Screening assessment - Epoxy resins group
Screening assessment - Epoxy resins group
Chemical Abstracts Service Registry Numbers:
25036-25-3, 25068-38-6, 25085-99-8, 28064-14-4
Environment and Climate Change Canada
Cat. No.: En14-375/2019E-PDF
Pursuant to section 74 of the Canadian Environmental Protection Act, 1999 (CEPA), the Minister of the Environment and the Minister of Health have conducted a screening assessment of four substances referred to under the Chemicals Management Plan as the Epoxy Resins Group. Substances in this group [namely three Diglycidyl Ethers of Bisphenol A (DGEBA) and one Novolac epoxy resin] were identified as priorities for assessment as they met categorization criteria under subsection 73(1) of CEPA. The Chemical Abstracts Service Registry Numbers (CAS RNFootnote 1), their Domestic Substances List (DSL) names and their acronyms are listed in the table below.
|CAS RN||Domestic Substances List name||Acronyms|
|25036-25-3||Phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bis[oxirane]||DGEBA epoxy resin|
|25068-38-6||Phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2-(chloromethyl)oxirane||DGEBA epoxy resin|
|25085-99-8||Oxirane, 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bis-, homopolymer||DGEBA epoxy resin|
|28064-14-4||Phenol, polymer with formaldehyde, glycidyl ether||Novolac epoxy resin|
These four substances were previously evaluated under the Second Phase of Polymer Rapid Screening, which identified CAS RN 25036-25-3 (one of the DGEBA epoxy resins) and CAS RN 28064-14-4 (Novolac epoxy resin) as having low potential to cause ecological harm, however further evaluation of human health risks was warranted. The three DGEBA epoxy resins and Novolac epoxy resin were identified as requiring further assessment for potential human health and/or ecological risks on the basis of structural alerts and/or uses associated with significant consumer exposure. The present assessment further elaborates on the potential for these substances to cause harm to human health and ecological harm, in order to reach an overall conclusion under section 64 of CEPA as to whether they pose a risk to the environment or human health.
The four epoxy resins do not occur naturally in the environment. In Canada, they are reported to be used as crosslinkers and binders in paints/coatings and plating agents; as intermediates; in adhesives and sealants in grout, flooring, plastics and concrete; in lubricants and lubricant additives; as corrosion inhibitors and anti-scaling agents, and as processing aids specific to petroleum production. In addition, epoxy resins have been identified as components used in the manufacture of some food packaging materials.
DGEBA epoxy resins contain epoxy reactive functional groups which in general may be associated with adverse effects to fish, invertebrates, and algae. However, the assessment revealed that DGEBA epoxy resins are expected to show moderate to low toxicity to aquatic organisms, and low toxicity towards sediment dwelling species in natural environments. Considering the use of the DGEBA epoxy resins, they may be released to the environment through formulation facilities and during end use applications; however, conservative estimates of exposure were calculated and found to be below the exposure expected to cause harm to sensitive organisms in the environment.
DGEBA and Novolac epoxy resins contain epoxy reactive functional groups which are associated with potential adverse human health effects. These substances show effects on the spleen in chronic studies at doses greater than 15 mg/kg bw/day (primarily associated with the lower molecular weight resins) and are dermal sensitizers; however, they have low acute toxicity and are not developmental or reproductive toxicants, nor are they teratogenic or carcinogenic in animal studies. Canadians may be exposed to DGEBA epoxy resins from potential transfer of an insignificant amount of the resin from food packaging materials into food including canned liquid infant formula products. Quantities are very low because these substances are used up in the chemical reaction when the packaging is made. Dietary exposure to Novolac epoxy resin from food packaging material is also expected to be negligible to both adults and children. Exposure to epoxy resins by inhalation is not expected due to their low vapour pressures. Dermal exposure to epoxy resins is considered minimal due to their usage in cured-form. Indirect exposure of the general public to epoxy resins through media such as drinking water is not expected due to their low water solubility.
A comparison of estimated levels of exposure to DGEBA epoxy resins and Novolac epoxy resins to the critical effect levels results in margins of exposure that are considered adequate to account for uncertainties in the health effects and exposure information.
Considering all available lines of evidence presented in this screening assessment, there is low risk of harm to organisms and the broader integrity of the environment from DGEBA epoxy resin and Novolac epoxy resin. It is concluded that DGEBA epoxy resins and Novolac epoxy resin do not meet the criteria under paragraphs 64(a) or (b) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitutes or may constitute a danger to the environment on which life depends.
On the basis of the information presented in this screening assessment, it is concluded that the three DGEBA epoxy resins and Novolac epoxy resin do not meet the criteria under paragraph 64(c) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.
Therefore, it is concluded that the four epoxy resins do not meet any of the criteria set out in section 64 of CEPA.
Pursuant to section 74 of the Canadian Environmental Protection Act, 1999 (CEPA) (Canada 1999), the Minister of Environment and Climate Change and the Minister of Health have conducted a screening assessment of four substances referred to collectively as the epoxy resins group to determine whether these substances present or may present a risk to the environment or to human health. The substances in this group were identified as priorities for assessment as they met categorization criteria under subsection 73(1) of CEPA (ECCC, HC 2017).
While the four substances considered in this assessment are collectively referred to as the epoxy resins group, three of them (DGEBA epoxy resins) have similarities that would support a group approach to exposure, hazard and risk characterization; thus, their exposure and hazard profiles were collectively assessed for risk. The assessment of Novolac epoxy resin forms its own chapter.
The substances considered in this assessment have been previously evaluated using a rapid screening approach. The approach and results of its application, are presented in the document “Second Phase of Polymer Rapid Screening: Results of the Screening Assessment” (ECCC, HC 2017). The ecological and human health rapid screening approaches are summarized in the Appendix of this screening assessment. Application of these approaches identified one of the DGEBA epoxy resins (CAS RN 25036-25-3) and Novolac epoxy resin as having low potential to cause ecological harm; however, further evaluation of human health risks was warranted. These results, in conjunction with any other relevant information that became available after the publication of the report on the second phase of polymer rapid screening, are considered in support of the conclusions made under section 64 of CEPA in this screening assessment.
This screening assessment includes consideration of additional information on chemical properties, environmental fate, hazards, uses and exposures, including additional information submitted by stakeholders. Relevant data were identified up to March 2017. Empirical data from key studies as well as results from models were used to reach conclusions. When available and relevant, information presented in assessments from other jurisdictions was considered.
This screening assessment was prepared by staff in the CEPA Risk Assessment Program at Health Canada and Environment and Climate Change Canada and incorporates input from other programs within these departments. The document “Second Phase of Polymer Rapid Screening: Results of the Screening Assessment” has undergone external review and was subject to a 60-day public comment period. While external comments were taken into consideration, the final content and outcome of this screening assessment remain the responsibility of Health Canada and Environment and Climate Change Canada.
This screening assessment focuses on information critical to determining whether substances meet the criteria as set out in section 64 of CEPA, by examining scientific information and incorporating a weight of evidence approach and precautionFootnote 2. The screening assessment presents the critical information and considerations upon which the conclusion is made.
2. Diglycidyl ether of bisphenol A epoxy resins
2.1 Identity of substance
The most commonly used intermediate in epoxy resin technology is Diglycidyl Ether of Bisphenol A (DGEBA or BADGE) (Pascault 2010). It is the reaction product of bisphenol A and epichlorohydrin (Figure 2‑1). DGEBA epoxy resins are prepared directly from bisphenol A and epichlorohydrin [route (a)], by homopolymerization of DGEBA [route (b)], or by reaction of DGEBA with bisphenol A [route (c)]. These epoxy resins are usually mixtures, which could be isomers, branched-chain oligomers, and monoglycidyl ethers (Bingham 2012). However, no residual monomers (i.e. bisphenol A and epichlorohydrin) are expected to remain as these processes involve several purification stages to remove all impurities.
The average degree of polymerization, n, varies from 0.1 up to 25. When n is very low (< 0.2), DGEBA epoxy resin is a low molecular weight (MW) liquid substance (comprising mostly DGEBA itself) usually with the CAS RN 25068-38-6. A majority of this low MW substance is used as starting material to produce high MW solid epoxy resins (n = 0.2 to 25) (Kirk-Othmer 2014). The CAS RNs 25085-99-8 (when n ≈ 0.2) and 25036-25-3 (when n > 0.2) are predominately used for higher MW solid DGEBA epoxy resins. These higher MW epoxy resins contain no or a limited amount of DGEBA in their formulations.
The performance characteristics of the DGEBA epoxy resins are due to the presence of the bisphenol A moiety (rigidity, toughness, and elevated temperature performance), the ether linkages (chemical resistance), and the hydroxyl and epoxy groups (reactivity with a variety of curing agents). Theoretically, two terminal epoxy groups are present in DGEBA epoxy resins. Epoxides are a reactive functional group associated with adverse human health effects (US EPA 2010). In polymeric structures such as the one below, flexibility and strength increase as the repeating unit (represented by the coefficient n) increases. Furthermore, the DGEBA epoxy resins can also be cured through the multiple hydroxyl groups along the backbones using cross-linkers (Jin 2015, Ullman’s 2012).
Figure 2‑1. Synthesis and representative structure of DGEBA epoxy resins
The figure shows structures for the reactants and the final DGEBA epoxy resins. DGEBA epoxy resins can be prepared directly from bisphenol A (C(c1ccc(O)cc1)(c1ccc(O)cc1)(C)C) and epichlorohydrin (C1[C@@H](O1)CCl) [route (a)], by homopolymerization of DGEBA (CC(C)(C1=CC=C(C=C1)OCC2CO2)C3=CC=C(C=C3)OCC4CO4) [route (b)], or by reaction of DGEBA (CC(C)(C1=CC=C(C=C1)OCC2CO2)C3=CC=C(C=C3)OCC4CO4) with bisphenol A ((C(c1ccc(O)cc1)(c1ccc(O)cc1)(C)C) ) [route (c)].
2.2 Physical and chemical properties
A summary of physical and chemical properties for DGEBA epoxy resins are presented in Table 2‑1.
|Corresponding CAS RN||25068-38-6||25085-99-8||25036-25-3||NS|
|Degree of polymerization||n ≤ 0.1||n ≈ 0.2||n = 2||n = 9|
|Physical form||liquid||liquid (viscous)||solid||solid|
|Number average molecular weight (g/mol)||350-370||380||900||2900|
|Melting point (°C)||-16-5||44-55||64-95||127-133|
|Boiling point (°C)||> 260||320 (decom.)||114-118||NA|
|Water solubility (mg/L)||3.6-6.9 @ 20°C||5.4-8.4 @ 20°C||3.7 @ 25°C||NA|
|Vapour pressure (Pa)||4.6 × 10-8 @ 25°C||< 10-7||1.4 × 10-5 @ 25°C||NA|
|Octanol/water partition co-efficient (log Kow)||2.8-3.25 @ 25°C, pH 7||3.24 (est.)||3.84||NA|
|Epoxy equivalent weighta (g/eq.)||172-185||182-195||450-525||1650-2050|
|Epoxide contenta (%)||~ 24||~ 23||~ 9||~ 2|
|Biodegradation (%)||NA||12% @ 28 d||NA||NA|
|References||Kirk-Othmer 2014 Ullman’s 2012 ECHA c2007-2017b Canada 2015 ECCC 2015||Kirk-Othmer 2014 Ulmann’s 2012 DME 2012 Canada 2015 ECCC 2015||SciFinder Boyle 2001 Bingham 2012||Bingham 2012|
NS: Not specifically identified; see Section 188.8.131.52 (Uncertainties in evaluation of risk to human health) for more information
NA: Not Available
a Epoxy equivalent weight (EEW) is the weight of resin required to obtain one equivalent of epoxy functional group. It is related to the epoxide content (%) of the epoxy resin through the following relationship: EEW = (43.05 ÷ % Epoxide) ×100
Figure 2‑2. Representative structure of the hydrolysis product used for modelling
Epoxide groups are known to be susceptible to hydrolysis to form diols (Rickborn and Lamke 1967). Therefore, the terminal epoxide rings present in DGEBA epoxy resins are expected to readily hydrolyze under environmental conditions to form terminal diols. As a result, the environmental fate and ecotoxicity of the hydrolysis product in Figure 2‑2 will be considered as part of the current assessment. Supplementary physical and chemical data modelled using this hydrolysis product is summarized in Table 2‑2.
|Water Solubility||96.18 mg/L||EPI v4.11 WSKOW v1.42|
|Octanol/water partition co-efficient (log Kow)||1.93||EPI v4.11 KOWWIN v1.68|
|Adsorption Desorption||Log Koc = 1.28 (Log Kow)||EPI v4.11 KOCWIN v2.00|
|Henry’s Law Constant||1.67×10-9 Pa-m3/mole||EPI v4.11 HENRYWIN v3.20 (Bond Estimate)|
|WWTS Removala||Total removal = 2.19% Total biodegradation = 0.09%||EPI v4.11 STP Fugacity (10000 hr Bio P,A,S)|
a wastewater treatment system (WWTS) removal
2.3 Sources and uses
DGEBA epoxy resins are prepared industrially. Uncured epoxy resins are frequently encountered in industrial settings (Ellis 1993). They are marketed in different physical forms and require an admixture with curing agents to form nonreactive cross-linked polymers (Boyle 2001).
DGEBA epoxy resins were included in a voluntary survey (ECCC 2015) as well as a mandatory survey conducted under section 71 of CEPA (Canada 2015). Table 2‑3 presents a summary of the total manufacture and total import reported for the substance in 2014. These sources indicate that the functional uses for DGEBA epoxy resins in Canada included use as binders, coating agents, plating agents, adhesives, sealants, intermediates, lubricant additives, corrosion inhibitors, anti-scaling agents, and processing aids. Moreover, DGEBA epoxy resins in Canada have commercial and consumer uses, including toner and colorants, fence post backfill, epoxy primer, garage floor coating, and pesticides.
DGEBA epoxy resins are the most widely used epoxy resins (> 75% of resin sales volume) (Kirk-Othmer 2014). Globally, the largest use of epoxy resins is in protective coatings (> 50%), with the remainder being in structural applications such as printed circuit board laminates, semiconductor encapsulants, structural composites; tooling, molding, casting; flooring; adhesives (Petrie 2006); lithographic inks and photoresists for the electronics industry (Ullmann’s 2012).
|Substance||Total manufacturea (million kg)||Total importsa (million kg)||Survey reference|
|25036-25-3||0||1-10||Canada 2015, ECCC 2015|
|25068-38-6||0.1-1||1-10||Canada 2015, ECCC 2015|
|25085-99-8||<0.1||0.1-1||Canada 2015, ECCC 2015|
A number of domestic government databases were searched to determine if DGEBA epoxy resins are approved, licensed, and/or registered for uses in Canada. These uses for DGEBA epoxy resins are listed in Table 2‑4.
|Food packaging materialsa||Yes||Yes||Yes|
|Notified to be present in cosmetics, based upon notifications submitted under the Cosmetic Regulations to Health Canadab||Yes||No||No|
|Formulant in pest control products registered in Canadac||Yes (list 3)||No||No|
|Known Toy Used||No||Yes (adhesive)||Yes (Paint)|
a Food Directorate, Health Canada, to the Risk Management Bureau, Health Canada; unreferenced
b Consumer Product Safety Directorate, Health Canada, to the Risk Management Bureau, Health Canada; unreferenced
c PMRA (2010)
d Toy Industry Spreadsheet (2016)
2.4 Releases to the environment
According to available information, large quantities of each of the three DGEBA epoxy resins were manufactured and/or imported into Canada in 2014 (see Table 2-3) to be used mainly as components in two types of products: (1) adhesives and sealants, and (2) paints and coatings, according to the data collected under a regulatory survey (Canada 2015). The main functional uses for DGEBA epoxy resins in Canada are as binders, coating agents, adhesives, and intermediates to form epoxy coatings in industrial facilities.
Release to the environment of DGEBA epoxy resins is possible from the epoxy coating industries during use as an intermediate in further manufacturing of another substance, in the production of articles, formulation of mixtures and in processing aids at industrial sites.
Epoxy coatings are generally packaged in two parts that are mixed prior to application. The two parts consist of 1) an epoxy resin which is cross-linked with 2) a co-reactant or hardener. Epoxy coatings are formulated based upon the performance requirements for the end product. When properly catalyzed and applied, epoxies produce a hard, chemical and solvent resistant finish. The substance is consumed in the reaction with the curing agent to form an epoxy coating.
2.5 Environmental fate and behaviour
2.5.1 Environmental distribution
The three DGEBA epoxy resins have molecular weights between 350 and 900 daltons, and have water solubility less than 10 mg/L (see Table 2‑1). During industrial use, DGEBA epoxy resins are expected to be mostly consumed in the reaction with the curing agent to form an epoxy coating as mentioned above. Small quantities of DGEBA epoxy resins may still be released into the environment during the various steps involved during application of the resins. Once in the environment, the three DGEBA epoxy resins are expected to hydrolyze and the hydrolysis products are not expected to volatilize into the air compartment as they have low expected Henry’s Law constant (based upon estimation, see Table 2‑2). The hydrolysis products are anticipated to adsorb onto dissolved organic matter and settle into sediments. Any residual polymer is expected to remain in the water column.
2.5.2 Environmental persistence
Biodegradation data provided through voluntary (ECCC 2015) and mandatory surveys (Canada 2015) are summarized in Table 2‑5.
|CAS RN||Result (% degradation)||Test Method||Sources|
|25036-25-3||12||OECD 302||ECCC, HC 2007|
|25068-38-6||11||OECD 306||Canada 2015|
|25068-38-6||5||OECD 301F||SDS 2014|
|25068-38-6||0||OECD 301||SDS 2015a|
|25085-99-8||12||OECD 302||SDS 2011a|
Biodegradation in sea water for CAS RN 25068-38-6 has been reported to be 11% in 28 days (Canada 2015). The low biodegradation value is supported by submitted Safety Data Sheet (SDS) data describing 0 and 5% degradation.
The inherent biodegradation value for CAS RN 25085-99-8 has been reported to be 12% in 28 days according to SDS. It also specifies results are from test protocol OECD 302 but the full report was not provided.
The overall trend shows that the three DGEBA epoxy resins are not biodegradable.
Although there is no available information to assess the biodegradation potential of the three DGEBA epoxy resin in sediments, it is generally expected to be slower than in soil or water, where aerobic conditions favour biodegradation. As such, it is anticipated that the three DGEBA epoxy resins will have lower biodegradation in sediments.
Hydrolysis information for the three DGEBA epoxy resins was not provided. On the basis of their chemical structure, DGEBA epoxy resins are expected to be readily susceptible to hydrolysis where the terminal epoxide rings open and form terminal diols. The hydrolysis products are expected to be stable (May 1987).
On the basis of experimental biodegradation data, the three DGEBA epoxy resins are not expected to be degraded rapidly in the aquatic environment. However, they are expected to be hydrolytically unstable under environmental conditions.
Although experimental data on the biodegradation of the three DGEBA epoxy resins are available, a QSAR-based weight-of-evidence approach was also applied using the degradation models shown in Table 2‑6.
The predicted degradation parameters in Table 2‑6 were based upon the representative structure in Figure 2‑2 representing the hydrolysis product, as the three DGEBA epoxy resins are expected to readily hydrolyze in the environment.
|Fate process||Model and model basis||Model prediction||Extrapolated half-life (days)|
|Water: Hydrolysis||EPI v4.11 HYDROWIN v2.00||NAb||NA|
|Ready Biodegradability Prediction||EPI v4.11 BIOWIN v4.10||No||≥182|
|Ultimate aerobic biodegradation: Probability||DS TOPKAT c2005-2009||c “biodegrades very slowly”||≥182|
|Ultimate aerobic biodegradation: % BOD (biological oxygen demand)||Catalogic 301C v.9.13||% BOD = 0 “biodegrades very slowly”||≥182|
a The predicted degradation parameters were based upon the representative structure of 376.19 Da with the following SMILES: CC(C1=CC=C(OCC(O)CO)C=C1)(C)C2=CC=C(OCC(O)CO)C=C2
b Model does not provide an estimate for this type of structure
c Output is a probability score
NA – Not available
Modelled results presented in Table 2‑6 provide additional and relatively consistent evidence for the degradation potential of the three DGEBA epoxy resins.
On the basis of empirical and modelled data, the three DGEBA epoxy resins are expected to undergo environmental hydrolysis to form diols which are not readily biodegradable in the water, soil and sediment compartments.
2.5.3 Bioaccumulation potential
Empirical Octanol/Water Partition Coefficient (log Kow) and Bioconcentration Factor (BCF) data provided through voluntary (ECCC 2015) and mandatory surveys (Canada 2015) are summarized in Table 2‑7.
|CAS RNs||Property||Value||Test method||Sources|
|25068-38-6||Octanol/Water Partition Coefficient (log Kow)||Log Kow > 3||NA||SDS 2015a|
|25068-38-6||Octanol/Water Partition Coefficient (log Kow)||Log Kow=3.2||NA||SDS 2014|
|25068-38-6||Octanol/Water Partition Coefficient (log Kow)||Log Kow=3.6||OECD 117||Canada 2015|
|25068-38-6||Bioconcentration Factor (BCF)||BCF = 0.56~ 0.67||NA||SDS 2015a|
|25068-38-6||Bioconcentration Factor (BCF)||BCF = 31||NA||SDS 2014|
|25085-99-8||Bioconcentration Factor (BCF)||BCF = 100-3000||NA||SDS 2011a|
The empirical Octanol/Water Partition Coefficient (log Kow) and BCFs summarized in Table 2‑7 support low to moderate bioaccumulation potential of the three DGEBA epoxy resins for aquatic organisms.
Although experimental data on the bioaccumulation of the three DGEBA epoxy resins are available, a QSAR-based weight-of-evidence approach was also applied to a hydrolysis product and results are summarized in Table 2‑8.
|Octanol-Water Partition Coefficient||Log Kow 2.69 at 25°C||EPI v4.11 KOWWIN v1.68|
|BCF/BAF||27.88 L/kg wet-wt (mid trophic)||EPI v4.11 BCFBAF v3.01|
a The predicted degradation parameters were based upon the representative structure of 376.19 Da with the following SMILES: CC(C1=CC=C(OCC(O)CO)C=C1)(C)C2=CC=C(OCC(O)CO)C=C2
Modelled results of a hydrolysis product presented in Table 2‑8 provide additional and relatively consistent evidence for the bioaccumulation potential of the three DGEBA epoxy resins.
From Table 2-7 and Table 2-8, it can be seen that the bioaccumulation potential for DGEBA epoxy resins are generally low to moderate. The empirical BCF value for CAS RN 25085-99-8 suggests that the substance could have moderate bioaccumulation potential. This differs from the predicted BCF/BAF values reported in Table 2-8, where the predicted values suggest that the hydrolysis products of DGEBA (see Figure 2-2) have very low bioaccumulation potential. The difference could be owing to the fact that the predicted BCF/BAF are based on metabolism rate for mid trophic fish. Furthermore, the model is also predicting that the fragment could be metabolized by the organism, both of which could differ significantly between living organism and modelled organism. Considering the Log Kow (empirical and predicted) and BCF (values) available, the overall bioaccumulation potential of DGEBA epoxy resin is anticipated to range from low to moderate.
2.6 Potential to cause ecological harm
2.6.1 Results of the second phase of Polymer Rapid Screening for CAS RN 25036-25-3
The three DGEBA epoxy resins were previously screened through the Second Phase of Polymer Rapid Screening: Results of the Screening Assessment (2018). Through this rapid screening process, phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bis[oxirane]) (CAS RN 25036-25-3) was identified as having low water extractability and therefore not available to aquatic organisms. This substance was characterized as having a low potential for ecological risk. It is unlikely that this substance will result in concerns for organisms or the broader integrity of the environment in Canada.
Critical data and considerations used during the second phase of polymer rapid screening to evaluate the three DGEBA epoxy resins with respect to their potential to cause ecological harm are presented in ECCC (2016).
The two remaining DGEBA epoxy resins, phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2-(chloromethyl)oxirane (CAS RN 25068-38-6) and oxirane, 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bis-, homopolymer (CAS RN25085-99-8), were found to have high environmental exposure potential, and were characterized as having moderate to high potential for ecological risk. As such, CAS RN 25068-38-6 and CAS RN 25085-99-8 were identified for further ecological assessment. In the remainder of Section 2.6, discussion on DGEBA epoxy resins will be specifically referring to CAS RN 25068-38-6 and CAS RN 25085-99-8.
2.6.2 Ecological effects assessment
According to the US EPA (2010), substances containing epoxide functional groups may be associated with adverse effects to fish, invertebrates, and algae.
The aquatic toxicity for epoxides and poly(epoxides) has been determined through Structure Active Relationship (SAR) analysis by US EPA using ECOSAR, a hazard estimation tool that uses chemical structure descriptors to estimate the acute and chronic toxicity of a substance to aquatic organisms. This analysis indicated that structures with epoxy equivalent weights (EEWepoxy) of greater than 1 000 Da are not expected to pose a hazard under any conditions. Concerns are confined to those species with Number Average Molecular Weight (Mn) less than 1 000 Da.
As indicated in Table 2‑1, the two DGEBA epoxy resins have Mn and EEWepoxy less than 1 000 Da and may, therefore, be hazardous to aquatic biota.
Empirical ecotoxicity data for the two DGEBA epoxy resins were reported in response to government surveys mentioned previously (ECCC 2015, Canada 2015). The results of ecological studies are summarized in Table 2‑9. The data were extracted from SDS and summary information provided by stakeholders, and suggest that DGEBA epoxy resins could have moderate toxicity towards algae, daphnids and fish.
|CAS RNs||Organism||Result (mg/L)a||Test method||Sources|
|25068-38-6||Algae (P. subcapitata)||48h EC50=9.4||NA||SDS 2015d|
|25068-38-6||Algae (P. subcapitata)||72h EC50=9.4||NA||SDS 2014|
|25068-38-6||Daphnid (D. magna)||48h EC50=1.4-1.7||NA||SDS 2013|
|25068-38-6||Daphnid (D. magna)||24h EC50=3.6||NA||SDS 2012b|
|25068-38-6||Daphnid (D. magna)||24h EC50=2.6||NA||SDS 2012c|
|25068-38-6||Fish (S. gairdneri)||96h LC50=3.6||NA||SDS 2015c|
|25068-38-6||Fish (P. promelas)||96h LC50=3.1||NA||SDS 2013|
|25068-38-6||Fish (O. latipes)||96h LC50=1.41||NA||SDS 2015a|
|25068-38-6||Fish||96h LC50=1.3||OECD 203||SDS 2012a|
|25085-99-8||Algae (S. capricornutum)||72h ErC50=11||NA||SDS 2011a|
|25085-99-8||Fish (O. mykiss)||96h LC50=2||NA||SDS 2011a|
|25085-99-8||Fish (P. promelas)||96h LC50=3.1||NA||SDS 2010|
a EC50 is the Effect Concentration for 50 percent of the population; LC50 is the Lethal Concentration for 50 percent of the population; NOEC is the No Observed Effect Concentration.
NA: Not Available
The European Chemical Agency (ECHA) database contains several ecotoxicity data for CAS RN 25068-38-6. The results of these ecological studies are summarized in Table 2‑10.
|Organism||Result (mg/L)a||Test method||Sources|
|Daphnid (D. magna)||48h EC50 = 1.1b-2.8||NA||ECHA c2007-2017a|
|Algae (S. capricornutum)||72h EbC50 = 9.1-9.4 c||NA||ECHA c2007-2017a|
|Algae (S. capricornutum)||72h NOEC = 2.4 c||NA||ECHA c2007-2017a|
a EC50 is the Effect Concentration for 50 percent of the population; NOEC is the No Observed Effect Concentration.
b This endpoint was chosen as the critical toxicity value (CTV)
c Based upon biomass
NA: Not Available
As presented above, the ECHA database contains acute toxicity information for Daphnia magna. According to summary information, the study reported hazard endpoints for different test solution preparations. The acute study reported 48-hour EC50 values ranging from 1.1 to 2.8 mg/L.
The ECHA database also contains an aquatic toxicity study for algae. The study was found to be of good quality and reliable. The study tested CAS RN 25068-38-6 with Scenedesmus capricornutum and reported the NOEC and EbC50 as 2.4 and 9.1-9.4 mg/L, respectively. The 72-hour ErC50 value (based upon growth rate) could not be exactly determined since no significant effects were noted at the limit of solubility for the test material.
The ecotoxicity data identified through the ECHA database suggest that CAS RN 25068-38-6 could have moderate toxicity towards algae, and daphnia.
Two ecotoxicological analogues of DGEBA epoxy resin were identified through New Substances Notification Program (ECCC 2017). However, the ecotoxicological data of these two analogues are not described in this report because they are considered to be confidential business information. These two analogue polymers with high degrees of structural similarity exhibited moderate toxicity towards algae, daphnia and fish.
The ECHA database contains three ecotoxicity endpoints for oxirane, 2,2'-[1,4-butanediylbis (oxymethylene)]bis- (CAS# 2425-79-8) which can be considered an ecotoxicological analogue of DGEBA epoxy resins (ECHA c2007-2017b). The results of ecological studies of this analogue are summarized in Table 2‑11.
|CAS RNs||Organism||Result (mg/L)||Test method|
|2425-79-8||Fish (B. rerio)||24h-LC50=19.8||OECD 203|
|2425-79-8||Daphnid (D. magna)||48h- EC50=75||OECD 202|
|2425-79-8||Algae (S. subspicatus)||72h-ECr50>100a 72h-ECb50=160b||OECD 201 OECD 201|
a 72h-ECr50 based upon growth rate of water accommodated fraction (WAF)
b 72h-ECb50 based upon biomass of water accommodated fraction (WAF)
Zebra fish (Brachydanio rerio), daphnid (Daphnia magna), and green algae (Scenedesmus subspicatus) were exposed to the analogue substance (CAS# 2425-79-8) under static conditions following OECD Guidelines 203, 202, and 201, respectively. The results reported are based on nominal concentrations or loading rates of water accommodated fractions. The data for these ecotoxicological analogues suggest that DGEBA epoxy resins could have low to moderate toxicity towards algae, daphnia and fish.
Ecotoxicity was also predicted based upon the representative structure of the hydrolysis product depicted in Figure 2‑2. ECOSAR predictions were generated for neutral organics classes. However, no effects at saturation were reported for all organisms.
No sediment ecotoxicity data were provided for the two DGEBA epoxy resins, or were available for other DGEBA epoxy resins.
Overall, on the basis of empirical, analogue and model data, the two DGEBA epoxy resins are expected to show moderate to low toxicity to aquatic organisms, and low toxicity to sediment dwelling species in natural environments. On the basis of available data, the lowest ecotoxicity end point, daphnid 48h EC50=1.1 mg/L was selected to be the Critical Toxicity Value (CTV), and is used to estimate the aquatic Predicted No Effect Concentration (PNEC). A PNEC is not considered necessary for sediment species, as the toxicity value is anticipated to be greater than 100 mg/L.
The aquatic PNEC is derived from the Critical Toxicity Value (CTV), which is divided by an assessment factor (AF) as shown:
Aquatic PNEC (mg/L) = CTV / AF
Aquatic PNEC (mg/L) = (1.1 mg/L) / 10
Aquatic PNEC (mg/L) = 0.11
The AF selected represents a factor of 10 to extrapolate from acute to chronic toxicity and a factor or 1 to account for species sensitivity (> 7 species, covering 3 categories, for the two DGEBA epoxy resins).
2.6.3 Ecological exposure assessment
According to the data collected through the voluntary (ECCC 2015) and mandatory surveys (Canada 2015), DGEBA epoxy resins are used as components in (1) adhesives and sealants, and (2) paints and coatings. Based upon available information, the majority of DGEBA epoxy resins were imported in to Canada. Therefore, the exposure scenario for the manufacturing of DGEBA epoxy resins is not considered further as its release is expected to be lower than other scenarios described below.
According to the survey data, there are three major industrial scenarios:
- Formulation of DGEBA epoxy resins into adhesives and sealants
- Formulation of DGEBA epoxy resins into paints and coatings
- Application of the formulated products in the production of toys, automobiles, etc.
In estimating the aquatic exposure under each scenario, a fraction of a substance is assumed to end up in wastewater. This assumption is conservative for cases where no water is used in the formulation or application, or equipment cleaning. On the basis of this assumption, a small amount of each substance enters the wastewater generated from an industrial facility. The industrial wastewater is then discharged to a wastewater collection system. The substance is subsequently released to the aquatic environment via the effluent after wastewater treatment. The predicted environmental concentration (PEC) of each CAS RN in receiving water depends upon its use quantity at a given facility as well as the conditions associated with its off-site wastewater treatment and the receiving water. The aquatic PEC resulting from a facility is estimated by
PEC = [109 × Q × E × (1-R)]/ [F×D×N]
PEC: predicted environmental concentration in receiving water near discharge point, mg/L
Q: a substance’s annual use quantity at a facility, kg/year
E: emission factor to wastewater, unitless
R: wastewater treatment removal, unitless
F: daily wastewater flow rate, L/d
D: receiving water dilution factor near discharge point, unitless
N: number of annual operation days, d/y
109: conversion factor from kg to mg, mg/kg
In the formulation of adhesives and sealants, organic solvent is used on the basis of information provided by a formulator (response to 2015 CEPA Section 71 CMP3 polymers survey, and 2017 follow-up questions). According to a number of site visits to formulation facilities conducted by Environment and Climate Change Canada in 2013, no water was used and no material was released to wastewater during solvent-based formulation equipment cleaning. Releases of DGEBA epoxy resins to off-site wastewater treatment systems and aquatic environment are therefore not expected from the formulation of adhesives and sealants.
In the formulation of paints and coatings, no information is available about the type of carriers used. As a conservative estimate, water is assumed to be used in the formulation and to be released to wastewater treatment systems. In addition, a set of conservative conditions are selected in the PEC determination. These conservative conditions include the upper limit for annual use quantity found at a formulation facility (Q = 1 000 000 kg/y), the lower limit for daily wastewater flow rate associated with a formulation facility (F = 27 000 000 L/d) and nil for wastewater treatment removal (R = 0). The number of annual operation days and the emission factor or the fraction lost to wastewater are 300 days per year (N) and 0.3% (E), respectively according to a technical guidance document on risk assessment from the European Chemicals Bureau (2003). The receiving waterbodies of the wastewater treatment systems associated with the formulation facilities are generally large and 10-fold dilution is used for dilution near the discharge point (D = 10). On the basis of the above conservative conditions and assumptions, the PEC is determined as
Aquatic PEC for formulation of paints and coatings = 37 mg/L
The aquatic PEC for the application scenario is also determined conservatively on the basis of the largest industrial user in Canada in terms of annual use quantity. The upper limit for this annual use quantity is 10 million kg/y (Q) and the off-site wastewater treatment facility has a daily flow rate of 456 million L/d (F). The values of the other parameters used in the PEC calculation are selected to be the same as those for the formulation of paints and coatings. The PEC is determined as
Aquatic PEC for application scenario = 22 mg/L
2.6.4 Characterization of ecological risk
The approach taken in this ecological risk assessment was to examine direct and supporting information and develop conclusions based upon a weight-of-evidence approach. Lines of evidence considered include information on sources and fate of the substance, persistence, bioaccumulation, and ecological hazard properties. The two DGEBA epoxy resins are used as components in adhesives and sealants, and paints and coatings. On the basis of available information, the quantity of each substance imported into Canada in 2014 from the survey data was up to 10 million kg.
Water solubility information reported for the two DGEBA epoxy resins, indicates they are slightly water soluble. When the two DGEBA epoxy resins are released into the environment, they are expected to hydrolyze. Given the low vapour pressure, partitioning into the air compartment is not expected. Furthermore, significant amounts are anticipated to adsorb onto dissolve organic matter and settle to sediments. Any residual polymer is expected to remain in the water column.
With respect to long term persistence of these polymers, available biodegradation data for DGEBA epoxy resins suggest that they will not be biodegradable in the environment. Other information on transformative properties suggests these polymers are hydrolyzable.
All empirical and modelled data used to assess the bioaccumulation potential support the low to moderate bioaccumulation potential of the two DGEBA epoxy resin for aquatic organisms.
Reported information on the current use pattern of the two DGEBA epoxy resins indicates that they are used as components in two types of products: (1) adhesives and sealants, and (2) paints and coatings. The majority of DGEBA epoxy resins was imported and only minor quantities are manufactured in Canada. A conservative exposure estimation for the formulation and application of the two DGEBA epoxy resins generated the PEC is shown in Table 2‑12.
According to the ecological hazard profile of the two DGEBA epoxy resins, they generally have low to moderate toxicity towards fish, daphnia, and algae. For the purpose of this assessment, the highest toxicity value was selected as the CTV and used to estimate the PNEC.
The risk quotient was estimated based upon the PNEC and conservative PEC.
Table 2‑12 summarizes the risk quotients calculated.
|Scenarios||PNEC (mg/L)||PEC (mg/L)||Risk quotient (PEC/PNEC)|
|Aquatic PEC for formulation of adhesives and sealants||0.11||0||0|
|Aquatic PEC for formulation of paints and coatings||0.11||0.037||0.34|
|Aquatic PEC for application of the formulated products||0.11||0.022||0.2|
Based upon Table 2‑12, neither the formulation scenario nor the application scenario for the two DGEBA epoxy resin are expected to result in environmental concern (i.e., risk quotients are less than 1). Considering that conservative values, such as the high emission factor, volumes, number of sites and flow rates, were used to estimate the PEC, it is anticipated that the risk quotients are an over estimation of the potential risk. Overall, the two DGEBA epoxy resins are not expected to result in ecological concern on the basis of available information and conservative estimation of PEC values for the main exposure scenarios.
184.108.40.206 Uncertainties in evaluation of risk to environment
There are various uncertainties related to the ecological assessment of DGEBA. It is recognized that a given CAS RN can describe polymers that have different Mn, and composition; and hence, a different range of physical-chemical properties and hazard properties. Furthermore, there are uncertainties in the exposure scenarios for DGEBA, such as the maximum quantity that a formulation could utilize in a year, the flow rates of the dilution river and the emission factor. However, considering that conservative assumptions were used to determine the exposure potential for DGEBA, changes in molecular weight, quantities, or other factors are not expected to result in a significant increase in ecological risk.
2.7 Potential to cause harm to human health
2.7.1 Exposure assessment
220.127.116.11 Direct exposure
As indicated above (Section 2-1), low molecular weight DGEBA epoxy resins (n ≤ 0.5) contain a substantial amount of DGEBA. Conversely, higher molecular weight DGEBA epoxy resins contain a limited amount of DGEBA but are primarily oligomeric forms of DGEBA. Therefore, the studies performed on DGEBA may apply to DGEBA epoxy resins in some cases.
When used industrially, direct exposure of the general population to DGEBA epoxy resins is not expected. Furthermore the release of DGEBA from end-use applications is very limited as epoxy resins are reacted with hardeners/curing agents into cross-linked systems that are stable against thermal and hydrolytic breakdown (DME 2012; SPII 1997, Bingham 2012).
The primary exposure to DGEBA is from food and drink cans lined with epoxy-based coatings. Residues of non-crosslinked DGEBA in epoxy resin can coating could migrate into foods due to incomplete polymerization, especially at elevated temperatures (e.g., for hot fill or heated processed canned foods) (Cao et al 2009, Lipke 2016). A number of surveys of DGEBA and their derivatives have been conducted in various countries in Europe to investigate the potential migration of DGEBA used in the interior coating for food and beverage cans. One study showed the amount of DGEBA derivatives contained in canned food was 100-600 µg/kg food (DME 2012). In 2001, the United Kingdom Food Standards Agency (FSA) conducted a market survey of DGEBA in canned food (Dionisi and Oldring 2002). Migration levels of DGEBA detected in the canned foodstuff were around 100 µg/kg food. The FSA calculated exposure to DGEBA as 0.05-0.13 μg/kg bw/day for a 60 kg individual considering the available information on European consumption pattern for canned food, total surface areas of cans, and the FSA survey data. The major sources of exposure appear to arise mostly from canned vegetables (48%), canned fish (18%) and pre-prepared meals (5%) (DME 2012). Another study used a Monte Carlo simulation which is a computational method on the basis of the measured average content of DGEBA in various canned foods. The estimated average DGEBA exposure was found to be 0.004 μg/kg bw/day with a maximum of 0.19 μg/kg bw/day for a 60 kg individual (European Commission 2002).
In 2004, market surveillance in the Netherlands was repeated on the potential migration of DGEBA derivatives from can coatings into fish. The method was suitable to determine the presence of these substances in fish-in oil and fish-in aqueous sauces. A total of 64 cans of fish were sampled and analysed. Epoxy derivatives were only detected in 9 cans or 14% of the total cans sample. Of those, 6 cans or 9% of the total number of canned fish sampled were found to contain DGEBA derivatives at average concentrations of 100 µg/kg food. This market surveillance was also performed previously in 2001 and 2002; a visible trend showed that all cans complied with the specific migration limit (SML) of 1 mg/kg in food or food simulants established by the European Commission for the sum of DGEBA, DGEBA.H2O and DGEBA.2H2O (DME 2012, European Commission 2005, Simal-Gandara 1998).
Several seafood products such as sardines, tuna fish, mackerel, mussels, cod, and mackerel eggs were manufactured in different conditions changing covering sauce, time and temperature of storage and heat-treatment for sterilization in cans. Migration kinetics of DGEBA from varnish into canned products was evaluated in 70 samples after 6, 12 or 18 months of storage. All samples analyzed presented values lower than 1 mg DGEBA/kg net product without exceeding European limits (i.e. 1 mg/kg). The highest rate of migration took place in mackerel reaching a value of 340 µg DGEBA/kg net product, in a red pepper sauce (Cabado 2008).
Health Canada’s Food Directorate also measured the levels of some epoxy resins, including DGEBA, in canned liquid infant formula products sampled in Canada in 2007. In that study, DGEBA was detected in samples of all 21 products from 2.4 – 262 ng/g. The probable daily intakes of DGEBA owing to consumption of canned liquid infant formula were estimated for infants from premature to 12–18 months of age. The maximum Probable Daily Intake (PDI) was 22 µg/kg bw/d for the 12–18 months old with the maximum formula intake. The probable daily intake of DGEBA for infants less than 12 months ranged from 1.2 to 5.6 µg/kg bw/d (Cao et al. 2009).
Using a worst-case scenario that assumes that DGEBA migrates at the same level as in canned foods into all types of food, the estimated per capita daily intake for a 60-kg individual is approximately 0.098 - 0.16 µg/kg bw/day, which is considered low for adults (Poole et al. 2004, Dionisi and Oldering 2002).
For children, the intake of DGEBA epoxy resins through exposure to toys is considered to be minimal as it will be contained within a hardened polymer matrix from which it is not likely to be released.
Exposure through dust
DGEBA epoxy resins have low vapour pressure, thus inhalation exposure is not expected. In one study, 158 indoor dust samples were collected from the U.S., China, Korea, and Japan and the concentrations of DGEBA and its three hydrolysis products (DGEBA·H2O, DGEBA·2H2O, and DGEBA·HCl-H2O) were determined. Among the four countries, all DGEBA target compounds were found in dust samples and the geometric mean concentrations ranged from 1.3 to 2.9 µg/g. The estimated intake for DGEBAs through dust ingestion was 6.5 ng/kg bw/day (Wang 2012).
Notifications for DGEBA epoxy resins (CAS RN 25068-38-6) submitted under the Cosmetic Regulations to Health Canada indicate that 8 cosmetics contain this substance at levels up to 10%. The products are listed as non-permanent make-ups and adhesives (nails, eye, face, body). Although DGEBA epoxy resins have been used in cosmetics which would be a source of exposure, because of their usage in the cured-form, dermal absorption is not expected (Ellis 1993).
Liquid epoxy resins are used in two-component epoxy glues sold to the general public in retail shops. These two components of epoxy glues would be mixed immediately before use. The mixed glue would contain the cured and solidified form of epoxy resins; therefore, dermal exposure to DGEBA epoxy resins is expected to be negligible (Petrie 2006).
DGEBA epoxy resins are not listed in the Natural Health Products Ingredients Database (NHPID [modified 2017]). They are not found in any drug products, including natural health products (LNHPD [modified 2016, DPD [modified 2015]).
In summary, on the basis of the sources of exposure described above, oral exposure to DGEBA epoxy resins is estimated to range from 1.2-22 µg/kg bw/d for Canadian infants from premature to 12–18 months of age (Cao et al 2009) and 0.05-0.19 µg/kg bw/d for European adults. The estimated intake for DGEBAs through dust ingestion was found to be 6.5 ng/kg bw/day. Exposure to DGEBA epoxy resins by inhalation is not expected due to their low vapour pressures. Dermal exposure to DGEBA epoxy resins is not expected due to their usage in cured-form.
18.104.22.168 Indirect exposure
When released to water, DGEBA epoxy resin (25036-25-3) is assumed to adsorb to particulate matter and sediment. Leaching to the groundwater compartment is not expected. Products containing DGEBA epoxy resins may be disposed of in landfills. DGEBA was identified as leachate from a DGEBA-based epoxy coating used to coat lead and copper pipe specimens. Identified DGEBA hydrolysis products included DGEBA-H2O and DGEBA-2H2O, with DGEBA-2H2O being the end product under the time, temperature, and pH conditions studied, which encompass conditions representative of those encountered in drinking water distribution systems (Lane 2015).
Although DGEBA has been identified as a leachate (Xue 2015), in the event of an unforeseen environmental release of DGEBA epoxy resins, they are not expected to become widely distributed in the aquatic environment on the basis of their low water solubility and predicted hydrolysis.
2.7.2 Health effects assessment
During evaluation under the second phase of polymer rapid screening (ECCC, HC 2017), DGEBA based epoxy resins (CAS RN 25085-99-8, 25068-38-6 and 25036-25-3) were identified as requiring further assessment as a result of the presence of epoxy reactive functional groups which are associated with adverse human health effects including subchronic toxicity and dermal sensitization.
DGEBA -based epoxy resins
Commercial DGEBA-based epoxy resins have a low acute oral toxicity in rats, mice and rabbits with an LD50 > 15,000 mg/kg bw. The acute dermal toxicity of commercial DGEBA-based resins is also low when tested on rabbits with an LD50 of 20 mL/kg bw. It also has low dermal toxicity in rats and mice with a LD50 > 1200 and > 800 mg/kg bw, respectively. Lower molecular weight DGEBA-based liquid resins are only slightly irritating to either intact or abraded rabbit skin, however prolonged and repeated exposure may cause a more severe irritation. Higher molecular weight solid resins were less likely to cause irritation, even with prolonged and repeated exposure. Lower molecular weight DGEBA-based resins were moderate dermal sensitizers in both Guinea pigs and mice with a NOEL of 3% and an EC3 of 5.7% respectively, the latter of which translates to an exposure threshold of 1425 µg/cm2. Liquid resins were only minimal eye irritants while solid resins were moderate eye irritants as a result of their abrasive properties (Bingham and Cohrssen, 2012).
Cured resins added to the diet at 1, 5 and 10% for 6 weeks did not result in any behaviour or organ weight differences (Bingham and Cohrssen, 2012).
In a dermal teratology study, rabbits were administered doses of 0, 100, 300, or
500 mg/kg/day on days 6–18 of gestation. No evidence of embryo/fetal toxicity or teratogenicity was observed at any dose. Gavage teratology studies using both rats and rabbits with a low molecular weight BADGE-based epoxy resin were conducted at dose levels of 0, 60, 180, and 540 mg/kg/day in rats, and dose levels of 0, 20, 60, and 180 mg/kg/day in rabbits. There were no adverse effects on mean litter size, pre- and post-implantation losses, or any evidence of a teratogenic or embryotoxic effect at any dose level (Bingham and Cohrssen, 2012). Dermal exposure in pregnant rabbits at doses of 100, 300 or 500 mg/kg bw/day between gestational days 6-18 was not embryo toxic or teratogenic. Teratology studies in rats at the oral doses of 60, 80 and 540 mg/kg bw/day and the rabbits at oral doses of 20, 60, and 180mg/kg bw/day did not result in changes in litter size, pre or post-implantation losses or any evidence of teratogenic or embryo toxicity. A one generation reproductive study in rats at oral doses of 20, 60, 180 and 540 mg/kg bw/day did not affect reproductive parameters in either sex and any of the doses tested (Poole et al., 2004). A dietary carcinogenicity study in mice at a concentration of 10% or dermal studies in mice at concentrations up to 5% with exposure 3 times weekly for 2 years did not result in any increases in the presence of tumors, therefore the resins had a low subchronic toxicity in rodent studies and were not reproductive/developmental toxicants or carcinogenic in vivo (Bingham and Cohrssen, 2012).
In humans, contact dermatitis has been noted in individuals exposed in an occupational setting. The authors of one study established that the 340 molecular weight oligomer was responsible for the dermal sensitization potential of the resin (Bingham and Cohrssen, 2012).
Low molecular weight resin may contain a significant proportion of DGEBA which may leach out of the cured resins and result in direct human exposure. DGEBA has a low acute oral toxicity in rats with an LD50 greater than 2000 mg/kg bw/day. In a subchronic study, rats feed a diet containing 0.1%, 0.3%, 1.0% or 3% (corresponding to 150, 450, 1500, and 4500 mg/kg bw/day) DGEBA for 3 months did not show any gross or histopathological changes, although animals at the highest dose rejected the diet and failed to gain weight. Animals dosed at 1500 mg/kg bw/day exhibited slight enlargement of the kidneys, therefore the NOAEL was established at 450 mg/kg bw/day (Poole et al., 2004).
In a subchronic study, rats were fed a low molecular weight epoxy resin 300, 1500 or 7500 mg/kg bw/day for 26 weeks. All animals at the highest dose died by week 20 but no evidence of systemic toxicity was observed in gross and histopathological examinations. The low and mid dose treated animals also did not show any gross or histopathological findings other than an increase in kidney weights. No NOAEL was reported for the study (Poole et al., 2004).
A NOAEL of 15 mg/kg bw/day was generated in a 2 year rat(Fisher 344) study with oral gavage chronic toxicity/carcinogenicity study based upon a decrease in spleen weight at 100 mg/kg bw/day (Poole et al., 2004).
Dermal application of DGEBA at doses of 10, 100, and 1000 mg/kg bw for 13 weeks in Fisher 344 rats did not cause any apparent systemic toxicity, although high dose animals ate less and lost weight. Dermal application did not alter mortality, clinical observations and behaviour, gross pathology or histopathology with the exception of a local dermatitis therefore a NOAEL of 100 mg/kg bw/day was established (Bingham and Cohrssen, 2012).
Reproductive studies with DGEBA at doses of 50, 540 and 750 mg/kg bw/day did not result in any effects on reproduction even though males and females lost weight at the two highest doses tested (Bingham and Cohrssen, 2012).
A 2 year dermal carcinogenicity study in CF1 mice with DGEBPA at concentrations of 1% and 10% did not show any increase in tumor formation at either of the two concentrations tested. (Zakova et al.,1985).
According to toxicity data for DGEBA (CAS 1675-54-3) and DGEBA containing substances (CAS 25036-25-3 and CAS 25068-38-6) dermal sensitization potential is the main concern associated with these substances. A completely cured epoxy resin contains no free monomer and is non-sensitizing, However, substances containing up to 20% DGEBA monomer, which is a known skin sensitizing substance, and also having an average molecular weight of approximately 1000 daltons or less, produced allergic contact dermatitis in guinea pigs(DME 2012). A NOAEL of 15 mg/kg bw/day was observed in a chronic carcinogencity study in rats treated with low molecular weight resins. Although the resins showed no oncogenic potential and no specific organ toxicity was identified, the NOAEL was established on the basis of atrophy and a decrease in spleen weight at higher doses (EFSA 2005). The hazard for the substance is considered moderate on the basis of a NOAEL of 15 mg/kg bw/day obtained from chronic and carcinogenicity studies in rats, rabbits, and mice.
2.7.3 Characterization of risk to human health
In this assessment, the human health risks were established through consideration of both the hazard and the direct and indirect exposure of the substance for current uses identified from a survey under section 71 of CEPA.
The human health hazard associated with the presence of reactive epoxy groups in DGEBA-based substances is considered moderate on the basis of the available toxicological information. Although exposure to DGEBA epoxy resins through food sources is not expected, there is the potential for unreacted DGEBA present in some can coatings to migrate into the food. However, dietary exposure to DGEBA epoxy resins is unlikely to pose a risk to human health. Dionisi and Oldering (2002) calculated the exposure of DGEBA from food sources which resulted in an exposure of 0.16 µg/kg bw/day for European adults, while Cao et al. (2009) estimated the highest exposure in 12-18 month olds at 22 µg/kg bw/day. When compared to NOAELs of 15 mg/kg bw/day from animal chronic studies, on the basis of splenic effects, there are Margins of Exposure (MOE) of 93,750 and 682 for adults and children (0-18 months), respectively, that are considered adequate to account for uncertainties in the health effects and exposure databases. In addition, dietary exposures are expected to decrease in the future, given the gradual change to DGEBA-free epoxy resins in food packaging applications. Dermal sensitization is not expected to pose a health risk as it requires a threshold value of 1425 µg/cm2 which is not expected to be reached at the current dermal exposure levels. Taking into consideration the direct and indirect exposure to products intended for consumer use, the overall human health risk has been determined to be low.
22.214.171.124 Uncertainties in evaluation of risk to human health
While the higher molecular weight DGEBA epoxy resins contain a limited amount of free DGEBA, the low molecular weight resins contain a significant proportion of DGEBA which may leach out of the cured resins and result in direct human exposure. Therefore, an assumption was made that DGEBA is an indicator for leaching DGEBA epoxy resins.
Some inconsistencies have been found in CAS RNs for DGEBA epoxy resins. For instance CAS RNs 25085-99-8 and 25068-38-6 have been preferably used by U.S. companies and in European Union countries, respectively (DME 2012). Inconsistencies have also been found in each CAS RN for DGEBA epoxy resins. For instance some references used only one CAS RN for all DGEBA epoxy resins but others used two or three (DME 2012, Kirk-Othmer 2014, Bingham 2012, European Commission 2005). In addition, some references used the method of preparation (see routes a, b, and c in Figure 2‑2) for categorizing DGEBA epoxy resins. For instance, routes (b) and (c) for the preparation of DGEBA epoxy resins with n ≤ 4 and n= 4-10, respectively (Boyle 2001, Ullman’s 2012). Despite all the above inconsistent representation, it is believed that the DGEBA epoxy resins have been identified here adequately.
3. Novolac epoxy resin
3.1 Identity of substance
Novolac epoxy resin is a multifunctional epoxy oligomer based upon phenolic formaldehyde novolac (Figure 3‑1). It is made by epoxidation of novolac obtained from condensation of phenol and formaldehyde (Kirk-Othmer 2014). This produces random ortho and para-methylene bridges. An excess of epichlorohydrin is used to minimize the reaction of the phenolic OH groups with epoxidized phenolic groups and, as a result, to prevent branching (Jin 2015). Novolac epoxy resin ranges from a high viscosity liquid of n ≈ 0.2 to a solid of n > 3. Low molecular weight Novolac epoxy resin (n ≤ 0.5) contains a substantial amount of Bisphenol F diglycidyl ether (BFDGE) mixture (ortho-ortho, para-ortho, para-para). Conversely, higher molecular weight Novolac epoxy resin (n > 1) contains a limited amount of BFDGE but is present in oligomeric forms. The epoxy functionality (which is a functional group of concern for human health) is between 2.2 and 3.8.
Figure 3‑1. Representative structure of Novolac epoxy resin
The figure shows structures for the reactants and the final Novolac epoxy resin. Condensation reaction of phenol (c1(ccccc1)O) and formaldehyde (C=O) forms the phenolic formaldehyde novolac. Epoxidation of novolac results in novolac epoxy resin.
3.2 Physical and chemical properties
A summary of physical and chemical properties for Novolac epoxy resin is presented in
|Property||n = 0.2||n = 1.6||n = 1.8|
|Molecular weight (g/mol)||~ 344||~ 570||~ 605|
|Melting/Softening point (°C)||NA||NA||53|
|Boiling point (°C)||> 90||≥ 245||NA|
|Water solubility (mg/L)||slightly soluble (< 1% @ 25°C)||insoluble||insoluble|
|Vapour pressure (Pa)||NA||< 133 @ 20°C||NA|
|Density (g/cm3)||1.18-1.20 @ 25°C||1.22 @ 25°C||NA|
|Epoxy equivalent weight (g/eq.)||172-179||176-181||200|
|Epoxide content (%)||~ 25||~ 24||~ 22|
|Biodegradation (%)||t 1/2 ≈ 5 years||10-16% @ 28d||NA|
|Sources||Kirk-Othmer 2014 Canada 2015 ECCC 2015||Bingham 2012 Ullman’s 2012 Canada 2015 ECCC 2015||Kirk-Othmer 2014|
NA: Not available
3.3 Sources and uses
Novolac epoxy resin has been included in a voluntary survey (ECCC 2015), as well as a mandatory survey conducted under section 71 of CEPA (Canada 2015).
Table 3‑2 presents a summary of the total manufacture and total import quantities for the substance in 2014. These sources indicate that the functional uses for Novolac epoxy resin in Canada are as a binder, crosslinker, and intermediate in adhesive/sealant, paints/coatings, grout, flooring, plastics, metal materials (such as can coating), and auto sealants.
In general, Novolac epoxy resins, when cured, produce tightly cross-linked systems with improved high-temperature performance, chemical resistance, and adhesion over the DGEBA epoxy resins. The thermal stability of Novolac epoxy resins has made them useful for structural and electrical laminates and as coatings and castings for elevated temperature service. Chemical resistance of Novolac epoxy resins makes them useful for lining storage tanks, pumps, and other process equipment as well as for corrosion-resistant coatings (Bingham 2012).
|Substance||Total manufacture (million kg)||Totala imports (million kg)||Survey reference|
|28064-14-4||0.01-0.1||0.1-1||Canada 2015, ECCC 2015|
a Values reflect quantities reported in response to a voluntary survey (ECCC 2015) and a mandatory survey conducted under section 71 of CEPA (Canada 2015). See surveys for specific inclusions and exclusions (schedules 2 and 3).
A number of domestic government databases were searched to determine if Novolac epoxy resin is registered and/or approved for uses in Canada. Novolac may also be used as a component in the manufacture offood packaging materials (personal communication, emails from the Food Directorate, Health Canada to the Risk Management Bureau, Health Canada).
3.4 Potential to cause ecological harm
Critical data and considerations used during the second phase of polymer rapid screening to evaluate the substance-specific potential to cause ecological harm are presented in ECCC (2016).
The above report identified Novolac (CAS RN 28064-14-4; phenol, polymer with formaldehyde, glycidyl ether) as having low water extractability and is therefore not available to aquatic organisms. This substance was characterized as having a low potential for ecological risk. It is unlikely that this substance will result in concerns for organisms or the broader integrity of the environment in Canada.
3.5 Potential to cause harm to human health
3.5.1 Exposure assessment
126.96.36.199 Direct exposure
When used industrially, direct exposure of the general population to Novalac epoxy resin would be similar to DGEBA epoxy resins and thus considered negligible (Bingham 2012).
In Canada, Novalac epoxy resin has been identified as a component used in the manufacture of some food packaging materials, i.e., can coatings where it is used as a crosslinking agent. Only unreacted crosslinking agent will be available for migration into food. Even considering a worst-case scenario, including the assumption that all of the unreacted crosslinking agent would migrate into food, any exposure from such uses is expected to be negligible (personal communication, emails from Food Directorate, Health Products and Food Branch, Health Canada, dated February, 2017; unreferenced.).
Health Canada’s Food Directorate measured the levels of some epoxy resins, including BFDGE, in canned liquid infant formula products in Canada. In that study, BFDGE (the main constituent in low molecular weight Novolac epoxy resin) was found in only 1 sample of the 21 products tested, at a level of 0.04 µg/kg food (Cao et al., 2009).
Novolac epoxy resin is not listed in the Natural Health Products Ingredients Database (NHPID [modified 2017]). It is not found in any drug products, including natural health products (LNHPD [modified 2016], DPD [modified 2015]). Novolac epoxy resin is not used in cosmetics.
Regardless of the products used, the exposure to Novalac epoxy resin by inhalation is not expected due to its predicted low vapour pressure (for solid polymers) and its presence as a cured resin. Dermal exposure to Novalac epoxy resin is not expected as it is available mostly in a cured form.
188.8.131.52 Indirect exposure
In the event of an unforeseen environmental release of Novolac epoxy resin, the substance is not expected to become widely distributed in the aquatic environment on the basis of its low water solubility and predicted hydrolysis. Since Novalac epoxy resin is not biodegradable, there is the possibility that it may be persistent in the environment.
3.5.2 Health effects assessment
The only toxicological information found on Novolac resins was data reported in a Huntsman SDS for RENLAM® 5052 US which is 60-100% Epoxy phenol Novolac resin (CAS RN 28064-14-4) and 30-60% Butanedioldiglycidyl ether (CAS RN 2425-79-8). Toxicity studies were identified as being conducted according to the referenced OECD protocol but were unavailable for review. Epoxy phenol Novolac resin has a low acute oral and dermal toxicity in rats with an LD50 > 2000 mg/kg bw. It is a mild skin and eye irritant in rabbits and was a dermal sensitizer in mice (SDS, 2014). The closest surrogate to the Novolac epoxy resin (BFDGE; CAS RN 2095-03-6) has a moderate dermal sensitization potential with EC3 value of 1.1 which translates to exposure value of 275 µg/cm2 (Delaine et al., 2011). It was mutagenic in vitro when tested in an AMES test or with mammalian cells but was negative for mutagenicity in vivo for both mammalian germ and somatic cells. Novolac resins were not carcinogenic in 2 year chronic studies in rats dosed at 1 or 15 mg/kg bw/ 5 and 7 days/week respectively, or in mice dosed at 0.1 mg/kg bw/ 3 days/week. It was not a reproductive toxicant in a two generation reproductive study in rats and was not teratogenic in a prenatal development studies performed with rats via the oral route or rabbits via the oral or dermal routes. It had a moderate oral subchronic toxicity in a 90-day repeated dose toxicity assay in rats with a NOAEL of 50 mg/kg bw/day and a NOEL of 10 mg/kg bw/day in a rat subchronic dermal assay and a NOAEL of 100 mg/kg bw/day in a 90 day subchronic dermal study performed in mice (SDS, 2014).
3.5.3 Characterization of risk to human health
In this assessment, the human health risks were established through consideration of both the hazard and the direct and indirect exposure of the substance for current uses identified from a survey under section 71 of CEPA.
The human health hazard associated with the presence of reactive epoxy groups in Novolac epoxy resins is considered moderate on the basis of the available toxicological information. Consumption of the resin through food sources is not expected and release of epichlorhydrin is also not expected. Therefore, the human health risk associated with this substance is low. Dermal sensitization is not expected to pose a health risk as it requires a threshold value of 275 µg/cm2, a value that is not expected at current exposure levels.
184.108.40.206 Uncertainties in evaluation of risk to human health
The structure presented for Novolac epoxy resin in Figure 3‑1 has been simplified. In reality, a mixture of branched epoxy resin in ortho and/or para positions would be generated during the manufacture processes.
There were also uncertainties associated with the toxicity as only one reference was identified and the studies were not available for a detailed review.
Despite the above uncertainties, it is believed that the risk conclusions made for Novolac epoxy resin are accurate.
Considering all available lines of evidence presented in this screening assessment, there is low risk of harm to organisms and the broader integrity of the environment from the four epoxy resins. It is concluded that the four epoxy resins do not meet the criteria under paragraphs 64(a) or (b) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends.
On the basis of the information presented in this screening assessment, it is concluded that the four epoxy resins do not meet the criteria under paragraph 64(c) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.
Therefore, it is concluded that the four epoxy resins do not meet any of the criteria set out in section 64 of CEPA.
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Appendix A: Assessment approaches applied during the second phase of Polymer Rapid Screening
The approaches applied during the second phase of polymer rapid screening are outlined in this section. The detailed analyses, as well as the results of the second phase of polymer rapid screening for the individual substances, are presented in Chapters 2 to 3.
Characterization of ecological risk for Epoxy Resins
The ecological risks of epoxy resins were characterized using the approach outlined in the report on the second phase of polymer rapid screening. The approach consisted of multiple steps that addressed different factors related to the potential for a polymer to cause ecological harm. At each step in the rapid screening process, any substance that appeared to present a potential for harm was identified as requiring further assessment. The approach was intended to be pragmatic, protective of the environment, and fairly rapid, largely making use of available or easily obtainable data. This section summarizes the approach, which is described in detail in the report; “Second Phase of Rapid Polymer Screening, Results of the Screening Assessment” (ECCC, HC 2018).
The ecological component of the second phase of polymer rapid screening approach consisted of four main steps to identify polymers that warrant further evaluation of their potential to cause harm. The first step involved identifying polymers which are not likely to be of ecological concern based upon low reported import and manufacture quantities according to Phase Two of the DSL Inventory Update (Canada 2012), a voluntary survey (ECCC 2015) and a mandatory survey conducted under section 71 of CEPA (Canada 2015). Polymers with import and/or manufacture volumes less than 1000 kg per year are not likely to be of ecological concern. This is consistent with the notifying trigger quantity of 1000 kg for polymers under section 7 of the New Substances Notification Regulations (Chemicals & Polymers) [NSNR (C&P)] (Canada 2005).
The second step involved determining whether the polymer will likely have water extractability greater than 2% by weight. Water extractability greater than 2% by weight indicates that the polymer may be more bioavailable to aquatic organisms. The increased potential for exposure to aquatic organisms may present higher ecological risk. Literature, online safety data sheet (SDS) databases, the internal New Substances database for polymers, data gathered through a voluntary survey (ECCC 2015) and a mandatory section 71 survey under CEPA (Canada 2015), and other reliable sources and databases (e.g., QSAR toolbox, ECHA chemical database) were searched for water extractability and solubility information.
The third step in the ecological component involved identifying polymers with reactive functional groups (RFGs). RFGs are groups with chemical functionality that are considered to be reactive and may have damaging effects on the biological community. These groups are well described in Schedule 7 of the NSNR (C&P) (Canada 2005) and polymers containing RFGs may be of increased ecological concern, and require further screening. The RFGs include, among others, potentially cationic or cationic functionalities, alkoxy silanes, and phenols with unsubstituted ortho or para positions. To determine the presence of RFGs, structural information was gathered through a voluntary (ECCC 2015) and a mandatory section 71 survey of CEPA (Canada 2015). For polymers where no representative structures were provided, structural representations were derived from information available for similar polymers: 1) obtained from the internal New Substances program database; 2) from the Chemical Abstract Services (CAS) name; or 3) on the basis of professional knowledge on likely polymerization mechanisms.
The final step of the second phase of polymer rapid screening for ecological considerations involved applying environmental release scenarios to estimate environmental exposure. Two generic aquatic exposure scenarios were applied to identify potential concerns near the point of discharge of a polymer into the environment. These scenarios involved comparing conservative (i.e., ecologically protective) estimates of exposure in receiving waters [predicted environmental concentrations (PEC)] with an effects threshold [predicted no-effect concentration (PNEC)] in order to evaluate whether a polymer is likely to cause harm to the local aquatic environment. The approaches made use of quantity information from each reporting company gathered through Phase Two of the DSL Inventory Update (Canada. 2012), and import and/or manufacture volumes through a voluntary survey (ECCC 2015) and a mandatory survey conducted under section 71 of CEPA (Canada 2015). The aquatic PNEC for each of the scenarios was derived from the critical toxicity value (CTV), which was divided by an assessment factor (AF) as shown:
Aquatic PNEC (mg/L) = CTV / AF
CTVs were based upon empirical or modelled data (where appropriate). Experimental ecotoxicity data were gathered through the voluntary survey and polymer survey under section 71 of CEPA, literature information, as well as read-across data from polymers which have been assessed by the New Substances program. If the scenarios indicated a low likelihood of harm to aquatic organisms (i.e., ratio of PEC/PNEC is less than one), the polymer is anticipated to present low ecological concern.
It is recognized that conclusions resulting from the use of the second phase of polymer rapid screening have associated uncertainties, including commercial activity variations. However, the use of a wide range of information sources (relating to both exposure potential and hazard concerns identified for a polymer), as well as the use of conservative exposure scenarios increase confidence in the overall approach that the polymers identified as not requiring further assessment are unlikely to be of concern.
Information on the decision taken at each step for each polymer is presented in a document titled “Information on the Decision Taken at Each Step for Rapid Screening II of Polymers” (ECCC 2016).
On the basis of available information, DGEBA epoxy resin (25036-25-3) and Novolac epoxy resin (28064-14-4) were identified under the second phase of polymer rapid screening, as not requiring further ecological assessment. It is therefore unlikely that DGEBA epoxy resin (25036-25-3) and Novolac epoxy resin (28064-14-4) result in concerns for organisms or the broader integrity of the environment in Canada.
Characterization of risk to human health for Epoxy Resins
The human health risks of epoxy resins were characterized using the approach outlined in the report; “Second Phase of Polymer Rapid Screening: Results of the Screening Assessment” (ECCC, HC 2017). This process consisted of determining the location of each polymer in a health risk matrix, assigning a low, moderate or high level of potential concern for substances on the basis of their hazard and exposure profiles. The matrix has three exposure bands that represent different exposure potentials which increase from band 1 to 3 and three hazard bands representing different hazard potentials which increase from band A to C.
The first step involved identifying the degree of direct and indirect exposure for each polymer on the basis of its human exposure potential derived through its use pattern, import, manufacture or use quantity and water extractability. To determine if a polymer is used in or is present in a product available to Canadians, numerous additional sources of information related to both domestic and international use and product information were searched and consulted.
The highest exposure band (3) is designated for polymers which are expected to have high direct exposure resulting from their use in products available to consumers that are intended for consumption or application to the body, such as cosmetics, drugs and natural health products. The middle exposure band (2) is designated for polymers which are anticipated to have moderate direct or indirect exposure resulting from the use of polymers in household products that are not intended to be applied to the body or consumed, such as cleaning products, household paint and sealants. The lowest exposure band (1) is designated for polymers which are anticipated to have low direct or indirect exposure. This exposure band includes polymers which are used in the industrial sector to form manufactured articles and which are often contained within or reacted into a cured or hardened polymer matrix during industrial manufacturing.
The second step involved identifying the hazard potential, and corresponding hazard band, for each polymer based upon the presence of reactive functional groups (RFGs) and available toxicological data. Identification of a hazard band was performed independently of the identification of an exposure band. The highest hazard band (C) is associated with polymers which are known or suspected to have a RFG or metals of concern to human health. The highest hazard band is also assigned to polymers for which toxicological data on the polymer or a structurally-related polymer shows or suggests that the polymer may pose a human health risk. The middle hazard band (B) is associated with polymers which do not contain any RFGs or metals of concern to human health but may contain other structural features such as ethylene glycol, aliphatic and aromatic amines or maleic acid anhydrides which may be associated with human health effects. The lowest hazard band (A) is associated with polymers which do not contain a RFG or other structural feature or metals which are known to be associated with human health concerns and available toxicological data indicates a low concern for human health.
The final step combined the exposure and hazard potentials to determine the overall risk potential as represented by the location in the risk matrix. Polymers which have a moderate-to-high exposure potential and the highest hazard potential (cells 2C or 3C) are identified as requiring further assessment to determine their risk to human health.
Polymers that are placed in all other cells of the risk matrix are considered unlikely to cause harm to human health at current levels of exposure. As a result, these polymers are not identified as requiring further human health assessment.
It is recognized that conclusions resulting from the use of this polymer rapid screening approach have associated uncertainties, including commercial activity variations and limited toxicological information. However, the use of a wide range of information sources (relating to both exposure potential and hazard concerns identified for a polymer), as well as the use of conservative exposure scenarios, increase confidence in the overall approach that the polymers identified as not requiring further assessment are unlikely to be of concern.
Information on the decision taken at each step for the substances in this assessment is presented in Second Phase of Rapid Polymer Screening, Results of the Screening Assessment (Health Canada 2017).
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