Summary of public comments received on the draft screening assessment for naphthalene sulfonic acids and salts group

Comments on the draft Screening Assessment for Naphthalene Sulfonic Acids and Salts Group, assessed under the Chemicals Management Plan (CMP), were submitted by the Canadian Consumer Specialty Products Association, Canadian Fuels Association and Prevent Cancer Now.

Summarized public comments and responses are provided below, organized by topic.

Consultations and stakeholder engagement

Comment Summary 1: Stakeholders remain available should further input be required in the finalization of the assessment.

Response 1: Noted.

Comment Summary 2: The peer review process should take advantage of the knowledge and experiences of university researchers and otherwise independent specialists, in addition to larger organizations. Consulting with different knowledge bases and perspectives will strengthen the programme, make its consultation process much more effective and strengthen its credibility.

Response 2: Peer reviews are critical to ensuring the relevance and accuracy of data and information applied in the assessment. External peer reviewers are selected based on their experience and/or technical expertise with issues or areas of uncertainty identified in the assessment. Their credentials are carefully considered before they are selected. Peer reviewers may come from academia, industry, consulting firms or government (including government experts from other countries). Peer reviews are conducted prior to the publication of draft screening assessments. The peer reviewers for the assessment are noted in the Introduction of the report. Comments from all peer reviewers are considered.

Persistence

Comment Summary 3: In section 6.2 (environmental persistence), the data would more appropriately support a determination that NSAs may persist in the environment, rather than the proposal that “NSAs are likely to persist in the environment in water, soils and sediments (for example, have half-lives greater than 182 days in water and soil or greater than 365 days in sediments).”

Response 3: Changes have been made to the Persistence section, including addition of new information on the inherent biodegradability of C₉-rich DANSA, a close analogue, and a re-evaluation of the modelled data. The new information that C₉-rich DANSA is not inherently biodegradable suggests that NSAs with alkyl chains are likely to persist in water, sediment and soil.

Comment Summary 4: The modeling approaches show biodegradation half-life predictions of <182 days (CATALOGIC) and similarly, weeks to months with BIOWIN. As such, we do not see the rationale for estimating the half-life up to 200 days. There is little evidence supporting this timeline.

Response 4: The empirical analogue data for long-chain NSAs were used preferentially over the modelled data. These data showed low to no biodegradation in OECD ready and inherent biodegradation tests. For this reason, biodegradation half-lives of up to 200 days were considered in the risk assessment.

Comment Summary 5: The empirical biodegradation data range widely, and do not necessarily support the determination of persistence.

Response 5: For the five NSAs with alkyl chains, the empirical persistence data for the two longer-chain NSA analogues are given more weight than the data for the other analogue substances, as they are most structurally similar. These substances show very low or no biodegradation in the ready and inherent biodegradation studies. Based on these data, NSAs with alkyl chains are likely to persist in water, and by extrapolation, in soil and sediment. It has been clarified in the screening assessment that NaNSA is not expected to persist in the environment, on the basis of the data presented for the structurally similar analogue 2-NSA.

Comment Summary 6: We do not agree with the use of Kölbel (1964) in the persistence assessment. Assessing biodegradation using a culture of E. coli is not representative of a biodegradation test, nor is it environmentally relevant.

Response 6: The Kölbel (1964) study is not used directly in the assessment of persistence. It is used to show trends in biodegradation of NSAs with different chain lengths of alkyl substituents. The text has been modified to clarify this.

Bioaccumulation

Comment Summary 7: The summary should be corrected to indicate that, based on modeling, CDINSA is not bioaccumulative.

Response 7: The modeling data are no longer included in the screening assessment, as more experimental data on the bioaccumulation of NSAs became available. The assessment of bioaccumulation potential for CDINSA is now based upon read-across data for DNNDSA, which indicates that CDINSA is not bioaccumulative.

Comment Summary 8: The experimental data for analogue substances, that show that these substances do not bioaccumulate, was not given the appropriate weight when assessing bioaccumulation potential.  The only data that suggests bioaccumulation potential is modeling data.

Response 8: New experimental data have been added to the report. Consequently, the determinations regarding bioaccumulation have been changed in consideration of these experimental results. The assessment now indicates that none of the NSAs appear to be bioaccumulative.

Health effects

Comment Summary 9: The assessment did not address potential effects on molecular signalling, such as endocrine disruption, for both parent compound and metabolites even though substances in the Naphthalene Sulfonic Acids and Salts group have a conjugated ring structure similar to known endocrine disruptors. Endpoints representing endocrine toxicity, and exposure of individuals and their offspring, were not considered.

Response 9: In screening assessments conducted under Canadian Environmental Protection Act, 1999 (CEPA), information on endocrine-related effects is considered when available. There is a lack of empirical health effects data to suggest that the substances in the Naphthalene Sulfonic Acids and Salts Group have endocrine disrupting effects. The available health effects data for the analogues presented in the screening assessment, which included results from repeat dose and reproduction / developmental toxicity studies in laboratory animals, were also considered. The risk characterization of these substances took into consideration uncertainties in the health effects and exposure databases. For more information, please refer to the RA Series Fact sheet: Consideration of endocrine-related effects in risk assessment.

Comment Summary 10: There is a lack of data on systemic toxicity as well as acute and chronic hazard of substances in this Group. 

Response 10: Screening assessments conducted under CEPA are based on the best available data. The lack of substance-specific health effects data is noted in the screening assessment and is addressed by employing a read-across approach. Uncertainties in the health effects database were taken into consideration in the risk characterization of these substances.    

Comment Summary 11: Substances in the Naphthalene Sulfonic Acids and Salts group are identified with “warning” and “danger” notices regarding skin and eye damage, irritation and sensitization. Sensitization to organic chemicals can be very serious, as it is the first step in the development of multiple chemical sensitivities.

Response 11: Screening assessments of existing substances conducted under the Chemicals Management Plan (CMP) generally focus on critical effects related to systemic toxicity including reproductive and developmental toxicity, and genotoxicity and carcinogencity for the purpose of characterizing potential risk to human health for the Canadian general population. The best and most relevant available data on the potential human health effects of NSAs and exposure of the general population were considered. The screening assessment does not list or describe all available data, but rather presents only the relevant information key to the risk characterization.

Ecological exposure

Comment Summary 12: The screening assessment does not include measured data on discharges to the environment.

Response 12: The draft assessment included data on concentrations of NSAs in wastewater effluent in Canada. New data have been added to the assessment on concentrations of NSAs in river sediment from Ontario, which were not available at the time that the draft screening assessment was prepared. No other measured data on environmental concentrations or releases were available.

Human exposure assessment

Comment Summary 13: The screening assessment did not assess occupational exposures, which excludes people who would be expected to be the most highly exposed group. There is a need to assess workplace issues under the Hazardous Products Regulations or occupational health in general.

Response 13: Screening assessments conducted under CEPA focus on risks of exposure to the general population, rather than risks of exposures in the workplace. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System (WHMIS).

The Government of Canada is currently working with the provinces and territories to explore ways to enhance the protection of workers from exposure to chemicals by integrating and leveraging the information, tools, and/or technical expertise of the Chemicals Management Plan and Health Canada’s Workplace Hazardous Products Program.

Comment Summary 14: Trends in manufacture and use of NaNSA, which is the highest-volume substance, as well as importation and use of other analogues, should also be presented. Instead, claims of confidentiality were accepted.

Response 14: Based on all available information, which included information provided through CEPA section 71 surveys and subsequent follow-ups with industry, it was determined that the general population is not expected to be exposed to NaNSA. 

Information on uses of NaNSA was available to the Government of Canada and assessed, even though it could not be disclosed in the screening assessment due to confidentiality claims. The screening assessment has been revised for clarity.

Uses of other substances outside the Naphthalene Sulfonic Acids and Salts Group, as defined in this screening assessment, are outside the scope of this screening assessment.

Read-across approach

Comment Summary 15: The assessment does not use a read-across approach to assess health effects for substances with one or no alkyl chain, despite these being the predominant substances in commerce, while data is noted for three larger molecule congeners with multiple alkyl chains.

Response 15: Read-across is conducted on a substance by substance basis to address specific data gaps. Read-across for NaNSA was not required as exposure to the general population was not expected and risk to human health was considered to be low on this basis.

The other substances in the group (that is, DNNSA, CaDNNSA and DNNDSA) were assessed using a read-across approach to inform the human health assessment. These substances have a higher molecular weight and different chemical structure (for example, each have two C9 alkyl chains) compared to NaNSA and naphthalene, and are not expected to degrade in the environment. Thus, it is unlikely that they would share a similar toxicity profile. More appropriate analogues were selected to inform the human health assessment of DNNSA, CaDNNSA and DNNDSA.

Risk characterization

Comment Summary 16: There is an absence of health data for NaNSA and a scarcity of health data for other substances in this group, while potentially highly-exposed populations and younger age groups, like teenagers, were not duly considered. As such, the proposed conclusion is premature.

Response 16: Screening assessments conducted under CEPA are based on the best available data at time of assessment.

It was determined that the Canadian general population is not expected to be exposed to NaNSA. Also, NaNSA was not identified as posing a high hazard to human health, therefore risk to human health from NaNSA was determined to be low. Further investigation into its health effects beyond what was described in the screening assessment was not warranted. 

The potential for exposure to substances in the Naphthalene Sulfonic Acids and Salts Group was considered for all relevant segments of the Canadian general population, including younger age groups, and no risk to human health was identified. Considering the adequate margin of exposure for adults in the screening assessment, the potential use of general purpose aerosol lubricants by teenagers would similarly be expected to not result in a risk to human health.

Comment Summary 17: Naphthalene sulfonic acids and salts, including but not limited to those subject to this screening assessment, are widely used in Canada in both industrial and consumer settings. There are uncertainties associated with the quantities manufactured and imported, but conceivably range over a million kilograms in total.

Response 17: Noted.

Comment Summary 18: The screening assessment does not assess uses, exposures or health effects of NaNSA despite it being closely related to naphthalene, a substance listed on the CEPA Schedule 1 list of toxic substances.

Response 18: Based on all available information, which included information provided through CEPA section 71 surveys and subsequent follow-up with industry, it was determined that the Canadian general population is not expected to be exposed to NaNSA. Also, NaNSA was not identified as posing a high hazard to human health. As such, risk to human health was determined to be low and further investigation of health effects beyond what was described in the screening assessment was not warranted.

Comment Summary 19: NaNSA was represented by naphthalene-2-sulphonic acid (2-NSA), which is listed by the European Chemicals Agency (ECHA) with a Danger warning about potential detrimental impact on human health and aquatic life.

Response 19: The substance naphthalene-2-sulfonic acid (2-NSA), which is similar to NaNSA, was used as an analogue to inform the ecological assessment. The Classification, Labelling and Packaging (CLP) legislation Cancer Category 2 label for 2-NSA is a result of an impurity (naphthalene) reported in some notifications and is not specific to 2-NSA or NaNSA.

Naphthalene was assessed under CMP as part of the Challenge; the final screening assessment can be found here.

Comment Summary 20: It is unclear how the government is identifying NaNSA as not posing a high hazard to human health. The Canadian assessment should include the detailed evidence and analysis that form the basis of these conclusions, and reference the international agencies.

Response 20: Classifications for carcinogenicity, mutagenicity, reproductive or developmental toxicity are established by international organizations such as the United States Environmental Protection Agency (US EPA), the European Chemicals Agency (ECHA) and the International Agency for Research on Cancer (IARC), and are publicly available. The basis of classifications of substances by such organizations is available though each respective programme.

NaNSA was not found to be internationally classified for any of the above-mentioned endpoints.

Comment Summary 21: The assessment should consider a carcinogenic or endocrine disruption potential for the substances in the Naphthalene Sulfonic Acids and Salts Group and as such only consider a zero threshold acceptable. The probability of disproportionately high marginal increases in hazards at low doses is a reasonable assumption here. Relying on the Threshold of Toxicological Concern (TTC) approach for health effects of hazardous chemicals is not justified. It is necessary to gather more information to carry out this evaluation.

Response 21: There are insufficient data to suggest that any of the substances or analogues used to inform the health effects of the Naphthalene Sulfonic Acids and Salts Group have carcinogenic potential. Available genotoxicity data showed negative results and modelling described in this approach did not produce any structural alerts for genotoxicity.

The Threshold of Toxicological Concern (TTC)-based Approach was published as a Science Approach Document and was subject to a 60-day public comment period. The Approach considers genotoxicity and carcinogenicity, and addresses endocrine-related effects.

Comment Summary 22: The screening assessment does not present measured exposure data.  Environmental discharges were modelled, but not human exposures for manufacturing, use or in the environment.

Response 22: Measured exposure data are considered when available and appropriate for the Canadian context. Modelled data are used in the absence of applicable measured data. Potential exposures of the Canadian general population from the environment (including as a result from industrial releases to water) and from the use of a product available to consumers were derived using modelled data where measured data were not available.

Comment Summary 23: Environmental and human health effects of metabolites and degradation products may dwarf the effects of the parent compounds and the assessment does not clearly state how it considers their impact.  Other sources of substances in the Naphthalene Sulfonic Acids and Salts Group, such as substances degrading into naphthalene derivatives, should be considered in a cumulative assessment.

Response 23: Additional sources of substances in the Naphthalene Sulfonic Acids and Salts Group (that is, via degradation) would be captured within available measured data on substances in the Group, if available.

Metabolites are considered as part of the human health effects assessment in the context of their potential contribution to health effects observed in studies.

Metabolites are now considered as part of the ecological assessment in section 7.1.1 Mode/mechanism of action. Description of a new frog ecotoxicity study which discusses metabolites of NSAs was added. In addition, the major metabolites of NSAs were predicted and run through models to determine their mode of action. The results of this modelling is included in an appendix of the assessment.

Alternatives and informed substitution

Comment Summary 24: The screening assessment did not consider possible least-toxic alternatives to the use of these substances.

Response 24: When a risk has been identified in the development of risk management activities, the CMP considers substitutes and alternatives whenever possible and when adequate and relevant information is available on the economic, social and environmental implications for Canada.  However, in this case no risks or toxic substances have been identified.

Conclusions

Comment Summary 25: We support the proposed conclusion that the NSAs group of substances 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, and we support the ministers’ proposal to 1) take no further action on the group at this time under section 77 of CEPA for the two substances identified under subsection 73(1) of the Act, 2) and to take no further action on the other four substances at this time.

Response 25: Noted.