Indoor Air Reference Levels

Many volatile organic compounds (VOCs) are present in the indoor air of Canadian homes, some of which may pose a risk to human health at certain exposure concentrations. Health Canada has developed exposure limits for a small number of VOCs (benzene, formaldehyde, naphthalene, toluene, acetaldehyde), which were prioritized for full assessments because they are commonly found in Canadian homes and have the potential to cause adverse health effects. To assist public health professionals, including those involved in standards development processes, who may need to assess the possible risk from exposure to other VOCs potentially found in indoor air, Health Canada has developed screening values called Indoor Air Reference Levels (IARLs). The IARLs are intended to supplement Health Canada’s Residential Indoor Air Quality Guidelines.

To identify IARLs, Health Canada evaluated assessments developed by internationally recognized health and environmental organizations. Health Canada did not perform new risk assessments for the IARLs, and only selected the most relevant reference level derived by other organizations. The IARLs listed below represent concentrations that are associated with acceptable levels of risk after long-term exposure (over several months or years) for each specific VOC, as determined by the organization that performed the risk assessment.

Summary of Indoor Air Reference Levels

The IARL selected for each VOC is listed in Table 1. The table also lists the organization from which each IARL was selected. The listed critical effects are the health endpoint used as the basis of the IARL, which is typically the most sensitive effect (i.e. occurs at the lowest exposure concentrations) that is considered relevant to humans.

Table 1. Indoor Air Reference Levels
VOC (CAS No.)	IARL (µg/m³)	Critical effect		Reference
VOC (CAS No.)	IARL (µg/m³)	Cancer	Non-Cancer	Reference
1,3-Butadiene (106-99-0)	1.7	leukemia	-	EC/HC (2000)
1,4-Dichlorobenzene (106-46-7)	60	-	nasal lesions	ATSDR (2006)
2-Butoxyethanol (111-76-2)	11 000	-	hematological effects	EC/HC (2002)
2-Ethoxyethanol (110-80-5)	70	-	reproductive effects	CalEPA (2000)^{Table 1 - Footnote 1}
3-Chloropropene (107-05-1)	1	-	neurotoxicity	US EPA (1991)
Acetone (67-64-1)	70 000	-	developmental effects	VCCEP (2003)
Acrolein (107-02-8)	0.35	-	respiratory epithelial lesions	CalEPA (2008)^{Table 1 - Footnote 1}
Aniline (62-53-3)	1	-	spleen effects	US EPA (1990a)
Carbon tetrachloride (56-23-5)	1.7	adrenal gland tumours	-	US EPA (2010)
Chloroform (67-66-3)	300	-	liver and kidney effects	CalEPA (2000)^{Table 1 - Footnote 1}
Cyclohexane (110-82-7)	6000	-	developmental effects	US EPA (2003a)
Dichloromethane (75-09-2)	600	-	liver effects	US EPA (2011)
Epichlorohydrin (106-89-8)	1	-	nasal lesions	US EPA (1994)
Ethylbenzene (100-41-4)	2000	-	kidney, pituitary gland, and liver effects	CalEPA (2000)^{Table 1 - Footnote 1}
Ethylene oxide (75-21-8)	0.002	lymphoid and breast cancer	-	US EPA (2016)
Isopropyl alcohol (67-63-0)	7000	-	kidney lesions	CalEPA (2000)^{Table 1 - Footnote 1}
Isopropylbenzene^{Table 1 - Footnote 2}(98-82-8)	400	-	kidney and adrenal lesions	US EPA (1997)
Methyl ethyl ketone (78-93-3)	5000	-	developmental effects	US EPA (2003b)
Methyl isobutyl ketone^{Table 1 - Footnote 2} (108-10-1)	3000	-	cardiac malformations	US EPA (2003c)
Propionaldehyde (123-38-6)	8	-	olfactory epithelium atrophy	US EPA (2008)
Propylene oxide (75-56-9)	2.7	nasal tumours	-	US EPA (1990b)
Styrene (100-42-5)	850	-	neurotoxicity	ATSDR (2010)
Tetrachloroethylene (127-18-4)	40	-	neurotoxicity	US EPA (2012), ATSDR (2014)
Toluene diisocyanate (26471-62-5)	0.008	-	decreased lung function	CalEPA (2016)
Xylenes, mixture (1330-20-7)	100	-	neurotoxicity	US EPA (2003d)
Table 1 - Footnote 1 Refers to the actual date of assessment. Toxicological reference value information was summarized from CalEPA (2015), CalEPA (2014), CalEPA (2011) and CalEPA (2008). Return to Table 1 - Footnote 1 referrer Table 1 - Footnote 2 Methyl isobutyl ketone and isopropylbenzene are currently being assessed by Health Canada’s Chemicals Management Plan, which may warrant revisiting the IARL. Return to first Table 1 - Footnote 2 referrer

Contact the Air Health Science Division office if you:

have questions about the Indoor Air Reference Levels
would like to read the document summarizing the methodology for selection of IARLs
would like to read the document summarizing the details and derivation of each IARL

References

ATSDR (2014) Toxicological Profile for Tetrachloroethylene. Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services, Atlanta, GA. https://www.atsdr.cdc.gov/toxprofiles/tp18.pdf.
ATSDR (2010) Toxicological Profile for Styrene. Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services, Atlanta, GA. https://www.atsdr.cdc.gov/toxprofiles/tp53.pdf.
ATSDR (2006) Toxicological Profile for Dichlorobenzenes. Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services, Atlanta, GA. http://www.atsdr.cdc.gov/toxprofiles/tp10.pdf.
CalEPA (2016) Technical Support Document for the Derivation of Noncancer Reference Exposure Levels. Appendix D1 – Toluene Diisocyanate Reference Exposure Levels. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/air/report-hot-spots/finaltdirelmarch2016.pdf.
CalEPA (2015) Appendix L. Air Toxics Hot Spot Program - Guidance manual for Preparation of Health Risk Assessments - OEHHA/ARB Health Values for Use in Hot Spot Facility Risk Assessments. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/2015gmappendiceslm.pdf.
CalEPA (2014) Appendix D1. Air Toxics Hot Spot Program - Summaries using this version of the hots spots risk assessment guidelines. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/appendixd1final.pdf.
CalEPA (2011) Appendix B. Air Toxics Hot Spot Program - Chemical-specific summaries of the information used to derive unit risk and cancer potency values. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/appendixb.pdf.
CalEPA (2008) Appendix D3. Air Toxics Hot Spot Program - Chronic RELs and toxicity summaries using the previous version of the hot spots risk assessment guidelines. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/appendixd3final.pdf.
Environment Canada and Health Canada (EC/HC) (2002) Priority Substances List Assessment Report: 2-Butoxyethanol. En40-215/66E, Minister of Supply and Services Canada, Ottawa, ON.
EC/HC (2000) Priority Substances List Assessment Report: 1,3-Butadiene. En40-215/52E, Minister of Supply and Services Canada, Ottawa, ON.
US EPA (2016) Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide (CASRN 75-21-8). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-16/350Fa, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1025tr.pdf.
US EPA (2012) Toxicological Review of Tetrachloroethylene (Perchloroethylene) (CAS No. 127-18-4). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/011F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0106tr.pdf.
US EPA (2011) Toxicological Review of Dichloromethane (Methylene Chloride). (CAS No. 75-09-2). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-10/003F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0070tr.pdf.
US EPA (2010) Toxicological Review of Carbon Tetrachloride (CAS No. 56-23-5). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/005F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0020tr.pdf
US EPA (2008) Toxicological Review of Propionaldehyde (CAS No. 123-38-6). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/003F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1011tr.pdf.
US EPA (2003a) Toxicological Review of Cyclohexane (CAS No. 100-82-7). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-03/008, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1005tr.pdf.
US EPA (2003b) Toxicological Review of Methyl Ethyl Ketone (CAS No. 78-93-3). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA 635/R-03/009, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0071tr.pdf.
US EPA (2003c) Toxicological Review of Methyl Isobutyl Ketone (CAS No. 108-10-1). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-03/002, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0173tr.pdf.
US EPA (2003d) Toxicological Review of Xylenes (CAS No. 1330-20-7). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-03/001, United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0270tr.pdf.
US EPA (1997) Toxicological Review of Cumene (Isopropyl Benzene) (CAS No. 98-82-8). In support of summary information on the integrated risk information system (IRIS). United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0306tr.pdf.
US EPA (1994) Toxicological Review of Epichlorohydrin (CASRN 106-89-8). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0050_summary.pdf.
US EPA (1991) Toxicological Review of Allyl chloride (CASRN 107-05-1). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0387_summary.pdf.
US EPA (1990a) Toxicological Review of Aniline (CASRN 62-53-3). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0350_summary.pdf.
US EPA (1990b) Toxicological Review of Propylene Oxide (CASRN 75-56-9). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0403_summary.pdf.
VCCEP (2003) Acetone (Cas No. 67-64-1). VCCEP Submission. Voluntary Children's Chemical Evaluation Program, Washington, DC. http://www.tera.org/Peer/VCCEP/Acetone/acevccep.pdf.

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