Priority Substances List Assessment Report for N-Nitrosodimethylamine (NDMA)

1.0 Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) requires the federal Ministers of Environment and of Health to develop and publish a Priority Substances List (PSL) that identifies substances, including chemicals, groups of chemicals, effluents and wastes, that may be harmful to the environment or constitute a danger to human health. The Act also requires both Ministers to assess these substances and determine whether they are "toxic" as defined in Section 64 of the Act, which states:

... a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that

1. have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
2. constitute or may constitute a danger to the environment on which life depends; or
3. constitute or may constitute a danger in Canada to human life or health.

Substances that are assessed as "toxic" as defined in Section 64 may be placed on Schedule I of the Act and considered for possible risk management measures, such as regulations, guidelines, pollution prevention plans or codes of practice to control any aspect of their life cycle, from the research and development stage through manufacture, use, storage, transport and ultimate disposal.

Based on initial screening of readily accessible information, the rationale for assessing NDMA provided by the Ministers' Expert Advisory Panel on the Second Priority Substances List (Ministers' Expert Advisory Panel, 1995) was as follows:

NDMA is used in rubber formulations and in the organic chemical industry. The general population is exposed to the substance from ambient air; from foods, including beer, cured meats, fish, and cheeses; from smoking and chewing tobacco; from cosmetic products, including shampoos, conditioners, and children's bath products; from the interior air of automobiles as a result of NDMA use in upholstery and rubber products; and from various household products. There are already steps to minimize exposure to this potent carcinogen from some specific sources including food, cosmetics, pesticides and rubber nipples. However, there are also public health concerns about potential airborne exposure. Moreover, most assessments have not considered the general public's exposure from all sources. An assessment is required to determine the extent of exposure and the associated risks to human health and the environment in Canada.

Descriptions of the approaches to assessment of the effects of Priority Substances on the environment and human health are available in published companion documents. The document entitled "Environmental Assessments of Priority Substances under the Canadian Environmental Protection Act. Guidance Manual Version 1.0 - March 1997" (Environment Canada, 1997a) provides guidance for conducting environmental assessments of Priority Substances in Canada. This document may be purchased from:

• Environmental Protection Publications
  Environmental Technology Advancement Directorate
  Environment Canada
  Ottawa, Ontario
  K1A 0H3

It is also available on the Internet at www.ec.gc.ca/cceb1/eng/psap.htm under the heading "Technical Guidance Manual." It should be noted that the approach outlined therein has evolved to incorporate recent developments in risk assessment methodology, which will be addressed in future releases of the guidance manual for environmental assessments of Priority Substances.

The approach to the assessment of effects on human health is outlined in the following publication of the Environmental Health Directorate of Health Canada: "Canadian Environmental Protection Act - Human Health Risk Assessment for Priority Substances" (Health Canada, 1994), copies of which are available from:

• Environmental Health Centre
  Room 104
  Health Canada
  Tunney's Pasture
  Ottawa, Ontario
  K1A 0L2

or on the Environmental Health Directorate publications web site - www.hc-sc.gc.ca/ehp/ehd/catalogue/bch.htm. The approach is also described in an article published in the Journal of Environmental Science and Health -Environmental Carcinogenesis & Ecotoxicology Reviews (Meek et al., 1994). It should be noted that the approach outlined therein has evolved to incorporate recent developments in risk assessment methodology, which are described on the Environmental Substances Division web site (www.hc-sc.gc.ca/ehp/ehd/bch/env_contaminants/psap/psap.htm) and which will be addressed in future releases of the approach paper for the assessment of effects on human health.

The search strategies for identification of data relevant to assessment of potential effects on the environment (prior to August 1998) and on human health (prior to August 1999) are presented in Appendix A. Review articles were consulted where appropriate. However, all original studies that form the basis for determining whether NDMA is "toxic" under CEPA 1999 have been critically evaluated by staff of Environment Canada (entry and environmental exposure and effects) and Health Canada (human exposure and effects on human health).

Almost all of the environmental information was incorporated into the Assessment Report, and therefore no supporting document for the environmental assessment of NDMA was prepared. Sections of the Assessment Report related to the environmental assessment of NDMA were prepared by the following members of the Environmental Resource Group, established by Environment Canada to support the environmental assessment of NDMA:

• H. Atkinson, Environment Canada
• V. Taguchi, Ontario Ministry of the Environment
• W. Windle, Environment Canada

Other members of the Environmental Resource Group who reviewed the document and participated in discussions were:

• S. Abernethy, Ontario Ministry of the Environment
• T. Boose, Uniroyal Chemical Ltd.
• R. Breton, Environment Canada
• N. Bunce, University of Guelph
• A. Edmonds, Ontario Ministry of the Environment
• T. Leah, Environment Canada
• F. Onuska, Environment Canada
• B. Patel, Chinook Group
• G. Rutherford, Ontario Ministry of the Environment

Environmental sections of the Assessment Report were also reviewed by the following people: R. Chénier (Environment Canada), G. Moore (Health Canada), A. McLarty (Ontario Ministry of the Environment), E. McBean and

• J. Kochany (Conestoga-Rovers & Associates) and
• D. Carlisle (Brez-Carlisle Inc.). Special acknowledgement is given to the following staff of the Ontario Ministry of the Environment for their assistance: L. MacDonnell, B. Birmingham, G. Rutherford, R. Angelow, D. Spry and S. Abernethy.

The content of the health-related sections of this Assessment Report and supporting documentation was prepared by the following staff of Health Canada, based, in part, on background information compiled by BIBRA Toxicology International (1997, 1998):

• R. Beauchamp
• K.Byrne
• R.G. Liteplo
• M.E. Meek
• M. Walker

In order to address primarily adequacy of coverage, sections of the supporting documentation pertaining to human health were reviewed externally by B. Birmingham (Ontario Ministry of the Environment) and R. Brecher (Globaltox International Consultants, Inc.).

Accuracy of reporting, adequacy of coverage and defensibility of conclusions with respect to hazard characterization and dose-response analysis were considered at a panel meeting of the following members, convened by Toxicology Excellence for Risk Assessment (TERA) on August 12, 1999, in Ottawa, Ontario:

• M. Bogdanffy, DuPont Haskel Laboratory
• J. Christopher, California Environmental Protection Agency
• M. Dourson, TERA
• S. Felter, Procter & Gamble
• J. Mandel, Exponent
• R. Rudel, Silent Spring Institute
• V. Walker, New York State Department of Health
  
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The health-related sections of the Assessment Report were reviewed and approved by the Health Protection Branch Risk Management meeting of Health Canada.

The entire Assessment Report was reviewed and approved by the Environment Canada/Health Canada CEPA Management Committee.

A draft of the Assessment Report was made available for a 60-day public comment period (February 19 to April 19, 2000) (Environment Canada and Health Canada, 2000). Following consideration of comments received, the Assessment Report was revised as appropriate. A summary of the comments and their responses is available on the Internet at:

www.ec.gc.ca/cceb1/eng/final/index_e.html

The text of the Assessment Report has been structured to address environmental effects initially (relevant to determination of "toxic" under Paragraphs 64(a) and (b)), followed by effects on human health (relevant to determination of "toxic" under Paragraph 64(c)).

Copies of this Assessment Report are available upon request from:

• Inquiry Centre
  Environment Canada
  Main Floor, Place Vincent Massey
  351 St. Joseph Blvd.
  Hull, Quebec
  K1A 0H3

or on the Internet at:

www.ec.gc.ca/cceb1/eng/final/index_e.html

Unpublished supporting documentation on the health-related effects of NDMA, which presents additional information, is available upon request from:

• Environmental Health Centre
  Room 104
  Health Canada
  Tunney's Pasture
  Ottawa, Ontario
  K1A 0L2