Priority Substances List Assessment Report for Ammonia in the Aquatic Environment

1.0 Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) requires the federal Ministers of the Environment and of Health to prepare 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" or capable of becoming "toxic" as defined in Section 64 of the Act, which states:

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 ammonia in the aquatic environment provided by the Ministers' Expert Advisory Panel on the Second Priority Substances List (Ministers' Expert Advisory Panel, 1995) was as follows:

Anthropogenic sources of ammonia in Canada include effluent from sewage treatment plants, steel mills, fertilizer plants, the petroleum industry and intensive farming. Releases from these sources can result in locally elevated concentrations. At several point sources in Canada, concentrations exceed the threshold levels of sensitive species such as rainbow trout. An assessment of ammonia in the aquatic environment is needed to evaluate the extent of the problem.

Following an initial scoping exercise, it was decided that the scope of the assessment was too narrow and that it should be expanded to include the atmospheric and terrestrial environments in Canada. This decision was based on the findings of European researchers that ammonia transmitted by air to sensitive terrestrial ecosystems was having negative impacts on those ecosystems. Several of the impacted European ecosystems, conifer forests in particular, exist in large areas of Canada. Also, the atmospheric chemistry of ammonia is such that its interactions with sulphates form fine respirable particulate matter (PM_2.5 and PM₁₀). Since "Respirableparticulate matter less than or equal to 10 microns" (i.e., PM₁₀) has been determined to be "toxic" to humans under CEPA 1999, an evaluation of the role of ammonia in the formation (but not the environmental effects) of respirable particulate matter was warranted.

A description of the approaches to assessment of the effects of Priority Substances on the environment is available in a published companion document. 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 Advancemen Directorate
Environment Canada
Ottawa, Ontario
K1A 0H3

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

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

The Assessment Report was written by M. Constable, F. Jensen, K. McDonald, K. Taylor and M. Charlton (Canada Centre for Inland Waters) of Environment Canada. The Assessment Report was reviewed by and portions of the supporting documentation (Environment Canada, 2000) related to the assessment of ammonia were prepared by the following members of the Environmental Resource Group, established by Environment Canada to support the environmental assessment:

• P. Chambers, National Water Research Institute,
  Environment Canada
• G. Craig, GR Craig and Associates
• P. Doyle, Environment Canada
• J. Farrell, Canadian Fertilizer Institute
• L. Gammie, Canadian Water and Wastewater
  Association
• J. Haskill, Environment Canada
• S. McGinn, Agriculture and Agri-Food Canada
• J. McLernon, Environment Canada
• D. Moore, The Cadmus Group, Inc.
• B. Munson, Environment Canada
• D. Penney, Alberta Agriculture
• K. Reid, Ontario Ministry of Agriculture,
  Food and Regional Affairs
• S. Sheppard, EcoMatters
• W. Windle, Environment Canada

Environmental sections of the Assessment Report and supporting documentation (Environment Canada, 2000) were also reviewed by external reviewers:

• J. Diamond, TetraTech Inc.
• B. Parkhurst, The Cadmus Group, Inc.

The basis for recommending inclusion of ammonia in the aquatic environment by the Ministers' Expert Advisory Panel on the Second Priority Substances List was limited to environmental effects (namely, effects on sensitive aquatic species). As a result, the principal focus of this assessment is a determination of whether ammonia is "toxic" under Paragraph 64(a) of CEPA 1999. However, in view of the expansion of the scope of the assessment of environmental effects to address the terrestrial environment (through exposure via air) as well, effects of ammonia in air and water on human health were also considered, at least in a preliminary fashion, primarily to ensure that conclusions drawn on the basis of a more robust data set on environmental effects would also be protective of human health.

The database on the effects of ammonia relevant to assessment of the effects on human health is limited principally to early short-term studies in animals, older reports of accidental exposures of humans, limited clinical studies and one cross-sectional study of an occupationally exposed population (Health Canada, 1999).

The paucity of information on effects in experimental animals and humans is likely attributable to the considerably greater amounts of ammonia produced endogenously in humans through metabolism in the synthesis of amino acids, nucleosides and other nitrogen-containing compounds compared with environmental exposure, as well as to its relatively low toxicity.

Because of the focus on environmental effects and in view of the limitations of the data relevant to assessment of the effects on human health, a screening assessment was conducted, in which the limited number of identified effect levels for ammonia in the more relevant studies were compared with worst-case or bounding estimates of exposure in air (including indoor air) and drinking water and the adequacy of these rather crude margins of exposure was considered. On the basis of the magnitude of these margins, which are considered sufficient to account for various elements of uncertainty and variability, ammonia is not considered a priority for investigation of options to reduce public exposure through control of sources that are addressed under CEPA 1999 (Health Canada, 1999), and the remainder of this assessment addresses effects on the environment. Unpublished supporting documentation on the health-related effects of ammonia in the aquatic environment, which presents additional information, is available upon request from:

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

A draft of the Assessment Report was made available for a 60-day public comment period (May 13 to July 12, 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 responses is available on the Internet at:

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

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, which presents additional information, is available upon request from:

Commercial Chemicals Evaluation Branch
Environment Canada
14th Floor, Place Vincent Massey
351 St. Joseph Blvd.
Hull, Quebec
K1A 0H3