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Aluminum salts final content: chapter 1

1. Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) requires the 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 to determine whether they meet or are capable of meeting the criteria as defined in section 64 of the act. A substance meets the criteria under CEPA 1999 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

For substances deemed to meet the criteria defined in section 64, risk management measures  are identified and implemented in consultation with stakeholders, in order to reduce or eliminate the risks posed to human health or the environment. These measures may include regulations, guidelines, pollution prevention plans or codes of practice to control any aspect of the life cycle of the substance, from the research and development stage through to manufacture, use, storage, transport and ultimate disposal.

Based on initial screening of readily accessible information, the rationale provided by the Ministers' Expert Advisory Panel in 1995 for including aluminum chloride, aluminum nitrate and aluminum sulphate on the second Priority substances list was as follows (Environment Canada and Health Canada 2000):

"Aluminum, from both natural and man-made sources, is widespread in the Canadian environment. Intakes of aluminum among the human population and ambient airborne concentrations in some parts of the country are close to those that have induced developmental and pulmonary effects in animal studies. Epidemiological studies have indicated that there may be a link between exposure to aluminum in the environment and effects in humans. Aluminum compounds are bioaccumulative, and can cause adverse ecological effects, especially in acidic environments. The Panel identifies three aluminum compounds as being of particular concern. An assessment is needed to establish the weight of evidence for the various effects, the extent of exposure and the aluminum compounds involved. If necessary, the assessment could be expanded to include other aluminum compounds."

A preliminary report was completed for the three aluminum salts and released as a State of the Science (SOS) report in December 2000. With respect to immediate or long term harmful effects of the three aluminum salts on the environment or its biological diversity, the report proposed that, based on measured and estimated aluminum levels in Canadian aquatic and terrestrial environments receiving direct inputs of aluminum from the use of aluminum salts and on the predicted no-effect concentrations (PNECs) derived from experimental data for aquatic and terrestrial biota, it is in general unlikely that organisms are exposed to harmful levels of aluminum resulting from the use of aluminum salts in Canada.

With respect to human health, a conclusion regarding section 64(c) could not be reached in 2000, owing to the limitations in the available data for assessing health effects. Therefore, the assessment of aluminum salts was suspended in December 2000 for a period of six years to allow for the development of additional human health effects data in order that Health Canada could reach a conclusion on whether aluminum salts (chloride, nitrate and sulphate) and possibly other aluminum compounds should be considered as "toxic" under CEPA 1999.

In terms of this PSL assessment, the conclusions made under section 64 of CEPA 1999 relate directly to the three aluminum salts nominated by the Ministers’ Expert Advisory Panel (aluminum chloride, nitrate, and sulphate). However, different approaches are taken by Environment Canada and Health Canada in evaluating the potential for risk.

In characterizing the potential for risk to the environment, data relevant to the entry of the three listed salts into the Canadian environment from local point sources (such as, drinking water treatment plants) were examined in conjunction with data on environmental fate and exposure. The focus was on assessing potential for effects on the environment near point sources. This evaluation formed the basis for determining whether the three aluminum salts identified by the Ministers' Expert Advisory Panel (chloride, nitrate and sulphate) are "toxic" under section 64 of CEPA 1999. 

The human health risk characterization consists of a two-stage evaluation. In the first stage, exposure of the general Canadian population to total aluminum in air, drinking water, diet, and soil is evaluated. Although the relative bioavailabiilties of aluminum in these different media are also assessed, no distinction is made in the exposure assessment at this first stage with regard to the specific salts contributing to total aluminum exposure. This stage allows for a comparison of the total aluminum intake with the estimated exposure level of concern, and therefore provides a characterization of human health risk in relation to total aluminum exposure from the four media. In the second stage, the relative contribution of each of the three listed aluminum salts (chloride, nitrate, and sulphate) to this total aluminum exposure is evaluated, and a decision with respect to section 64(c) of CEPA 1999 is made for the three salts.

Health Canada chose this two-stage approach on the basis of both scientific and practical considerations. First, overall exposure to the aluminum moiety (Al3+), and not exposure to a particular aluminum compound, is the critical parameter for evaluating potential toxicological riskFootnote 1. Second, concentrations of aluminum in foods, soil, drinking water, and air are generally reported as total aluminum, and not in terms of specific salts.

The search strategies employed in the identification of relevant data are presented in Appendix A. All original studies that form the basis for determining whether aluminum salts are "toxic" under CEPA 1999 have been critically evaluated and are described in the assessment. For issues relevant to the environmental and human health effects of aluminum, but outside the scope of the present assessment, the information is summarized briefly and the reader is referred to recent critical reviews published in the scientific literature for a more detailed discussion.

The human health components of the present document were prepared by the Safe Environments Programme- Quebec Region, in collaboration with the Existing Substances Division of the Safe Environments Programme (National Capital Region).  The environmental components were prepared by the Existing Substances Division of the Science and Technology Branch.

The human health components of this assessment have been peer reviewed by the following external experts:

Information relevant to environmental components of this assessment has been reviewed by the following external experts:

While external peer review comments were taken into consideration, the final content and outcome of the risk assessment remain the responsibility of Health Canada and Environment Canada.

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