Priority Substances List Assessment Report for Aluminum Chloride, Aluminum Nitrate, Aluminum Sulphate

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.

Based on initial screening of readily accessible information, the rationale for including aluminum chloride, aluminum nitrate and aluminum sulfate provided by the Ministers' Expert Advisory Panel on the Second Priority Substances List (Ministers' Expert Advisory Panel, 1995) was as follows:

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.

Since it is the dissolved aluminum species formed when these compounds dissociate, and not the compounds themselves, that are bioavailable and can adversely affect organisms, the environmental part of this report examines risks associated with exposures to dissolved forms of aluminum associated with the use of these aluminum salts. In relation to human health, consideration of individual aluminum compounds is precluded, due to lack of information on species of aluminum to which the general population is exposed in the general environment.

The search strategies employed in the identification of data relevant to characterization of potential effects on the environment (prior to January 1999) and human health (prior to January 2000) are presented in Appendix A. Review articles were consulted where appropriate. All original studies that form the basis for assessing the environmental exposure and effects of aluminum chloride, aluminum nitrate and aluminum sulfate have been critically evaluated by staff of Environment Canada.

Preparation of the environmental components of the characterization was led by A. Gosselin of Environment Canada. Sections of the Report and the supporting documentation related to the environmental characterization of aluminum chloride, aluminum nitrate and aluminum sulfate (Bélanger et al., 1999; Germain et al., 1999; Roy, 1999a) were prepared or reviewed by the members of the Environmental Resource Group, established by Environment Canada to support the environmental part of this report:

P. Doyle, Environment Canada
C. Gagnon, Environment Canada
R.G. Garrett, Geological Survey of Canada
A. Germain, Environment Canada
A. Gosselin, Environment Canada
W.H. Hendershot, McGill University C.B. Lind, General Chemical Corporation
R. Roy, Fisheries and Oceans Canada (formerly from E.S.G. International)
P. Thompson, Environment Canada

Environmental sections of the supporting documentation were also reviewed by:

C. Cronan, University of Maine
L. Curtis, Oregon State University
D.S. Jeffries, National Water Research Institute
R. Lapointe, Société d'électrolyse et de chimie Alcan Ltée
C. Neville, Ontario Ministry of the Environment
J.  Smith, National Water Research Institute
W. Wagner, Natural Resources Canada

The sections of this report related to characterization of environmental effects were reviewed by members of the Environmental Resource Group as well as by:

J. Brown, Reynolds Metals Company
S. Brown, National Water Research Institute
C. Cronan, University of Maine
L. Curtis, Oregon State University
R. Lapointe, Société d'électrolyse et de chimie Alcan Ltée
S. McFadien, Canadian Water and Wastewater Association
W. Wagner, Natural Resources Canada

The health-related sections of this Report build on several previous initiatives of Health Canada related to aluminum in drinking water. Aluminum has been considered recently by the Federal-Provincial Subcommittee on Drinking Water in its continuing revision of the "Guidelines for Canadian Drinking Water Quality." Following a review of the relevant information, the Subcommittee concluded that the available data were inadequate as a basis for development of a health-based guideline for aluminum in drinking water (Health Canada, 1998).

To address the inadequacy of data for developing a health-based drinking water guideline, Health Canada convened an international workshop on September 3-4, 1997, to investigate the feasibility of conducting further study of the potential critical endpoint - i.e., neurotoxicity (Health Canada, 1997). The workshop, from which there were several recommendations for relevant further study, was co-sponsored by the Office of Water of the U.S. Environmental Protection Agency (EPA). The following experts participated:

K. Bailey, Water Research Centre
T.P. Flaten, Norwegian University of Science and Technology
W.F. Forbes, University of Ottawa
M.J. Gardner, Water Research Centre
M.S. Golub, University of California
S. Gupta, Health Canada (Scientific Coordinator)
A. Mahfouz, U.S. EPA
D.R.C. McLachlan (retired from University of Toronto)
D. Rice, Health Canada
D.J. Savory, University of Virginia
B.H. Thomas, Health Canada (Chair)
J. Walton, Australian Institute for Biomedical Research Ltd.
R.A. Yokel, University of Kentucky

As follow-up to the workshop, Health Canada established an Expert Steering Committee on Aluminum and Animal Neurotoxicity to develop a Request for Proposals (RFP) for a study or studies on the neurotoxicity of aluminum as a basis for risk assessment by both Health Canada and the U.S. EPA.

The first meeting of the Steering Committee was held in Montréal, Quebec, on May 30-31, 1999. Participants included the following:

I. Arnold, Alcan Aluminum Ltd.
P. Campbell, Université du Québec
H. Durham, McGill University
D. Krewski, University of Ottawa
J. Lindsay, Health Canada
P. Mouton, Johns Hopkins University
E. Ohanian, U.S. EPA
G. Plaa, Université de Montréal (Chair)
B.H. Thomas, Health Canada

The Steering Committee developed study designs for multigeneration studies in mice to further investigate the biological plausibility of purported associations between aluminum and Alzheimer's disease.

In relation to toxicity, this report addresses only potentially critical (i.e., neurological) effects in humans and supporting evidence. Available data to serve as a basis for characterization of the potential of aluminum to induce effects other than those on the neurological system, such as carcinogenicity, genotoxicity and reproductive, developmental and other systemic or organ system effects, are limited. Indeed, there are few experimental studies conducted to recent standards by relevant routes of exposure in which the effects of a range of doses have been examined, with adequate account of dietary exposure. Based on the limited available data, effects observed consistently at lowest doses in experimental animals are those on the neurological system, specifically neurobehavioural effects in offspring exposed during development and tested as adults or in exposed adults. Aluminum has also been implicated in the induction of several neurological disorders in humans.

In this report, the weight of evidence for these potentially critical neurological effects is considered, therefore, primarily as a basis for delineation of the above-mentioned research plan. Potential exposure of the general population is also addressed primarily to provide perspective on the principal sources and media of exposure and potential bioavailability therefrom. The extent of primary review of relevant information and level of documentation included herein reflect the limited scope and objectives of this report, which builds upon previous initiatives by Health Canada.

The health-related sections on toxicity of this report are based, in part, on the deliberations of a Task Group on Aluminum of the International Programme on Chemical Safety in which staff of Health Canada participated (WHO, 1997) and updates in critical areas, as identified below.

A critical review of the epidemiological data relevant to the characterization of the weight of evidence for neurotoxicity of aluminum was prepared by A. Smargiassi, Université du Québec à Montréal, and subsequently reviewed by:

J. Lindsay, Laboratory Centre for Disease Control, Health Canada
C. Martyn, University of Southhampton
L. Smith, Ontario Ministry of Health and Long-term Care

A critical review of data relevant to the characterization of the potential mode of the neurotoxicity of aluminum was prepared by J. Savory, University of Virginia, and subsequently reviewed by:

P.R. Mouton, Johns Hopkins School of Medicine
M. Strong, University of Western Ontario
T. Wisniewski, New York University School of Medicine

A critical review of the available data on the bioavailability of aluminum was prepared by R.A. Yokel and P.J. McNamara, University of Kentucky, and subsequently reviewed by:

M.J. Gardner, Water Research Centre
E. Nieboer, McMaster University
N. Priest, Middlesex University

The health-related sections of this State of the Science Report were prepared by the following staff of Health Canada:

M.E. Meek
J. Paterson

The health-related sections of this Report were reviewed by H. Durham, McGill University and J. Lindsay, Laboratory Centre for Disease Control, Health Canada and approved by the Health Protection Branch Risk Management meeting.

The entire State of the ScienceReport was reviewed and approved by the Environment Canada/Health Canada CEPA Management Committee.

The text of the Report has been structured to address environmental effects initially, followed by effects on human health.