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  • Ontario Air Standards

    For

    Cadmium and Cadmium Compounds

    June 2007

    Standards Development Branch Ontario Ministry of the Environment

    Ontario

  • Ontario Air Standards for Cadmium and Cadmium Compounds

    Executive Summary

    The Ontario Ministry of the Environment (MOE) has identified the need to develop and/or update air quality standards for priority contaminants. The Ministry’s Standards Plan, which was released in October, 1996 and revised in November, 1999, identified candidate substances for which current air quality standards will be reviewed or new standards developed. Cadmium and cadmium compounds were identified as a priority compound for review based on the pattern of use in Ontario and recent toxicological information that was published subsequent to the development of the existing guideline in 1974. Once a decision is made on the air standards, they will be incorporated into Ontario Regulation 419: Air Pollution – Local Air Quality (O. Reg. 419/05). The Ambient Air Quality Criterion (AAQC) will be incorporated into Schedule 3 of the regulation and the half hour standards will be incorporated into Schedule 2. An ‘Information Document’ containing a review of scientific and technical information relevant to setting an air quality standard for cadmium and cadmium compounds was previously posted on the Environmental Bill of Rights Registry for public comments. This was followed more recently by the posting of a document providing the rationale (‘Rationale Document’) for recommending an Ambient Air Quality Criterion (AAQC) and a half hour standard for cadmium and cadmium compounds. This document, referred to as the ‘Decision Document’, summarizes the comments received from stakeholders on the proposed standards and the Ministry responses to these comments. This document also provides the rationale for the decision on the air quality standards for cadmium and cadmium compounds.

    Cadmium is classified as a heavy metal and found widely distributed in the air, soil, and fresh and salt water. It can also be detected in foliage, coal, and petroleum. The most common forms of cadmium are oxide, chloride, and sulfide/sulfate. The most common uses for cadmium include the production of nickel-cadmium rechargeable batteries, paint pigments, and anticorrosive metal coatings. Cadmium is also used in the manufacturing of electronic components and select metal alloys.

    Cadmium releases to the air take place through both natural and anthropogenic processes. Rock erosion, forest fires, and volcanic eruptions release cadmium to the air. Anthropogenic sources of cadmium are largely from the industrial sector such as mining, metal refining, and the combustion of fossil fuels.

    The approximate airborne cadmium levels found in environments free of anthropogenic activity are of the order of 0.1 to 5 nanograms per cubic meter depending on other sources as will be discussed later. In urban environments in Ontario, cadmium levels as high as 3.44 nanograms per cubic meter have been measured.

    i

  • Ontario Air Standards for Cadmium and Cadmium Compounds

    The primary form of cadmium to which the general population in Ontario is expected to be exposed to is cadmium oxide. Therefore, although discussions on toxicity assessment of various species of cadmium are presented, the emphasis in the development of the standard will be cadmium oxide.

    This document reviews the adverse health effects due to cadmium-in-air exposure with an emphasis on the inhalation pathway. Cadmium in particulate matter in the PM10 size range is the most relevant with respect to human health with respect to inhalation. However, cadmium in the larger total suspended particulates (TSP), which easily deposit to soils, is also relevant to other exposure pathways from which cadmium can contribute to the body burden. This is of particular relevance for persistent contaminants like cadmium that can build up in the local environment from emitting facilities. A host of studies published in international journals have identified various human health concerns associated with exposure to air-borne cadmium. Cadmium has been directly associated with kidney damage in mammalian species when the intake occurred via ingestion and inhalation. Chronic exposure to airborne cadmium (inhalable or respirable particles) has been linked to increases in lung cancer and the International Agency for Research on Cancer (IARC) has classified cadmium as a Group 1 carcinogen implicating it as “probably carcinogenic to humans”. However, the World Health Organization (WHO) in its recent reanalysis stated that because of the identified and controversial influence of concomitant exposure to arsenic in the epidemiological study, no reliable unit risk can be derived to estimate the excess lifetime risk for lung cancer.

    The current Ontario 24-hour Ambient Air Quality Criterion (AAQC) for cadmium is 2 μg/m3. The half-hour point of impingement (POI) standard is 5 μg/m3. The basis for both of the criteria, set in 1974, was protection of human health.

    The Ministry of the Environment has reviewed and considered air quality guidelines and standards as well as the derivation approaches used by leading agencies worldwide and advice from Ontario stakeholders. Based on recent evidence and recent reanalysis of studies by the Agency for Toxic Substances and Disease Registry (ATSDR), the World Health Organization (WHO), the European Commission (EC) and stakeholder comments, the Ministry considers the EC’s approach, modified by input from comments received, to be the most appropriate for developing air quality standards. In particular, the non-cancer endpoint of kidney damage, together with the provision of additional protection of human health with respect to carcinogenicity, were considered to provide the most appropriate guideline value on the basis of the studies and plausibility of the mechanisms. Accordingly, the annual cadmium ambient air quality criterion for Ontario is proposed to be 5 ng/m3 of cadmium in total suspended particulates.

    ii

  • Ontario Air Standards for Cadmium and Cadmium Compounds

    Based on an evaluation of the scientific rationale of air guidelines from leading agencies, an examination of current toxicological research, and comments from stakeholders, the following Air Quality Standards are set for cadmium (CAS# 7440-43-9) and cadmium compounds :

    • An annual Ambient Air Quality Criterion (AAQC) of 5 ng/m3 (nanograms per cubic metre of air) for cadmium and cadmium compounds based on kidney effects and carcinogenicity associated with exposure to these compounds ; and

    • A 24-hour average AAQC of 25 ng/m3 (nanograms per cubic metre of air) for cadmium and cadmium compounds based on kidney effects and carcinogenicity associated with exposure to these compounds ; and

    • A half-hour standard of 75 ng/m3 (nanograms per cubic metre of air) for cadmium and cadmium compounds based on the kidney effects and carcinogenicity associated with exposure to these compounds

    These effects-based standards (which include the AAQCs and the corresponding effects-based half hour standards) will be incorporated into Ontario Regulation 419/05: Air Pollution – Local Air Quality (O. Reg. 419/05). The AAQCs (except the annual AAQC) will be incorporated into Schedule 3 of O. Reg. 419/05; the half-hour standard will be incorporated into Schedule 2.

    MOE generally proposes a phase-in for new standards or standards that will be more stringent than the current standard or guideline. The phase-in for cadmium and cadmium compounds is set out in O. Reg. 419/05.

    Among other things, O. Reg. 419/05 sets out the applicability of standards, appropriate averaging times, phase-in periods, types of air dispersion model and when various sectors are to use these models. There are 3 guidelines that support O. Reg. 419/05. These guidelines are:

    • “Guideline for the Implementation of Air Standards in Ontario” (GIASO);

    • Air Dispersion Modelling Guideline for Ontario” (ADMGO); and

    • “Procedure for Preparing an Emission Summary and Dispersion Modelling Report” (ESDM Procedure).

    GIASO outlines a risk-based decision making process to set site specific alternative air standards to deal with implementation barriers (time, technology and economics) associated with the introduction of new/updated/ air standards and new models. The alternative standard setting process is set out in section 32 of O. Reg. 419/05.

    iii

  • Ontario Air Standards for Cadmium and Cadmium Compounds

    For further information on these guidelines and O. Reg. 419/05, please see the Ministry’s website http://www.ontario.ca/environment and follow the links to local air quality.

    iv

    http://www.ontario.ca/environment

  • Ontario Air Standards for Cadmium and Cadmium Compounds

    Table of Contents

    Executive Summary........................................................................................................ i Table of Contents .......................................................................................................... v 1.0 Introduction ......................................................................................................... 1 2.0 General Information............................................................................................ 3

    2.1 Physical and Chemical Properties..................................................................... 3 2.2 Pro