The Department of Health has published a notice under the Canadian Environmental Protection Act, 1999 proposing new health-based air quality objectives (HBAQOs) for arsenic. The proposed HBAQOs are non-regulatory health benchmarks designed to represent concentrations of airborne pollutants below which adverse health effects are expected to be minimal. They are developed to reflect both short-term and long-term exposure scenarios and account for variability in susceptibility among populations. These objectives are intended to guide governments and partners in assessing air quality risks, supporting risk management decisions, and improving public communication about environmental health hazards. While not legally binding, they serve as scientifically grounded reference points for managing air pollution and protecting public health.

Arsenic is a naturally occurring element found in the earth’s crust, primarily in inorganic forms. In ambient air, it is most commonly present as inorganic arsenic trioxide particles released through industrial and natural processes. Key sources include mining and smelting operations, energy production, waste incineration, and wildfire events. Exposure risk is higher in communities located near such sources, as well as in areas with elevated natural background levels. The proposed objectives apply specifically to inorganic arsenic expressed as elemental arsenic and exclude organic arsenic compounds and arsine gas.

The proposed health-based air quality objectives include a short-term guideline of 0.2 micrograms per cubic metre over a one-hour averaging period, designed to protect against acute developmental effects observed in fetal development. For long-term exposure, an annual objective ranging from 0.001 to 0.01 micrograms per cubic metre is proposed, corresponding to an estimated incremental lifetime cancer risk between one additional case per million people and one per one hundred thousand people. The document emphasizes that because arsenic is a known carcinogen, no level of exposure is considered entirely risk-free, and concentrations should be kept as low as reasonably achievable.

Short-term exposure to arsenic can cause irritation of the respiratory tract and neurological symptoms such as dizziness and lightheadedness. The most sensitive effects are observed during fetal development, including reduced fetal weight and congenital abnormalities in animal studies, which supports the use of a short averaging period for acute exposure protection. Long-term exposure has been strongly associated with lung and respiratory cancers, based on evidence from occupational studies and animal research. Arsenic is classified as a Group 1 carcinogen by the International Agency for Research on Cancer and is listed as a toxic substance under Canadian environmental legislation.

Emerging research also suggests associations between chronic arsenic exposure and cardiovascular disease, as well as neurological conditions such as peripheral neuropathy. Certain populations face disproportionate exposure risks, particularly those living near industrial sources or in regions with higher natural arsenic levels. These populations may also be exposed through multiple pathways, including ambient air, drinking water, indoor dust, and traditional or country foods, compounding overall exposure.

Canada (Draft) May 26, 2026
Disclaimer: Insights are for informational purposes only and does not reflect RRI’s official position or constitute legal opinion.