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The Ministers of Environment and Health have released for final publication the assessment report for the priority substance acrolein. Notice concerning the assessment of this substance and a summary of its assessment report was published in the Canada Gazette, Part 1 May 27, 2000. The synopsis of the report is provided below.

A draft of this Assessment Report was made available for a 60-day public comment period (May 1, 1999 - June 29, 1999). Following consideration of the comments received, the Assessment Report was revised as appropriate. A summary of the comments and their responses may also be accessed from this page.

For paper copies of the Full Assessment Report, please contact the Inquiry Centre at Environment Canada:

To obtain an electronic version of the Assessment Report in PDF, please request a copy from the following address: ESB.DSE@ec.gc.ca

Synopsis

Acrolein is not commercially produced in Canada. It is imported from the United States for use mainly as an aquatic herbicide in irrigation canals and as a microbiocide in produced water during oil explorations. These uses are regulated under the Pest Control Products Act and Regulations. An estimated minimum of 218 tonnes of acrolein is released yearly to the atmosphere from anthropogenic sources involving the combustion of organic matter (i.e., predominantly as a component of vehicle exhaust) or the forest industry. Unquantified amounts are also released from natural sources and the photooxidation of organic pollutants in air. No releases of "non-pesticidal" acrolein to water, sediments or soils in Canada have been identified.

Acrolein is unlikely to be transported over long distances because of its high reactivity and estimated short half-lives in air and water. It is also unlikely to partition from these compartments to soil or sediments. Acrolein is rapidly metabolized by organisms and does not bioaccumulate. The highest environmental concentrations of acrolein not directly released during its application as a pesticide in Canada have been measured in air from urban areas. With the exception of samples taken in the vicinity of pesticidal application, acrolein has not been detected in water, sediment or soil in Canada.

Acute and chronic data on toxicity are available for aquatic organisms and laboratory animals. Only acute data were identified for terrestrial crop plants. Terrestrial organisms appear less sensitive to acrolein than aquatic organisms. Known concentrations of acrolein in the Canadian atmosphere are less than the threshold for adverse effects estimated for terrestrial organisms. Exposure of other organisms to non-pesticidal acrolein is considered unlikely, since no sources or detectable concentrations of acrolein have been identified in other compartments. Acrolein is not involved in stratospheric ozone depletion and is not an important contributor to climate change or photochemical smog formation.

Based upon studies conducted primarily with laboratory animals, adverse health effects associated with exposure to acrolein are mostly confined to the tissue of first contact (i.e., the respiratory and gastrointestinal tracts after inhalation and ingestion, respectively) and are concentration related. Hence, for comparison with Tolerable Concentrations for both inhalation and ingestion, exposures via these routes have been assessed separately. Tolerable Concentrations are the concentrations to which it is believed that a person may be exposed continuously without deleterious effect.

Available information is considered insufficient to characterize exposure of Canadians to acrolein via ingestion. However, the range of concentrations measured in food in other countries (although highly dependent upon such factors as method of cooking) is within the range of a provisional Tolerable Concentration for ingestion that is protective for site-of-contact effects.

Probabilistic estimates of the distribution of time-weighted 24-hour concentrations of acrolein in air indicate that between 5% and 10% of the general population would be expected to be exposed to at least 5 mg/m3. This is greater than the Tolerable Concentration for inhalation derived on the basis of site-of-contact effects in animal species.

Based on the information available, it is concluded that acrolein is not entering the environment in a quantity or concentration or under conditions that have or that may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends. It is concluded that acrolein is entering the environment in a quantity or concentration or under conditions that constitute a danger in Canada to human life or health. Therefore, acrolein is considered to be "toxic" as defined in Section 64 of the Canadian Environmental Protection Act, 1999 (CEPA 1999).

Indoor air is an important source of exposure, although the relative contribution of various sources therein is unknown. Better characterization of the significance of sources in indoor air and investigation of the potential to reduce emissions or exposure are also desirable.

While for the general population, the contribution of ambient air to overall exposure to inhaled acrolein is expected to be small, compared with the contribution from indoor air, ambient air may be an important source of exposure via inhalation for populations residing in the vicinity of locations heavily impacted by vehicular exhaust. Additional characterization of the contribution of motor vehicle exhaust to air in Canada and investigation of the potential to reduce emissions from this source are also recommended.

In view of the sensitivity of some aquatic organisms, it is also recommended that the use of acrolein to control aquatic weeds be reviewed by appropriate authorities under the Pest Control Products Act in light of this assessment and other relevant considerations.