The Ministers of Environment and Health have released for final publication the assessment report for the priority substance acetaldehyde. 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 (August 14, 1999 - October 13, 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

In Canada, the major use of acetaldehyde is in the production of pentaerythritol for use in alkyd resin production, fatty acid esters (synthetic lubricants), rosin and tall oil esters, and other smaller-volume applications. The Canadian domestic demand for acetaldehyde was under 10 000 tonnes in 1996.

Acetaldehyde enters the Canadian environment from natural sources (including forest and brush fires), from human sources such as fuel combustion and industrial on-site releases, and through secondary formation as a result of the atmospheric oxidation of natural and anthropogenic organic compounds. Although there are no quantitative estimates of releases from natural and secondary sources in Canada, it is believed that these sources are very large. However, the highest concentrations measured in the environment are present near anthropogenic sources. On-road motor vehicles are the largest human source of acetaldehyde emissions to the Canadian environment, releasing about 3290 tonnes per year into the air. The amount of acetaldehyde estimated to have been released into the Canadian environment from industrial processes in 1996 was 478 tonnes.

When acetaldehyde is released to or formed in air, most will undergo various degradation processes in air, and a very small amount will move into water. When acetaldehyde is released into water, it degrades there and does not move into other media. Acetaldehyde does not persist in the environment, but its continuous release and formation result in chronic exposure of biota near sources of release or formation.

Extensive recent data are available on concentrations of acetaldehyde in urban, suburban and rural air in Canada, and data are available on concentrations in air at the largest industrial emitter of acetaldehyde in Canada. Limited data are available on concentrations in surface water in four rivers and in groundwater at the industrial site that is the largest single emitter of acetaldehyde. Environmental toxicity data are available for a range of terrestrial and aquatic organisms, although mostly only for acute exposure. Based on the highest concentrations measured in air and in surface water and groundwater in Canada and on the Estimated No-Effects Values derived from experimental data for terrestrial and aquatic biota, it is unlikely that organisms are exposed to harmful levels of acetaldehyde in the Canadian ambient environment.

Acetaldehyde is not involved in the depletion of stratospheric ozone or in climate change. Because of its photo-reactivity and its moderate concentrations in the air in Canadian cities, acetaldehyde plays a role, along with other reactive volatile organic chemicals in air, in the photochemical formation of ground-level ozone.

The focus of the human health assessment is airborne exposure. Based on short-term and long-term inhalation studies conducted in experimental animals, the upper respiratory tract is the principal target site for effects of inhaled acetaldehyde. In short-term studies, acetaldehyde causes degenerative non-neoplastic effects. Although it is genotoxic both in vitro and in vivo, tumours have been observed following inhalation only at concentrations that have produced significant cytotoxicity, and it is likely that both the genotoxicity and irritancy of acetaldehyde play a role in its carcinogenicity.

Therefore, a Tolerable Concentration (based on a benchmark concentration or an effect level) and a Tumorigenic Concentration have been derived for this substance.

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

Since acetaldehyde contributes to the formation of ground-level ozone, it is recommended that key sources of acetaldehyde be addressed as part of management plans for volatile organic chemicals associated with the formation of ground-level ozone.

Based on the comparison of the carcinogenic potency of acetaldehyde with estimates of population exposure, the priority for investigation of options to reduce exposure of the general population in the ambient environment is considered to be moderate only. Additional work on characterization of exposure of populations in the vicinity of industrial point sources and of sources in indoor air may be warranted.