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A Draft Report has been completed for ethylene glycol. With respect to human health, owing to the considerable limitations of the available data on both exposure and effects of ethylene glycol, a definitive conclusion of "toxic" or not "toxic" could not be reached. Therefore, the five year timeframe mandated within the CEPA 1999 for assessment of Priority Substances is suspended for a period of five years to collect necessary data on:

• Range and distribution of concentrations of ethylene glycol in currently available consumer products in Canada;
  
  
• Monitoring information on concentrations of ethylene glycol in the vicinity of industrial point sources; and
  
  
• Information on progression of ethylene glycol induced renal lesions in the likely most sensitive strain of rat.
  
  

Notice concerning the suspension of this substance has been published in the Canada Gazette, Part 1 on December 2, 2000.

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

Ethylene glycol (CAS No. 107-21-1) is a colourless, odourless, relatively non-volatile liquid. It has a low vapour pressure and is completely miscible in water.

Ethylene glycols (mono-, di- and tri-) are produced by three companies in Canada, which had a total annual capacity of 850 kilotonnes in 1996. Ethylene glycol is used primarily as an antifreeze agent but is also used, for example, in the manufacture of polyethylene terephthalate, in natural gas processing and as a component of paints. Natural levels of ethylene glycol are considered to be insignificant relative to amounts released from anthropogenic sources. The highest reported releases of ethylene glycol to the environment are to land from aircraft deicing/anti-icing operations, with subsequent release to the aquatic environment. Current management practices at the major airports in Canada have resulted in a trend of decreased releases in recent years. Other sources of releases to water include paper products and steel industries. Releases to air occur during ethylene glycol production, during natural gas processing and from paints and coatings manufacture. Ethylene glycol is also injected underground as a means of disposal from natural gas processing operations.

Once released into the environment, ethylene glycol partitions mainly into surface water or groundwater. It does not bioaccumulate or persist in the environment, primarily due to biodegradation. Half-lives in air, water, groundwater and soil are estimated to typically range from 0.35 to 3.5 days, from 2 to 12 days, from 4 to 24 days, and from 2 to 12 days, respectively, but may exceed these ranges, depending on the environmental conditions. Ethylene glycol is not expected to deplete the ozone layer, it has a low potential to contribute to ground-level ozone formation, and its potential contribution to climate change is negligible. Ethylene glycol has been found to biodegrade rapidly in the aquatic environment and therefore has the potential to induce depletion of the dissolved oxygen (DO) in receiving waters.

Given that ethylene glycol tends to partition to the aquatic environment, with little transfer to soil or air expected, and because the majority of ethylene glycol is released to the aquatic environment from aircraft deicing and anti-icing, the potential for effects is greatest for aquatic organisms. In assessing the risk, consideration is given to the time and frequency of exposure. From the available studies, the induction of effects on algae and amphibians is selected to represent the most sensitive measurement endpoints for inducing potential population-level impacts on aquatic organisms and is used as a basis for generating the Estimated No-Effects Values (ENEVs). Indirect effects from oxygen depletion following ethylene glycol release was also examined using the Streeter-Phelps oxygen sag model and probabilistic analysis.

The direct comparison of current exposure concentrations predicted to occur in the aquatic environment with the ENEVs suggests that adverse effects are unlikely when consideration is given to the seasonal nature of releases, ambient temperatures, metabolic rates and duration of exposure. Examination of potential indirect effects through oxygen depletion suggests a low potential for DO levels to drop below the Canadian water quality guideline (9.5 mg/L) under very infrequent, maximal loading conditions. However, under the vast majority of release conditions, adverse impacts are not expected. If the current Canadian Environmental Protection Act, 1999 (CEPA 1999) effluent guideline of 100 mg total glycol/L, applicable to releases from airports on federally owned lands, is maintained, adverse effects from direct and indirect exposure are not expected.

Monitoring data upon which to base estimates of exposure of the general population in Canada to ethylene glycol were not identified. Population exposure estimates are, therefore, extremely limited. Intakes in air and soil in the vicinity of a point source were estimated based on modelled data, and that in food was based on reported concentrations in a limited range of foodstuffs from other countries. Dermal absorption was also estimated for a limited range of products for which data on the proportion of ethylene glycol in the product were identified.

Based on short-term and long-term studies conducted by the oral route in experimental animals, the kidney is the principal target site for effects of ethylene glycol. Consistently, degenerative non-neoplastic changes in the kidney have been observed at lowest doses in a range of species. Based on an extensive database, ethylene glycol induces slight reproductive effects and developmental toxicity, including teratogenicity, in rodents exposed by the oral route, although at doses greater than those associated with renal effects.

Therefore, a Tolerable Intake has been derived for this substance, based on a Benchmark Dose calculated for non-neoplastic renal effects in animals and an uncertainty factor. Based on uncertain estimates, exposure of some age groups in the vicinity of a point source or of adults through absorption from some consumer products exceeds the Tolerable Intake. A Tolerable Intake is the level of intake to which it is believed a person may be exposed daily over a lifetime without deleterious effect.