Synopsis
Ethylene glycol was included on the Priority Substances List (PSL) under the Canadian Environmental Protection Act (CEPA) to assess the potential environmental and human health risks posed by the exposure to ethylene glycol in consumer products and the environment.
In December 2000, the second Priority Substances List (PSL2) assessment of ethylene glycol was formally suspended due to the uncertainties associated with the human effect and exposure data set. At the same time, a state of the science report (Environment Canada and Health Canada 2000) on ethylene glycol was released, providing an in depth review of the toxicity and exposure information related to human health and the environment. The essential information needed to complete the PSL2 assessment was identified and acquired during the subsequent seven years.
Ethylene glycol is primarily used as a component of de-icer and anti-icer/antifreeze fluid used in aircraft de-icing and anti-icing operations, and as an anti-freeze component in motor vehicles. It is also used in manufacturing polyester products. Ethylene glycol is present as a slow-evaporating solvent and/or freeze-thaw stabilizer in latex paints. Ethylene glycol can also be used in a variety of other products such as floor and wall adhesives, brake fluid, automotive wax/polish and floor wax/polish. In 2001, approximately 1440 kt of ethylene glycol were manufactured in Canada by three companies in Alberta. Most Canadian glycol production is destined for export.
With regard to the environment, 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. However, in recent years, management practices at Canada’s major airports have improved with the installation of new ethylene glycol application and mitigation facilities or improvements to existing ones.
The direct comparison of exposure concentrations measured in the aquatic environment with the estimated no-effect values (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. Furthermore, examination of potential indirect effects through oxygen depletion suggests a low potential for concentrations of dissolved oxygen (DO) to drop to levels of concern. As such, it is proposed that ethylene glycol is not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity, or that constitutes, or may constitute a danger to the environment on which life depends.
With regard to human health, upper-bounding estimates of daily intake of ethylene glycol by the general population of Canada, and by a highly exposed population in the immediate vicinity of an industrial point source, are well below tolerable intake (TI), derived based on a Benchmark Dose calculated for non-neoplastic renal effects in animals and an uncertainty factor. "Tolerable intake" is the level of intake to which it is believed a person may be exposed daily over a lifetime without deleterious effect. However, conservative estimates of short-term indoor air concentrations that individuals, including children, may be exposed to from use of certain consumer products containing this substance (latex paint), exceeds the Tolerable Concentration (the concentration to which it is believed a person may be exposed without deleterious effect) considered appropriate for short-term exposures. The Tolerable Concentration was based on a no-observed-adverse-effect-level for developmental effects in animals and an uncertainty factor. Given the uncertainties in estimates of short-term concentrations that individuals, including children, may be exposed to, and the nature of the health effect, it is considered appropriate to apply precaution when characterizing risk. It is proposed, therefore, that ethylene glycol is entering the environment in a quantity or concentration or under conditions that may constitute a danger to human life or health.
Based on the information available for human health and the environment, it is thus proposed that ethylene glycol be considered "toxic" as defined in section 64 of the Canadian Environmental Protection Act, 1999 (CEPA 1999).
Additional characterization of the range and distribution of concentrations of ethylene glycol in certain consumer products (latex paint) currently available in Canada, as well as human exposure (inhalation, dermal contact) to ethylene glycol from use of these consumer products is considered a priority for risk management. Furthermore, information to reduce uncertainty regarding absorption of ethylene glycol through the skin from use of consumer products containing this substance would be valuable. Further information on interspecies and intraspecies toxicokinetics and toxicodynamics would be useful in determining whether data-derived values could replace components of the interspecies and intraspecies uncertainty factors.