Priority Substances List Assessment Report for Di-n-Octyl Phthalate

3.0 Assessment of "Toxic" Under CEPA

3.1 CEPA 11(a) Environment

There are no Canadian producers of DnOP. Approximately one tonne of this substance is used annually in Canada. Di-n-octyl phthalate has been detected occasionally in industrial effluents and in sewage sludges in Canada and less frequently in surface waters and sediments. No data were identified on concentrations of DnOP in air, soil, or precipitation in Canada.

The lowest reported LOEL for dissolved DnOP on freshwater aquatic organisms was 1 mg/L (exposure for 16 days reduced the number of young per adult by 75% in Daphnia magna). This effect level was divided by a net factor of 30 (10 to account for differences in sensitivity between species and to extrapolate from laboratory to field conditions, and 3 because of the large reduction in reproduction associated with the LOEL), resulting in an estimated effects threshold of 33 ìg/L. The highest concentration of DnOP reported for Canadian surface waters (7 ìg/L) is about five times less than this estimated effects threshold.

No data were identified to serve as a basis for comparison of an estimated effects level with environmental levels in Canadian sediments, the only other medium in which DnOP has been detected. Similarly, no information pertaining to adverse effects of DnOP on plants, birds, or wild mammals has been identified in the literature. However, on the basis of its very limited use in Canada, exposure of these organisms to DnOP is unlikely to result in harmful effects.

Therefore, based on available data, DnOP is not considered to be entering the environment in a quantity or concentration or under conditions that are having a harmful effect on the environment.

3.2 CEPA 11(b) Environment on Which Human Life Depends

There are no data available concerning the concentration of DnOP in the atmosphere in Canada. However, based on its limited use in Canada and its rapid removal from the atmosphere by photo-oxidation (half-life of less than 2 days), concentrations in the atmosphere are likely to be small. Consequently, DnOP is not expected to contribute significantly to formation of ground-level ozone, global warming, or depletion of stratospheric ozone.

Therefore, based on available data, DnOP is not considered to be entering the environment in a quantity or concentration or under conditions that constitute a danger to the environment upon which human life depends.

3.3 CEPA 11(c) Human Life or Health

Available data are few and unreliable on concentrations of DnOP in environmental media to which humans are exposed in Canada and elsewhere. Consequently, the available information is inadequate for quantitative estimation of the exposure of the general population in Canada to DnOP.

Available data on the toxicity of DnOP are also limited. Reports on effects in humans are limited to a small number of poorly documented studies of small groups of workers exposed in the occupational environment to other phthalates and unspecified isomers of dioctyl phthalate.

Available data are inadequate to assess the carcinogenicity of DnOP in experimental animals owing to incomplete documentation and examination of a limited range of endpoints in identified studies (Carter et al., 1989; DeAngelo et al., 1986; DeAngelo, 1992; Pieckacz, 1971). There has been no convincing evidence of the genotoxicity of DnOP based on the results of a small number of investigations in in vitro bioassays of mutagenicity or DNA repair in bacteria or mutagenicity of a mixture of dialkyl phthalates in cultured mouse lymphoma cells.

Di-n-octyl phthalate has been classified, therefore, in Group V ("Inadequate Data for Evaluation") of the classification scheme developed for use in the derivation of the "Guidelines for Canadian Drinking Water Quality" (Health and Welfare Canada, 1989). For compounds classified in Group V, a Tolerable Daily Intake (TDI) is derived on the basis of division of a no- or lowest-observed-(adverse)-effect-level [NO(A)EL or LO(A)EL] in animal species by an uncertainty factor.

Identified information on the subchronic toxicity of DnOP is restricted to an incomplete report of a study in which male rats were exposed to two doses (and controls) of DnOP in their diet for 11 weeks (DeAngelo et al., 1988) for which additional documentation is not available (DeAngelo, 1992); an inadequately documented study in which small groups of mice were exposed to an unspecified concentration of DnOP in air for up to 16 weeks (Lawrence et al., 1975); and investigations of a limited range of effects following exposure by routes not similar to those by which humans are principally exposed in the general environment (intraperitoneal injection of DnOP to an unspecified strain of rats - Khanna et al., 1990).

Though a well conducted and documented two generation reproduction study in mice has been identified (Heindel et al., 1989; Morrissey et al., 1989), it was considered to be inadequate to serve as a basis for the development of a TDI since effects (e.g., histopathological changes), other than those on reproductive indices, were not examined. Similarly, a 90-day study has also been identified on the immunological effects of DnOP in mice administered for 45 or 90 days by a route to which man is not exposed in the general environment (i.p.) (Oishi, 1990); however, endpoints relevant to assessment of general systemic toxicity were not examined.

Available data are considered inadequate, therefore, to develop a tolerable daily intake for DnOP. Consequently, it is not possible to evaluate whether current concentrations of DnOP present in the environment constitute a danger in Canada to human life or health.

Therefore, based on available data, there is insufficient information to conclude whether DnOP is entering the environment in a quantity or concentration or under conditions that constitute a danger to human life or health.

3.4 Conclusion

Based on these considerations, it has been concluded that DnOP is not entering the environment in a quantity or concentration or under conditions that are having a harmful effect on the environment or that constitute a danger to the environment upon which human life depends. There are insufficient data to determine whether DnOP is entering the environment in a quantity or concentration or under conditions that constitute a danger to human life or health.