Several research and development needs were identified during the preparation of this document:
1. Several high molecular weight PAHs have been shown to be mutagenic, carcinogenic, and inducers of tumors in laboratory animals exposed to high doses. Whether such conditions will also occur at low exposure levels (i.e., equivalent to those one may be exposed to in the environment), can not be determined from the current literature. More work is needed on low level effects of PAHs on animals, including humans.
2. Several PAHs have been shown to be phototoxic when aquatic organisms contaminated with the organic compounds are exposed to solar ultraviolet radiation. The photo-induced toxicity of the PAHs occurs at much lower concentrations than the laboratory chronic tests (generally performed in the absence of ultraviolet radiation) might suggest. Research is needed to identify the existence, and to assess the impact, of photo-induced toxicity in natural aquatic environments. Confirmation is also required regarding photo-induced toxic reactions of those PAHs which have been designated to be phototoxic based on empirical modelling techniques, but have not been tested in the laboratory or in the field.
3. The data on long-term effects (both phototoxic and non-phototoxic) on freshwater and marine organisms exposed to waters and sediments contaminated with PAHs are lacking in the literature. As a result, water quality or sediment quality criteria for several PAHs could not be recommended in this document, while for other PAHs the recommended criteria are interim. The lack of data on effects of PAHs on the other water uses (e.g., irrigation, livestock watering, wildlife, and contact recreation) was also recognized.
4. Field measurements have linked chronic effects (e.g., carcinogenic, mutagenic, and tumor induction, etc.) suffered by aquatic organisms to PAHs found in the environment (e.g., sediments). Despite such associations, definitive information does not exist about which environmental chemicals or group of chemicals may be responsible for the observed effects. Clearly, PAHs and other environmental chemicals may not act individually, but through synergistic-antagonistic interactions. Interactions among PAHs and other equally toxic contaminants such as PCBs need to be addressed to develop definitive (not interim) criteria for PAHs.
5. Data on ambient PAH concentrations in British Columbia waters are non-existent. Good water quality data are required to assess the state of the environment in British Columbia with respects to PAHs.
6. Minimum detectable concentrations need to be improved for some PAHs as indicated in section 6.11.3.