Assessment of Photochemical Processes in Environmental Risk Assessment of PAHs

Report no. 15/20: Petroleum substances may contain polyaromatic hydrocarbons (PAHs) that can interact with sunlight. These interactions can increase hazard, via photo-enhanced toxicity, and reduce exposure, due to photodegradation. These processes are not considered in the PETRORISK model, developed and used by Concawe for risk assessments of petroleum substances under REACH. To assess the role of photochemical reactions on hazard and exposure and resulting risks to aquatic life, available photodegradation and photoxicity data were used to calibrate hazard and multimedia exposure models for representative 3, 4, and 5-ring PAHs.  These models were then used to calculate risks for a range of sunlight exposures in natural waters.

Risks derived for these scenarios were then compared to the default case without light. Results showed risks with sunlight were similar to or lower than the no light scenario since the predicted enhancement in toxicity was mitigated by reduced exposure from photodegradation. Study findings indicate that neglecting light interactions in petroleum substance risk assessments do not preclude effective chemical management since risks are not increased.