Toxicological assessment of crude oil, oil spill dispersant, and dispersed oil

The toxicities of crude oil and crude oil plus dispersant Water Accommodated Fractions (WAFs) were evaluated in three toxicity testing systems: spiked and continuous exposures to Mysidopsis bahia were tested in flow-through and static testing systems respectively; microbial toxicity was tested with Microbics Microtox{dollar}spcircler{dollar}. Flourometry and HPLC were used to quantitate WAF concentrations of PAHs and BTEX respectively. The mechanically dispersed WAFs spiked exposure test resulted in a median lethal crude oil loading (LL50) = 3914 mg/L compared to a LL50 = 2766 mg/L for the continuous exposure assay. This data suggest that spiked exposures require higher WAF concentrations to achieve toxic responses similar to those due to continuous exposures. PAH data showed some correlation to aquatic toxicity data, while BTEX data showed no correlation. Microtox{dollar}spcircler{dollar} and fluorescence data revealed that chemically dispersed WAF EC50s were 2 to 29 greater than the mechanically dispersed WAF EC50s. This suggests that the chemically dispersed WAFs have a lower percentage of toxic components per unit concentration that the mechanically dispersed WAFs. No significant toxicity variance was observed between the two aquatic test systems and the microbial assay.