Toxic equivalency factors/quotients (TEF/TEQs) express the toxicity of complex mixtures. For PAHs, TEF
values are available for assessing their carcinogenic potential and are expressed as benzo[a]pyrene
equivalents. This study develops a similar approach for their acute toxicity in sediments. Acute toxicity
(10 day EC50) values were generated using the marine amphipod Corophium volutator bioassay for
twelve low molecular weight PAHs. The results ranged from 24 to 41000 mg/Kg sediment dry weight
for 4-methyldibenzothiophene and anthracene, respectively. Phenanthrene was used as the reference
compound (TEF¼1) and so the TEQ values derived are expressed as phenanthrene equivalents. In order
to illustrate the applicability of this approach to the development of marine indicators we plotted TEQ
values for acute toxicity to UK environmental monitoring data. Further work is required to validate the
TEF values produced and to extend the TEQ approach to include a wider range of low molecular
weight PAHs.