Creosote a mixture of polycyclic aromatic hydrocarbons (PAH), typicall
y becomes depleted of low molecular weight compounds once in the envir
onment. Previous studies indicated that PAH toxicity increased with in
creasing molecular weight up to phenanthrene: heavier compounds were l
ess toxic than phenanthrene, possibly due to their limited solubility.
A high molecular weight fraction (HMWF) of creosote, with a compositi
on similar to environmentally weathered creosote, and a low molecular
weight fraction (LMWF) were obtained by distillation. Fish were expose
d to suspended sediments contaminated with each fraction for 10 days.
Samples of fish were removed on days 2, 4, 7 and 10, observed for gros
s pathological abnormalities, weighed, measured, and the livers analyz
ed for ethoxyresorufin O-de-ethylase (EROD) activity. Mortality, epide
rmal lesions, fin erosion, and temporary induction of EROD activity oc
curred in fish exposed to the HMWF. No mortality, fin erosion, or indu
ction of EROD activity occurred in fish exposed to the LMWF or unconta
minated sediment. Fish exposed to the LMWF did develop lesions, but on
ly in the area surrounding the mouth, nares, and opercula. These resul
ts suggest that the environmental toxicity of creosote is due to the h
igh molecular weight compounds. Copyright (C) 1996 Elsevier Science Lt
d.