Ecological risk assessment for the recent case of DDT pollution in Lake Maggiore (Northern Italy)

Contamination by DDT of industrial origin was detected in 1996 in Lake Maggiore (Northern Italy) causing concern for wildlife and human health. Starting from 1998 a monitoring programme involving different research laboratories was undertaken to establish the pollution level of the lake. In assessing the ecological risk to Lake Maggiore wildlife during this period, the present study integrates information provided by the Commission for the Protection of Italian and Swiss Waters with further analysis and ecotoxicological tests carried out on some autochthonous target species for this insecticide. Sediments collected at the end of 1997 in the most contaminated bay (total DDT 860.2 ng g-1 dry weight) caused a decrease in fertility and growth of benthic oligochaetes and chironomids, while the 48 h IC50 for Daphnia galeata (0.76 μg L-1, c.i. 0.43-1.34) was much higher than the DDT concentration in the lake water. The risk of acute effects on zooplankton should therefore be excluded, while transfer through the trophic web and bioconcentration in fish and fish-eating birds are the most adverse consequences of DDT contamination in Lake Maggiore.