The toxicity of tecnazene, a potato sprouting inhibitor, to freshwater fauna

Tecnazene, 2,3,5,6-tetrachloronitrobenzene, a sprouting inhibitor and fungicide used on stored potatoes, has been found to enter the freshwater environment at specific sites in the United Kingdom due to the practice of bulk washing potatoes for supermarket presentation. Because of the paucity of toxicity data for aquatic organisms, the acute toxicity of tecnazene was determined for 7 freshwater species (3 fish, 2 crustaceans, 1 mollusc and 1 insect). A 28-day fish growth test and bioconcentration study were also conducted. Tecnazene is highly toxic to the aquatic species tested, with 96 h LC50 values ranging from 270 to 2340 μg 1−1; adverse effects on fish growth rates were found above 7.5 μg 1−1. Mean bioconcentration factors of between 2390 and 5170 were found after 28 days' exposure although the accumulated tecnazene depurated rapidly. A limited field investigation in the potato growing region of the Lincolnshire Fens, UK, revealed no traces of tecnazene in fish samples but concentrations of tecnazene and one of its breakdown products, 2,3,5,6-tetrachloroaniline, were detected in water at 18 and 5 μg 1−1 respectively, immediately downstream of one potato washing plant. Sporadic washing activity probably affected the frequency of occurrence of tecnazene.