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Diuron factsheet

Published in Pesticides News No. 67, March 2005

Diuron is a common ‘booster biocide’ in anti-fouling paints.

“Diuron is a non-selective herbicide mainly used to control weeds on hard surfaces. Its principal breakdown product 3,4-dichloroaniline is more toxic than diuron itself. Two ‘dioxin-like’ compounds are present in diuron preparations as contaminants from the manufacturing process. The United States EPA classifies diuron as a ‘known/likely’ carcinogen. It is persistent and contaminates marine waters, groundwater, sediment and soil.”

“Exposure to sub-lethal doses of diuron causes formation of methaemoglobin, an abnormal form of the protein haemoglobin which carries oxygen in the blood(21). Diuron can decrease the number of red blood cells (RBCs), increase the number of abnormally shaped RBCs, and increase the number of white blood cells. Diuron may cause the spleen to become congested due to the increased demand to remove damaged RBCs. Increases in liver size are also observed and are indicative of the extra load placed on this organ, the body’s major site of detoxification. Diuron can also cause eye and skin irritation.”

“The US Environmental Protection Agency (EPA) has classified diuron as a ‘known/likely’ carcinogen since 1997 based on the results of two studies. One study on rats indicated that both males and females fed diuron had a higher incidence of bladder cancer than control animals. The male rats in this study also had a higher incidence of kidney cancer than the control animals. In a study of mice animals with higher exposures had more breast cancer”

“Diuron’s potential to pollute water is of particular concern. Herbicides used for weed control on hard surfaces are washed down drains into water supplies by rainfall. In addition, diuron in antifouling paint on ships has contributed to contamination of marine and estuarine waters, and of marine sediments. As abiotic breakdown in waters is extremely slow this contamination will likely persist for years despite regulatory action withdrawing antifouling uses of diuron in a number of countries. In the Japanese aquatic environment 86% of tested samples showed a 3.05 μg/litre concentration of diuron(30). In Dutch coastal waters a higher level than the permitted 430 ng/litre was detected(31). According to the French Environmental Institute diuron is detected in 34.6% of surface waters in France where it was the fifth most frequently detected pesticides. It was also found in 6.4% of groundwater samples where it was the seventh most frequently detected pesticide(32). In the UK diuron is consistently one of the pesticides most frequently found exceeding the non-statutory Environmental Quality Standard of 0.1 μg/litre(33). Many other studies have reported contamination of water by diuron in antifouling paint”

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