For the second time in two years, residues of clopyralid were found in two compost facilities in Washington, according to the Pesticide Action Network Updates Services. Clopyralid is the active ingredient in Confront, and is a persistent herbicide that breaks down extremely slowly, especially in composting. This chemical was also recently found contaminating compost in Pennsylvania and New Zealand.
Both purchasers of the compost and the facilities themselves suffer the consequences. Clopyralid's persistence, mobility in soil and water solubility allow it seriously damage plants. Clopyralid is toxic to sunflowers, tomatoes, potatoes and legumes at levels of 10 parts per billion (ppb). Residue testing of compost at the facilities revealed clopyralid levels between 73 and 80 ppb. These levels have the potential to damage crops, gardens and nurseries. The resulting occurrence of revenue losses, claim settlements, testing and additional labor cost one facility at the University of Washington $250,000.
Actions have been taken to ameliorate the problem. Washington State University is requiring vendors of straw and hay to be used in compost to guarantee their product is pesticide-free. Spokane, Washington began a campaign to educate the public concerning the importance of pesticide-free compost. Public utilities in Oregon and Washington asked EPA to require that there be no residual herbicides in compost after a 60 - 90 day cycle. They also stressed that the manufacturer of the herbicide should be responsible for any detected residues, and not the composting facility.
In addition, the U.S. Composting Council is asking Dow AgroSciences, the manufacturer of Confront, to buy the contaminated compost and compensate for all losses.