San Francisco Chronicle: A state appeals court has ordered California regulators to re-evaluate a widely used rat-killing chemical, saying the state has approved its continued use for years without assessing its potential harmful effects on other creatures.
The state Department of Pesticide Regulation, whose annual approval is needed to sell pesticides in the state, has approved the rodenticide, diphacinone, without conducting a full re-evaluation of its effects in recent years. Asked in December 2017 by a rodenticide-safety group for a new assessment, the agency refused, saying it had received no evidence that the chemical could be dangerous.
But the First District Court of Appeal in San Francisco said the department had failed to examine the effects of diphacinone when used over long periods or in combination with other rodent-killing chemicals and had wrongly classified it as one of a group of older chemicals that needed less scrutiny.
“The department’s 35-page report contains no discussion of the cumulative impacts resulting from the combination of diphacinone with other rodenticides present in the environment,” Justice Therese Stewart said in a 3-0 ruling last week requiring a reassessment of the product. Among rodenticides on the market, Stewart said, studies show diphacinone is the second-most-toxic to bobcats and other mammals that prey on rats, and it may have more serious effects when interacting with other rodent-killing chemicals. She said it was also the second-most-widely used rodenticide as of 2016.