EU Warns of Potential Insecticide Health Risk

The warning is the latest blow to a relatively new group of insecticides, called neonicotinoids, which have become widely used in recent years because the chemicals were believed to be safer than older alternatives.

One of the products, imidacloprid—made primarily by chemical company Bayer AG —is among the world's top-selling insecticides. But this year, the EU banned many uses of imidacloprid and two other neonicotinoids for two years because of concerns that they are contributing to mass deaths of honey bees.

The assessment released Tuesday by the European Food Safety Authority(EFSA) applies to imidacloprid and acetamiprid, which is produced by the Japanese company Nippon Soda Co. and sold in numerous products.

An EFSA scientific panel "found that acetamiprid and imidacloprid may adversely affect the development of neurons and brain structures associated with functions such as learning and memory," the agency said Tuesday.

"It concluded that some current guidance levels for acceptable exposure to acetamiprid and imidacloprid may not be protective enough to safeguard against developmental neurotoxicity and should be reduced."

The EFSA panel also called for all neonicotinoid insecticides to be tested for toxic effects in the developing brain.

The report is likely to add fuel to a debate that has been raging about the health and environmental impacts of neonicotinoids. Bayer and Syngenta AG , which manufactures one of the other neonicotinoids linked to bee deaths, deny that their products cause "colony collapse disorder," the phenomenon of sharply falling honey bee populations seen around the world that has become a ferocious dispute between chemical companies, scientists and environmental groups.

The two companies in August brought a complaint against the European Commission, the EU's executive arm, saying the restrictions are based on faulty science.

In response to Tuesday's report, Bayer said imidacloprid isn't a developmental neurotoxin. "EFSA's concerns regarding the developmental neurotoxicity potential of imidacloprid are based on a 2012 publication by Japanese scientists, which reports investigations in rat cell cultures, i.e. in an artificial system," the company said in a statement.

A representative for Nisso Chemical, the European subsidiary of Nippon Soda, didn't immediately respond to a request for comment.

A spokeswoman for the European Commission, the EU's executive arm, said Bayer and Nisso will now have the chance to defend their products before the commission. Then the commission will decide whether to propose tougher exposure limits for workers using the chemicals, residents living near fields where they are applied and consumers buying products treated with the chemicals.

A proposal for lower exposure limits would likely be discussed at a meeting of experts from the 28 EU member states in March, the spokeswoman said.

DuPont, which sells an insecticide with the brand name Assail that contains acetamiprid, is "aware of the latest EFSA assessment on acetamiprid and imidacloprid, and we are reviewing it," said spokesman Mike Hall.