Exposure and environmental impact

More knowledge needed on breakdown products in the environment

Pesticides are broken down, more or less rapidly, via chemical, physical or biological processes to one or more breakdown products. In individual cases the breakdown products can be more toxic than the parent substance. Despite this, relatively little is known about the breakdown products formed, how they are spread and how they act in the environment. An attempt by Dutch researchers to carry out risk assessments on 78 breakdown products originating from 20 common pesticides revealed a lack of information. For more than 45% of the breakdown products there was absolutely no available ecotoxicological information, i.e. information on the toxicity of the substances for different organisms. The researchers considered that there was sufficient ecotoxicological information for less than 10% of the breakdown products. A similar lack of information was reported for physico-chemical properties, i.e. the properties that determine e.g. the spread to aquatic environments and the degradability. Sufficient physico-chemical information was lacking for more than 50% of the breakdown products. It is naturally difficult to make a risk assessment and predict possible ecological effects when the available information is so scarce.