Toxicological assessment of biological pesticides

The majority of pesticides are based on synthetic chemicals. Regulatory assessments are performed by comparing the findings in a range of routine toxicity studies, designed for testing chemicals, with estimates of exposures. Recently there have been significant moves towards developing natural/biological alternatives. Biological pesticides (those based on viable organisms) present the regulator with a different set of challenges to those raised by most chemical pesticides. The concerns associated with biological pesticides can vary greatly from one organism to another, requiring an almost case-by-case approach. The known toxicity of certain bio-molecules and the pathogenicity of certain organisms underlines the need for a risk assessment of biological pesticides. The main aspects of a health risk assessment are characterisation of the organism, infectivity, pathogenicity, sensitisation and production of toxic secondary metabolites. Obtaining information or data on these areas is not always easy as there are no widely accepted test schemes or protocols for organisms, though guidelines are being developed for the European Commission (EC). Predicting exposure following pesticidal use of an organism is made more complex if it multiplies or secretes toxic metabolites. Reliable data on effects (lack of) associated with naturally occurring (background) exposures can sometimes provide considerable reassurance. This paper describes the background to the proposed EC scheme, which has much in common with current UK practices, and presents three examples of biological pesticides which have been assessed under the existing UK procedures.