ED points and NOELs: how they are used by UK pesticide regulators

The availability and use of ED point and NOEL values in ecotoxicological data submitted to the UK Pesticides Safety Directorate is explored. In first tier data normally submitted for pesticide registration, ED points such as EC/LC/LD50s are commonly available from acute laboratory toxicity studies conducted using birds, small mammals, fish, aquatic invertebrates, plants, honeybees and earthworms. These ED points are subsequently used for hazard classification of the pesticide and in toxicity: exposure ratio (TER) calculations required during the acute risk assessment. Although NOELs can often be available from the same first tier data, they are generally not used. However, NOELs commonly available from higher tier chronic toxicity studies such as chronic fish, Daphnia reproduction and avian reproduction studies, are used in TER calculations to assess chronic risk. The statistical limitations of the NOEL are recognized and the regulatory implications of replacing the NOEL with an alternative ED point are discussed.