New approaches to assessing the risk of groundwater contamination by pesticides

Because of the large range of circumstances (such as soil-type, climatic zo ne, and local agricultural practice) in which pesticides are applied, it is impossible to test fully the environmental fate of a new pesticide being c onsidered for registration. Thus, risk assessors should make best use of mo dern techniques and all relevant information to make their assessments. Thi s paper discusses the use of statistical methods which use pesticide chemic al properties to predict environmental fate. Using US data, a logistic regr ession approach can be used to estimate the probability that a compound lea ches to groundwater based on adsorption (K-oc) and degradation (DT50) param eters. An advantage is that both properties are already required to be meas ured as part of the present pesticide registration process. For UK groundwa ter monitoring, precise pesticide soil properties are not measured. However , further methods using UK data also indicate that polluting and non-pollut ing compounds may be distinguished on the basis of these chemical propertie s. The techniques presented can be used in conjunction with pesticide usage statistics to inform the selection of priority pollutants, to enable monit oring programmes to become more focused, to assess the risk associated with new compounds, and to identify those at high risk of contaminating groundw ater.