Long-term measurements of gamma-HCH in precipitation in the Netherlands

The results of 20 yr of measuring γ-HCH in precipitation in The Netherlands are presented here. Analysis has revealed a systematic seasonal behaviour, with enhanced levels of γ-HCH in precipitation from April through June. A statistically significant change in concentrations during the last 20 yr was found. An evaluation of measurement results from north-west Europe confirms the large-scale distribution of γ-HCH in precipitation in that region. Long time series of γ-HCH measurements are a useful tool in evaluating its emission trend. Given the large uncertainties in emission estimates and in modelling of atmospheric transport and deposition up to now, measurements are considered to be a better tool for monitoring the changes in environmental levels of γ-HCH.