A captured episode of γ-hexachlorocyclohexane air pollution in the Toronto area after the Canadian lindane ban

Abstract

A Canadian ban on lindane for agricultural use came into effect on December 31, 2004. In the years leading up to this ban, air concentrations of γ–HCH, the active ingredient of lindane, decreased gradually over the Great Lakes region. Typical mean concentrations were about 5 and 10 pg m-3 for Lakes Huron and Ontario, respectively, during the summer of 2005. However, during the period June 27–28, 2005, a γ–HCH air pollution episode was captured in Toronto by three independent sampling programs [Episodic Pesticide Transport (EPT) Study, Integrated Atmospheric Deposition Network (IADN) and Canadian Atmospheric Network for Currently Used Pesticides (CANCUP)], with concentrations of 586 and 3 070 pg m-3 measured in north and downtown Toronto, respectively – an increase of about two orders of magnitude above typical levels. This episode was not observed at any of the regional IADN sites on the same day, suggesting a localized emission in the city from an unknown and episodic source. This study demonstrates the value in continued monitoring of persistent organic pollutants (POPs) beyond their phase–out period and highlights the importance of combining information from different projects to discover environmental pollution events.