A Natural Intervention Study: Closure Of The Oakville Oil Refinery

Abstract

INTRODUCTION: Under the Clean Air Regulatory Agenda, Health Canada is mandated to study the effect of air pollution from various industrial sources on Canadian population health. An oil refinery in Oakville, Ontario in 2004-05, providing an opportunity for a natural experiment, comprising analysis of the effects of changes in oil refinery-related air pollution on human health. METHODS: To evaluate the impact of the oil refinery-related air pollution on public health, we compared air pollution levels and both cause-specific hospitalizations and mortality counts before and after the refinery closure based on a balanced two-period design. The refinery was located between two census subdivisions, Oakville and Burlington, which were considered the primary impacted areas. The next closest census divisions, comprising the Greater Toronto Area and Hamilton, were used as reference population. We examined wind speed and direction to be able to demonstrate reduction in air pollution. RESULTS: About 6,000 tonnes of sulphur dioxide (SO2) were emitted annually by the refinery prior to its closure. Following the refinery closure, ambient SO2 concentrations dropped on average 13% in Oakville and 21% in Burlington. Cold season age-standardized circulatory mortality rate decreased significantly after refinery closure (p