I am an environmental epidemiologist. My main interests in research have been in occupational and environmental epidemiology, focusing especially on environmental and occupational causes of cancer as well as on the short- and long-term effects of air pollution on health. My research bridges clinical and environmental epidemiology and I have published almost 200 papers in peer-reviewed journals, covering myriad topics, including the health effects arising from exposures to ambient biogas produced in municipal solid waste sites, environmental and occupational causes of disease, and occupational and environmental investigations of breast cancer, ovarian cancer, colon cancer, and lung cancer. Since 1995, I have conducted numerous studies on the acute and chronic health effects of ambient air pollution. Notable among these are my recent findings that chronic exposure to ambient air pollution may cause breast cancer and prostate cancer. From 2009 until 2013 I was co-editor in chief of the scholarly journal Environmental Research. I was a member of Health Canada’s Science Advisory Board and I have sat on a number of expert committees of the U.S. National Academies.