Len has served on various expert panels and boards including the International Centre on Pesticide Safety, the U.S. National Academy of Sciences, the National Cancer Institute of Canada and the Canadian Cancer Society, the US National Cancer Institute, and the World Health Organization Joint Expert Committee on Food Additives. Len advises government departments and agencies, and various industries, in Canada and abroad on issues related to pesticides, risks from exposure to toxic chemicals, and human health risk assessment.
Len has been a long serving expert advisor to the Joint Expert Committee on Food Additives of the Food and Agricultural Organization/World Health Organization of the United Nations. His research interests have focused on adverse health outcomes associated with exposure to pesticides and environmental contaminants and residues in food.
Len serves on the US EPA Human Studies Review Board. He is a Fellow of the Academy of Toxicological Sciences, and in 2006, was awarded a medal by the World Health Organization in recognition of his contributions to the work of the United Nations Joint Expert Committee on Food Additives.