https://phys.org/news/2019-01-fort-mcmurray-homes-indoor-toxins.html > As people slowly gained re-entry to their homes a month later, concerns were raised about residual fire ash or toxins in homes that could pose health risks. Smoke and ash can contain a large number of potentially harmful carcinogens, including arsenic, heavy metals and polycyclic aromatic hydrocarbons (PAHs). > In the summer of 2017, chemical engineering professor Arthur Chan and his research team visited Fort McMurray to find out if there was indeed cause for concern. "Many people were saying, 'I'm not sure if it's safe for my children to come back and live here after this big fire,'" says Chan.