Benzene is everywhere — how much exposure is safe?

Concerns about air pollution in the area of southwestern Ontario dubbed Chemical Valley go back decades. And earlier this year, high benzene levels prompted Aamjiwnaang First Nation — which neighbours a petrochemical facility — to declare a state of emergency. Last week, some members of the First Nation left their homes due to an expected spike. Benzene, however, isn't only found near industrial areas. CBC's Chris Ensing explains what this chemical is and how much long term exposure