A sign warns of a possible benzene leak at the Aamjiwnaang First Nation, near Sarnia, Ont., on Oct. 1, 2024. The removal of the substance from the nearby Ineos Styrolution plant prompted a voluntary evacuation order in the community.

High levels of the chemical benzene were registered in the air near Sarnia, Ont., in April, forcing neighbouring Aamjiwnaang First Nation to declare a state of emergency after people became ill with headaches, nausea and dizziness.