Coverage for pollution is limited to cleaning up pollution that was caused by a covered cause of loss occurring during the policy period. For example, if vandals opened drums of a toxic chemical and poured it on the ground, the insurer would cover the cost of the cleanup, up to the policy limit, since vandalism is a covered cause of loss. On the other hand, if the toxic chemical slowly leaked into the ground because the drum was defective and had a tiny hole in it, you would not have coverage under the BOP. A defect in the drum is not a covered cause of loss under your property policy. For help with cleanup costs in this hypothetical situation, you might find compensation from the liability insurance of the drum manufacturer or seller of the chemical.