Mercury is an environmental pollutant that accumulates in fish and other sea life. which human activity has had the greatest impact on increasing mercury levels?

While mercury occurs naturally in the environment, human activities that increase the number of  elements in the ecosystems. Examples of such activities include;

When the mercury settles in lakes and oceans and consumed by fish, the toxin get to the fish tissues. As the fishes are predated on, there occurs a phenomenon called bioaccumulation in the high animals in the food chain.