Mercury primarily emanates from coal combustion, electric/light bulb, wood preservatives, leather tanning, ointments thermometers, adhesives and paints.
Cadmium often originates from industries like battery manufacturing, paint pigments, pesticides, galvanized pipes, plastics, polyvinyl and copper refineries.
Lead an extremely toxic metal, commonly originates from substances like Pb-based paints, gasoline and mobile batteries.
Chromium is emitted from a variety of industrial activities, including petroleum refining, electroplating, leather tanning, textile manufacturing, and pulp processing.