Asbestos and lead are two hazardous substances that may be present in electrical equipment.
Asbestos may be found in breakers, panels, cable conduits and wraps. Lead may be found in some wire and cable coatings.
Exposure to lead or asbestos can cause serious health problems. Asbestos fibers may attach themselves to clothing, which puts coworkers, friends and family at risk. Inhaling asbestos may cause chronic lung disease or cancer. Lead particles may be inhaled from combustion gases or even absorbed into the skin if directly contacted and can damage organs, muscles and bones.
These substances are not easily detected, so you must assume that all electrical equipment and coatings contain them.