Metallic elements with high atomic weights; (e.g., mercury, chromium, cadmium, arsenic, and lead); can damage living things at low concentrations and tend to accumulate in the food chain. Mercury: Heavy metal that can accumulate in the environment and is highly toxic if breathed or swallowed. Chromium: Please See: The ATSDR fact sheet for chromium. Arsenic: Please See: The ATSDR fact sheet for arsenic.