Common sources
Mercury
Dental amalgam fillings are roughly 50% mercury by weight and continuously release small amounts of mercury vapor, particularly during chewing and grinding [1]. This is a contentious topic — regulatory agencies maintain amalgams are safe for most adults, while many integrative practitioners consider them a significant chronic exposure source.
Large predatory fish — tuna (especially albacore and bigeye), swordfish, shark, king mackerel, and tilefish — concentrate methylmercury up the food chain. Methylmercury is the most toxic organic form and is readily absorbed from the gut [1].
Other sources: compact fluorescent light bulbs, certain vaccines (thimerosal, though largely phased out), contaminated water near mining sites, and some traditional medicines.
Lead
Old paint in homes built before 1978 remains the primary source of lead exposure in children. Deteriorating paint creates lead dust that settles on surfaces and contaminates soil around older buildings [2].
Old plumbing — lead pipes, lead solder on copper joints, and brass fixtures can leach lead into drinking water, especially in older homes and cities with aging infrastructure.
Contaminated soil around industrial sites, near old highways (from decades of leaded gasoline), and near shooting ranges.
Other sources: some imported ceramics and pottery glazes, certain cosmetics (particularly traditional kohl eyeliner), and some imported candies and spices.
Arsenic
Rice is a major dietary source of inorganic arsenic because rice paddies flood with water that may contain arsenic, and rice plants are unusually efficient at absorbing it [3]. Brown rice contains more arsenic than white rice because it concentrates in the bran layer.
Groundwater in certain regions — particularly parts of Bangladesh, West Bengal, and some areas of the American Southwest — contains naturally elevated arsenic levels.
Other sources: pressure-treated wood (CCA-treated lumber, pre-2004), apple juice from concentrate, some wines, and chicken (historically from arsenic-containing feed additives, now largely banned).
Cadmium
Cigarette smoke is the dominant source of cadmium exposure for smokers — tobacco leaves accumulate cadmium from soil.
Chocolate and cocoa can contain significant cadmium levels, particularly cacao grown in volcanic soils in Latin America.
Other sources: shellfish, organ meats, and occupational exposure in battery manufacturing, pigment production, and metal plating.
Who is at risk
- Children — more vulnerable to lead and mercury due to developing nervous systems and higher absorption rates relative to body weight
- Pregnant and nursing women — metals cross the placenta and enter breast milk
- People with dental amalgams — chronic low-level mercury vapor exposure
- Regular consumers of large fish — methylmercury accumulation
- Smokers — cadmium exposure
- People in older homes — lead paint and plumbing
- Communities near industrial sites or mines — multiple metal exposures
- Rice-heavy diets — arsenic exposure [3]