What is the best first test for heavy metal exposure?

Mercury

Dental amalgam fillings are roughly 50% mercury by weight and continuously release small amounts of mercury vapor, particularly during chewing and grinding¹. 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 gut¹.

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 buildings².

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 it³. 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 exposure³

Blood testing

Blood tests measure recent or ongoing exposure — metals circulating in the bloodstream. This is the clinical standard for acute lead exposure (blood lead level) and methylmercury. However, blood levels can appear normal even when tissues have accumulated significant amounts, because metals move from blood into organs and bones relatively quickly.

Urine testing

Unprovoked urine testing measures metals being naturally excreted by the kidneys. Useful as a baseline and for monitoring ongoing exposure.

Provoked (challenge) urine testing involves taking a chelating agent (like DMSA) and then collecting urine for 6-24 hours to measure what gets pulled out. This is controversial — the provoked values have no established reference ranges, and comparing provoked results to unprovoked reference ranges (as some labs do) will always make it look like you have high levels⁴. Some practitioners find it clinically useful for assessing body burden, but the interpretation requires expertise.

Hair mineral analysis

Hair testing reflects exposure over the period the hair was growing (typically 2-3 months for a standard sample). It can be useful for identifying chronic exposure patterns, particularly for mercury and arsenic. However, external contamination (hair products, environmental dust) can affect results, and standardization across laboratories remains inconsistent⁴.

The pragmatic approach: If you suspect heavy metal exposure, start with a standard blood panel through your doctor (blood lead, blood mercury). If you want a broader picture and are working with an integrative practitioner, unprovoked urine and hair mineral analysis can add context. Be cautious about provoked urine tests unless your practitioner has specific expertise in interpreting them.