Foodborne Chemicals: Heavy Metals

Public health agencies should educate the public regarding ways to minimize heavy metal exposures. Anyone who knows that he or she has been exposed should contact a local poison control authority.

• Mercury is a well–known toxin. Mercury poisoning may cause digestive, respiratory, and neurologic disorders, and can be lethal. It easily crosses the placenta in pregnant women and may cause birth defects, even in the absence of symptoms in the mother.
  
  Mercury is used in medical instruments, although less commonly than in the past, and in some dental fillings. Mercury is also a common environmental pollutant, as a result of industrial processes.
  
  Aside from occupational exposures, the main exposure route is through ingestion of fish, especially those high on the food chain, such as shark, tuna, and swordfish, and certain fish taken from some freshwaters.
  
  Mercury toxicity is usually diagnosed by a blood test.
• Cadmium can contribute to kidney and bone disease and is considered a probable carcinogen by the federal Environmental Protection Agency.
  
  Cigarettes are a common source of cadmium exposure. Incineration of household waste, particularly batteries, may release cadmium into the atmosphere, and industrial processes such as mining and sewage sludge can pollute water and air. Phosphate fertilizers commonly contain cadmium, and grain and vegetable crops easily absorb the metal through polluted irrigation waters. Fish can have high levels of cadmium in their livers and kidneys, especially fish taken from urban waters and shellfish.
  
  Cadmium toxicity can be diagnosed through urine and blood tests.
  
• Lead poisoning can lead to brain and kidney damage. It may also adversely affect fetal and childhood development, and may cause infertility.
  
  Lead is very common in the environment and in households. It can be found in landfills that hold old electronic devices, in mine runoff areas, and in manufacturing facilities where lead is used in batteries, radiators, and other products. Groundwater and waterways may become contaminated from these sources, and many old houses still use lead pipes. In addition, older houses often have lead–based paint, which may flake off and be consumed by small children.
  
  Lead may also be present in toy jewelry, household crystal and glazed pottery used for serving foods and beverages, imported Mexican candy, and traditional medicines. For example, some Ayurvedic and Chinese medicines may contain lead, mercury, and arsenic. Air emissions, especially in areas where leaded gasoline is still available, may cause surface contamination of crops.
  
  Lead poisoning is diagnosed through blood testing.
  
  High–calcium diets may protect against lead accumulation by reducing absorption of lead in the intestines. High blood levels of vitamin C are also associated with lower risk for lead poisoning. However, neither calcium nor vitamin C has been shown in controlled clinical trials to reduce lead in the body.
• Arsenic exposure may increase the risk for skin and other cancers, including lung cancer.
  
  Arsenic is present in some pesticides, treated wood, and mining runoff. Arsenic is also a component of chicken feed supplements, and often reaches drinking water, especially untreated well water. Exposure through water is of particular concern, because the arsenic compounds formed are readily available for absorption into the body.
  
  Arsenic poisoning is commonly diagnosed through urine tests, although hair and nail samples can also reveal exposure.