Metals are essential for many uses, but some, such as mercury, arsenic, cadmium, and lead, can cause health harm. Fetuses and young children are particularly susceptible.
What are they?
Mercury, arsenic, cadmium, and lead are elements that occur naturally in the earth’s crust. Mining and smelting, fossil fuel combustion, industrial processes, and the use and disposal of products containing them have led to widespread environmental contamination and human exposure and health harm.
Where are they found?
Coal burning plants can release mercury into air and water. The bacteria in bodies of water convert it into the more toxic methylmercury. Then, methylmercury is taken up by and concentrated in fish, with levels increasing up the food chain. Eating long-lived fish such as tuna is the major source of mercury exposure in humans. Other sources include some imported face creams, silver-colored dental fillings, glass thermometers, barometers, and fluorescent lights.
The major source of arsenic exposure is food. For example, rice, mushrooms, apples, and grapes can absorb arsenic from contaminated water and soil. Rice products (like infant cereal) have the highest amount of inorganic arsenic, which is the more toxic form. Inorganic arsenic is also found in pressure-treated wood used for outdoor structures manufactured before 2004, some drinking water sources, and cigarette smoke.
Cadmium is found in cigarette smoke, certain foods (shellfish, leafy vegetables, potatoes, grains, legumes), metal costume jewelry and charms, rechargeable batteries (labeled NiCd or NiCad), metal plating and solder, and some decorative paints used on glassware and pottery.
The major source of exposure to lead is peeling paint and dust in and around homes built before 1978. Lead can leach into water from plumbing and fixtures (common in plumbing before 1986) that are either made of lead or have lead solder, especially when the water is acidic. Lead can also be found in improperly made or deteriorating dishware and cookware, toys and costume jewelry, imported or recycled vinyl products, and lipstick.
What are the health concerns?
Exposure to mercury, arsenic, cadmium, and lead in the womb or in early childhood can harm brain development, leading to learning and behavioral problems. In adults, each metal is associated with increased cancer risk. Mercury and arsenic are associated with adverse effects on the nervous and cardiovascular systems. Cadmium is associated with lung and kidney damage as well as weakened bones. Lead can cause high blood pressure, miscarriages, stillbirth, infertility, and decreased kidney and brain function.
How are we exposed?
People are exposed to these metals through eating and drinking contaminated food and drinking water, ingesting and inhaling dust, inhaling cigarette smoke, and using certain products (listed above). In pregnancy, mercury, arsenic, cadmium, and lead cross the placenta and fetal blood-brain barrier during critical windows of brain development. Infants are further exposed through breastfeeding. Young children typically have higher exposure to metals because they consume more food in relation to their body weight, put their hands and toys in their mouths, and absorb metals more readily than adults.
What are the environmental concerns?
As they are chemical elements, these metals cannot be broken down, leading to accumulation in ecoystems. When released into the air, they can travel long distances before falling on land or surface waters. Because of their persistence and potential for long-range transport, industrial emissions of metals affect even the most remote regions.
The accumulation of methylmercury in fish has led to decreased reproduction rates in some fish-eating birds and other animals. Arsenic can harm aquatic organisms and reduce crop yields. Cadmium accumulates in plants, affecting the health of herbivorous mammals. Elevated lead in the environment can result in decreased growth and reproduction rates in plants and animals as well as and neurological effects in vertebrates.
What should be done to reduce exposure?
Despite significant decreases in exposure due to technological improvements and reduced usage in some products and industrial processes, these metals continue to pose health and environmental risks. For example, blood lead levels in U.S. children have declined by 90% since the mid-1970s from the elimination of lead in gasoline and paint. However, many in the U.S. are still exposed to lead through paint dust in housing built before the 1978 and drinking water service lines made from lead, lead solder, or plumbing materials that contain lead. Further phase outs, abatement programs, emission regulations, cleaner technologies, and proper disposal practices are necessary to reduce metal contamination.
What Can You Do?
Reduce dust exposure by vacuuming, wet-mopping, using door mats, and washing hands.
Eat a well-balanced diet with adequate calcium, iron, and vitamin C, which can help reduce the amount of lead and cadmium that your body absorbs.
Properly recycle CFL bulbs, batteries, paint, and electronic waste in the trash (find appropriate recycling facilities here).
To reduce mercury expsoure:
Avoid fish that are high in mercury, such as shark, swordfish, orange roughy, bluefin, and bigeye tuna (see this chart by the U.S. FDA).
Do not use imported skin lightening, acne treatment, or anti-aging creams unless you are certain that they do not contain mercury.
Purchase LED light bulbs instead of compact fluorescent light (CFL) bulbs.
Properly clean up broken thermometers, CFL bulbs, and other items containing mercury (find EPA guidance on cleaning up spills here).
To reduce arsenic expsoure:
To reduce arsenic in your child’s diet, include alternatives to rice-based foods whenever possible.
Do not use pressure-treated wood manufactured before 2004 which may contain arsenic. Have children wash their hands after they play on or around older wooden play structures or decks. If you own such a structure or deck, apply a sealant or coating every one to two years.
To reduce cadmium expsoure:
Do not let children wear or play with inexpensive metal jewelry or charms.
Do not let children handle rechargeable batteries labeled NiCd or NiCad.
To reduce lead expsoure:
Renovations, repair jobs and paint jobs in pre-1978 homes and buildings can create significant amounts of lead-based paint dust. In these homes, contractors should be trained in lead-safe practices. Find a Lead-Safe Certified firm here.
Keep children away from chipped and peeling paint.
Cover bare soil with grass, bark, or gravel, especially near homes built before 1978.
Use cold water for drinking or cooking to reduce release of lead from some faucets and old pipes.
Other Videos on Certain Metals
Webcast introducing the new Certain Metals video featuring conversation with Michael Kirschner, Meredith Williams, and Arlene Blum.
Introduction to Certain Metals: Graham Peaslee, Hope College
TEDxGreatPacificGarbagePatch – Arlene Blum – Plastic Pollution In Our Homes
Where have all the toxic chemicals gone? Arlene Blum at TEDxWellesleyCollege
- The Minamata Convention on Mercury – This international treaty obliges governments to take a range of actions, including to address mercury emissions to air and to phase-out certain mercury-containing products.
- Arsenic and Environmental Health: State of the Science and Future Research Opportunities – This recent National Institute of Environmental Health Sciences report assesses arsenic exposure sources, health risks, and remediation strategies.
- The Broad Scope of Health Effects from Chronic Arsenic Exposure: Update on a Worldwide Public Health Problem – This report in Environmental Health Perspectives reviews chronic arsenic exposures and health risks and emphasizes the importance of reducing exposure, particularly during pregnancy and early life.
- Exposure to Cadmium: A Major Public Health Concern – This WHO report reviews sources of exposure and health effects of cadmium and proposes strategies for decreasing cadmium levels in the environment.
- NTP Monograph on Health Effects of Low-level Lead – This report by the National Toxicology Program discusses the evidence that even very low-level lead exposures can have adverse health impacts on both children and adults.
- Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention – This CDC advisory committee report recommends the discontinuation of the term blood lead “level of concern” (to acknowledge that there is no safe level) and the adoption of a lower “reference value” of 5 μg/dL to identify children with elevated blood lead levels.
- Three ways scientists are trying to keep arsenic out of our diets. Science Magazine, 2/18/2017.
- Special Report: Thousands of U.S. areas afflicted with lead poisoning beyond Flint’s. Reuters, 12/19/2016.
- Why it’s still so hard to eat fish and avoid mercury. Washington Post, 3/18/2016.
- How much arsenic is in your rice? Consumer Reports, 11/18/2014.
- Lead in jewelry leads to California crackdown. NBC News, 7/17/2012.
- Is cadmium as dangerous for children as lead? Scientific American, 2/10/2012.
- Some skin whitening creams contain toxic mercury, testing finds. Chicago Tribune, 5/18/2010.