Public awareness of the potential poisoning effects of heavy metals has increased greatly in the past few decades due to public awareness campaigns. Preschool-aged children have the greatest risk of poisoning, because of their tendency to place their hands and objects in their mouths, and their small mass means that they develop toxic levels at much lower doses than adults. The metals of primary concern are lead and mercury, although others have been discussed.
Lead Poisoning
The most-studied toxic heavy metal is lead. Lead poisoning is most common in the first couple of years of life, and it poses greatest harm during brain development as a fetus and young child. Some symptoms of acute lead poisoning include abdominal pain and constipation, irritability, lethargy, coma, seizures, and in some cases, death. Later, these children have poor attention span and difficulty learning.
Effects
The Environmental Protection Agency banned lead paint from use in homes in 1978, but the main source of lead poisoning continues to be old paint, either by ingestion of paint chips or inhalation of paint dust. Once in the bloodstream, the body will use lead like other metals, namely calcium and iron. Like calcium, lead will be deposited in bones and teeth. Lead in bones is fortunately locked in place and cannot cause any harm. Mimicking iron, lead will interfere with the production of red blood cells, leading to mild or moderate anemia.
Treatment
Lead levels can be monitored by simple blood tests. If the levels are moderate, then care should be given to remove all lead from the child's environment. If it is severe, a medication that binds lead, a chelating agent, is used in an inpatient or outpatient setting. The chelation is only effective on lead that is in the bloodstream, and will also increase the loss of some essential metals, like zinc.
Mercury
Mercury is also toxic to the nervous system. The leading source of mercury exposure is consumption of seafood. Developing fetuses are particularly sensitive to mercury exposure and the exposure may have severe consequences, such as cerebral palsy. Shark, swordfish and mackerel have high mercury levels, while shrimp, light tuna, salmon, pollock and catfish are low in mercury and serve as good sources of essential omega-3 fatty acids.
Other Sources
Other sources of mercury include some exterior paints, thermometers and other medical equipment, and some industries. Dental amalgams may contain mercury, but studies show that no toxicity results from them. Thimerosal, a preservative once used in some vaccines, has been blamed for numerous toxic effects; however, studies have shown no link between thimerosal and health problems, including autism.
Expert Insight
The subject of heavy metal toxins causing a large range of symptoms has been popularized by homeopathic and naturopathic companies and individuals. In October 2010, the Food and Drug Administration required eight companies offering over-the-counter "chelation" treatments to immediately stop sales of their products, citing false claims that their products treat a variety of problems, including autism. Dr. Marc Cohen, a professor of complementary medicine in Australia, states that "evidence-based detoxicology still seems quite far off, and at present 'detox' is certainly more of a sales pitch than a science."
References
- Medscape Today: Toxic Effects of Lead and Mercury
- "Nelson Textbook of Pediatrics, 16th Edition"; Robert Kliegman, MD; Richard E. Behrman, MD; Hal B. Jenson, MD; 2000
- Drugs.com: Chemet
- FDA: FDA Issues Warnings to Marketers of Unapproved 'Chelation' Products
- The Royal Australian College of General Practitioners: 'Detox': Science or sales pitch?
