Although your body needs some metals, such as iron and zinc, others, including lead and mercury, are harmful and cause a range of toxic effects. These hazardous metals are present in the environment as pollution from sources such as manufacturing processes and discarded household goods. Governmental and other agencies monitor foods, consumer products and working conditions for the presence of these metals, helping improve public health by reducing exposure to them.
Known and used for thousands of years, lead is a relatively soft, dense and inexpensive metal, used both in its pure form and in compounds. A good electrical conductor, lead is used for components such as car battery terminals. Lead is also used in paint pigments and radiation shielding. If ingested, lead accumulates in the bones, kidneys and liver; small amounts add up over time, leading to nervous system, blood and kidney diseases.
The metal cadmium is employed in industry for electroplating processes; manufacturers also use it in red and yellow pigments for artists’ paints. As with lead, the human body has difficulty eliminating cadmium, so it accumulates over a person’s lifetime. Symptoms of cumulative cadmium poisoning include kidney problems, liver damage, loss of sense of smell, and shortness of breath.
Although technically a semi-metallic element, arsenic’s well-known toxic properties make it natural to include in discussions of hazardous metals. Electronics component manufacturers use small amounts of arsenic in combination with silicon for light-emitting diodes and other devices. The human body eliminates half its arsenic in about a day, but chronic exposure leads to health hazards. Arsenic poisoning affects several major organs, including the skin, nervous and reproductive systems, liver and lungs.
Mercury is a silvery, dense metal, liquid at room temperatures. Although it was once widely used in thermometers and barometers, as it provided a clear indication of temperature or pressure, mercury’s toxic effects led to its replacement in these applications. Mercury vapor continues to be an essential part of fluorescent lamps, including compact fluorescent bulbs; each lamp or bulb uses only a tiny amount of mercury. Although your body eliminates mercury more efficiently than it does lead and cadmium, mercury can still accumulate to hazardous levels. Mercury toxins accumulate in fish such as king mackerel and albacore tuna; because of widespread pollution, the Environmental Protection Agency recommends against the consumption of these fish for pregnant women. Anaerobic organisms in the environment convert mercury to methylmercury, which damages the nervous system, leading to blurred vision, “pins and needles” sensations in the tongue and lips, and hearing difficulties.
Hexavalent chromium is a toxic form of chromium used in industry for electroplating chrome finishes, in dyes and paints, and as a byproduct of stainless steel welding. The toxic metal can cause skin rashes from contact dermatitis. When particles of hexavalent chromium are inhaled, physical reactions vary widely. According to the Occupational Health and Safety Administration, some people are not affected by breathing in small amounts of the metal; others develop respiratory conditions ranging from nosebleeds and irritation to lung cancer.
- National Institutes of Health: Iron
- Stanford University: Human Health Concerns of Lead, Mercury, Cadmium and Arsenic
- Georgia State University: Fluorescent Lighting
- Royal Society of Chemistry: Cadmium
- Environmental Protection Agency: What You Need to Know about Mercury in Fish and Shellfish
- Web Elements: Arsenic
- Occupational Safety and Health Administration: Health Effects of Hexavalent Chromium
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