The toxic effects of mercury depend on its chemical form and the route of exposure. Methylmercury [CH3Hg] is the most toxic form. It affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste, and sight. Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults. Exposure to methylmercury is usually by ingestion, and it is absorbed more readily and excreted more slowly than other forms of mercury. Elemental mercury, Hg(0), the form released from broken thermometers, causes tremors, gingivitis, and excitability when vapors are inhaled over a long period of time. Although it is less toxic than methylmercury, elemental mercury may be found in higher concentrations in environments such as gold mine sites, where it has been used to extract gold. If elemental mercury is ingested, it is absorbed relatively slowly and may pass through the digestive system without causing damage. Ingestion of other common forms of mercury, such as the salt HgCl2, which damages the gastrointestinal tract and causes kidney failure, is unlikely from environmental sources.
Risk to People
People are exposed to methylmercury almost entirely by eating contaminated fish and wildlife that are at the top of aquatic foodchains. The National Research Council, in its 2000 report on the toxicological effects of methylmercury, pointed out that the population at highest risk is the offspring of women who consume large amounts of fish and seafood. The report went on to estimate that more than 60,000 children are born each year at risk for adverse neurodevelopmental effects due to in utero exposure to methylmercury. In its 1997 Mercury Study Report to Congress, the U.S. Environmental Protection Agency concluded that mercury also may pose a risk to some adults and wildlife populations that consume large amounts of fish that is contaminated by mercury.
Styrene, the primary raw material used in the production of extruded or expanded polystyrene, is a petrochemical that has been the subject of dozens of studies since plastics were developed. The Environmental Protection Agency (EPA) completed a Hazard Summary in 1992 and updated it in 2000 after the production of Styrofoam was reformulated with materials to replace chlorofluorocarbon (CFC) chemicals. The EPA found that the primary risks associated with styrene were occupational as well as outgassing found in indoor air from polystyrene building materials, consumer products and tobacco smoke. Although the EPA made no assertion of positive cancer risk, central nervous system effects from headaches, fatigue and depression to dysfunction in reaction time, memory loss, visual-motor accuracy and intellectual function were reported in humans. More physical and reproductive risks were suggested in animal studies; some effects were reported among humans in hearing loss, kidney and blood as well as acute mucous membrane irritation and gastrointestinal effects.
Polystyrene presents the classic pollution problems: hydrocarbons and other toxic substances are used in its manufacture, are present in the finished material or are released into the atmosphere during its use or incineration. A viable recycling industry does not exist, in part because the bulky EPF contains so little reclaimable styrene. Polystyrene does not decompose–it breaks into smaller pieces, creating permanent litter and unusable fiber for hungry wild animals. The addiction to EPF is profound because it has become an integral and, in some cases, more environmentally friendly material than many options in today’s fast-paced consumer society. With so many problematic materials to choose from, the answer may lie in new materials such as organic plastics made of corn or bamboo or developing viable industries to refashion goods out of post-consumer materials.
Styrofoam Cups in the Microwave or oven. . . major bad news
Although there is no research to suggest that Styrofoam causes ill health effects when used correctly, it is not microwave-safe. Styrene can melt in the microwave, causing plastic and chemicals to migrate from the cup into your drink. Low levels of the chemicals may not affect you. However, according to the Environmental Protection Agency, if you ingest too much styrene you may suffer from weakness, depression, fatigue, nerve and liver damage or cancer. The USDA advises that you should only use microwave-safe containers in the microwave.
Hazards of Teflon
Teflon has been making headlines. But they are headlines that its manufacturer, DuPont Co, would rather live without. The focus of the stories is PFOA, a chemical which is a key component in Teflon and other nonstick coatings.
A scientific advisory panel to the US Environmental Protection Agency recently unanimously recommended that PFOA should be considered a likely human carcinogen. This classification means that there is evidence of cancer causing effects from both human and animal studies.
Leaked documents exposed that DuPont hid studies showing the risks of a Teflon related chemical, Zonyl which breaks down into PFOA. Zonyl is used to line microwave popcorn bags, candy wrappers, pizza boxes and hundreds of other food containers. The documents describe “laboratory tests showing [Zonyl] came off paper coatings and leached into foods at levels three times higher than the FDA limit set in 1967.” Other tests showed “anemia and damage to …kidneys and livers” in rats and dogs fed Zonyl for three months.
Researchers at Johns Hopkins Hospital tested the umbilical cords of 300 newborn babies, and found that 99% of the babies were born with trace amounts of PFOA. The scientists are now studying whether the toxic chemical has harmed the infants, possibly by interfering with their thyroid glands and hormone levels.
Studies conducted earlier by the Center for Disease Control found PFOA in the bloodstream of 95% of US citizens. According to the EPA, PFOA can remain in the human body for up to four years.
Teflon’s breakdown chemical, PFOA, is a serious concern for a number of reasons. In addition to evidence that it is a likely cause of cancer, it falls into the category of chemicals which are persistent and accumulative. This means that rather than breaking down into harmless substances over time, they remain as they and accumulate in the environment. This is why studies which found PFOA in new born infants and in polar bears are so significant. Since neither newborns or polar bears use teflon coated objects, the presence of PFOA in their bodies shows that the substance builds up in the body and that exposure comes from environmental buildup of the chemical
In addition to its well known uses in nonstick coatings, PFOA is used in manufacturing stain-resistant clothing, bedding and upholstery fabrics, rain-repellant clothing, house paint, computer chips, coating on irons, stain resistant treatments for carpets, and a wide range of other products. While there is still debate about the toxicity of Teflon at normal temperatures, it is well established that at high heat, Teflon emits a toxic gas.