periods, miscarriages, and giving birth to infants with congenital deformities than women who are not consistently exposed to mercury at work.21 Moreover, it was found that occupational exposure to mercury vapor lowered fertility rates among female dental assistants.22 A study examining the relationship between amalgam fillings and mother’s breast milk taken shortly after birth found a correlation between the concentration of mercury in milk and the number of fillings in the mother.23
Though the damaging effects mercury can exhibit on the reproductive system are known, many dental journals insist that the risk is low if proper mercury hygiene is used and mercury accumulation remains below the established “threshold limit value”—though no true “safe” level for mercury has ever been established.24,25
Even waste disposal has been an issue for the mercury used in amalgams by dental practitioners, and amalgams have now been identified as a significant source of environmental pollution.26 With a focus on the tons of mercury-amalgam waste dumped into sewers or on land in the United Kingdom, the WHO reported that as much as 53 percent of total environmental mercury emissions come from dental, laboratory, and medical waste.27 An estimated one-third of mercury waste collected in sewage sludge comes from dental discharge.
Methods for separating amalgam and reducing mercury levels in waste have been deployed, while many countries have begun regulating dental disposal practices.28,29 However, discharged mercury remains a widespread and significant environmental problem, and many dental amalgam separation technologies have been found inadequate at reducing pollution levels.30
Once mercury enters the environment, microbes readily convert the elemental mercury into methylmercury, which significantly bioaccumulates and becomes a major issue in the food chain, as with fish (see “Methylmercury in fish” on page 49 for more information).
Mercury from dental amalgams has even been found to be a significant environmental pollutant through its release into air after deceased people who had fillings in their teeth are cremated, as mercury is being released at levels similar to other industrial emissions.31
Even with the abundance of studies noting the adverse effects and the FDA’s reclassification of amalgam as riskier to health, the American Dental Association (ADA) continues to assert that mercury-containing dental amalgam is “a safe, affordable, and durable material.”32
Banned in the EU; concerns about exposure in U.S. products
The European Union has banned nearly 1,400 chemicals from being used in the production of cosmetics based on health risk assessment that they may be carcinogenic, mutagenic, or reproductive toxicants.98 In an attempt to rein in mercury by-products, the European Union enacted a ban, beginning in 2011, on the export of mercuric chloride, cinnabar ore, and many derivatives.99 Mercury, lead, and arsenic (among others) have all been banned as cosmetic additives in Canada.
By contrast, the U.S. FDA has only banned ten ingredients, and even though mercury is on that short list, up to 65 parts per million of mercury is still allowed in cosmetics applied to the eye area.100 As of 2007, Minnesota was the first U.S. state to officially outlaw thimerosal, a mercury derivative, in some cosmetics, including mascara, eye liners, and skin-lightening cream—a far stricter rule than the federal standards currently in place. One of the concerns Minnesota officials considered was that fumes from these cosmetics could build up within the containers and users might inhale them upon opening the products. Minnesota Senator John Marty, who sponsored the ban, noted, “Mercury does cause neurological damage to people even in tiny quantities.”101
Bioaccumulation
The senator is correct: Mercury damages human health. Even low-level mercury exposure can be toxic, and chronic exposure bioaccumulates in the body. Mercury poisoning can induce reproductive, developmental, systemic, immunological, genotoxic, and carcinogenic adverse effects, potentially impacting every single body system.102 Although science has long established the grave effects that mercury poisoning can have on the brain and nervous system—especially for fetuses and developing children—exposure to even smaller amounts have been linked to cardiovascular disease and neurotoxicity.103
Methylmercury in fish
Methylmercury, as found in tuna and other large fish, is the primary source of dietary mercury consumed today. Once ingested, methylmercury is absorbed through the gastrointestinal tract where it is eventually converted to inorganic mercury. Five percent of bodily mercury load is found in the blood and another 10 percent is found in the brain. The metabolism rate for mercury is slow, so less than 1 percent of the total mercury in the body is actually excreted in a given day.104
The New York Times conducted an investigation on mercury involving twenty Manhattan sushi restaurants and stores in 2007 and found that eating a mere six pieces of sushi a week would actually surpass EPA limits on mercury. Five of the twenty restaurants had mercury levels high enough to warrant FDA action.105
To avoid mercury toxicity, considering your fish intake is important.
Mercury and Seafood: Eating Guide
Highest Mercury (Avoid eating)
Mackerel (King), Marlin, Orange Roughy, Shark, Tilefish
High Mercury (Eat only three servings or less per month)
Bluefish, Grouper, Sea Bass (Chilean), Tuna (Yellowfin, Canned Albacore)
Moderate Mercury (Eat six servings or less per month)
Bass (Striped, Black), Carp, Cod (Alaskan), Croaker (White Pacific),
Halibut (Atlantic, Pacific), Lobster, Mahi Mahi, Perch (Freshwater),
Sablefish, Sea Trout, Snapper, Tuna (Canned Chunk Light, Skipjack)
Least Mercury
Anchovies, Butterfish, Clam, Crab (Domestic), Croaker (Atlantic),
Flounder, Hake, Herring, Mullet, Oyster, Plaice, Pollock, Salmon, Sardine,
Scallop, Shrimp, Sole (Pacific), Tilapia, Trout (Freshwater), Whiting
Source: The Natural Resources Defense Council (based on FDA and EPA data). NRDC. org. www.nrdc.org/health/effects/mercury/walletcard.PDF.
In my lab testing, I have primarily found mercury in fish—and shellfish-derived food products, including those harvested from the North Atlantic region. Beware of high mercury content in pet food treats derived from fish, where I’ve spotted some products containing more than 1,000 ppb mercury (1 ppm).
THE SYSTEMIC, APOCALYPTIC POLLUTION OF THE WORLD’S OCEANS
Approximately ten years ago, Newcastle yachtsman Ivan Macfadyen decided to sail from Melbourne, Australia, to Osaka, Japan, then on to San Francisco, California. In a 2013 interview with the Newcastle Herald, Macfadyen recalled how the ocean was teeming with life: sounds of sea birds and an abundance of fish to catch with a simple bait and line.1
Expecting a similar journey, Macfadyen recently decided to redo the trip only to find a very different ocean waiting for him. For
