Myth vs. Fact

Myth: Tuna is low in mercury and safe to eat.

Fact: Tuna are lower in mercury than shark and swordfish, for which FDA has issued a "no consumption advisory" for women of childbearing age and children; however, FDA specifically advised limiting tuna consumption because tuna do contain a considerable amount of mercury, and tuna is the most commonly consumed fish in the American diet. Every year, Americans eat more tuna than any other fish, making it the United States' most popular fish. There are two types of commonly eaten tuna: albacore and canned light tuna. Albacore tuna's mercury content is high enough that the Food and Drug Administration (FDA) has warned women and children to limit their consumption of it to 6 ounces a week. This means that if women and children eat more than about one albacore tuna sandwich a week, they may exceed the FDA's advisory level. Fresh tuna steaks typically contain higher levels of mercury than canned light tuna and consumption should be similarly limited.  In any event, the FDA warned women and children to consume no more than 12 ounces of fish each week, and tuna are certainly no exception.

Myth: The FDA action level of 1.0 ppm of mercury in fish is a conservative limit.

Fact: The FDA limit is actually among the highest thresholds; it is not the most conservative limit. Many countries have even lower, more protective thresholds including Thailand and India (0.5 ppm), Japan (0.4 ppm), and the United Kingdom and China (0.3 ppm.) In the United States, the risk-based action levels recommended by the Environmental Protection Agency for recreationally caught fish are much more conservative due to the assumption that recreational fish-eaters may consume more fish than the average person. Using EPA risk-based procedures, many states set action levels for recreationally caught fish at 0.3-0.5 ppm. Even the National Research Council in the United States has recommended 0.5 ppm.

It should be noted that the FDA action level targets the average adult consumer and balances risks to human health with economic and other considerations. EPA action levels, on the other hand, are based solely on protecting the health of humans and wildlife.

The FDA is not the only agency using the higher, and less protective 1.0 ppm figure. The levels set by the World Health Organization and the United Nation Food and Agriculture Organization, the Philippines and Australia for predatory fish are exactly the same, 1.0 ppm. With the exception of Croatia (1.5 ppm),there are few if any thresholds that are higher than the FDA's 1.0 ppm figure.

Myth: Studies show that mercury has no effect on women and children who eat fish.

Fact: In 2000, the U.S. National Academy of Sciences reviewed 237 studies on mercury toxicity, including the Seychelles study which is often quoted as showing no effects. They determined not only that the Seychelles population was a poor example for U.S. fish consumers but that the vast majority of studies conducted around the world have proven the detrimental impact of mercury-heavy diets. Effects on humans include neurological and developmental effects as well as heart disease, increased risk of heart attacks and infertility.

Myth: Environmental groups like Oceana just want people to stop eating fish.

Fact: Actually, the opposite is true. Oceana is working to ensure that fish remains available and safe to eat now and in the future. Oceana and other groups are concerned about public health and ocean health, and both are in jeopardy as a result of mercury contamination. People should continue to eat fish, but they should be able to do so without running the risk of being poisoned. By trying to eliminate a major source of mercury pollution, Oceana is working to rid the fish of mercury, so that fish can remain an important part of our diets.

Myth: Not eating fish will limit a person's consumption of Omega 3 fatty acids - which recent studies have shown to benefit the heart and reduce the inflammation that triggers asthma.

Fact: Oceana recommends seeking safe Omega 3 sources, and is working to reduce mercury in fish, so that people are not forced into making a choice between mercury poisoning and fatty acids. Omega 3s are found in many fish that have low concentrations of mercury, and fish oils can be used as a supplement, as long as they come from species with low mercury levels. In addition, Omega 3s are found in a variety of other sources, including fennel seeds and walnuts. The type of fatty acid in plants is somewhat different, but in most cases the body can convert it to the type found in fish. Furthermore, research has shown that high levels of mercury, which have been linked to increased risk of heart attack and heart disease, can cancel out the benefits of Omega 3 fatty acids. It is impossible to generalize about whether Omega 3s are more important than minimizing mercury.

Myth: Mercury occurs naturally and therefore is not a problem.

Fact: Regardless of its origins, mercury, like many other things found in nature, is dangerous. Scientists estimate that 50 to 75% of the mercury now in the environment comes from human sources such as coal-burning and chlorine production, while the remainder is a product of natural emissions. Studies also have shown a two- to four-fold increase in mercury concentrations in air and marine surface waters since the pre-industrial era.

Myth: The U.S. Centers for Disease Control and Prevention recently said that the number of women whose blood mercury level exceeds the reference dose is lower than previously thought, possibly as low as 6%.

Fact: There continues to be debate about the exact figure; however, by any account the number of women and children that are exposed to dangerous levels of mercury is too high. In the case of the most recent CDC study, its authors acknowledge that their figure may be an underestimate. The exact number of women at risk is difficult to pinpoint, and there is a range of estimates in the literature. The CDC study showed that approximately 6 percent of women in the United States have mercury levels above the threshold believed by EPA and others to affect the developing fetus. This compares to a study conducted by a scientist at the EPA which places the estimate at 15.7 percent and a recent Greenpeace estimate - based on testing of actual hair samples - of 21 percent. However, the CDC study itself acknowledges that it is assuming a 1:1 ratio between mother's blood and umbilical cord blood, which they acknowledge may not be correct. Recent science suggests the ratio is closer to 1.7 :1 -- a full 70 percent higher - but that the range could go as high as 3:1 - which would be even higher still. Using the mid-range ratio would effectively double the percentage in the CDC's findings, making the numbers more comparable and bringing the CDC figure far closer to EPA's estimate.

Developing precise estimates of risk is difficult and is never an exact science. Estimates can vary depending on a variety of assumptions, years studied, and other variables. Studies have predicted a range of cord blood to maternal blood ratios and female blood mercury levels which, when compared to population figures available from the U.S. Census Bureau, all place the number of newborns at risk in the hundreds of thousands for the United States population alone. This does not consider the additional number of newborns at risk in other countries where similar risk levels are likely to occur.

Myth: Mercury is not that dangerous; there are other chemicals out there that are worse.

Fact: Mercury is the only chemical for which the FDA has issued a health advisory for fish. The U.S. EPA reports over 2,300 recreational fish advisories in the United States for 2003, all because of mercury. No other chemical has caused nearly that many advisories. There are chemicals that, pound for pound, are more toxic than mercury, but the risks posed by a chemical are dependent on that chemical's availability, that means whether it is in the food we eat, in the air we breath, for example. Because of mercury's chemistry, it is among a short list of chemicals that bioaccumulate. Because it is also toxic, it is one of the most dangerous chemicals in our environment.

The Minnesota Pollution Control Agency developed an indexing system to compare the potential environmental impact of toxic substances emitted into the air. The system calculates an index value based on both the environmental fate of a substance and its toxicity. Mercury scores high in both categories because 1) it doesn't degrade and has a tendency to bioaccumulate in food chains; and 2) it is a potent neurotoxin. In a relative ranking of 183 substances, only dioxin is a greater environmental hazard for equivalent amounts released into the air.  However, it is unlikely that the amounts of mercury released to the air could ever be rivaled by dioxin emissions.

Myth: Contaminated fish cannot be legally sold.

Fact: The FDA does not pull fish off the market when they exceed the warning levels. In fact, most fish are not even tested to determine the level of mercury they contain prior to being sold. FDA advisories are based on a limited amount of testing data, and the result of high mercury levels is simply to issue an advisory, not to pull fish out of the stores.

Myth: It is not feasible to convert mercury-cell chlorine plants to newer technology—it would force plants to shut down.

Fact: Conversion is both possible and practical. Many plants have successfully converted and totally eliminated mercury releases. In fact, according to the industry converting tends to reduce costs.  Companies have saved as much as 15% on electric and 10% on total energy costs. Furthermore reductions in waste generation can also save companies money after switching.  When Occidental Chemical converted its Mobile Plant they reduced hazardous wastes by 92%. Plants don’t always need to shut down when they convert, which means they can minimize down time. One plant in Austria that converted in 1999 did so while operating at 80% capacity, avoiding major losses in production.

Myth: The type of mercury released by mercury-cell chlorine factories is not the same as the mercury in fish, and therefore reducing emissions will not help reduce mercury levels in fish.

Fact: Mercury released by chlorine factories can be converted to methylmercury in the environment.  Industrial mercury releases, including those from the chlorine industry, start out as an inorganic or elemental form of mercury. It is well recognized that when mercury is deposited in water, either directly or in runoff, bacteria convert it to methylmercury through a process called methylation. Because methylmercury builds up in animal tissue, this form is the one that becomes problematic from a health standpoint. Methylmercury bioaccumulates, reaching high levels in large predatory fish. While it is true that mercury is in a different form when it is released, release is the first step in the process of contaminating fish. The methylmercury in fish started out as elemental or inorganic mercury, the same type that is released by chlorine factories.  In the absence of inorganic mercury, methylation of mercury could not occur.

One way to reduce both forms of mercury in the environment is to alleviate the unnecessary use and release of mercury. Mercury-cell chlorine factories use an outdated technology to produce chlorine. The process requires the continued use of new mercury and large emissions of mercury into the environment. By converting to mercury-free technology, mercury can remain where it belongs…underground.

Myth: U.S. (and European) mercury-cell chlorine plants are a miniscule part of the U.S. and global mercury problem.

Fact: The U.S. is the second largest consumer of mercury in the world, according to a United Nations assessment. U.S. mercury-cell chlorine plants still consume more elemental mercury than any other industry, even though most of the chlorine industry has switched to cleaner technologies. Their annual demand for tons of pure elemental mercury causes more and more new or recycled mercury to enter the environment every year. The mercury-cell chlorine plants emit tons of elemental mercury (Hg0) and reactive mercury (Hg(II)) to the atmosphere every year. Some (5-10%) of the reactive Hg(II) gets deposited within 100 km of the plant and the rest is carried further away. Emissions of elemental mercury enter the global atmospheric pool. Industry wastes containing mercury can continue to contaminate local environments and waterways for decades after plants convert to mercury-free technology.



Questions? Email mercury@oceana.org or call 877-7OCEANA.