Mercury Levels in Fish Remain ‘Unchanged’
- New research published in the journal Environmental Science and Technology Letters indicates that mercury levels have not significantly decreased in tuna fish despite global efforts to reduce mercury emissions in the environment. The data found that mercury levels in the oceans’ tuna population have remained the same in the last five decades.
- Researchers attribute the unchanging mercury levels in fish to “legacy mercury” previously absorbed by the ocean before efforts were made to reduce it in the air. The legacy mercury is still impacting fish today and may continue for years to come.
- According to the Environmental Protection Agency (EPA), “No human data currently ties mercury exposure to cancer, but the data available are limited. In very high doses, some forms of mercury have caused increases in several types of tumors in rats and mice.” Other credible research published in scientific journals suggests more research is needed to determine a definitive link between mercury and cancer.
- Mercury levels found in most fish are at “chronic low-dose,” meaning you would have to eat a great deal of fish to pose a significant health risk.
- The environment and foods you eat, combined with your genetics, can all influence your cancer risk. People can make some dietary choices to reduce their cancer risk, such as eating more vegetables and limiting red meat.
Tuna is eaten by millions of Americans each year, and with such fishy cravings comes the risk of consuming mercury, which these fish are known to possess. Mercury is a type of metal naturally found in rocks and the oceans, which is how fish absorb it. Health concerns arise when too much mercury is consumed by people eating fish.
Human consumption of methylmercury from fish has been linked to cardiovascular disease, according to research published in the New England Journal of Medicine. However, a direct link of mercury causing cancer is less clear due to inconclusive and insufficient research available.
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Predatory fish are more likely to contain higher amounts of mercury compared to fish lower on the food chain. The U.S. Food and Drug Administration lists general mercury exposure in fish. Fish such as shrimp, which has “0.009 mercury concentration parts per million (PPM),” tuna, which contains “0.689 mercury concentration PPM,” and sharks, which contain “0.979 mercury concentration PPM.”
Helping You Understand How Your Environment Impacts Your Health
Efforts to Reduce Mercury Emissions
The study published in Environmental Science and Technology examined nearly 3,000 tuna fish caught in the world’s oceans (Pacific, Atlanta, and Indian) between 1971 and 2022. The mercury levels within the fish were examined during the five-decade period.
It should be noted that during the early 1970s, global efforts began to ramp up to reduce mercury emissions. In the U.S., the U.S. Clean Air Act and the EPA were enacted to help with this effort.
However, although mercury pollution in the air has decreased, mercury levels in the ocean’s fish population remained stable. The unchanged mercury levels are attributed to the “legacy mercury” previously absorbed by the ocean before efforts were made to reduce it in the air. As the legacy mercury circulates deeper into the ocean through ocean currents, it continues to impact fish it comes into contact with up to the present day. It’s estimated that the legacy mercury will take another decade or two to filter out of the ocean.
“This legacy mercury could have been emitted years or even decades earlier, so it wouldn’t reflect efforts to clear airborne mercury emissions,” the research team surmised.
So, with the possibility of mercury still persistent in fish populations for years to come, is it safe to eat and avoid health risks? Like with most foods, there is no significant risk when consumed in moderation. As previously mentioned, mercury levels found in most fish are at “chronic low-dose,” meaning you would have to eat a great deal of fish to pose significant risk.
A 2009 study published in “Cases” examined two Caribbean men who experienced low-level mercury poisoning. The men were middle-aged and in relatively good health when they started experiencing back pain, fatigue, and weight loss for 8 to 12 months. Both men ate fish quite often, and when they stopped eating fish, their symptoms subsided.
The EPA concluded that environmental exposures to inorganic mercury and methylmercury “are not likely to cause cancer in humans” in its 2005 Cancer Guidelines. Of course, ongoing research is still needed to conclusively say if elevated exposure to mercury causes cancer in humans.
Researchers who sought to examine research attempting to link mercury and cancer noted that “While some epidemiological studies have observed a strong association between environmental/occupational (mercury) Hg exposure levels, measured in blood, toenail, and hair, and cancer risk and mortality, others failed to reveal any association.”
They add that the data regarding mercury and cancer in people remains “inconsistent” to say for sure.
How the Environment, Diet, and Genetics Influence Your Cancer Risk
What causes cancer to develop depends on a myriad of factors, from family genetics, your diet and exercise habits, or environmental factors like exposure to chemicals in the air, water, or food you consume.
“We create carcinogens all the time in our foods when we cook them, and very few of us get cancer because our bodies can handle them,” Dr. Robert Wright, chair of the Department of Environmental Medicine and Public Health at Mount Sinai, tells SurvivornNet.
“But some people have susceptibilities to these environmental carcinogens, which might be genetic or might be caused by combinations of carcinogens,” Dr. Wright continued.
Of course, not everyone develops cancer when exposed to certain environmental or genetics are taken into consideration. This problem is why cancer research is continually needed.
“What we haven’t figured out for cancer is, what is the combination of risk factors that end up leading to a particular person getting cancer,” Dr. Wright said. “The goal [in the future] is to identify those people who are more susceptible to cancer and to give them counseling and foods that they can eat and other habits like exercise that can reduce their risk. Right now, we’re not really good at predicting that.” Dr. Robert Wright, chair of the Department of Environmental Medicine and Public Health at Mount Sinai, tells SurvivornNet.
Dr. Wright encourages us to eat a well-balanced diet and maintain physical activity.
WATCH: Can diet affect cancer risk?
“In the end, prevention is actually kind of simple,” he said. “It’s what we always know. It’s exercise and eat well. That means eating more vegetables and less meats, particularly red meats.”
Some dietary basics to avoid a higher cancer risk include:
- If you can afford it, buy organic fruits and vegetables
- When buying non-organic, make sure to wash produce thoroughly
- Avoid overcooking food
- Try to eat fewer red meats
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