Most College Students Are Not Aware of Mercury Exposure Risk of Eating Large Amounts of Tuna

Tim Stephens wrote . . . . . . . . .

A surprising number of students eating in university dining halls have been helping themselves to servings of tuna well beyond the amounts recommended to avoid consuming too much mercury, a toxic heavy metal.

Researchers at UC Santa Cruz surveyed students outside of campus dining halls on their tuna consumption habits and knowledge of mercury exposure risks, and also measured the mercury levels in hair samples from the students. They found that hair mercury levels were closely correlated with how much tuna the students said they ate. And for some students, their hair mercury measurements were above what is considered a “level of concern.”

“It doesn’t necessarily mean that they would be experiencing toxic effects, but it’s a level at which it’s recommended to try to lower your mercury exposure,” said Myra Finkelstein, an associate adjunct professor of environmental toxicology at UC Santa Cruz. “Our results were consistent with other studies of mercury levels in hair from people who eat a lot of fish.”

Neurological effects

Tuna and other large fish contain significant amounts of mercury in its most toxic form (methylmercury), and exposure to high levels of methylmercury can cause neurological damage. Because of its effects on neurological development and reproductive health, concerns about mercury exposure are greatest for pregnant women and children. Finkelstein said college students should also limit their exposure to mercury because their nervous systems are still developing and they are of reproductive age.

She said the study was prompted by her experiences teaching students about mercury in the environment and hearing about how much tuna some students eat. “I’ve been dumbfounded when students have told me they eat tuna every day,” Finkelstein said. “Their lack of knowledge about the risk of exposure to mercury is surprising.”

Graduate student Yasuhiko Murata led the study and is first author of a paper on their findings, which has been accepted for publication in Environmental Toxicology and Chemistry and is available online. In the surveys, about a third of students reported weekly tuna consumption, and 80 percent of their tuna meals were at the campus dining halls, where tuna is regularly available from the salad bar. Half of the tuna eaters reported eating three or more tuna meals per week, potentially exceeding the “reference dose” established by the U.S. Environmental Protection Agency (EPA), considered a maximum safe level (0.1 micrograms of methylmercury per kilogram of body weight per day).

Before the results were published, Finkelstein discussed her team’s findings with UCSC administrators who oversee the dining halls. New signs in the campus dining halls will now give students information about mercury in tuna and guidelines for fish consumption. Other changes may be made after a more thorough assessment, said William Prime, executive director of dining services.

Finkelstein said this issue could be a concern for all kinds of institutions with dining halls, especially those serving children, such as boarding schools. “Any time you have a dining hall situation where people are helping themselves, some residents may be eating way too much tuna,” she said.

Servings per week

Nearly all fish contain some mercury, but tuna, especially the larger species, are known to accumulate relatively high levels of the toxic metal. Consumers are advised to eat no more than two to three servings per week of low-mercury fish (including skipjack and tongol tuna, often labeled “chunk light”) or one serving per week of fish with higher levels of mercury (including albacore and yellow fin tuna).

Some of the students surveyed at UC Santa Cruz reported having more than 20 servings of tuna per week. The researchers analyzed the mercury content of the tuna being served in the dining halls, collecting samples periodically over several months, and found that the mercury content was variable, with some samples having five times as much mercury as others.

“Some chunk light tuna was actually quite high in mercury, although typically it has only half or one-third as much as albacore,” Finkelstein said.

The researchers calculated that, to stay below the EPA reference dose, a 140-pound person could consume up to two meals per week of the lower-mercury tuna but less than one meal per week of the higher-mercury tuna.

After conducting an initial survey and hair analysis, the researchers conducted a second survey with more detailed questions designed to probe students’ knowledge about mercury in tuna and recommended consumption rates. Whether they were tuna eaters or not, most students had very little knowledge about this issue, Finkelstein said. A majority of students answered that it is safe to eat two to three times as much tuna per week as is recommended.

“It was not a large sample size, but only one out of 107 students surveyed had a high level of knowledge as well as confidence in that knowledge, so I think it’s important to provide students with more information about safe levels of tuna consumption,” she said.

Recommendations regarding consumption of tuna and other fish are complicated by the fact that fish is highly nutritious and contains beneficial omega-3 fatty acids and other nutrients. In addition, mercury concentrations vary widely among different types of fish. The U.S. Food and Drug Administration and EPA have issued advice on eating fish for pregnant women, parents, and caregivers of young children.

Source: University of California Santa Cruz

Lead, Mercury Exposure Raises Cholesterol Levels

Higher levels of lead and other heavy metals detected in the blood was associated with increased levels of lower density lipoprotein (LDL – bad cholesterol) and total cholesterol, according to preliminary research to be presented in Chicago at the American Heart Association’s Scientific Sessions 2018, a premier global exchange of the latest advances in cardiovascular science for researchers and clinicians.

Researchers reviewed information from NHANES 2009-2012, a national representative database which includes cholesterol levels and blood levels of heavy metals among U.S. adults. They found a notable difference between those with the least blood levels of heavy metal and those with the most, with LDL becoming progressively higher as lead levels increased.

Compared with those who had the lowest levels of a metal, those with the highest:

  • had 56 percent greater odds of having higher total cholesterol if they have the highest level of lead;
  • were 73 percent more likely to have higher total cholesterol if they had the highest levels of mercury in their blood;
  • had 41 percent higher risk of elevated total cholesterol if their cadmium levels were in the highest levels; and
  • were 22 percent more likely to have higher bad cholesterol if they were in the highest lead levels.

In addition, mercury levels increased the odds for higher LDL by 23 percent among those who fell in the middle for their heavy metal levels, compared to those with the lowest level. The rise in cholesterol seen with increasing heavy metal levels in the blood might have cardiovascular consequences in people exposed to heavy metals, such as in areas with disaster water crises. This suggests the need for screening for heavy metals as a risk for high cholesterol and cardiovascular disease, the authors noted.

Source: EurekAlert!

Today’s Comic

Mercury Poisoning

Jon Johnsonwrote . . . . . . . .

What is mercury poisoning?

Mercury is a naturally occurring metal that is in many everyday products, albeit in tiny amounts. While this limited exposure is usually considered safe, a buildup of mercury is highly dangerous.

Mercury is a liquid at room temperature and readily vaporizes into the air around it. It is often a by-product of industrial processes, such as burning coal for power. Vaporized mercury can make its way into the rain, soil, and water, where it poses a risk to plants, animals, and humans.

Ingesting or coming into contact with too much mercury can cause symptoms of mercury poisoning.

Symptoms and early signs

Mercury may affect the nervous system, leading to neurological symptoms such as:

  • nervousness or anxiety
  • irritability or mood changes
  • numbness
  • memory problems
  • depression
  • physical tremors

As the levels of mercury in the body rise, more symptoms will appear. These symptoms may vary depending on a person’s age and exposure levels. Adults with mercury poisoning may experience symptoms such as:

    muscle weakness

  • metallic taste in the mouth
  • nausea and vomiting
  • lack of motor skills or feeling uncoordinated
  • inability to feel in the hands, face, or other areas
  • changes in vision, hearing, or speech
  • difficulty breathing
  • difficulty walking or standing straight

Mercury can also affect a child’s early development. Children with mercury poisoning may show symptoms such as:

  • impaired motor skills
  • problems thinking or problem-solving
  • difficulties learning to speak or understanding language
  • issues with hand-eye coordination
  • being physically unaware of their surroundings

Mercury poisoning tends to develop slowly over time if a person comes into frequent contact with mercury. However, in some cases, mercury poisoning comes on quickly and is associated with a specific incident.

Anyone who experiences a sudden onset of mercury poisoning symptoms should call a doctor or poison control.

Long-term complications

Exposure to high levels of mercury may also put a person at risk for long-term complications, including:

Neurological damage

High levels of mercury in the blood may put a person at risk for long-term neurological damage. These effects may be more pronounced in children who are still developing.

A study in the Journal of Preventive Medicine and Public Health noted that many incidents of mercury poisoning have led to long-term nerve damage, which can cause:

  • intelligence disorders and low IQ
  • slow reflexes
  • damaged motor skills
  • paralysis
  • numbness
  • problems with memory and concentration
  • symptoms of ADHD

Reproductive effects

Mercury poisoning also poses a risk to the reproductive system. It may cause reduced sperm count or decreased fertility and may also cause problems with the fetus.

Possible effects of mercury poisoning include deformity and a decreased survival rate of the fetus, and reduced growth and size of the newborn at birth.

Cardiovascular risks

Mercury helps promote the accumulation of free radicals in the body, which puts the cells at risk for damage. This may lead to an increased risk of heart problems, including heart attack and coronary heart disease.


The most common cause of mercury poisoning is from eating seafood, but people can get mercury poisoning from industrial processing, thermometers and blood pressure machines, dental work, and old paints.

Mercury poisoning from seafood

Eating seafood that has been tainted with mercury is one of the most common ways humans accumulate mercury in their bodies. The mercury in seafood is a highly poisonous form of the metal called methylmercury, which forms when mercury dissolves into the water.

Methylmercury can be absorbed from the water by all sea creatures, but it also continues through the food chain.

Small sea creatures, such as shrimp, often ingest methylmercury and are then eaten by other fish. These fish will now have more methylmercury in them than the original shrimp.

This process continues all the way up the food chain, so that a large fish may contain much more mercury than the fish it has eaten. This does not necessarily make it better to eat smaller fish, however. It is always essential for a person to check the source of their seafood to avoid contaminated fish and shellfish.

People worried about their exposure to mercury may want to limit their seafood intake, particularly of fish that are high on the food chain, such as swordfish, shark, white tuna, pike, walleye, and bass.

Pregnant or breast-feeding women may want to avoid or restrict their intake of fish and shellfish, as any mercury they contain can pass to the fetus or infant through the umbilical cord or breast milk.

Dental fillings

Amalgam fillings, commonly called silver fillings, contain approximately 40 to 50 percent mercury. Amalgam fillings are not often used now, as there are newer and safer alternatives.

Old fillings may increase a person’s risk for mercury exposure. Some people choose to replace their amalgam fillings to reduce their long-term exposure to mercury.

Other causes

Mercury poisoning may also be due to direct or environmental exposure. Mercury exposure may come from one or more of the following sources:

  • mining for gold
  • exposure to some types of jewelry
  • exposure to older paints
  • some vaccinations
  • contact with a broken fever thermometer or older house thermometer
  • toxic air in areas near factories that produce mercury as a by-product, such as coal plants
  • Some skin care products may also be tainted with mercury, though this is uncommon.


Doctors can usually diagnose mercury poisoning through a physical exam and blood tests. Doctors may ask about any symptoms the person is having, as well as for a general breakdown of their diet.

They may also ask questions about the environment the person lives or works in, including whether they live near any factories or work in an industrial plant.

If the doctor suspects mercury poisoning, a blood and or urine mercury test can gauge the levels of mercury in the body.


Treatment of mercury poisoning involves eliminating any and all exposure to the metal. Doctors will recommend that the person does not consume any seafood that contains mercury.

If mercury poisoning is related to a person’s workplace or environmental exposure, doctors may suggest that the person change their environment to reduce their exposure, or that the workplace puts new safety measures in place.

Mercury poisoning may cause some long-term side effects, which will be treated or managed individually.

Certain types of severe cases of mercury poisoning may require chelation therapy. This is the process of removing mercury from the organs so the body can dispose of it.

The drugs used in chelation therapy bind to heavy metals in the bloodstream and are then eliminated in the urine. Chelation therapy comes with its own risks and side effects, so it is crucial to use the medication only when necessary.


Mercury is toxic to humans. There is no standard cure for mercury poisoning, so it is best to avoid exposure to high amounts of mercury when possible.

Eliminating risk factors by making changes in the diet and work or living environment may help reduce the levels of mercury in the body.

It is essential to consult a doctor at the first sign of mercury poisoning, as it can have long-lasting effects. Parents and caregivers should also be aware of the signs of mercury poisoning in children and call a doctor if a child or infant displays any symptoms.

Source: Medical News Today

Mercury in Fish, Seafood May Be Linked to Higher ALS Risk

Eating fish and seafood with higher levels of mercury may be linked to a higher risk of amyotrophic lateral sclerosis (ALS), according to a preliminary study that will be presented at the American Academy of Neurology’s 69th Annual Meeting in Boston, April 22 to 28, 2017. However, fish and seafood consumption as a regular part of the diet wasn’t associated with ALS.

“For most people, eating fish is part of a healthy diet,” says study author Elijah Stommel, MD, PhD, of Dartmouth College in Hanover, New Hampshire, and a Fellow of the American Academy of Neurology. “But questions remain about the possible impact of mercury in fish.”

While the exact cause of ALS is unknown, some previous studies have suggested mercury to be a risk factor for the disease. In the United States, the primary source of exposure to mercury is through eating fish contaminated with the neurotoxic metal.

Often referred to as Lou Gehrig’s disease, ALS is a progressive neurological disease that takes away the ability of nerve cells to interact with the body’s muscles. Early symptoms of the disease can include muscle twitching and weakness in a limb. It typically develops into complete paralysis of the body, including the muscles needed to speak, eat, and breathe. There is no cure for ALS, and eventually the disease is fatal.

For the study, researchers surveyed 518 people, 294 of whom had ALS and 224 of whom didn’t, on how much fish and seafood they ate. Participants reported the types of fish they ate, and whether they were purchased from stores or caught when they were fishing.

Researchers estimated the annual exposure to mercury by looking up the average mercury levels in the types of fish and the frequency that the participants reported eating them. Swordfish and shark are examples of fish that are considered high in mercury, while salmon and sardines typically have lower levels. Researchers also measured the levels of mercury found in toenail samples from participants with ALS and compared those levels to people without ALS.

The study found that among participants who ate fish and seafood regularly, those in the top 25% for estimated annual mercury intake were at double the risk for ALS compared with those with lower levels. A total of 61% of people with ALS were in the top 25% of estimated mercury intake, compared with 44% of people who didn’t have ALS. They also found that higher mercury levels measured in toenail clippings were associated with an increased risk of ALS. Those in the top 25% of mercury levels, based on fish-related intake or toenail clippings, were at a two-fold higher risk of ALS. These findings need to be replicated in additional studies.

The authors emphasize that this study doesn’t negate the fact that eating fish provides many health benefits. However, the study suggests that the public may want to choose species that are known to have lower mercury content and avoid consuming fish caught in waters where mercury contamination is well recognized. More research is needed before fish consumption guidelines for neurodegenerative illness can be made.

Currently, the FDA health recommendations for women of childbearing age and children are to eat two to three weekly meals of species such as salmon or sardines that have low mercury but are also high in nutrients such as potentially beneficial omega-3 fatty acids. The FDA recommends avoiding fish with the highest mercury levels, such as shark and swordfish. Check for waterbody-specific fish advisories when consuming fish caught by family or friends.

Source: American Academy of Neurology

Does Mercury in Fish Play a Role in Lou Gehrig’s Disease (ALS)?

Eating mercury-laden seafood may raise the risk of developing ALS (Amyotrophic Lateral Sclerosis), preliminary research suggests.

The report warns of possible harm from fish containing the most mercury, such as swordfish and shark. It doesn’t suggest a higher risk of ALS from general consumption of seafood.

“For most people, eating fish is part of a healthy diet,” said study author Dr. Elijah Stommel, who’s with Dartmouth College’s Geisel School of Medicine in Hanover, N.H.

“But questions remain about the possible impact of mercury in fish,” Stommel said in an American Academy of Neurology news release.

The study of 500-plus people found that seafood eaters who ate the most mercury-heavy fish may face double the risk of developing ALS.

However, the study only established a link between the two, not a cause-and-effect relationship.

Mercury is a toxic metal that occurs naturally in the environment. It tends to be lower in fish such as salmon and sardines, and the study authors stressed that seafood confers many health benefits. But they suggested paying attention to what type of seafood you eat.

ALS, an incurable neurodegenerative disease, is also called Lou Gehrig’s disease in memory of the legendary baseball player who died from it. It often starts with muscle weakness or twitching and eventually develops into complete paralysis and death.

In the United States, just over 6,000 people are diagnosed with ALS each year, according to the ALS Association.

What causes ALS is unknown, but some research has identified mercury as a risk factor. Americans most commonly encounter mercury when they eat fish that contains it, the researchers pointed out.

For the study, the researchers surveyed 294 people with ALS and 224 without it.

Participants were asked about their seafood consumption and whether they caught it themselves or bought it. The researchers then estimated how much mercury the participants consumed annually. They also tested participants’ toenail clippings for mercury content.

The results: 61 percent of those with ALS were in the top quarter of mercury consumption, compared to 44 percent of those without ALS.

Among regular seafood eaters, people in the top quarter of mercury consumption were at twice the risk of ALS, the researchers determined. People with the highest mercury levels, based on toenail clippings and diet, also had twice the risk, they said.

The U.S. Food and Drug Administration suggests that children and women of childbearing age eat two to three meals a week of fish like salmon, cod and sardines that are high in nutrients and lower in mercury. The FDA recommends against fish like shark, marlin and swordfish because of their higher mercury content.

The study results are scheduled for release at the American Academy of Neurology’s annual meeting April 22-28, in Boston. Research presented at conferences should be considered preliminary until published in peer-reviewed medical journals.

Source: HealthDay

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