Mercury Isn't Just a Hazard for Young Children, It's a Health Risk for Adults Too

The Environmental Protection Agency recently created the first-ever national standards to limit mercury pollution from coal-fired power plants. Mercury is a potent toxin that interferes with the human nervous system. Reducing this hazard will be a major public health breakthrough.

Mercury is most commonly recognized as a developmental toxin, threatening to young children and fetuses as they develop their nervous system. Prenatal exposure to even low levels of mercury can cause life-long problems with language skills, fine motor function, and the ability to pay attention.

But mercury is also a danger for adults. This reality was brought home to me when I was recently talking with a colleague of mine – a 38 year old man – who ate a lot of fish as part of low-fat, healthy diet. He said that during a routine medical exam, his doctor ordered blood work and decided to include a test for mercury.

When the results came back, he was astonished to learn he had mercury poisoning. He had never worried about mercury contamination before, nor did he realize the particular fish he loved to eat could endanger him. Luckily his doctor caught the problem before neurological symptoms had set in and offered treatments that brought his mercury levels down.

In grownups, mercury can cause memory loss, tremors, vision loss and numbness of the fingers and toes. It can also adversely affect fertility and blood pressure regulation, and a growing body of evidence suggests that exposure to mercury may lead to heart disease.  Fewer people know about these risks than those posed to the developing child.

A hundred years ago, adult mercury poisoning was well recognized.  In fact, the phrase “mad as a hatter” was coined because hat makers were poisoned by the high levels of mercury used in felt processing; these workers developed a strange, uneven gait as well as strange alterations in their personalities – traits that resembled mental instability.  Today, we have the Occupational Health and Safety Administration to protect people from workplace hazards and have eliminated most of the uses of mercury in products and industrial processes. 

Mercury contamination continues.  Coal-fired power plants are the largest industrial source of mercury. The mercury they release gets deposited in waterways, where it is converted into methylmercury and ingested by fish. When we eat these fish, we absorb methylmercury into our own bloodstream.

The contaminant is so ubiquitous that all 50 states advise people to avoid eating fish from certain contaminated waters. But still many Americans eat fish high in mercury. Whether they catch it themselves to provide food for their families or they get it from sushi restaurants as an alternative to red meat, people young and old are being exposed to mercury more than they realize.

For this reason, doctors should routinely test their patients for mercury poisoning.  When physicians ask about risk factors, like whether their patients smoke, drink alcohol, or exercise, they should also ask if we eat a lot of fish. Patients may not realize that some symptoms they are experiencing could come from mercury poisoning. Testing of high risk patients could open the door to treatment and recovery.  

The good news is that unlike many toxins, the body can excrete mercury, which is not stored in our fat tissues.  Once people stop eating mercury contaminated fish, they can start healing themselves. This easy fix is a big reason more doctors should routinely test their patients who eat certain fish.

NRDC will continue to fight to reduce sources of mercury pollution both here and abroad; it is one of our highest priorities.  Until the results of this work shows up in the fish in our food supply, we need doctors to scan for mercury poisoning problems in their patients and recommend actions to reduce their risks of neurological and other problems.

Meanwhile, people can still eat fish and protect themselves from mercury; they just have to make smart choices. Because mercury bio-accumulates—gets carried up the food chain—bigger fish tend to have higher amounts than small fish. You can protect yourself by eating fewer servings of tuna, ahi, and swordfish and opting instead for squid, mussels, mackerel, sardines, and anchovies; keep NRDC's Mercury in Fish Wallet Card handy for reference.