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Mercury Poisoning
What is mercury? - Mercury is a naturally occurring element that is found in air, water and soil. However, human activities have also contributed greatly to the amount of mercury released into the environment.
There are three basic types of mercury that can be found in the environment: elemental mercury, mercury salts, and organic mercury compounds.
Elemental mercury
- This is the kind of mercury, also known as quicksilver, is found in thermometers. It has a bright silver color and is a liquid at room temperature.
Mercury salt - A mercury salt is formed when mercury forms bonds with other elements like oxygen, chlorine, or sulfur.
- Mercury salts tend to be powders or crystals at room temperature.
- Mercury salts are also known as inorganic mercury.
Organic mercury - An organic mercury compound results when mercury forms bonds with carbon. An example of organic mercury is methylmercury.
- In the past, certain organic mercury compounds (ethyl- and methyl- mercury) were used to eliminate molds from grain stores. This use was banned in the 1970s due to the possibility that humans may accidentally eat the contaminated grains and suffer negative health effects.
- Most of the mercury wastes that are released into the environment are inorganic, not organic mercury. However, certain bacteria in water can transform inorganic mercury to organic mercury.
- As various fish and shellfish eat these bacteria, the amount of organic mercury gets concentrated in the meat of the fish as we move further up the food chain. This results because methylmercury is poorly eliminated from the body and tends to accumulate in the body over time (ie. bioaccumulation).
Mercury can be released into the environment by: - Burning of coal
Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the United States, accounting for over 40 percent of all domestic human-caused mercury emissions.
- Burning of city waste
- Industrial dumping
How can my child be exposed to mercury?
- Because it is found naturally in the environment, almost everyone will be exposed to very low levels of mercury in air, water, or food. However, some people may be exposed to higher levels of mercury from food, dental fillings, air, water, soil, medicinal products, and cultural practices:
Food
- The most likely way that most people will be exposed to higher levels of mercury is from eating fish or shellfish contaminated with methylmercury.
- Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish.
- Fish and shellfish are the main sources of methylmercury exposure to humans. Methylmercury builds up more in some types of fish and shellfish than others. Large predator fish that feed on smaller fish, such as swordfish and tuna, accumulate the most mercury.
- Several studies have consistently demonstrated that populations who eat fish tend to have higher levels of methylmercury than the EPA’s reference dose level. Exposures below the reference dose are considered unlikely to cause harm in humans.
- Fish is an excellent source of protein and can be high in omega-3 fatty acids. Omega-3 fatty acids found in seafood are essential to neural development.
- However, methylmercury is known to cross from a pregnant mother’s blood into the bloodstream of the developing child. Fetuses and young children are most susceptible to the neurotoxic effects of mercury.
- The Environmental Protection Administration (EPA) and the Food and Drug Administration (FDA) issued an advisory in 2004 telling pregnant women to avoid eating more than 340 grams of fish, about 12 ounces (2 seafood servings) a week.
However, there is growing evidence that very low fish consumption can actually be harmful to an unborn child and that the benefits of fish intake for women of childbearing age outweigh the potential risks if a modest fish intake (2 seafood servings/wk) is consumed:
- A 2006 study, published in JAMA, reviewed reports published through April 2006 that evaluated the effects of methylmercury and fish oil on early neurodevelopment in infants and children.
- The review suggests that the benefits of fish intake for women of childbearing age outweigh the potential risks if a modest fish intake (2 seafood servings/wk) was consumed, except for certain species of fish.
- Also, a study published in the February 2007 edition of Lancet of over 11,000 pregnant women in the UK examined neurodevelopmental outcomes in children whose mothers ate varying amounts of seafood while pregnant.
- The researchers used the Avon Longitudinal Study of Parents and Children to assess possible benefits and disadvantages of seafood consumption. The study relied on mothers’ observations of their children’s development and their reports of their food intake while pregnant.
- While it has been suggested by the EPA and FDA that pregnant women should limit their consumption of seafood to 340 grams per week (2 seafood servings/wk), the researchers found that there were beneficial effects on child neural development with maternal consumption of seafood over 340 grams.
- Furthermore, they showed that seafood intake of less than 340 grams per week was associated with increased risk of children being in the lowest quartile for verbal IQ and having low communication and social development scores compared with mothers who ate more seafood.
For information on the best and worst fish alternatives with regard to mercury and other contaminants, see the Oceans Alive campaign of Environmental Defense website at http://www.oceansalive.org/eat.cfm?contentID=4004. After the Q&As at the bottom you will click on the list of fish species.
Advice:
- Choose fish low in mercury and high in omega-3 fatty acids.
- Pregnant women, women of childbearing age, nursing mothers, and young children should completely avoid shark, tilefish, swordfish, and king mackerel because they contain high levels of methylmercury, and should limit consumption of other mercury-containing fish.
- For pregnant women and women of childbearing age, there is growing evidence that very low fish consumption can actually be harmful to an unborn child. As with any study based on self-reporting methods the results cannot be considered entirely definitive; therefore, further studies are needed.
- The FDA has reviewed the results of the Lancet study and for now has made no changes to their current information regarding pregnant women and seafood consumption.
- In the meantime, the best course of action would be to eat certain species of fish (provided by link above) in moderation (2-3 servings per week).
Dental Fillings
Breathing mercury vapors from dental fillings is another common source of mercury exposure.
However, the level of mercury from this type of exposure is very minimal and is unlikely to be associated with any negative health effects.
The U.S. Public Health Service has recommended that people do not remove dental fillings simply to reduce mercury exposure.
Air
As stated, most of us our exposed to very low background levels of mercury in the air. City air generally contains higher levels of mercury than rural air, but both levels are still very low.
Higher-level exposure from the air is more likely near certain hazardous waste sites, city incinerators, or facilities that burn coal and other fossil fuels.
Broken thermometers Children may break open a thermometer in order to play with the bright silver mercury droplets. Upon spilling, the droplets will bead up and spread easily.
Liquid mercury evaporates at room temperature and these vapors are invisible, odorless, and, at high levels, are very toxic.
Children who breathe vapors from such mercury spills may be exposed to high levels of mercury.
Mercury vapors are easily absorbed through the lungs into the bloodstream and are therefore, particularly hazardous.
Mercury vapors are also heavier than air and may linger in higher concentrations close to the floor.
Children who crawl or play in these areas are at highest risk of breathing these vapors.
Water
The levels of mercury in most sources of drinking water are very low.
Higher exposure levels are possible if there is mercury runoff from mercury-containing sites into the drinking water sources.
Soil Background levels of mercury in most soils are very low.
It is possible to have higher levels of exposure from contact with mercury-contaminated soil in hazardous waste sites or other sites polluted with high levels of mercury. This exposure may be through the skin or through the gastrointestinal tract.
Increased exposure from contaminated soil may be a problem for kids living in areas contaminated with mercury.
Compared with adults, they have a greater tendency to eat dirt and explore their environments with their mouths.
Medicinal products Certain medicinal products like skin creams may contain small levels of mercury that may be absorbed across the skin.
Despite the health risks, so-called "skin-lightening" products that contain mercury are used in many parts of the world, and many are illegally imported into the United States.
Some Chinese herbal products contain mercury
Vaccines
Over the years thimerosal, a preservative that contains ethyl mercury, has been used in certain vaccines.
No harmful effects have been reported from thimerosal at doses used in vaccines, except for minor reactions like redness and swelling at the injection site.
Children receive the bulk of their vaccinations in the first six months of life, and so those exposed to mercury through vaccination experienced the largest burden during this period.
For normal weight babies, this exposure did not exceed maximum limits. For premature babies, however, who are generally underweight, this mercury burden could have exceeded maximum limits.
This raised concern that the early mercury loads might have placed children at risk of developmental problems such as autism; however studies have not demonstrated this association.
Despite these study findings, in July of 1999, the U.S. government asked vaccine manufactures either to reduce or eliminate thimerosal from vaccines as a precautionary measure. The manufactures decided to replace thimerosal with a mercury-free preservative to relieve any remaining concerns.
As of 2005, with the exception of some Influenza (flu) vaccines, none of the vaccines used in the U.S. to protect preschool children against 12 infectious diseases contain thimerosal as a preservative.
Regarding more recent vaccine research:
1. Study published in 2004 in the journal, Pediatrics, reviewed all research publications reporting original data that were published between 1966 and 2004 that examined for an association of thimerosal-containing vaccines and autism, autism spectrum disorders and neurodevelopmental disorders.
- Of the published literature identified by this study, the majority of the studies did not demonstrate an association between thimerosal-containing vaccines and autism. A small number of studies suggesting an association were found to be of poor quality with flaws that made interpretation impossible.
2. A separate study published in 2004 in the journal, Pediatrics, sought to answer the question, did thimerosal exposure cause developmental disorders in young children?
This study analyzed data about the children born to 14,541 women from Avon, England in 1991 - 1992.
The researchers collected information on childhood behavior and development from questionnaires administered to the mothers.
They evaluated 12, 956 children who were singleton births that survived to at least a year of age and on whom they had valid information on thimerosal exposure.
The researchers also examined other factors that could affect childhood behavior and development, such as birth weight, gender, maternal education, maternal smoking, breastfeeding, and ethnic origins.
Subsequently, they also considered the effects of maternal fish consumption (another source of mercury) on the children studied.
When taking into account only thimerosal exposure, only 1 result of 69 evaluations suggested that poor social behavior at 47 months of age could have been associated with thimerosal exposure at 3 months of age. However, the results of 8 other evaluations suggested a beneficial effect.
Bottom line: This study showed no evidence of any harmful effect of thimerosal-containing vaccines on neurologic or psychological outcome.
The findings of this, and an increasing number of other studies, should provide reassurance to families and others that there continues to be no evidence of a relationship between developmental problems and thimerosal-containing vaccines.
3. A study published in 2003 in the journal, Pediatrics, sought to answer, did children exposed to differing amounts of thimerosal develop at the right ages? - Scientists looked for neurodevelopmental disorders (e.g. autism, speech problems) in children immunized with vaccines containing varying amounts of thimerosal at three health maintenance organizations (HMOs).
- Researchers conducted the study in two phases. In the first phase, they analyzed 124,170 children who were born from 1991 through 1999 at 2 HMOs for many aspects of child development.
- Data from these HMOs suggested that thimerosal could be associated with tics and speech and language disorders.
- However, in the second phase of the study, which included 16,717 children at a third HMO, this association was not demonstrated.
- In none of the three HMOs was there any evidence of an association between thimerosal-containing vaccines and autism.
- The researchers concluded that there was no significant association between thimerosal-containing vaccines and neurodevelopmental outcomes, but further studies are needed.
Cultural practices
- Certain cultures have been known to use elemental mercury in folk remedies or religious practices.
- There are documented cases of children who have been exposed to high levels of mercury in the context of these practices or from misuse of mercury-containing objects used in these practices.
What are the health effects of mercury exposure?
Mercury exposure at high levels can harm the brain, heart, kidneys, and the lungs of people of all ages.
Research shows that most people’s fish consumption does not cause a health concern. However, it has been demonstrated that high levels of methylmercury in the bloodstream of unborn babies and young children may harm the developing nervous system, making the child less able to think and learn.
The factors that determine how severe the health effects are from mercury exposure include:
• the chemical form of mercury - elemental (metallic), inorganic compounds, or organic compounds
• the dose -- how much
• the duration of exposure -- how long
• the route of exposure -- eating, breathing, injecting, touching
• other chemical exposures
• the specific characteristics of the person - age, health
We will discuss these effects in terms of the specific type of mercury (elemental mercury, inorganic mercury salts, and organic mercury compounds) and the level of exposure (high-level vs. low-level).
- Elemental Mercury (e.g., exposure to mercury from a broken thermometer)
Acute, high-level exposure
Such exposure may cause the following health effects within a few hours:
• personality changes (irritability, shyness, nervousness)
• confusion
• problems with hearing
• problems with vision
• tremors or chills
• headache
• nausea and vomiting
• cough and chest tightness
• difficulty breathing
• damage to kidneys
Chronic, lower-level exposure
Such exposure may cause the following health effects:
• inability to sleep
• emotional instability
• forgetfulness
• tremor
• loss of appetite
• reddening of the palms
• increased saliva production
• increased sweating
• damage to kidneys
Mercury Salts (inorganic mercury) (e.g., exposure to folk medicines containing mercury)
Acute, high-level exposure
Such exposures may have the following negative health effects:
• Serious irritation, bleeding, and possible tearing of the digestive tract
• Collapse of the circulatory system
• Serious damage to the kidneys
Chronic, lower-level exposure
Such exposures may result in the following health effects:
• Skin rash
• Swollen, painful arms and legs
• Problems with nerves in the arms and legs
• High blood pressure
• Damage to kidneys
Organic Mercury (e.g., exposure to contaminated fish)
Acute, high-level exposure
- There have been several documented episodes of widespread mercury poisoning.
- One occurred in Iraq in 1971 when thousands of people were acutely poisoned from accidentally eating grain that contained methylmercury and was meant for planting, not for consumption.
- Some of these Iraqi mothers had serious problems with vision and even blindness attributed to the exposure.
- Iraqi mothers with or without such health problems from this type of mercury exposure gave birth to children with the following health problems:
• Mental retardation
• Problems with vision
• Problems with hearing
• Seizures
• Problems with coordination
• Delays in walking
Chronic, high-level exposure
- A major episode of this type occurred during the 1950’s in Minimata Bay and Niigata, Japan.
- In these areas, local people ate a large amount of fish contaminated with methylmercury.
- This contamination resulted from industrial dumping of mercury-containing waste into local waters.
- Unlike the exposure in Iraq, those in Japan occurred over a span of years.
- Mothers with little or no health problems from this exposure gave birth to children with the following health problems:
• Mental retardation
• Problems with swallowing and sucking
• Problems with walking
• Problems with speech
• Abnormal reflexes
Chronic, low-level exposure
- Several studies have examined the health effects of this type of exposure on children of mothers who ate fish from waters contaminated with methyl mercury.
- The evidence concerning the health effects of these levels of methyl mercury exposure is conflicting. Some studies demonstrate health effects while others do not.
- None of these studies has shown the same type of obvious developmental disabilities as the exposures in Iraq or Japan. However, some of these studies have demonstrated more subtle developmental problems such as:
• problems with coordination
• problems with memory
• problems with language development
• problems with attention
How is mercury poisoning diagnosed and treated?
If you believe that your child has been exposed to mercury and has symptoms consistent with mercury poisoning, call your pediatrician immediately for evaluation and testing.
Testing is the only definite way to determine if mercury is the cause of the symptoms.
Mercury poisoning can be diagnosed by special blood and urine collection tests. These test are not routine and it may take some time to get the results back.
If levels are high, there is treatment. Medication can be administered to help bind the mercury and increase removal of it from the body.
This treatment should be done in consultation with a medical toxicologist.
Symptoms do not always correspond to mercury levels. Many patients with high levels do not have severe symptoms.
If mercury levels are going to be tested, it is important NOT to eat any seafood products for at least 2 days before testing. Eating seafood will cause misleading high levels.
If you believe that your child has been exposed to mercury and has symptoms consistent with mercury poisoning, call your pediatrician immediately for evaluation and testing.
What can I do to limit mercury exposure to my child? If you are a pregnant mother, eliminate or limit fish caught from contaminated waters from your diet.
Check with your state’s health department information concerning mercury contamination of your local waters.
If your cultural or religious practices involve the use of elemental mercury, consider stopping this practice because of the health risks involved. If you choose to continue, only use the elemental mercury in well-ventilated areas and keep mercury-containing items securely stored away from children.
Thermometer break
Before beginning the clean up, change into old clothes and shoes that can be thrown away if they get contaminated with mercury.
If you are wearing gold jewelry, either remove the jewelry or wear good protective gloves. If the liquid mercury contacts the gold jewelry, the mercury bonds permanently to the gold and ruins it. Wearing gloves is a good idea to prevent mercury from lodging under the fingernails while cleaning.
Increase ventilation in the room with outside air and close the room off from the rest of the house. If available, use fans for at least one hour to help ventilate the room.
Pick up the mercury with an eyedropper or scoop up beads with a piece of heavy paper (e.g., playing cards, index cards).
Wide sticky tape such as duct tape can also be used to pick up any glass particles and mercury beads.
Powdered sulfur (which can be purchased at garden supply stores) can be used to bind any remaining mercury. When the sulfur combines with mercury the sulfur turns from the usual yellow color to brown. Continue to use sulfur until there is no longer a color change. Keep in mind that sulfur can be irritating to the skin, nose, throat and eyes. Sulfur may also stain fabrics.
Place the mercury, contaminated instruments (dropper/heavy paper) and any broken glass in a plastic zipper bag.
Place this zipper bag in a second zipper bag and then in a third zipper bag (triple bag), tightly sealing each bag with tape. Place the bags in a wide-mouth, sealable plastic container.
Throw away everything that may have been exposed to the mercury including towels, bedding, clothes if they were contaminated.
Call your local health department for the nearest approved mercury disposal location. If disposal at such a location is not possible, dispose of the plastic container according to state and local requirements.
If weather permits, leave windows open for approximately two days to make sure the area is completely ventilated.
Wash hands very well with soap and water afterwards. Shower well if you think any mercury touched other parts of your body.
Never sweep the area with a broom. Sweeping breaks the mercury into smaller droplets, further contaminating the room and the broom.
Never use an ordinary household vacuum cleaner to clean up mercury. Vacuuming vaporizes the mercury and increases the concentration of mercury in the air that can result in poisoning.
Never pour mercury down the sink drain. It may stay in the plumbing.
Never wash mercury contaminated clothes in the washing machine. Mercury can contaminate the washing machine.
Never walk around if your shoes or socks may be contaminated with mercury. That will spread the mercury droplets all over the house.
Never use household cleaning products to clean the spill, particularly products that contain ammonia or chlorine. These chemicals will react violently with mercury, releasing a toxic gas.
Contact your local health department immediately for help with mercury spills larger than a teaspoon. These spills need special cleanup attention.
Also, you can contact the Poison Control Center at 1-800-222-1222 with any questions.
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