ATSDR TOXZINE

MERCURY
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CONTENTS

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5 . . . . . . . . . . . . . . . . . . . . . . . Mercury Overview

6 . . . . . . . . . . . . Mercury and the Environment

9 . . . . . . . . . . . . . . . . . . . . . Exposure to Mercury

13 . . . . . . . . . . . . . . . . . . . Mercury and the Body

15 . . . . . . . . . . . . . . . Health Effects of Exposure

18 . . . . . . . . . . . . . . . . . . . . Mercury and Children

22 . . . . . . . . . . . . . . . Reducing Risk of Exposure

28 . . . . . . . . . . . . . . . . . . . . . . . . . Exposure Testing

29 . . . . . . . . Governmental Recommendations

30 . . . . . . . . . . . . . . . . . . . Additional Information
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5

MERCURY

OVERVIEW

Mercury occurs naturally in the environment and exists in 

several forms. 

These forms can be organized under three headings: metallic mercury (also 

known as elemental mercury), inorganic mercury, and organic mercury. Metallic 

mercury is used in a variety of household products and industrial items, including 

thermostats, fluorescent light bulbs, barometers, glass thermometers, and some 

blood pressure devices. Additionally, some religions have practices that may include 

the use of metallic mercury. The most common organic mercury compound that 

microorganisms and natural processes generate from other forms is methylmercury.

Methylmercury is of particular concern because it can build up in certain edible 

freshwater and saltwater fish and marine mammals to levels that are many times 

greater than levels in the surrounding water.

Because mercury occurs naturally in the environment, everyone is exposed to very low 

levels of mercury in air, water, and food. Some people may be exposed to higher levels 

of mercury in this form if they have a diet high in fish, shellfish, or marine mammals. 

Workers are mostly exposed from breathing air that contains mercury vapors, but 

may also be exposed to other inorganic mercury compounds in the workplace.

Children are at risk of being exposed to metallic mercury that is not safely contained, 

to mercury that may be brought home on work clothes or tools, or to methylmercurycontaminated foods.

The nervous system is very sensitive to mercury. Permanent damage to the brain has 

been shown to occur from exposure to sufficiently high levels of metallic mercury. The 

kidneys are also sensitive to the effects of mercury, because mercury accumulates in 

the kidneys and causes higher exposures to these tissues, and thus more damage.

Be careful when you handle and dispose of all items in the home that contain metallic 

mercury. If larger amounts of metallic mercury are found (for example, a jar of liquid 

mercury), it should be contained in an airtight container, and you should call your local 

health department for instructions on how to safely dispose of it.

There are reliable and accurate ways to measure mercury levels in the body. These tests 

all involve taking blood, urine, or hair samples, and must be performed in a doctor’s 

office or in a health clinic. To help prevent harm from exposure, the EPA, FDA, and 

OSHA have established exposure limits. ◆
6

MERCURY AND 

THE ENVIRONMENT 

Mercury is a naturally occurring metal found throughout 

the environment.

Mercury enters the environment as the result of the normal breakdown of minerals 

in rocks and soil from exposure to wind and water, and from volcanic activity. Human 

activities (e.g., mining, burning of fossil fuels) have resulted in additional 

release of mercury to the environment. Estimates of the total annual 

mercury releases that result from human activities range from one-third 

to two-thirds of the total mercury releases. The levels of mercury in the 

atmosphere (i.e., the air you breathe in the general environment) are 

very, very low and do not pose a health risk; however, the steady release 

of mercury has resulted in current levels that are three to six times higher 

than the estimated levels in the preindustrial era atmosphere.

Approximately 80% of the mercury released from human activities 

is elemental mercury released to the air, primarily from fossil fuel 

combustion, mining, and smelting, and from solid waste incineration.

About 15% of the total is released to the soil from fertilizers, fungicides, 

and municipal solid waste (for example, from waste that contains 

discarded batteries, electrical switches, or thermometers). An additional 

5% is released from industrial wastewater to water in the environment. 

With the exception of mercury ore deposits, the amount of mercury 

that naturally exists in any one place is usually very low. In contrast, the 

amount of mercury that may be found in soil at a particular hazardous 

waste site because of human activity can be high (over 200,000 times 

natural levels). The mercury in air, water, and soil at hazardous waste sites 

may come from both natural sources and human activity.

Most of the mercury found in the environment is in the form of metallic 

mercury and inorganic mercury compounds. Metallic and inorganic 

mercury enters the air from mining deposits of ores that contain 

mercury, from the emissions of coal-fired power plants, from burning 

municipal and medical waste, from the production of cement, and from 

uncontrolled releases in factories that use mercury. Metallic mercury is 

a liquid at room temperature, but some of the metal will evaporate into the air and 
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The levels of 

mercury in the 

atmosphere 

(i.e., the air 

you breathe 

in the general 

environment) 

are very, very 

low and 

do not pose 

a health risk.

can be carried long distances. In air, the mercury vapor 

can be changed into other forms of mercury, and can 

be further transported to water or soil in rain or snow.

Inorganic mercury may also enter water or soil from 

the weathering of rocks that contain mercury, from 

factories or water treatment facilities that release water 

contaminated with mercury, and from incineration of 

municipal garbage that contains mercury (for example, 

in thermometers, electrical switches, or batteries 

that have been thrown away). Inorganic or organic 

compounds of mercury may be released to the water or 

soil if mercury-containing fungicides are used.

Microorganisms (bacteria, phytoplankton in the ocean, 

and fungi) convert inorganic mercury to methylmercury.

Methylmercury released from microorganisms can 

enter the water or soil and remain there for a long time, 

particularly if the methylmercury becomes attached to 

small particles in the soil or water. Mercury usually stays 

on the surface of sediments or soil and does not move 

through the soil to underground water. If mercury enters 

the water in any form, it is likely to settle to the bottom 

where it can remain for a long time.

Mercury can enter and accumulate in the food chain. The 

form of mercury that accumulates in the food chain is 

methylmercury. Inorganic mercury does not accumulate 

up the food chain to any extent. When small fish eat 

the methylmercury in food, it goes into their tissues.

When larger fish eat smaller fish or other organisms that 

contain methylmercury, most of the methylmercury 

originally present in the small fish will then be stored in 

the bodies of the larger fish. As a result, the larger and 

older fish living in contaminated waters build up the 
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highest amounts of methylmercury in their bodies. Saltwater fish (especially sharks 

and swordfish) that live a long time and can grow to a very large size tend to have the 

highest levels of mercury in their bodies. Plants (such as corn, wheat, and peas) have 

very low levels of mercury, even if grown in soils containing mercury at significantly 

higher than background levels. Mushrooms, however, can accumulate high levels if 

grown in contaminated soils. ◆
9

EXPOSURE 

TO MERCURY

Because mercury occurs naturally in the environment, everyone 

is exposed to very low levels of mercury in air, water, and food.

The levels of mercury that have been measured in urban outdoor air are hundreds of 

times lower than levels still considered to be “safe” to breathe. Background levels in 

nonurban settings are even lower. Mercury levels in surface water are generally about 

a thousand times lower than “safe” drinking water standards. 

A potential source of exposure to metallic mercury for the general population is 

mercury released from dental amalgam fillings. An amalgam is a mixture of metals.

The amalgam used in silver-colored dental fillings contains 

approximately 50% metallic mercury, 35% silver, 9% tin, 6% 

copper, and trace amounts of zinc. The mercury from dental 

amalgam may contribute from 0 to more than 75% of your total 

daily mercury exposure, depending on the number of amalgam 

fillings you have, the amount of fish consumed, the levels of 

mercury (mostly as methylmercury) in those fish, and exposure 

from other less common sources such as mercury spills, religious 

practices, or herbal remedies that contain mercury. However, 

it should be kept in mind that exposure to very small amounts 

of mercury, such as that from dental amalgam fillings, does not 

necessarily pose a health risk.

Whether the levels of exposure to mercury vapor from dental 

amalgam are sufficiently high to cause adverse health effects, 

and exactly what those effects are, continues to be researched 

and debated by scientists and health officials. U.S. government summaries on the 

effects of dental amalgam conclude that there is no apparent health hazard to the 

general population, but that further study is needed to determine the possibility 

of more subtle behavioral or immune system effects, and to determine the levels 

of exposure that may lead to adverse effects in sensitive populations. Sensitive 

populations may include pregnant women, children under the age of 6 (especially 

up to the age of 3), people with impaired kidney function, and people with 

hypersensitive immune responses to metals.

You must be careful 

when you handle 

and dispose of 

all items in the home 

that contain 

metallic mercury.
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Some religions have practices that may include the use 

of metallic mercury. Examples of these religions include 

Santeria (a Cuban-based religion whose followers 

worship both African deities and Catholic saints), Voodoo 

(a Haitian-based set of beliefs and rituals), Palo Mayombe 

(a secret form of ancestor worship practiced mainly in 

the Caribbean), and Espiritismo (a spiritual belief system 

native to Puerto Rico). Not all people who observe 

these religions use mercury, but when mercury is used 

in religious, ethnic, or ritualistic practices, exposure to 

mercury may occur both at the time of the practice 

and afterwards from contaminated indoor air. Metallic 

mercury is sold under the name “azogue” (pronounced 

ah-SEW-gay) in stores called “botanicas.” Botanicas are 

common in Hispanic and Haitian communities, where 

azogue may be sold as an herbal remedy or for spiritual 

practices. The metallic mercury is often sold in capsules 

or in glass containers. It may be placed in a sealed pouch 

to be worn on a necklace or in a pocket, or it may be 

sprinkled in the home or car. Some people may mix 

azogue in bath water or perfume, or place azogue in 

devotional candles. Because metallic mercury evaporates 

into the air, these practices may put anyone breathing 

the air in the room at risk of exposure to mercury. The 

longer people breathe the contaminated air, the greater 

their risk will be. The use of metallic mercury in a home 

or an apartment not only threatens the health of the 

people who live there now, but also threatens the health 

of future residents who may unknowingly be exposed 

to further release of mercury vapors from contaminated 

floors or walls.

Metallic mercury is used in a variety of household 

products and industrial items, including thermostats, 

fluorescent light bulbs, barometers, glass thermometers, 

and some blood pressure devices. The mercury in these 

devices is contained in glass or metal, and generally does 

not pose a risk unless the item is damaged or broken, and 

mercury vapors are released. Spills of metallic mercury 

from broken thermometers or damaged electrical 
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switches in the home may result in exposure to mercury 

vapors in indoor air. You must be careful when you handle 

and dispose of all items in the home that contain metallic 

mercury.

Very small amounts of metallic mercury (for example, 

a few drops) can raise air concentrations of mercury to 

levels that may be harmful to health. The longer people 

breathe the contaminated air, the greater the risk to their 

health. Metallic mercury and its vapors are extremely 

difficult to remove from clothes, furniture, carpet, 

floors, walls, and other such items. If these items are not 

properly cleaned, the mercury can remain for months or 

years, and continue to be a source of exposure.

It is possible for you to be exposed to metallic mercury 

vapors from breathing contaminated air around 

hazardous waste sites, waste incinerators, or power 

plants that burn mercury-containing fuels (such as coal 

or other fossil fuels), but most outdoor air is not likely 

to contain levels that would be harmful. Exposure to 

mercury compounds at hazardous waste sites is much 

more likely to occur from handling contaminated 

soil (i.e., children playing in or eating contaminated 

surface soil), drinking well-water, or eating fish from 

contaminated waters near those sites. Not all hazardous 

sites contain mercury, and not all waste sites that do 

contain mercury have releases of mercury to the air, 

water, or surface soils.

You can be exposed to mercury vapors from the use 

of fungicides that contain mercury. Excess use of these 

products may result in higher-than-average exposures.

You may also be exposed to mercury from swallowing 

or applying to your skin outdated medicinal products 

(laxatives, worming medications, and teething powders) 

that contain mercurous chloride. Exposure may also 

occur from the improper or excessive use of other 

chemicals containing mercury, such as skin-lightening 

creams and some topical antiseptic or disinfectant 

agents (mercurochrome and thimerosal).

Some people 

may be exposed 

to higher levels 

of mercury in 

the form of 

methylmercury 

if they have 

a diet high in 

fish, shellfish, 

or marine 

mammals.
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Workers are mostly exposed from breathing air that contains mercury vapors, but 

may also be exposed to other inorganic mercury compounds in the workplace.

Occupations that have a greater potential for mercury exposure include 

manufacturers of electrical equipment or automotive parts that contain mercury, 

chemical processing plants that use mercury, metal processing, construction where 

building parts contain mercury (e.g., electrical switches, thermometers), and the 

medical professions (medical, dental, or other health services) where equipment 

may contain mercury (e.g., some devices that measure blood pressure contain liquid 

mercury). Dentists and their assistants may be exposed to metallic mercury from 

breathing in mercury vapor released from amalgam fillings and to a much lesser 

extent from skin contact with amalgam restorations. Family members of workers 

who have been exposed to mercury may also be exposed to mercury if the worker’s 

clothes are contaminated with mercury particles or liquid.

Some people may be exposed to higher levels of mercury in the form of 

methylmercury if they have a diet high in fish, shellfish, or marine mammals (whales, 

seals, dolphins, and walruses) that come from mercury-contaminated waters.

Methylmercury accumulates up the food chain, so that fish at the top of the food 

chain will have the most mercury in their flesh. Of these fish, the largest (i.e., the 

oldest) fish will have the highest levels. Commercial fish sold through interstate 

commerce that are found to have levels of methylmercury above an “action level” of 1 

ppm (established by the FDA) cannot be sold to the public. This level itself is below a 

level associated with adverse effects. Public health advisories are issued by state and 

federal authorities for local waters that are thought to be contaminated with mercury.

Foods other than fish that may contain higher than average levels of mercury 

include wild game, such as wild birds and mammals (bear) that eat large amounts 

of contaminated fish. People in the most northern climates may be exposed to high 

levels of mercury from eating meat or fat from marine mammals including whales, 

dolphins, walruses, and seals. Plants contain very little methylmercury or other forms 

of mercury. Mushrooms grown in mercury-contaminated soil may contain levels of 

mercury that could pose some risk to health, if large amounts were eaten. ◆
13

MERCURY 

AND THE BODY 

Oral exposure to mercury results in very small amounts 

getting into your body. 

When you swallow small amounts of metallic mercury, for example, from a broken 

oral thermometer, virtually none (less than 0.01%) of the mercury will enter your 

body through the stomach or intestines, unless they are diseased. Even when a 

larger amount of metal mercury (a half of a tablespoon, about 204 grams) was 

swallowed by one person, very little entered the body. When you breathe in mercury 

vapors, however, most (about 80%) of the mercury enters your bloodstream directly 

from your lungs, and then rapidly goes to other parts of your body, including 

the brain and kidneys. Once in your body, metallic mercury can stay for weeks 

or months. When metallic mercury enters the brain, it is readily converted to an 

inorganic form and is “trapped” in the brain for a long time. Metallic mercury in the 

blood of a pregnant woman can enter her developing child. Most of the metallic

mercury will accumulate in your kidneys, but some metallic mercury can also 

accumulate in the brain. Most of the metallic mercury absorbed into the body 

eventually leaves in the urine and feces, while smaller amounts leave the body in the 

exhaled breath.

Inorganic mercury compounds like mercurous chloride and mercuric chloride are 

white powders and do not generally vaporize at room temperatures like elemental 

mercury will. If they are inhaled, they are not expected to enter your body as easily as 

inhaled metallic mercury vapor. When inorganic mercury compounds are swallowed, 

generally less than 10% is absorbed through the intestinal tract; however, up to 40% 

may enter the body through the stomach and intestines in some instances. Some

inorganic mercury can enter your body through the skin, but only a small amount 

will pass through your skin compared to the amount that gets into your body from 

swallowing inorganic mercury. Once inorganic mercury enters the body and gets 

into the bloodstream, it moves to many different tissues. Inorganic mercury leaves 

your body in the urine or feces over a period of several weeks or months. A small 

amount of the inorganic mercury can be changed in your body to metallic mercury 

and leave in the breath as a mercury vapor. Inorganic mercury accumulates mostly 

in the kidneys and does not enter the brain as easily as metallic mercury. Inorganic 
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mercury compounds also do not move as easily from 

the blood of a pregnant woman to her developing child.

In a nursing woman, some of the inorganic mercury in 

her body will pass into her breast milk.

Methylmercury is the form of mercury most easily 

absorbed through the gastrointestinal tract (about 95% 

absorbed). After you eat fish or other foods that are 

contaminated with methylmercury, the methylmercury 

enters your bloodstream easily and goes rapidly 

to other parts of your body. Only small amounts 

of methylmercury enter the bloodstream directly 

through the skin, but other forms of organic mercury 

(in particular dimethylmercury) can rapidly enter the 

body through the skin. Organic mercury compounds 

may evaporate slowly at room temperature and may 

enter your body easily if you breathe in the vapors. Once 

organic mercury is in the bloodstream, it moves easily to 

most tissues and readily enters the brain. Methylmercury 

that is in the blood of a pregnant woman will easily 

move into the blood of the developing child and then 

into the child’s brain and other tissues. Like metallic 

mercury, methylmercury can be changed by your body 

to inorganic mercury. When this happens in the brain, 

the mercury can remain there for a long time. When 

methylmercury does leave your body after you have 

been exposed, it leaves slowly over a period of several 

months, mostly as inorganic mercury in the feces. As 

with inorganic mercury, some of the methylmercury in a 

nursing woman’s body will pass into her breast milk. ◆

Metallic 

mercury in 

the blood of 

a pregnant 

woman can 

enter her 

developing 

child.
15

HEALTH EFFECTS

OF EXPOSURE 

The nervous system is very sensitive to mercury.

In poisoning incidents that occurred in other countries, some people who ate fish 

contaminated with large amounts of methylmercury or seed grains treated with 

methylmercury or other organic mercury compounds developed permanent damage 

to the brain and kidneys. Permanent damage to the brain has also been shown to 

occur from exposure to sufficiently high levels of metallic mercury. Whether exposure 

to inorganic mercury results in brain or nerve damage is not as certain, since it does 

not easily pass from the blood into the brain.

Metallic mercury vapors or organic mercury may affect many different areas of the 

brain and their associated functions, resulting in a variety of symptoms. These include 

personality changes (irritability, shyness, nervousness), tremors, changes in vision 

(constriction (or narrowing) of the visual field), deafness, muscle incoordination, loss of 

sensation, and difficulties with memory.

Different forms of mercury have different effects on the nervous system, because they 

do not all move through the body in the same way. When metallic mercury vapors are 

inhaled, they readily enter the bloodstream and are carried throughout the body and 

can move into the brain. Breathing in or swallowing large amounts of methylmercury 

also results in some of the mercury moving into the brain and affecting the nervous 

system. Inorganic mercury salts, such as mercuric chloride, do not enter the brain as 

readily as methylmercury or metallic mercury vapor.

The kidneys are also sensitive to the effects of mercury, because mercury accumulates 

in the kidneys and causes higher exposures to these tissues, and thus more damage.

All forms of mercury can cause kidney damage if large enough amounts enter the 

body. If the damage caused by the mercury is not too great, the kidneys are likely to 

recover once the body clears itself of the contamination.

Short-term exposure (hours) to high levels of metallic mercury vapor in the air can 

damage the lining of the mouth and irritate the lungs and airways, causing tightness 

of the breath, a burning sensation in the lungs, and coughing. Other effects from 

exposure to mercury vapor include nausea, vomiting, diarrhea, increases in blood 

pressure or heart rate, skin rashes, and eye irritation. Damage to the lining of the 
16

mouth and lungs can also occur from exposure to lower 

levels of mercury vapor over longer periods (for example, in 

some occupations where workers were exposed to mercury 

for many years). Levels of metallic mercury in workplace 

air are generally much greater than the levels normally 

encountered by the general population. Current levels of 

mercury in workplace air are low, due to increased awareness 

of mercury’s toxic effects. Because of the reduction in the 

allowable amount of mercury in workplace air, fewer workers 

are expected to have symptoms of mercury toxicity. Most 

studies of humans who breathed metallic mercury for a long 

time indicate that mercury from this type of exposure does 

not affect the ability to have children. Studies in workers 

exposed to metallic mercury vapors have also not shown any 

mercury-related increase in cancer. Skin contact with metallic 

mercury has been shown to cause an allergic reaction (skin 

rashes) in some people.

In addition to effects on the kidneys, inorganic mercury can 

damage the stomach and intestines, producing symptoms 

of nausea, diarrhea, or severe ulcers if swallowed in large 

amounts. Effects on the heart have also been observed in 

children after they accidentally swallowed mercuric chloride.

Symptoms included rapid heart rate and increased blood 

pressure. There is little information on the effects in humans 

from long-term, low-level exposure to inorganic mercury.

Studies using animals indicate that long-term oral exposure 

to inorganic mercury salts causes kidney damage, effects on 

blood pressure and heart rate, and effects on the stomach.

Some rat and mice strains that are susceptible to 

autoimmune responses develop kidney damage as a result 

of an immune response when exposed to relatively low 

levels of mercury vapor or mercury chloride. ◆

The kidneys 

are also 

sensitive to 

the effects 

of mercury, 

because 

mercury 

accumulates 

in the kidneys 

and causes 

higher 

exposures to 

these tissues.
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Health effects caused by 

long-term exposure to mercury vapors

Anxiety

Excessive shyness

Anorexia

Sleeping problems

Loss of appetite

Irritability

Fatigue

Forgetfulness

Tremors

Changes in vision

Changes 

in hearing

Health effects caused by short-term exposure 

to high levels of mercury vapors

Cough, sore throat

Shortness of breath

Chest pain

Nausea, vomiting, 

diarrhea

Eye irritation

Increase in blood 

pressure 

or heart rate

A metallic taste 

in the mouth

Headache

Vision problems
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MERCURY 

AND CHILDREN 

Children are at risk of being exposed to mercury in a number 

of ways. 

Some of these routes may include exposure to metallic mercury that is not safely 

contained, to mercury that may be brought home on work clothes or 

tools, or to methylmercury-contaminated foods. Methylmercury eaten 

or swallowed by a pregnant woman or metallic mercury that enters 

her body from breathing contaminated air can also pass into the 

developing child. Inorganic mercury and methylmercury can also pass 

from a mother’s body into breast milk and into a nursing infant. The 

amount of mercury in the milk will vary, depending on the degree of 

exposure and the amount of mercury that enter the nursing woman’s 

body. There are significant benefits to breast feeding, so any concern 

that a nursing woman may have about mercury levels in her breast 

milk should be discussed with her doctor. Methylmercury can also 

accumulate in an unborn baby’s blood to a concentration higher than 

the concentration in the mother.

For similar exposure routes and forms of mercury, the harmful health 

effects seen in children are similar to the effects seen in adults. High exposure to 

mercury vapor causes lung, stomach, and intestinal damage and death due to 

respiratory failure in severe cases. These effects are similar to those seen in adult 

groups exposed to inhaled metallic mercury vapors at work.

Children who had been exposed to excessive amounts of mercurous chloride tablets 

for worms or mercurous chloride-containing powders for teething discomfort had 

increased heart rates and elevated blood pressure. Abnormal heart rhythms were 

also seen in children who had eaten grains contaminated with very high levels of 

methylmercury.

Other symptoms of poisonings in children who were treated with mercurous chloride 

for constipation, worms, or teething discomfort included swollen red gums, excessive 

salivation, weight loss, diarrhea and/or abdominal pain, and muscle twitching or 

cramping in the legs and/or arms. Kidney damage is very common after exposure to 

toxic levels of inorganic mercury. Metallic mercury or methylmercury that enters the 
19

U.S. Map of National Response Center (NRC) 

Reported Events Representing Children 

Potentially Exposed to Elemental Hg: 2002–2007

Reported Events

0

0–2

2–4

4–6

6–8

8–10

A total of 113 events over the five year period.

Data source: NRC Database, 2002–2008.

NRC events represent potential childhood exposures. States with more calls may 

reflect increased awareness of Hg hazards and subsequently increased reporting.

AAPCC Reported Events Potentially Exposing Children to 

Elemental Mercury during 2002 through 2006 by State

Reported Events

1–50

50–100

100–250

250–500

500–921

A total of 6,396 events over the five year period. Excludes mercury thermometer events.

Data source: National Poison Data System (NPDS). Compiled by the American 

Association of Poison Control Centers (AAPCC) 2002–2006.

AAPCC events represent individual calls to AAPCC. Multiple calls may refer to one or 

more Hg exposure events. States with more calls may reflect increased awareness of Hg 

hazards and subsequently increased reporting.

body can also be converted to inorganic 

mercury and result in kidney damage. 

Children who breathe metallic/elemental 

mercury vapors, eat foods or other 

substances containing phenylmercury or 

inorganic mercury salts, or use mercurycontaining skin ointments for an extended 

period may develop a disorder known as 

acrodynia, or pink disease. Acrodynia can 

result in severe leg cramps; irritability; and 

abnormal redness of the skin, followed by 

peeling of the hands, nose, and soles of 

the feet. Itching, swelling, fever, fast heart 

rate, elevated blood pressure, excessive 

salivation or sweating, rashes, fretfulness, 

sleeplessness, and/or weakness may also 

be present. It was once believed that this 

syndrome occurred only in children, but 

recent reported cases in teenagers and 

adults have shown that they can also 

develop acrodynia.

In critical periods of development before 

they are born, and in the early months after 

birth, children and fetuses are particularly 

sensitive to the harmful effects of metallic 

mercury and methylmercury on the nervous 

system. Harmful developmental effects may 

occur when a pregnant woman is exposed 

to metallic mercury and some of the 

mercury is transferred into her developing 

child. Thus, women who are normally 

exposed to mercury vapors in the workplace 
20

(such as those working in thermometer/barometer or fluorescent light manufacturing 

or the chloralkali industry) should take measures to avoid mercury vapor exposures 

during pregnancy. Exposures to mercury vapors are relatively rare outside of the 

workplace, unless metallic mercury is present in the home.

As with mercury vapors, exposure to methylmercury is more dangerous for young 

children than for adults, because more methylmercury easily passes into the 

developing brain of young children and may interfere with the development process.

Methylmercury is the form of mercury most commonly associated with a risk for 

developmental effects. Exposure can come from foods contaminated with mercury on 

the surface (for example, from seed grain treated with methylmercury to kill fungus) 

or from foods that contain toxic levels of methylmercury (as in some fish, wild game, 

and marine mammals). Mothers who are exposed to methylmercury and breast-feed 

their infant may also expose the child through the milk. The effects on the infant 

may be subtle or more pronounced, depending on the amount to which the fetus 

or young child was exposed. In cases in which the exposure was very small, some 

effects might not be apparent, such as small decreases in IQ or effects on the brain 

that may only be determined by the use of very sensitive neuropsychological testing.

In instances in which the exposure is great, the effects may be more serious. In some 

such cases of mercury exposure involving serious exposure to the developing fetus, 

the effects are delayed. In such cases, the infant may be born apparently normal, but 

later show effects that may range from the infant being slower to reach developmental 

milestones, such as the age of first walking and talking, to more severe effects 

including brain damage with mental retardation, incoordination, and inability to move.

Other severe effects observed in children whose mothers were exposed to very toxic 
21

In critical 

periods of 

development 

before they 

are born, and 

in the early 

months after 

birth, fetuses 

and children 

are particularly 

sensitive to the 

harmful effects 

of metallic 

mercury and 

methylmercury 

on the nervous 

system.

levels of mercury during pregnancy include eventual 

blindness, involuntary muscle contractions and seizures, 

muscle weakness, and inability to speak. It is important 

to remember, however, that the severity of these effects 

depends upon the level of mercury exposure and the 

time of exposure. The very severe effects just mentioned 

were reported in large-scale poisoning instances in which 

pregnant and nursing women were exposed to extremely 

high levels of methylmercury in contaminated grain used 

to make bread (in Iraq) or seafood (in Japan) sold to the 

general population.

Researchers are currently studying the potential for 

less serious developmental effects, including effects on 

a child’s behavior and ability to learn, think, and solve 

problems that may result from eating lower levels of 

methylmercury in foods. A main source of exposure to 

methylmercury for the pregnant woman and the young 

child is from eating fish. Most fish purchased in the 

market in the United States do not have mercury levels 

that pose a risk to anyone, including pregnant women.

Since mercury accumulates in the muscles of fish, larger 

fish that feed on smaller fish and live for long periods 

usually have larger concentrations of methylmercury than 

fish that feed on plants. For example, shark and swordfish 

normally contain the highest levels of mercury out of all 

ocean fish. Scientists have an ongoing debate about the 

value of fish in the diet versus any risk from increased 

exposure of pregnant women to methylmercury that may 

be in the fish. The safety of most fish sold commercially 

in the United States is regulated by the FDA. These fish 

pose no health risk to those who purchase and eat them.

Only fish or wildlife containing relatively high levels of 

methylmercury are of concern. ◆
22

REDUCING RISK 

OF EXPOSURE 

If your doctor finds that you have been exposed to significant 

amounts of mercury, ask whether your children might also 

be exposed. Your doctor might need to ask your state health 

department to investigate.

Children may be exposed to metallic mercury if they play with it. Metallic mercury 

is a heavy, shiny, silver liquid. When metallic mercury is spilled, it forms little balls 

or beads. Children are sometimes exposed to metallic mercury when they find it in 

abandoned warehouses or closed factories, and then play with it or pass it around 

to friends. Children have also taken metallic mercury from school chemistry and 

physics labs. Broken thermometers and some electrical switches are other sources 

of metallic mercury. Sometimes children find containers of metallic mercury that 

were improperly disposed of, or adults may bring home metallic 

mercury from work, not knowing that it is dangerous.

To protect your children from metallic mercury, teach them not 

to play with shiny, silver liquids. Schoolteachers (particularly 

science teachers) and school staff need to know about students’ 

fascination with metallic mercury. Teachers and school staff 

should teach children about the dangers of getting sick from 

playing with mercury, and they should keep metallic mercury in 

a safe and secured area (such as a closed container in a locked 

storage room) so that children do not have access to it without 

the supervision of a teacher. Metallic mercury evaporates slowly, 

and if it is not stored in a closed container, children may breathe 

toxic mercury vapors.

In the past, mercurous chloride was widely used in medicinal products such as 

laxatives, worming medications, and teething powders. These older medicines should 

be properly disposed of and replaced with safer and more effective medicines.

Other chemicals containing mercury, such as mercurochrome and thimerosal (sold 

as Merthiolate and other brands), are still used as antiseptics or as preservatives in 

eye drops, eye ointments, nasal sprays, and vaccines. Some skin-lightening creams 

contain ammoniated mercuric chloride and mercuric iodide. These and all other 
23

You should 

check to see 

if any medicines 

or herbal 

remedies 

that you or your 

child 

use contain 

mercury.

mercury-containing medicines should be kept safely out of 

the reach of children to prevent an accidental poisoning.

Nonmedicinal products, including some fungicides that 

contain mercury compounds and paints that contain mercuric 

sulfide or mercuric oxide, should also be safely stored out of 

the reach of children.

You should check to see if any medicines or herbal remedies 

that you or your child use contain mercury. Some traditional 

Chinese and Indian remedies for stomach disorders (for 

example, herbal balls) contain mercury, and if you give these 

remedies to your children, you may harm them. If you are 

pregnant or nursing a baby and you use mercury-containing 

ethnic or herbal remedies, you could pass some of the mercury 

to your unborn child or nursing infant.

If you use metallic mercury or azogue in religious practices, 

you may expose your children or unborn child to mercury 

or contaminate your home. Such practices in which mercury 

containing substances have traditionally been used include 

Santeria (a Cuban-based religion whose followers worship 

both African deities and Catholic saints), Voodoo (a Haitianbased set of beliefs and rituals), Palo Mayombe (a secret form 

of ancestor worship practiced mainly in the Caribbean), or 

Espiritismo (a spiritual belief system native to Puerto Rico).

Metallic mercury is used in a variety of household products 

and industrial items, including thermostats, fluorescent light 

bulbs, barometers, glass thermometers, and some blood 

pressure measuring devices. You must be careful when you 

handle and dispose of all items in the home that contain 

metallic mercury.

If small amounts of mercury are spilled, be very careful 

cleaning it up. Do not try to vacuum spilled metallic mercury.
24

Using a vacuum cleaner to clean up the mercury causes the mercury to evaporate 

into the air, creating greater health risks. Trying to vacuum spilled metallic mercury 

also contaminates the vacuum cleaner. Also, take care not to step on the mercury 

and track it into other areas of the home. Metallic mercury vapors are very toxic and 

have no odor. Do not remain unnecessarily in that room, and try not to let metallic 

mercury contact your eyes, skin, or clothing. If you think you have been exposed 

directly to metallic mercury, wash yourself thoroughly and discard 

contaminated clothing by placing them in a sealed plastic bag.

Perhaps the most important thing to remember if you break a 

household thermometer is do not panic. The amount of mercury 

contained in an oral thermometer is small and does not present 

an immediate threat to human health. However, if it is not 

properly cleaned up and disposed of, it may present a health risk 

over time, particularly to infants, toddlers, and pregnant women.

If a thermometer breaks on a counter top or uncarpeted floor, 

remove children from the area. Mercury is not absorbent, so 

do not try to wipe or blot it up with a cloth or paper towel; that 

will only spread the mercury and break it up into smaller beads, 

making it more difficult to find and remove. Instead, clean up 

the beads of metallic mercury by using one sheet of paper to 

carefully roll them onto a second sheet of paper, or by sucking 

very small beads of mercury into an eye dropper. After picking 

up the metallic mercury in this manner, put it into a plastic bag or airtight container.

The paper and eye dropper should also be bagged in a zip-lock plastic container.

All plastic bags used in the cleanup should then be taken outside of the house or 

apartment and disposed of properly, according to instructions provided by your local 

health department or environmental officials. Try to ventilate the room with outside 

air, and close the room off from the rest of the home. Use fans (that direct the air to 

the outside and away from the inside of the house) for a minimum of one hour to 

speed the ventilation.

If a thermometer breaks and the liquid/metallic mercury spills onto a carpeted floor, 

try to collect the mercury beads in the manner described in the above paragraph.

Do not try to 

vacuum spilled 

metallic mercury. 

Using a vacuum 

cleaner to clean up 

the mercury causes the 

mercury to evaporate 

into the air, creating 

greater health risks.
25

Depending on the cut or pile of the carpeting, however, it may not be possible to 

collect all of the spilled mercury. Regardless, do not vacuum. Instead, call your local 

(county, city, or state) health department and tell them of your situation. (You may 

also call the Agency for Toxic Substances and Disease Registry [ATSDR] toll-free at 

1-888-42-ATSDR [1-888-422-8737] to obtain additional guidance, if local assistance 

cannot be obtained.) 

If larger amounts of metallic mercury are found (for example, a jar of liquid mercury), 

it should be contained in an airtight container, and you should call your local health 

department for instructions on how to safely dispose of it. If the mercury is in an open 

container or the container does not have a lid, place a piece of plastic wrap around 

the top of the container to prevent vapors from escaping; then wash your hands 

thoroughly. If a larger amount is spilled, leave the area and contact your local health 

department and fire department. Do not simply throw metallic mercury away, but 

instead seek professional help.

ATSDR and EPA strongly recommend against the use of metallic (liquid) mercury that 

is not properly enclosed in glass, as it is in thermometers. This form of mercury should 

not be used or stored in homes, automobiles, day-care centers, schools, offices, 

or other public buildings. If you notice a child with metallic mercury on his or her 

clothing, skin, or hair, call the fire department and let them know that the child needs 

to be decontaminated.
26

Metallic or inorganic mercury can be carried into the home from a workers’ 

contaminated clothing and shoes. Increased exposure to mercury has been reported 

in children of workers who are exposed to mercury at work, and increased levels 

of mercury were measured in places where work clothes were stored and in some 

washing machines. The children most likely to be exposed to risky levels of mercury 

are those whose parents work in facilities that use mercury (for example, a scientific 

glassware manufacturing plant or a chlor-alkali chemical plant), but where no 

protective uniforms or footgear are used. In some reported cases 

in which children were exposed in this way, protective clothing 

was used in the workplace by the parent, but work gloves, 

clothes, and boots, which were contaminated with mercury, were 

taken home, thus exposing family members.

The Occupational Safety and Health Administration (OSHA) 

requires employers to provide Material Safety Data Sheets 

(MSDSs) for many of the chemicals used at the workplace.

Information on these sheets should include chemical names 

and hazardous ingredients, important properties (such as fire 

and explosion data), potential health effects, how you get the 

chemical(s) in your body, how to properly handle the materials, 

and what to do in an emergency. Your occupational health and 

safety officer at work can and should tell you whether chemicals 

you work with are dangerous and likely to be carried home 

on your clothes, body, or tools, and whether you should be 

showering and changing clothes before you leave work, storing 

your street clothes in a separate area of the workplace, or laundering your work 

clothes at home separately from other clothes. Your employer is legally responsible 

for providing a safe workplace and should freely answer your questions about 

hazardous chemicals. Your OSHA-approved state occupational safety and health 

program or OSHA can also answer any further questions you might have, and help 

your employer identify and correct problems with hazardous substances. If you would 

like to make a formal complaint about health hazards in your workplace, your OSHAapproved state occupational safety and health program or OSHA office will listen to 

your complaint and inspect your workplace when necessary.

Mercury is 

not absorbent, 

so do not try to wipe 

or blot it up with a 

cloth or paper towel.
27

If you are pregnant, the decision of whether to have dental amalgam or a nonmercury 

material used for fillings, or whether existing amalgam fillings should be repaired or 

replaced during pregnancy, should be made in consultation with your dentist. The 

practice of having all your dental amalgam fillings replaced with non-mercury filling 

materials just to remove the possibility of mercury exposure is not recommended by 

ATSDR. In fact, the removal of the mercury amalgam fillings would actually expose 

the patient to a greater amount of mercury for a while.

FDA currently advises that pregnant women and women of childbearing age who 

may become pregnant limit their consumption of shark and swordfish to no more 

that one meal per month. This advice is given because methylmercury levels are 

relatively high in these fish species. Women of childbearing age are included in this 

advice because dietary practices immediately before the pregnancy could have a 

direct bearing on fetal exposure during pregnancy, particularly during the earlier 

months of pregnancy.

FDA further advises that persons other than pregnant women and women of 

childbearing age in the general population limit their regular consumption of shark 

and swordfish (which typically contains methylmercury around 1 ppm) to about 

7 ounces per week (about one serving) to stay below the acceptable daily intake 

for methylmercury. For fish species with methylmercury levels averaging 0.5 ppm, 

regular consumption should be limited to 14 ounces per week. Recreational and 

subsistence fishers who eat larger amounts of fish than the general population and 

routinely fish the same waterbodies may have a higher exposure to methylmercury 

if these waters are contaminated. People who consume greater than 100 grams of 

fish (approximately 3.5 ounces) every day are considered high-end consumers. This 

is over 10 times more than the amount of fish consumed by members of the general 

population (6.5 g/day). No consumption advice is necessary for the top ten seafood 

species that make up about 80% of the seafood sold in the United States: canned 

tuna, shrimp, pollock, salmon, cod, catfish, clams, flatfish, crabs, and scallops. The 

methylmercury in these species is generally less than 0.2 ppm, and few people eat 

more than the suggested weekly limit of fish (i.e., 2.2 pounds). ◆
28

EXPOSURE 

TESTING 

There are reliable and accurate ways to measure mercury 

levels in the body.

These tests all involve taking blood, urine, or hair samples, and must be performed 

in a doctor’s office or in a health clinic. Nursing women may have their breast milk 

tested for mercury levels, if any of the other samples tested are 

found to contain significant amounts of mercury. Most of these 

tests, however, do not determine the form of mercury to which 

you were exposed. Mercury levels found in blood, urine, breast 

milk, or hair may be used to determine if adverse health effects 

are likely to occur. Mercury in urine is used to test for exposure 

to metallic mercury vapor and to inorganic forms of mercury.

Measurement of mercury in whole blood or scalp hair is used 

to monitor exposure to methylmercury. Urine is not useful for 

determining whether exposure has occurred to methylmercury.

Levels found in blood, urine, and hair may be used together to 

predict possible health effects that may be caused by the different 

forms of mercury.

Blood and urine levels are used as markers to determine whether 

someone has been exposed to mercury. They are used to 

determine whether exposure to mercury has occurred and to give 

a rough idea of the extent of exposure, but they do not tell exactly 

how much exposure has occurred. Except for methylmercury 

exposures, blood is considered useful if samples are taken within 

a few days of exposure. This is because most forms of mercury in 

the blood decrease by one-half every three days if exposure has 

been stopped. Thus, mercury levels in the blood provide more 

useful information after recent exposures than after long-term exposures. Several 

months after an exposure, mercury levels in the blood and urine are much lower. Hair, 

which is considered useful only for exposures to methylmercury, can be used to show 

exposures that occurred many months ago, or even more than a year ago if the hair is 

long enough and careful testing. ◆
29

GOVERNMENTAL 

RECOMMENDATIONS 

For the most current information, check with the federal 

agency or organization that provides it for the substance in 

which you are interested. 

Some regulations and recommendations for mercury include the following:

EPA and FDA have set a limit of 2 parts inorganic mercury per billion (ppb) parts of 

water in drinking water. EPA is in the process of revising the Water Quality Criteria for 

mercury.

EPA currently recommends that the level of inorganic mercury in rivers, lakes, and 

streams be no more than 144 parts mercury per trillion (ppt) parts of water to 

protect human health (1 ppt is a thousand times less than 1 part per billion, or ppb).

EPA has determined that a daily exposure (for an adult of average weight) to 

inorganic mercury in drinking water at a level up to 2 ppb is not likely to cause any 

significant adverse health effects.

FDA has set a maximum permissible level of 1 part of methylmercury in a million 

parts (ppm) of seafood products sold through interstate commerce (1 ppm is a 

thousand times more than 1 ppb). FDA may seize shipments of fish and shellfish 

containing more than 1 ppm of methylmercury, and may seize treated seed grain 

containing more than 1 ppm of mercury.

OSHA has set a limit of 0.1 milligrams of mercury per cubic meter of air (mg/m3) for 

aryl mercury and 0.01 mg/m3 for alkyl mercury to protect workers during an 8-hour 

shift and a 40-hour work week. NIOSH recommends that the amount of metallic 

mercury vapor in workplace air be limited to an average level of 0.05 mg/m3 during a 

10-hour work shift.

Removal of dental amalgams in people who have no indication of adverse effects is 

not recommended and can put the person at greater risk, if performed improperly.

Chelation therapy (used to remove metals from the body tissues) itself presents 

some health risks, and should be considered only when a licensed occupational or 

environmental health physician determines it necessary to reduce immediate and 

significant health risks due to high levels of mercury in the body. ◆
30

ADDITIONAL 

INFORMATION 

If you have more questions or concerns, please contact 

your community or state health or environmental quality 

department, or contact ATSDR at the address and phone 

number below. 

ATSDR also can tell you the location of occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, and treating illnesses that result 

from exposure to hazardous substances. 

Agency for Toxic Substances and Disease Registry

Division of Toxicology and Human Health Sciences

1600 Clifton Road NE, Mailstop F-57

Atlanta, GA 30329-4027

Toll-free information and technical assistance: 1-800-CDCINFO (1-800-232-4636)

For additional information, please check out ATSDR’s Don’t Mess with Mercury website 

http://www.atsdr.cdc.gov/dontmesswithmercury
31
something like: A publication from the Centers for 

Disease Control and Prevention

ATSDR TOXZINE A publication of CDC/ATSDR

CS246650-A