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APPENDIX A: Population and Housing Data; Census Tract Map

Figure 2. Indian Head Naval Surface Warfare Center



Base*Town of
Indian Head**


Total area,
square miles

Persons per
square mile

% Male

% Female38.651.849.9

% White

% Black

% American Indian,
Eskimo, or Aleut
% Asian or
Pacific Islander
% Other races2.30.20.2

% Hispanic origin




% Under age 10

% Age 65 and older0.312.49.7

Source: Census of Population and Housing, 1990: Summary Tape File 1A (Maryland) [machine-readabledata files]. Prepared by the Bureau of the Census. Washington, DC: The Bureau [producer anddistributor], 1991.

* Tract 850201
** Tract 850202
*** Tract 8503, Block Groups 1 and 2; and Tract 8504, Block Group 1.



Base*Town of
Indian Head**


Persons per

% Households

% Households

% Households
mobile homes

% Persons in
group quarters

Median value,
households, $

Median rent paid,
households, $

Source: Census of Population and Housing, 1990: Summary Tape File 1A (Maryland)[machine-readable data files]. Prepared by the Bureau of the Census. Washington, DC: TheBureau [producer and distributor], 1991.

* Tract 850201
** Tract 850202
*** Tract 8503, Block Groups 1 and 2; and Tract 8504, Block Group 1

Note: A household is an occupied housing unit, but does not include group quarters such asmilitary barracks, prisons, and college dormitories.




Town of
Indian Head**


Total households
Percentage householdersmoving into current housingunit, by time period






Before 1960



















Source: 1990 Census of Population and Housing, Summary Tape File 3 (Maryland). U.S.Bureau of the Census, Washington, DC.

* Tract 850201
** Tract 850202
*** Tract 8503, Block Groups 1 and 2; and Tract 8504, Block Group 1


Base*Town of
Indian Head**
Persons age 25 and older

    % With at least a high school diploma




Total households

    Median income, $

    % Below poverty level







Employed persons age 16 and older(civilian)

    % In blue-collar jobs

    % In white-collar jobs







Total housing units

    % With water from public system or private company

    % With water from individual well or other source










Source: 1990 Census of Population and Housing, Summary Tape File 3 (Maryland). Preparedby Bureau of the Census, Washington, DC.

* Tract 850201
** Tract 850202
*** Tract 8503, Block Groups 1 and 2; and Tract 8504, Block Group 1

APPENDIX B: Summary of Site Evaluations


Summary of Site Evaluations, NSWC-IHDIV, Indian Head, Maryland
Site Location and Number EvaluationComments
NSWC: Sites 51, 52

There is no evidence of contaminant release(s) at these sites.

These sites have been removed from the IRP list anddesignated as "No Further Action" required.
NSWC: Sites 5, 8

These are sites with surface, sub-surface, shallow groundwater and surface water contamination. However, based on the information and data currently available for these sites, ATSDR concludes thatthere are no public health issues associated with these areas of contamination (other than thosesituations identified in the text of the PHA).

  • No past exposure situations were identified for these sites
  • No current exposure situations were identified. Areas of soil contamination, including the network ofdrainage ditches that discharge into the creeks and Potomac River, are well vegetated and in some casehave been paved. Although shallow groundwater at the base is contaminated, sampling data indicatethat the contaminants have not migrated off-site into the community. Both the base and Charles Countyresidential and industrial water supplies are obtained from the deeper Patapsco and Patuxentgroundwater aquifers. Employees do not generally work in the areas of contamination or otherwise comeinto contact with the contamination at these sites, therefore, no health threat is posed to base employees. In some cases, portions of a building or entire buildings are contaminated; in these cases, thecontaminated areas are secured from entry.
  • No future exposure scenarios were identified. Exposure of site clean-up workers and employees tocontaminants is minimized or prevented through implementation of Health and Safety Plans andenvironmental surveillance monitoring during clean-up activities.
Removal actions were completed at these sites in 1996.
NSWC: Sites 1, 2, 3, 4, 6,7, 8, 9, 10, 13, 14,15, 16, 17, 18, 19,20, 21, 22, 23, 24,25, 26, 27, 28, 29These sites are designated for future (unscheduled)Site Screening Activities.
NSWC: Sites 43, 44, 45,48, 50These sites are proposed for future (unscheduled)Remedial Investigation/Feasibility Study activities
NSWC: Sites 11, 12, 39,42, 43, 46, 47, 49,53, 54, 55, 56These sites are proposed as "high priority" sites forRemedial Investigation /Feasibility Study activitiesbeginning in 1997.
Stump Neck: Sites 30, 31, 32,33, 34, 35, 36, 37,38

This property has been used primarily for explosives training, mixing, assembly, and disassembly ofordnance, The RCRA Facility Assessment evaluation documents few releases of hazardous substancesto the environment. Characterization and clean-up of these sites will proceed under the RCRACorrective Action Program.

ATSDR's primary concern with the Stump Neck Annexrelates to releases of contaminants to the Mattawomanand Chicamuxen Creeks entering the aquatic foodchain.


The following section was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:

Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services Branch
1600 Clifton Road NE, Atlanta, Georgia 30333


ATSDR Public Health Assessment Conclusion Categories
A. Urgent public health hazard This category is used for sites that pose an urgent publichealth hazard as the result of short-term exposures tohazardous substances.
  • evidence exists that exposures have occurred, are occurring, or are likely to occurin the future AND
  • estimated exposures are to a substance(s) at concentrations in the environmentthat, upon short-term exposures, can cause adverse health effects to anysegment of the receptor population AND/OR
  • community-specific health outcome data indicate that the site has had an adverseimpact on human health that requires rapid intervention AND/OR
  • physical hazards at the site pose an imminent risk of physical injury
B. Public health hazardThis category is used for sites that pose a public healthhazard as the result of long-term exposures to hazardoussubstances.
  • evidence exists that exposures have occurred, are occurring, or are likely to occurin the future AND
  • estimated exposures are to a substance(s) at concentrations in the environmentthat, upon long-term exposures, can cause adverse health effects to anysegment of the receptor population AND/OR
  • community-specific health outcome data indicate that the site has had an adverseimpact on human health that requires intervention
C. Potential (indeterminate) public health hazardThis category is used for sites with incomplete information.
  • limited available data do not indicate that humans are being or have been exposedto levels of contamination that would be expected to cause adverse health effects;data or information are not available for all environmental media to which humans may be exposed AND
  • there are insufficient or no community-specific health outcome data to indicate thatthe site has had an adverse impact on human health
D. No apparent public health hazardThis category is used for sites where human exposure tocontaminated media is occurring or has occurred in the past,but the exposure is below a level of health hazard.
  • exposures do not exceed an ATSDR chronic MRL or other comparable value AND
  • data are available for all environmental media to which humans are being exposed AND
  • there are no community-specific health outcome data to indicate that the site hashad an adverse impact on human health
E. No public health hazardThis category is used for sites that do not pose a public healthhazard.
  • no evidence of current or past human exposure to contaminated media AND
  • future exposures to contaminated media are not likely to occur AND
  • there are no community-specific health outcome data to indicate that the site hashad an adverse impact on human health

APPENDIX D:Application, to the NSWC-IHDIV soil data set, of the algorithmrelating soil lead concentrations to potential increases in blood leadlevels. References are noted inparentheses.

Application of the Algorithm
The following formula describes the observed relationship between soil lead concentrationsand increases in blood lead (PbB) levels (9):

ln(PbB) = 0.879 + 0.241 ln(Pb soil)

where the PbB data are expressed in units of µg/dL and the concentrations of lead in soil (Pb soil) are expressed as parts per million (ppm) (i.e., µg/g, mg/kg).

If the baseline PbB levels are defined, and the potential increase in PbB levels is calculatedusing the above formula, the sum of the two values provides an estimate of the predicted totallead concentration in blood if blood lead testing were performed. This value is compared tothe CDC public health PbB screening criterion for children of 10 µg/dL to determine if PbBtesting of the exposed population is recommended (9):

    Testing is recommended if:
      PbB baseline level + increase in PbB > 10 µg/dL

    Testing is not recommended if:

      PbB baseline level + increase in PbB < 10 µg/dL


Baseline blood lead (PbB) levels
Baseline PbB values in exposed communities will vary depending on a number of socio-demographic factors including age, gender, race, income level, and environment (7).The National Health and Nutrition Examination Survey (NHANES) for 1976 - 1991 providesbaseline PbB data for the U.S. population (11). These data are averaged over age groupcategories for children, e.g, 1-2 years, 3-5 years, 6-11 years, etc. Neither baseline PbB datanor site-specific demographic data were available for the children residing in the NSWC-IHDIVhousing; therefore, for the purposes of these calculations it was assumed that the meanbaseline PbB values at the facility are not significantly different from the national averages forthe overall U.S. population (11). Based on the CDC recommendation for blood lead screeningof children ages 6 years and under (9), we used the NHANES 1-2 year and 3-5 year age group mean values:

AgeMean PbB level (µg/dL)
1-2 years
3-5 years

The calculations assume that the children regularly play in the lead-contaminated soils aroundthe NSWC-IHDIV housing : this may lead to an overestimate in the potential increase in PbBlevels due to soil exposure. However, the calculations do not integrate the increases in PbBwhich may occur due to exposure to other sources of lead in the NSWC-IHDIV residentialsetting including inhalation and ingestion of household dusts and ingestion of indoor paintchips.


All NSWC-IHDIV soil lead data values were obtained from the NSWC-IHDIV HousingInspection Report (8). The average soil lead concentration was calculated for each unit in eachhousing area: samples collected from foundation garden, pedestrian path and play areas wereused. (Data from background and roadside samples were not included in the calculations.) Thehousing unit with the highest average soil lead concentration for a particular housing area wasused in the PbB calculations. These calculations are presented below.

Detached Housing

Average foundation soil Pb concentrations ranged from 88.6 (115 Strauss) to 12,669 (7 Pickens) ppm for the NSWC-IHDIV Detached housing units.

For the highest average soil Pb concentration (7 Pickens), the calculated potential increase inPbB is 23.5 µg/dL:

      ln (PbB) = 0.879 + 0.241 ln(12,669)
      ln (PbB) = 3.155
      PbB = 23.5 µg/dL

The predicted increase in PbB due to exposure to lead contaminated soils at this averageconcentration exceeds the screening criterion. Compare the sum of the baseline PbB andincrease in PbB to the screening criterion of 10 µg/dL:

      1-2 years 4.1 + 23.5 = 27.6 µg/dL PbB
      3-5 years 3.4 + 23.5 = 26.9 µg/dL PbB
For children 5 years of age and under, the predicted PbB levels exceed the screening criterion of 10 µg/dL by a factor of two.

La Plata Housing
The highest average lead concentration in soils at the La Plata housing units = 1213.5 ppm(Unit 6).

For the highest average soil Pb concentration, the calculated potential increase in PbB is 13.3µg/dL:

      ln (PbB) = 0.879 + 0.241 ln(1213.5)
      ln (PbB) = 2.59
      PbB = 13.3 µg/dL

Compare the sum of the baseline PbB and increase in PbB to the screening criterion of 10µg/dL:

      1-2 years       4.1 + 13.3 = 17.4 µg/dL PbB
      3-5 years       3.4 + 13.3 = 16.7 µg/dL PbB

For children 5 years of age and under, the predicted PbB levels exceed the screening criterionof 10 µg/dL.

Waldorf Housing
The highest average lead concentration in soils at the Waldorf housing units = 483 ppm (Unit2).

For the highest average soil Pb concentration, the calculated potential increase in PbB is 10.7 µg/dL:

      ln (PbB) = 0.879 + 0.241 ln(483)
      ln (PbB) = 2.36
      PbB = 10.7 µg/dL

Compare the sum of the baseline PbB and increase in PbB to the screening criterion of 10µg/dL:

      1-2 years       4.1 + 10.7 = 14.8 µg/dL PbB
      3-5 years       3.4 + 10.7 = 14.1 µg/dL PbB

For children 5 years of age and under, the predicted PbB levels exceed the screening criterionof 10 µg/dL.

Riverview Village Apartments
The highest average lead concentration in soils at the Riverview apartments = 91.5 ppm (Unit16).

For the highest average soil Pb concentration, the calculated potential increase in PbB is 7.1 µg/dL:

      ln (PbB) = 0.879 + 0.241 ln(91.5)
      ln (PbB) = 1.96
      PbB = 7.1 µg/dL

Compare the sum of the baseline PbB and increase in PbB to the screening criterion of 10µg/dL:

      1-2 years       4.1 + 7.1 = 11.2 µg/dL PbB
      3-5 years       3.4 + 7.1 = 10.5 µg/dL PbB

For children 5 years of age and under, the predicted PbB levels exceed the screening criterionof 10 µg/dL.

APPENDIX E: ATSDR Public Health Statement on Mercury



This Statement was prepared to give you information about mercury and to emphasize thehuman health effects that may result from exposure to it. The Environmental ProtectionAgency (EPA) has identified 1,300 hazardous waste sites as the most serious in the nation.These sites comprise the "National Priorities List" (NPL): Those sites which are targeted forlong-term federal cleanup activities. Mercury has been found in at least 600 of the sites onthe NPL. However, the number of NPL sites evaluated for mercury is not known. As EPAevaluates more sites, the number of sites at which mercury is found may increase. Thisinformation is important because exposure to mercury may cause harmful health effects andbecause these sites are potential or actual sources of human exposure to mercury.

When a substance is released from a large area, such as an industrial plant, or from acontainer, such as a drum or bottle, it enters the environment. This release does not alwayslead to exposure. You can be exposed to a substance only when you come in contact with it.You may be exposed by breathing, eating, or drinking substances containing the substance orby skin contact with it.

If you are exposed to a substance such as mercury, many factors will determine whetherharmful health effects will occur and what the type and severity of those health effects will be.These factors include the dose (how much), the duration (how long), the route or pathway bywhich you are exposed (breathing, eating, drinking, or skin contact), the other chemicals towhich you are exposed, and your individual characteristics such as age, gender, nutritionalstatus, family traits, life-style, and state of health.


Mercury is a metal (element) that occurs naturally in the environment in several forms. In themetallic or elemental form, mercury is a shiny, silver-white, odorless liquid familiar to anyonewho has used a mercury thermometer. Some evaporation of metallic mercury occurs at roomtemperature to form mercury vapor, a colorless, odorless gas. Some people who havebreathed mercury vapors report a metallic taste in their mouth. Mercury can also combinewith other elements, such as chlorine, sulfur, or oxygen, to form inorganic mercury compoundsor "salts". Most inorganic mercury compounds are white powders or crystals, except formercuric sulfide (also known as cinnabar) which is red and turns black after exposure to light.In the following text, we include both metallic mercury (liquid and vapor) and inorganicmercury compounds under the generic term "inorganic mercury."

Mercury can also form a chemical bond with carbon to create a large number oforganomercurial compounds. It is customary to refer to mercury with bonds to carbon as"organic" mercury. However, only two of these organomercurial compounds (methylmercuryand phenylmercury) have been identified at hazardous waste sites. In most instances in thetext, we refer to these chemicals by name rather than using the generic term "organicmercury." Like the inorganic mercury compounds, both methylmercury and phenylmercuryexist as "salts" (for example methylmercuric chloride or phenylmercuric acetate). When pure,most forms of methylmercury and phenylmercury are white crystalline solids.

Several mercury compounds are found naturally in the environment. The most common formsof mercury naturally found in the environment are metallic mercury, mercuric sulfide, mercuricchloride, and methylmercury. The mercury portion of these forms does not break down intoother chemicals. However, the form of mercury found in the environment can be changedslowly by microorganisms and natural processes. Metallic mercury vapor may be changedinto inorganic forms, such as mercuric chloride, and inorganic forms may be changed inorganic forms of mercury (and vice versa). Methylmercury is the usual organic form ofmercury created by these natural processes. It is of particular concern because it can build upin certain fish to levels that are many times greater than in the surrounding water (seeSection 1.2)*.

Mercury is mined as mercuric sulfide. Metallic mercury is then refined from the mercuricsulfide by heating the ore above 1000 degrees Fahrenheit and capturing the metallic mercuryvapor that is released. There are many different uses for metallic mercury. It is used in theproduction of chlorine gas and caustic soda. It is also used in thermometers, barometers,batteries, and electrical switches. Silver-colored dental fillings typically contain about 50%metallic mercury. Metallic mercury is also used to extract gold from ore or to reclaim gold fromgold-containing articles. Some Mexican-American and Asian populations have used metallicmercury in folk remedies for chronic stomach disorders. Metallic mercury has also been usedby Latin-American and Caribbean cultures in occult practices. Inorganic salts of mercury,such as ammoniated mercuric chloride or mercuric iodide, have been used in skin lighteningcreams. Mercuric chloride has also been used as a topical antiseptic or disinfectant agent.Some chemicals containing mercury, such as mercurochrome and thimerosal, are stillcommonly used in medicine as antiseptics or as preservatives in eye drops, eye ointments,nasal sprays, and vaccines. Neither mercurochrome or thimerosal have been identified athazardous waste sites. Mercuric sulfide and mercuric oxide are used as pigments in paints.Mercuric sulfide is also used as a pigment for tattoos. Mercurous chloride was widely used atone time in medicinal products, such as laxatives, worming medications, and teethingpowders. It has since been replaced by safer and more effective agents. Some inorganicmercury compounds are used in fungicides.

Methylmercury is generally produced by microorganisms in the environment, rather than madeby human activity. However, at one time methyl- and ethylmercury compounds were used toprotect seed grains from fungal infections. This use has been banned since the 1970s.Phenylmercuric compounds were used as antifungal agents in paints until 1991, when thisuse was also stopped. Mercury compounds may be found in the air, soil, and water nearhazardous waste sites. Chapter 3 contains more information on the physical and chemicalproperties of mercury. Chapter 4 contains more information on the production and use ofmercury.


Mercury is a naturally occurring metal found throughout the environment as the result ofnormal breakdown of minerals in the earth's crust by weathering processes involving wind andwater. The total amount of mercury entering the environment from natural processesthroughout the world is about equal to, or maybe less than, the total amount released byhuman activities. However, with the exception of mercury ore deposits, the amount of mercurythat naturally exists in any one place is usually very low. In contrast, the amount of mercurythat may be found at a particular waste site because of human activity can be high. Themercury in air, water, and soil at hazardous waste sites may come from both natural sourcesand human activity.

Most of the mercury found in the environment is inorganic mercury (metallic mercury andinorganic mercury compounds). This inorganic mercury can enter the air from deposits of orethat contain mercury, from the burning of coal or garbage, and from the emissions of factoriesthat use mercury. Inorganic mercury may also enter water or soil from rocks that containmercury, factories or water treatment facilities that release water contaminated with mercury,and the disposal of wastes. Inorganic or organic compounds of mercury may be released tothe soil through the use of mercury- containing fungicides.

Metallic mercury is a liquid at room temperature. It can evaporate into the air and can becarried long distances before returning to water or soil in rain or snow. As mentioned before,some microorganisms in the water or soil can change inorganic forms of mercury tomethylmercury. Methylmercury can enter the water and remain there for a long time,particularly if there are particles in the water to which the methylmercury can attach. Ifmercury enters the water in any form, it is likely to settle to the bottom where it can remain fora long time. Mercury also remains in soil for a long time. Mercury usually stays on the surfaceof the sediments or soil and does not move through the soil to underground water.

Small fish and other organisms living in the water can take up methylmercury and inorganicforms of mercury. When larger fish eat small fish or other organisms that containmethylmercury, most of the methylmercury originally present in the small fish will be stored inthe bodies of the large fish. As a result, large fish living in contaminated waters can collect arelatively large amount of methylmercury. Plants may have a greater concentration ofinorganic mercury in them if they are grown in soil that contains higher than normal amountsof mercury. For further information on what happens to mercury in the environment, refer toChapters 4 and 5.


Because mercury occurs naturally in the environment, everyone is exposed to very low levelsof mercury in air, water, and food. However, some people may be exposed to higher levels ofmercury. One of the most likely ways that the general population will be exposed to higherlevels of mercury is through eating fish or shellfish contaminated with methylmercury. Somefish contain such high levels of methylmercury that selling them for human consumption hasbeen prohibited. In addition, public health advisories have been issued by state and federalauthorities to discourage anyone from catching fish from some areas for human consumption.Other foods typically contain very little methylmercury or other forms of mercury. The othermost likely form of exposure is by absorbing mercury vapors released from dental fillings.Most silver-colored dental fillings are about 50% metallic mercury and slowly release smallamounts of mercury vapor.

Sources of higher exposure to mercury include breathing air containing mercury vaporsreleased from metallic mercury spills, incinerators, and facilities that burn mercury-containingfuels (for example, coal or other fossil fuels). Exposure near hazardous waste sites is likely tooccur by breathing contaminated air, having contact with contaminated soil, or drinkingcontaminated water. Persons may be exposed to mercury compounds in medicinal products,such as antiseptics or skin lightening creams, that contain small amounts of mercury.

In the past, the level of mercury found in outdoor air has been reported to be between 10 and20 nanograms of mercury per cubic meter (ng/m3) of air in urban areas. Background or natural levels are generally about 6 ng/m3 or less. Mercury levels found in surface water aregenerally less than 5 ng per liter of water. Levels normally found in soil range from 20 to 625ng of mercury per gram of soil. The Food and Drug Administration (FDA) has estimated that,on average, most people are exposed to about 50 ng of mercury per kilogram of body weightper day in the food they eat. This amount translates to about 3.5 micrograms (mg) of mercuryper day for an adult of average weight. A large proportion of this mercury, in the form ofmethylmercury, is likely to come from fish. Furthermore, people who eat a lot of fish are likelyto have higher exposure to methylmercury. Mothers with mercury in their blood can exposetheir unborn children to methylmercury. Infants who nurse can be exposed to methylmercuryand inorganic mercury in their mother's milk.

Workers in some occupations may also be exposed to inorganic mercury (metallic andinorganic mercury compounds) in the workplace. Most exposures on the job occur as a resultof breathing air that contains mercury vapors. Exposure occurs in the medical, dental, andother health services, and in the chemical, metal processing, electrical equipment, automotive,building, and other industries. Families of workers may be exposed to mercury in the home ifthe workers' clothes have been contaminated with mercury. Dentists and their assistants mayalso be exposed to metallic mercury from skin contact with materials used to fill cavities in the teeth and breathing metallic mercury vapor released from these materials.

Exposure to mercury can be determined by measuring amounts in blood, urine, and hair.Levels found in blood, urine, or hair may show whether health effects are expected (seeSection 2.5). Refer to Chapter 5 for more information on how you might be exposed tomercury.


Mercury can easily enter your body when you breathe in air containing metallic mercury vapor.Most of the mercury vapor you breathe in enters your bloodstream and goes rapidly to otherparts of the body. Inhaled metallic mercury can reach the fetuses of pregnant women easily.Some metallic mercury can be changed by your body into mercuric chloride. Some mercurythat enters your bloodstream as metallic mercury may stay in your body for weeks or months.It stays mostly in the kidney and brain, as either metallic mercury or mercuric chloride. Metallicmercury that you breathe in will leave your body in the urine, feces, and breath. Metallicmercury that you might swallow in the liquid form does not enter the bloodstream very easily,and most of it leaves the body in the feces.

Inorganic salts of mercury (mercurous chloride or mercuric chloride, for example) that areinhaled are not believed to enter your body as easily as inhaled metallic mercury vapor.However, these inorganic forms of mercury, if swallowed, enter the body more easily thanmetallic mercury. Inorganic mercury can also enter the bloodstream directly through the skin.However, only a small amount would pass through your skin compared with breathing orswallowing inorganic mercury. After entering the body, inorganic compounds of mercury canalso reach many tissues. Mercurous mercury in your body breaks down to metallic mercury and mercuric mercury. Some mercuric mercury may stay in your body, mostly in the kidneys.Mercuric salts of mercury cannot reach the brain as easily as metallic mercury. Inorganicmercury leaves your body in the urine or feces over a period of several weeks or months.

Some organic compounds of mercury (such as methylmercury) can evaporate slowly at roomtemperature and can enter your body easily as vapors through the lungs. Methylmercury incontaminated fish or other foods that you might eat enters your bloodstream easily and goesrapidly to other parts of your body. It can also enter the bloodstream directly through the skin,but only in small amounts. Organic mercury compounds (such as methylmercury) that are inthe bloodstream are similar to metallic mercury because they can reach most tissues includingthe brain and fetus. Methylmercury can change to inorganic mercury in the brain and remainthere for a long time. Methylmercury that you swallow or breathe leaves your body in thefeces, mostly as inorganic mercury. It leaves the body over a period of several months Formore information on how mercury can enter and leave your body, please refer to Chapter 2.


Exposure to high enough levels of metallic, inorganic, or organic mercury can permanentlydamage the brain, kidneys, and developing fetus. The nervous system is very sensitive tomercury's effects. The changes that mercury causes in the brain are not specific for one typeof brain function. Therefore, a variety of effects may occur. These effects include personalitychanges (irritability, shyness, nervousness), tremors, changes in vision or hearing, anddifficulties with memory. Because of differences in the way that different forms of mercury areable to travel through the body, not all forms of mercury are equally able to affect the nervoussystem. For example, breathing in large amounts of metallic mercury vapors and breathing inor swallowing large amounts of methylmercury are more likely to cause nervous systemeffects than swallowing large amounts of inorganic mercury salts. This difference is becausemercury transport into the brain is very low after exposure to inorganic salts of mercury, suchas mercuric chloride. Therefore, exposure to this form of mercury is less likely to causenervous system toxicity. The extent of recovery depends on what kind of nervous systemdamage mercury caused.

The kidney is also very sensitive to mercury. All forms of mercury are able to cause kidneydamage if large enough amounts enter the body. Recovery from the kidney effects of mercuryis likely, once the body clears itself of the contamination, if the damage caused by themercury is not too great.

In addition to the effects described above, short-term exposure to high levels of metallicmercury vapor in the air can damage the lungs, cause nausea, vomiting, or diarrhea, causeincreases in blood pressure or heart rate, and cause skin rashes or eye irritation. Long-termexposure of workers in several industries to metallic mercury has been shown to cause similareffects. Levels of metallic mercury in air were greater than the levels normally encountered bythe general population. Current levels of mercury in workplace air are lower than in the past.Because of this reduction, fewer workers are expected to have symptoms from mercuryexposure. Results of studies in humans showed that there were no effects on the ability tohave children after breathing metallic mercury for a long time. Studies in workers exposed tometallic mercury vapors have not shown an increase in cancer. Skin contact with the metalmercury causes allergic reactions (skin rashes) in some people.

Other than effects on the kidneys, little is known about the effects of inorganic mercury saltson the body. Some people have shown nausea and diarrhea after swallowing large amountsof inorganic mercury salts, and some have shown nervous system effects. There is noinformation on long-term, low-level exposures in humans.

People who have eaten fish containing large amounts of methylmercury or seed grains treatedwith methylmercury or other organic mercury compounds have had permanent damage to thebrain, kidneys, and the growing fetus. The amounts of organic mercury that cause theseeffects are higher than the amounts to which the general population is exposed daily.Exposure to methylmercury may cause brain damage in the developing fetus. Exposure tomethylmercury is also likely to be more dangerous for young children than for adults. This isbecause relatively more methylmercury passes into the brains of young children than adults,and because methylmercury interferes with brain development.

Studies in animals show similar effects to those seen in people. Studies in animals have alsoprovided more information on types of exposure for which human data are limited. Forexample, studies in animals provide information about the effects of long-term exposure tomercury through food, water, or inhaled dust. These studies show that long-term oralexposure to inorganic mercury salts can cause kidney damage, effects on blood pressure andheart rate, and effects on the stomach. Studies in animals also provide important informationabout an autoimmune reaction that may occur in sensitive populations after swallowinginorganic mercury salts. Some studies in animals also show that nervous system damageoccurs after long-term exposure to high levels of inorganic mercury. Short- term high levelexposure to inorganic mercury affects the fetus in animals. The general population isgenerally not exposed to levels high enough to produce these effects.

In addition to the effects observed in people who have eaten food contaminated withmethylmercury, studies in animals exposed to methylmercury or phenylmercury show thatlong-term exposure to high levels can cause kidney damage, damage to the stomach andlarge intestine, changes in blood pressure and heart rate, adverse effects on the developingfetus, sperm, and male reproductive organs, and increases in the number of spontaneousabortions and stillbirths. Adverse effects on the nervous system of animals occurred at lowerdoses than most other effects. This difference indicates that the nervous system is moresensitive to methylmercury toxicity than other organs in the body.

Studies also show that animals given inorganic mercury salts by mouth for most of theirlifetime had increases in some kinds of tumors. Animals that received methylmercury orphenylmercury in their drinking water or feed for most of their lives had increases in cancer ofthe kidney. There is no information to show that mercury causes cancer in humans. TheDepartment of Health and Human Services (DHHS), EPA, and the International Agency forResearch on Cancer (IARC) have not classified mercury as to its human carcinogenicity.Chapter 2 contains information on health effects of mercury in humans and animals.


There are reliable, accurate, and easily available ways to measure mercury levels in the body.However, the most easily available tests do not determine the form of mercury to which youmight have been exposed. Blood or urine samples can be taken in a doctor's office andtested using special equipment in a laboratory. Mercury in urine is used to test for exposure tometallic mercury vapor and to inorganic forms of mercury. Blood levels are measured lessfrequently. Measurement of mercury in whole blood or scalp hair is also used to monitorexposure to methylmercury. Urine is not useful for testing whether exposure has occurred tomethylmercury. Levels found in blood, urine, and hair may be used to predict possible healtheffects that may be caused by the different forms of mercury.

Levels of mercury found in the urine provide information about recent exposures better thanabout long-term exposures. Blood and urine levels are useful during and after short- andlong-term exposures. However, several months after exposure ends, mercury levels in theblood and urine are much lower. Hair can be used to show exposures that occurred manymonths ago, or even more than a year ago if the hair is long enough and careful testingmethods are used. These methods for hair analysis are not easily available. Short-termexposure to mercury can also be evaluated by measuring mercury in the breath, but onlywithin a few days after exposure. For more information on testing for mercury levels in thebody, see Chapters 2 and 6.


The government has developed regulations and guidelines for mercury. EPA has establishedmany regulations to control air pollution. These are designed to protect the public from thepossible harmful health effects of mercury.

EPA and the FDA have set a limit of 2 parts mercury per billion (ppb) parts of water in drinkingwater. EPA also recommends that the level of inorganic mercury in rivers, lakes, and streamsshould be no more than 144 parts mercury per trillion (ppt) parts of water to protect humanhealth (1 ppt is a thousand times less than 1 ppb). EPA suggests that a daily exposure to 2ppb of mercury in drinking water for an adult of average weight is not likely to cause anysignificant adverse health effects. The FDA has set a maximum permissible level of 1 part ofmethylmercury in a million parts (ppm) of seafood products (1 ppm is a thousand times morethan 1 ppb). The FDA also may seize treated seed grain containing more than 1 ppm ofmercury.

The Occupational Safety and Health Administration (OSHA) regulates levels in the workplace.It has set a limit of 0.01 mg/m3 for organic mercury and 0.05 mg/m3 for metallic mercury vaporin the workplace air to protect workers during an %-hour shift and a 40-hour work week. TheNational Institute for Occupational Safety and Health (NIOSH) recommends that the amount of metallic mercury vapor in workplace air be limited to 0.05 mg/m3 averaged over a 10-hour work shift.


If you have any more questions or concerns, please contact your community or state health orenvironmental quality department or:

    Agency for Toxic Substances and Disease Registry
    Division of Toxicology
    1600 Clifton Road NE, E-29
    Atlanta, Georgia 30333

This agency can also provide you with information on the location of occupational andenvironmental health clinics. These clinics specialize in the recognition, evaluation, andtreatment of illness resulting from exposure to hazardous substances.

*Note: This Public Health Statement on mercury is derived from the ATSDR Toxicological Profile forMercury (Reference 17). Section and chapter references in the public health statement are contained inthe toxicological profile.

Table of Contents The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

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