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Public Health Assessment
Drinking Water Supplies and Groundwater Pathway Evaluation,
Isla de Vieques Bombing Range,
Vieques, Puerto Rico
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October 16, 2001
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry
ATSDR Plain Language Glossary of Environmental Health Terms
- Adverse Health Effect:
- A change in body function or the structures of cells that can lead to disease or health problems.
- The Agency for Toxic Substances and Disease Registry. ATSDR is a federal health agency in Atlanta, Georgia that deals with hazardous substance and waste site issues. ATSDR gives people information about harmful chemicals in their environment and tells people how to protect themselves from coming into contact with chemicals.
- Used in public health, things that humans would eat - including animals, fish and plants.
- A group of diseases which occur when cells in the body become abnormal and grow, or multiply, out of control
- Any substance shown to cause tumors or cancer in experimental studies.
- Chronic Exposure:
- A contact with a substance or chemical that happens over a long period of time. ATSDR considers exposures of more than one year to be chronic.
- Completed Exposure Pathway:
- See Exposure Pathway.
- Comparison Value (CVs):
- Concentrations or the amount of substances in air, water, food, and soil that are unlikely, upon exposure, to cause adverse health effects. Comparison values are used by health assessors to select which substances and environmental media (air, water, food and soil) need additional evaluation while health concerns or effects are investigated.
- Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA):
- CERCLA was put into place in 1980. It is also known as Superfund. This act concerns releases of hazardous substances into the environment, and the cleanup of these substances and hazardous waste sites. ATSDR was created by this act and is responsible for looking into the health issues related to hazardous waste sites.
- A belief or worry that chemicals in the environment might cause harm to people.
- How much or the amount of a substance present in a certain amount of soil, water, air, or food.
- See Environmental Contaminant.
- Dermal Contact:
- A chemical getting onto your skin. (see Route of Exposure).
- The amount of a substance to which a person may be exposed, usually on a daily basis. Dose is often explained as "amount of substance(s) per body weight per day".
- Dose / Response:
- The relationship between the amount of exposure (dose) and the change in body function or health that result.
- The amount of time (days, months, years) that a person is exposed to a chemical.
- Environmental Contaminant:
- A substance (chemical) that gets into a system (person, animal, or the environment) in amounts higher than that found in Background Level, or what would be expected.
- Environmental Media:
- Usually refers to the air, water, and soil in which chemicals of interest are found. Sometimes refers to the plants and animals that are eaten by humans. Environmental Media is the second part of an Exposure Pathway.
- U.S. Environmental Protection Agency (EPA):
- The federal agency that develops and enforces environmental laws to protect the environment and the public's health.
- The study of the different factors that determine how often, in how many people, and in which people will disease occur.
- Coming into contact with a chemical substance. (For the three ways people can come in contact with substances, see Route of Exposure.)
- Exposure Assessment:
- The process of finding the ways people come in contact with chemicals, how often and how long they come in contact with chemicals, and the amounts of chemicals with which they come in contact.
- Exposure Pathway:
- A description of the way that a chemical moves from its source (where it began) to where and how people can come into contact with (or get exposed to) the chemical.
ATSDR defines an exposure pathway as having 5 parts:
- Source of Contamination,
- Environmental Media and Transport Mechanism,
- Point of Exposure,
- Route of Exposure, and
- Receptor Population.
When all 5 parts of an exposure pathway are present, it is called a Completed Exposure Pathway. Each of these 5 terms is defined in this Glossary.
- How often a person is exposed to a chemical over time; for example, every day, once a week, twice a month.
- Hazardous Waste:
- Substances that have been released or thrown away into the environment and, under certain conditions, could be harmful to people who come into contact with them.
- Health Effect:
- ATSDR deals only with Adverse Health Effects (see definition in this Glossary).
- Indeterminate Public Health Hazard:
- The category is used in Public Health Assessment documents for sites where important information is lacking (missing or has not yet been gathered) about site-related chemical exposures.
- Swallowing something, as in eating or drinking. It is a way a chemical can enter your body (See Route of Exposure).
- Breathing. It is a way a chemical can enter your body (See Route of Exposure).
- Compounds that do not contain hydrocarbon groups.
- A narrow passage connecting two larger cavities.
- Lowest Observed Adverse Effect Level. The lowest dose of a chemical in a study, or group of studies, that has caused harmful health effects in people or animals.
- Maximum Contaminant Level. The standard set by EPA for drinking water within public water supply systems. EPA considers the protection of human health when setting the MCL.
- Minimal Risk Level. An estimate of daily human exposure - by a specified route and length of time -- to a dose of chemical that is likely to be without a measurable risk of adverse, noncancerous effects. An MRL should not be used as a predictor of adverse health effects.
- The National Priorities List. (Which is part of Superfund.) A list kept by the U.S. Environmental Protection Agency (EPA) of the most serious, uncontrolled or abandoned hazardous waste sites in the country. An NPL site needs to be cleaned up or is being looked at to see if people can be exposed to chemicals from the site.
- No Observed Adverse Effect Level. The highest dose of a chemical in a study, or group of studies, that did not cause harmful health effects in people or animals.
- No Apparent Public Health Hazard:
- The category is used in ATSDR's Public Health Assessment documents for sites where exposure to site-related chemicals may have occurred in the past or is still occurring but the exposures are not at levels expected to cause adverse health effects.
- No Public Health Hazard:
- The category is used in ATSDR's Public Health Assessment documents for sites where there is evidence of an absence of exposure to site-related chemicals.
- Military materiels such as weapons, ammunition, combat vehicles, and equipment.
- Compounds containing carbon.
- Public Health Assessment. A report or document that looks at chemicals at a hazardous waste site and tells if people could be harmed from coming into contact with those chemicals. The PHA also tells if possible further public health actions are needed.
- Point of Exposure:
- The place where someone can come into contact with a contaminated environmental medium (air, water, food or soil). For examples:
the area of a playground that has contaminated dirt, a contaminated spring used for drinking water, the location where fruits or vegetables are grown in contaminated soil, or the backyard area where someone might breathe contaminated air.
- A group of people living in a certain area; or the number of people in a certain area.
- Public Health Hazard:
- The category is used in PHAs for sites that have certain physical features or evidence of chronic, site-related chemical exposure that could result in adverse health effects.
- Public Health Hazard Criteria:
- PHA categories given to a site which tell whether people could be harmed by conditions present at the site. Each are defined in the Glossary. The categories are:
- Urgent Public Health Hazard
- Public Health Hazard
- Indeterminate Public Health Hazard
- No Apparent Public Health Hazard
- No Public Health Hazard
- Receptor Population:
- People who live or work in the path of one or more chemicals, and who could come into contact with them (See Exposure Pathway).
- Reference Dose (RfD):
- An estimate, with safety factors (see safety factor) built in, of the daily, life-time exposure of human populations to a possible hazard that is not likely to cause harm to the person.
- Route of Exposure:
- The way a chemical can get into a person's body. There are three exposure routes:
- breathing (also called inhalation),
- eating or drinking (also called ingestion), and
- or getting something on the skin (also called dermal contact).
- Safety Factor:
- Also called Uncertainty Factor. When scientists don't have enough information to decide if an exposure will cause harm to people, they use "safety factors" and formulas in place of the information that is not known. These factors and formulas can help determine the amount of a chemical that is not likely to cause harm to people.
- Semi-volatile organic compound (SVOC):
- A class of organic (carbon-containing) chemicals similar to VOCs, but that evaporate, or volatilize, less readily.
- The Secondary Maximum Contaminant Level is established based on secondary considerations such as taste, odor, and appearance, when health concerns are not an issue.
- Source (of Contamination):
- The place where a chemical comes from, such as a landfill, pond, creek, incinerator, tank, or drum. Contaminant source is the first part of an Exposure Pathway.
- Special Populations:
- People who may be more sensitive to chemical exposures because of certain factors such as age, a disease they already have, occupation, sex, or certain behaviors (like cigarette smoking). Children, pregnant women, and older people are often considered special populations.
- Harmful. Any substance or chemical can be toxic at a certain dose (amount). The dose is what determines the potential harm of a chemical and whether it would cause someone to get sick.
- The study of the harmful effects of chemicals on humans or animals.
- Abnormal growth of tissue or cells that have formed a lump or mass.
- Urgent Public Health Hazard:
- This category is used in ATSDR's Public Health Assessment documents for sites that have certain physical features or evidence of short-term (less than 1 year), site-related chemical exposure that could result in adverse health effects and require quick intervention to stop people from being exposed.
- Volatile Organic Compound (VOC):
- A class of organic (carbon-containing) chemicals which readily evaporate, or volatilize. VOCs are frequently used as solvents, degreasing agents, and in other industrial applications.
|Chemicals Sampled||Date Sampled|
|Arcadia Tank||Naval Ammunitions Support Detachment (NASD)||Public water supply tank owned by Puerto Rico Aqueduct and Sewer Authority (PRASA)||Puerto Rico Department of Health (DOH)||June 1999a|
|United States Environmental Protection Agency (USEPA)||September 1999
|NASD Tank||NASD||Navy water supply tank (water is supplied from the mainland)||USEPA||September 1999
|The Navy's contractor||September 1999|
|Pilon Tank||Pilon||Public water supply tank owned by PRASA||USEPA||September 1999
|Esperanza Tank||Esperanza||Public water supply tank owned by PRASA||Puerto Rico DOH||June 1999a|
|Florida Tanks (2)||Florida||Public water supply tank owned by PRASA||Puerto Rico DOH||June 1999a|
|Martineau Tank||Martineau||Public water supply tank owned by PRASA||USEPA||September 1999
|Destino Tank||Destino||Public water supply tank owned by PRASA||USEPA||September 1999
|Leguillow Tank||West of Isabel Segunda||Public water supply tank owned by PRASA||USEPA||September 1999
|Los Chivos Tank||Los Chivos||Public water supply tank owned by PRASA||USEPA||September 1999
|Distribution Tank||Unknown||Public water supply tank owned by PRASA||Puerto Rico DOH||June 1999a|
|Agencia Comercial||Baldorioty Street||Tap connected to the public water supply||Puerto Rico DOH||June 1999|
|Rio Blanco Input & Output||Naguabo, Puerto Rico||Filtration plant for public water supply||USEPA||January 2000|
aPR DOH also sampled for nitrate and nitrite.
bUSEPA only sampled for explosives.
|Name||Location||Use||Sampling Agency||Chemicals Sampled||Date Sampled|
|Well 2-3||Martineau||Remote well used by the public when water supply is interrupted||United States Environmental Protection Agency (USEPA)||September 1999
|Well 3-7||Proyecto Barracon||Local well used by the public when the water supply is interrupted||USEPA||September 1999
|Sun Bay Wells (3)||Sun Bay||Emergency water supply wells owned by Puerto Rico Aqueduct and Sewer Authority (PRASA)||Puerto Rico Department of Health (DOH)||May 1995|
|B Wells (4)||Sun Bay||Prior to their abandonment in 1978, these wells were part of the Esperanza valley well field||Puerto Rico DOH||May 1995|
|Navy Well 14||Camp Garcia||Former drinking water well||The Navy's contractor||August 1999|
|Navy Wells (5)||NASD||Uncertain: one was a supply well (Navy Well 17)||The Navy's contractor||August 1999|
|U.S. Geological Survey||November 1996|
|Monitoring Wells (11)||Along the Eastern Maneuver Area (EMA) western boundary||Monitoring||The Navy's contractor||August 1999|
Appendix C: Sampled Chemicals
|Volatile Organic Compounds||EPA 1999b||Baker 1999||PR DOH 1999||PR DOH 1995|
|Bromomethane (Methyl bromide)|
|Chloromethane (Methyl chloride)|
|Dibromomethane (Methylene bromide)|
|Iodomethane (Methyl iodide)|
|Isobutanol (Isobutyl alcohol)|
|Methylene chloride (Dichloromethane)|
|Semi-volatile Organic Compounds||EPA 1999b||Baker 1999||PR DOH 1999||PR DOH 1995|
|2-Chloroethyl vinyl ether|
|4-Bromophenyl phenyl ether|
|4-Chlorophenyl phenyl ether|
|Butyl benzyl phthalate|
|4-Methyl phenol (p-cresol)|
|2-Methyl phenol (o-cresol)|
|Metals||EPA 1999b||Baker 1999||PR DOH 1999||PR DOH 1995|
|Inorganics||EPA 1999b||Baker 1999||PR DOH 1999||PR DOH 1995|
|Nitrate plus Nitrite|
|Total Dissolved Solids|
|Pesticides||Baker 1999||PR DOH 1999||PR DOH 1995|
|Ethyl parathion (Parathion)|
|Sulfotepp (Tetraethyl dithiopyrophosphate)|
|Herbicides||Baker 1999||PR DOH 1999||PR DOH 1995|
|PCBs/Dioxins/Furans||Baker 1999||PR DOH 1999||PR DOH 1995|
|Explosives||EPA 2000||Baker 1999||PR DOH 1999||CH2MHILL and Baker 1999|
|Cyclotrimethylene trinitramine (RDX)|
|Cyclotetramethylene tetranitramine (HMX)|
|Radionuclides||Baker 1999||PR DOH 1999|
|Miscellaneous||Baker 1999||PR DOH 1999|
Estimates of Human Exposure Doses and Determination of Health Effects
Overview of ATSDR's Methodology for Evaluating Potential Public Health Hazards:
ATSDR evaluated exposures to various sources of drinking water on Vieques. To do so, ATSDR derived exposure doses and compared them against health-based guidelines. ATSDR also reviewed relevant toxicological data to obtain information about the toxicity of contaminants of interest.
Deriving Exposure Doses:
ATSDR derived exposure doses (i.e., the amount of chemical a person is exposed to over time) for all chemicals detected in drinking water sources. When estimating exposure doses, health assessors evaluate 1) contaminant concentrations to which people may have been exposed and 2) length of time and the frequency of exposure. Together, these factors influence an individual's physiological response to chemical contaminant exposure and potential outcomes. Where possible, ATSDR used site-specific information about the frequency and duration of exposures. In cases where site-specific information was not available, ATSDR applied several conservative exposure assumptions to estimate exposures for residents of Vieques.
The following equation was used to estimate exposure to contaminants in drinking water:
|Conc.:||Maximum concentration in parts per million (ppm)|
|IR:||Ingestion rate: adult = 3 liters per day; child = 1.5 liter per day|
|EF:||Exposure frequency, or number of exposure events per year of exposure: 365 days/year|
|ED:||Exposure duration, or the duration over which exposure occurs: adult = 70 years; child = 6 years|
|BW:||Body weight: adult = 70 kg; child = 10 kg|
|AT:||Averaging time, or the period over which cumulative exposures are averaged (6 years or 70 years x 365 days/year for noncancer effects; 70 years x 365 days/year for cancer effects)|
Using Exposure Doses to Evaluate Potential Health Hazards:
ATSDR performs weight of evidence analyses to determine whether exposures might be associated with adverse health effects (noncancer and cancer). As part of this process, ATSDR examines relevant toxicologic, medical, and epidemiologic data to determine whether estimated doses are likely to result in adverse health effects. As a first step in evaluating noncancer effects, ATSDR compares estimated exposure doses to standard health guideline values, including ATSDR's minimal risk levels (MRLs) and EPA's reference doses (RfDs). The MRLs and RfDs are estimates of daily human exposure to a substance that are unlikely to result in noncancer effects over a specified duration. Estimated exposure doses that are less than these values are not considered to be of health concern. To be very protective of human health, MRLs and RfDs have built in "uncertainty" or "safety" factors that make them much lower than levels at which health effects have been observed. Therefore, if an exposure dose is higher than the MRL or RfD, it does not necessarily follow that adverse health effects will occur.
If health guideline values are exceeded, ATSDR examines the effect levels seen in the literature and more fully reviews exposure potential to help predict the likelihood of adverse health outcomes. ATSDR looks at human studies, when available, as well as experimental animal studies. This information is used to 1) describe the disease-causing potential of a particular contaminant and 2) compare site-specific dose estimates with doses shown to result in illness in applicable studies (known as the margin of exposure). For cancer effects, ATSDR also reviews genotoxicity studies to further understand the extent to which a contaminant might be associated with cancer outcomes. This process enables ATSDR to weigh the available evidence, in light of uncertainties, and offer perspective on the plausibility of adverse health outcomes under site-specific conditions.
For essential nutrients that do not have MRLs or RfDs (e.g., iron, magnesium, potassium, and sodium), ATSDR compares the estimated daily exposure doses to U.S. Food and Drug Administration's (FDA's) Daily Values. Because essential nutrients are important minerals that maintain basic life functions, certain doses are recommended on a daily basis.
Evaluation of Health Hazards Associated with Vieques:
Public Water Supply System:
After calculating exposure doses according to the equation and assumptions described above, all chemical doses (with the exception of chloroform) were below their corresponding MRLs or RfDs. The calculated exposure dose of chloroform for a child [0.011 milligrams per kilogram per day (mg/kg/day)] only slightly exceeded EPA's chronic RfD (0.01 mg/kg/day). When compared to actual doses seen in the literature for less serious health effects (15 mg/kg/day), the calculated exposure dose is too low to be of health concern.
The calculated exposure doses for the essential nutrients that were detected in the public water--iron (0.72 mg/day for adults and 0.36 mg/day for children), magnesium (11.1 mg/day for adults and 5.5 mg/day for children), potassium (3.9 mg/day for adults and 1.95 mg/day for children), and sodium (29.7 mg/day for adults and 14.9 mg/day for children)--were well within the Daily Values recommended by FDA (iron: 18 mg/day, magnesium: 400 mg/day, potassium: 3,500 mg/day, and sodium: 2,400 mg/day). The additional intake of these chemicals from the public water supply system does not pose a health hazard to the residents of Vieques.
Of the chemicals detected in the public water supply system, only the disinfection byproducts (chlorodibromomethane, chloroform, and dichlorobromomethane) and di(2-ethylhexyl)phthalate are known carcinogens. Using conservative exposure assumptions, ATSDR found that the levels of these chemicals do not pose a risk for excess cancer cases in the Vieques community. ATSDR does not expect any increase in cancer risk by drinking water from the public water supply system.
After calculating exposure doses according to the equation and assumptions described above, all chemical doses (with the exception of manganese and nitrate plus nitrite) were below their corresponding MRLs or RfDs. The exposure doses of manganese for adults (0.022 mg/kg/day) and children (0.08 mg/kg/day) slightly exceeded EPA's chronic RfD for manganese (0.02 mg/kg/day). However, when compared to actual doses seen in the literature the calculated exposure dose is too low to be of health concern. In addition, the Food and Nutrition Board of the National Research Council determined an estimated safe and adequate daily dietary intake of manganese to be 2-5 mg/day for adults (EPA 1988). Based on the highest detected concentration, daily intake from drinking water is only 1.6 mg/day for adults and 0.8 mg/day for children--well within the limit.
The exposure doses for nitrate plus nitrite (0.54 mg/kg/day for adults and 1.89 mg/kg/day for children) were above EPA's chronic RfD for nitrite (0.1 mg/kg/day) and for nitrate (1.6 mg/kg/day). In addition, the chemical concentration detected in Well 3-7 (12,600 ppb) was higher than the maximum contaminant level (MCL: 10,000 ppb) set by EPA. Because of the elevated nitrate plus nitrite levels detected in the water from Well 3-7, a potential public health hazard may exist if residents drink water from this well. Puerto Rico Department of Health has issued an advisory for Well 3-7 and informed residents not to drink water from this well.
The calculated exposure doses for the essential nutrients that were detected in the groundwater wells--iron (6.5 mg/day for adults and 3.2 mg/day for children) and sodium (687 mg/day for adults and 344 mg/day for children)--were below the Daily Values recommended by FDA (iron: 18 mg/day and sodium: 2,400 mg/day). The additional iron that would be received by drinking water from the Sun Bay wells is not harmful. The additional sodium could be of a health concern for those individuals with sodium-restricted diets. Determining whether the additional sodium intake will adversely affect a person's health is an individual assessment based on that person's diet and health status.
In order to determine if the limits of detection for explosives were protective of public health, ATSDR calculated exposure doses using the limits of detection as the maximum concentration in the formula described above. All of the calculated doses were at levels too low to be of health concern (i.e., below their respective MRLs and RfDs) for both noncancerous and cancerous health effects.
Of the chemicals detected in groundwater wells, only chloroform and di(2-ethylhexyl)phthalate are known carcinogens. Using conservative exposure assumptions, ATSDR found that the levels of these chemicals do not pose a risk for excess cancer cases in the Vieques community. ATSDR conservatively assumed that people were exposed to the maximum detected concentration on a daily basis over a lifetime exposure, even though samples collected at other times contained lower levels. ATSDR does not expect any increase in cancer risk by drinking water from groundwater wells.
Historical Drinking Water Samples:
All of the calculated exposure doses for chemicals (with the exception of nitrate plus nitrite) detected in historical drinking water samples were well below their corresponding RfDs or MRLs. The exposure doses for nitrate plus nitrite (0.21 mg/kg/day for adults and 0.77 mg/kg/day for children) were above EPA's chronic RfD for nitrite (0.1 mg/kg/day), but below the RfD for nitrate (1.6 mg/kg/day). There is not an MRL or RfD for nitrate plus nitrite. Because the sample was analyzed for nitrates and nitrites together, it is impossible to determine how much of the sample is actually nitrate and how much is nitrite. However, it is highly unlikely that the entire sample is nitrite. In addition, the actual detected concentration (5,100 ppb) was almost half of EPA's MCL (10,000 ppb) for nitrate plus nitrite. For these reasons, ATSDR determined that exposure to the chemicals detected in the historical drinking water samples did not pose a health hazard to the residents of Vieques.
Of the chemicals detected in historical drinking water samples, only cyclotrimethylene trinitramine (RDX) and dinitrotoluene are carcinogenic. Using conservative exposure assumptions, ATSDR found that the levels of RDX and dinitrotoluenes assumed to be in the drinking water samples did not pose a risk for excess cancer cases in the Vieques community. ATSDR conservatively assumed that people were exposed to the maximum detected concentration on a daily basis over a lifetime exposure, even though current samples did not detect RDX or dinitrotoluenes. ATSDR does not expect any increase in cancer risk for people who drank water from the locations where the historical sample were taken.
The Navy reported very low levels of cyclotrimethylene trinitramine (RDX) and methyl-2,4,6-trinitrophenylnitramine (tetryl) in water samples from Vieques in 1978 (Lai 1978, Hoffsommer and Glover 1978). ATSDR reviewed that data, as well as the sampling and analytical procedures, to evaluate whether those reported detections posed a potential health hazard.
ATSDR concludes that even though there is uncertainty about the source of the water sampled, RDX and tetryl may have been detected in very low concentrations in areas outside the LIA. These chemicals were at levels below health concern and did not pose a health hazard to residents who may have ingested these chemicals in drinking water. It should also be noted that, given the uncertainties stated by the laboratory that analyzed the samples, the interpretation that these chemicals were present in the water source at the reported levels is a conservative interpretation used to be protective of human health; it should not be interpreted as validation of the laboratory study's results.
Historical Drinking Water Supplies:
There were various potential sources of drinking water for residents of Vieques in 1978. The pipeline from the main island of Puerto Rico began operation in 1977, supplying public drinking water by 1978. Drinking water wells in the Esperanza aquifer that had previously been the supply of public drinking water were not closed until some time in 1978. Additionally, rainfall collection systems were still used by individuals. Although water from these collection systems did not enter the public water supply system, storage tanks at homes or at businesses may have been filled by either public water or rainfall as needed.
In 1978, the Naval Surface Weapons Center obtained and analyzed water samples inside and outside the LIA on Vieques at the request of the Chief of Naval Operations. The samples were collected one week after a military exercise in which live ordinance was used at the LIA. Fifteen water samples were taken within the LIA and 11 water samples were taken outside the impact area. Only four of these samples represent drinking water. Fourteen samples were taken of seawater and water in lagoons around the island. Eight samples were taken from bomb craters or runoff from craters (Lai 1978, Hoffsommer and Glover 1978). This discussion focuses on the drinking water samples.
Although the location of each sample is noted in the Navy report, the source of the water sampled is not documented. As previously discussed, drinking water on the island may have been piped in from Puerto Rico, collected as rainfall, pumped from the ground, or a combination of these sources. Two of the drinking water samples were taken from public water storage tanks (storing water piped in from the main island of Puerto Rico)--one sample each from Esperanza and Isabel Segunda (Lai 1978, Hoffsommer and Glover 1978). However, the water sample from Isabel Segunda was reported to be "diluted with rainfall" (Lai 1978). Although this note is not explained further, it is possible that the Isabel Segunda sample was taken from a storage tank that received both public water and rainwater from a rainfall catchment system. Note that an environmental consultant hired by the Government of Puerto Rico reported that air could be pulled into the public water storage tanks through the air vents (EPA 1999a). A third sample, from the pump house in the NASD area, is also believed to be drinking water. The source water for this sample was not noted, but since it is a pump house, the source may be a groundwater well in the Resolution aquifer (possibly Navy Well 17). The fourth drinking water sample is listed as site "OP-1", drinking water from Cerro Matias, but no source is given. OP-1 is the observation tower and the closest drinking water sample to the LIA. This sample may include rainfall collection or possibly water trucked in from Camp Garcia; there is no groundwater well near the observation tower.
The samples were tested for explosives (2,4,6-trinitrotoluene (TNT), RDX, and tetryl) [Hoffsommer and Glover 1978] and for explosion combustion products (i.e., compounds that are formed after bombs detonate: ammonia, cyanide, nitrate plus nitrite, perchlorate, and phosphorous) [Lai 1978]. Sample OP-1 was not tested for explosion combustion products.
The Navy laboratory that analyzed the samples had developed very sensitive techniques for detecting explosive compounds in order to test for explosives in seawater (Hoffsommer and Rosen 1972). These methods were more sensitive than the current EPA laboratory methods that are now considered the standard for environmental work. The detection limits are reported by the laboratory that performs the analysis and may change slightly with each analysis. Although the Navy laboratory reported very low detection limits, the authors note that "a completely positive identification was not possible due to the extremely low concentrations found" (Hoffsommer and Glover 1978). They further note "if these explosives are present, the concentrations do not exceed the values reported here."
Compounds that might interfere with the analysis are those that might leach from plastic or rubber materials (Hoffsommer and Rosen 1972). Two of the non-drinking water samples contained interfering peaks. They were re-analyzed with a slightly different method to compensate for the interference (Hoffsommer and Glover 1978). Lai notes that samples used in testing for explosion combustion products were collected with a polyethylene bottle. It is unknown if this collection method was also used for samples collected for explosives analysis. However, it is believed that both sets of samples were collected together by the same personnel.
Despite some of the uncertainties in the source of water sampled (and therefore its representativeness for exposures from drinking water), the potential health effects of the detected chemicals are evaluated here as if they were representative of a drinking water source on the island. It should also be noted that, given the uncertainties stated by the laboratory that analyzed the samples, the interpretation that these chemicals were present in the water source at the reported levels is a conservative interpretation used to be protective of human health; it should not be interpreted as validation of the laboratory study's results.
TNT was not detected in any of the drinking water samples (Table E-1). However, it is unclear from the report if TNT degradation products, specifically 4-amino-2,6-dinitrotoluene (4-A-DNT) and 2-amino-4,6-dinitrotoluene (2-A-DNT) were detected in any of the drinking water samples (Hoffsommer and Glover 1978). The authors give a detection range of 0.1 to 0.01 ppb of 2-A-DNT in all samples where the chemical was present but do not indicate which samples contained the 2-A-DNT. Since the authors are discussing all samples, including water samples from the LIA and adjacent seawater samples, it is unknown if any drinking water samples contained the 2-A-DNT. 4-A-DNT was not measured directly, but was considered by Hoffsommer and Glover (1978) to be present at the same levels as 2-A-DNT, where present.
The water sample from OP-1, the sample location closest to the LIA, did not contain measurable amounts of explosive products. However, drinking water from Esperanza was reported to have RDX (0.04 ppb) and drinking water from Isabel Segunda was reported to have both RDX and Tetryl (0.04 ppb and 0.5 ppb, respectively). The water from the Navy pump house in the magazine area on the west end of the island contained 0.06 ppb RDX (Hoffsommer and Glover 1978) [Table 6]. It should be noted that RDX was not distinguishable from 4-A-DNT in this study, so positive identification of this chemical was not possible. However, since the authors were aware of this fact and reported these results as RDX, it was evaluated as such.
Evaluation of the Impact of Water Quality on Public Health:
The concentrations of the explosive compounds (RDX and tetryl) that were detected in drinking water are not at levels of health concern. Daily intake rates that were calculated based on drinking 3 liters of water a day (1.5 liters for a 10 kg child) show doses at least 3 orders of magnitude below a level of health concern (0.003 mg/kg/day for RDX and 0.01 mg/kg/day for tetryl) for noncarcinogenic effects. Similarly, the potential for the TNT breakdown products, 4-A-DNT and 2-A-DNT, would not pose a hazard, even with calculating doses on the assumption that both compounds are present at the maximum detected value--in water from the LIA. A lifetime exposure to these levels in drinking water does not pose a cancer risk for RDX and the dinitrotoluenes, compounds which are possible human carcinogens. The carcinogenic potential of tetryl cannot be assessed because of lack of experimental data. Please refer to Appendix D for further details concerning how ATSDR estimated exposure doses and determined health effects.
The level of ammonia and nitrate plus nitrite detected is similar to what was found in groundwater sources previously discussed. Use of this water, even over a lifetime, does not pose health hazards from exposure to these chemicals.
|Chemical||Chemical Concentration (ppb)||Drinking Water Standards (ppb)|
|Explosion Combustion Products|
|Nitrate plus nitrite||5,100||4,900||240||NS||10,000†|
Reference: Hoffsommer and Glover 1978; Lai 1978
MCL = Maximum Contaminant Level (EPA)
NA = Not Available
ND = Not Detected
ppb = parts per billion