EPA Response to BP Spill in the Gulf of Mexico
Human Health Benchmarks for Chemicals in Water
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EPA, in coordination with the US Department of Health and Human Services, has developed benchmarks to assess potential human health risks from exposure to oil-contaminated water. These human health benchmarks are listed below.
To date, no chemicals have exceeded human health benchmarks. However, people should heed warnings from their local health officials regarding oil-impacted beaches and water. As an added safety precaution, if people see or smell oil in the water or beach area, they should avoid the oil-impacted area.
Human Health Benchmark Values by Chemical
Human health benchmarks are based on potential cancer and non-cancer risks associated with exposure to oil-contaminated water in the Gulf. Where applicable, the benchmarks account for both skin contact and incidental ingestion of water by a child swimmer, assuming 90 hours of exposure. These benchmarks were developed by EPA in coordination with the US Department of Health and Human Services.
Human Health Benchmark
Volatile Organic Compounds, µg/L
|Ethylbenzene||100-41-4||610||C||1, 2, 3|
Semivolatile Organic Compounds, µg/L
Polyaromatic Hydrocarbons (PAHs) µg/L
*total xylene based on the most toxic of the xylenes (m-xylene)
C - Concentration for generally acceptable cancer risk level
Questions and Answers about Human Health Benchmarks
- General information about benchmarks
- Human Health Benchmarks
- How are the human health benchmarks developed?
- Why did EPA use the exposure scenario of the child swimmer to develop the human health benchmarks?
- Do these benchmarks consider health effects of chemicals that are found in crude oil?
- What does it mean if a contaminant exceeds a human health benchmark?
- If a human health benchmark has NOT been exceeded, does that mean it is safe for me and my child to swim in the waters of the Gulf Coast that have been affected by the oil spill?
- Why is EPA sampling and monitoring the water?
- How are the human health benchmarks developed?
General information about benchmarks:
What are benchmarks?
A benchmark is a chemical concentration, specific to either water or sediment, above which there is the possibility of harm or risk to the humans or animals in the environment. Benchmarks are designed to provide risk assessors with an efficient tool to identify contaminants of concern when evaluating data. EPA is providing benchmark values on the website to aid in the assessment of potential risk to fish and other aquatic life that may come into contact with oil spill associated chemicals in the water column or sediment. These are not reflective of direct contact with oil. Benchmark values are also available for human health. Benchmarks are meant to be used for screening purposes only; they are not regulatory standards, site-specific cleanup levels, or remediation goals. These screening benchmarks are presented with the EPA data to help the public understand the condition of the environment as it relates to the oil spill.
What does EPA do with the chemical information from its sediment and water samples?
EPA has approximately 280 sampling stations in the Gulf waters near Louisiana, Mississippi, Alabama and Florida. Samples are collected periodically from the water column and sediments. Analysis of samples takes 7 to 10 days. Once water and sediment samples are analyzed in a lab, the results of the chemical analyses are sent to EPA. EPA compares the data received to various numbers, called benchmarks, that have been developed for each chemical. If the concentration of a chemical is less than its benchmark value, this suggests that it poses little risk to aquatic life or human health. Likewise, a chemical concentration that is greater than its benchmark value suggests that there is potential risk to aquatic life or human health. If a human health benchmark has been exceeded for a contaminant, it means that you should contact your state health agencies for additional information. State health agencies will provide information on what steps members of the public should take if they are exposed to these contaminants during activities on or around the coast. However, it is noteworthy that a benchmark assumes 90 hours of exposure to a chemical in question, so a single exposure is unlikely to result in significant risk.
Do all contaminants found in crude oil have ambient water quality criteria or standards?
There are chemicals related to the BP oil spill for which EPA does not have readily available ambient water quality 304(a) criteria or other established criteria or guidelines. Therefore, toxicity study data and scientific information regarding the toxicity of these chemicals are being used to develop these screening benchmarks. Given the urgency of the BP spill, all available data are used but may not encompass all data necessary for establishing Ambient Water Quality Criteria and/or Standards. Methods for developing sediment benchmarks include use of "Effects Range Low or Median" (ERL or ERM), as well as equilibrium partitioning and narcosis theory.
Human Health Benchmarks
How are the human health benchmarks developed?
Human health benchmarks are based on potential cancer and non-cancer risks associated with exposure to oil-contaminated water in the Gulf. They are based on a number of conservative assumptions about who is exposed to the chemicals and for how long. Specifically, these values are based on a 15-kg child with a body surface area of 6600 cm2, swimming 1 hour a day for 90 days, and incidentally swallowing 50 milliliters of water while swimming. The exposure assumptions used in our calculations are from two of EPA’s Exposure Factors Handbooks ( 1, 2) or are more specific to Gulf Coast living (e.g., 90 days per year Exposure Frequency). The contaminant benchmarks account for both skin contact and incidental swallowing of water by a child swimmer. However, for those contaminants which are not readily absorbed through the skin, the benchmarks are based solely on incidental swallowing. Oral exposures are quantified using Risk Assessment Guidance for Superfund (RAGS), Volume I, Part A ( 3) and dermal exposures are quantified using RAGS Volume I, Part E ( 4).
- U.S. EPA. Exposure Factors Handbook (Final Report) 1997. U.S. Environmental Protection Agency, Washington, DC, EPA/600/P-95/002F a-c, 1997. cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=12464
- U.S. EPA. Child-Specific Exposure Factors Handbook (Final Report) 2008. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/096F, 2008. cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=199243
- U.S. EPA, Risk Assessment Guidance for Superfund Volume I, Part A, 1989, EPA/540/1-89/002 www.epa.gov/oswer/riskassessment/ragsa/
- U.S. EPA, Risk Assessment Guidance for Superfund, Volume 1, Part E, 2004, EPA/540/R/99/005 www.epa.gov/oswer/riskassessment/ragse/
Why did EPA use the exposure scenario of the child swimmer to develop the human health benchmarks?
The selection of a child swimmer scenario is a conservative approach and helps to ensure that the human health benchmarks are protective of the population as a whole as well as the most sensitive populations that may potentially be exposed. Children may be more sensitive to chemicals than adults. This is due to the fact that children absorb more of the chemical, relative to body weight, than adults and have developing organ systems that are more vulnerable and less able to detoxify chemicals.
Do these benchmarks consider health effects of chemicals that are found in crude oil?
The human health benchmarks were developed for compounds that are commonly found in crude oil. The benchmarks represent water concentrations of individual chemicals that, if not exceeded, are considered acceptable for the exposure situation presented. These values were derived using toxicity information from studies of the individual chemicals. Toxicity information for the complex and varied mixture of chemicals that are found in crude oil is not available. These values represent health-protective concentrations in the sense that safety factors were incorporated in their derivation, and a high end exposure scenario was considered. There is uncertainty regarding the level of protectiveness if a substance is present at the benchmark concentration in combination with a complex mixture of chemicals in crude oil.
What does it mean if a contaminant exceeds a human health benchmark?
If a benchmark has been exceeded for a contaminant, it means that you should contact your state health agencies for additional information. State health agencies will provide information on what steps members of the public should take if they are exposed to these contaminants during activities on or around the coast. However, it is noteworthy that a benchmark assumes 90 hours of exposure to a chemical in question, so a single exposure is unlikely to result in significant risk.
Here are some simple steps you can take to protect yourself from contaminated water along the Gulf Coast:
- Pay attention to local authorities and avoid areas affected by the oil spill. The oil could cause health problems, including skin and eye irritation or breathing problems.
- Keep your pets from entering oil-contaminated areas.
- If you get contaminated water on your skin, wash it off immediately with soap and water or a hand cleanser meant to remove oils and grease.
- If you accidentally drink some oil-contaminated seawater and symptoms such as nausea, vomiting or dizziness occur, seek medical attention.
If a human health benchmark has NOT been exceeded, does that mean I can swim with my child in Gulf Coast waters?
Even when a human health benchmark has not been exceeded, residents and tourists should refer to state and local information for beach conditions in their area. EPA sampling data is only one tool for examining water quality conditions. In addition, it takes several days from the point of collection to analyze and post the data on the website, so data posted may not reflect real-time conditions. If the water smells like gasoline or there are visible signs of oil contamination, swimming or contact with the water is not recommended.
Why is EPA sampling and monitoring the water?
EPA is tracking the prevalence of potentially harmful chemicals in the water as a result of the BP spill to determine the level of risk posed to aquatic life and human health. Monitoring information allows EPA to estimate the amount of these compounds that may reach ecological systems. When combined with available information on the toxicity of these compounds, scientists can estimate the likely magnitude of effects on aquatic life and human health.