PUBLIC HEALTH ASSESSMENT
IMPERIAL REFINING COMPANY
ARDMORE, CARTER COUNTY, OKLAHOMA
Imperial Refining Company was proposed for the National Priorities List (NPL) on May 11, 2000and listed on July 27, 2000. The Agency for Toxic Substances and Disease Registry (ATSDR) isrequired by Congress to conduct public health assessments on all sites proposed for the NPL. In thispublic health assessment, ATSDR evaluates the public health significance of the Imperial RefiningCompany site. ATSDR has reviewed available environmental data, potential exposure scenarios,and community health concerns to determine whether adverse health effects are possible. In addition,this public health assessment recommends actions to prevent, reduce, or further identify thepossibility for site-related adverse health effects.
This site description comes in part from the Removal Assessment Report (May 1999) and the SiteInspection Narrative Report (July 1998) [1,2]. The Imperial Refining Company (IRC) site (the site)is located just northeast of Ardmore, in Carter County, Oklahoma. It covers approximately 80 acreson either side of Highway 142 about 50 yards north of the overpass crossing the Burlington,Northern, and Santa Fe railroad tracks. The legal description of the property is the SE1/4 of theNE1/4 of Section 20, and the SW1/4 of the NW1/4 of Section 21, Township 4 South, Range 2 East,Carter County, Oklahoma. Initial site investigations only covered about 55 acres of the property,located northwest of the railroad tracks. The determination of exact site size has not been finalized.
The site is well vegetated with trees and moderate underbrush, except in several impacted areaswhich are covered with asphalt- or tar-like wastes. At least one waste area also contains severalabandoned, partially crushed 55-gallon drums. The drums are rusty and appear to be empty. Anintermittent stream and several wetlands areas are found on the site. Ponds on the site could havebeen highway fill "borrow pits" or reservoirs during operation of the refinery. The site is bounded byundeveloped property to the south and east. Several small businesses, an active refinery, and a smallresidential area with about a dozen houses are located north of the site, and west of the property areseveral treatment lagoons for waste water from the active refinery. Directly south of the west side ofthe site is a closed City of Ardmore landfill dating from the early 1970s. Access to the site isunrestricted.
Imperial Refining Company was a crude oil refinery which operated on the site from 1917 to 1934,when it declared bankruptcy. All tanks and storage equipment were dismantled by 1948. The tankbottom materials were apparently dumped out onto the site soils during the dismantling. Althoughthe property has changed ownership several times since the tanks and storage equipment weredismantled, there is no clear evidence of further operations occurring on the site.
Ardmore has between 26,000 and 28,000 people. Figure 1 shows demographic information for thepopulation of the area surrounding the site. About 2,250 people live within a 1-mile radius of thesite. The population is mostly Caucasian (70%), African-American (14%), and American Indian(13%). According to the site assessment report, approximately 130 workers and residents are within200 feet of contaminated areas .
The land surrounding the site is mostly rural or industrial. There is a small residential area of abouta dozen houses approximately 200 to 300 yards north of the site. During a visit to the site area,evidence of hunting (a deer blind and tree stand) was observed just north of the site. Members of thepublic interviewed during a public availability session confirmed that hunting is common on the site.They also indicated that people fish in the ponds on the site, especially during the summer, and thatchildren 10 years of age and older play on the site.
Farm animals, including cows and horses, were observed in the fields near the site. Various types ofwildlife live on or near the site, including the Texas Horned Lizard and the Alligator SnappingTurtle, which are sensitive species .
The intermittent stream that runs through the north side of the site joins Sand Creek, which flowstowards the northeast for approximately 4 miles until it joins Caddo Creek . The active refinerynorth of the site and the city of Ardmore use these downstream creeks for wastewater discharge(1).
No domestic groundwater wells are located within a 1-mile radius of the site . According to stateofficials, Ardmore's municipal water system supplies drinking water to people living in the residential area north of the site.
Two sets of data have been collected to characterize the site. On May 20, 1998, Oklahoma Department of Environmental Quality (DEQ) sampled waste sources (surface samples analyzed were from 0 to 6 inches in depth), surface water, and sediment (0 to 6 inches in depth) on the site as part of the site inspection . On February 23 and 24, 1999, contractors for the Region 6 Superfund Technical Assessment and Response Team (START) collected waste source samples at the site as part of a removal assessment .
The data collected were part of the initial characterization of the wastes and highly impacted areas ofthe site. While these data give useful information about site contaminants, the data do not fullydescribe all the exposure pathways of potential concern. The conclusions reached in this documentare based on the data available at the time and may be modified based on the results of additionalsamples that will be collected during the remedial investigation process.
The process by which ATSDR evaluates the possible health impact of contaminants is summarizedhere and described in more detail in Appendix A. ATSDR uses comparison values (CVs) todetermine which chemicals to examine more closely. CVs are concentrations of chemicals in theenvironment (air, water, or soil) below which no adverse human health effects should occur.Exceeding a CV does not mean that health effects will occur, just that more evaluation is needed.
If the level of contamination at the site is greater than the CV, further evaluation will focus onidentifying which chemicals and exposure situations could be a health hazard. Child and adultexposure doses are calculated for the exposure scenario of interest. Exposure doses are the estimatedamounts of a contaminant that people come in contact with under specified exposure situations.These exposure doses are compared to appropriate health guidelines for that chemical. Healthguideline values are considered safe doses; that is, health effects are unlikely below this level. If theexposure dose for a chemical is greater than the health guideline, then the exposure dose is comparedto known health effect levels identified in ATSDR's Toxicological Profiles. If the chemical ofconcern is a carcinogen, the cancer risk is also estimated. These comparisons are the basis for statingwhether the exposure is a health hazard.
The following sections describe the various ways people could come into contact with contaminantsat the site. Each of these is called an exposure pathway. Appendix B summarizes the possibleexposure pathways. If people are unlikely to be exposed to contaminants in a given pathway, thenthat pathway will not be evaluated further for human health risks.
Several impacted areas on the site are covered with black, asphalt- or tar-like waste material; thesewill be referred to as source areas. People trespassing on the site could come into direct contact withthese contaminants. They could get particles of the material on their skin, or they might accidentallyeat or breathe in the particles.
To be conservative, our initial screening assumed that people will contact the source areas as much as they would the soil. Table 1 lists the contaminants that were found in the wastes on-site at levels above soil CVs.
|Contaminant2,3,4||Range Detected in Waste in ppm5||Samples > DL6 / Total||CV7 in ppm||CV Source8|
2.1 - 17
|6 / 11||20 / 0.59||EMEG10 / CREG11|
10.5 - 721
|11 / 11||400||SSL12|
46 - 430
|5 / 11||none13|
| PAHs: |
143 - 232
|4 / 12||0.9||SSL|
145 - 570
|3 / 12||0.9 / 0.114||SSL / CREG|
248 - 717
|5 / 12||88||SSL|
168 - 932
|5 / 12||none13|
|1 Data Sources: Removal Assessment , Site Inspection .|
|2 Antimony, beryllium, thallium, 1,1-dichloroethene, vinyl chloride, benzo(k)fluoranthene,dibenz(ah)anthracene, and indeno(123cd)pyrene were not detected. However, some or all of theanalysis detection limits for these compounds were higher than the CV.|
|3 4-methyl-2-pentanone, acenaphthylene, and benzo(ghi)perylene were not detected. No CVs areavailable for these compounds.|
|4 Naphthalene and pyrene were not detected at levels above the CV. However, some of the analysisdetection limits were higher than the CV.|
|5 ppm = parts per million of chemical in waste. ppm = mg (milligram) per kg (kilogram) of waste.|
|6 DL = detection limit.|
|7 CV = comparison value.|
|8 These comparison values are described in Appendix 1.|
|9 The first number is the EMEG and the second is the CREG.|
|10 EMEG = environmental media evaluation guide.|
|11 CREG = cancer risk evaluation guide.|
|12 SSL = EPA soil screening level.|
|13 No CV available.|
|14 The first number is the SSL and the second is the CREG.|
Next, exposure doses were calculated for the contaminants of concern in Table 1. The worst casewas assumed to be a 10-year-old (36.3 kg average ) contacting the maximum concentration ofeach contaminant all day for 52 days out of the year (once a week). The exposure dose estimatedthrough this procedure was compared with health guideline values and toxicological information forthe contaminant of concern. For evaluating the risk of cancer, we assumed adults weighing 70 kgwould be exposed to the maximum concentration of each contaminant for 52 days a year for alifetime (70 years). The following sections describe this evaluation for the contaminants of concern from Table 1.
No health effects are expected from current exposure to the arsenic detected in the waste piles on thesite. The estimated exposure dose for arsenic was found to be 30 times smaller than the chronic oralminimal risk level (MRL) for arsenic . The MRL, an ATSDR health guideline value, is a dose ofa chemical that is unlikely to cause an adverse, noncancerous health effect.
Arsenic causes cancer, based on human studies . However, based on the low levels of arsenic inthe source areas and the low exposure doses, the chance of an increased risk of cancer from thisexposure is negligible.
Exposure to lead in the source areas on this site is unlikely to result in health effects. This is basedon the maximum levels of lead detected and the assumption that older children only occasionallyplay or trespass on the site. If young children (less than 6 years old) had daily contact with the wastepiles, the lead could pose a health hazard. However, it is unlikely that a small child would beplaying on the waste piles long enough to ingest appreciable amounts of dirt. Older children (andadults) are less vulnerable to lead in the soil than small children because they generally ingest lesssoil and less lead is absorbed into their bodies .
In general, the level of lead in a person's blood, typically measured in micrograms per deciliter (µg/dL), gives a good indication of recent exposure to lead and also correlates well with health effects. If we use the most protective correlation between blood lead levels and soil concentration found in epidemiological studies (0.0068 µg/dL increase in blood lead level per parts per million [ppm] of lead in soil) and the maximum lead concentration measured in soil, then persons exposed to this soil could increase their blood lead levels by 4.9 µg/dL . The Centers for Disease Control and Prevention (CDC) considers children to have elevated lead levels if the amount of lead in the blood is 10 µg/dL or above. However, some studies have indicated that levels of 10 µg/dL and less in children's blood may be associated with small decreases in IQ and slightly impaired hearing and growth. Any increase in blood lead level from exposure to the site is likely to be much smaller than the 4.9 µg/dL value. This is because the exposure to the whole site is infrequent, a child probably would not play exclusively on the waste piles, and the maximum concentration of lead was used to make our estimate.
Animal data indicate that lead is a probable human carcinogen . However, the animal studieswere based on very high doses of lead and are difficult to compare to low level environmentalexposures, such as at those present at the site. Because no cancer slope factor for lead exists, it isimpossible to quantitatively evaluate carcinogenic risk.
The estimated exposure dose for 2-methylnaphthalene was found to be more than 200 times lowerthan the chronic oral MRL for 1-methylnaphthalene, a compound expected to behave like 2-methylnaphthalene . No health effects are expected from this exposure.
Polycyclic Aromatic Hydrocarbons (PAHs)
The remaining contaminants from Table 1 are polycyclic aromatic hydrocarbons (PAHs). Theseindividual PAHs often occur together in the environment, and many have similar toxicologicaleffects and environmental fate . PAHs are a group of chemicals that are formed during theincomplete burning of coal, oil, wood, or other organic substances, such as tobacco or charbroiledmeat. They can also be found in crude oil and creosote. Low levels of PAHs are found throughoutthe environment in the air, water, and soil.
At the site, adults or children coming into contact with the waste piles may get additional PAHs intotheir bodies by accidentally eating the soil (oral exposure) or by getting the contaminated soil ontheir skin (dermal exposure). Breathing in PAH-contaminated dust from the site does not appear tobe a significant source of exposure at this point, since the tar-like waste in the source areas is notcrumbling into small particles.
For noncancer health effects, the exposure doses were calculated from the maximum levels of PAHs(listed in Table 1). These estimated oral exposure doses for this site are over 1,000 times smallerthan effect levels seen in animal experiments on various PAHs. Therefore, no noncancer healtheffects are expected from ingestion of PAHs from the source areas, assuming the current infrequentuse of the site. In studies of dermal exposure to high concentrations of PAHs, skin irritation andother disorders have occurred. Since exposure to the waste source is infrequent at present and thePAHs in the soil are less likely to be absorbed into the skin compared the methods used inexperimental studies, no adverse health effects are expected from dermal exposure to PAHs from thesource areas.
Evidence shows that some PAHs may cause cancer in humans. This evidence comes primarily fromoccupational studies of workers who were exposed to mixtures of PAHs as a result of theirinvolvement in such processes as coke production, roofing, oil refining, or coal gasification. Theassociated cancer occurred predominately in the lungs, following inhalation exposure, and in theskin, following dermal exposure. Certain PAHs also cause cancer in animals.
In order to estimate the increased risk of cancer from this group of PAHs, a relative potencyapproach has been developed for carcinogenic PAHs based on benzo(a)pyrene, the most studiedPAH compound . Using the maximum concentration of PAHs found at the site and assumingweekly contact with the contaminated source areas over many years results in an estimated low tomoderate increase in the risk of cancer. This is likely an overestimate of the current cancer riskbecause of the conservative (i.e., protective) exposure assumptions used. People would not beexpected to frequently contact the maximum concentration every time they are on the site, nor wouldthey be likely to keep the tar-like substance on their skin for prolonged periods. When moresampling data are available for the site, we can make a better estimate of the average concentrationof PAHs that a person may contact in the soil and source areas.
Water from surface runoff, streams, and ponds on-site comes in contact with the waste material. Nouse of this water for drinking water purposes was identified, but people who hunt, fish, or otherwisetrespass on the site may accidentally ingest some of the surface water or get it on their skin.
Four surface water samples were collected during the site investigation. As shown in Table 2, in onesample a contaminant (chloroform) was detected above the drinking water CV. This sample wastaken from a wetland on the western central portion of the site. Estimated exposure of a 10-year oldchild (36.3 kg average ) who accidentally ingests this surface water 52 times a year (once aweek) is more than 10 times lower than the minimal risk level . Health effects are not expected tooccur due to exposure to chloroform at this level. Chloroform is a probable human carcinogen.However, the calculated increased cancer risk from exposure to the highest level of chloroform in Table 2 is negligible.
|Contaminant||Range in Water inppb2||Samples > DL3 /Total||Drinking Water|
CV4 in ppb
ND - 2300
|1 / 4||100 / 66||EMEG7 / CREG8|
|1 Data source: Site Inspection .|
|2 ppb = parts per billion of chemical in water. ppb = µg (microgram) per liter of water.|
|3 DL = detection limit.|
|4 CV = comparison value.|
|5 These comparison values are described in Appendix 1.|
|6 The first number is the EMEG and the second is the CREG.|
|7 EMEG = environmental media evaluation guide.|
|8 CREG = cancer risk evaluation guide.|
People who hunt, fish, or otherwise trespass on the site may accidentally ingest some of thesediments from the ponds or streams on the site or get them on their skin. To be conservative, ourinitial screening assumed sediments would be contacted like soil particles. Table 3 lists the eightcontaminants that were found at levels above soil CVs in the sediments on-site.
|Contaminant||Range in sediment in ppm2||Samples > DL3 / Total||CV4 in ppm||CV Source5|
ND - 23
|4 / 13||20 / 0.56||EMEG7 / CREG8|
| PAHs |
ND - 1.3
|3 / 13||0.9||SSL9|
ND - 12
|4 / 13||0.9 / 0.110||SSL / CREG|
ND - 1.1
|2 / 13||0.9||SSL|
ND - 4.9
|5 / 13||none11|
ND - 2.9
|2 / 13||none|
ND - 2.6
|5 / 13||0.9||SSL|
ND - 0.53
|1 / 13||0.09||SSL|
|1 Data source: Site Inspection .|
|2 ppm = parts per million of chemical in sediment. ppm = mg (milligram) per kg (kilogram) of sediment.|
|3 DL = detection limit.|
|4 CV = comparison value.|
|5 These comparison values are described in Appendix 1.|
|6 The first number is the EMEG and the second is the CREG.|
|7 EMEG = environmental media evaluation guide.|
|8 CREG = cancer risk evaluation guide.|
|9 SSL = EPA soil screening level.|
|10 The first number is the SSL and the second is the CREG.|
|11 No CV available.|
Next, exposure doses were calculated for the contaminants of concern in Table 3. The worst casewas assumed to be a 10-year-old contacting the maximum concentration of each contaminant forabout half a day for 52 days out of the year.
For this scenario, the exposure doses estimated for sediment are at least 10 times smaller thanexposure doses estimated for the source areas. The estimated exposure doses are well below theMRLs for arsenic and PAHs. At these concentrations, the increased risk of developing cancer is alsovery low. Therefore, no health effects are expected from exposure to the sediment.
People trespassing on the site for hunting, fishing, or other purposes could come into contact withsoil contaminated by the source areas. People could get soil particles on their skin, or they mightaccidentally eat or breathe in the soil. There are no data on contaminant levels in soil at this time;only the source areas have been sampled. It is assumed that the soil contamination is no greater thansource area contamination. However, it is possible that not all source areas have been discovered,and additional soil contamination may exist. Therefore, any potential impact to public health cannotbe determined until further investigation and/or additional sampling is conducted.
Hunting and fishing takes place on the site. Hunters, fishers, and their families may consumeanimals and fish that may have bioaccumulated contaminants from the wastes and sediments on thesite. No data on contaminant levels in fish and animals from the site have been collected. There waslittle vegetation growing directly on the source areas, and it is therefore unlikely that animals couldaccumulate appreciable amounts of contaminants through eating vegetation. Based on the sedimentdata available, it is unlikely that fish would be affected to a large degree by contaminants. However,further characterization of the site may indicate that testing of fish tissue is warranted.
The site contains physical hazards which warrant restricting access. The rusted, partially crusheddrums could have sharp edges, and areas with large quantities of broken glass were observed. Acomplete site characterization has not been performed as of the writing of this report, so othermaterials on site may also pose physical hazards.
Contaminants from the source areas could infiltrate into the groundwater beneath the site. If peopleused this groundwater for drinking, they could be exposed to contaminants. According to the SiteInspection Report , no private drinking water wells are within 1 mile of the site. Because thecurrent information indicates that no one is drinking groundwater near the site, this pathway will notbe evaluated further. If the well survey to be performed in conjunction with the remedialinvestigation shows wells have recently been installed near the site, we will evaluate this pathway atthat time.
Contaminants may volatilize from the source area, or particles may be transported as fugitive dust.People could breathe in these contaminants or get them on their skin. There are no data on aircontaminants from the site. Based on the current conditions at the site and the source area makeup, itis extremely unlikely that contaminants are being transported through this pathway. The maincontaminants in the source areas are not very volatile, and the source areas do not appear to crumbleinto small enough particles to create dust.
Due to the age of the contamination, more volatile contaminants were probably released in the past.While people could have been exposed to these contaminants, the rural nature of the area suggeststhat exposure was not great or frequent enough to significantly affect people's health.
ATSDR recognizes that infants and children may be more vulnerable to exposures than adults incommunities faced with contamination of their air, water, soil, or food. This vulnerability is a result of the following factors:
- Children are more likely to play outdoors and bring food into contaminated areas.
- Children are shorter, resulting in a greater likelihood to breathe dust, soil, and heavy vapors close to the ground.
- Children are smaller, resulting in higher doses of chemical exposure per body weight.
- The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages.
Because children depend completely on adults for risk identification and management decisions,ATSDR is committed to evaluating their special interests at the site as part of the ATSDR ChildHealth Initiative.
The major exposure route for children living near the site is ingestion of surface soil. Please refer tothe appropriate section for discussion of the possible health effects for children.
The Superfund law requires that health outcome data be considered in a public health assessment.Health outcome data may include mortality information (e.g., the number of people dying from acertain disease) or morbidity information (e.g., the number of people in an area getting a certaindisease or illness). In order to thoroughly evaluate health outcome data as it relates to a hazardouswaste site, the following elements are necessary: (1) the presence of a completed human exposurepathway, (2) sufficiently high contaminant levels to result in measurable health effects, (3) sufficientnumber of people in the completed pathway for the health effect to be measured, and (4) a healthoutcome database in which disease rates for populations of concern can be identified.
The site does not meet the requirements for including an evaluation of health outcome data in apublic health assessment. While there are completed human exposure pathways at this site, thecontaminant levels, exposures, and exposed population are not great enough to result in ameaningful measurement of health outcome data.
On January 24, 2001, ATSDR had a public availability session in Ardmore. The meeting wasattended by approximately 5 residents of Ardmore, as well as several officials from city, state, andfederal organizations. During this meeting, the community voiced only one concern regardinghuman health.
In addition to the January availability session, the Imperial Refining Company Public HealthAssessment was available for public review and comment from August 23 to September 24, 2001,at the Ardmore Public Library in Ardmore, OK. The public comment period was announced in localnewspapers, and fact sheets announcing the availability of the public health assessment were mailedto residents near the site. The PHA was also sent to several federal, state, and local officials. Nowritten comments were received, but several concerns were expressed in telephone calls to ouroffice.
The health concerns are summarized and addressed below.
Concern: About 3-4 years ago, during a summer night, a strong odor was coming from the areaof the Imperial Refining site. It smelled like rotten eggs, but did not seem to be coming from therefinery treatment ponds (located west of the Imperial Refining site). Also at this time, a weldingtorch flared up, like there was something flammable in the air. This occurred about a quartermile south of the site.
Response: Of course, at this point in time, it is very difficult to determine the true cause of the pastodor. But we do use past information like this to help us evaluate site conditions and, whenappropriate, direct future sampling efforts. Observations about the site are always appreciated.
A rotten egg smell usually indicates hydrogen sulfide in the air. Hydrogen sulfide is a colorless,flammable gas and is found naturally or may be produced from man-made processes. It is often theresult of bacteria breaking down organic matter. This could occur in sewage treatment plants or inwetlands. Since hydrogen sulfide is found in crude petroleum, refineries may also be a source of thiscompound.
Because hydrogen sulfide gas is heavier than air, it is possible that the gas collected in a low areadownwind of the source. People are very sensitive to hydrogen sulfide and can smell it at lowconcentrations (around 0.5 parts of gas per billion parts of air). At higher concentrations, it can beirritating to your eyes and throat or cause even more serious health problems. Since this situationwas out in the open, it is unlikely that any gas present could build up to very high concentrations.The citizen reporting this odor did not describe any health problems resulting from it.
A welding torch flaring up could result from a number of conditions, including something with thewelding operation itself. If an outside gas was the cause, it could be another naturally occurring gas,methane. Methane is also produced by bacteria breaking down organic material, such as in landfillsor sewage plants. When large amounts of methane are produced, it can pose an explosive hazard if itcollects in confined spaces. Methane is an odorless gas and is not otherwise considered toxic orharmful. For the situation described by the citizen, again, it is impossible for us to determine yearslater exactly what caused the flare up.
Concern: If the public health assessment said that everything was settled on the site [noimmediate health risks], why did we receive the letter in the mail?
This public health assessment was open for public comment from August 23 to September 24, 2001.ATSDR was seeking comments and health concerns to ensure that the community's concerns areconsidered in planning future activities on the site. Current site data do not indicate the potential forhealth effects in the community. However, community concerns will be especially useful in planningand evaluating data to be collected during the remedial investigation process.
Concern: My street is one block from Refinery Road and there has been a lot of cancer there.Out of 14 houses, I know of 6 cases of cancer, including breast, lung, prostate, and tumors in thepelvic and tailbone areas. No one knows why Ardmore's cancer rates are so high.
At this time, we do not have any reason to believe that the Imperial Refining Company site may becausing cancer in the Ardmore area. Currently available site data show contaminant levels andexposures are too low to result in health effects. Since the refinery discontinued operation over 65years ago, any past occupational exposures from Imperial Refinery would not significantly affectcancer rates at this point.
The best indicator of an unusual number of cancers in an area would be to look at the rate of cancersbeing diagnosed in a given population within a certain time period. This is called the cancerincidence rate. Oklahoma started compiling cancer incidence data in 1997. However, because thecancer registry program is so new, there are not enough available data at this time to evaluatewhether or not Ardmore has a high rate of cancer.
In the United States, a person has about a 1 in 3 risk of developing cancer over their lifetime. Ofcourse, the risk is smaller for the young and increases as we age. So, in any given community, itwould not be unusual to see a number of people with various types of cancer. For more informationon cancer statistics, risk factors, and prevention; contact the American Cancer Society at 1-800-ACS-2345 or at their internet site, www.cancer.org.
- Analyses of the available environmental data and the past and current limited use of the siteindicate that any past or current exposures are not likely to lead to adverse health effects.Therefore, the site is categorized as "no apparent public health hazard." However, changing exposure scenarios, such as residential development of the site or the addition of a playground, could alter this conclusion.
- The site has not been completely characterized regarding contaminant levels. EPA will becollecting more data on the site through the remedial investigation. If the new data indicates significantly higher levels of contamination than known now, the above conclusion may be changed.
- Rusted drums and broken glass on the site may pose a physical hazard, especially to children if they play on the site.
- Off-site contaminant migration has not been determined for the site. Based on the currently available on-site data, it is not expected that off-site contaminant levels would be likely to lead to health effects.
- ATSDR recommends that EPA complete its characterization of contamination at the site.This should include measuring contamination in the soil, shallow groundwater, surfacewater, and sediment. Based on the shallow groundwater findings, soil gas sampling may bewarranted. Based on the surface water and sediment findings, fish tissue sampling may bewarranted.
- Until the site is fully characterized, and to prevent injury from the physical hazards at thesite, ATSDR recommends restricting access through fencing or posting of no trespassingsigns. Proposed land uses should be reviewed for public health impact.
- If warranted by the results of the remedial investigation, ATSDR recommends that off-site migration of site contamination be characterized.
The Public Health Action Plan for the site contains a description of actions to be taken by ATSDRat the site after the completion of this public health assessment. The purpose of the Public HealthAction Plan is to ensure that this public health assessment not only identifies public health hazards,but provides a plan of action designed to mitigate and prevent adverse human health effects resultingfrom exposure to hazardous substances in the environment. Included is a commitment on the part ofATSDR to follow up on this plan to ensure its implementation. The public health action to be implemented is as follows:
- A fact sheet on the site and the findings of this public health assessment will be developed and distributed to citizens living near the site.
- Additional environmental sampling results for the site will be reviewed as needed, and the possible public health implications will be evaluated.
ATSDR will reevaluate and expand the Public Health Action Plan when needed. Newenvironmental, toxicological, or health outcome data or the results of implementing the above proposed actions may determine the need for additional actions at this site.
Authors of Report
Jill J. Dyken, Ph.D., P.E.
Environmental Health Scientist
Superfund Site Assessment Branch
Division of Health Assessment and Consultation
Barbara Cooper, M.S.P.H.
Environmental Health Scientist
Superfund Site Assessment Branch
Division of Health Assessment and Consultation
ATSDR Region 6
Community Involvement Specialist
Community Involvement Branch
Division of Health Assessment and Consultation
- Ecology and Environment. Removal assessment report for Imperial Refining Company.Prepared for the US Environmental Protection Agency, Region VI. Dallas, TX; May 1999.
- Oklahoma Department of Environmental Quality. Site inspection narrative report.Oklahoma City, OK; July 1998.
- US Environmental Protection Agency. Exposure factors handbook. Washington, DC: USEnvironmental Protection Agency. Office of Research and Development. EPA/600/C-99/001; February 1999.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for arsenic:update. Atlanta: US Department of Health and Human Services; 2000.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for lead: update. Atlanta: US Department of Health and Human Services; 1999.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for naphthalene: update. Atlanta: US Department of Health and Human Services; 1995.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for polycyclic aromatic hydrocarbons (PAHs): update. Atlanta: US Department of Health and Human Services; 1995.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for chloroform: update. Atlanta: US Department of Health and Human Services; 1997.
In evaluating these data, ATSDR used comparison values (CVs) to determine which chemicals to examine more closely. CVs are the contaminant concentrations found in a specific media (air, soil, or water) and are used to select contaminants for further evaluation. CVs incorporate assumptions of daily exposure to the chemical and a standard amount of air, water, and soil that someone may inhale or ingest each day.
As health-based thresholds, CVs are set at a concentration below which no known or anticipatedadverse human health effects are expected to occur. Different CVs are developed for cancer andnoncancer health effects. Noncancer levels are based on valid toxicologic studies for a chemical,with appropriate safety factors included, and the assumption that small children (22 pounds) andadults are exposed every day. Cancer levels are the media concentrations at which there could be aone in a million excess cancer risk for an adult eating contaminated soil or drinking contaminatedwater every day for 70 years. For chemicals for which both cancer and noncancer numbers exist, thelower level is used to be protective. Exceeding a CV does not mean that health effects will occur,just that more evaluation is needed.
CVs used in this document are listed below:
Environmental Media Evaluation Guides (EMEGs) are estimated contaminantconcentrations in a media where non-carcinogenic health effects are unlikely. The EMEG isderived from the Agency for Toxic Substances and Disease Registry's (ATSDR) minimalrisk level (MRL).
Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations thatwould be expected to cause no more than one additional excess cancer in one million personsexposed over a lifetime. CREGs are calculated from the Environmental Protection Agency's(EPA) cancer slope factors (CSFs).
EPA Soil Screening Levels (SSLs) are estimated contaminant concentrations in soil at whichadditional evaluation is needed to determine if action is required to eliminate or reduce exposure.
Evaluation of Public Health Implications
The next step is to take those contaminants that are above the CVs and further identify which chemicals and exposure situations are likely to be a health hazard. Child and adult exposure doses are calculated for the site-specific exposure scenario, using our assumptions of who goes on the site and how often they contact the site contaminants. The exposure dose is the amount of a contaminant that gets into a person's body. Following is a brief explanation of how we calculated the estimated exposure doses for the site.
Source Area Contaminant Ingestion
Exposure doses for ingestion of contaminants from the source areas were calculated using the maximum concentration measured in the source areas, in mg/kg (or ppm), multiplied by the soil ingestion rate for adults (0.0001 kg/day) or children (0.0002 kg/day). The multiplication product was divided by the average weight for an adult, 70 kg (154 pounds) or a 10-year old child, 36.3 kg (80 pounds). The resulting dose was then multiplied by a factor of 52/365, because the exposure was assumed to occur on average of once a week throughout the year.
Surface Water Ingestion
Exposure doses for surface water ingestion were calculated using the maximum concentration for a surface water contaminant, in milligrams per liter (mg/L), multiplied by an incidental surface water ingestion rate of 0.02 liter/day for adults or 0.01 liter/day for children. These ingestion rates are 1/100th of the EPA default drinking water rates. The multiplication product was divided by the average weight for an adult, 70 kg (154 pounds), or for a 10-year old child, 36.3 kg (80 pounds). The resulting dose was then multiplied by a factor of 52/365, because the exposure was assumed to occur on average once a week throughout the year.
Exposure doses for ingestion of contaminants from the sediment were calculated using the maximum concentration measured in the sediment, in mg/kg (or ppm), multiplied by 1/10th of the soil ingestion rate, 0.00001 kg/day for adults or 0.00002 kg/day for children. The multiplication product was divided by the average weight for an adult, 70 kg (154 pounds) or a 10-year-old child, 36.3 kg (80 pounds). The resulting dose was then multiplied by a factor of 52/365, because the exposure was assumed to occur on average once a week throughout the year.
Dermal (Skin) Exposure
Dermal absorption depends on numerous factors including the area of exposed skin, anatomical location of exposed skin, length of contact, concentration of chemical on skin, chemical-specific permeability, soil adherence, medium in which the chemical is applied, and skin condition and integrity. Because chemicals differ greatly in their potential to be absorbed through the skin, each chemical needs to be evaluated separately and is discussed as needed in the main body of the public health assessment. The assumed exposure frequency and duration for contact with the soil, sediment, and surface water is the same as used above for the ingestion route. The skin surface area and soil-to-skin adherence factors used in this public health assessment were taken from EPA's Exposure Factor Handbook(2). Absorption factors and other chemical-specific factors were taken from the ATSDR toxicological profile for that chemical.
The calculated exposure doses are then compared to an appropriate health guideline for that chemical. Health guideline values are considered safe doses; that is, health effects are unlikely below this level. The health guideline value is based on valid toxicologic studies for a chemical, with appropriate safety factors built-in to account for human variation, animal-to-human differences, and/or the use of the lowest adverse effect level. For noncancer health effects, the following health guideline values are used.
Minimal Risk Level (MRLs) - developed by ATSDR
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. A list of MRLs can be found at http://www.atsdr.cdc.gov/mrls.html.
Reference Dose (RfD) - developed by EPA
An estimate, with safety factors built in, of the daily, life-time exposure of human populations to a possible hazard that is not likely to cause noncancerous health effects. The RfDs can be found at http://www.epa.gov/iris/.
If the estimated exposure dose for a chemical is less than the health guideline value, then the exposure is unlikely to cause a non-carcinogenic health affect in that specific situation. If the exposure dose for a chemical is greater than the health guideline, then the exposure dose is compared to known toxicological values for that chemical and is discussed in more detail in the public health assessment (see Discussion Section). These toxicological values are doses derived from human and animal studies which are summarized in the ATSDR Toxicological Profiles. A direct comparison of site-specific exposure and doses to study-derived exposures and doses found to cause adverse health effects is the basis for deciding whether health effects are likely or not.
The estimated risk of developing cancer from exposure to the contaminants was calculated by multiplying the site-specific adult exposure dose by EPA's corresponding Cancer Slope Factor (which can be found at http://www.epa.gov/iris/). The results estimate the maximum increase in risk of developing cancer after 70 years of exposure to the contaminant.
The actual risk of cancer is probably lower than the calculated number. The method used to calculate EPA's Cancer Slope Factor assumes that high-dose animal data can be used to estimate the risk for low dose exposures in humans. The method also assumes that there is no safe level for exposure. Little experimental evidence exists to confirm or refute those two assumptions. Lastly, the method computes the 95% upper bound for the risk, rather than the average risk, suggesting that the cancer risk is actually lower, perhaps by several orders of magnitude.(3)
Because of uncertainties involved in estimating carcinogenic risk, ATSDR employs a weight-of-evidence approach in evaluating all relevant data(4). Therefore, the carcinogenic risk is described inwords (qualitatively) rather than giving a numerical risk estimate only. The numerical risk estimatemust be considered in the context of the variables and assumptions involved in their derivation andin the broader context of biomedical opinion, host factors, and actual exposure conditions. Theactual parameters of environmental exposures must be given careful consideration in evaluating the assumptions and variables relating to both toxicity and exposure.
|Source for All Pathways: Bottoms Material from Defunct Refinery Tanks|
|Pathway Name||EnvironmentalMedia & TransportMechanisms||Point ofExposure||Route of Exposure||Exposed Population||Time||Notes||Complete?|
|Waste Sources||Waste depositedthroughout site||Waste sources onsite||Incidental ingestion,inhalation, dermalexposure||Hunters, fishers,trespassing children andadults||Past, present,future||Population may includechildren 10 years andolder||Y|
|Surface water||Surface water runoff overwastes to creek andwetlands||Along creek, waterin pond||Incidental ingestion,inhalation, dermalexposure||Hunters, fishers,trespassing children andadults||Past, present,future||Population may includechildren 10 years andolder||Y|
|Sediments||Deposition from surfacewater runoff into andalongside creek andponds||Along creek, waterin pond||Incidental ingestion,dermal exposure||Hunters, fishers,trespassing children andadults||Past, present,future||Population may includechildren 10 years andolder||Y|
|Soil||Erosion of waste tosurface soils;redeposition of fugitivedust||Site soils,residences nearby||Incidental ingestion,inhalation, dermalexposure||Nearby residents, hunters,fishers, trespassing childrenand adults||Past, present,future||Population may includechildren 10 years andolder||Y|
|Biota||Bioaccumulation ofcontaminants fromsurface water andsediments and vegetationinto fish and/or deer||Meal preparedusing fish fromsite pond or deerfrom site||Ingestion||Hunters, fishers, and theirfamilies||Past, present,future||Population may includetoddlers and childrenunder 10||Y|
|Well water||Infiltration togroundwater||Groundwater wellssupplying drinkingwater taps||Ingestion, inhalation,dermal exposure||Residents and workers nearthe site||Past, present,future||Population may includetoddlers and childrenunder 10||N|
|Air||Volatilization ofcontaminants; fugitivedust||Groundwater wellssupplying drinkingwater taps||Inhalation, dermalexposure||Residents and workers nearthe site||Past, present,future||Population may includetoddlers and childrenunder 10||N|
- How a chemical enters a person's blood after the chemical has been swallowed, has come into contact with the skin, or has been breathed in.
- Acute Exposure:
- Contact with a chemical that happens once or only for a limited period of time. ATSDR defines acute exposures as those that might last up to 14 days.
- Additive Effect:
- A response to a chemical mixture, or combination of substances, that might be expected if the known effects of individual chemicals, seen at specific doses, were added together.
- Adverse Health Effect:
- A change in body function or the structures of cells that can lead to disease or health problems.
- Antagonistic Effect:
- A response to a mixture of chemicals or combination of substances that is less than might be expected if the known effects of individual chemicals, seen at specific doses, were added together.
- 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.
- Background Level:
- An average or expected amount of a chemical in a specific environment. Or, amounts of chemicals that occur naturally in a specific environment.
- See Relative Bioavailability
- 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.
- Community Assistance Panel (CAP):
- A group of people from the community and health and environmental agencies who work together on issues and problems at hazardous waste sites.
- 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. This act created ATSDR and gave it the responsibility to look into health issues related to hazardous waste sites.
- How much or the amount of a substance present in a certain amount of soil, water, air, or food.
- See Environmental Contaminant.
- Delayed Health Effect:
- A disease or injury that happens as a result of exposures that may have occurred far in the past.
- 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 the Background Level, or what would be expected.
- Environmental Media:
- Usually refers to the air, water, and soil in which chemical 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.
- 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).
- 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.
- See Cancer.
- 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.
- 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.
- A line or column of air or water containing chemicals moving from the source to areas further away. A plume can be a column or clouds of smoke from a chimney or contaminated underground water sources or contaminated surface water (such as lakes, ponds and streams).
- Point of Exposure:
- The place where someone can come into contact with a contaminated environmental medium (air, water, food or soil). Some examples include:
the area of a playground that has contaminated dirt, a contaminated spring used for drinking water, 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.
- Potentially Responsible Party. A company, government or person that is responsible for causing the pollution at a hazardous waste site. PRP's are expected to help pay for the clean up of a site.
- Public Health Assessment(s):
- See PHA.
- 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.
- Relative Bioavailability:
- The amount of a compound that can be absorbed from a particularmedium (such as soil) compared to the amount absorbed from a referencematerial (such as water). Expressed in percentage form.
- 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
- 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.
- The Superfund Amendments and Reauthorization Act in 1986 amended CERCLA and expanded the health-related responsibilities of ATSDR. CERCLA and SARA direct ATSDR to look into the health effects resulting from chemical exposures at hazardous waste sites.
- Sample Size:
- The number of people that are needed for a health study.
- A small number of people chosen from a larger population (See Population).
- 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.
- A branch of the math process of collecting, looking at, and summarizing data or information.
- Superfund Site:
- See NPL.
- A way to collect information or data from a group of people (population). Surveys can be done by phone, mail, or in person. ATSDR cannot do surveys of more than nine people without approval from the U.S. Department of Health and Human Services.
- Synergistic effect:
- A health effect from an exposure to more than one chemical, where one of the chemicals worsens the effect of another chemical. The combined effect of the chemicals acting together are greater than the effects of the chemicals acting by themselves.
- 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.
- Uncertainty Factor:
- See Safety Factor.
- 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.
1. Based on conversations with Ardmore city officials, January 24, 2001.
2. Environmental Protection Agency (EPA). Exposure Factors Handbook. August 1997.
3. Environmental Protection Agency (EPA), Office of Emergency and Remedial Response. Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation Manual. December 1989.
4. Agency for Toxic Substances and Disease Registry (ATSDR). Cancer Policy Framework. January 1993.