PUBLIC HEALTH ASSESSMENT
DAVIS PARK ROAD TCE
GASTONIA, GASTON COUNTY, NORTH CAROLINA
The Davis Park Road Trichloroethene (TCE) site is located in the southwestern part of Gastonia,North Carolina, along Davis Park Road, south of Hudson Boulevard and north of BlackwoodCreek. Groundwater at the site was contaminated with volatile organic compounds (VOCs),including TCE and tetrachloroethene (PCE). These compounds reportedly originated fromcontaminated soil behind a local auto repair shop. Groundwater contamination was detected in anumber of private wells in the area. Residents have been provided with filters for their private wellsor put on the municipal water system.
Based on available information, the Agency for Toxic Substances and Disease Registry hasconcluded that the Davis Park Road TCE site warrants no health concerns at this time. Residents areno longer drinking contaminated water, and levels of contaminants in soil are too low to causehealth effects. In the past, the maximum levels of TCE detected in well water exceeded regulatorystandards and could have increased the risk of health effects if that water was used for drinking formany years.
ATSDR recommends that the Environmental Protection Agency (EPA) continue monitoring the groundwater at the site to confirm that contaminant levels are decreasing.
The Davis Park Road Trichloroethene (TCE) site was proposed for the National Priorities List(NPL) on July 28, 1998 and listed on January 19, 1999. The Agency for Toxic Substances andDisease Registry (ATSDR) is required by Congress to conduct public health assessments on all sitesproposed for the NPL. In this public health assessment, ATSDR evaluates the public healthsignificance of the Davis Park Road TCE site. ATSDR has reviewed available environmental data,potential exposure scenarios, and community health concerns to determine whether adverse healtheffects are possible. In addition, this public health assessment recommends actions to prevent,reduce, or further identify the possibility of site-related adverse health effects.
This site description comes from reports provided by the Environmental Protection Agency (EPA)[1,2,3]. The Davis Park Road TCE site ("the site") includes approximately 20 acres of residentialhomes and private businesses in unincorporated Gaston County, southwest of the city of Gastonia,North Carolina. The site consists of contaminated soil behind an automobile transmission shop(Davis Park Auto Repair) located at 2307 Davis Park Road, and contaminated groundwateremanating from this property and extending south along Davis Park Road to Blackwood Creek.Another potential source of contamination is gasoline leaking from underground storage tanks atGodwin Refrigeration, located approximately 150 feet north of Davis Park Auto Repair. Residencesare present above the entire extent of contaminated groundwater. A majority of the houses within thesite area obtained water from private or community wells. Tetrachloroethene (PCE), TCE, 1,1-dichloroethene (1,1-DCE), chloroform, and methyl tert-butyl ether (MTBE) are the groundwatercontaminants of concern identified in EPA's record of decision (ROD) for this site. .
The topography of the area is slightly sloped to the west toward Crowders Creek and to the east andsouth towards Blackwood Creek. Both creeks are receiving streams for groundwater in the area.
Contamination at the site was discovered in March 1990, when a routine groundwater samplecollected from the Cedar Oak Park community well by the Gaston County Environmental HealthDepartment (GCEHD) was found to contain volatile organic compounds (VOCs), including TCE,PCE, and chloroform. Follow-up sampling of community and private wells confirmed thecontamination and showed that the highest TCE concentrations were near Davis Park Auto Repair.
From May 1990 to January 1994, a series of soil and groundwater investigations were conducted atthe site by EPA, North Carolina Department of Environment, Health and Natural Resources(DEHNR), and Gaston County [1,3,4]. The results suggested that PCE, and possibly TCE, had beenreleased sometime in the past through a drainpipe behind Davis Park Auto Repair and that thesecontaminants and their breakdown products had moved through the soil into the underlyinggroundwater [1,3,4].
From May 1996 through April 1998, EPA conducted a remedial investigation (RI) to assess thenature and extent of site contamination. Results indicated minimal soil contamination (primarilypetroleum-related VOCs) behind Davis Park Auto Repair. In addition, VOCs in area wells werefound to be less numerous and at generally lower levels than in the previous studies. In the wellsclosest to the auto shop, which initially had the highest contaminant levels, VOCs were no longerdetectable [1,3].
In September 1998, EPA issued a ROD for the site. In the ROD, EPA presented its selectedremedial alternative for the site. The remedy included connection of homes, churches, and businessesin the site area to the Gastonia municipal water system, optional installation of carbon filters onprivate wells that have been affected by site contamination, and monitored natural attenuation of thegroundwater contamination, which is decreasing through dispersion and intrinsic biodegradation(breakdown by naturally occurring microorganisms). The groundwater will be tested forcontamination on a quarterly basis for 3 years and annually for 27 years. Monitoring will bediscontinued when groundwater contamination has declined to below drinking water standards asspecified in the ROD .
During the remedial design, a natural attenuation study was conducted to confirm that thecontaminant plume is naturally attenuating. A contingency remedy for active pumping andtreatment of the contaminated groundwater plume was provided for in the ROD, should the resultsof groundwater sampling fail to confirm natural attenuation. In a September 25, 2000,memorandum report, EPA confirmed that natural attenuation was occurring at the site and thatremedial goals would be achieved .
On-site construction was initiated on May 15, 2000. A total of 63 residences were connected to theGastonia municipal water system and are now receiving water from that system. EPA installedcarbon filters at 5 residences where the homeowners did not agree to be connected to the publicwater supply system. Two residents with private wells in the affected area chose not to receive eitherpublic water or a carbon filter. EPA also physically abandoned 19 private wells by plugging themwith a cement grout. Construction was determined to be complete on September 27, 2000 .
Demographic information is shown in Figure 1. The population of Gaston County was estimated tobe approximately 178,000 in 1995, with a 1990 population density of about 490 persons per squaremile. From 1980 until 1990, the county experienced a population increase of 15.3%. The city ofGastonia, the largest municipality in Gaston County, had a 1990 population of nearly 55,000 [1,3].
According to 1990 U.S. Census information, an estimated 5,264 people lived within a one-mileradius of Davis Park Auto Repair. Approximately 69% of the population was white, 30% wasblack, and less than 1% was of another racial or ethnic group.
The predominant land use in the immediate vicinity of the site is residential. Two of the largerneighborhoods are the Cedar Oak Park subdivision and the Hedgewood Circle area. Although mostof the site is outside the Gastonia city limits, it is still under city jurisdiction. The only commercialoperations within the site boundary are Davis Park Auto Repair and Godwin Refrigeration. Severalchurches are also located within the site boundary [1,3,5].
Before the remedial action, approximately 120 residences in the Davis Park Road area were servedby the Gastonia municipal water system. These 120 residences included 26 homes in the Cedar OakPark subdivision that were served by two community supply wells until February 1998, when theywere connected to the municipal water system. The water source for the municipal system is MountIsland Lake, located east-northeast of the city .
The remaining 170 residences in the site area used private or community wells for their householdwater needs. These wells range from 80 to over 250 feet in depth [1,4]. Groundwater is present in adeep aquifer in fractured bedrock more than 80 feet below ground surface (bgs) and in a shallowaquifer above a weathered rock layer ranging from 10 to 80 feet bgs. Because interconnection islikely, groundwater (and contaminants) can be transferred from one aquifer to the other [1,4].
At the site, groundwater generally flows toward the south or southeast and discharges to BlackwoodCreek along the eastern and southeastern edge of the site. However, local groundwater flow, andtherefore movement of contaminants, is also influenced by fractures in the rock layers and operationof area water supply wells. Measurements of hydraulic conductivities suggest that groundwatermoves most easily in the weathered rock of the shallow aquifer . Davis Park Auto Repair isbelieved to be located within a localized groundwater high area so that groundwater flows awayfrom the property in a semi-circular pattern .
The nearest surface water to the site is Blackwood Creek, located about 2,500 feet south of DavisPark Auto Repair. The creek flows along the south and southeast borders of the site and intoCrowders Creek, approximately 3,500 feet south of Davis Park Auto Repair. According topublished reports, Crowders Creek is not used for recreational purposes, except for very limitedbridge fishing several miles downstream of the site .
Several investigations of groundwater and soil from the site have been conducted. The dataevaluated in this report include results from the following studies.
- several investigations performed from 1990 to 1994 and reported in the RI Report [1,6].
- an expanded site investigation performed by DEHNR in January 1994 .
- a remedial investigation performed in 3 phases by EPA from May 1996 to April 1998 .
Appendix A contains details on the groundwater and soil samples evaluated. ATSDR's review of thedata reports indicated that appropriate quality control measures were taken in the preparation of theanalytical data. The conclusions reached in this document are based on the data listed above andmay be modified if new environmental data become available.
ATSDR visited the site(1) to better understand the physical setting of the site and its relationship to thepeople living and working nearby. During the site visit, the following observations were made:
- The site area was primarily residential (single family homes).
- The site area included two businesses - an automobile repair shop and a commercial refrigeration business - and several churches.
- At the time of the site visit, the automobile repair shop on Davis Park Road - the suspected groundwater contamination source - was currently doing business under the name Davis Park Auto Repair. At least 20 vehicles (cars and trucks) were parked in front of the shop awaiting repair, and a number of additional vehicles (cars, trucks, and boats) were stored behind the shop.
- The nearest house was located less than 50 feet north of the repair shop on Davis Park Road.
The process by which ATSDR evaluates the possible health impact of contaminants is summarizedhere and described in more detail in Appendix B. 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 or not the exposure presents a health hazard. More information on these calculations isprovided in Appendix C.
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 D 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.
Contaminants have been detected in the groundwater beneath the site. People drinking thisgroundwater could be exposed to these contaminants. For this analysis, we considered watersampling results from private wells and from converted former residential wells collected during theRI . The converted residential wells were included with the monitoring well section of the RI, butwe treated them as drinking water wells in this document since people once used them for drinkingpurposes. Data from the other monitoring wells were not considered since contaminantconcentrations measured in monitoring wells were in the same range as the drinking water wells andpeople do not generally drink water from monitoring wells. Table 1 lists the contaminants ofconcern, compounds that were detected at least once above the corresponding CV.
|Contaminant||ConcentrationRange in partsper billion (ppb)||Frequency ofDetection /Total||ComparisonValue (CV) inppb||CV Source1|
|Benzene||ND - 26||3 / 97||5 / 0.6||MCL2 / CREG3|
|Bromodichloromethane||ND - 6||1 / 97||200 / 0.6||EMEG4 / CREG|
|Chloroform||ND - 40||1 / 97||100 / 6||EMEG / CREG|
|Dibromochloromethane||ND - 0.6||1 / 97||300 / 0.4||EMEG / CREG|
|Dichloroethane||ND - 0.6||2 / 97||2000 / 0.4||EMEG / CREG|
|1,1-DCE||ND - 4||3 / 97||90 / 0.06||EMEG / CREG|
|MTBE||ND - 5096||5 / 97||200||LTHA5|
|PCE||ND - 24||18 / 97||5||MCL|
|TCE||ND - 134||43 / 97||5||MCL|
|Source:  |
1 These comparison values are described in Appendix B.
2 MCL = maximum contaminant level
3 CREG = cancer risk evaluation guide.
4 EMEG = environmental media evaluation guide.
5 LTHA = lifetime health advisory
Next, exposure doses were calculated for the contaminants of concern in Table 1. The worst casewas assumed to be a one-year-old child weighing 11 kilograms (kg) drinking one liter per day ofwater containing the maximum concentration of each contaminant for 350 days out of the year .The exposure dose estimated through this procedure was compared with health guideline values andtoxicological information for the contaminant of concern. For evaluating the risk of cancer, weassumed that adults weighing 70 kg would be exposed to the maximum concentration of eachcontaminant for 350 days a year for the 34 years that contamination was possible (from 1966, whenthe auto repair shop opened, to 2000, when homes were connected to the municipal water system).This dose was multiplied by 2 to account for additional dermal and inhalation exposure duringshowering . When this analysis was performed, doses for benzene, bromodichloromethane,chloroform, dibromochloromethane, 1,1-DCE, and PCE were found to be lower than the applicablenoncancer health guidelines and/or within EPA's acceptable cancer risk range (less than 1×10-4) andwere dropped from further consideration [9,10,11,12,13,14,15,16,17,18].
Details of the calculations and tables containing the calculated exposure doses and excess cancerrisks are included in Appendix C. The following sections describe the evaluation of the remaining contaminants of concern from Table 1.
The child exposure dose calculated using the highest concentration of MTBE measured in drinkingwater is 1.5 times higher than the intermediate oral minimal risk level (MRL) . This MRL isbased on a lowest observed adverse effect level (LOAEL) of 100 mg/kg/day in studies on rats .At the LOAEL, kidney function effects were observed. No health effects are expected from thisexposure because the calculated dose is 250 times smaller than the LOAEL. However, peopledrinking water containing MTBE at levels higher than about 20 parts per billion (ppb) might detectunpleasant tastes and odors from the MTBE in their water .
The International Agency for Research on Cancer (IARC) has determined that MTBE is notclassifiable as a human carcinogen . There is insufficient evidence that it causes cancer inhumans and only limited animal data . No evaluation of cancer risk was performed.
The child exposure dose calculated using the highest concentration of TCE measured in drinkingwater is 0.01 milligrams per kilogram per day (mg/kg/day). Animal studies have shown effect levelsseveral orders of magnitude higher than this dose . However, some epidemiologic studies havesuggested that drinking TCE at levels similar to the maximum at this site for long periods isassociated with skin problems, liver and kidney damage, impaired immune system function, andimpaired fetal development in pregnant women . These studies are controversial because therewere other contaminants present in the water which may have caused the observed health effects,some studies had too few people in them, and TCE effect levels were not well-defined .Although still unlikely, if people drank the most highly contaminated water at the site for severalyears, they may have an increased risk of the above health effects.
The International Agency for Research on Cancer (IARC) has determined that TCE is a probablehuman carcinogen . EPA is currently reviewing the cancer slope factor for this substance .Assuming a person drank 2 liters of water containing TCE at the maximum concentration every dayfor the entire 34 years that contamination was possible (from 1966 to 2000), and assuming aconservatively high cancer slope factor of 0.4 (mg/kg/day)-1, the predicted increased risk of cancerwould be low to moderate.
ATSDR also considered how concurrent exposure to the other chemical contaminants in addition toTCE in well water may have affected people. Because the worst case scenario (long-term exposureto the maximum level) showed no adverse health effects were expected for the other individualcontaminants, the presence of other contaminants is not expected to have a significant additive effectto the risk of health effects from TCE. In addition, the increased risk of cancer from cumulativeexposures is not considered to be of concern because of the low risks calculated for the individualcontaminants and the conservative assumptions described above.
Many wells on the site had contaminant levels much lower than the maximums discussed above, toolow to cause health effects. Homeowners at the site have been informed of the results of testing oftheir wells, and all but two homes were connected to the Gastonia municipal water system or hadcarbon filters installed on their wells, effectively disrupting this exposure pathway . It isimpossible to tell whether past exposures could lead to the above long-term health effects withoutmore specific information about how long people were drinking contaminated water and the levelsof contaminants in each well over time. The risk to the residents who chose not to receive eitherpublic water or a carbon filter depends on the actual contaminant levels in their wells and theirspecific exposure scenario. Sampling by EPA showed reductions of contaminants in the groundwaterover time, indicating that these contaminants are being naturally attenuated . Therefore, while thewell water pathway could have posed a public health hazard in the past, since the pathway has beendisrupted it is not considered to pose a current public health hazard.
People on the site could come into direct contact with contaminants in soil. They could getcontaminated soil on their skin, or they might accidentally eat or breathe in soil particles. Table 2 lists the contaminants that were found in the soil on site at levels above soil CVs. Only surface soilsamples were considered, since people would not normally come in contact with soil beneath the ground surface.
|Contaminant||Concentration Range in parts per million (ppm)||Frequency of Detection / Total||ComparisonValue (CV) inppm||CV Source1|
|Arsenic||ND - 15||7 / 7||20 / 0.5||EMEG2 / CREG3|
|Lead||20 - 630||7 / 7||400||SSL4|
|Source: [1,3,4] |
1 These comparison values are described in Appendix B.
2 EMEG = environmental media evaluation guide.
3 CREG = cancer risk evaluation guide.
4 SSL = EPA soil screening level.
Although initial investigations had shown significant levels of PCE, TCE, and DCE (a PCE/TCEbreakdown product) in soils behind the auto repair shop, all data presented in the RI report showednondetectable levels of these contaminants in surface soils, indicating that they had already brokendown or volatilized . In addition, the below ground surface samples showed significant reductionsin contaminants over time, indicating that these contaminants were being naturally attenuated .None of the volatile contaminants were present at levels above CVs .
Exposure doses were calculated for the contaminants of concern in Table 2. The worst case wasassumed to be a 10-year-old child (36.3 kg average weight) contacting the maximum concentrationof each contaminant all day for 52 days out of the year (once a week) . The exposure doseestimated through this procedure was compared with health guideline values and toxicologicalinformation for the contaminant of concern. For evaluating the risk of cancer, we assumed adultsweighing 70 kg would be exposed to the maximum concentration of each contaminant for 52 days ayear for a lifetime (70 years). When this evaluation was performed, the exposure dose for arsenicwas below applicable cancer and noncancer health guidelines and it was dropped from consideration. For lead, the blood lead level increase predicted in a worst-case scenario was below healthguidelines, and it was also dropped from consideration . Therefore, the surface soils are notconsidered to pose a health hazard. Details of the calculations and tables containing the calculatedexposure doses and excess cancer risks are included in Appendix C.
Water from surface runoff on the site may pick up contaminants from soils, sediments, orgroundwater. No use of this water for drinking water purposes was identified, but people who liveon or visit the site might accidentally ingest some of the surface water or get it on their skin whilewading or swimming in the creeks or ponds on site. Nine surface water samples were collected fromBlackwood Creek and Crowders Creek downstream of the auto repair shop during the RI. Nocontaminants were detected in any surface water sample [1,3]. Because there are no contaminantspresent, the surface water pathway is considered incomplete.
People who live on or visit the site might accidentally ingest some of the sediments from the pondsor streams on the site or get them on their skin while wading or swimming there. Six sedimentsamples were collected from the creek near the site. No compounds were detected above screeninglevels . The sediment pathway is therefore considered incomplete.
ATSDR recognizes that infants and children may be more vulnerable to exposures than adults in communities 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 routes for children living on the site are ingestion of drinking water andingestion of surface soil. Please refer to the appropriate sections of this report for discussions of thepossible 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 (the number of people dying from a certaindisease) or morbidity information (the number of people in an area getting a certain disease). Inorder to thoroughly evaluate health outcome data as it relates to a hazardous waste site, thefollowing elements are necessary: (1) the presence of a completed human exposure pathway, (2)sufficiently high contaminant levels to result in measurable health effects, (3) sufficient number ofpeople in the completed pathway for the health effect to be measured, and (4) a health outcomedatabase 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. Although completed human exposure pathways existed at this site, thosepathways have been disrupted and the former contaminant levels, exposures, and exposed populationare not great enough to result in a meaningful measurement of health outcome data.
On March 25, 1999, ATSDR staff held a public availability session at the Taylor Memorial BaptistChurch to gather community concerns about the Davis Park Road TCE site. Approximately 21people attended the session, including 18 residents and 3 city or county officials. Most of theresidents were interested in finding out what ATSDR was doing at the site and in getting informationabout TCE and PCE, two of the major groundwater contaminants associated with the site. Some ofthe residents asked whether their well water was safe and some suggested that we contact the GastonCounty Health Department or EPA to obtain the sampling data for their wells. Residents who askedabout the status of EPA's plans and activities for the site were referred to the EPA remedial projectmanager.
A few of the residents indicated that they were experiencing health problems and wondered if theywere related to the site. The specific concerns raised and ATSDR's responses are detailed below.
Concern: What are the long-term health effects for children and adults who drank private wellwater shown to contain site-related contaminants?
Response: It is unlikely that people will exhibit health effects from drinking well water from the site. If a person drank water with the highest concentration of TCE for several years, they would have an increased, although still very small, risk of health effects. See the discussion of the well water pathway on page 7 of this document.
Concern: Did the contaminants in private well water cause brain tumors, lung cancer, and otherhealth problems, including headaches, chronic cough, sinusitis, bronchitis, cysts, skin andintestinal disorders in residents at the site?
Response: Some epidemiologic studies have suggested that exposure to TCE in drinking water cancause health effects, but the studies are controversial because of their limitations. In addition, we donot know enough about past contaminant levels in people's well water and how much well waterthose people were drinking to determine the risk for health effects. Based on the available data,however, it is unlikely that any people were exposed to contaminants at high enough levels for along enough time to result in health effects.
Concern: Can't the government close down the Davis Park Auto Repair shop and remove thejunk cars leaking oil in my neighbor's backyard?
Response: ATSDR is a non-regulatory, public health agency and does not have any authority toclose down the auto repair shop or remove junk cars from residential properties. ATSDR suggeststhat these issues be discussed with the local zoning authority.
During the March 1999 site visit, ATSDR staff also contacted local health officials to gatheradditional information regarding health concerns about the site. These officials indicated that fewresidents had expressed health concerns about the Davis Park Road site contamination.
In addition to the March 1999 availability session, the Davis Park Road TCE Public HealthAssessment was available for public review and comment from August 23 to March 25, 2002, at theGaston County Public Library in Gastonia, NC. 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. Thefollowing written comments were received.
(from North Carolina Department of Environment and Natural Resources)
Page 8, first paragraph, last line: The statement that the risk calculations are overlyconservative is too strong based on the arguments that follow. The arguments that "mostwells did not contain the maximum concentration contaminants", and "contaminantlevels probably varied over time" ignore the fact that contaminant levels were onlymonitored at this site for 12 of the 34 years of its potential existence. Prior tocontamination discovery in 1990, there may have been periods when people wereexposed to water from these wells that had contaminant levels greater than have beendetected in the last 12 years. While there are many other areas in risk assessment thatare biased towards conservatism, there is too much uncertainty in the two argumentspresented above to support such a strong statement. A similar argument is made on page9, TCE, end of second paragraph.
ATSDR agrees that there is not enough past information to make the statements listed in theabove comment. These statements have been removed from the document.
(from a former site resident, paraphrased)
Concerns expressed over contaminated well water causing stomach, muscle, bone, andheart problems.
Some epidemiologic studies have suggested that exposure to TCE in drinking water cancause health effects, but the studies are controversial because of their limitations. In addition,we do not know enough about past contaminant levels in people's well water and how muchwell water those people were drinking to determine the risk for health effects. Based on theavailable data, however, it is unlikely that any people were exposed to contaminants at highenough levels for a long enough time to result in health effects.
People may have been exposed in the past to levels of TCE that exceeded regulatory guidelines andmay have slightly increased the risk of health effects. Therefore, ATSDR considers the Davis ParkRoad TCE site a past public health hazard (as defined in Appendix E).
Because people are no longer drinking contaminated water from the site and because contaminantlevels in soil are too low to cause health effects, ATSDR considers the Davis Park Road TCE site tocurrently pose no apparent public health hazard (as defined in Appendix E).
- The maximum levels of TCE detected in well water exceeded regulatory standards andcould increase the risk of long-term noncancer health effects and cancer if that water wasused for drinking for many years. ATSDR considers the site a past public health hazard.
- Because the well water pathway has been effectively disrupted, it does not pose a publichealth hazard at this time.
- Arsenic and lead detected in site soils were present at levels too low to result in health effects.
- ATSDR supports EPA's plan for continued monitoring of the groundwater to ensure naturalattenuation of contaminants.
The public health action plan for the Davis Park Road site contains a description of actions that havebeen or will be taken at the site by ATSDR and/or other government agencies. The purpose of theplan is to ensure that this public health assessment not only identifies public health hazards at thesite, but also outlines a plan of action to prevent or minimize the potential for adverse human healtheffects from exposure to site-related hazardous substances. ATSDR will follow up on this plan toensure that it is implemented.
- ATSDR conducted a site visit in order to verify site conditions and to gather pertinent information and data for the site.
- ATSDR held a public availability session to gather health concerns from the site community.
- EPA completed the RI activities for the site.
- EPA connected homes, churches, and businesses in the site area to the City of Gastonia municipal water system and/or installed carbon filters on private wells that were impacted by site contamination.
- EPA will continue monitoring groundwater at the site.
ATSDR will reevaluate and expand the public health action plan if needed. New environmental,toxicological, or health outcome data or the results of implementing the above proposed actions maydetermine the need for additional actions at this site.
Authors of Report
Jill J. Dyken, Ph.D., P.E.
Environmental Health Scientist
Division of Health Assessment and Consultation
Moses Kapu, Ph.D.
Environmental Health Scientist
Division of Health Assessment and Consultation
Stephen Richardson, P.E.
Environmental Health Engineer
Division of Health Assessment and Consultation
Senior Regional Representative
ATSDR Region IV
Community Involvement Specialist
Division of Health Assessment and Consultation
Health Education Specialist
Division of Health Education and Promotion
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- US Environmental Protection Agency. Integrated Risk Information System (IRIS) website.Washington (DC): EPA Office of Research and Development; revised September 28, 2001.Accessed electronically at: http://www.epa.gov/iris/ .
- 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.
Private well sampling
From May 1990 to July 1993, approximately 26 private and community wells in the site area,including the Cedar Oak Park community well, were sampled by EPA, the state of North Carolina,and Gaston County. At least 14 of the samples contained detectable levels of TCE and/or PCE. Thehighest TCE and PCE levels were generally found in the Cedar Oak Park community well and inwells close to and down gradient (south and southeast) of the Davis Park Auto Repair shop. VOCsnormally associated with gasoline contamination, such as benzene and MTBE, were found in twowells just west of the auto repair shop. The presence of benzene and MTBE in these wells may beattributed to gasoline contamination from the Godwin Refrigeration property, which is locatedwithin a few hundred feet of the wells [1,4,6].
During the January 1994 expanded site investigation by the state of North Carolina, 5 private wellsnear the auto repair shop that had previously been found to contain VOCs were sampled. Thesampling results showed TCE and PCE, along with traces of other VOCs, in several of the wells.The highest TCE and PCE levels were found in the Cedar Oak Park community well. In general, thecontaminant levels were lower than those found in previous years .
In May 1996, during Phase I of the RI field activities, groundwater samples were collected for VOCanalysis from 29 residential wells in the site area. The well locations are shown in Figure 5. VOCswere detected in several of the wells, including the Cedar Oak Park community well, which againhad the highest levels of TCE and PCE. Most of the wells closest to the auto shop (historicallyamong the most contaminated area wells) showed little contamination. Samples from 4 of the wellswere also analyzed for metals. A number of metals were detected in these samples, but the levels donot exceed health CVs [1,3].
In February 1998, during Phase III of the RI, groundwater samples were collected from 3 privatewater supply wells in the site area. PCE was detected in 1 well, and TCE was found in all 3 wells.Among the 3 wells, the lowest TCE level (about half the May 1996 level) was found in the wellclosest to the auto shop. No other VOCs were detected in the 3 wells [1,3].
Monitoring Well Sampling (includes converted former residential wells)
In May 1996, during Phase I of the RI field activities, groundwater samples were collected from 2existing monitoring wells at the Davis Park Auto Repair shop. No VOCs, pesticides, or PCBs weredetected in either of the wells. Various metals were detected in both wells, but the levels do notexceed health CVs [1,3]. RI Phase II groundwater samples were collected in October 1996 fromtemporary monitoring wells installed at 3 locations on the Davis Park Auto Repair property and atone location southeast of the shop near Blackwood Creek. Low levels of TCE and toluene weredetected in 2 of the monitoring wells on the auto shop property [1,3].
In January 1998, during Phase III of the RI, groundwater samples were collected from the 2 existingmonitoring wells at the Davis Park Auto Repair shop; 9 newly installed monitoring wells southeast,south, southwest, and west of the auto shop; and 6 former residential wells which had beenconverted to monitoring wells. Several VOCs, including PCE, TCE, and MTBE, were detected inthe wells. The highest PCE and TCE levels were detected at the former Cedar Oak Park communitywell, while the highest MTBE concentrations were found in a former residential well west of theauto shop. MTBE in the former residential well may have been associated with gasolinecontamination from the nearby Godwin Refrigeration operation, located about 150 feet north of theauto shop. According to published documents, releases from the Godwin Refrigeration property,where two underground storage tanks (USTs) were used to store gasoline until 1992, wereresponsible for contamination of nearby private wells with gasoline-type contaminants .
In April 1998, during Phase III of the RI, an additional groundwater sample was collected from asoil boring adjacent to the auto shop. Only low levels of MTBE were detected [1,3].
From May 1990 to August 1992, the NCDENR sampled soils around the Davis Park Auto Repairshop several times. These samples showed significant levels of PCE, TCE, and DCE (a PCE/TCEbreakdown product) in soils behind the shop near a drainpipe that exited the shop's service bays .
During a January 1994 expanded site investigation, the State of North Carolina sampled soils nearthe drainpipe behind the Davis Park Auto Repair shop. The sampling results showed TCE, DCE,and petroleum-type VOCs (toluene, ethyl benzene, and xylene) in the soils around the drainpipe.However, the TCE and DCE soil levels were significantly lower than the 1990-1992 levels [1,3,4].
In May 1996, during Phase I of the EPA RI field activities, 6 surface soil (0 to 6 inches belowground surface [bgs]), and 9 subsurface soil samples were collected from the auto shop property andanalyzed for VOCs, semi-volatile organic compounds (SVOCs), pesticides, PCBs, and metals. Noorganic contaminants were detected in the surface samples except low levels of the pesticide dieldrinin one sample. Petroleum-type VOCs (ethyl benzene, toluene, and xylene) and a number of SVOCswere detected in 2 of the subsurface soil samples, and the pesticide toxaphene was detected in onesubsurface sample. Various metals were detected in both surface and subsurface sample. Metalslevels were generally consistent with local background levels, with the exception of lead, which wasfound at elevated levels in several samples [1,3].
In October 1996, during Phase II of the RI field activities, 9 subsurface soil samples were collectedfrom 8 locations around the auto repair shop; 3 of the samples were taken from areas behind theshop where soil contamination was previously found. No VOCs were detected except bromoform,which was detected in only one sample [1,3].
In December 1997, during Phase III of the RI field activities, 10 subsurface soil samples werecollected from a single boring behind the auto repair shop, and 4 subsurface samples were collectedduring installation of 4 monitoring well boreholes southeast, south, and southwest of the auto shop.No VOCs were detected in any of the samples except benzene, which was found in one soil sample(39 to 41 feet bgs) from behind the auto shop. In April 1998, an additional 9 subsurface soil sampleswere collected from 7 borings around the auto shop. No VOCs were found in any of these samples[1,3].
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, or 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. Different CVs are developed for cancer and noncancerhealth effects. Noncancer levels are based on valid toxicologic studies for a chemical, withappropriate safety factors included, and the assumption that exposure occurs every day. Cancerlevels are the media concentrations at which there could be a one in a million excess cancer risk foran adult eating contaminated soil or drinking contaminated water every day for 70 years. Forchemicals for which both cancer and noncancer numbers exist, the lower level is used to beprotective. Exceeding a CV does not mean that health effects will occur, just that more evaluation isneeded.
CVs used in this document are listed below:
Environmental Media Evaluation Guides (EMEGs) are estimated contaminantconcentrations in a media where noncancer health effects are unlikely. The EMEG is derivedfrom ATSDR's minimal risk 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 EPA's cancer slope factors.
Lifetime Health Advisories (LTHAs) are derived by EPA from a drinking water equivalentlevel below which no adverse noncancer health effects are expected to occur over a 70-yearlifetime.
Maximum Contaminant Levels (MCLs) are enforceable drinking water regulationsestablished by EPA under the Safe Drinking Water Act that are protective of human healthto the extent feasible both technologically and economically. The MCL assumes exposureover a 70-year lifetime and ingestion of 2 liters of water per day.
Reference Media Evaluation Guides (RMEGs) are estimated contaminant concentrations ina media where noncancer health effects are unlikely. The RMEG is derived from EPA'sreference dose (RfD).
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 reduceexposure.
Evaluation of Public Health Implications
The next step is to take those contaminants that are above the CVs and further identify whichchemicals and exposure situations are likely to be a health hazard. Child and adult exposure dosesare calculated for the site-specific exposure scenario, using our assumptions of who goes on the siteand how often they contact the site contaminants. The exposure dose is the amount of a contaminantthat gets into a person's body. Appendix C details how exposure doses were calculated for this site.
Noncancer Health Effects
The calculated exposure doses are then compared to an appropriate health guideline for thatchemical. Health guideline values are considered safe doses; that is, health effects are unlikely belowthis level. The health guideline value is based on valid toxicologic studies for a chemical, withappropriate 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 healthguideline values are used.
Minimal Risk Level (MRLs) - developed by ATSDR
An estimate of daily human exposure - for a specified route and duration - to a dose of chemical that is likely to be without a measurable risk of adverse, noncancer effects. An MRL should not be used as a predictor of adverse health effects. A list of MRLs is available at http://www.atsdr.cdc.gov/mrls.html.
Reference Dose (RfD) - developed by EPA
An estimate of the daily, life-time exposure of human populations to a possible hazard that is not likely to cause noncancer health effects. The RfDs is available at http://www.epa.gov/iris/ .
If the estimated exposure dose for a chemical is less than the health guideline value, then theexposure is unlikely to cause a noncancer health effect in that specific situation. If the exposure dosefor a chemical is greater than the health guideline, then the exposure dose is compared to knowntoxicological values for that chemical and is discussed in more detail in the public health assessment.These toxicological values are doses derived from human and animal studies which are summarizedin the ATSDR toxicological profiles. A direct comparison of site-specific exposure and doses tostudy-derived exposures and doses found to cause adverse health effects is the basis for decidingwhether health effects are likely or not.
Calculation of Excess Cancer Risk
The estimated risk of developing cancer from exposure to the contaminants is calculated bymultiplying the site-specific adult exposure dose by EPA's corresponding cancer slope factor(available at http://www.epa.gov/iris/ ). For the air pathway, the maximum air concentration ismultiplied by the corresponding cancer slope factor. The results estimate the maximum increase inrisk 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 tocalculate the cancer slope factor assumes that high-dose animal data can be used to estimate the riskfor 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 methodcomputes the 95% upper bound for the risk, rather than the average risk, suggesting that the cancerrisk is actually lower, perhaps by several orders of magnitude.(2)
Because of uncertainties involved in estimating cancer risk, ATSDR employs a weight-of-evidenceapproach in evaluating all relevant data(3). Therefore, the cancer risk is described in words(qualitatively) rather than giving a numerical risk estimate only. The numerical risk estimate mustbe considered in the context of the variables and assumptions involved in their derivation and in thebroader context of biomedical opinion, host factors, and actual exposure conditions. The actualparameters of environmental exposures must be given careful consideration in evaluating theassumptions and variables relating to both toxicity and exposure.
Well Water Pathway
The ATSDR exposure dose formula used for the well water pathway is:
ed = exposure dose in milligrams per kilogram per day (mg/kg/day);
c = maximum concentration in water in micrograms per liter (µg/L);
ir = ingestion rate in liters per day (L/day);
ef = exposure factor, days of exposure divided by 365 days per year (unitless);
1000 = conversion factor of micrograms per milligram (µg/mg);
bw = body weight in kilograms (kg).
Assumptions used were based on default values and/or professional judgment . The incidentaldrinking water ingestion rate for adults was 2 L/day and for children was 1 L/day. For average bodyweight, 70 kg and 11 kg was used for adults and 1-year-old children, respectively. The exposurefactor was 350/365, because the exposure was assumed to occur 350 days a year. The adultexposure was multiplied by 2 to account for dermal and inhalation exposure during showering .The child doses were larger and were used for initial screening.
The doses for children resulting from this calculation for well water contaminants of concern areshown in Table C1. Child doses for benzene, bromodichloromethane, chloroform,dibromochloromethane, dichloroethane, 1,1-DCE, and PCE were below the health guidelines.MTBE and TCE were retained for further analysis in the document text.
|Contaminant||Maximum concentration, micrograms per liter (µg/L)||Child dose, milligrams per kilogram per day (mg/kg/day)||Health guideline (HG), mg/kg/day||HG source|
|1 chronic oral minimal risk level. |
2 intermediate oral minimal risk level.
3 no health guideline available.
Excess cancer risk is estimated by multiplying the adult exposure dose by the cancer slope factor.This is then multiplied by the fraction 34/70, because the cancer slope factor assumes a 70-yearlifetime of exposure, whereas the maximum time anyone at this site could have been exposed was 34years (from 1966 when the auto repair shop opened to 2000 when homes were connected to themunicipal water system). Table C2 tabulates the results of this calculation for the well watercontaminants of concern. The excess cancer risk for benzene, bromodichloromethane, chloroform,dibromochloromethane, dichloroethane, 1,1-DCE, and PCE is within EPA's acceptable risk range of1×10-6 to 1×10-4. MTBE is not classifiable as to its potential to cause cancer in humans and isdiscussed further in the document. TCE was also retained for further evaluation. The oral cancerslope factor has been withdrawn for review at the time of the writing of this document.
|Contaminant||Maximumconcentration,micrograms perliter (µg/L)||Cancer slope factor,1 / milligrams perkilogram per day(mg/kg/day)-1||Adult dose,mg/kg/day||Excesscancer risk|
|1 no cancer slope factor available.|
The ATSDR exposure dose formula used for the soil pathway is:
ed = exposure dose in milligrams per kilogram per day (mg/kg/day);
c = maximum concentration in soil in milligrams per kilogram (mg/kg);
ir = ingestion rate in milligrams per day (mg/day);
ef = exposure factor, days of exposure divided by 365 days per year (unitless);
1×10-6 = conversion factor of kilograms per milligram (kg/mg);
bw = body weight in kilograms (kg).
Assumptions used were based on default values and/or professional judgment . The incidentalsoil ingestion rate for adults was 100 mg/day and for children was 200 mg/day. For average bodyweight, 70 kg and 36.3 kg was used for adults and 10-year-old children, respectively. Childrenyounger than 10 years old are assumed to not access the site. The exposure factor was 52/365,because the exposure was assumed to occur on average once a week throughout the year.
The doses for children resulting from this calculation for soil contaminants of concern are shown inTable C3. The child dose for arsenic was below the health guideline. For lead, we used the mostprotective correlation between blood lead levels and soil concentration found in epidemiologicalstudies, 0.0068 microgram per deciliter (µg/dL) increase in blood lead level per mg/kg of lead insoil. For the maximum lead concentration measured in soil, blood lead levels could be expected toincrease by 4.3 µg/dL. Because this is a protective calculation (i.e., children would be exposed to anaverage rather than the maximum concentration) and blood lead levels are not considered elevateduntil they reach 10 µg/dL, lead exposure is not considered a problem for this site.
|Contaminant||Maximum concentration, milligrams per kilogram (mg/kg)||Child dose, milligrams per kilogram per day (mg/kg/day)||Health guideline (HG), mg/kg/day||HG source|
|1 chronic oral minimal risk level. |
2 no health guideline available.
Excess cancer risk is estimated by multiplying the adult exposure dose by the cancer slope factor;Table C4 tabulates the results of this calculation for the soil contaminants of concern. The excesscancer risk for arsenic is within EPA's acceptable risk range of 1×10-6 to 1×10-4. Lead is a probablehuman carcinogen, but no cancer slope factor is available so it was impossible to quantitativelyassess risk.
|Contaminant||Maximumconcentration,milligrams perkilogram (mg/kg)||Cancer slope factor,1 / milligrams perkilogram per day(mg/kg/day)-1||Adult Dose,mg/kg/day||Excesscancer risk|
|1 no cancer slope factor available.|
|Source for all pathways: Solvent and/or petroleum disposal, spillage, and/or leakage at auto repair shop|
|PATHWAYNAME||ENVIRONMENTALMEDIA & TRANSPORTMECHANISMS||POINT OFEXPOSURE||ROUTE OFEXPOSURE||EXPOSUREPOPULATION||TIME||NOTES||Complete?|
|Well Water||Infiltration to groundwater||Residences withcontaminated drinkingwater wells||Ingestion, inhalation,dermal exposure||Residents||Past,Present||Population mayinclude youngchildren.||Y|
|Soils||Disposal, spillage, or leakage ofwaste materials||Auto shop property,especially near the olddrainpipe||Incidental Ingestion,inhalation, dermalexposure||Site workers,trespassing childrenand adults||Past,Present||Population mayinclude children 10years and older.||Y|
|Surface Water||Surface water runoff overcontaminated soil to creek||Along BlackwoodCreek||Incidental ingestion,dermal exposure||Residents and sitevisitors wading orplaying in creek||Past,Present||Population mayinclude children 10years and older.||N|
|Sediment||Surface water runoff overcontaminated soil to creek||Along BlackwoodCreek||Incidental ingestion,dermal exposure||Residents and sitevisitors wading orplaying in creek||Past,Present||Population mayinclude children 10years and older.||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 (CV):
- 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.
- 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 that found in 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.
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).
- 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). 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.
- 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 particular medium (such as soil) compared to the amount absorbed from a reference material (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
- 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.
- 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 from chemical exposures at hazardous waste sites.
- Sample Size:
- The number of people that are needed for a health study.
- A smallnumber 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. ATSDR Staff (Steve Richardson, Moses Kapu, Steve Blackwell, LaFreta Dalton, and Bob Safay) visited the site on March 25, 1999 with a member of the Gaston County Health Department (Doc Thompson).
2. Environmental Protection Agency (EPA), Office of Emergency and Remedial Response. Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation Manual. December 1989.
3. Agency for Toxic Substances and Disease Registry (ATSDR). Cancer Policy Framework. January 1993.