PUBLIC HEALTH ASSESSMENT
LAIDLAW ENVIRONMENTAL SERVICES (TOC), INCORPORATED
ROEBUCK, SOUTH CAROLINA
Figure 1: Facility Location Map
Figure 2: Facility Site Plan Diagram
Figure 3: Cancer Study 1.5 Mile Radius
Figure 4: Location of Surface Water Bodies with Respect to Laidlaw
Figure 5: Location of Air Monitoring Stations with Respect to Laidlaw
Figure 6: Location of Groundwater Monitoring Wells
Figure 7: Demographic Statistics for Within One Mile of Laidlaw
Figure 8: Aerial Extent of VOC Contamination Based on 1996 Data
Figure 1: Facility Location Map
Figure 2: Facility Site Plan Diagram
Figure 3: Cancer Study 1.5 Mile Radius
Figure 4: Location of Surface Water Bodies with Respect to Laidlaw
Figure 5: Location of Air Monitoring Stations with Respect to Laidlaw
Figure 6: Location of Groundwater Monitoring Wells
Figure 7: Demographic Statistics for Within One Mile of Laidlaw
Figure 8: Aerial Extent of VOC Contamination Based on 1996 Data
Table 1: Completed Exposure Pathways
Table 2: Potential Exposure Pathways
Table 3: Groundwater Sampling Results -- Organics
Table 4: Groundwater Sampling Results -- Inorganics
Table 5: Off-site Air Sampling Results for 1986-1989 -- Organics
Table 6: Off-site Air Sampling Results for 1986-1989 -- Inorganics
Table 7: On-site Soil Sampling Results for 1988-1989 -- Organics
Table 8: On-site Soil Sampling Results for 1988-1989 -- Inorganics
Table 9: On-site Pond Sampling Results for 1980-1981
a Please refer to Appendix C for information on comparison values.
a Please refer to Appendix C for information on comparison values.
a Please refer to Appendix C for information on comparison values.
B The -- indicates no data available for the time frame reviewed.
C The comparison value (chronic EMEG) for naphthalene is 2 ppb or 10 ug/m3.
a Please refer to Appendix C for information on comparison values.
b The -- indicates no data available for the time frame reviewed.
C Note: From a risk assessment point of view, the population within 1 mile of the site (< 1,300) is not large enough to express the small theoretical cancer risk associated with the maximum detected concentrations of arsenic and nickel (0.007 per thousand and 0.015 per thousand, respectively)in anything less than 7,000 years. The concentration of nickel at Parklane appears to be 10-100 times too high for a true background level. The lower concentrations at Cromer and Pecan are within the range of concentrations found in urban areas without a metallurgy industry.
a Background samples were taken from on-site locations not expected to have been impacted from site activities
b D = secondary dilution needed
c The -- indicates no data available
d BDL = below detection limit
e Please refer to Appendix C for information on comparison values.
a Background samples were taken from on-site locations not expected to have been impacted from site activities
b The -- indicates no data available
c x = matrix interference which may require a dilution
d BDL = below detection limit
e Please refer to Appendix C for information on comparison values.
a Sample listed only as "Rainwater" with no other information<
b The -- indicates no data available
c ND = not detected
d Please refer to Appendix C for information on comparison values.
APPENDIX C - Comparison Values
ATSDR comparison values are media-specific concentrations that are considered to be safeunder default conditions of exposure. They are used as screening values in the preliminaryidentification of site-specific "contaminants of concern". The latter term may be misinterpretedas an implication of "hazard". As ATSDR interprets the phrase, a "contaminant of concern" ismerely a site-specific chemical substance that the health assessor has selected for furtherevaluation of potential health effects. Generally, a chemical is selected as a contaminant ofconcern because its maximum concentration in air, water, or soil at the site exceeds one ofATSDR's comparison values.
However, it must be emphasized that comparison values are not thresholds of toxicity. Whileconcentrations at or below the relevant comparison value may reasonably be considered safe, itdoes not automatically follow that any environmental concentration that exceeds a comparisonvalue would be expected to produce adverse health effects. The purpose behind highlyconservative, health-based standards and guidelines is to enable health professionals to recognizeand resolve potential public health problems before they become actual health hazards. Theprobability that adverse health outcomes will actually occur depends on site-specific conditionsand individual lifestyle and genetic factors that affect the route and duration of actual exposure,and not on environmental concentrations alone.
Listed and described below are the various comparison values that ATSDR uses to select chemicals for further evaluation, along with the abbreviations for the most common units of measure.
| CREG | = Cancer Risk Evaluation Guides |
|---|---|
| MRL | = Minimal Risk Level |
| EMEG | = Environmental Media Evaluation Guides |
| IEMEG | = Intermediate Environmental Media Evaluation Guides |
| RMEG | = Reference Dose Media Evaluation Guide |
| RfD | = Reference Dose |
| RfC | = Reference Concentration |
| RBC | = Risk-Based Concentrations (RBC) |
| EPA III | = EPA Region III |
| DWEL | = Drinking Water Equivalent Level |
| LTHA | = Drinking Water Lifetime Health Advisory |
| MCL | = Maximum Contaminant Level |
| PRG | = Permissible Remediation Goal (Action Level) |
| PEL | = Permissible Exposure Limit |
| TLV | = Threshold Limit Value |
| AWQC | = Ambient Water Quality Criteria |
| ppm | = parts per million (mg/L water or mg/kg soil) |
| ppb | = parts per billion (ug/L water or ug/kg soil) |
| kg | = kilogram (1,000 grams) |
| mg | = milligram (0.001 grams) |
| ug | = microgram (0.000001 grams) |
| L | = liter |
| m3 | = cubic meter (used in reference to a volume of air equal to 1,000 liters) |
Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations expectedto cause no more than one excess cancer in a million persons exposed over a lifetime. CREGsare calculated from EPA's cancer slope factors.
Minimal Risk Levels (MRL) are estimates of daily human exposure to a chemical (i.e., dosesexpressed in mg/kg/day) that are unlikely to be associated with any appreciable risk ofdeleterious noncancer effects over a specified duration of exposure. MRLs are calculated usingdata from human and animal studies and are reported for acute (< 14 days), intermediate (15-364days), and chronic (> 365 days) exposures. MRLs are published in ATSDR ToxicologicalProfiles for specific chemicals.
Environmental Media Evaluation Guides (EMEGs) are concentrations that are calculatedfrom ATSDR minimal risk levels by factoring in default body weights and ingestion rates.
Intermediate Environmental Media Evaluation Guides (IEMEG) are calculated fromATSDR minimal risk levels; they factor in body weight and ingestion rates for intermediateexposures (i.e., those occurring for more than 14 days and less than 1 year).
Reference Dose Media Evaluation Guide (RMEG) is the concentration of a contaminant in air,water or soil that corresponds to EPA's RfD for that contaminant when default values for bodyweight and intake rates are taken into account.
EPA's Reference Dose (RfD) is an estimate of the daily exposure to a contaminant unlikely tocause noncarcinogenic adverse health effects. Like ATSDR's MRL, EPA's RfD is a doseexpressed in mg/kg/day.
Reference Concentrations (RfC) are concentrations derived from an EPA Reference Dose withassumed body and ingestion rates factored into the calculation.
Risk-Based Concentrations (RBC) are media-specific concentrations derived by Region III ofthe Environmental Protection Agency from RfDs, RfCs, or EPA's cancer slope factors. Theyrepresent concentration of contaminants in tap water, ambient air, fish, or soil (industrial orresidential) that are considered unlikely to cause adverse health effects over a lifetime of chronicexposure. RBCs are based either on cancer ("c") or non-cancer ("n") effects.
Environmental Protection Agency Region III (EPA III) values are risk-based concentrationswhich take into account factors such as body weight, toxicity, and exposure duration andfrequency for non-carcinogens and carcinogens, when applicable.
Drinking Water Equivalent Levels (DWEL) are based on EPA's oral RfD and representcorresponding concentrations of a substance in drinking water that are estimated to havenegligible deleterious effects in humans at an intake rate of 2 L/day, assuming that drinkingwater is the sole source of exposure.
Lifetime Health Advisories (LTHA) are calculated from the DWEL and represents theconcentration of a substance in drinking water estimated to have negligible deleterious effects inhumans over a lifetime of 70 years, assuming 2 L/day water consumption for a 70-kg adult, andtaking into account other sources of exposure. In the absence of chemical-specific data, theassumed fraction of total intake from drinking water is 20%. Lifetime health advisories are notderived for compounds which are potentially carcinogenic for humans.
Maximum Contaminant Levels (MCLs) represent contaminant concentrations in drinkingwater that EPA deems protective of public health (considering the availability and economics ofwater treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water perday (for an adult).
Secondary Maximum Contaminant Levels (sMCLs) are EPA drinking water standardsbased solely on the aesthetic qualities (e.g., taste, color) of the water.
Permissible Remediation Goal (PRG) are levels set by EPA under Superfund that trigger aresponse or action when the contaminant concentration exceeds this value. Also genericallyknown as action levels.
Occupational Safety and Health Administration's Permissible Exposure Limit (PEL) for airis an 8-hour, time-weighted average developed for the workplace. The level of exposure may beexceeded (for brief periods), but the sum of the exposure levels averaged over 8 hours must notexceed the limit.
Threshold Limit Value (TLV), according to the American Conference of GovernmentalIndustrial Hygienists (ACGIH), is "the time-weighted average concentrations for a normal 8-hourworkday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, dayafter day, without adverse effect". Many of ACGIH's TLVs were adopted by OSHA for use asPELs. TLVs and PELs, which were designed to protect healthy workers, are usually muchhigher than the health-based values of ATSDR and EPA, which were designed to protect thehealth of the general population, including the very young and the elderly. Although the ATSDRdoes not base any of its community health decisions on TLVs or PELs, agency health assessorsand toxicologists may sometimes mention such values in Public Health Assessments orconsultations as a means of putting site-specific concentrations of contaminants into some kindof meaningful perspective for the reader.
Ambient Water Quality Criteria (AWQC) are clean water standards established under theClean Water Act. Separate criteria are established for humans and for aquatic organisms. Twotypes of Ambient Water Quality Criteria are established for humans: one based on consumptionof fish alone and another based on both the water and fish living in that water.
Reference
Agency for Toxic Substances and Disease Registry. Health Assessment Guidance Manual.Atlanta: ATSDR, March, 1992.
