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
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Table 1: COMPLETED EXPOSURE PATHWAYS
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| Pathway Name | Source | Environmental Medium | Point of Exposure | Route of Exposure | Exposed Pop. | Time |
| Air | Laidlaw/ ABCO |
Air | On-site Work Areas | Inhalation | Workers | Past |
| Air | Laidlaw/ ABCO |
Air | Off-site Residential Areas | Inhalation | Area Residents | Past |
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Table 2: POTENTIAL EXPOSURE PATHWAYS | ||||||
| Pathway Name | Source | Environmental Medium |
Point of Exposure | Route of Exposure | Exposed Pop. |
Time |
| Surface Water | ABCO | Surface Water | On-site Ponds | Dermal, Incidental Ingestion | Workers | Past |
| Surface Water | ABCO/ Laidlaw |
Surface Water | Off-site Unnamed Tributary | Dermal, Incidental Ingestion | Area Residents | Past, Current, Future |
| Groundwater | ABCO Ponds/ Spills |
Private Groundwater Wells |
Off-site Private Wells | Inhalation, Ingestion, Dermal | Area Residents | Future |
| Soil | ABCO/ Laidlaw |
Soil | On-site Shallow and Deep Soil | Dermal | Workers | Past |
| Sediment | ABCO/ Laidlaw |
Sediment | Off-site Sediment | Dermal, Incidental Ingestion |
Area Residents | Past Current Future |
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Table 3: Groundwater Sampling Results -- Organics
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| Contaminant | Concentration Range (ppb) |
Year of Max. |
Comparison Valuea
|
|
| Value (ppb) | Source | |||
| Benzene | 0.3 - 15 | 1987 | 5 | MCL |
| Bromodichloromethane | 0.5 - 5.6 | 1995 | 200 | Chronic EMEG (child) |
| Bromoform | 1.0 - 99 | 1988 | 2,000 | Chronic EMEG (child) |
| Carbon Tetrachloride | 0.5 - 851 | 1987 | 5 | MCL |
| Chloroethane | 1.0 | 1992 | 8,600 | RBC (n) |
| Chloroform | 0.6 - 180 | 1991 | 100 | Chronic EMEG (child) |
| Chloromethane | 5.8 | 1989 | 3 | LTHA |
| Chloromethlymethyl ether | 14 - 86 | 1994 | 0.00184 | AWQC (10-6 cancer risk level) |
| Dibromochloromethane | 1.2 - 2.7 | 1987 | 300 | Chronic EMEG (child) |
| Dibromomethane | 2 - 12 | 1989 | (See Bromoform above) | (Methylene Bromide is less toxic than Bromoform.) |
| 1,1-Dichloroethane | 0.5 - 20 | 1991 | 810 | RBC (n) |
| 1,2-Dichloroethane | 0.6 - 61,300 | 1990 | 5 | MCL |
| 1,1-Dichloroethene | 0.51 - 103 | 1991 | 7 | MCL |
| 1,2-Dichloroethene, total | 0.7 - 1,400 | 1995 | 70 (cis) 100 (trans) |
LTHA |
| 1,4-Dioxane | 124 | 1990 | 3 | CREG |
| Heptachlor | 0.08 | 1991 | 0.4 | MCL |
| Methylene Chloride | 0.1 - 232 | 1992 | 5 | MCL |
| 1,1,2,2-Tetrachloroethane | 1.2 - 1,013 | 1992 | 3,000 | Chronic EMEG (child) |
| Tetrachloroethene | 1.0 - 3,900 | 1995 | 5 | MCL |
| 1,1,1-Trichloroethane | 0.7 - 817 | 1987 | 200 | LTHA / MCL |
| Trichloroethene | 0.5 - 610 | 1995 | 5 | MCL |
| Vinyl Chloride | 0.5 - 3.0 | 1995 | 2 | MCL |
a Please refer to Appendix C for information on comparison values.
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Table 4: Groundwater Sampling Results -- Inorganics
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| Contaminant | Concentration Range (ppb) |
Year of Max. | Comparison Valuea | |
| Value (ppb) | Source | |||
| Arsenic | 0.5 - 125 | 1990 | 50 | MCL |
| Barium | 100 - 50,000 | unknown | 2,000 | MCL |
| Cadmium | 4 - 18 | 1994 | 5 | MCL |
| Chloride | 1,000 - 1,596,000 | 1988 | 250,000 | sMCL |
| Chromium | 10 - 420 | 1990 | 100 | LTHA / MCL |
| Iron | 910 - 163,000 | 1994 | 300 | sMCL |
| Lead | 2 - 840 | 1990 | 15 | Action Level |
| Manganese | 28 - 4,410 | 1994 | 50 | RMEG (child) |
| Mercury (inorganic) | 0.2 - 3.9 | 1991 | 11 | RBC (n) |
| Nickel | 21 - 360 | 1993 | 100 | LTHA / MCL |
| Sodium | 1,200 - 699,000 | 1989 | 20,000 | DWEL |
| Sulfate | 1,000 - 48,000 | 1993 | 250 | sMCL |
a Please refer to Appendix C for information on comparison values.
| Table 5: Off-site Air Sampling Results for 1986-1989 -- Organics | ||||||
| Contaminant | Concentration (ug/m3) Cromer |
Concentration (ug/m3) Pecan |
Concentration (ug/m3) Parklane (background) |
Concentration (ug/m3) Cromer |
Concentration (ug/m3) Pecan |
Comparison Valuea (ug/m3) |
| 24 hour | Episodic | |||||
| Acenapthene | 0.030 | 0 | --b | 0.020 | 0 | 220 RBC (N) |
| Acenapthylene | 0 | 0 | -- | 0.020 | 0 | 220 RBC (N) |
| Anthracene | 0.006 | 0 | -- | 0.010 | 0 | 1,100 RBC (N) |
| Benzoic Acid | 0.116 | 0.130 | -- | 2.990 | 0 | 15,000 RBC (N) |
| Benzothiazole | 0.080 | 0 | 0.016 | 68.910 | -- | NONE |
| Bis(2-ethylhexyl)phthalate | 0 | 0.011 | -- | 0.040 | 0.020 | 0.45 RBC (C) |
| Butyl benzene | -- | -- | -- | 0.015 | -- | 37 RBC (N) |
| Butyl benzyl phthalate | 0.030 | 0 | -- | 0 | 0 | 730 RBC (N) |
| Caprolactan | 0.158 | 0.203 | 0.096 | 6.105 | -- | 1,800 RBC (N) |
| Chrysene | 0.005 | 0 | -- | 0 | 0 | 1.0 RBC (C) |
| Decane | 0.353 | 0.323 | -- | 0.300 | 1.798 | NONE |
| Undecane | 0.598 | 0.250 | -- | 0.290 | 1.804 | NONE |
| Dodecane | 0.238 | 0.123 | -- | 0.150 | 0.575 | NONE |
| Tetradecane | 0.110 | 0.071 | -- | 0.040 | 0.312 | NONE |
| Hexadecane | 0.052 | 0.023 | -- | 0.020 | 0.304 | NONE |
| Octadecane | 0.038 | 0.009 | -- | 0.005 | 0 | NONE |
| Eicosane | 0.043 | 0 | -- | 0 | 0 | NONE |
| Docosane | 0.018 | 0 | -- | 0 | 0 | NONE |
| Tetracosane | 0.005 | 0 | -- | 0 | 0 | NONE |
| Dibenzofuran | 0.030 | 0.006 | -- | 0.030 | 0 | 15 RBC (N) |
| 1,2-Dichlorobenzene | 0.005 | 0.005 | 0.007 | 1.842 | 0 | 150 RBC (N) |
| 1,3-Dichlorobenzene | 0 | 0 | 0 | 0.491 | 0.429 | 320 RBC (N) |
| Diethyl phthalate | 0.005 | 0 | -- | 0 | 0 | 2,900 RBC (N) |
| 1,2-Dimethyl benzene
(o-xylene) |
0.457 | 0.181 | 0.104 | 27.780 | -- | 730 RBC (N) |
| 1,3/1,4-Dimethyl benzene
(m/p xylene) |
1.464 | 0.207 | 0.250 | 70.310 | 0 | 730/310 RBC (N) |
| Dimethyl phthalate | 0.087 | 0.005 | 0 | 0.029 | 0 | 37,000 RBC (N) |
| Di-n-butyl phthalate | 0.006 | 0 | -- | 0 | 0 | 370 RBC (N) |
| 4-Ethyl benzaldehyde | 1.171 | 0 | 0.090 | 0 | -- | NONE |
| 2-Ethyl hexanoic Acid | 0 | 0 | 0 | 2.941 | -- | NONE |
| 4-Ethyl hexanoic Acid
(Ethyl Caproate or Ethyl Hexanoic Acid) |
-- | -- | -- | 0.345 | -- | NONE |
| Fluoranthene | 0.007 | 0 | -- | 0 | 0 | 150 RBC (N) |
| Fluorene | 0.026 | 0 | -- | 0.020 | 0 | 150 RBC (N) |
| Indene | 0.123 | 0 | 0 | 0.943 | -- | 48,000 TLV |
| Isopropyl toluene
(p-Cymene) |
-- | -- | -- | 0.050 | -- | NONE |
| Methyl benzene
(toluene) |
-- | -- | -- | 0.420 | -- | 420 RBC (N) |
| 2-Methyl naphthalene | 0.179 | 0.070 | -- | 0.160 | 0.697 | NONE |
| 2-Methyl phenol
(o-Cresol) |
0.022 | 0 | -- | 0.080 | 0 | 180 RBC (N) |
| 4-Methyl phenol
(p-Cresol) |
0.005 | 0.008 | -- | 0.130 | 0 | 18 RBC (N) |
| Naphthalene c | 2.543 | 0.310 | 0.722 | 181.800 | 1.562 | 150 RBC (N)
CREG=10 |
| Nitrobenzene | 0.018 | 0 | -- | 0 | 0 | 2.1 RBC (N) |
| 2-Nitrophenol | 0.007 | 0.023 | -- | 0.070 | 0 | NONE |
| 4-Nitrophenol | 0 | 0 | -- | 0.010 | 0 | 230 RBC (N) most toxic isomer |
| Nonanal | 0.399 | 0.127 | 0.129 | 22.890 | -- | NONE |
| Nonane | 0.581 | 0.227 | 0.116 | 19.040 | 1.107 | 1,050,000 TLV |
| Octanal | 0.133 | 0.033 | 0.037 | 5.652 | -- | NONE |
| Pentachlorophenol | 0.009 | 0 | -- | 0 | 0 | 0.052 RBC (C) |
| Phenanthrene | 0.035 | 0 | -- | 0.030 | 0 | mouse LD50=700 mg/kg |
| Phenol | 0.036 | 0.010 | -- | 0.120 | 0 | 2,200 RBC (N) |
| alpha Pinene | 0.143 | 0.410 | 0.099 | 7.412 | -- | NONE |
| beta Pinene | 0.125 | 0.415 | 0.072 | 7.089 | -- | NONE |
| Pyrene | 0.005 | 0 | -- | 0 | 0 | 110 RBC (N) |
| 1,2,4-Trichlorobenzene | 0.022 | 0.026 | -- | 0.020 | 0 | 210 RBC (N) |
| 1,2,4-Trimethylbenzene | 1.131 | 0.380 | 0.650 | 97.250 | -- | 180 RBC (N) |
| 1,3,5-Trimethylbenzene | -- | -- | -- | 0.190 | -- | 180 RBC (N) |
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.
| Table 6: Off-site Air Sampling Results for 1986-1989 -- Inorganics | ||||
| Contaminant | Concentration (ug/m3) Cromer |
Concentration (ug/m3) Pecan |
Concentration (ug/m3) Parklane (background) |
Comparison Valuea (ug/m3) |
| Arsenic | 0.00298 | --b | 0.00163 | 0.0002 CREGc 1.1 RBC(N) |
| Copper | 0.280 | 0.695 | 0.164 | 150 RBC(N) |
| Iron | 1.110 | 0.930 | 0.520 | 1,100 RBC(N) |
| Lead | 0.101 | 0.270 | 0.123 | 1.5 NAAQS |
| Magnesium | 0.293 | 0.303 | 0.680 | essential nutrient (high doses cause metal fume fever) |
| Nickel | 0.029 | 0.025 | 0.064 | 73 RBC(N) 0.004 CREG (for Ni subsulfidec) |
| Selenium | 0.00126 | -- | 0.000400 | 18 RBC(N) |
| Zinc | 0.127 | 0.309 | 0.411 | 1,100 RBC(N) |
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.
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| Contaminant |
Concentration (mg/kg) |
Concentration (mg/kg) Deep Samples (2-47 feet) |
Concentration (mg/kg) Gas Tar Pond Soil Samples (8 feet) |
Concentration(mg/kg) Backgrounda |
Comparison Valuee | |
| Value (mg/kg) | Source | |||||
| 1,2-Dichloroethane | 80 | 7 - 344 Db | --c | BDLd | 8 | CREG |
| 105 | intermediate EMEG (adult) | |||||
| Dimethyl phthalate |
-- | -- | 0.84 | BDL | 106 | RBC (n) |
| Methylene Chloride | 7 - 13 | 6 - 128 | -- | BDL | 90 | CREG |
| 4x104 | RMEG (adult) | |||||
| 1,1,2,2-Tetrachloroethane | 22 | 6 - 14 | -- | BDL | 4 | CREG |
| 2x105 | Chronic EMEG (adult) | |||||
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.
| Table 8: On-site Soil Sampling Results for 1988-1989 -- Inorganics | ||||||
| Contaminant |
Concentration (mg/kg) |
Concentration (mg/kg) Deep Samples (2-47 feet) |
Concentration (mg/kg) Gas Tar Pond Soil Samples (8 feet) |
Concentration (mg/kg) Backgrounda |
Comparison Value e | |
| Value (mg/kg) | Source | |||||
| Aluminum | --b | -- | 58,000 - 67,000 | 49,000 | 106 | RBC (n) |
| Arsenic | <5x c | <10x | 0.7 | BDL d | 0.5 | CREG |
| 200 | Chronic EMEG (adult) | |||||
| Barium | 60 - 140 | 60 - 800 | 257 - 598 | 70 - 430 | 50,000 | RMEG (adult) |
| Cadmium | < 0.5 | 0.8 - 1.0 | -- | <0.5 | 700 | Chronic EMEG (adult) |
| Chromium | 14 - 27 | 3 - 163 | 23 - 39 | 11 - 82 | 60 | Hexavalent CREG |
| 4,000 | Hexavalent RMEG (adult) | |||||
| Copper | -- | -- | 9 - 33 | 17 | None | |
| Lead | 13 - 36 | 7 - 31 | 24 - 249 | 14 - 31 | None | |
| Magnesium | -- | -- | 4,000 - 7,000 | 2,600 | None | |
| Manganese | -- | -- | 363 - 744 | 349 | 100,000 | RMEG (adult) |
| Mercury | 0.12 - 0.41 | 0.1 - 0.37 | BDL | 0.27 | None | |
| Sodium | -- | -- | 1,300 - 15,000 | 1,200 | None | |
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.
| Table 9: On-site Pond Sampling Results for 1980-1981 | |||||
| Contaminant |
Concentration (ppb) |
Concentration (ppb) Catchment Pond |
Concentration (ppb) Rainwatera |
Comparison Valued | |
| Value (ppb) | Source | ||||
| Arsenic | 20 | --b | -- | 50 | MCL |
| Chromium | 830 - 2,600 | NDc | 30 | 100 | LTHA / MCL |
| Cobalt | 100 | -- | -- | 2,200 | RBC (n) |
| Copper | 10 - 30 | 20 | 10 | 1,300 | MCLG |
| 1,000 | sMCL | ||||
| Iron | 9,000 | -- | -- | 11,000 | RBC (n) |
| 300 | sMCL | ||||
| Lead | 50 - 310 | 100 | 140 | 15 | MCL |
| Manganese | 500 | -- | -- | 50 | RMEG (child) |
| 50 | sMCL | ||||
| Mercury | 10 | -- | -- | 11 | RBC (n) |
| Nickel | 100 - 2,960 | 110 | 120 | 100 | LTHA / MCL |
| Sodium | 1,170,000 | -- | -- | 20,000 | DWEL |
| Zinc | 40 - 210 | 50 | 220 | 2,000 | LTHA |
| 5,000 | sMCL | ||||
| Phenols | 154 - 2,000 | -- | -- | 4,000 | LTHA |
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 safe under default conditions of exposure. They are used as screening values in the preliminary identification of site-specific "contaminants of concern". The latter term may be misinterpreted as an implication of "hazard". As ATSDR interprets the phrase, a "contaminant of concern" is merely a site-specific chemical substance that the health assessor has selected for further evaluation of potential health effects. Generally, a chemical is selected as a contaminant of concern because its maximum concentration in air, water, or soil at the site exceeds one of ATSDR's comparison values.
However, it must be emphasized that comparison values are not thresholds of toxicity. While concentrations at or below the relevant comparison value may reasonably be considered safe, it does not automatically follow that any environmental concentration that exceeds a comparison value would be expected to produce adverse health effects. The purpose behind highly conservative, health-based standards and guidelines is to enable health professionals to recognize and resolve potential public health problems before they become actual health hazards. The probability that adverse health outcomes will actually occur depends on site-specific conditions and 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 expected to cause no more than one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors.
Minimal Risk Levels (MRL) are estimates of daily human exposure to a chemical (i.e., doses expressed in mg/kg/day) that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. MRLs are calculated using data from human and animal studies and are reported for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures. MRLs are published in ATSDR Toxicological Profiles for specific chemicals.
Environmental Media Evaluation Guides (EMEGs) are concentrations that are calculated from ATSDR minimal risk levels by factoring in default body weights and ingestion rates.
Intermediate Environmental Media Evaluation Guides (IEMEG) are calculated from ATSDR minimal risk levels; they factor in body weight and ingestion rates for intermediate exposures (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 body weight and intake rates are taken into account.
EPA's Reference Dose (RfD) is an estimate of the daily exposure to a contaminant unlikely to cause noncarcinogenic adverse health effects. Like ATSDR's MRL, EPA's RfD is a dose expressed in mg/kg/day.
Reference Concentrations (RfC) are concentrations derived from an EPA Reference Dose with assumed body and ingestion rates factored into the calculation.
Risk-Based Concentrations (RBC) are media-specific concentrations derived by Region III of the Environmental Protection Agency from RfDs, RfCs, or EPA's cancer slope factors. They represent concentration of contaminants in tap water, ambient air, fish, or soil (industrial or residential) that are considered unlikely to cause adverse health effects over a lifetime of chronic exposure. RBCs are based either on cancer ("c") or non-cancer ("n") effects.
Environmental Protection Agency Region III (EPA III) values are risk-based concentrations which take into account factors such as body weight, toxicity, and exposure duration and frequency for non-carcinogens and carcinogens, when applicable.
Drinking Water Equivalent Levels (DWEL) are based on EPA's oral RfD and represent corresponding concentrations of a substance in drinking water that are estimated to have negligible deleterious effects in humans at an intake rate of 2 L/day, assuming that drinking water is the sole source of exposure.
Lifetime Health Advisories (LTHA) are calculated from the DWEL and represents the concentration of a substance in drinking water estimated to have negligible deleterious effects in humans over a lifetime of 70 years, assuming 2 L/day water consumption for a 70-kg adult, and taking into account other sources of exposure. In the absence of chemical-specific data, the assumed fraction of total intake from drinking water is 20%. Lifetime health advisories are not derived for compounds which are potentially carcinogenic for humans.
Maximum Contaminant Levels (MCLs) represent contaminant concentrations in drinking water that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day (for an adult).
Secondary Maximum Contaminant Levels (sMCLs) are EPA drinking water standards based 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 a response or action when the contaminant concentration exceeds this value. Also generically known as action levels.
Occupational Safety and Health Administration's Permissible Exposure Limit (PEL) for air is an 8-hour, time-weighted average developed for the workplace. The level of exposure may be exceeded (for brief periods), but the sum of the exposure levels averaged over 8 hours must not exceed the limit.
Threshold Limit Value (TLV), according to the American Conference of Governmental Industrial Hygienists (ACGIH), is "the time-weighted average concentrations for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect". Many of ACGIH's TLVs were adopted by OSHA for use as PELs. TLVs and PELs, which were designed to protect healthy workers, are usually much higher than the health-based values of ATSDR and EPA, which were designed to protect the health of the general population, including the very young and the elderly. Although the ATSDR does not base any of its community health decisions on TLVs or PELs, agency health assessors and toxicologists may sometimes mention such values in Public Health Assessments or consultations as a means of putting site-specific concentrations of contaminants into some kind of meaningful perspective for the reader.
Ambient Water Quality Criteria (AWQC) are clean water standards established under the Clean Water Act. Separate criteria are established for humans and for aquatic organisms. Two types of Ambient Water Quality Criteria are established for humans: one based on consumption of 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.
