PUBLIC HEALTH ASSESSMENT
GEIGY CHEMICAL CORPORATION SITE
[a/k/a GEIGY CHEMICAL CORPORATION (ABERDEEN PLANT)]
ABERDEEN, MOORE COUNTY, NORTH CAROLINA
APPENDIX B: GEIGY SITE HISTORY
| Date | Site-Related Event |
| 1948-1955 | Geigy Chemical Corporation operated a pesticide formulation facility. |
| 1956-1967 | Olin-Mathieson Chemical Corporation operated a pesticide formulation facility on the site. |
| 1967-1989 | Site operated by various distributors of agricultural chemicals. |
| March 1986 | Town of Aberdeen closed municipal well 1 after detecting lindane at elevated concentration. |
| February 1987-March 1987 | State of North Carolina performed a preliminary site assessment and site investigation. |
| March 1988 | EPA conducted a site inspection. |
| September 1989 | The site is closed and placed on EPA's National Priorities List. |
| 1989-1992 | Remedial investigation/feasibility study conducted. |
| 1989 | In an EPA-approved plan, GSX Services (for Olin Corporation, Ciba-Geigy Corporation, and Kaiser Aluminum Chemical Company) removed 462 tons of soil and debris, clearing areas of soil that appeared to be contaminated. |
| March 1991-April 1991 | The companies conducted a second EPA-approved removal using EPA interim removal levels. Warehouse structures and the pump house were removed; the remaining concrete foundation was steam cleaned; and 2,841 tons of soil and debris were removed. |
| January 1992 | Town of Aberdeen closed municipal well 4, the well closest to the Geigy site. |
| August 1992 | EPA issued a record of decision for the site. To further define the extent of contamination, the decision called for further excavation of contaminated soil; groundwater treatment through a carbon desorption process; and continued groundwater sampling. |
| April 1993 | The three responsible parties entered into a Consent Decree with EPA, agreeing to clean up the remaining impacted soil and groundwater at the site. |
| December 1993- March 1994 | Companies conduct field investigation activities. |
| 1995 | Three-phase downgradient groundwater investigation conducted. Companies sample for 21 pesticide-related compounds, and initiate remedial design. |
| March 1996 | EPA and the NCDEHNR approve the Geigy site remediation plan. |
| September1996-December 1996 | Remedial action completed: Contaminated soil was excavated (4,475 tons) and remainder of concrete foundations demolished. 2,460 tons of debris was removed to solid waste landfill. Seven extraction wells were installed (4 in the Surficial Aquifer and 3 in the Upper Black Creek Aquifer). Six monitoring wells were installed. A groundwater treatment facility was constructed and an infiltration gallery built for discharge of treated groundwater. |
| January 1997 | Groundwater extraction and treatment system began operating. |
| November 1997 | Downgradient groundwater remedial action work plan was finalized. |
| January 1998 | EPA issued an Explanation of Significant Difference to the groundwater remedial action workplan to include installation of additional monitoring wells. |
| April 1998 | Installation of additional monitoring wells was completed. |
APPENDIX C: DESCRIPTION OF EVALUATION PROCESS
Selection of Contaminants for Public Health Significance Evaluation
ATSDR reviews contaminant data and selects those that warrant subsequent further evaluation for public health significance. Contaminant selection considers the following factors:
ATSDR summarized all monitoring data for the Geigy site, and considered how people might come into contact with contaminants in each environmental medium, or pathway. Exposure pathway information is essential to determining public health hazards because, for any given chemical, exposure concerns vary according to the route of exposure and the concentrations of contaminants. A pathway analysis considers five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and a receptor population. When all five elements are evident, a pathway is considered complete. Appendices E and F contain exposure pathway and environmental data tables, respectively.
ATSDR evaluates environmental data by comparing contaminant concentrations to health-based comparison values (CVs). Comparison values are derived from available scientific literature on exposure and health effects. These values, which are derived for each of the different media, reflect the estimated contaminant concentration for a given chemical that is not likely to cause adverse health effects, given a standard daily intake rate and standard body weight. If contaminant concentrations are above comparison values, ATSDR further analyzes site-specific exposures and reviews the toxicity of the contaminant to determine if the exposures are of health concern.
It is important to understand that comparison values are not thresholds of toxicity. While concentrations at or below the relevant comparison value may be considered safe, it does not necessarily follow that any concentration that exceeds a comparison value would be expected to produce adverse health effects. To the contrary, ATSDR's comparison values are designed to be lower, usually orders of magnitude lower, than the corresponding no-effect levels (or lowest-effect levels) determined in laboratory studies. Further information about comparison values is available in Appendix H.
Determination of Public Health Implications
This section of the health assessment focuses on estimating how much of the pesticides people might have been exposed to daily and how that estimated dosage compares to doses that may produce health effects in the community. Because many uncertainties exist when making these estimations (e.g., lack of knowledge of how long people were exposed), ATSDR tends to use what are called "conservative" assumptions about possible exposures and associated health effects. To make a conservative estimate, ATSDR usually assumes a person is exposed to the most contaminated well water reasonably possible. This allows ATSDR to determine the highest possible level to which people may have been exposed and the corresponding health effects. Although ATSDR does not expect that most people in the Aberdeen area were exposed to the highest (most conservative) levels of contamination, the conservative estimates are used to protect public health.
While the relative toxicity of a chemical is important, the response of the human body to a chemical exposure is also determined by several additional factors, including the concentration (how much), the duration of exposure (how long), and the route of exposure (breathing, drinking, or skin contact). The probability that exposure-related adverse health outcomes will actually occur does not depend solely on concentrations in the water. Instead, the combination of all of the factors helps ATSDR to evaluate how individuals may be affected by chemical exposures.
Based on available scientific data, much of which ATSDR has collected in its toxicological profiles, ATSDR has determined concentrations of chemicals that can reasonably (and conservatively) be regarded as harmless, assuming default conditions of exposure. The resulting comparison values (see Appendix H) and health guidelines generally include safety factors believed to be sufficient to ensure protection of sensitive populations. The values are used to screen contaminant concentrations at a site, and to select contaminants that warrant closer scrutiny by agency health assessors and toxicologists. These are called "contaminants of concern." A "contaminant of concern" is defined as any substance that is detected in air, water, or soil at concentrations that exceed one or more of ATSDR's comparison values.
It must be emphasized, however, that ATSDR's comparison values and health guidelines and other comparison values, such as drinking water standards, are not thresholds of toxicity. While concentrations at or below the relevant comparison value may reasonably be considered safe, it does not necessarily follow that any concentration that exceeds a comparison value would be expected to produce adverse health effects in the community. Conservative, health-based standards and guidelines are derived to enable health professionals to recognize and resolve potential public health problems before that potential is realized. While the levels of lindane detected in municipal wells exceeded ATSDR's Intermediate EMEG, for example, it is important to understand that EMEGs are often at levels much lower than the levels at which adverse effects are seen in experimental studies. The purpose of this public health assessment is to evaluate whether exposures to detected contaminant levels, under site-specific conditions, are expected to affect the health of Aberdeen residents.
APPENDIX D: FURTHER INFORMATION ON GROUNDWATER AND SOIL SAMPLING
Groundwater Sampling of Monitoring Wells
Description of Aquifers
Three aquifers lie beneath the Geigy site (Rust, 1995). The uppermost aquifer (Surficial Aquifer) lies 35 to 45 feet underground and receives rainfall infiltration from the surface. The second uppermost aquifer (Black Creek Aquifer) is divided into two distinct units, the Upper Black Creek Aquifer and the Lower Black Creek Aquifer, and is located approximately 50 to 90 feet underground. The third uppermost aquifer (Upper Cape Fear Aquifer) directly overlies the crystalline bedrock. This aquifer has not been impacted by the site (Rust, 1995a).
The second uppermost aquifer is the primary source of drinking water in the Aberdeen area. Most residential drinking wells are between 100 and 200 feet deep and therefore below the uppermost aquifer, which is the most susceptible to contamination (Sirrine, 1992). Municipal wells are 120-300 feet deep (Monroe, 1998).
Beneath the Geigy site, the Upper Black Creek Aquifer is not hydraulically connected to the Surficial Aquifer (Sirrine, 1992). Approximately 250 to 350 feet south of the site, however, the aquifers intermingle in a recharge zone (Rust, 1996). At this location, pesticides in the Surficial Aquifer have been shown to migrate to the Upper Black Creek Aquifer.
Water in the uppermost aquifer flows primarily from the eastern and western portions of the site and meets in a "zone of convergence" in the interior (Rust, 1995a).Downgradient groundwater flow in the Upper Black Creek Aquifer is primarily to the west-southwest (Rust, 1996). Groundwater also flows vertically downward from the Upper Black Creek Aquifer to the Lower Black Creek Aquifer in the recharge zone west of the site. Groundwater flow in the Lower Black Creek Aquifer is primarily to the west and northwest (Rust, 1996).
Environmental Sampling/Analyses
In November 1990 and July 1991, EPA conducted groundwater sampling
as part of the remedial investigation (Sirrine, 1992). The remedial investigation
focused primarily on the Surficial Aquifer beneath the site (Rust, 1996). In
1990, six wells were monitored on-site in the Surficial Aquifer (MW-1S through
MW-6S), three in the Black Creek Aquifer (MW-1D, MW-4D, MW-6D), and one in the
Cape Fear Aquifer. In 1991, nine wells were monitored off site, downgradient
from the on-site monitoring wells. Six were installed in the Surficial Aquifer
(MW-7S through MW-10S, MW-12S, and MW-13S) and three in the Black Creek Aquifer
(MW-11D, MW-14D, and MW-15D). Samples were also collected from two private wells
and a USGS well in the vicinity of Municipal Well Number 4 (USGS-02-3) Pesticides
were the only chemicals found in significant concentrations in the Surficial
Aquifer. The most prevalent pesticides were BHC isomers (alpha, beta, gamma,
and delta), which were found at maximum concentrations up to 30 ppb in monitoring
wells (Sirrine, 1992). Toxaphene was also detected (See Table 3 in Appendix F).
Although pesticides were not detected in either the Black Creek or the Cape Fear aquifers directly beneath the site, they were detected off site in the Black Creek Aquifer in monitoring well MW-11D, which is 375 feet south of the site. Pesticides were not detected in the USGS shallow well near Municipal Well Number 4 (Sirrine, 1992).
In 1993, Rust sampled from the Surficial and Upper Black Creek Aquifers for the pre-remedial design field investigation (See Tables 3 and 4 in Appendix D). BHC isomers, heptachlor epoxide, and DDD were detected in the Upper Black Creek Aquifer at levels exceeding comparison values. During this investigation, Rust determined that pesticides were entering the Upper Black Creek Aquifer along a zone of groundwater recharge located approximately 250 to 350 feet south of the facility property in the vicinity of monitoring well 11D (Rust, 1996).
To further characterize the downgradient extent of pesticide contamination, in 1995 Rust collected samples from the Upper and Lower Black Creek aquifers. From this investigation Rust determined that the pesticide contamination in the Upper Black Creek Aquifer was limited to the area south of Route 211, and that groundwater discharge to the eastern portion of McFarland's Branch was controlling the extent of this contamination. Rust also determined that the contamination in the Lower Black Creek Aquifer was primarily limited to the area where the aquifers mixed, and that groundwater discharge to portions of Aberdeen and Ray's Mill creeks was preventing further migration of this contamination (Rust, 1996).
Soil Monitoring
In 1987 EPA collected on-site and off-site soil samples. Based on the results of this initial soil sampling, the companies removed more than 3,000 tons of soil in two separate actions between 1989 and 1991. EPA collected additional soil samples to assess the effectiveness of this soil remediation. The maximum values of the pesticides detected in surface soil from these two investigations are presented in Table 6 in Appendix F.
Aldrin, BHC isomers, chlordane , DDT and its metabolites (DDD and DDE), dieldrin, and toxaphene were detected at levels exceeding comparison values in both on-site and off-site soil samples. Aldrin and toxaphene levels exceeded both child and adult comparison values (chronic EMEGs) in off-site soils, while alpha-BHC, beta-BHC, DDT, and dieldrin exceeded CREG comparison values. Chlordane exceeded the child chronic EMEG in on-site soil. Generally the highest levels of pesticides were found on the site, southeast of former warehouse A (Sirrine, 1992).
In 1995 Rust sampled off-site soils to delineate the extent of contamination north of Route 211 (Rust, 1995b). The levels of pesticides detected were lower than what had been detected previously.
In 1996, the companies removed an additional 4,475 tons of contaminated soil, both on and off site. Rust conducted soil sampling again in September 1996 to verify that this soil remediation had achieved its goals. The results of this sampling effort indicated that the remediation reduced pesticide contamination in surface soils to EPA performance standards. These performance standards are generally greater than or within one order of magnitude of ATSDR Comparison Values (See Appendix G). However, while the statistical analysis showed that the site had attained the clean-up goals, some individual samples exceeded a few of the performance standards. This was particularly true of toxaphene. The highest concentrations were generally found in the immediate vicinity of culverts and drainage features. At the request of the North Carolina Department of Health and Natural Resources, the companies excavated an additional 129 cubic yards of surface soils (Rust, 1997b).
APPENDIX E: EXPOSURE PATHWAY TABLE FOR THE GEIGY CHEMICAL CORPORATION SITE
| PATHWAY NAME | SOURCE | MEDIA | POINT OF EXPOSURE | ROUTE OF EXPOSURE | RECEPTOR POPULATION | TIME | CONTAMINANTS OF CONCERN |
| Groundwater | pesticide blending facility | ground-water | public and private wells | ingestion dermal contact inhalation |
private well users and residents supplied with water from municipal wells 1 and 4 | past | Public well data alpha-BHC beta-BHC lindane Private well data |
| Surface soil | pesticide blending facility | soil | on site and off site |
incidental ingestion dermal contact |
on-site workers nearby residents |
past | aldrin chlordane DDT toxaphene |
| Air | pesticide blending facility | air | Aberdeen | inhalation | Aberdeen residents | past | unknown |
APPENDIX F: EXPOSURE DATA TABLES
TABLE 1. GEIGY MUNICIPAL WELL DATA
| Chemical | Maximum Concentration Detected (ppb) |
Date of Maximum Concentration | Location of Maximum Concentration | Comparison Value (ppb) |
Comparison Value Reference |
| alpha-BHC | 2.9 | 3/23/87 | MUW-04 | 100
400 0.006 |
Child EMEG (I)
Adult EMEG (I) CREG |
| beta-BHC | 4.9 | 3/23/87 | MUW-01 | 6
20 0.02 |
Child EMEG (I)
Adult EMEG (I) CREG |
| gamma-BHC | 17 11.6 0.8 (n = 4) |
3/23/87 | MUW-01 MUW-01 (after closing) tap water hydrant |
0.1 0.4 |
Child EMEG (I) Adult EMEG (I) |
CREG = cancer risk evaluation guide
EMEG (I) = intermediate environmental media evaluation guide
MUW = municipal well
n = number of samples
ppb = parts per billion
RMEG = ATSDR's reference dose media evaluation guide
Source: NUS, 1988; ERT, 1987
TABLE 2: GEIGY PRIVATE WELL DATA--UNTREATED WATER
| Chemical | Maximum Concentration Detected (ppb) |
Date of Maximum Concentration | Location of Maximum Concentration | Comparison Value
(CV) (ppb) |
Comparison Value Reference |
| alpha-BHC | 6.4 | 5/12/95 | PW-17 | 100 400 0.006 |
Child EMEG (I) Adult EMEG (I) CREG |
| beta-BHC | 12 | 5/12/95 | PW-17 | 6 20 0.02 |
Child EMEG (I) Adult EMEG (I) CREG |
| delta-BHC | 4.6 | 5/12/95 | PW-17 | NA | -- |
| gamma-BHC | 6.5 | 5/12/95 | PW-17 | 0.1 0.4 |
Child EMEG (I) Adult EMEG (I) |
| gamma-chlordane | 0.0056 <0.25 |
5/3/94 7/15/96 |
PW-14 PW-14 |
6* 20* 0.03* |
Child EMEG (C) Adult EMEG (C) CREG |
| 4,4'-DDD | 0.0089 <0.25 |
7/20/94 7/15/96 |
PW-14 PW-14 |
0.1 | CREG |
| 4,4'-DDE | 0.0077 <0.25 |
7/20/94 7/15/96 |
PW-14 PW-14 |
0.1 | CREG |
| 4,4'-DDT | 0.0051 <0.25 |
5/3/94 7/15/96 |
PW-14 PW-14 |
5 20 0.1 |
Child RMEG Adult RMEG CREG |
| dieldrin | 0.13 | 4/11/95 | PW-17 | 0.5 2 0.002 |
Child EMEG (C) Adult EMEG (C) CREG |
| heptachlor epoxide | <0.25 | 7/15/96 | PW-14 | 0.1 0.5 0.004 |
Child RMEG Adult RMEG CREG |
* the comparison value used for gamma-chlordane is the comparison
value for chlordane (isomer not specified)
CREG = cancer risk evaluation guide
EMEG (C) = chronic environmental media evaluation guide
EMEG (I) = intermediate environmental media evaluation
guide
NA = not available
ppb = parts per billion
PW = private well
RMEG = ATSDR's reference dose media evaluation guide
SOURCES: Environmental Response Team, 1987: Geigy, 1996; NUS, 1988.
TABLE 3: GEIGY SURFICIAL AQUIFER MONITORING WELL DATA
| Chemical | Maximum Concentration Detected (ppb) |
Date of Maximum Concentration | Location of Maximum Concentration | Comparison Value (ppb) |
Comparison Value Reference |
| aldrin | 0.54 J | 12/9/93 | MW-5S | 0.3 1 0.002 |
Child EMEG (C) Adult EMEG (C) CREG |
| alpha-BHC | 36 | 11/90 | MW-6S | 100 400 0.006 |
Child EMEG (I) Adult EMEG (I) CREG |
| beta-BHC | 25 | 7/91 | MW-10S | 6 20 0.02 |
Child EMEG (I) Adult EMEG (I) CREG |
| delta-BHC | 29 | 12/9/93 | MW-6S | NA | -- |
| gamma-BHC | 30 | 11/90 | MW-6S | 0.1 0.4 |
Child EMEG (I) Adult EMEG (I) |
| chlordane | 10 U | 12/9/93 | MW-5S, MW-6S, MW-10S | 6 20 0.03 |
Child EMEG (C) Adult EMEG (C) CREG |
| 4,4'-DDD | 2 U | 12/9/93 | MW-5S, MW-6S, MW-10S | 0.1 | CREG |
| 4,4'-DDE | 0.73 J | 12/9/93 | MW-10S | 0.1 | CREG |
| 4,4'-DDT | 2 U | 12/9/93 | MW-5S, MW-6S, MW-10S | 5 20 0.1 |
Child RMEG Adult RMEG CREG |
| dieldrin | 2 | 7/91 | MW-10S | 0.5 2 0.002 |
Child EMEG (C) Adult EMEG (C) CREG |
| endrin ketone | 4 | 7/91 | MW-10S | 3* 10* |
Child RMEG Adult RMEG |
| heptachlor epoxide | 0.15 J | 12/9/93 | MW-5S | 0.1 0.5 0.004 |
Child RMEG Adult RMEG CREG |
| toxaphene | 20 U | 12/9/93 | MW-5S, MW-6S, MW-10S | 3 10 40 0.03 |
MCL Child EMEG (I) Adult EMEG (I) CREG |
* comparison value listed for endrin ketone is the comparison
value for endrin
CREG = cancer risk evaluation guide
EMEG (I) = intermediate environmental media evaluation guide
EMEG (C) = chronic environmental media evaluation guide
J = estimated value
MCL = maximum contaminant level (EPA)
MW = monitoring well
NA = not available
ppb = parts per billion
RMEG = ATSDR's reference dose media evaluation guide
U = detection limit for the contaminant; contaminant not detected at or below this level
Sources: Rust, 1995a; Sirrine, 1992
TABLE 4: GEIGY UPPER BLACK CREEK AQUIFER MONITORING WELL
DATA
| Chemical | Maximum Concentration Detected (ppb) |
Date of Maximum Concentration | Location of Maximum Concentration | Comparison Value (ppb) |
Comparison Value Reference |
| aldrin | 0.5 U 0.5 U |
12/10/93 2/26/94 |
MW-11D MW-18D |
0.3 1 0.002 |
Child EMEG (C) Adult EMEG (C) CREG |
| alpha-BHC | 6.4 u | 12/10/93 | MW-11D | 100 400 0.006 |
Child EMEG (I) Adult EMEG (I) CREG |
| beta-BHC | 7.9 | 2/26/94 | MW-18D | 6 20 0.02 |
Child EMEG (I) Adult EMEG (I) CREG |
| delta-BHC | 6.3 | 2/26/94 | MW-18D | ||
| gamma-BHC | 5.6 | 2/26/94 | MW-18D | 3 10 |
Child RMEG Adult RMEG |
| 4,4'-DDD | 1 U 1 Uu |
12/10/93 2/26/94 |
MW-11D MW-18D |
0.1 | CREG |
| 4,4'-DDE | 0.018 J <0.26 |
2/9/94 8/18/95 |
MW-17D MW-11D |
0.1 | CREG |
| 4,4'-DDT | 0.11 J | 8/18/95 | MW-18D | 5 20 0.1 |
Child RMEG Adult RMEG CREG |
| dieldrin | 0.18 | 8/18/95 | MW-18D | 0.5 2 0.002 |
Child EMEG (C) Adult EMEG (C) CREG |
| heptachlor epoxide | 0.5 U 0.5 U |
12/10/93 2/26/94 |
MW-11D MW-18D |
0.1 0.5 0.004 |
Child RMEG Adult RMEG CREG |
| methoxychlor | 5 U 5 U |
12/10/93 2/26/94 |
MW-11D MW-18D |
50 200 |
Child RMEG Adult RMEG |
| toxaphene | 10 U <10 |
12/10/93 8/18/95 |
MW-11D | 3 10 40 0.03 |
MCL Child EMEG (I) Adult EMEG (I) CREG |
Sources: Rust, 1995a; Rust, 1996
TABLE 5: GEIGY LOWER BLACK CREEK AQUIFER MONITORING WELL
DATA
| Chemical |
Maximum Concentration Detected
(ppb) |
Date of Maximum Concentration | Location of Maximum Concentration | Comparison Value (ppb) |
Comparison Value Reference |
| alpha-BHC |
6.0
|
8/15/95 | MW-27L | 100 400 0.006 |
Child EMEG (I) Adult EMEG (I) CREG |
| beta-BHC |
2.1
|
8/15/95 | MW-27L | 6 20 0.02 |
Child EMEG (I) Adult EMEG (I) CREG |
| delta-BHC |
4.9
|
8/15/95 | MW-27L | NA | -- |
| gamma-BHC |
5.0
|
8/15/95 | MW-27L | 0.1 0.4 |
Child EMEG (I) Adult EMEG (I) |
| dieldrin |
0.011 J
<0.25 UJ <0.25 |
8/15/95 | PZ-2 MW-22L MW-27L |
0.5 2 0.002 |
Child EMEG (C) Adult EMEG (C) CREG |
Source: Rust, 1996
TABLE 6: GEIGY SURFACE SOIL SAMPLES
| Chemical | Maximum Concentration Detected (ppm) |
Date of Maximum Concentration | Location of Maximum Concentration | Comparison Value (ppm) |
Comparison Value Reference |
| aldrin | 28 C 14 |
3/23/87 unknown |
off-site (SS-09) on-site (SS-06) |
2 20 0.04 |
Child EMEG (C) Adult EMEG (C) CREG |
| alpha-BHC | 0.51 2.1 |
3/23/87 unknown |
off-site (SS-11) on-site (SS-91) |
50 7,000 0.1 |
Child EMEG (I) Adult EMEG (I) CREG |
| beta-BHC | 1.1 4.1 |
3/23/87 unknown |
off-site (SS-11) on-site (SS-91) |
30 400 0.4 |
Child EMEG (I) Adult EMEG (I) CREG |
| delta-BHC | 6.4 J 1.9 |
3/23/87 unknown |
off-site (SS-09) on-site (SS-73-5) |
NA | -- |
| chlordane (tech. mixture) | 270 J, C | 3/23/87 | off-site (SS-09) | 30 400 0.5 |
Child EMEG (C) Adult EMEG (C) CREG |
| 4,4'-DDD | 28 | unknown | on-site (SS-06) | 3 | CREG |
| 4,4'-DDE | 1.1 17 J, C |
3/23/87 3/23/87 |
off-site (SS-12) on-site (SS-02) |
2 | CREG |
| 4,4'-DDT | 10 54 |
3/23/87 unknown |
off-site (SS-10) on-site (SS-06) |
30 700,000 2 |
Child RMEG Adult RMEG CREG |
| dieldrin | 0.62 9.7 |
3/23/87 unknown |
off-site (SS-10) on-site (SS-06) |
3 40 0.04 |
Child EMEG (C) Adult EMEG (C) CREG |
| toxaphene | 740 C 1,119* |
3/23/87 prior to remediation |
off-site (SS-11) on-site |
50 700 0.6 |
Child EMEG (I) Adult EMEG (I) CREG |
Sources: NUS, 1988; Rust, 1997a; Sirrine, 1992
APPENDIX G: SOIL PERFORMANCE STANDARDS
| Pesticide | EPA Soil Performance Standard (ppm) |
ATSDR Comparison Values (ppm) |
ATSDR Comparison Value Reference |
|
aldrin
|
0.113
|
2
0.04 |
Child EMEG (C)
CREG |
|
alpha-BHC
|
0.28
|
50
0.1 |
Child EMEG (I)
CREG |
|
beta-BHC
|
1.15
|
30
0.4 |
Child EMEG (I)
CREG |
|
gamma-BHC
|
1.5
|
0.5
7 |
Child EMEG (I)
Adult EMEG (I) |
|
dieldrin
|
0.13
|
3
0.04 |
Child EMEG (C)
CREG |
|
toxaphene
|
2.0
|
50
0.6 |
Child EMEG (I)
CREG |
|
DDD
|
7.6
|
3
|
CREG
|
|
DDE
|
5.5
|
2
|
CREG
|
|
DDT
|
4.75
|
2
|
CREG
|
|
gamma-chlordane
|
1.43
|
0.5
30 |
Child EMEG (C)
CREG |
|
alpha-chlordane
|
1.4
|
0.5
30 |
Child EMEG (C)
CREG |
Source: Rust, 1997a
APPENDIX H: ATSDR's 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 "contaminants of concern" at a site. The latter is, perhaps, an unfortunate term because the word "concern" may be misinterpreted as an implication of "hazard." As ATSDR uses the phrase, however, 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 cannot be emphasized strongly enough 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. Indeed, the whole 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 as a result of exposure to environmental contaminants depends on site-specific conditions and individual lifestyle and genetic factors that affect the route, magnitude, and duration of actual exposure, and not on environmental concentrations alone.
Screening values based on noncancer effects are obtained by dividing NOAELs or LOAELs determined in animal or (less often) human studies by cumulative safety margins (variously called safety factors, uncertainty factors, and modifying factors) that typically range from 10 to 1,000 or more. By contrast, cancer-based screening values are usually derived by linear extrapolation from animal data obtained at high doses, because human cancer incidence data for very low levels of exposure simply do not exist, and probably never will. In neither case can the resulting screening values (i.e., EMEGs or CREGs) be used to make realistic predictions of health risk associated with low-level exposures in humans.
Following is a list of the various comparison values that ATSDR uses to select chemicals for further evaluation, along with abbreviations for the most common units of measure. A description of the comparison values follows.
|
CREG |
= cancer risk evaluation guide |
| EMEG | = environmental media evaluation guide |
| IEMEG | = intermediate environmental media evaluation guide |
| kg | = kilogram (1,000 grams) |
| LOAEL | = lowest-observed-adverse-effect level |
| MCL | = maximum contaminant level |
| mg | = milligram (0.001 grams) |
| MRL | = minimal risk level |
| NOAEL | = no-observed-adverse-effect level |
| ppb | = parts per billion |
| ppm | = parts per million |
| RMEG | = reference dose media evaluation guide |
| µg | = microgram (0.000001 grams) |
Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations in water, soil, or air that would be 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, and cannot be used to make predictions about actual cancer incidence rates.
Environmental Media Evaluation Guides (EMEGs) are concentrations of a contaminant in water, soil, or air that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. EMEGs are derived from ATSDR minimal risk levels (MRL) by factoring in default body weights and ingestion rates. Separate EMEGS are computed for acute (<14 days), intermediate (15-364 days), and chronic (>365 days) exposures. See the definition of minimal risk levels.
Intermediate Environmental Media Evaluation Guides (IEMEG) are media-specific concentrations which correspond to a minimal risk level (MRL), factoring in body weight and ingestion rates for intermediate exposures (i.e., >14 days and <1 year).
Lowest-Observed-Adverse-Effect Level (LOAEL) is the lowest dose of chemical in a study, or group of studies, that produces statistically or biologically significant increases in frequency or severity of adverse effects between the exposed population and its appropriate control.
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.
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 derived for acute (<14 days), intermediate (15-364 days), and chronic (>365 days) exposures, and are published in ATSDR's Toxicological Profiles for specific chemicals.
No-Observed-Adverse-Effect Level (NOAEL) is the dose of chemical at which there were no statistically significant or biologically significant increases in frequency or severity of adverse effects seen between the exposed population and its appropriate control. Nonadverse effects may still be observed at this dose, but they will have no deleterious impact on the organism.
Reference Dose Media Evaluation Guide (RMEG) is the concentration of a contaminant in air, water, or soil that corresponds to EPA's reference dose of RfC for that contaminant when default values for body weight and intake rates are taken into account.
