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PUBLIC HEALTH ASSESSMENT

GEIGY CHEMICAL CORPORATION SITE
[a/k/a GEIGY CHEMICAL CORPORATION (ABERDEEN PLANT)]
ABERDEEN, MOORE COUNTY, NORTH CAROLINA


APPENDIX A: FIGURES

Vicinity Map
Figure 1. Vicinity Map


APPENDIX B:

GEIGY SITE HISTORY
DateSite-Related Event
1948-1955Geigy Chemical Corporation operated a pesticide formulation facility.
1956-1967Olin-Mathieson Chemical Corporation operated a pesticide formulationfacility on the site.
1967-1989Site operated by various distributors of agricultural chemicals.
March 1986Town of Aberdeen closed municipal well 1 after detecting lindane atelevated concentration.
February 1987-March1987State of North Carolina performed a preliminary site assessment and siteinvestigation.
March 1988EPA conducted a site inspection.
September 1989The site is closed and placed on EPA's National Priorities List.
1989-1992Remedial investigation/feasibility study conducted.
1989In an EPA-approved plan, GSX Services (for Olin Corporation, Ciba-Geigy Corporation, and Kaiser Aluminum Chemical Company) removed462 tons of soil and debris, clearing areas of soil that appeared to becontaminated.
March 1991-April 1991The companies conducted a second EPA-approved removal using EPAinterim removal levels. Warehouse structures and the pump house wereremoved; the remaining concrete foundation was steam cleaned; and2,841 tons of soil and debris were removed.
January 1992Town of Aberdeen closed municipal well 4, the well closest to the Geigysite.
August 1992EPA issued a record of decision for the site. To further define the extentof contamination, the decision called for further excavation ofcontaminated soil; groundwater treatment through a carbon desorptionprocess; 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 thesite.
December 1993-March 1994Companies conduct field investigation activities.
1995Three-phase downgradient groundwater investigation conducted.Companies sample for 21 pesticide-related compounds, and initiateremedial design.
March 1996 EPA and the NCDEHNR approve the Geigy site remediation plan.
September1996-December 1996Remedial action completed: Contaminated soil was excavated (4,475tons) and remainder of concrete foundations demolished. 2,460 tons ofdebris was removed to solid waste landfill. Seven extraction wells wereinstalled (4 in the Surficial Aquifer and 3 in the Upper Black CreekAquifer). Six monitoring wells were installed. A groundwater treatmentfacility was constructed and an infiltration gallery built for discharge oftreated groundwater.
January 1997Groundwater extraction and treatment system began operating.
November 1997Downgradient groundwater remedial action work plan was finalized.
January 1998EPA issued an Explanation of Significant Difference to the groundwaterremedial action workplan to include installation of additional monitoringwells.
April 1998Installation 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 evaluationfor public health significance. Contaminant selection considers the following factors:

  1. Concentrations of contaminants in media
  2. Sample locations, field quality data, and laboratory data quality
  3. Relationship of concentrations to ATSDR's public health assessment comparison values; also the unavailability of suitable comparison values
  4. Community health concerns.

ATSDR summarized all monitoring data for the Geigy site, and considered how people mightcome into contact with contaminants in each environmental medium, or pathway. Exposurepathway information is essential to determining public health hazards because, for any givenchemical, exposure concerns vary according to the route of exposure and the concentrations ofcontaminants. A pathway analysis considers five elements: a source of contamination, transportthrough an environmental medium, a point of exposure, a route of human exposure, and areceptor 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-basedcomparison values (CVs). Comparison values are derived from available scientific literature onexposure 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 causeadverse health effects, given a standard daily intake rate and standard body weight. Ifcontaminant concentrations are above comparison values, ATSDR further analyzes site-specificexposures and reviews the toxicity of the contaminant to determine if the exposures are of healthconcern.

It is important to understand that comparison values are not thresholds of toxicity. Whileconcentrations at or below the relevant comparison value may be considered safe, it does notnecessarily follow that any concentration that exceeds a comparison value would be expected toproduce adverse health effects. To the contrary, ATSDR's comparison values are designed to belower, usually orders of magnitude lower, than the corresponding no-effect levels (or lowest-effect levels) determined in laboratory studies. Further information about comparison values isavailable in Appendix H.

Determination of Public Health Implications

This section of the health assessment focuses on estimating how much of the pesticides peoplemight have been exposed to daily and how that estimated dosage compares to doses that mayproduce health effects in the community. Because many uncertainties exist when making theseestimations (e.g., lack of knowledge of how long people were exposed), ATSDR tends to usewhat are called "conservative" assumptions about possible exposures and associated healtheffects. To make a conservative estimate, ATSDR usually assumes a person is exposed to themost contaminated well water reasonably possible. This allows ATSDR to determine the highestpossible 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 thehighest (most conservative) levels of contamination, the conservative estimates are used toprotect public health.

While the relative toxicity of a chemical is important, the response of the human body to achemical 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 actuallyoccur does not depend solely on concentrations in the water. Instead, the combination of all ofthe 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 toxicologicalprofiles, ATSDR has determined concentrations of chemicals that can reasonably (and conservatively) be regarded as harmless, assuming default conditions of exposure. The resultingcomparison values (see Appendix H) and health guidelines generally include safety factorsbelieved to be sufficient to ensure protection of sensitive populations. The values are used toscreen contaminant concentrations at a site, and to select contaminants that warrant closerscrutiny by agency health assessors and toxicologists. These are called "contaminants ofconcern." A "contaminant of concern" is defined as any substance that is detected in air, water, orsoil 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 andother comparison values, such as drinking water standards, are not thresholds of toxicity. Whileconcentrations at or below the relevant comparison value may reasonably be considered safe, itdoes not necessarily follow that any concentration that exceeds a comparison value would beexpected to produce adverse health effects in the community. Conservative, health-basedstandards and guidelines are derived to enable health professionals to recognize and resolvepotential public health problems before that potential is realized. While the levels of lindanedetected in municipal wells exceeded ATSDR's Intermediate EMEG, for example, it is importantto understand that EMEGs are often at levels much lower than the levels at which adverse effectsare seen in experimental studies. The purpose of this public health assessment is to evaluatewhether 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 seconduppermost aquifer (Black Creek Aquifer) is divided into two distinct units, the Upper BlackCreek Aquifer and the Lower Black Creek Aquifer, and is located approximately 50 to 90 feetunderground. The third uppermost aquifer (Upper Cape Fear Aquifer) directly overlies thecrystalline 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. Mostresidential drinking wells are between 100 and 200 feet deep and therefore below the uppermostaquifer, which is the most susceptible to contamination (Sirrine, 1992). Municipal wells are120-300 feet deep (Monroe, 1998).

Beneath the Geigy site, the Upper Black Creek Aquifer is not hydraulically connected to theSurficial Aquifer (Sirrine, 1992). Approximately 250 to 350 feet south of the site, however, theaquifers intermingle in a recharge zone (Rust, 1996). At this location, pesticides in the SurficialAquifer 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 siteand meets in a "zone of convergence" in the interior (Rust, 1995a).Downgradient groundwaterflow 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 LowerBlack Creek Aquifer in the recharge zone west of the site. Groundwater flow in the Lower BlackCreek 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 aquifersdirectly beneath the site, they were detected off site in the Black Creek Aquifer in monitoringwell MW-11D, which is 375 feet south of the site. Pesticides were not detected in the USGSshallow well near Municipal Well Number 4 (Sirrine, 1992).

In 1993, Rust sampled from the Surficial and Upper Black Creek Aquifers for the pre-remedialdesign field investigation (See Tables 3 and 4 in Appendix D). BHC isomers, heptachlorepoxide, and DDD were detected in the Upper Black Creek Aquifer at levels exceedingcomparison values. During this investigation, Rust determined that pesticides were entering theUpper Black Creek Aquifer along a zone of groundwater recharge located approximately 250 to350 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 Rustcollected samples from the Upper and Lower Black Creek aquifers. From this investigation Rustdetermined that the pesticide contamination in the Upper Black Creek Aquifer was limited to thearea south of Route 211, and that groundwater discharge to the eastern portion of McFarland'sBranch was controlling the extent of this contamination. Rust also determined that thecontamination in the Lower Black Creek Aquifer was primarily limited to the area where theaquifers mixed, and that groundwater discharge to portions of Aberdeen and Ray's Mill creekswas 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 soilsampling, the companies removed more than 3,000 tons of soil in two separate actions between1989 and 1991. EPA collected additional soil samples to assess the effectiveness of this soilremediation. The maximum values of the pesticides detected in surface soil from these twoinvestigations are presented in Table 6 in Appendix F.

Aldrin, BHC isomers, chlordane , DDT and its metabolites (DDD and DDE), dieldrin, andtoxaphene were detected at levels exceeding comparison values in both on-site and off-site soilsamples. Aldrin and toxaphene levels exceeded both child and adult comparison values (chronicEMEGs) in off-site soils, while alpha-BHC, beta-BHC, DDT, and dieldrin exceeded CREGcomparison values. Chlordane exceeded the child chronic EMEG in on-site soil. Generally thehighest 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 detectedpreviously.

In 1996, the companies removed an additional 4,475 tons of contaminated soil, both on and offsite. Rust conducted soil sampling again in September 1996 to verify that this soil remediationhad achieved its goals. The results of this sampling effort indicated that the remediation reducedpesticide contamination in surface soils to EPA performance standards. These performancestandards are generally greater than or within one order of magnitude of ATSDR ComparisonValues (See Appendix G). However, while the statistical analysis showed that the site hadattained the clean-up goals, some individual samples exceeded a few of the performancestandards. This was particularly true of toxaphene. The highest concentrations were generallyfound in the immediate vicinity of culverts and drainage features. At the request of the NorthCarolina Department of Health and Natural Resources, the companies excavated an additional129 cubic yards of surface soils (Rust, 1997b).


APPENDIX E:

EXPOSURE PATHWAY TABLE FOR THE GEIGY CHEMICAL CORPORATION SITE
PATHWAYNAMESOURCEMEDIAPOINT OFEXPOSUREROUTE OFEXPOSURERECEPTORPOPULATIONTIMECONTAMINANTS OFCONCERN
COMPLETED EXPOSURE PATHWAYS
Groundwaterpesticideblendingfacilityground-waterpublic andprivate wells ingestion
dermal contact
inhalation
private well users and residents supplied with water from municipal wells 1 and 4past Public well data
alpha-BHC
beta-BHC
lindane

Private well data
alpha-BHC
beta-BHC
dieldrin
lindane

POTENTIAL EXPOSURE PATHWAYS
Surface soilpesticideblendingfacilitysoil on site and
off site
incidental ingestion
dermal contact
on-site workers
nearby residents
past aldrin
chlordane
DDT
toxaphene
AirpesticideblendingfacilityairAberdeeninhalationAberdeenresidentspastunknown


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-BHC2.9 3/23/87MUW-04100

400

0.006

Child EMEG (I)

Adult EMEG (I)

CREG

beta-BHC4.93/23/87MUW-016

20

0.02

Child EMEG (I)

Adult EMEG (I)

CREG

gamma-BHC 17
11.6

0.8 (n = 4)
1.2 (n = 7)

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-BHC6.45/12/95PW-17 100
400
0.006
Child EMEG (I)
Adult EMEG (I)
CREG
beta-BHC125/12/95PW-17 6
20
0.02
Child EMEG (I)
Adult EMEG (I)
CREG
delta-BHC4.65/12/95PW-17NA--
gamma-BHC6.55/12/95PW-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
0.1CREG
4,4'-DDE 0.0077
<0.25
7/20/94
7/15/96
PW-14
PW-14
0.1CREG
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
dieldrin0.134/11/95PW-17 0.5
2
0.002
Child EMEG (C)
Adult EMEG (C)
CREG
heptachlor epoxide<0.257/15/96PW-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
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
MW = monitoring well
ppb = parts per billion
RMEG = ATSDR's reference dose media evaluation guide
u = all reporting limits raised due to high levels of target compound
U = detection limit for the contaminant, contaminant not detected at or below this level

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
CREG = cancer risk evaluation guide
EMEG (C) = chronic environmental media guide
EMEG (I) = intermediate environmental media evaluation guide
J = estimated value
MW = monitoring well
ppb = parts per billion
PZ = piezometer
U = detection limit for the contaminant, contaminant not detected at or below this level

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, C3/23/87off-site (SS-09) 30
400
0.5
Child EMEG (C)
Adult EMEG (C)
CREG
4,4'-DDD28unknownon-site (SS-06)3CREG
4,4'-DDE 1.1

17 J, C
3/23/87

3/23/87
off-site (SS-12)

on-site (SS-02)
2CREG
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
* site-wide average
C = pesticide identity confirmed with secondary analysis (GC/MS)
CREG = cancer risk evaluation guide
EMEG (C) = chronic environmental media guide
EMEG (I) = intermediate environmental media evaluation guide
J = estimated value
NA = not available
ppm = parts per million
RMEG = ATSDR's reference dose media evaluation guide
SS = soil sample

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

CREG = cancer risk evaluation guide
EMEG (C) = chronic environmental media guide
EMEG (I) = intermediate environmental media evaluation guide
ppm = parts per million

Source: Rust, 1997a


APPENDIX H: ATSDR's COMPARISON VALUES

ATSDR comparison values are media-specific concentrations that are considered to be "safe" underdefault 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 hasselected 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 emphasizedstrongly enough that comparison values are not thresholds of toxicity. While concentrations at or belowthe relevant comparison value may reasonably be considered safe, it does not automatically follow thatany environmental concentration that exceeds a comparison value would be expected to produce adversehealth effects. Indeed, the whole purpose behind highly conservative, health-based standards andguidelines is to enable health professionals to recognize and resolve potential public health problemsbefore they become actual health hazards. The probability that adverse health outcomes will actuallyoccur as a result of exposure to environmental contaminants depends on site-specific conditions andindividual 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 determinedin 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 athigh doses, because human cancer incidence data for very low levels of exposure simply do not exist, andprobably never will. In neither case can the resulting screening values (i.e., EMEGs or CREGs) be usedto 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 inwater, soil, or air that are unlikely to be associated with any appreciable risk of deleteriousnoncancer effects over a specified duration of exposure. EMEGs are derived from ATSDRminimal risk levels (MRL) by factoring in default body weights and ingestion rates. SeparateEMEGS 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-specificconcentrations which correspond to a minimal risk level (MRL), factoring in body weight andingestion 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, orgroup of studies, that produces statistically or biologically significant increases in frequency orseverity of adverse effects between the exposed population and its appropriate control.

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.

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 derived for acute(<14 days), intermediate (15-364 days), and chronic (>365 days) exposures, and are published inATSDR's Toxicological Profiles for specific chemicals.

No-Observed-Adverse-Effect Level (NOAEL) is the dose of chemical at which there were nostatistically significant or biologically significant increases in frequency or severity of adverseeffects seen between the exposed population and its appropriate control. Nonadverse effects maystill 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.



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