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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
Disclaimers
Si'.
This document is designed to provide supporting information regarding the regulatory determinations
for aldrin and dieldrin as part of the Contaminant Candidate List (CCL) evaluation process. This
document is not a regulation, and it does not substitute for the Safe Drinking Water Act (SDWA) or the
Environmental Protection Agency's (EPA's) regulations. Thus, it cannot impose legally-binding
requirements on EPA, States, or the regulated community, and may not apply to a particular situation
based upon the circumstances. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
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Acknowledgments
This document was prepared in support of the EPA Office of Ground Water and Drinking
Water's regulatory determinations for aldrin and dieldrin as part of the Contaminant Candidate List
(CCL) evaluation process. Dan Olson and Karen Wirth served as EPA's team leaders for the CCL
regulatory determination process and James Taft as Standards and Risk Management Division Chief.
Tara Cameron and Karen Wirth served as Work Assignment Managers. The CCL Work Group provided
technical guidance throughout La particular, Karen Wirth, Dan Olson, and Joyce Donohue provided
scientific and editorial guidance. External expert reviewers and many stakeholders provided valuable
advice to improve the CCL Program and this document. The Cadmus Group, Inc., served as the primary
.contractor providing support for this work. The major contributions of Matt Collins, Emily Brott, and
Ashton Koo are gratefully acknowledged. George Hallberg served as Cadmus' Project Manager.
111
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Preliminary Regulatory Determination Support Document for A Idrin and Dieldrin
November, 2001
USEPA, Office of Water Report: EPA 815-R-01-011, November, 2001
CONTAMINANTCANDIDATE LIST
PRELIMINARY REGUJoATORY DETERMINATION
SUPPORT DOCUMENT FOR ALDRIN AND DIELDRIN
Executive Summary
Aldrin and dieldriu are 1998 Contaminant Candidate List (CCL) regulatory determination priority
contaminants. Aldrin and dieldrin are two of the contaminants considered by the US Environmental
Protection Agency (EPA) for a regulatory determination. The available data on occurrence, exposure,
and other risk considerations suggest that regulating aldrin and dieldrin with a National Primary Drinking
Water Regulation (NPDWR) may not present a meaningful opportunity to reduce health risk. EPA
presents preliminary CCL regulatory determinations and further analysis in the Federal Register Notice.
To make this preliminary regulatory determination for aldrin and dieldrin, EPA used approaches
guided by the National Drinking Water Advisory Council's (NDWAC) Working Group on CCL and Six-
Year Review. The Safe Drinking Water Act (SDWA) requirements for.National Primary Drinking Water
Regulation (NPDWR) promulgation guided protocol development The SDWA Section 1412(b)(l)(A)
specifies that the determination to regulate a contaminant must be based on a finding that each of the
following criteria are met: (i) "the contaminant may have adverse effects on the health of persons"; (ii)
"the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in
public water systems with a frequency and at levels of public health concern"; and (iii) "in the sole
judgement of the Administrator, regulation of such contaminant presents a meaningful opportunity for
health risk reduction for persons served by public water systems." Available data were evaluated to
address each of the three statutory criteria.
Aldrin and dieldrin, related synthetic organic compounds (SOCs), are insecticides that were
discontinued for most agricultural uses in 1974 and all uses in 1987. They were used primarily on com
and citrus products, as well as for general crops and timber preservation. In addition, aldrin and dieldrin
were used for termite-proofing plywood, building boards, and the plastic and rubber coverings of
electrical and telecommunication cables. Aldrin is considered moderately persistent in the environment,
with a half-life of approximately 110 days. Dieldrin is among the common degradates of aldrin. Dieldrin
is considered extremely persistent, with a half-life of up to seven years.
Aldrin and dieldrin were monitored from 1993 to 1999 under the SDWA Unregulated Contaminant
Monitoring (UCM) program. Aldrin and dieldrin are also regulated or monitored by other federal
programs including the Clean Water Act Priority Pollutants list, the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA), and the Resource Conservation and Recovery
Act (RCRA). In addition, the Emergency Planning and Community Right-to-Know Act (EPCRA) has
listed aldrin as an extremely hazardous substance (EHS) and aldrin is on EPCRA's Toxic Release
Inventory (TRI).
Aldrin and dieldrin have been detected at low frequencies and concentrations in ambient surface and
ground water and stream bed sediments sampled by the United States Geological Survey's (USGS)
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin November, 2001
L>h^
H°™ m ** SamPles * at Ieast 40 States (both substances) recorded in the
l^frfn61^^! ^ be"1 deteCted * pubMc Water **** CPWS) samples collected under
% ^S f^^0^ a ^oss-section of Sta*« ™* UCM data are v£y low with oZ
rff ^Sf? of f s^1^ sbowmg detections for aldrin and dieldrin, respecfaVely Systems with
detections of aldnn and dieldrin constitute approximately 0.02% and 0.1%of cwss-slclon
respecfavely Systems with detections above the Health Reference Level flSS
" bCt ' f°r ** "^^ « ^ estimated * W8H
and 0 1
0 4%
% of fto Jfa?s Pwaid
were reported fa *" state of Iowa- or fa minois
While there is evidence that aldrin and dieldrin have adverse health effects in humans their
aldnn and dieldnn may be unukely to represent a meaningful opportunity for health risk reaction
VI
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
Table of Contents
Disclaimers .. i
Acknowledgments iii
Executive Summary .. v
Table of Contents vii
List of Tables ix
List of Figures xi
1.0 INTRODUCTION 1
1.1 Purpose and Scope 1
1.2 Statutory Framework/Background 1
1.3 Statutory History of Aldrin 2
1.4 Regulatory Determination Process 3
1.5 Determination Outcome 4
2.0 CONTAMINANT DEFINITION 5
2.1 Physical and Chemical Properties 5
2.2 Environmental Fate/Behavior 6
3.0 OCCURRENCE AND EXPOSURE 8
3.1 Use and Environmental Release 8
3.1.1 Production and Use 8
3.1.2 Environmental Release 8
3.2 Ambient Occurrence 9
3.2.1 Data Sources and Methods 9
3.2.2 Results 11
3.2.2.1 Aldrin 11
3.2.2.2 Dieldrin 12
3.3 Drinking Water Occurrence 14
3.3.1 Analytical Approach 15
3.3.1.1 UCM Rounds land 2 15
3.3.1.2 Developing a Nationally Representative Perspective ;. 16
3.3.1.2.1 Cross-Section Development 16
3.3.1.2.2 Cross-Section Evaluation 18
3.3.1.3 Data Management and Analysis 18
3.3.1.4 Occurrence Analysis 19
3.3.1.5 Additional Drinking Water Data from the Corn Belt 21
, 3.3.2 Results , 21
3.3.2.1 Aldrin , 21
vu
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin November, 2001
3.3.2.1.1 Occurrence Estimates 21
3.3.2.1.2 Regional Patterns " 74
3.3.2.2 Dieldrin .'.'.'.'."!!.'.'.'!'.'!'.'.'.'.'.'.'.'.'.'.'.'."" 27
3.3.2.2.1 Occurrence Estimates ',, 27
3.3.2.2.2 (Regional Patterns '....'..............,',,! 29
3.4 Conclusion ...!'. 37
4.0 HEALTH EFFECTS 33
4.1 Hazard Characterization and Mode of Action Implications ] 33
4.2 Dose-Response Characterization and Implications in Risk Assessment 34
4.3 Relative Source Contribution ] ] 35
4.4 Sensitive Populations 36
4.5 Exposure and Risk Information 37
4.6 Conclusion ' 37
5.0 TECHNOLOGY ASSESSMENT ; 37
5.1 Analytical Methods " 38
5.2 Treatment. Technology 35
6.0 SUMMARY AND CONCLUSIONS -DETERMINATION OUTCOME 39
References
Appendix A: Abbreviations and Acronyms 51
vm
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
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List of Tables
Table 2-1: Physical and chemical properties 6
Table3-l: Aldrin detections in stream bed sediments 11
Table 3-2: Dieldrin detections and concentrations in streams and ground water ' 13
Table 3-3: Dieldrin detections and concentrations in sediments, whole fish, and bivalves
(all sites) 14
Table 3-4: Summary occurrence statistics for aldrin 23
Table 3-5: Summary occurrence statistics for dieldrin 28
Table 5-1: Analytical methods for aldrin and dieldrin 38
IX
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
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List of Figures
Figure 3-1: Geographic distribution of cross-section States for Round 2 (SDWIS/FED) 17
Figure 3-2: States with PWSs with detections.of aldrin for all States with data in SDWIS/FED (Round 2)
25
Figure 3-3: Round 2 cross-section States with PWSs with detections of aldrin (any PWSs with results
greater than the Minimum Reporting Level [MRL]; above) and concentrations greater than the Health
Reference Level (HRL; below)
26
Figure 3-4: States with PWSs with detections of dieldrin for all States with data hi SDWIS/FED (Round
2) . -.- 30
Figure 3-5: Round 2 cross-section States with PWSs with detections of dieldrin (any PWSs with results
greater than the Minimum Reporting Level [MRL]; above) and concentrations greater than the Health
Reference Level (HRL; below) 31
XI
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
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1.0 INTRODUCTION
1.1 Purpose and Scope
This document presents scientific data and summaries of technical information prepared for, and used
in, the Environmental Protection Agency's (EPA) regulatory determinations for aldrin and dieldrin.
Information regarding the physical and chemical properties, environmental fate, occurrence and exposure,
and health effects of aldrin and dieldrin is included. Analytical methods and treatment technologies are
also discussed. Furthermore, the regulatory determination process is described to provide the rationale for
the decision.
1.2 Statutory Framework/Background
The Safe Drinking Water Act (SDWA), as amended hi 1996, requires the EPA to publish a list of
contaminants (referred to as me Contaminant Candidate List, or CCL) to assist in priority-setting efforts.
The contaminants included on the CCL were not subject to any current or proposed National Primary
Drinking Water Regulations (NPDWR), were known or anticipated to occur in public water systems, and
were known or suspected to adversely affect public health. These contaminants therefore may require
regulation under SDWA. The first Drinking Water CCL was published on March 2,1998 (USEPA,
1998a; 63 FR 10274), and a new CCL must be published every five years thereafter.
The 1998 CCL contains 60 contaminants, including 50 chemicals or chemical groups, and 10
microbiological contaminants or microbial groups. The SDWA also requires the Agency to select 5 or
more contaminants from the current CCL and determine whether or not to regulate these contaminants
with an NPDWR. Regulatory determinations for at least 5 contaminants must be completed 3Vz years
after each new CCL.
Language in SDWA Section 1412(b)(l)(A) specifies that the determination to regulate a contaminant
must be based on a finding that each of the following criteria are met:
Statutory Finding i. .. .the contaminant may have adverse effects on the health of persons;
Statutory Finding ii. the contaminant is known to occur or there is substantial likelihood that the
contaminant will occur in public water systems with a frequency and at levels of public health
concern; and
Statutory Finding Hi. in the sole judgement of the Admmistrator, regulation of such contaminant
presents a meaningful opportunity for health risk reduction for persons served by public water
systems:
The geographic distribution of the contaminant is another factor evaluated to determine whether it
occurs at the national, regional or local level. This consideration is important because the Agency is
charged with developing national regulations and it may not be appropriate to develop NPDWRs for
regional or local contamination problems.
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin , November, 2001
EPA must determine if regulating this CCL contaminant will present a meaningful opportunity to
reduce health nsk based on contaminant occurrence, exposure, and other risk considerations. The Office
of Ground Water and Dnnkmg Water (OGWDW) is charged with gathering and analyzing the
occurrence, exposure, and nsk information necessary to support this regulatory decision. The OGWDW
must evaluate when and where this contaminant occurs, and what would be the exposure and risk to
For each of the regulatory determinations, EPA must first publish in the Federal Register the draft
detemunations for public comment EPA will respond to the public comments received! and will then
fmahze regulatory determinations. If the Agency finds that regulations are warranted, the regulations
musttfaen be formally proposed within twenty-four months, and promulgated eighteen months later EPA
has determined that there is sufficient information to support regulatory determinations for aldrin and
ouelonn.
1 3 Statutory History of Aldrin
monitored ™*r toe SDWA Unregulated Contaminant Monitoring
S"T ^ (USEPA' 1992; 5? m 31776)' Monitori°g «*sed for small public water
systems (PWSs) under a direct final rule published January 8, 1999 (USEPA, 1999a: 64 FR 1494) and
endedfor large PWSs with promulgation of the new Unregulated Contaminant Monitoring Regulation
^^)Jf^™S^mber 17' 19" (USBPA« 1999b; ** ** 50556> ** effec*ve JanuarJ 1. 2001 At
the time the UCMR lists were developed, the Agency concluded there were adequate monitoring data for
regulatory determinations. This obviated the need for continued monitoring under the new UCMR list.
«. ^A pwvfoiMfy recommended guidelines for exposure to aldrin and dieldrin in drinking water
toough health advisories issued in 1991 and 1988, respectively (USEPA, 1991a; USEPA, 1988). As part
document prOCeSS' health effects data have been ^ewed. These are summarized in Section 4.0 of mis
r monitored ^ 01her federal PW^nans as well. They are included
ants list for which the EPA e
,r™ TW * reguiatea or monitored by other federal programs as well. They are incli
on the Clean Water Act Priority Pollutants list for which the EPA establishes ambient water quality
cntena. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA
-Superfund •) includes aldrin and dieldrin as hazardous substances while the Resnm™ rm,mmrinn
, . s sng
rep0rtable (Pjantity" ****, for aldrin and dieldrin, is one
In addition, die Emergency Planning and Community Right-to-Know Act (EPCRA) has listed aldrin
SSSl hazar^OUS rtb!bn" OB**- ™* P»«» °f EHSs in excess of the Threshold Planning
1**11188 °ertam ^^^y Plam^»g activities to be conducted. For aldrin, the
SS* .Quantily£500.lbs tf il » m «olten form, in solution, or in powder form with particle
lOOmicrons. Otfaerw^aldrin's TPQ is 10,000 Ibs (USEPA, 1996). Aldrin is also on
EPCRA s Toxic Release Inventory (TRI). The TRI requkes certain industrial sectors to publicly report
the environmental release or transfer of listed chemicals (USEPA, 2000c).
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Preliminary Regulatory Determination Support Document for Aldrin anii Dieldrin
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The Occupational Safety and Health Administration (OSHA) recommends occupational exposure
limits for aldrin and dieldrin of 250 fig/m3 for an 8-hour workday over a 40-hour workweek. The
National Institute for Occupational Safety and Health (NIOSH) suggests that aldrin and dieldrin levels be
kept at the lowest amounts that can be measured reliably (ATSDR, 1993).
The U.S. Department of Agriculture (USDA) discontinued registration and use of aldrin and dieldrin
.as pesticides in 1970. In 1972, EPA canceled all but the following three uses of aldrin and dieldrin:
subsurface ground insertion for termite control, the dipping of nonfood plant roots and tops, and moth-
proofing in manufacturing processes using completely closed systems. This cancellation decision was
finalized in 1974. The sole manufacturer of aldrin and dieldrin, Shell Chemical Company, ceased
producing the compounds for mom-proofing and the dipping of non-food plants in 1974, and canceled
their use as termiticides in 1987 (ATSDR, 1993). . "
1.4 Regulatory Determination Process
In developing a process for the regulatory determinations, EPA sought input from experts and
stakeholders. EPA asked the National Research Council (NRC) for assistance in developing a
scientifically sound approach for deciding whether or riot to regulate contaminants on the current and
future CCLs. The NRC's Committee on Drinking Water Contaminants recommended that EPA: (1)
gather and analyze health effects, exposure, treatment, and analytical methods data for each contaminant;
(2) conduct a preliminary risk assessment for each contaminant based on the available data; and (3) issue
a decision document for each contaminant describing the outcome of the preliminary risk assessment.
The NRC noted that in using this decision framework, EPA should keep hi mind the importance of
involving all interested parties;
One of the formal means by which EPA works with its stakeholders is through the National Drinking
Water Advisory Council (NDWAC). The NDWAC comprises members of the general public, State and
local agencies, and private groups concerned with safe drinking water, and advises the EPA Administrator
on key aspects of me Agency's drinking water program. The NDWAC provided specific
recommendations to EPA on a protocol to assist the Agency in making regulatory determinations for
current and future CCL contaminants. Separate but similar protocols were developed for chemical and
microbial contaminants. These protocols are intended to provide a consistent approach to evaluating
contaminants for regulatory determination, and to be a tool that will organize information in a manner that
will communicate the rationale for each determination to stakeholders. The possible outcomes of the
regulatory determination process are: a decision to regulate, a decision not to regulate, or a decision that
some other action is needed (e.g., issuance of guidance).
The NDWAC protocol uses the three statutory requirements of SDWA Section 1412(b)(l)(A)(i)-(iii)
(specified hi section 1.2) as the foundation for guiding EPA in making regulatory determination
decisions. For each statutory requirement, evaluation criteria were developed and are summarized below.
To address whether a contaminant may have adverse effects on the health of persons (statutory
requirement (i)), the NDWAC recommended that EPA characterize the health risk and estimate a health
reference level for evaluating the occurrence data for each contaminant.
Regarding whether a contaminant is known to occur, or whether there is substantial likelihood that
the contaminant will occur, in public water systems with a frequency, and at levels, of public health
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Preliminary Regulatory Determination Support Document for Alarm andDieldrin November, 2001
concern (statutory requirement (ii)), the NDWAC recommended that EPA consider: (1) the actual and
estimated national percent of public water systems (PWSs) reporting detections above half the health
reference level; (2) the actual and estimated national percent of PWSs with detections above the health
reference level; and (3) the geographic distribution of the contaminant
To address whether regulation of a contaminant presents a meaningful opportunity for health risk
reduction for persons served by public water systems (statutory requirement (iii)) the NDWAC
recommended that EPA consider estimating the national population exposed above half the health
reference level and the national population exposed above the health reference level.
The approach EPA used to make preliminary regulatory determinations followed the general format
recommended by the NRC and the NDWAC to satisfy the three SDWA requirements under section
1412(b)(l)(AXi)-(iii). The process was independent of many of the more detailed and comprehensive
nsk management fectors that will influence the ultimate regulatory decision making process. Thus, a
decision to regulate is the beginning of the Agency regulatory development process, not the end.
Specifically, EPA characterized the human health effects that may result from exposure to a
contaminant found in drinking water. Based on this characterization, the Agency estimated a health
reference level (HRL) for-each contaminant.
For each contaminant EPA estimated the number of PWSs with detections >'/£HRL and >HRL the
population served at these benchmark values, and the geographic distribution, using a large number of
occurrence data (approximately seven million analytical points) that broadly reflect national coverage
Round 1 and Round 2 UCM data, evaluated for quality, completeness, bias, and representativeness, were
the primary data used to develop national occurrence estimates. Use and environmental release
urformation, additional drinking water data sets (e.g., State drinking water data sets, EPA National
Pesticide Survey, and Environmental Working Group data reviews), and ambient water quality data (eg
NAWQA, State and regional studies, and the EPA Pesticides in Ground Water Database) were also
consulted.
The findings from these evaluations were used to determine if there was adequate information to
evaluate the three SDWA statutory requirements and to make a preliminary determination of whether to
regulate a contaminant.
1.5 Determination Outcome
After reviewing the best available public health and occurrence information, EPA has made a
preliminary determination not to regulate the contaminants aldrin and dieldrin with NPDWRs. EPA has
found that aldrin and dieldrin may have adverse effects on the health of persons and are known to occur in
at least some PWSs. However, EPA has not found that they occur in public water systems at frequencies
or levels of public health concern. Furthermore, all uses of these compounds were suspended in 1987
EPA does not consider exposure to aldrin or dieldrin to be widespread nationally. All preliminary CCL
regulatory determinations will be presented in the Federal Register Notice. The following sections
summarize the data used by the Agency to reach this preliminary decision.
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Preliminary Regulatory Determination Stqjport Document for Aldrin and Dieldrin
November, 2001
2.0 CONTAMINANT DEFINITION
Aldrin and dieldrin are both synthetic organic compounds (SOCs) that are white powders when pure,
but tan powders in thejr technical-grade forms. Aldrin is generated by the Diels-Alder condensation of
hexachlorocyclopentadiene with bicyclo[2.2.1]-2,5-heptadiene. Its chemical name is 1^,3,4,10,10-
hexacUoroJ,4}4a,53,8a-hexahydro-l,4^endo,exo-5,8-dimemanonaphmalene (abbreviated HHDN).
Dieldrin is generated by the epoxidation of aldrin. The chemical name for dieldrin is 1,2,3,4,10,10-
hexacMoro^6,7-epo:^-l,4,4a^,6,7i8$^^
HEQD). The Shell Chemical Company was the sole United States manufacturer and distributor of these
compounds. Trade names for aldrin include: Aldree, Aldrex, Drinox, Octalene, Seedrin, and Compound
118. Some dieldrin trade names are: Alvit, Dieldrix, Octalox, Quintox, and Red Shield (ATSDR, 1993).
Aldrin and dieldrin are insecticides that were discontinued for all uses hi 1987. Aldrin and dieldrin
combat insects by contact or ingestion, and were used primarily on corn and citrus products, as well as for
general crops and timber preservation. In addition, aldrin and dieldrin were used for termite-proofing
plywood, building boards, and the plastic and rubber coverings of electrical and telecommunication
cables (ATSDR, 1993).
2.1 Physical and Chemical Properties
Table 2-1 lists summary information regarding the physical and chemical properties of aldrin and
dieldrin. Also included are their CAS Registry Numbers and molecular formulas.
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
Table 2-1: Physical and chemical properties
Illlillili^^
CAS number
Molecular Formula
309-00-2
C'i2H8Cl
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
Aldrin is classified as a moderately persistent compound, which signifies that its half life in soil
ranges from 20-100 days (Howard, 1991). Aldrin degrades to dieldrin by epoxidation in all aerobic and
biologically active soils. Another metabolite of aldrin in soil is aldrin acid (ATSDR, 1993).
Mathematical models estimate that aldrin would degrade by 69% to dieldrin in 81 days when applied
within IS cm from the soil surface. The half life of aldrin was estimated to be approximately 110 days
when applied to soil at a rate of Ll-3.4 kg/hectare, with 95% disappearance in 3 years. The half life of
aldrin was shown to be significantly lower in sandy loam compared to clay loam soils (36.5 versus 97
days when applied at a rate of 9 kgfoectare; ATSDR, 1993).
Dieldrin is extremely persistent in soil, with a residence time of often greater than 7 years. Although
volatilization is dieldrin's most important terrestrial loss process, its low vapor pressure keeps it from
evaporating quickly from soil. Another loss process from soil is adsorption on dust particles and
atmospheric transport (Howard, 1991). An experiment with dieldrin applied to a microagroecosystem
demonstrated that 73% of the compound remained on the soil surface after 11 days. Soil moisture content
also affects dieldrin volatilization rates. One study showed that after five months, about 18% of dieldrin
had volatilized from moist land compared to 2% from flooded and 7% from dry lands (ATSDR, 1993).
Volatilization rates for dieldrin decrease with time and increase with increasing temperature to a
maximum at 25°C. Dieldrin is highly resistant to biodegradation in soil, with an estimated half life in soil
of 868 days (estimated using the Henry's law constant and the organic carbon partition coefficient, K^;
ATSDR, 1993).
Aldrin sorbs to soil and is not available to leach to ground water systems, as evidenced by its general
absence in ground water samples (ATSDR, 1993; Howard, 1991). However, small amounts of aldrin
have been detected in surface waters. Volatilization is expected to be a significant loss process for aldrin
in water, with the rate of volatilization directly proportional to wind speed and current velocity and
hiversely proportional to water body depth (Howard, 1991). Aldrin was photooxidized by 75% to
dieldrin following 48 hours of irradiation at 238 nm in filtered natural field water. Studies show that
aldrin degrades under anaerobic conditions in biologically active wastewater sludge (pH 7-8,35° C) with
a half life of under one week (ATSDR, 1993).
Dieldrin is also mostly absent from ground water samples because of its tendency to sorb to soil.
Dieldrin that is sorbed to waterborne sediments can run-off to surface waters. Dieldrin does not undergo
hydrolysis or significant aqueous biodegradation. Conflicting data exist regarding the importance of
volatilization for dieldrin in water (Howard, 1991; ATSDR, 1993). Dieldrin is slowly converted in the
presence of sunlight to photodieldrin, a sterepisomer of the compound (water half-life of 4 months;
Howard, 1991). Dieldrin added to natural water (from a drainage canal in an agricultural area) and
incubated in the dark degraded by less than 20% hi 16 weeks. Dieldrin is stable against significant
degradation hi both biologically active and anaerobic wastewater sludge (89% remained after 48 hours of
continuous anaerobic digestion; 45% remained after 9 days of aerobic digestion; ATSDR, 1993).
Aldrin and dieldrin have ranges of log K^, values from 5.68 to 7.4, and from 4.32 to 6.2, respectively,
suggesting high potentials for bioaccumulation. Dieldrin's extreme nonpolarity gives it a strong affinity
towards animal fat and plant waxes (ATSDR, 1993; Howard ,1991).
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin November, 2001
3.0 OCCURRENCE AND EXPOSURE
This section examines the occurrence of aldrin and dieldrin in drinking water. While no complete
national database exists of unregulated or regulated contaminants in.drinking water from public water
systems (PWSs) collected under the Safe Drinking Water Act (SDWA), this report aggregates and
analyzes existing State data that have been screened for quality, completeness, and representativeness.
Populations served by PWSs exposed to aldrin and dieldrin are estimated, and the occurrence data are
examined for regional or other special trends. To augment the incomplete national drinking water data
and aid in the evaluation of occurrence, information on the use and environmental release, as well as
ambient occurrence of aldrin and dieldrin, is also reviewed.
3.1 Use and Environmental Release
* f-
3.1.1 Production and Use
Aldrin and dieldrin combat insects by contact or ingestion, and were used primarily on corn and citrus
products, as well as for general crops and timber preservation. In addition, aldrin and dieldrin were used
for termite-proofing plywood, building boards, and the plastic and rubber coverings of electrical and
telecommunication cables (ATSDR, 1993). In 1972, EPA canceled all but the following three uses of
aldrin and dieldrin: subsurface ground insertion for termite control, the dipping of non-food plant roots
and tops, and moth-proofing in manufacturing processes using completely closed systems. This
cancellation decision was finalized in 1974.
Aldrin was not imported into the United States prior to the 1974 cancellation decision, however Shell
International (Holland) imported the chemical for limited use from 1974 to 1985 (with the exception of
1979 and 1980, when imports were temporarily suspended). An estimated 1-1.5 million Ibs of aldrin
were imported annually from 1981-1985, after which time importation ceased. No importation data were
found for dieldrin. By 1987, all uses of aldrin and dieldrin had been canceled voluntarily by the
manufacturer (ATSDR, 1993).
3.1.2 Environmental Release
Aldrin is listed as a Toxic Release Inventory chemical. In 1986, the Emergency Planning and
Community Right-to-Know Act (EPCRA) established the Toxic Release Inventory (TRI) of hazardous
chemicals. Created under the Superfund Amendments and Reauthorization Act (SARA) of 1986 EPCRA
is also sometimes known as SARA Title m. The EPCRA mandates that larger facilities publicly'report
when TRI chemicals are released into the environment. This public reporting is required for facilities
with more than 10 full-time employees that annually manufacture or produce more than 25 000 pounds
or use more than 10,000 pounds, of a TRI chemical (USEPA; 1996; USEPA, 2000c).
Under these conditions, facilities are required to report the pounds per year of aldrin released into the
environment both on- and off-site. The production, import, and use of aldrin had been canceled by the
time the TRI was instated, however, and therefore no release or transfer data were reported. In 1995
Resource Conservation and Recovery Act (RCRA) subtitle C hazardous waste treatment and disposal
facilities were added to the list of those facilities required to present release data to the TRI. This addition
became effective for the 1998 reporting year, which is the most recent TRI data eminently available.
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Waste treatment facilities from three States (AR, MI, TX) reported releases of aldrin in 1998, with on-
and off-site releases totaling 25,622 pounds. The on-site quantity is subdivided into air emissions, surface
water discharges, underground injections, and releases to land. Most of the aldrin released to the
environment was released directly to land (22,000 Ibs; USEPA, 2000a).
Although the TRI data can be useful in giving a general idea of release trends, it is far from
exhaustive and has significant limitations. For example, only industries that meet TRI criteria (at least 10
full-time employees and the manufacture and processing of quantities exceeding 25,000 Ibs/yr, or use of
more than 10,000 Ibs/yr) are required to report releases. These reporting criteria do not account for
releases from smaller industries; Also, the TRI data is meant to reflect releases and should not be used to
estimate general exposure to a chemical (USEPA, 2000b). ~
Aldrin and dieldrin are included in the Agency for Toxic Substances and Disease Registry's
(ATSDR) Hazardous Substance Release and Health Effects Database (HazDat). This database records
detections of listed chemicals in site samples; aldrin and dieldrin were both detected in 40 States. The
National Priorities List (NPL) of hazardous waste sites, created in 1980 by the Comprehensive
Environmental Response, Compensation & Liability Act (CERCLA), is a listing of some of the most
health-threatening waste sites in the United States. Aldrin and dieldrin were detected in NPL hazardous
waste sites in 31 and 38 States, respectively (USEPA, 1999c).
In summary, aldrin and dieldrin have not been produced in the United States since 1974, and all uses
of the pesticides were canceled by 1987. The chemicals had been used mostly on corn and citrus
products. Aldrin was imported to the United States from Holland from 1974-1985 (with the exception of
1979 and 1980) hi quantities of approximately 1-1.5 million Ibs/yr. TRI data from 1998 suggest that
aldrin continues to be released into the environment, even though the chemical is no longer produced nor
used in the United States. The presence and persistence of aldrin and dieldrin in the environment is
evidenced by detections of the compounds in hazardous waste sites in at least 31 and 38 States,
respectively (at NPL sites), as well as detections of both chemicals in site samples hi at least 40 States
(listed hi ATSDR's HazDat).
3.2 Ambient Occurrence . •
To understand the presence of a chemical hi the environment, an examination of ambient occurrence
is useful. In a drinking water context, ambient water is source water existing in surface waters and
aquifers before treatment The most comprehensive and nationally consistent data describing ambient
water quality hi the United States are being produced through the United States Geological Survey's
(USGS) National Water Quality Assessment (NAWQA) program. (NAWQA, however, is a relatively
young program and complete national data are not yet available from their entire array of sites across the
nation.)
3.2.1 Data Sources and Methods
The USGS instituted the NAWQA program in 1991 to examine water quality status and trends hi the
United States. NAWQA is designed and implemented hi such a manner as to allow consistency and
comparison between representative study basins located around the country, facilitating interpretation of
natural and anthropogenic, factors affecting water quality (Leahy and Thompson, 1994).
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin November, 2001
The NAWQA program consists of 59 significant watersheds and aquifers referred to as "study units "
The study units represent approximately two thirds of the overall water usage in the United States and a
similar proportion of the population served by public water systems. Approximately one half of the
nation's land area is represented (Leahy and Thompson, 1994).
To facilitate management and make the program cost-effective, approximately one third of the study
units at a fame engage in intensive assessment for a period of 3 to 5 years. This is followed by a period of
less intensive research and monitoring that lasts between 5 and 7 years. This way all 59 study units rotate
through intensive assessment over a ten-year period (Leahy and Thompson, 1994). The first round of
mtensiye monitoring (1991-96) targeted 20 units and the second round monitored another 16 beginning in
1994. This first group was more heavily slanted toward agricultural basins. A national synthesis of
results firom these study units, focusing on pesticides and nutrients, has been compiled and analyzed
(Kolpin etal., 2000; Larson etal., 1999; USGS, 1999a).
Aldrin was not an analyte for either the ground water or the surface water NAWQA studies included
in the pesticide and nutrient national synthesis (Kolpin et al., 1998; Larson et al., 1999- USGS 1999b)
Because of analytical and budget constraints the NAWQA program targets certain pesticides, many of
which are high use and/or have potential environmental significance (Larson et al., 1999- USGS 1999a)
Aldnnmay have been excluded because it breaks down in the environment to dieldrin (among other
degradates), which is analyzed in the NAWQA studies (USGS, 1999b). Aldrin persisting in the
environment is more likely to be found in sediments or biotic tissues because of its strong hydrophobicitv
and sorpfaon potential (ATSDR, 1993; Nowell, 1999; USGS, 2000). Consequently, NAWQA
mvcstigators focused their aldrin occurrence studies on bed sediments and aquatic biota tissue (Nowell,
Dieldrin isan analyte for both surface and ground water NAWQA studies. Two of the first 20 study
basms analyzed in the pesticide and nutrient national synthesis reports, the Central Nebraska Basins and
the White River Basin in Indiana, are located in the corn belt where dieldrin use was heavy in the 1960s
The Minimum Reporting Level (MRL) for dieldrin is 0.001 ug/L (Kolpin et al., 1998), substantially
lower than most drinking water monitoring.
-•J?* *f "?*? available for &d&™ occurrence in surface water in the Mississippi River and six major
tributaries draining corn belt States (Goolsby andBattaglin, 1993). These data are the result of aUSGS
regional water quality investigation, and details regarding sampling and analytical methods are described
rathe report
Aldrin and dieldrin are organochlorine insecticides. As a group, organochlorines are hydrophobic
and resist degradation. Hydrophobic ('Vater hating") compounds have low water solubilities and strong
tendencies to sorb to organic material in sediments and accumulate in the tissue of aquatic biota where
they can persist for long periods of time (ATSDR, 1993; USGS, 2000). OrganocMorines may be present
in bed sediments and tissues of aquatic systems even when they are undetectable in the water column
using conventional methods (Nowell, 1999). The occurrence of a toxic compound in stream sediments is
pertinent to drinking water concerns because some desorption of the compound from sediments into water
will occur through equilibrium reactions, although in very low concentrations.
To determine their presence in hydrologic systems of the United States, the NAWQA program has
investigated organochlorine pesticide detections in bed sediments and biotic tissue, focusing on the
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organochlorine insecticides that were used heavily in the past (Nowell, 1999). The occurrence of aldrin,
one of the top three insecticides used for agriculture in the 1960s and widely used to kill termites in
structures until the mid 1980s, and dieldrin was investigated in mis study (Nowell, 1999; tFSGS, 1999a).
Sampling was conducted at 591 sites from 1992-1995 in the 20 NAWQA study units where the first
round of intensive assessment took place. Two of these basins, the Central Nebraska Basins and the
White River Basin in Indiana, are located in the corn belt where aldrin use was heavy in the 1960s.
Details regarding sampling techniques and analytical methods are described by Nowell (1999).
3.2.2 Results
3.2.2.1 Aldrin
Aldrin was not detected, in aquatic biota tissue samples. However, it was detected in stream bed
sediment samples. The occurrence frequencies.above the Minimum Reporting Level (MRL) of 1 fig/kg,
and basic summary statistics, indicate that occurrence in sediments is very low (Table 3-1). Both the
median and 95* percentile concentrations were reported as non-detections (< MRL) across all land use
categories.
Aldrin was detected in sediments only at agricultural or mixed land use sites, perhaps reflecting the
heavy agricultural use in the late 1960s and early 1970s (Table 3-1). Interesting in light of the more
recent termiticide use, no urban detections were reported. This may be partly a function of the NAWQA
sampling design that targeted basins more representative of agricultural and mixed land use conditions for
the first round of intensive monitoring from which these sediment data were produced (see Section 3.2.1
above) (Data from later rounds are not yet available).
Table 3-1: Aldrin detections in stream bed sediments
Detection frequency
(% samples > MRL of 1 Jig/kg)
Concentration
(all samples; ng/kg dry weight)
urban
mixed
agricultural
forest-rangeland
0.0 %
0.5 %
0.6 %
0.0 %
median
nd*
nd
nd
nd
95th
oercentile
nd
nd
nd
nd
maximum
nd
3
2.2
nd
all sites
0.4%
nd
nd
after Novell, 1999
"not detected in concentration greater than MRL
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3.2.2.2 Dieldrin
Detection frequencies and concentrations of dieldrin in ambient surface and ground water are low
especially in ground water which is the case for insecticides in general (Table 3-2; Kolpin et al., 1998-
Miller and Wilber, 1999). However, using a common reporting limit of 0.01 ug/L, dieldrin is toe most
commonly detected insecticide in ground water in these USGS studies. This possibly reflects the
historically heavy use of aldrin and dieldrin and clearly indicates dieldrin's environmental persistence
(Kolpin et al., 1998; Miller, 2000). Also, though relatively immobile in water when compared to newer
pesticides, dieldrin is one of the most mobile of the older organochlorine pesticides (USGS, 1999a).
Dieldrin detection frequencies are considerably higher in shallow ground water in urban areas as
compared to shallow ground water in agricultural areas (Table 3-2), a likely consequence of the more
recent use of aldrin and dieldrin as a termiticide and industrial moth-proofing agent until the mid-1980s
Agricultural uses were discontinued in the 1970s. Major aquifers, which are generally deep have very
low detection frequencies and concentrations of dieldrin. Hydrophobic compounds have high sorption
potential and are not very mobile in ground water, making their occurrence in deep aquifers unlikely.
In streams, detection frequencies are higher compared to ground water (Table 3-2) Dieldrin's
chemical characteristics, chiefly its hydrophobicity, make it less likely to be transported to the subsurface
with ground water recharge. Instead, dieldrin sorbs easily to sediments and biotic tissues and may persist
m surface water environments for many years after applications have ceased. Differences hi detection
frequencies and concentrations between urban and agricultural settings are less pronounced for streams
than for ground water, but frequencies and concentrations are greater for streams in agricultural settings
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Table 3-2: Dieldrin detections and concentrations in streams and ground water
Detection frequency
(% samples ;> MRL*)
Concentration percentiles
(all samples; ug/L)
streams
urban
integrator
agricultural
all sites
ground water
shallow urban
shallow
agricultural
major aquifers
all sites
% ;> 0.001 ue/L
3.67%
3.27 %
6.90%
4.64%
,* 5-65%
0.97 %
0.43%
1.42%
% a 0.01 ug/L
1.83 %
1.63%
3.90 %
2.39 %
... 332%
0.65 % .
0.21%
0.93 %
median
nd**
nd
nd
nd
nd
nd
nd
nd
95f
nd
nd
0.007
nd
0.005
nd
nd
nd
maximum
0.016
0.015
0.027
0.19
0.068
0.057
0.03
0.068
*MRLfor dieldrin in water studiesrO.OOl pgfL.
**not detected in concentrations greater than MRL .
The concentrations and detection frequencies of dieldrin in bed sediments and biotic tissues are
considerably higher than water, although the median concentration of all samples is still below the MRL
(Table 3-3). Occurrence of dieldrin is highest in whole fish, highlighting the potential for it to
bioaccumulate (Kolpin et al., 1998). The trend of higher concentrations and detection frequencies hi
urban environments is again apparent when examining dieldrin occurrence across various land use
settings in sediments and biotic tissues. Urban areas have the highest detections and concentrations.
Occurrence in agricultural and mixed land use types is lower and approximately equivalent. Forest and
rangeland show very low occurrence (Nowell, 1999).
While concentrations hi water are generally low, a risk-specific dose (RSD) criteria of 0.02 ug/L, a
concentration associated with a cancer risk level of 1 in 100,000 people, was exceeded at one site at least,
in both suriace and ground water (Kolpin et al., 1998; Larson et al., 1999; USGS, 1998). t
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Table 3-3: Dieldrin detections and concentrations in sediments, whole fish, and bivalves
(all sites)
Detection frequency
(% samples >MRL*)
Concentration percentiles
sediments
•wholefish
bivalves
13.7 %
28.6%
6.4%
median
nd**
nd
nd
9£?
2.7
31.9
6.4
maximum
18
260
20
aJterNoweO, 1999
"MRLfm- tBeldrin in sediments: 1 fig/kg; dlddrin in whole fish and bivalves: 5 us/kg
"not detected 'in concentrations greaser -than MKL
.- 1. to quality investigation provides additional information on the occurrence of
diddnn in the corn belt For surface water sampling from April 1991 to March 1992 from the Mississippi
R!ver andsix ta-butenes draining the corn belt; 8% of all samples and 71% of sites had detections greater
*
33 Drinking Water Occurrence
«s,n ,i *? amended m 1986' retmired Pub«c water systems (PWSs) to monitor for specified
'unregulated' contaminants, on a five year cycle, and to report the monitoring results to the States
Unregulated contammants do not have an established or proposed NPDWR, but they are contaminants
that were formally listed and required for monitoring under federal regulations. The intent was to gather
scientific information on the occurrence of these contaminants to enable a decision as to whether or not
regulations were needed ;A11 non-purchased community water systems (CWSs) and non-purchased non-
tamsaent non-communuy water systems (NTNCWSs), with greater than 150 service connections, were
required to .conduct this unregulated contaminant monitoring. Smaller systems were not required to
conduct this monitoring under federal regulations, but were required to be available to monitor if the State
decided such momtoruig was necessary. Many States collected date from smaller systems. Additional
^5^ to ^ y^gulated Contaminant Monitoring (UCM) program in 1991 (USEPA,
R. 3526) for required momtonng that began in 1993 (USEPA, 1992; 57 FR 31776).
en monitored under me SDWA Unregulated Contaminant Monitoring
!• (USEPA' 1992; 57FR31776)" Monitorkg ceased for small pubSwTto
^^ *°? "^ PUWished JaDUaiy 8' 19" &****• 1999a' 64 ^ 1494), and
endedfor large PWSs with promulgation of the new Unregulated Contaminant Monitoring Regulation
(UCMR) issued September 17, 1999 (USEPA, 1999b; 64 FR 50556) and effective January 1, 2001 At
fce tune the UGMR fart, were developed, the Agency concluded there were adequate mStormgdata for
a regulatory determination. This obviated the need for continued monitoring under the new UCMR list
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33.1 Analytical Approach
Currently, there is no complete national record of unregulated or regulated contaminants in drinking
water from PWSs collected under SDWA. Many States have submitted unregulated contaminant PWS
monitoring data to EPA databases, but there are issues of data quality, completeness, and
representativeness^ Nonetheless, a significant amount of State data are available for UCM contaminants
that can provide estimates of national occurrence, lite contaminant occurrence analyses findings
presented in this report are based on a national cross-section of aggregated State data (i.e., a
representative subset of available State data) derived from the Federal Safe Drinking Water Information
System (SDWIS/FED) database.
The National Contaminant Occurrence Database (NCOD) is an interface to the actual occurrence data
stored in the Safe Drinking Water Information System (Federal version; SDWIS/FED) and can be queried
to provide a summary of the data in SDWIS/FED for a particular contaminant The drinking water
occurrence data for aldrin and dieldrin presented here were derived from monitoring data available in the
SDWIS/FED database. Note, however, that the SDWIS/FED data used in this report have undergone
significant review, edit, and filtering to meet various data quality objectives for the purposes of this
analysis. Hence, not all data from a particular source were used; only data meeting the quality objectives
described below were included. The sources of these data, their quality and national aggregation, and the
analytical methods used to estimate a given contaminant's national occurrence (from these data) are
discussed in this section (for further details see USEPA, 2001a, 2001c).
33.1.1 UCM Rounds 1 and 2
The 1987 UCMicontaminants include 34 volatile organic compounds (VOCs) (USEPA, 1987; 52 FR
25690). Aldrin and dieldrin, synthetic organic compounds (SOCs), were not among these contaminants.
The UCM (1987) contaminants were first monitored coincident with the Phase I regulated contaminants,
during the 1988-1992 period. This period is often referred to as "Round I" monitoring. The monitoring
data collected by the PWSs were reported to the States (as primacy agents), but there was no protocol in
place to report these data to EPA. These data from Round 1 were collected by EPA from many States
over time and put into a database called the Unregulated Contaminant Information System, or URCIS.
The 1993 UCM contaminants include 13 SOCs and 1 inorganic contaminant (IOC) (USEPA, 1992;
57 FR 31776). Monitoring for the UCM (1993) contaminants began coincident with the Phase n/V
regulated contaminants in 1993 through 1998. This is often referred to as "Round 2" monitoring. The
UCM (1987) contaminants were also included in the Round 2 monitoring. As with other monitoring data,
PWSs reported these results to the States. EPA, during the past several years, requested that the States
submit these historic data to EPA and they are now stored in the SDWIS/FED database.
Monitoring and data collection for aldrin and dieldrin, UCM (1993) contaminants, began in Round 2.
Therefore, the following discussion regarding data quality screening, data management, and analytical
methods focuses on SDWIS/FED. Discussion of the URCIS database is included where relevant, but it is
worth noting that the various quality screening, data management, and analytical processes were nearly
identical for the two databases. For further details on the two monitoring periods as well as the databases,
see USEPA (2001a) and USEPA (2001c).
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3.3.1.2 Developing a Nationally Representative Perspective
The Round 2 data contain contaminant occurrence data from a total of 35 primacy entities (including
34 States and data for some tribal systems). However, data from some States are incomplete and biased.
Furthermore, the nationaLrepresentativeness of the data is problematic because the data were not collected
in a systematic or random statistical framework. These State data could be heavily skewed to low-
occurrence or high-occurrence settings. Hence, the State data were evaluated based on pollution-potential
indicators and the spatial/foydrologic diversity of the nation. This evaluation enabled the construction of a
cross-section from the available State data sets that provides a reasonable representation of national
occurrence.
A national cross-section comprised of the Round 2 State contaminant occurrence databases was
established using the approach developed for the EPA report.* Review of Contaminant Occurrence in
Public Water Systems (USEPA, 1999d). This approach was developed to support occurrence analyses for
EPA s Chemical Monitoring Reform (CMR) evaluation, and was supported by peer reviewers and
stakeholders. The approach cannot provide a "statistically representative" sample because the original
monitoring data were not collected or reported in an appropriate fashion. However, the resultant
"national cross-section" of States should provide a clear indication of the central tendency of the national
data. The remainder of this section provides a summary description of how the national cross-section
from the SDWIS/FED (Round 2) database was developed. The details of the approach are presented in
other documents (USEPA, 2001a, 2001b); readers are referred to these for more specific information.
33.1.2.1 Cross-Section Development
As a first step in developing the cross-section, the State data contained in the SDWIS/FED database
(that contains the Round 2 monitoring results) were evaluated for completeness and quality. Some States
reported only detections, or their data had incorrect unite. Data sets only including detections are
obviously biased, over-representing high-occurrence settings. Other problems included substantially
incomplete data sets without all PWSs reporting (USEPA, 2001a; Sections E and JOT).
The balance of the States remaining after me data quality screening were then examined to establish a
national cross-section. This step was based on evaluating the States' pollution potential and geographic
coverage in relation to all States. Pollution potential is considered to ensure a selection of States that
represent the range of likely contaminant occurrence and a balance with regard to likely high and low
occurrence. Geographic consideration is included so that the wide range of climatic and hydrogeologic
conditions across the United States are represented, again balancing the varied conditions mat affect
transport and fate of contaminants, as well as conditions that affect naturally occurring contaminants
The cross-section States were selected to represent a variety of pollution potential conditions Two
primary pollution potential indicators were used. The first factor selected indicates pollution potential
from manufacturing/population density and serves as an indicator of the potential for VOC contamination
within a State. Agriculture was selected as the second pollution potential indicator because the majority
of SOCs of concern are pesticides (USEPA, 2001c; Section HI. A). The 50 individual States were ranked
from highest to lowest based on the pollution potential indicator data. For example, the State with the
highest ranking for pollution potential from manufacturing received a ranking of 1 for this factor and the
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State wife the lowest value was ranked as number 50. States were ranked for their agricultural chemical
use status in a similar fashion.
The States' pollution potential rankings for each factor were subdivided into four quartiles (from
highest to lowest pollution potential). The cross-section States were chosen equally for both pollution
potential factors to ensure representation, for example, from: States with high agrochemical pollution
potential rankings and high manufacturing pollution potential rankings; States with high agrochemical
pollution potential rankings and low manufacturing pollution potential rankings; States with low
agrochemical pollution potential rankings and high manufacturing pollution potential rankings; and States
with low agrochemical pollution potential rankings and low manufacturing pollution potential rankings
(USEPA, 2001c; Section BOLE.). In addition, some secondary pollution potential indicators were
considered to further ensure that the cross-section States included the spectrum of pollution potential
conditions (high to low). At the same time, States within the specific quartiles were considered
collectively across all quartiles to attempt to provide a geographic coverage across all regions of the
United States.
The data quality screening, pollution potential rankings, and geographic coverage analysis established
a national cross-section of 20 Round 2 (SDWIS/FED) States. The cross-section States provide good
representation of the nation's varied climatic and hydrogeologic regimes and the breadth of pollution
potential for the contaminant groups (Figure 3-1).
Figure 3-1: Geographic distribution of cross-section States for Round 2 (SDWIS/FED)
Round 2 (SDWIS/FED) Cross Section
States -
Alaska
Arkansas
Colorado
Kentucky
Maine
Maryland
Massachusetts
Michigan
Minnesota
Missouri
New Hampshire
New Mexico
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Rhode Island
Texas
Washington
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3.3.1.2.2 Cross-Section Evaluation
To evaluate and validate the method for creating the national cross-sections, the method was used to
create smaller State subsets fiom the 24-State, Round 1 (URCIS) cross-section. Again, States were
chosen to achieve a balance from the quartiles describing pollution potential, and a balanced geographic
distribution, to incrementally build subset cross-sections of various sizes. For example, the Round 1
cross-sechon was tested with subsets of 4, 8 (the first 4 State subset plus 4 more States), and 13 (8 State
subsetplus 5) States. Two additional cross-sections were included in the analysis for comparison- a
cross-section composed of 16 States with biased data sets eliminated from the 24 State cross-section for
date quality reasons, and a cross-section composed of all 4Q Round 1 States (USEPA, 2001c: Section
I H.o.l).
These Round 1 incremental cross-sections were then used to evaluate occurrence for an array of both
high and [low occurrence contaminants. The comparative results illustrate several points. The results are
quite stable and consistent for the 8-, 13- and 24-State cross-sections. They are much less so for the 4-
State, 16-State (biased), and 40 State (all Round 1 States) cross-sections. The 4-State cross-section is
apparently too small to provide balance both geographically and with pollution potential, a finding that
concurs with past work (USEPA, 1999d). The CMR analysis suggested that a minimum of 6-7 States was
needed to provide balance both geographically and with pollution potential, and the CMR report used 8
Jstates out of the available data for its nationally representative cross-section (USEPA 1 999d) The 1 6-
State and 40-State cross-sections, both including biased States, provided occurrence results that were
unstable and inconsistent for a variety of reasons associated with their data quality problems (USEPA,
u£\A/lcj occnon HlJB.l).
The 8-, 13-, and 24-State cross-sections provide very comparable results, are consistent, and are
usable as national cross-sections to provide estimates of contaminant occurrence. Including greater data
from more States improves the national representation and the confidence in the results, as long as the
States are balanced related to pollution potential and spatial coverage. The 20-State cross-section
provides the best, nationally representative cross-section for the Round 2 data.
33.13 Data Management and Analysis
The cross-section analyses focused on occurrence at the water system level; i.e., me summary data
presented discuss the percentage of public water system with detections, not flie percentage of samples
with detections. By normalizing the analytical data to the system level, skewness inherent in the sample
data is avoided. System level analysis was used since a PWS with a known contaminant problem usually
has to sample more frequently than a PWS that has never detected the contaminant Obviously me
results of a simple computation of the percentage of samples with detections (or other statistics) can be
skewed by the more frequent sampling results reported by the contaminated site. This level of analysis is
JETS? ^ 7 f^16' 3uSyStem need Only have a single samPle ^ m anneal result g^ ^
toe MKL, i.e., a detection, to be counted as a system with a result "greater than the MRL."
Also, the data used in the analyses were limited to only those data with confirmed water source and
samphng type ^formation. Only standard SDWA compliance samples were used; "special" samples or
investigation samples (investigating a contaminant problem that would bias results) or samples^ '
unknown type were not used in the analyses. Various quality control and review checks were made of the
results, including follow-up questions to the States providing the data. Many of the most intractable data
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quality problems encountered occurred with older data. These problematic data were, in some cases,
simply eliminated from the analysis. For example, when me number of problematic data were
insignificant relative to the total number of observations, they were dropped from the analysis (For further
details see Cadmus, 2000).
As indicated above, Massachusetts is included in the 20-State, Round 2 national cross-section.
Although noteworthy for the presence of SOCs like aldrin and dieldrin, Massachusetts SOC data were
problematic. Massachusetts reported Round 2 sample resulte for SOCs from only 56 PWSs, while
reporting VOC results from over 400 different PWSs. Massachusetts SOC data also contained an
atypically high percentage of systems with analytical detections when compared to all other States.
Through communications with Massachusetts data management staff it was learned that the State's SOC
data were incomplete and that the SDWIS/FED record for Massachusetts SOC data was also incomplete.
For instance, the SDWIS/FED Round 2 data for Massachusetts indicate 18% of systems reported
detections of aldrin and dieldrin. The States with the next highest detection frequencies reported only
0.2% and 0.4% of systems with detections for aldrin and dieldrin, respectively, In contrast,
Massachusetts data characteristics and quantities for lOCs and VOCs were reasonable and comparable
with other States' results. Therefore, Massachusetts was included in the group of 20 SDWIS/FED Round
2 cross-section States with usable data for lOCs and VOCs, but its aldrin and dieldrin (SOC) data were
omitted from Round 2 cross-section occurrence analyses and summaries presented hi this report.
3.3.1.4 Occurrence Analysis
To evaluate national contaminant occurrence, a two-stage analytical approach has been developed.
The first stage of analysis provides a straightforward, conservative, non-parametric evaluation of
occurrence of the CCL regulatory determination priority contaminants as described above. These Stage 1
descriptive statistics are summarized here. Based in part on the findings of the Stage 1 Analysis, EPA
will determine whether more rigorous parametric statistical evaluations, the Stage 2 Analysis, may be
warranted to generate national probability estimates of contaminant occurrence and exposure for priority
contaminants (for details on this two stage analytical approach see Cadmus, 2000,2001).
The summary descriptive statistics presented in Table 3-4 for aldrin and in Table 3-5 for dieldrin are a
result of the Stage 1 analysis and include data from Round 2 (SDWIS/FED, 1993-1997) cross-section
States (excluding Massachusetts). Included are the total number of samples, the percent samples with
detections, the 99th percentile concentration of all samples, the 99th percentile concentration of samples
with detections, and the median concentration of samples with detections. The percentages of PWSs and
population served indicate the proportion of PWSs whose analytical results showed a detections) of the
contaminant (simple detection, > MRL) at any time during the monitoring period; or a detections) greater
than half the Health Reference Level (HRL); or a detections) greater than the Health Reference Level.
The Health Reference Level for aldrin and dieldrin, 0.002 ng/L, is a preliminary estimated health effect
level used for mis analysis (EPA derived me HRL based on cancer potency selecting the most
conservative, and therefore the most protective, value corresponding to the one-in-a-million (1 x 10"6)
cancer risk level).
The 99th percentile concentration is used here as a summary statistic to indicate the upper bound of
occurrence values because maximum values can be extreme values (outliers) that sometimes result from
sampling or reporting error. The 99th percentile concentration is presented for only the samples with'
detections and for all of the samples because the value for the 99th percentile concentration of all samples
19
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Preliminary Regulatory Determination Support Document for Aldrin awJDieldrin
November, 2001
is below the Minimum Rejporting Level (MRL) (denoted by "<" in Tables 3-4 and 3-5). For the same
reason, summary statistics such as the PS^percentile concentration of all samples or the median (or mean)
concentration of all samples are omitted because these also are all "<" values. This is the case because
only 0.006% (aldrin) and 0.064% (dieldrin) of all samples recorded detections in Round 2.
As a simplifying assumption, a value of half the MRL is often used as an estimate of the
concentration of a contaminant in samples/systems whose results are less than the MRL. For
contaminants with relatively low occurrence such as aldrin and dieldrin hi drinking water occurrence
databases, the median or mean value of occurrence using this assumption would be half the MRL (0.5 *
MRL). However, for these occurrence data this is not straightforward. For Round 2, States have reported
a wide range of values for the MRLs. This is in part related to State data management differences as well
as real differences in analytical methods, laboratories, and other factors.
The situation can cause confusion when examining descriptive statistics for occurrence. For example,
most Round 2 States reported non-detections simply as zeroes resulting in a modal MRL value of zero.
By definition the MRL cannot be zero. This is an artifect of State data management systems. Because a
simple meaningful summary statistic is not available to describe the various reported MRLs, and to avoid
confusion, MRLs are not reported hi the summary tables (Tables 3-4 and 3-5).
In Tables 3-4 and 3-5, national occurrence is estimated by extrapolating the summary statistics for the
20-State cross-section (excluding Massachusetts) to national numbers for systems, and population served
by systems, from the Water Industry Baseline Handbook, Second Edition (USEPA, 2000d). From the
handbook, the total number of community water systems (CWSs) plus non-transient, non-community
water systems (NTNCWSs) is 65,030, and the total population served by CWSs plus NTNCWSs is
213,008,182 persons (see Tables 3-4 and 3-5). To generate the estimate of national occurrence based on
the cross-section occurrence findings, the national number of PWSs (or population served by PWSs) is
simply multiplied by the percentage value for the particular cross section occurrence statistic (e.g. the
national estimate for the total number of PWSs with detections (11) is the product of the total national
number of PWSs (65,030) and the percentage of PWSs with detections .(0.016%)).
Included in Tables 3-4 and 3-5, in addition to the cross-section data results, are results and national
extrapolations from all Round 2 reporting States. The data from the biased States are included because of
the very low occurrence of aldrin and dieldrin in drinking water samples in all States. For contaminants
with very low occurrence, such as aldrin and dieldrin where very few States have detections, any
occurrence becomes more important, relatively. For such contaminants, the cross-section process can
easily miss a State with occurrence that becomes more important This is the case with aldrin and
dieldrin.
Extrapolating only from the cross-section States, the very low occurrence of aldrin and dieldrin
clearly underestimates national occurrence. For example, while data from biased States like Alabama
(reporting 100% detections >HRL, >V* HRL, and >MRL for both aldrin and dieldrin) exaggerate
occurrence because only systems with detections reported results, their detections are real and need to be
accounted for because extrapolations from the cross-section States do not predict enough detections in the
biased States. Therefore, results from all reporting Round 2 States, including me biased States, are also
used here to extrapolate to a national estimate. Using the biased States' data should provide conservative
estimates, likely overestimates, of national occurrence for aldrin and dieldrin.
20
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
As exemplified by the cross-section extrapolations for aldrin and dieldrin, national extrapolations of
these Stage 1 analytical results can be problematic, especially for contaminants with very low occurrence,
because the State data used for the cross-section are not a strict statistical sample. For this reason, the
nationally extrapolated estimates of occurrence based on Stage 1 results are not presented in the Federal
Register Notice. The presentation in the Federal Register Notice of only the actual results of the cross-
section analysis maintains a straight-forward presentation, and the integrity of the data, for stakeholder
review. The nationally extrapolated Stage 1 occurrence values are presented here, however, to provide
additional perspective. A more rigorous statistical modeling effort, the Stage 2 analysis, could be
conducted on the cross-section data (Cadmus, 2001). The Stage 2 results would be more statistically
robust and more suitable to national extrapolation. This approach would provide a probability estimate
and would also allow for better quantification of estimation error.
• , . ''.. • ' " -• ' .i' •'..'.••'•'''.--' ' • ' ' ' :.
33.1.5 Additional Drinking Water Data from the Corn Belt
.... • :-; f .... ."•.-.••. . -••'.:.
To augment the SDWA drinking water data analysis described above, and to provide additional
coverage of the corn belt States where the use of aldrin and dieldrin as agricultural insecticides was
historically high, independent analyses of SDWA drinking water data from the States of Iowa, Illinois,
and Indiana are reviewed below. Raw water aldrin and dieldrin monitoring data are also included from
rural, private water supply wells in Illinois.
The Iowa analysis examined SDWA compliance monitoring data from surface and ground water
PWSs for the years 1988-1995 (Hallberg et al., 1996). Illinois and Indiana compliance monitoring data
for surface and ground water PWSs were evaluated mostly for the years after 1993, though some earlier
data were also included (USEPA, 1999d). The raw water data from Illinois were collected from rural,
private supply wells (Goetsch et al., 1992). Data sources, data quality, and analytical methods for these
analyses are described in the respective reports; they were all treated similarly to the data quality reviews
for this analysis.
33.2 Results
33.2.1 Aldrin
33.2.1.1 Occurrence Estimates
The percentages of PWSs with detections of aldrin are very low (Table 3-4). The cross-section shows
only approximately 0.02% of PWSs (approximately 11 PWSs nationally) experienced detections at any
concentration level (>MRL, >1A HRL, and >HRL), affecting about 0.02% of the population served
(approximately 40,000-50,000 people nationally) (see also Figure 3-3). All of the detections were in
systems using ground water. The percentage of PWSs (or population served) in a given source category
(i.e., ground water) with detections >MRL, >1A HRL, or >HRL is the same because the estimated HRL is
lower than the MRL. Hence, any detection reported is also greater than the HRL. While concentrations
are low — for the detections the median concentration is 0.58 ug/L and the 99th percentile concentration
is 0.69 \igfL — these values are greater than the HRL.
As noted above, because of the very low occurrence, the cross-section States yield an underestimate.
Hence, all data are used, even the biased data, to present a conservative upper bound estimate.
Conservative estimates of aldrin occurrence using all of the Round 2 reporting States still show relatively
21
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
low detection frequencies (Table 3-4). Approximately 0.2% of PWSs (estimated at 138 PWSs nationally)
experienced detections at any concentration level (>MRL, >% HRL, and >HRL), affecting about 0.5% of
the population served (approximately 1,052,000 people nationally). The proportion of surface water
PWSs with detections was greater than ground water systems. Again the percentages of PWSs (or
populations served) wife detections >MKL, >Vx HRL, or >HRL are the same because of the low HRL.
The median concentration of detections is 0.18 ug/L and the 99th percentile concentration is 4.4 ug/L.
The Round 2 reporting States and the Round 2 national cross-section show a proportionate balance in
PWS source waters compared to the national inventory. Nationally, 91% of PWSs use ground water (and
9% surface waters): Round 2 reporting States and the Round 2 national cross-section show that 87% use
ground water (and 13% surface waters). The relative populations served are not as comparable.
Nationally, about 40% of the population is served by PWSs using ground water (and 60% by surface
water). For the Round 2 cross-section, 29% of the cross-section population is served by ground water
PWSs (and 71% by surface water). For all Round 2 reporting States, 31% of the population is served by
ground water PWSs (and 69% by surface water). As a consequence of these disproportions, the resultant
national extrapolations are not additive.
Drinking water data from the corn belt States of Iowa, Indiana, and Illinois also show very low
occurrence of aldrin. There were no detections of the pesticide in the Iowa or Indiana SDWA compliance
monitoring data for surface or ground water PWSs (Hallberg et aL, 1996; USEPA, 1999d). While Illinois
also had no detections of the compound in ground water PWSs, it was detected in surface water PWSs in
that State. Occurrence was low with 1.8% of surface water systems, and 0.10% of samples, showing
detections. The 99th percentile concentration of all samples was below the reporting level and the
maximum concentration was 2.4 ug/L (USEPA, 1999d). A survey of Illinois rural, private water supply
wells showed very low occurrence of aldrin as well. Only 0.3% of all sampled wells had detections at a
reporting limit of 0.004 ugflL (Goetsch et al., 1992).
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Preliminary Regulatory Determination Support Document for Alarm andDieldrin
November, 2001
Table 3-4: Summary occurrence statistics for aldrin
Freonencv Factors
Total Number of Samples
Percent of Samples with Detections
99° Percentile Concentration (all samples)
Health Reference Level
Minimum Reporting Level (MRL)
99* Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GW PWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Peculation of SW PWSs
Occurrence bv Svstem
% PWSs with detections (> MRL)
Range of Cross-Section States
GW PWSs with detections
SW PWSs with detections
% PWSs > 1/2 Health Reference Level (HRL)
Range of Cross-Section States
GW PWSs > 1/2 Health Reference Level
SW PWSs > 1/2 Health R|ference Level
% PWSs > Health Reference Level
Range of Cross-Section States
GW PWSs > Health Reference Level
SW PWSs > Health Reference Level
Occnrrence bv Population Served
% PWS Population Served with detections
Range of Cross-Section States
GW PWS Population with detections
SW PWS Population with detections
% PWS Population Served > 1/2 Health Reference Level
Range of Cross-Section States
GW PWS Population > 1/2 Health Reference Level
SW PWS Population > 1/2 Health Reference Level
% PWS Population Served > Health Reference Level
Range of Cross-Section States
GW PWS Population > Health Reference Level
SW PWS Pooulation > Health Reference Level
20 State
I
Cross-Section
(Round 2)
31,083
0.006%
< fNon-detect)
0.002 ug/L
Variable4
0.69 ug/L '
0.58 ug/L
12,165
10,540
1,625
47,708,156
14,043,051
33.665.105
0.016%
0 - 0.23%
0.019%
0.000%
0.016%
0 - 0.23%
0.019%
0.000%
0.016%
0 - 0.23%
0.019%
0.000%
0.018%
0-0.35%
0.062%
0.000%
0.018%
0-0.35%
0.062%
0.000%
0.018%
0 - 0.35%
0.062%
0.000%
All Reporting '
2
States
(Round?,)
41,565
0.132%
< (Non-detect)
0.002 ug/L
Variable4
4.40 HE/L
0.18 ug/L
15,123
13,195
1,928
58,979,361
18,279,343
40.700.018
0.212%
0 - 100 %
0.167%
0.519%
0.212%
0 - 100 %
0.167%
0.519%
0.212%
0 - 100 %
0.167%
0.519%
0.494%
0 - 100 %
0.414%
0.530%
0.494%
0 - 100 %
0.414%
0.530%
0.494%
0-100%
0.414%
0.530%
National System &
Population Numbers3
—
- '
-•
. -
,.-
-
' , ~
65,030
59,440
5390
213,008,182
85,681,696
127.326.486
National Extrapolation
11
N/A
11
0
11
N/A
11
0
11
N/A
11
0
138
N/A
99
29
138
N/A
99
29
138
N/A
99
29
39,000
N/A
53,000
0
39,000
N/A
53,000
0
39,000
N/A
53,000
0
1,052,000
N/A
355,000
674,000
1,052,000
N/A
355,000
674,000
1,052,000
N/A
355,000
674.000
1. Summary Results based on data from 20-Stale Crass-Section (minus Massachusetts).from SDWtiMED, UCM (1993) Round 2.
2. Summary Results based on data from all reporting States from SDMlS/fED, UCM (1993) Round 2.
3. Total PWS and population numbers arc from EPA March 2000 Water Industry Baseline Handbook.
4. See Section 3.3.1.4 for discussion.
5. National extrapolations are Jrom the 20&atecross*ectlonda^
- PWS - Public Water Systems; GW - Ground Water; SW - Surface Water; MRL - Minimum Reporting Level (for laboratory analyses);
HRL-Health Reference Level, an estimated heahh effect level used forprelimi^^ •" Not Applicable."
- The Health Reference Level (HRL)ttsedfor aldrin fs 0.002 pg/L. This Is a draft value for waridng review onfy.
- Total Number of Samples - the total number of analytical records for aldrin,
- 99th Percentile Concentration «the concentration value of the 99th percentUe of either Maru^ytical results or Just the detections ftnp^/L)
-Median Concentration of Detections-fa median anafyturi
- Total Number of PWSs - the tola! number ofpubttc water systems with records for aldrin
- Total Population Served - the total population served by public water systems with records for aldrin
- % PWS with detections, % PWS > % Health Reference Level, % PWS > Health Reference Level-percent of the total nwnber ofpirffo water s^^
exceeded the MRL, % Health Reference Level, Ifealth Reference Level, respectively
- % PWS Population Served with detections, %'PWS Population Served >% Health Reference Level, % PWS Population Served > Health Reference Level - percent of the total population served
by PWSs -with at least one analytical result exceeding the MRL, % Health Reference Level, or the Health Reference Level, respectively
23
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Preliminary Regulatory Determination Support'Document for Aldrin and Dieldrin
November, 2001
33.2.1.2 Regional Patterns
Occurrence results are displayed graphically by State in Figures 3-2 and 3-3 to assess whether any
distinct regional patterns of occurrence are present Thirty-four States reported Round 2 data but seven of
those States have no data for aldrin (Figure 3-2). Another 22 States did not detect aldrin. The remaining
5 States have detected aldrin in drinking water and are generally located either in the southern United
States or the Northeast (Figure 3-2). In contrast to the summary statistical data presented in the previous
section, this simple spatial analysis includes the biased Massachusetts data.
The simple spatial analysis presented in Figures 3-2 and 3-3 suggests that special regional analyses
are not warranted. The State of Alabama does, however, stand out as having relatively high occurrence
for reasons that are uncleaV. While there is a weak geographic clustering of drinking water detections in a
few southern and northeastern States (including the State of Massachusetts' biased data), this is partly the
result of so few States with any detections. Further, use and environmental release information described
in Section 3.1 of this report indicates that aldrin detections are more widespread than the drinking water
data suggest Two out of the three TRI States (Arkansas and Michigan) that reported releases of aldrin
into the environment did not report detections of the chemical in PWS sampling. Furthermore, aldrin's
widespread presence in the environment is evidenced by detections of the compound in hazardous waste
sites in at least 31 States (at NPL sites), as well as detections in site samples in at least 40 States (listed in
ATSDR's HazDat).
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
Figure 3-2: States with PWSs with detections of aldrin for all States with data in SDWIS/FED
(Round 2)
All States
Aldrin Detects in AH Round 2 States
| States not in Round 2
ig No data for Aldrin
States with No Detections (No PWSs > MRL)
f States with Detections (Any PWSs > MRL)
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
Figure 3-3: Round 2 cross-section States with PWSs with detections of aldria (any PWSs with
results greater than the Minimum Reporting Level [MRL]; above) and concentrations greater than
the Health Reference Level (HRL; below)
•Sauofj&usodoaatsl, ai o«tffcr»r*i l7jeXfWSs > URL
Aldrl* Occnrreacc IB Cross-section States
States not in Cross-Section
No data for Aldrin
0.00% PWSs > MRL
0.01 - 1.00% PWSs > MRL
> law. PWSS > MRL •
o
Aldria Occxirence IB Cross-sectioB Stain
States not in Cross-Section
No data for Aldrin
0.00% PWSs > HRL
0.01 - 1.00% PWSl > HRL
> 1.00% PWSs > HRL
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
33.2.2 Dieldrin
33.2.2.1 Occurrence Estimates
The percentages of PWSs with detections are very low (Table 3-5). The cross-section shows
approximately 0.1% of PWSs (about 61 PWSs nationally) experienced detections at any concentration
level (>MRL, >Yz HRL, and >HRL), affecting less than 0.1% of the population served (approximately
150,000 people nationally) (see also Figure 3-5). The percentages of PWSs (or population served) in a
given source category (i.e., ground water) with detections greater than the MRL, Vz HRL, or HRL are the
same because the estimated HRL is less than the MRL. Hence, any detection reported is also greater than
the HRL. Detection frequencies are marginally higher for surface water systems when compared to
ground water systems. While concentrations are also low — for samples with detections the median
concentration is 0.16 ug/L and the 99th percentile concentration is 1.36 ug/L— these values are greater
than the HRL.
As noted above, because of the very low occurrence, the cross-section States yield an underestimate.
Hence, all data are used, even the biased data, to present a conservative upper bound estimate.
Conservative estimates of dieldrin occurrence using all of the Round 2 reporting States still show
relatively low detection frequencies (Table 3-5). Approximately 0.2% of PWSs (estimated at 137 PWSs
nationally) experienced detections at any concentration level (>MRL, >% HRL, and >HRL), affecting
about 0.4% of the population served (approximately 793,000 people nationally). The proportion of
surface water PWSs with detections was greater than ground water systems. Again the percentages of
PWSs (or populations served) with detections greater than the MRL, H HRL, or HRL are the same
because of the low HRL. The median concentration of detections is 0.42 jig/L and the 99th percentile
concentration is 4.4 ug/L.
The Round 2 reporting States and the Round 2 national cross-section show a proportionate balance in
PWS source waters compared to the national inventory. Nationally, 91% of PWSs use ground water (and
9% surface waters): Round 2 reporting States and the Round 2 national cross-section show that 88% use
ground water (and 12% surface waters). The relative populations served are not similarily comparable.
Nationally, about 40% of the population is served by PWSs using ground water (and 60% by surface
water). For the Round 2 cross-section, 30% of the cross-section population is served by ground water
PWSs (and 70% by surface water). For all Round 2 reporting States, 32% of the population is served by
ground water PWSs (and 68% by surface water). As a consequence of these disproportions, the resultant
national .extrapolations are not additive.
Drinking water data from the corn belt States of Iowa, Indiana, and Illinois also show very low
occurrence of dieldrin. There were no detections of the pesticide in the Iowa SDWA compliance
monitoring data for surface or ground water PWSs (Hallberg et al, 1996). While Illinois and Indiana also
had no detections of the compound in ground water PWSs, it was detected in surface water PWSs hi those
States (USEPA, 1999d). Occurrence was low in both States: 1.8% of surface water systems (0.1% of
samples) showed detections in Illinois and 2.1 % of surface water systems (0.3% of samples) showed
detections in Indiana. For Illinois and Indiana surface water PWSs, the 99th percentile concentrations of
all samples were below the reporting level and the maximum concentrations were 0.1 ug/L and 0.04 ug/L,
respectively (USEPA, 19£9d). Furthermore, in a survey of rural, private water supply wells in Illinois,
only 1.6% of all sampled wells had detections of dieldrin (Goetsch et al., 1992).
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
Table 3-5: Summary occurrence statistics for dieldrin
Er«a««evF«cton
ToUl Number of Samples
Percent of Samples with Detections •
99* Perccntile Concentration (all samples)
Health Reference Level
Minimum Reporting Level (MRL)
99* Percentile Concentration'of Detections
Median Concentration of Detections
Total Number of PWSs "
Number of GW PWSs
Number of SW PWSs
Total Population
Population of GW PWSs
PomjIatioBofSWPWSs
Occii-rence bv Sv«tem
•/. PWSs with detections (> MRL)
Range of Cross-Section States
GW PWSs with detections
SW PWSs with detections
% PWSs > 1/2 Health Reference Level (HRL)
Range of Cross-Section States
GW PWSs > 1/2 Health Reference Level
SW PWSs > 1/2 Health Reference Level
% PWSs > Health Reference Level
Range of Cross-Section States
GW PWSs > Health Reference Level
SW PWSs > Health Reference Level
Jccarrenee bv Pollution Served
% PWS Population Served with detections
Range of Cross-Section States
GW PWS Population with detections
SW PWS Population with detections
% PWS Population Served > 1/2 Health Reference Level
Range of Cross-Section States
GW PWS Population > 1/2 Health Reference Level
SW PWS Population > 1/2 Health Reference Level
% PWS Population Served > Health Reference Level
Range of Cross-Section States
GW PWS Population > Health Reference Level
SW PWS Pooulation > Health Reference Level
20 State
Cross-Section1
(Round 2)
29,603
0.064%
< (Non-detect)
0.002 ug/L
Variable4
136 us/L
0.16 ug/L
11,788
10^29
1,459
45,784,187
13,831,864
31.952.323
0.093%
0 - 0.97%
0.087%
0.137%
0.093%
0 - 0.97%
0.087%
0.137%
0.093%
0 - 0.97%
0.087%
0.137%
0.070%
0 - 2.00%
0.146%
0.038%
0.070%
0 - 2.00%
0.146%
0.038%
0.070%
0 - 2.00%
0.146%
0.038%
AH Reporting
States2
(Round 2)
40,055
0.135%
< (Non-detect)
0.002 ug/L
Variable4
4.40 UK/L
0.42 pg/L
14,725
12,968
1,757
56,909,027
18,044,000
38.865.027
0.211%
0 - 100%
0.177%
0.455%
0.21 1%
0 - 100%
0.177%
0.455%
0.211%
0 - 100%
0.177%
0.455%
0.372%
0-100%
0.371%
0.372%
0.372%
0-100%
0.371%
0.372%
0.372%
0-100%
0.371%
0.372%
National System &
Population Numbers3
•
_
' -
„
—
65,030
59,440
5,590
213,008,182
85,681,696
127.326.486
National Extrapolation*
61
N/A
52
8
61
N/A '
52
8
61
N/A
52
8
137
N/A
105
25
137
N/A
105
25
137
N/A
105
25
150,000
N/A
125,000
48,000
150,000.
N/A
125,000
48,000
150,000
N/A
125,000
48.000
793,000
N/A
318,000
474,000
793,000
N/A
318,000
474,000
793,000
N/A
318,000
—474.000
4, SttSfcOm 33J.4Jer*Kitalo«
S. N
-'fffS"PutScWncrSiiaans; GV-CmadWaler;
W^a^AX&rm&U&rnitakH^ht^tfc
-ntfMlll»^miKttad(HlU)laeilJa-aeUHnit0.002ff/L. This is a draft value far mx-Ung mi wordy.
i numbers.
-tenaSonmalflttvcfatfiathci^^
-KftrSPtfulalfiinSayalwtttiikualom. K PWS Population Saved >
-pemM^AfUiia
l. KPt^PopuMmSeri^>He^
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Preliminary Regulatory Determination Support Document for Aldrin and Dieldrin
November, 2001
33.23.2 Regional Patterns
Occurrence results are displayed graphically by State in Figures 3-4 and 3-5 to assess whether any
distinct regional patterns of occurrence are present. Thirty-four States reported Round 2 data but 7 of
those States have no data for dieldrin (Figure 3-4). Another 19 States did not detect dieldrin. The
remaining 8 States detected dieldrin in drinking water, and are generally located either in the southern
United States or in the Northeast (Figure 3-4). In contrast to the summary statistical data presented in the
previous section, this simple spatial analysis includes the biased Massachusetts data.
The simple spatial analysis presented in Figures 3-4 and 3-5 suggests that special regional analyses
are not warranted. The State of Alabama does, however, stand out as having relatively high occurrence
for reasons that are unclear. While there is a weak geographic clustering of drinking water detections in a
few southern and northeastern States (including the State of Massachusetts' biased data), this is partly the
result of so few States with any detections. Further, use and environmental release information (Section
3.1) and ambient water quality data (Section 3.2) indicate that dieldrin detections are more widespread
than the drinking water data suggest. Detections of the compound in hazardous waste sites in at least 38
States (atNPL sites), site samples in at least 40 States (listed in ATSDR's HazDat), and water, sediment,
and biotic tissue quality data from the NAWQA program provide evidence for nationwide occurrence.
29
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
Figure 3-4: States with PWSs with detections of dieldrin for all States with data in SDWIS/FED
(Round 2)
AH States
Dieldrin Detections in All Round 2 States
I States not in Round 2
^j No data for Dieldrin
iH States with No Detections (No PWSs > MRL)
jf States with Detections (Any PWSs > MRL)
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Figure 3-5: Round 2 cross-section States with PWSs with detections of dieldrin (any PWSs with
results greater than the Minimum Reporting Level [MKLJ; above) and concentrations greater than
the Health Reference Level (HRL; below)
•StaeafMaaachiaats is an csilHcrwillt 18.18% PWSs > URL
enrreaee In Cross-section States
States not in Cross-Section
No data for Dieldrin
0.00% PWSs >MRL
0.01 - LOOK PWSs > MM.
> 1.00% PWSs > MRL *
Dieldrin Occurrence in Cron-Kction States
States not in Cross-Section
Mo °^> t°r Dieldrin
0.00% PWSs > HRL
0.01 - 1.00% PWSs > HRL
> 1.00% PWSs> HRL
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3.4 Conclusion
Aldrin has been detected at very low frequencies and concentrations in bed sediments sampled during
the first round of the USGSNAWQA studies. Aldrin releases have been reported through TRI. Dieldrin
has been detected at low frequencies and concentrations in ground and surface water sampled during the
first round of the USGS NAWQA studies, and at similar frequencies and concentrations in surface waters
of the Mississippi River and major tributaries. Dieldrin occurrence is greater in stream bed sediments and
biotic tissue, however. Both aldrin and dieldrin have been found at ATSDR HazDat and CERCLA NPL
sites across the country.
Aldrin and dieldrin have been detected in PWS samples collected under SDWA. Occurrence
estimates are very low with only 0.006% and 0.06% of all cross-section samples showing detections for
aldrin and dieldrin, respectively. Significantly, the values for the 99th percentile and median
concentrations of all cross-section samples are less than the MRL for both contaminants. For Round 2
cross-section samples with detections, the median concentration for aldrin is Q.58 ug/L and the 99th
percentile concentration is 0.69 ug/L. Dieldrin Round 2 cross-section samples with detections show
median and 99th percentile concentrations of 0.16 ug/L and 1.36 fig/L, respectively. Systems with
detections constitute only 0.02% of Round 2 cross-section systems (an estimate of 11 systems, nationally)
for aldrin, and 0.1% of Round 2 cross-section systems (about 61 systems, nationally) for dieldrin.
National estimates for the population served by PWSs with detections are also very low (40,000-
50,000 for aldrin and 150,000 for dieldrin), and are the same for all categories (>MRL, >1A HRL, >HRL).
These estimates constitute less than 0.02% of the national population for aldrin and less than 0.1% of the
national population for dieldrin. Using more conservative estimates of occurrence from all States
reporting SDWA Round 2 monitoring data, including States with biased data, 0.2% of the nation's PWSs
(approximately 138 systems) and 0.5% of the PWS population served (approximately 1,052,000 people)
are estimated to have aldrin detections greater than the MRL, Vz HRL, and HRL. More conservative
estimates for dieldrin show that 0.2% of the nation's PWSs (approximately 137 systems) and 0.4% of the
PWS population served (approximately 793,000 people) are estimated to have detections of dieldrin
greater than the MRL, half the HRL, and the HRL.
Additional SDWA compliance data from the com belt States of Iowa, Indiana, and Illinois examined
through independent analyses support the drinking water data analyzed in this report. There were no
detections of aldrin or dieldrin in either surface or ground water PWSs in Iowa. Illinois reported aldrin
and dieldrin detections from surface water PWSs only, with 1.8% of surface water systems (0.1% of
samples) showing aldrin occurrence and 1.8% of surface water systems (0.1% of samples) showing
dieldrin occurrence. Indiana reported no detections of aldrin in either surface or ground water, though
2.1% of surface water systems (0.3% of samples) reported dieldrin detections. The 99th percentile
concentration of all aldrin samples was below the reporting level and the maximum concentration was 2.4
ug/L. The 99th percentile concentrations of all dieldrin samples from Illinois and Indiana were also below
the reporting level while the maximum concentrations were 0.1 ug/L and 0.04 ug/L, respectively
(USEPA, 1999d). Further, in a survey of rural, private water supply wells in Illinois, aldrin and dieldrin
were detected in only 0.3% and 1.6% of all sampled wells, respectively.
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4.0 HEALTH EFFECTS
A full description of the health effects and the dose-response information for threshold and non-
threshold effects associated with exposures to aldrin or dieldrin are presented in Chapters 7 and 8 of the
Drinking Water Support Document for Aldrin and Dieldrin (USEPA, 2001b). A summary of the
pertinent findings are presented below.
4.1 Hazard Characterization and Mode of Action Implications
Following acute exposure to high doses, the primary adverse health effects of aldrin and dieldrin in
humans are those resulting from neurotoxicity to the central nervous system, including hyperirritability,
convulsions and coma (Jager, 1970; Spiotta, 1951; ACGIH, 1984). In some cases, these may be followed
by cardiovascular effects such as unusually rapid beating of the heart and elevated blood pressure (Black,
1974). Under conditions of longer-term exposure to lower doses of these compounds, neurotoxic
symptoms may also include headache, dizziness, general malaise, nausea, vomiting, and muscle twitching
or muscle spasms (Jager, 1970; ATSDR, 2000b). Dieldrin exposure has been linked to two cases of
immunohemolytic anemia, where an immune system response destroys red blood cells (Hamilton et al.,
1978; Muirhead et al., 1959), and aldrin/dieldrin exposure has been linked with several instances of
aplastic anemia, where bone marrow cannot adequately regenerate red blood cells (de Jong, 1991; Pick et
al., 1965; ATSDR, 2000b). However, at least some of these studies are problematic. In any case,
hematological or immunological (e.g., dermal sensitization) effects have not generally been found in
humans following exposure to either compound.
Common acute or subchronic neurotoxic effects observed in animals are characterized by increased
irritability, salivation, hyperexcitability, tremors followed by convulsions, loss of body weight,
depression, prostration, and death (Borgmannet al., 1952; Walker et al., 1969; Wagner and Greene, 1978;
Woolley et al., 1985; NCI, 1978; Casteel, 1993). Manifestations of hepatotoxicity (e.g., elevated serum
enzyme levels, unregulated liver cell regenerations, rapid turn-over in bile duct cells, localized cell
degeneration and death, etc.) have been observed in annuals following subchronic-to-chronic exposure to
moderate-to-high concentrations of aldrin/dieldrin (summarized in ATSDR, 2000b). Relatively low-dose,
chronic exposures to either compound have been associated with changes in the tissue structure of the
liver in rat studies (e.g., Fitzhugh et al., 1964; Walker et al., 1969). There is some evidence from animals
that aldrin/dieldrin exposure may either induce renal lesions or exacerbate pre-existing kidney illness
(ATSDR, 2000b; Fitzhugh et al., 1964; Harr et al., 1970).
Various in vivo sad in vitro studies have provided evidence that aldrin and dieldrin may act as weak
endocrine disrupters. Changes in male and female hormone levels and/or receptor binding, and
degeneration of male germ cells and seminiferous tubules in the testes (the Leydig cell ultrastructure)
have been observed. In females, effects on the estrus cycle and rapid turnover of breast cells and of the
cells lining the uterus have been reported (ATSDR, 2000b). Oral administration of aldrin/dieldrin to
maternal or paternal animals has produced somewhat equivocal evidence of decreased fertility (Dean et
al., 1975; Epstein et al., 1972; Good and Ware, 1969; Harr et al., 1970; Virgo and Bellward, 1975), and
injection of aldrin in the abdominal cavity has produced various adverse effects on the male reproductive
system (ATSDR, 2000b).
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Immunosuppression by dieldrin has been reported in a number of mouse studies (Krzystyniak et al.,
1985; Loose, 1982; Loose et al., 1981). A number of long-term bioassay studies have provided evidence
that aldrin and dieldrin also cause liver cancer in mice (Davis and Fitzhugh, 1962; Davis, 1965; Song and
Harville, 1964; NCI, 1978; MacDonald et al., 1972; Walker et al, 1972; Thorpe and Walker, 1973;
Meierhenry et al., 1983). In one mouse study, dieldrin was found to have induced lung, lymphoid and
"other" tumors (Walker et al., 1972). In contrast, neither compound has been found to induce liver
tumors in rats (Treon and Cleveland, 1955; Song and Harville, 1964; Deichmann et al., 1967,1970;
Deichmann, 1974; NCI, 1978; Fitzhugh et al., 1964; Walker et al., 1969), although a number of these
studies suffered from one or more serious deficiencies.
Despite some sporadic, statistically significant increases in rectal or liver/biliary cancer, occupational
and epidemiological studies have failed to provide any convincing evidence for the carcinogenicity of
either aldrin or dieldrin in humans (Van Raalte, 1977; Versteeg and Jager, 1973; de Jong, 1991; de Jong
et al., 1997; Ditraglia et aL, 1981; Brown, 1992; Amaoteng-Adjepong et at, 1995). In fact, Ihe ratio of
deaths in the exposed vs. general populations for both specific causes and all causes of death have
generally been less man 1.0. •
$ • '.
Not a great deal is known about the modes of action that may underlie the various toxic effects
produced by exposure to aldrin or dieldrin. The hyperexcitability associated with these compounds'
neurotoxicity has generally been thought to arise from increased and unregulated nerve impulses
throughout the central nervous system, but whether this results from facilitated neurotransmitter release at
the nerve terminals, or from reducing the activity of inhibitory neurotransmitters within the central
nervous system, has been unclear (ATSDR, 2000b). Mehrota et al. (1988,1989) have proposed that
dieldrin may act by inhibiting a calcium-dependent brain enzyme (ATPase), resulting in higher
intracellular calcium levels that would promote neurotransmitter release. More recent work provides
significant evidence that aldrin and dieldrin's principal mode of neurotoxic action likely involves their
role as antagonists for the membrane receptor for the inhibitory neurotransmitter, gamma aminobutyric
acid (GABA), blocking the influx of chloride ion through the GABA-controlled channel (Klaassen, 1996;
Nagata andNarahashi, 1994,1995; Nagata et al., 1994; Brannen et aL, 1998; Johns et al., 1998; Liu et al.,
1997,1998). Additionally, at least one in vitro study using fetal rat brain cells suggests that dieldrin may
have an even greater functional effect on the nerve cells that use dopamine as a neurotransmitter
(Sanchez-Ramos et al., 1998).
Genotoxicity, defined as direct action of the chemical on the genetic material (i.e., DNA), is not
expected to have a predominant role hi the mode of action for these compounds' carcinogenicity. The
capacity of aldrin and dieldrin to inhibit various forms of in vitro intercellular communication hi both
human and animal cells may be significant in triggering tumor production due to cell proliferation,
unregulated cell growth and premature cellular death (Kurata et al., 1982; Wade et al., 1986; Zhong-
Xiang et al., 1986; Mikalsen and Sanner, 1993). However, these growth effects are epigenetic: they are
unrelated to any change in DNA. Generally speaking, hepatocarcinogenic effects in mice may potentially
be associated with epigenetic modes of action, but not in rats.
4.2 Dose-Response Characterization and Implications in Risk Assessment
In adult humans, the acute oral lethal dose for aldrin/dieldrin has been estimated at approximately 70
mg/kg bw (Jager, 1970; ATSDR, 2000b), which is about 3 times the dose reported to have induced
convulsions within 20 minutes of ingestion (Spiotta, 1951). The oral dose that is sufficient to kill 50
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percent of the treated animate (Oral LDjo) was determined in various animal species for the two
compounds; these values have been reported to range from 33-95 mg/kg bw, and appear to be affected by
age at the time of exposure. In rats, LD^ values were reported as 37 mg/kg bw for young adults, 25
mg/kg bw for two week-old pups, and a high 168 mg/kg bw for newborns (Lu etal., 1965).
Meaningful dose-response relationships have not been adequately characterized in humans for any of
the toxic effects of aldrin or dieldrin. In animals, oral exposure to aldrin/dicldrin has produced a variety
of dose-dependent effects over a collective dose range of at least three orders of magnitude (< 0.05-50
mg/kg bw), depending on the specific endpoint and the duration of exposure (ATSDR, 2000b). Dose-
response information for some key chronic and cancer bioassay studies are summarized in Table 9-1 of
the Drinking Water Support Document for Aldrin and Dieldrin (USEPA, 2001). For noncancer effects,
the USEPA has determined oral Reference Doses (RfDs) for both aldrin and dieldrin based upon the most
sensitive relevant toxic effects (critical effects) that have been reported. The RfD is an estimate, with an
uncertainty spanning perhaps an order of magnitude, of a daily oral exposure to the human population
(including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects
during a lifetime. For aldrin, the critical effect was liver toxicity observed in rats after chronic exposure
to approximately 0.025 mg/kg bw-day, Ihe Lowest Observed Adverse Effect Level (LOAEL) and lowest
dose tested (Fitzhugh et al., 1964). This dose was divided by a composite uncertainty factor of 1,000 (to
account for rat-to-human extrapolation, potentially sensitive human subpopulations, and the use of a
LOAEL rather than a No Observed Adverse Effect Level-NOAEL) to yield an oral RfD for aldrin of 3 x
10"5 mg/kg bw-day. Similarly for dieldrin, a chronic rat study NOAEL for liver toxicity of approximately
0.005 mg/kg bw-day (Walker et al., 1969) was divided by a composite uncertainty factor of 100 (to
account for rat-to-human extrapolation and potentially sensitive human subpopulations) to yield an oral
RfD of 5 x 10"5 mg/kg bw-day.
Based upon the mouse long-term bioassays discussed in Section 4.1, the USEPA has classified both
aldrin and dieldrin as group B2 carcinogens under the current cancer guidelines (USEPA, 1986), i.e., as
probable human carcinogens with little or no evidence of carcinogenicity in humans, and sufficient
evidence in animals. Mechanistic studies performed in vitro and in vivo suggest that one or more non-
genotoxic modes of action may underlie or contribute to the carcinogenic potential of aldrin and dieldrin,
but these effects are not completely established, nor can a role for genotoxic mechanisms confidently be
eliminated based upon the available data. Based upon these considerations, the quantitative cancer risk
assessments of aldrin and dieldrin have been conducted conservatively using the linear-default model.
This approach has yielded geometric mean cancer potency estimates for aldrin and dieldrin of 17 and
16 (mg/kg bw-day)"1, respectively. Using mis potency, a concentration of one microgram of aldrin or
dieldrin in a liter of water may be associated with a theoretical cancer risk of 4.9 deaths in a population of
10,000 for aldrin or 4.6 deaths for dieldrin, respectively. For both compounds, a drinking water
concentration of 0.002 ug/L would lead to an estimated increase in lifetime cancer risk of 10"*. This
concentration, 0.002 ug/L, was selected as the Health Reference Level (HRL) for each chemical. The
HRLs are benchmark values that are used in evaluating the occurrence data (Section 3.3) while risk
assessments for the contaminants are being developed.
4.3 Relative Source Contribution
Analysis of relative source contribution compares the magnitude of exposures expected via
consumption of drinking water with those estimated for other relevant media such as food, air and soil.
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The data summarized in Section 3.3 provide the basis for estimating the amounts of aldrin and dieldrin
ingested via drinking water in exposed populations. A less-conservative estimate was achieved by
utilizing the median and 99th percentile detected concentrations derived from only Unregulated
Contaminant Monitoring (UCM) Round 2 cross-section data, which will certainly underestimate to some
degree the true contribution of drinking water to the exposed population's total intake of aldrin/dieldrin.
For a 70 kg adult consuming 2 L/day of water containing aldrin at either 0.58 ug/L (median detect
concentration) or 0.69 ug/L (99th percentile detect concentration), the corresponding aldrin intakes from
drinking water are 1.7 x 10"5 and 2.0 x Ws mg/kg bw-day, respectively. For a 10 kg child consuming 1
L/day of water, the comparable values are 5.8 x 10'5 and 6.9 x 10'5 mg/kg bw-day.
Similarly, for median and 99th percentile detected concentrations of dieldrin (0.16 and 1.36 ug/L,
respectively), the correspojiding adult drinking water intakes of dieldrin are 0.46 x IQr5 and 3.9 x 10'5
mg/kg bw-day, respectively. Dieldrin drinking water intake values for the 10 kg child are 1.6 x KTS and
14 x 10"s mg/kg bw-day.
Chapter 4.0 of the Drinking Water Support Document for Aldrin and Dieldrin (USEPA, 2001)
presents data on the estimated daily dietary intake of aldrin and dieldrin. Combining estimates for non-
fish food with those for fish and shellfish, adult and child dietary intakes of aldrin are estimated at 3.3-6.5
x 10"5 and 13-18 x 10"s mg/kg bw-day, respectively. For dieldrin, the comparable adult and child dietary
intakes are 3.6 xlO"5 and 14 xlO'5 mg/kg bw-day.
s
Comparing these derived estimates for intakes via drinking water and diet, the ratios of dietary intake
to drinking water intake for aldrin range from 1.7 to 3.8 across all combinations of age and drinking water
concentration level. For dieldrin, the food/water intake ratios for adults and children are 0.9 and 1.0 using
the 99* percentile water concentration, and 7.8 and 8.8 using the median water concentration. Applying
the more conservative aldrin/dieldrin water concentrations based upon the monitoring data of all reporting
UCM Round 2 States would reduce all of these food/water ratios by a factor of approximately 3 to 6.
Thus, when conservatively analyzed relative to the diet, drinking water could potentially be responsible
for a significant portion of total daily intake of aldrin/dieldrin, but only for limited populations under
exposure circumstances that are considered unlikely.
The estimated daily intakes of aldrin and dieldrin from air for adults and children are small (ranging
from 0.013 x 10-5 to 0.24 x lO"5) relative to the unlikely, but potential, drinking water intakes and dietary
intakes discussed above. Although soil data were not available for aldrin, data for dieldrin indicates that
ingestion of soil represents only a minor exposure pathway for these compounds.
4.4 Sensitive Populations
The available literature did not provide direct evidence for any human subpopulations that are
particularly sensitive to the toxic affects of aldrin/dieldrin, or for which the relevant information on
absorption, metabolism, or elimination of these chemicals are known to be significantly different from
those for the general population. Speculatively, fetuses and very young children might be at increased
risk from exposures to aldrin/dieldrin as a result of the limited ability of the immature system to transform
these contaminants in the liver to less toxic chemicals that would be eliminated from the exposed
individuals; and as a result would have a higher vulnerability during these critical periods of
development Several mechanistic studies, which describe the prenatal effects of aldrin/dieldrin on
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GABA receptor malfunctions and on subsequent behavioral impairment, may suggest an increased
sensitivity of children (Brannen et al., 1998; Liu et aL, 1998; Johns et al., 1998; Castro et al., 1992).
Declining organ and immune functions may also render the elderly more susceptible to aldrin/dieldrin
toxicity. Additionally, it is reasonable to expect that individuals with compromised liver, immune or
neurological functions (as a result of disease, genetic predisposition or other toxic insult) might also
display increased sensitivity to these compounds. However, no study has convincingly demonstrated
sensitivity of any one group.
4.5 Exposure and Risk Information
Because the HRL of 0.002 ug/L for these compounds is below the Minimum Reporting Level (MRL),
any recorded detection will be above all three reference levels (MRL, '/£ HRL, HRL). Therefore,
estimates of the national population exposed to concentrations greater than any of these levels will be
equivalent For aldrin, data from only the UCM Round 2 cross-section (less-conservative approach or
probable underestimate) indicate that about 39,000 people are served by public water systems (PWSs)
with detections greater than the MRL, ¥t HRL, and HRL. Using the more conservative data from all
reporting Round 2 UCM States (a probable overestimate), approximately 1^052,000 people are served by
systems with detections greater than the MRL, Vi HRL, and HRL. The corresponding estimates for
dieldrin are approximately 150,000 people and 793,000 people, respectively.
For aldrin, the median and 99th percentile concentrations of detections based upon all Round 2 UCM
data were 0.18 and 4.40 ng/L, respectively. Based only upon the 19-State Round 2 cross-section data, the
corresponding values are 0.58 and 0.69 ug/L. The respective two sets of values for dieldrin are 0.42 and
4.40 ug/L, and 0.16 and &6 ug/L. While these values are above the HRL of 0.002 ug/L, it is necessary
to consider that the corresponding values for all samples were below the detection limit, and that the HRL
itself is likely a very conservative estimate of any human risk resulting from exposure to these chemicals.
4.6 Conclusion
In conclusion, while mere is evidence that aldrin and dieldrin may have adverse health effects in
humans, including the potential to cause cancer, these chemicals are detected very infrequently and
generally at very low concentrations in drinking water. Furthermore, there should be no new releases to
the environment because the compounds have not been used in the United States since 1987. Therefore,
it is unlikely that aldrin or dieldrin will occur at frequencies or concentrations that are of public health
concern or that regulation represents a meaningful opportunity for health risk reduction in persons served
by public water systems. Preliminary CCL regulatory determinations and further analysis will be
presented in the Federal Register Notice.
5.0 TECHNOLOGY ASSESSMENT
If a determination has been made to regulate a contaminant, SDWA requires development of
proposed regulations within 2 years of making the decision. It is critical to have suitable monitoring
methods and treatment technologies to support regulation development according to the schedules defined
in the SDWA.
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5.1 Analytical Methods
The availability of analytical methods does not influence EPA's determination of whether or mot a
CCL contaminant should be regulated. However, before EPA actually regulates a contaminant and
establishes a Maximum Contaminant Level (MCL), there must be an analytical method suitable for
routine monitoring. Therefore, EPA needs to have approved methods available for any CCL regulatory
determination contaminant before it is regulated with an NPDWR. These methods must be suitable for
compliance monitoring and should be cost effective, rapid, and easy to use.
Aldrin and dieldrin are unregulated contaminants for which monitoring was required under the
Unregulated Contaminant Monitoring Program (USEPA, 1987; 52 ER 25690). Monitoring for aldrin and
dieldrin was initiated through rulemaking in 1991 (USEPA, 1991b; 56 FR 3526), and began in 1993. The
contaminants already have well-documented analytical methods developed specifically for low-level
drinking water analyses (see Table 5-1).
Table 5-1: Analytical methods for aldrin and dieldrin
Method
EPA 525.2
EPA 505
EPA 508
EPA 508.1
Type
Gas Chromotography
(GCXQuadrupole Mass
Spectrometry (MS)
GC/IonTrapMS
GC/Electron Capture
Detectors (BCD)
GCfECD
GC/ECD
Method Detection
Limit (ug/L) for aldrin
0.11
0.045
0.075
0.014
0.009
Method Detection
Limit (fitg/L) for dieldrin
0.053
0.11
0.012
0.011
0.003
5.2 Treatment Technology
Treatment technologies also do not influence the determination of whether or not a contaminant
should be regulated. But before a contaminant can be regulated with an NPDWR, treatment technologies
must be readily available. EPA's Office of Research and Development (ORD) has researched treatment
technologies for all of the organic compounds listed as regulatory determination priorities on the CCL,
including aldrin and dieldrin. The two appropriate technologies reviewed were granular activated carbon
(GAC) and air stripping.
Granular activated carbon treatment removes contaminants via the physical and chemical process of
sorption, by which the contaminants attach to the carbon surface as water passes through the carbon bed.
Activated carbon has a large sorption capacity for many water impurities including synthetic organic
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contaminants, taste and odor causing compounds, and some species of mercury. Adsorption capacity is
typically represented by the Freundlich isotherm constants, with higher Freundlich (K.) values indicating
greater sorption potential?
Air stripping involves the continuous contact of air with the water being treated, allowing volatile
dissolved contaminants to transfer from the source water to the air. After contact, the "contaminated air"
is swept from the system, taking the contaminant out of contact with the treated water. The driving force
for the water-to-air transfer of the volatile contaminants is the contaminant's concentration gradient
between the water and air. The Henry's Law constant is a commonly used indicator of the tendency of a
contaminant to partition from water to air. A larger Henry's constant indicates a greater equilibrium of
the contaminant in the air. Thus, contaminants having larger Henry's constants are more easily removed
by air stripping.
Predictive computer modeling and specific chemical characteristics were used to determine the
isotherm constants needed to evaluate the two treatment technologies. The rule of thumb used for SDWA
compounds, learned through the development of cost-and-technology documents to support other
drinking water regulations, is that GAC is considered to be cost-effective if the contaminant has a
Freundlich (K) value above 200 (Speth and Adams, 1993). For air stripping, a compound with a Henry's
constant above dibromochloropropane (0.005) or ethylene dibromide (0.037) is considered strippable at a
reasonable cost.
Since aldrin has a predicted Freundlich (K) value of 718,000, it can be effectively treated by the GAC
method. However, because its predicted Henry's Law constant is 0,027, aldrin can only undergo effective
air stripping procedures under certain concentration conditions. Dieldrin has a predicted Freundlich (K)
value of 486,000 and a predicted Henry's Law constant of 2.0 x 10"5. Therefore, only GAC is an
applicable treatment technology for dieldrin. Its low volatilization potential makes air stripping
impractical.
6.0 SUMMARY AND CONCLUSIONS - DETERMINATION OUTCOME
Three statutory criteria are used to guide the determination of whether regulation of a CCL
contaminant is warranted: 1) the contaminant may adversely affect the health of persons; 2) the
contaminant is known or is likely to occur in public water systems with a frequency, and at levels, of
public health concern; and 3) regulation of the contaminant presents a meaningful opportunity for health
risk reduction for persons served by public water systems. As required by SDWA, a decision to regulate
a contaminant commits the EPA to propose a Maximum Contaminant Level Goal (MCLG) and
promulgate an NPDWR for the contaminant. A decision not to regulate a contaminant is considered a
final Agency action and is subject to judicial review. The Agency can choose to publish a Health
Advisory (a nonregulatory action) or other guidance for any contaminant on the CCL that does not meet.
the criteria for regulation.
The available toxicological data indicate that aldrin and dieldrin have the potential to cause adverse
health effects in humans and animals, In humans, the most common manifestation of acute aldrin/dieldrin
toxicity is neurotoxicity to the central nervous system, including hyperirritability, convulsions, and coma,
in some cases followed by cardiovascular effects such as unusually rapid beating of the heart and elevated
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blood pressure. In smaller doses over time, aldrin and dieldrin may cause headache, dizziness, general
malaise, nausea, vomiting, and muscle twitching or muscle spasms. Aldrin and dieldrin toxicity may also
be responsible for reported cases of immunohemolytic and aplastic anemia. Indications of aldrin/dieldrin
toxicity in animal subjects include neurotoxicity, hepatotoxicity (e.g., elevated serum enzyme levels,
unregulated liver cell regenerations, rapid turn-over in bile duct cells, localized cell degeneration and
death), changes in the tissue structure of the liver, renal lesions and exacerbation of pre-existing kidney
illness. Aldrin and dieldrin appear to be weak endocrine disrupters, affecting the reproductive system of
animal subjects. Though their carcinogenicity in mice is established, no occupational or epidemiological
study has convincingly linked aldrin and dieldrin to cancer in humans.
Aldrin and dieldrin are synthetic organic compounds (SOCs) that have been used as agricultural
insecticides (primarily on corn and citrus products) and termite deterrents. Production and most
agricultural uses of aldrin and dieldrin ceased in the U.S. in 1974, and all uses and imports were
discontinued in 1987. The presence and persistence of aldrin and dieldrin in the environment is
evidenced by detections of the compounds in hazardous waste sites in at least 31 and 38 States,
respectively (at NPL sites), as well as detections of both chemicals in site samples in at least 40 States
(listed in ATSDR's HazDat).
In the ambient environment, aldrin and dieldrin are occasionally detected at low concentrations. Both
substances are hydrophobic, and thus are more likely to sorb to surface soil or enter biotic tissue than
enter groundwater aquifers. Aldrin has been detected more commonly in streambed samples in
agricultural land use areas man in other land use areas or in biotic tissue. Dieldrin has been found to
occur most commonly in agricultural surface waters and shallow urban aquifers; it has also been detected
in biotic tissue, suggesting a risk of bioaccumulation.
Monitoring data indicate that aldrin and dieldrin are infrequently detected in public water supplies,
with only 0.006% and 0.06% of all cross-section samples showing detections for aldrin and dieldrin,
respectively. Significantly, the values for the 99th percentile and median concentrations of all cross-
section samples are less than the Minimum Reporting Level (MRL) for both contaminants. According to
the cross-section model, less than 0.02% of the national population served by public water supplies
(40,000-50,000 people) is served by PWSs with aldrin detections and less than 0.1% of the population
(150,000 people) is served by PWSs with dieldrin detections. Using more conservative estimates of
occurrence from all Statesjeporting SDWA Round 2 monitoring data, including States with biased data,
those figures increase to only 0.5% of the PWS population served (approximately 1,052,000 people) for
aldrin, and 0.4% of the PWS population served (approximately 793,000 people) for dieldrin. (For details
of the methodology used to construct the national cross-section, see Section 3.)
Additional data from corn belt States, where use of aldrin and dieldrin was historically high, were
evaluated to supplement the cross-section data. Drinking water data from Iowa, Indiana, and Illinois also
show low occurrence of aldrin and dieldrin. There were no detections in either surface or ground water
PWSs in the State of Iowa. Illinois and Indiana reported no groundwater detections; surface water
detections were low, with 1.8% of Illinois' surface water systems (0.1% of samples) showing detections
of aldrin/dieldrin and 2.1% of Indiana's surface water systems (0.3% of samples) showing detections of
dieldrin alone. For Illinois and Indiana surface water PWSs, the 99th percentile concentrations of all
samples were below the reporting level and the maximum concentrations were 0.1 ug/L and 0.04 ug/L,
respectively. Moreover, in a survey of Illinois community water supply wells dieldrin was detected in'
only 1.6% of all sampled wells.
40
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Preliminary Regulatory DeiOirmination Support Document for Aldrin andDieldrin November, 2001
EPA considers exposure to both the general public and sensitive populations, including fetuses,
infants, and children, in making its regulatory determination. A factor of ten is included in the reference
dose to account for differences in sensitivity between human subpopulations. Besides drinking water,
food intake may also presents risk of exposure to aldrin and dieldrin, of a similar order of magnitude, to
bom children and adults. (Exposure via air and soil are considered less significant)
In conclusion, while there is evidence that aldrin and dieldrin have adverse health effects in humans,
then- occurrence in drinking water at frequencies or concentrations significant for public health concern is
low. Furthermore, occurrence of aldrin and dieldrin in drinking water supplies in the coming years is
likely to decrease, since the substances are no longer produced or used commercially. Therefore
regulation of aldrin and dieldrin may be unlikely to represent a meaningful opportunity for health risk
reduction. Preliminary CCL regulatory determinations and further analysis will be presented in the
Federal Register Notice.
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
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Appendix A: Abbreviations and Acronyms
ACGIH -American Conference of Govenunaatal Industrial Hygienists
ATSDR -Agency for Toxic Substances and Disease Registry
CAS - Chemical Abstract Service
CCL - Contaminant Candidate List
CERCLA - Comprehensive Environmental Response, Compensation & Liability Act
CMR - Chemical Monitoring Reform
CWS - community water system
DBCP - dibromochloropropane
DNA - deoxyribomicleic acid
BCD - electron capture detectors
EHS - extremely hazardous substance
EPA - Environmental Protection Agency
EPCRA - Emergency Planning and Community Right-to-Know Act
FR - federal register
GABA - gamma aminobutyric acid
GAC - granular activated carbon (treatment technology for organic compounds)
GC - gas chromatography (a laboratory method)
g/mol - grams per mole
GW - ground water
HazDat - Hazardous Substance Release and Health Effects Database
HEOD - l^J3A10,10-hexachIoro-6,7-epoxy-l,4,4a,5,6,7,8,8a-octahydro-l,4-endo,exo-5,8-
dimethanonaphthalene
HHDN -l,2,3,4,10,10-hexachloro-l,4,4a,5,8,8a-hexahydro-l,4-endo,exo-5,8-
dimethanonaphthalene
HRL - Health Reference Level
IOC - inorganic compound
Kg,. - organic carbon partition coefficient
&„„ - octanol-water partitioning coefficient
LDSO - 50% lethal dose
LOAEL - lowest observed adverse effect level
MCL - maximum contaminant level
MCLG - maximum contaminant level goal
MDL - method detection limit
mg - milligrams
MRL - minimum reporting level
MS - mass spectrometry (a laboratory method)
NAWQA - National Water Quality Assessment Program
NCI - National Cancer Institute
NCOD - National Drinking Water Contaminant Occurrence Database
NDWAC -National Drinking Water Advisory Council
NIOSH -National Institute for Occupational Safety and Health
NIRS - National Inorganic and Radionuclide Survey
nm -nanometer
NOAEL - no observed adverse effect level
51
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Preliminary Regulatory Determination Support Document for Aldrin andDieldrin
November, 2001
NPDWR
NPL
NTNCWS
OGWDW
OMB
OKD
OSHA
PWS
RCRA
RfD
SARA Tide m
SDWA
SDWIS
SDWIS/FED
SOC
SW
TPQ
TRI
UCM
UCMR
URCIS
USDA
USEPA
USGS
VOC
"g
>MCL
>MRL
- National Primary Drinking Water Regulation
- National Priorities List
- non-transient non-community water system
- Office of Ground Water and Drinking Water
- Office of Management and Budget
- Office of Research and Development
- Occupational Safety and Health Administration
- public water system
- Resource Conservation and Recovery Act
- reference dose
- Superfund Amendments and Reauthorization Act
- Safe Drinking Water Act
- Safe Drinking Water Information System
- Federal Safe Drinking Water Information System
- synthetic organic compound
- surface water
- threshold planning quantity
- Toxic Release Inventory
- Unregulated Contaminant Monitoring
- Unregulated Contaminant Monitoring Regulation/Rule
- Unregulated Contaminant Monitoring Information System
- United States Department of Agriculture
- United Steles Environmental Protection Agency
- United States Geological Survey
- volatile organic compound
- micrograms r
- percentage of systems with exceedances
- percentage of systems with detections
52
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