United States
Environmental Protection
Agency
Office of
Pesticides and Toxic Substances
Washington, DC 20460
June 1988
Pesticides
vvEPA ALDICARB
SPECIAL REVIEW
TECHNICAL SUPPORT
DOCUMENT
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- ACKNOWLEDGMENTS -
Bruce Kapner
Janet Auerbach
Jack Housenger
Bob Barles
Michael Branagan
Mark Dow
Dennis Edwards
Jim Felkel
Joel Garbus
Pat Holden
Roger Holtorf
Bruce Jaeger
Bill Jordan
Tina Levine
Matt Lorber
Amal Mahfouz
Neil Pelletier
Dorm Viviani
Ralph Wright
Review Manager
Branch Chief
Section Head
Ground Water Project Manager
Regulatory Analyst
Entomologist
Product Manager
Wildlife Biologist
Residue Chemist
Ground Water Team Leader
Benefit Assessment Team Leader
Toxicologist
Attorney
Science Staff Coordinator
Agricultural Engineer
Toxicologist
Plant Physiologist
Regulatory Analyst
IPM Specialist
(RD)
(RD)
(RD)
(OPP)
(OPPE)
(BUD)
(RD)
(EEB/HED)
(RCB/HED)
(EAB/HED)
(EAB/BUD)
(TB/HED)
(OGC)
(HED)
(EAB/HED)
(ODW)
(BUD)
(OPPE)
(IPM/BUD)
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- EXECUTIVE SUMMARY -
On July 11, 1984, the Environmental Protection Agency (the
Agency) issued a Notice of Rebuttable Presumption Against Reg-
istration (RPAR or Special Review) and Continued Registration of
Pesticide Products Containing Aldicarb (49 FR 28320). That
action was based on a finding that registrations of pesticide
products containing aldicarb met or exceeded risk criteria in 40
CFR 162.ll(a)(6)(i) which provides that a Special Review be
initiated if it appears that, "based on toxicological data,
epidemiological studies, use history, accident data, monitoring
data, or such other evidence as is available to the Admin-
istrator, the pesticide may pose a substantial question of safety
to man or the environment..."
As part of the Special Review process, the Agency evaluates
the risks and benefits associated with the use of a pesticide and
then proposes any regulatory actions necessary to assure that use
of that pesticide results in no unreasonable adverse effects.
Aldicarb is a soil incorporated carbamate pesticide that is
absorbed by plant roots. It provides systemic control of
insects, mites and nematodes. The Agency estimates that approx-
imately 5.2-5.7 million pounds of active ingredient are used
annually. Rhone-Poulenc AG Company is the sole registrant of
aldicarb and its first registration in 1970 was for use on
cotton. Aldicarb is now registered for use on: citrus, dry
beans, grain sorghum, ornamentals, pecans, peanuts, potatoes,
seed alfalfa, soybeans, sugar beets, sugarcane, sweet potatoes
and tobacco.
Aldicarb is an acutely toxic pesticide, causing reversible
cholinesterase inhibition. The oral LD50 in rats is 0.9 mg/kg.
A wide range of clinical signs in humans are related to
cholinesterase inhibition including: gastrointestinal disturb-
ances, unconsciousness, blurred vision, excessive salivation,
seizures, and disorientation. Extensive cholinesterase
inhibition may result in death. A No Observed Effect Level for
human clinical signs has been reported to be 0.05 mg/kg, with an
estimated No Observed Effect Level of 0.01 mg/kg for human
cholinesterase inhibition.
A number of reports of accidental exposures following misuse
of aldicarb indicate that cholinergic signs, even severe cholin-
ergic signs, may occur at doses below 0.1 mg/kg. Calculated
doses of 0.01-0.0026 mg/kg have been associated with these
reports. These data are anecdotal -and it is difficult to deter-
mine precise consumption, but they may indicate a broad range of
sensitivity to aldicarb»s acute effects.
Potential risks are associated with consumption of raw
agricultural commodities and drinking water contaminated with
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residues of aldicarb. Aldicarb has been detected in ground or
drinking water wells in 16 states at levels ranging from under 10
ppb to over 500 ppb. Because aldicarb residues can persist in
ground water for several years, ground water contamination by
aldicarb may be a widespread, long-term problem.
Dietary Risk from Treated Commodities
The Agency has estimated maximal dietary exposure to
aldicarb, resulting from a single exposure from legally treated
potatoes and citrus by using the upper 5 percent residues. The
Agency used data in support of tolerances submitted by the
registrant and FDA market basket survey data. The exposure
estimates were then compared against aldicarb's cholinesterase
inhibition characteristics to determine the margins of safety for
these two crops for different sectors of the population. Infants
and children consuming the treated commodity are at the highest
risk of acute aldicarb toxicity from the consumption of citrus
and potato products with as many as 55 percent of consumers of
the commodity with upper 5 percent residue levels in these sub-
populations exposed to aldicarb at an amount providing less than
a tenfold margin of safety for cholinesterase inhibition.
The Agency has encouraged pesticide registrants to conduct
monitoring studies which, it believes, will give a more accurate
representation of the level of pesticide residues to which the
public is exposed. The registrant has recently conducted a
National Food Survey for aldicarb which monitors for residues in
the market place. Preliminary results from this survey suggest
that most aldicarb residues in commodities in the market place
are at or below the limit of detection (0.01 ppm). The final
results have been submitted and, along with the tolerance data
and the FDA market basket survey data, will be used in the final
dietary risk assessment. A regulatory proposal regarding dietary
risks is being deferred pending analysis of these data.
Dietary Risk from Contaminated Drinking Water
The Agency has also estimated the percent of affected
populations receiving certain levels of exposure from consuming
drinking water, assuming different levels of aldicarb residues in
the water. The Agency has provided a margin of safety estimate
for these exposure levels. The focus of the analysis was on the
population at greatest risk, infants, because they consume most
of their diet as formula and fruit juice, both of which are
frequently prepared using tap water. The Agency has assumed that
the daily intake of drinking water will be composed of two
separate doses because it is reasonable to assume that an
individual would not consume all of the water in his/her diet at
one time. The assessment also reflects the fact that aldicarb
can cause cholinesterase inhibition by a single acute exposure
and that about six hours are required for recovery. The Agency
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calculated that when drinking water containing aldicarb at 10
ppb, as many as 13 percent of consuming infants could be exposed
to a dose of 0.001 mg/kg or greater of aldicarb. The
corresponding margin of safety for cholinesterase inhibition
would then be 10 or less, based on the No Observed Effect Level
estimated by the National Academy of Sciences.
Ground Water Risk Assessment
The Agency assessed the ground water vulnerability, or
potential for aldicarb to reach ground water, using two different
methods. The Agency looked at all ground water sources, not just
current drinking water sources, since these potential sources
could be used in the future. One method uses Heath Regions (11
hydrogeologic ground water regions of the U.S.) to identify
states as the geographical unit for regulatory purposes, and the
other method uses counties as the geographical unit.
Three major parameters were employed in the Heath Region
assessment to evaluate the ground water vulnerability of these
regions: hydrogeologic characteristics of counties, ground water
monitoring data, and crop use practices. Hydrogeologic
characteristics were evaluated by a close evaluation of 138
counties where aldicarb is used and through use of a
hydrogeologic model called DRASTIC. DRASTIC is a screening
system which estimates ground water vulnerability using seven
characteristics: depth to ground water; recharge; aquifer media;
soil media; topography; impact of the vadose zone and hydraulic
conductivity of the aquifer. Crop use practices include
cultivation methods, rate of application, and temperature for
each of the five major crops grown in a particular region.
An integrated, qualitative weight-of-evidence approach was
used with the greatest emphasis placed on actual monitoring data
when reliable and representative data were available. Major
aldicarb use crops were evaluated as to ground water vulner-
ability in regions where they are grown. The result of this
analysis is a high, medium, and low "potential to leach" ranking
for 32 crop/Heath region combinations.
The county assessment evaluated ground water vulnerability
in three ways: 1) use of actual monitoring data, 2) evaluation of
use/usage data, and 3) use of DRASTIC scores for each county.
As in the Heath Region assessment, an integrated, qualitative
weight-of-the-evidence approach was used with the greatest
emphasis placed on positive monitoring data, when available. The
result is a high, medium, or low "potential to leach" ranking for
all counties of the country. The Agency has completed this
assessment in four selected states: California, Florida, North
Carolina, and Wisconsin.
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IV
Benefits Assessment
The benefits of aldicarb use were assessed in terms of the
economic impact of cancellation on society as well as the impact
on users and consumers. Assessments were based on changes in
production costs, crop yield reductions and possible grower
shifts to other enterprises. Impacts on users were considered on
a per-unit and per-establishment basis as well as at the county
(for some uses), state, regional, and national levels.
For cancellation in all areas of the country, significant
impacts would be expected for citrus ($54.5 million for Florida
oranges and Texas grapefruit) and peanuts ($17-33 million).
Moderate economic impacts on a national level would be expected
for cotton ($20-29 million), potatoes ($11-15 million), tobacco
($0.1-0.7 million), sweet potatoes ($1.3-2.7 million) and pecans
($0.48 million). For all uses, the impacts result primarily
because alternatives are less effective than aldicarb.
Prohibition of use of aldicarb would have the greatest
impact in the southeast (citrus: $49 million, peanuts: $22
million, pecans: $0.2 million, sweet potatoes: $0.9 million, and
tobacco: $0.7 million), north central (potatoes: $1.6 million and
sugarbeets: $0.6 million), and the northwest (potatoes: $4
million).
Ground Water Strategy
The Agency recently initiated a number of long-term strat-
egies on significant environmental issues which require cross-
media coordination. One strategy under development addresses
agricultural chemicals in ground water. As part of the strategy
development process, the Agency sponsored workshops at Coolfont,
West Virginia on June 24-27, 1986 and July 23-24, 1987. The
workshop participants discussed, among other issues, regulatory
strategies to limit the amount of pesticides and fertilizers
leaching into ground water. Representatives of state health,
environmental, and agricultural offices; other Federal agencies;
industry; user groups; researchers; Cooperative Extension
Services; and environmental groups participated in those
workshops. On February 25, 1988, the Agency issued a proposed
strategy for addressing ground water contamination by agri-
cultural chemicals (Agricultural Chemicals in Ground Water;
Proposed Pesticide strategy). This document is the Agency's
proposed long-term strategic plan for protecting ground water
from contamination by agricultural chemicals and the Agency is
soliciting public comment on this plan.
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Risk/Benefit Assessment and Regulatory Options
It is the Agency's preliminary determination that on a
national basis, the risks posed by aldicarb contamination of
ground water exceed the benefits derived from aldicarbTs
continued use. Consequently, regulatory action is necessary to
prevent unreasonable adverse effects on the environment.
The Agency believes it is possible to reduce the risks
significantly by imposing certain regulatory restrictions short
of cancellation of all uses. Accordingly, the Agency evaluated
three options to prevent the contamination of the nation's ground
water by aldicarb above an unacceptable level. The Agency
believes that vulnerable areas are likely to have leaching of
aldicarb into ground water at levels greater than the Health
Advisory. These options are: 1) Risk reduction measures/user
determines applicability, 2) Labeling/monitoring/state
management plans determined by Heath Regions, and 3) Labeling/
monitoring/state management plans determined by county.
In Option 1, the registrant would be required to place
additional risk reduction measures on aldicarb labels (i.e.,
drinking water well setbacks, modifications to application rates
and timing, and monitoring requirements). Restrictions imposed
through labeling would be targeted at the users and the costs of
monitoring ground water contamination and of corrective actions
would be borne by the registrant. Preventive measures would be
tailored to specific conditions of the application site in order
to prevent contamination of drinking water wells above an
unacceptable level.
Option 2 provides states the opportunity to play an active
role in protecting ground water. This option includes three
components: labeling, monitoring and State Pesticide Ground Water
Management Plans. The labeling component consists of uniform,
national actions which would prohibit the use of aldicarb within
300 feet from any drinking water well and classify aldicarb as a
restricted use pesticide due to ground water concerns. These
measures would serve as baseline requirements in all areas where
aldicarb is used. In addition to these baseline efforts,
monitoring would be required in representative areas which have
been evaluated in the Agency's ground water assessment as having
a medium potential to leach. The data resulting from this
monitoring will be used to further characterize the medium areas
and to determine whether additional regulatory action beyond the
baseline requirements will be needed in these areas.
The most stringent measures the Agency is proposing are in
those areas identified as having the greatest potential for
aldicarb to reach ground water. The Agency believes that the
states are in the best position to regulate the use of aldicarb
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VI
to prevent/reduce unacceptable ground water contamination in the
areas of greatest concern by implementing Management Plans. The
Heath Region approach of assessing ground water vulnerability was
used in identifying 10 states where Management Plans would be
needed. These states include: Alabama, Florida, Georgia, Maine,
Michigan, Minnesota, New York, North Dakota, Pennsylvania, and
Wisconsin. Acceptable Management Plans will serve as the basis
for the continued registration of aldicarb within these states.
Option 3 is identical to Option 2 in that it would have the
same labeling and monitoring components. However, the states
that would need to develop Management Plans would be identified
using a county approach which identified counties where the
Agency believes aldicarb has the highest tendency to leaching.
Under this approach, states would need to develop and implement a
Management Plan for those counties classified as such. The
Agency has only evaluated the counties of four states using the
county approach for assessing ground water vulnerability. As a
result of this assessment, the following results were obtained:
California has 3 out of 58 counties, Florida has 26 out of 67
counties, and Wisconsin has 8 out of 72 counties needing a
Management Plan. North Carolina did not have any counties which
were ranked high enough to need the establishment of a Management
Plan. However, the vulnerability to ground water contamination
was sufficiently high in all other counties in each of these four
states to be classified as medium in vulnerability. The
registrant will be required to undertake a monitoring study that
will be representative of those moderately vulnerable areas. The
Agency anticipates that 15 to 24 states would be required to
submit plans for one or more counties if this option were chosen.
The Agency proposes Options 2 and 3 to impose label
restrictions and monitoring requirements, and to allow the use of
aldicarb in certain states/counties which have approved
Management Plans and cancel the use of aldicarb in certain
states/counties which choose not to implement Management Plans.
The Agency's proposed approach for aldicarb implements the
recently proposed long-term strategy addressing the concern of
pesticides in ground water. This aldicarb proposal uses
graduated measures in order to prevent unacceptable ground water
contamination. The extent of preventive measures required in a
specific area would depend on the area's vulnerability to such
contamination. The most stringent prevention measures would be
required in those areas where there is the greatest potential for
unacceptable levels of ground water contamination by aldicarb.
The Agency believes that Management Plans are the best way
to prevent ground water contamination without subjecting areas
where contamination is less likely to occur to unnecessarily
stringent regulatory controls. The Agency believes that, in
areas without Management Plans, certain restrictions on the use
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VI1
of aldicarb are necessary to reduce the risks of ground water
contamination to acceptable levels. These restrictions would be
incorporated through labeling on all aldicarb products. The
Agency also believes that further monitoring data would improve
its ability to predict the likelihood of the contamination of
ground water in medium vulnerability areas and is imposing
monitoring data requirements for these areas. The Agency is
seeking public comment and preferences in selecting state or
county level Management Plans.
Additionally, the Agency is seeking comments on other issues
which are pertinent to the proposed regulatory action. These
issues include: 1) content of national labels, 2) design of
monitoring protocols, 3) conduct of local risk/benefit assess-
ments, 4) involvement in refining ground water contamination
assessments, 5) involvement of the registrant in developing the
Management Plans, and 6) design of Management Plans.
A further unresolved issue concerns who should be respons-
ible for remedial action (e.g. developing, approving, and
implementing corrective action plans such as funding clean-up
costs or providing an alternative water supply) when ground water
is contaminated by a registered pesticide use. The document
Agricultural Chemicals in Ground Water; Proposed Pesticide
Strategy discusses this issue in more detail. Since this is a
generic issue which pertains to all pesticides which leach rather
than just to aldicarb, any comments regarding this issue should
be made in response to the above document.
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VI11
TABLE OF CONTENTS
CHAPTER I
ENTRODUCTION 1-1
A. GJ&NHIKAL BACKGROUND AND ORGANIZATION I —1
B. LEGAL BACKGROUND 1-2
1. THE STATUTE 1-2
2. THE SPECIAL REVIEW PROCESS 1-2
C. CHEMICAL BACKGROUND 1-3
1. CHEMICAL AND PHYSICAL CHARACTERISTICS OF
ALDICARB 1-3
2. REGISTERED USES AND PRODUCTION 1-3
3. TOLERANCES 1-4
CHAPTER II
RISK ASSESSMENT AND ANALYSIS OF PUBLIC COMMENTS II-l
A. DIETARY RISK ASSESSMENT II-l
1. TOXICOLOGY SUMMARY II-l
a. Laboratory Studies II-2
1) Animal Studies II-2
2) Human Studies II-3
3) Conclusions II-3
b. Other Data II-4
1) Human Incidents II-4
2) Epidemiology Studies II-4
3) Conclusions II-5
2. EXPOSURE ASSESSMENT FOR TREATED FOOD
COMMODITIES II-5
a. Description of the Tolerance Assessment
System II-6
1) Food Consumption Data Files . . . II-6
2) Residue Data Files II-6
b. Exposure Estimates » II-7
1) Population Consuming Citrus and
Potatoes II-7
2) Percent of Crop Treated II-8
3) Crop Residues II-8
3. CONTAMINATED GROUND WATER 11-10
a. Background Information 11-10
b. Exposure Estimates 11-10
1) Water Residues 11-10
2) Processing Factors 11-11
4. RISK ASSESSMENT 11-11
a. Introduction 11-12
b. Toxicology Endpoints 11-12
c. Risk from Food Residues * . . 11-12
1) Oranges 11-13
2) Grapefruit 11-13
3) Potatoes 11-13
d. Risks from Contaminated Drinking Water 11-13
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e. Conclusions 11-18
B. GROUND WATER VULNERABILITY ANALYSIS 11-18
1. ENVIRONMENTAL FATE 11-19
a. Leaching Potential 11-19
b. Metabolism and Degradation 11-19
2. GROUND WATER ASSESSMENT 11-20
a. Ground Water Assessment by Heath Region 11-20
1) Hydrogeologic Vulnerability .... 11-23
2) Monitoring Data Evaluation .... 11-25
3) Crop/Site-Specific Correlation
Approach 11-32
4) Results of Integrated Ground Water
Assessment by Heath Region .... 11-33
b. Ground Water Assessment by County . . . 11-34
1) DRASTIC Analysis 11-34
2) Use and Usage 11-37
3) Monitoring Data Assessment .... 11-38
4) Results of Integrated Ground Water
Assessment by County 11-39
CHAPTER III
BENEFITS SUMMARY III-l
A. INTRODUCTION III-l
B. ANALYSIS OF INDIVIDUAL COMMODITIES AND
ALTERNATIVES III-3
1. COTTON III-3
2. POTATOES III-4
3. CITRUS III-4
4. PEANUTS III-6
5. SOYBEANS III-7
6. SUGAR BEETS III-8
7. PECANS III-9
8. TOBACCO III-9
9. SWEET POTATOES 111-10
10. ORNAMENTALS III-ll
11. SEED ALFALFA 111-13
12. GRAIN SORGHUM 111-13
13. DRY BEANS 111-14
14. SUGARCANE 111-14
C. CONCLUSIONS 111-14
CHAPTER IV
REGULATORY OPTIONS AND RISK/BENEFIT ANALYSIS IV-1
A. INTRODUCTION IV-1
B. RISK SUMMARY IV-1
1. RISKS FROM TREATED COMMODITIES IV-2
2. RISKS FROM CONTAMINATED DRINKING WATER . . . IV-2
C. BENEFITS SUMMARY IV-3
D. ANALYSIS OF ALTERNATIVE PESTICIDES IV-3
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E. PUBLIC fOMMKiyr CONCLUSIONS IV-6
F. REGULATORY OPTIONS IV-7
1. PROTECTING GROUND WATER IV-7
OPTION 1 - RISK RKnTTCTTQyf MKASURES/USER DETERMINES
APPLICABILITY IV-8
a. Drinking Water Well Setbacks IV-8
b. Application Rate, Frequency, and Timing
Modifications IV-10
c. Monitoring IV-11
d. General Restrictions IV-11
OPTION 2 - T.ATHJT.ING/MONITORING/STATE MANAGl^MFTyr PLANS
DETERMINED BY HTCATH REGIONS IV-11
1. LABELING COMPONENT IV-11
2. MONITORING COMPONENT IV-12
3. STATE PESTICIDE MANAGEMENT PLAN COMPONENT . . IV-13
OPTION 3 - T.ARKT.ING/MONITORING/STATE MANAGFTMITiyr PLANS
DETERMINED BY COUNTY IV-16
G. RISK/BENEFIT ANALYSIS OF REGULATORY OPTIONS . . . IV-17
1. INTRODUCTION IV-17
2. DIETARY EXPOSURE TO ALDICARB RESIDUES IN
TREATED COMMODITIES IV-17
3. DIETARY EXPOSURE TO CONTAMINATED GROUND WATER IV-18
a. Introduction IV-18
b. Discussion of Ground Water Options . . . IV-21
1) Option 1 - Risk Reduction
Measures/User Determines
Applicability IV-21
2) Option 2 - Labeling/Monitoring/State
Management Plans Determined by Heath
Region IV-22
3) Option 3 - Labeling/Monitoring/State
Management Plans Determined by
County IV-26
H. PROPOSED ACTIONS IV-26
CHAPTER V
BIBLIOGRAPHY V-l
APPENDIX I
LIST OF REBUTTORS i-1
APPENDIX II
STATE MANAGEMENT PLAN GUIDELINES ii-1
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LIST OF TABLES AND MAPS
TABLE II-l - Percent of and MOS for Affected Populations
Consuming Average Residues 11-14
Table II-2 - Percent of and MOS for Affected Populations
Consuming 95 Percent Confidence Level Residues 11-15
TABLE II-3 - Percent of and MOS for Affected Populations
Consuming Water from All Dietary Sources 11-16
TABLE II-4 - Aldicarb Monitoring Results - Summaries
by State 11-28
TABLE II-5 - Suffolk County Department of Health
Monitoring of Impacted Wells, 1980-1985 11-30
TABLE II-6 - Ground Water Vulnerability 11-35
TABLE II-7 - County Assignments 11-41
TABLE II-8 - Final Results of County Assessment 11-42
TABLE III-l - Summary of Aldicarb Benefits by Site .... III-2
TABLE IV-1 - Toxicology of Aldicarb and its
Alternatives , IV-4
MAP II-l - Ground Water Regions of the United States . . . 11-21
MAP II-2 - Aldicarb Crop/Region Combinations 11-22
MAP II-3 - DRASTIC Evaluation of the United States .... 11-26
MAP II-4 - Final Results of Aldicarb Integrated
Assessment 11-36
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INTRODUCTION
A. GENERAL BACKGROUND AND ORGANIZATION
On March 30, 1984, the Environmental Protection Agency (the
Agency) issued its requirements for the interim registration of
pesticide products containing aldicarb in the Aldicarb Reg-
istration Standard. On July 11, 1984 (49 FR 28320), the Agency
initiated a Special Review of aldicarb because aldicarb appeared
to meet or exceed the risk criteria in 40 CFR 162.11(a)(6). That
section provides that a Notice of Intent to Cancel the registra-
tion of a pesticide may be issued if "... based on toxicological
data, epidemiological studies, use history, accident data,
monitoring data, or such other evidence as is available to the
Administrator, the pesticide may pose a substantial question of
safety to man or the environment...." The basis of the aldicarb
Special Review is the potential for unreasonable adverse effects
to humans from dietary exposure to drinking water from ground
water wells contaminated with aldicarb. The use of aldicarb has
led to ground water contamination in 50 counties of 16 states,
with contamination ranging to 515 ppb.
This Aldicarb Technical Support Document (TSD) reiterates
the basis for initiating the Special Review stated in Position
Document 1 (PD 1) and describes the Agency's proposed regulatory
actions to reduce the potential adverse effects from aldicarb.
Aldicarb is one of the most acutely toxic pesticides
registered. It is a potent cholinesterase (ChE) inhibitor,
causing reversible inhibition of erythrocyte acetylcholin-
esterase (red blood cell ChE) as well as plasma butyryl ChE.
Acetylcholinesterase is an enzyme necessary for transmission of
impulses at nerve synapses. Sufficient inhibition of these
enzymes can result in serious toxic effects, including death.
Data indicate that aldicarb does not cause chronic effects and
that acute cholinesterase inhibition is the only toxicologically
significant effect.
The Agency has reviewed crop residue data to evaluate
potential exposure to residues of aldicarb and its metabolites
in treated commodities. The Agency also reviewed environmental
fate and monitoring data to determine the potential for and
magnitude of exposure via consumption of ground water.
The TSD contains five chapters. Chapter I is this intro-
duction and provides general background information on the
pesticide. Chapter II describes estimates of human and environ-
mental risk from use of aldicarb and its principle alternatives,
including descriptions and evaluations of the risk information,
responses to public comments to the PD 1, as well as the risk
conclusions. Chapter III discusses the quantitative estimates of
the benefits of use of registered aldicarb products on various
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crops, describes the major alternatives, and describes the
assumptions/limitations of these estimates, as well as the
benefits conclusions. All public comments associated with
benefits information are incorporated into the benefit analysis
chapter. Chapter IV describes the possible regulatory options to
reduce the risk from use of aldicarb, evaluates the impacts on
risks and benefits of aldicarb under these regulatory options,
and recommends a specific combination of actions. Chapter V is
the bibliography.
B. LEGAL BACKGROUND
1. THE STATUTE
A pesticide product may be sold
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1-3
Information concerning risks is evaluated and considered in
light of the information on the benefits of the pesticide. If the
Agency determines that risks outweigh benefits, the Agency can
initiate action under FIFRA to cancel, suspend, or require
modification of the terms and conditions of registration.
C. CHEMICAL BACKGROUND
1. CHEMICAL AND PHYSICAL CHARACTERISTICS OF ALDICARB
Aldicarb is the common chemical name for [2-methyl-2-
(methylthio)propionaldehyde-0-(methylcarbamoyl)oxime]. Trade
names include: Temik 10G, Temik 15G and Temik TSX. Aldicarb
sulfone, a related chemical, is also registered under the trade
name Aldoxycarb. Aldicarb sulfone is approximately 20 times
less toxic than aldicarb. Aldicarb sulfone is considered in this
Special Review because aldicarb sulfone is a degradate of parent
aldicarb in treated commodities and ground water.
Pure aldicarb is a white crystalline solid with a melting
point of 98-100° C. Under normal conditions, aldicarb is a heat
sensitive, inherently unstable chemical and must be stabilized to
obtain an extended shelflife.
2. REGISTERED USES AND PRODUCTION
There are five FIFRA §3 Federal registrations and 11 intra-
state registrations for aldicarb. Rhone-Poulenc AG Company is
the sole producer and registrant of aldicarb products. Aldicarb
was originally produced and registered by the Union Carbide
Agricultural Products Company, Inc. which sold its interests in
aldicarb to Rhone-Poulenc. (Hereafter Rhone-Poulenc and Union
Carbide are referred to as "the registrant".)
Aldicarb is a restricted-use pesticide that may be purchased
and used only by certified applicators or individuals under the
direct supervision of certified applicators.
Technical aldicarb is formulated into and sold as 5 percent,
10 percent and 15 percent active ingredient (a.i.) granular end-
use products. These end-use products are incorporated into soil
either at planting, at emergence or, in the case of established
trees, at first foliage flush and used for control of a variety
of insects, mites, and nematodes. Major sites of aldicarb usage
include: citrus, cotton, potatoes, peanuts, and soybeans. Aldi-
carb is also used on sugar beets, tobacco, ornamentals, sweet
potatoes, dry beans, pecans, sugarcane, seed alfalfa (California
only) and grain sorghum.
Approximately 5.2 to 5.7 million pounds a.i. of aldicarb are
used annually in the U.S.
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3. TOLERANCES
Tolerances have been established for aldicarb and its ChE
inhibiting metabolites under 40 CFR 180.269. A list of these
tolerances follows.
U.S. ALDICARB TOLERANCES
Crop
Maximum Residue
Limit (ppm)
Bananas 0.3
Beans (dried) 0.1
Beets, sugar 0.05
Beets, sugar, tops 1.0
Cattle, fat 0.01
Cattle, meat by-
products 0.01
Cattle, meat 0.01
Coffee 0.1
Cottonseed 0.1
Goats, fat 0.01
Goats, meat by-
products 0.01
Goats, meat 0.01
Grapefruit 0.3
Hogs, fat 0.01
Hogs, meat by-
products 0.01
Hogs, meat 0.01
Horses, fat 0.01
Horses, meat by-
products 0.01
Horses, meat 0.01
Crop
Maximum Residue
Limit (ppm)
Lemons 0.3
Limes 0.3
Milk 0.002
Oranges 0.3
Peanuts 0.05
Peanuts, hulls 0.5
Pecans 0.5
Potatoes 1.0
Sheep, fat 0.01
Sheep, meat by-
products 0.01
Sheep, meat 0.01
Sorghum, fodder 0.5
Sorghum, grain 0.2
Soybeans 0.02
Sugarcane 0.02
Sugarcane, fodder 0.1
Sugarcane, forage 0.1
Sweet Potatoes O.l
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CHAPTER II
RISK ASSESSMENT AMI) ANALYSIS OF PUBLIC C.pMMT?MTS
Tnis chapter is composed of three parts. The first part
describes the Agency's assessment of human health risk from the
consumption of treated food commodities and contaminated drinking
water containing residues of aldicarb and its metabolites. The
second part describes the Agency's assessment of the ground water
contamination data for aldicarb as well as the vulnerability of
ground water to contamination. The last part of this chapter
addresses all rebuttal comments submitted in response to the
Position Document 1 (PD 1).
A. PIETARY RISK ASSESSMETNT
This section describes the Agency's conclusions about
dietary risk. The section is composed of four subsections:
toxicology, exposure to treated food commodities, exposure to
contaminated ground water, and a risk assessment. The Agency's
assessment of the data base on oncogenicity, teratogenicity,
reproductive effects, and mutagenicity have been discussed in the
Registration Standard and PD 1 and therefore will not be pre-
sented again in this document.
1. TOXICOLOGY SUMMARY
The Agency examined the entire toxicology review file during
both the preparation of the Registration Standard and this
Technical Support Document. The Agency concluded from these data
that aldicarb has not been shown to cause immunologic, oncogenic,
teratogenic, reproductive or mutagenic effects in laboratory
animals.
Additionally, the Agency has reviewed a study in which the
Centers for Disease Control (CDC) and the Wisconsin Division of
Health (Fiore, et al, 1986), examined the association between
immune function and aldicarb contaminated ground water. This
.involved a cross sectional study of 50 women who were thought to
be free from other primary risk factors for altered immune
function. Although the Agency believes the results of this study
are of some interest, it believes the clinical significance of
the reported difference in T lymphocytes and Candida response is
highly questionable. The T data fall within the normal range as
indicated by Marti, et al (1985). The Candida response data are
also within normal limits that have been routinely observed at
the University of Wisconsin Medical Center. The results of this
study present no evidence for a causal relationship between
consumption of water contaminated with aldicarb and dysfunction
of the immune system.
The Agency believes the only reliably demonstrated toxic
effect of aldicarb is acute cholinesterase (ChE) inhibition. A
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discussion of the studies available which demonstrate this
effect are presented belov.
a. Laboratory Studies
1) Animal Studies
The Agency reviewed over 50 metabolism and acute toxicity
studies during the "preparation of the Registration Standard (EPA,
1984). These studies indicate that aldicarb is rapidly absorbed
by mammals and metabolized to aldicarb sulfoxide, the major
metabolite. Aldicarb sulfoxide is subsequently and more slowly
degraded to aldicarb sulfone. All three compounds inhibit red
blood cell (RBC) and plasma cholinesterase (ChE) with aldicarb
sulfoxide the most potent ChE inhibitor. The rapid conversion in
animals of aldicarb to aldicarb sulfoxide and subsequent rapid
ChE drop is probably responsible for the acute toxic reaction
associated with aldicarb. All metabolites are rapidly and
completely eliminated from the body, with 80 to 90 percent
excreted within 24 hours, leaving no detectable residues by the
fifth day. Data demonstrate that aldicarb is not stored in body
tissues. Both RBC and plasma ChE are restored to normal levels
within six hours after exposure to a single dose.
Aldicarb is very highly toxic to mammals by oral exposure.
The lower acute oral toxicity of the formulations reflects the
reduced concentration of aldicarb as formulated on the granular
material. The oral LD50Ts of aldicarb and its principal
metabolite, aldicarb sulfoxide, are similar (0.9 mg/kg), while
aldicarb sulfone (oral LD5Q of 24 mg/kg) is less toxic than
aldicarb. The other aldicarb metabolites are considerably less
toxic, with LDso's ranging between 350 mg/kg (aldicarb sulfone
nitrile) to greater than 15,000 mg/kg (amide derivative). The
dose-effect curve for aldicarb can be extremely steep. For
example, Maripot, et al. (1980) administered aldicarb in corn
oil, P.O., to fasted rats and found that the lowest dose
producing clinical signs, 0.1 mg/kg, also killed two of the 10
rats.
The registrant has submitted two monkey studies (Union
Carbide, 1987a and 1987b). In these studies, 12 monkeys consumed
either bananas or watermelons (six monkeys/fruit) containing
aldicarb to obtain a dose of 0.005 mg/kg. No clinical signs of
toxicity were observed. However, plasma ChE and, to a lesser
extent, RBC ChE was inhibited at this low dose.
The toxicity of aldicarb when injected intraperitoneally or
intravenously is almost the same as when it is given orally,
suggesting rapid absorption into the body when aldicarb is
ingested. The Agency's evaluation of the dermal LDso's indicates
that aldicarb (5 mg/kg), aldicarb sulfoxide (greater than 20
n»g/kg) and aldicarb sulfone (greater than 20 mg/kg) are less
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toxic dermally than by the oral route, but still highly toxic.
The Agency's evaluation of the inhalation toxicity of aldicarb
indicates that, while extremely toxic when inhaled, aldicarb does
not vaporize at ambient temperatures and thus does not produce
toxic vapors. There is no appreciable inhalation exposure from
application (i.e., it is not sprayed) or from dietary con-
sumption.
2) Human Studies
A wide range of clinical signs in humans are related to ChE
inhibition including: gastrointestinal disturbances, uncon-
sciousness, blurred vision, excessive salivation, seizures, and
disorientation. Extensive ChE inhibition may result in death.
The Agency evaluated a human study performed by the reg-
istrant (Dernehl and Block, 1971). Four men per dose each
consumed a single dose of 0.025, 0.05, and 0.1 mg/kg (body
weight) aldicarb in 100 ml of water. The high dose produced
clear, spontaneously reversible, clinical signs (i.e., blurred
vision and nausea) and ChE inhibition (54-86 percent inhibition).
The middle dose produced no clinical signs, but produced ChE
inhibition (52-70 percent inhibition). The lowest dose produced
no clinical signs, but also inhibited ChE (35-54 percent inhib-
ition) . These were measured in whole blood.
The Agency determined that the LOEL and NOEL for clinical
signs in this study are 0.1 mg/kg and 0.05 mg/kg, respectively.
The LOEL for ChE inhibition in this study is 0.025 mg/kg. The
National Academy of Sciences (NAS) extrapolated a NOEL for whole
blood ChE inhibition of 0.01 mg/kg from this study. The Agency
is using the NAS calculation of the NOEL for whole blood ChE
inhibition.
In another human study (Cope and Romine, 1973), two men were
each given a single dose of 0.5 and 0.26 mg/kg aldicarb in water.
The higher dose caused severe clinical signs, requiring the
administration of atropine, indicating again the steepness of the
dose-effect curve.
3) Conclusions
The Agency has concluded that aldicarb is an extremely
potent ChE inhibitor. The precipitous drop in ChE levels
resulting from exposure to aldicarb is the principle cause of the
toxic effects. The dose-effect curve for aldicarb is very steep
with little distance between the dose causing no clinical signs
or mild clinical signs and those causing severe clinical signs.
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b. Other Data
1) Human Incidents
There are a number of reports of accidental exposures
following misuse of aldicarb products. In 1966, a woman ate
approximately 0.5 to 1.0 gm of mint leaves from a plant growing
near an aldicarb treated rosebush. She developed severe clinical
signs, but recovered completely after administration of atropine.
Analysis of unconsumed mint samples contained up to 318 ppm of
aldicarb.
In 1977 and 1978, two separate incidents occurred in which
14 people exhibited clinical signs of ChE inhibition after
ingestion of local, hydroponically grown cucumbers which were
illegally treated with aldicarb. No patient received specific
medical treatment and all recovered quickly and completely.
Analysis indicated that the cucumbers contained 6.6 to 10.7 ppm
of aldicarb.
In 1985, the Canadian Department of Health and Welfare
reported 13 cases of people who showed clinical signs of ChE
inhibition following the consumption of local, hydroponically
grown cucumbers. Contamination of the cucumbers ranged from
0.156 to 8 ppm of aldicarb.
The largest documented episode of foodborne pesticide
poisoning in North American history occurred in July 1985 from
aldicarb contaminated California watermelons. More than a
thousand probable cases were reported from California, Oregon,
Washington, Alaska, Idaho, Nevada, Arizona and Canada. The
spectrum of illness attributed to aldicarb ranged from mild to
severe and included cases of grand mal seizures, cardiac
arrhythmias, severe dehydration, bronchospasms, and at least two
stillbirths occurring shortly after maternal illness. The prompt
embargo of watermelons on July 4, 1985 abruptly terminated the
major portion of the outbreak and reported illnesses occurring
after the implementation of the watermelon certification program
were far fewer and milder in comparison to earlier cases.
Contamination of the watermelons ranged up to 3.3 ppm of aldicarb
sulfoxide (ASO) (Goldman and Jackson, 1986).
2) Epidemiology Studies
The Agency reviewed a 1979 epidemiological study conducted
in Suffolk County, New York (Whitlock et al, 1982). An initial
association between diarrhea in children under 12 and consumption
of aldicarb contaminated drinking water was not confirmed upon
reexamination with an expanded population size. Interviews of
emergency room personnel and local physicians revealed no
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II-5
evidence of symptomology associated with aldicarb residues in
drinking water or food commodities.
A second epidemiology study in Long Island, New York (Varma
et al, 198?) attempted to support an association between
spontaneous abortions and exposure to aldicarb contaminated
drinking water. The Agency, however, concluded that there were
specific problems concerning the design and conduct of this study
and therefore no valid conclusions could be made.
3) Conclusions
The doses estimated from the human incidents reported have
been as low as 0.0026 mg/kg body weight. These estimates are
based largely on anecdotal data on consumption, and rarely have
analyses for aldicarb been done on the items consumed. Thus
there is considerable uncertainty regarding these estimated
doses. The human study reported above (Dernehl and Block, 1971),
which found a LOEL and NOEL for clinical signs of 0.1 mg/kg and
0.05 mg/kg, respectively, was based on four subjects per dose.
Thus, there is some uncertainty regarding these values as well.
The frequency of dose estimates from incidents that are at least
an order of magnitude lower than the 0.1 mg/kg LOEL reported
indicates that the true LOEL for clinical signs is probably lower
than this, and that the NOEL reported by Dernehl and Block could
well be an effect level for some individuals. The NOEL for ChE
inhibition extrapolated from this study, 0.01 mg/kg, may also be
high, as monkeys fed 0.005 mg/kg aldicarb had slightly depressed
ChE (Union Carbide, 1987a and 1987b); no clinical signs were
reported at this dose under controlled laboratory conditions.
Although there is uncertainty about the NOEL and LOEL for humans
based on the available data, the Agency believes that the NOELs
for ChE inhibition and clinical signs of such inhibition are
close to 0.01 mg/kg; and that at 0.001 mg/kg, it is unlikely that
many individuals will show clinical signs or have depressed ChE
activity.
2. EXPOSURE ASSESSMENT FOR TREATED FOOD COMMODITIES
The Agency has reviewed the entire residue chemistry and
environmental fate data base of aldicarb and concluded that the
two principal routes of exposure are consumption of legal
residues on treated commodities and drinking contaminated ground
water. Considering the acute nature of potential intoxication by
consumption of aldicarb residues, the Agency determined that a
single dose exposure is the exposure of concern* Hence, all
discussions of exposure will focus on the upper end estimate of
a single dose exposure.
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a. Description of the Tolerance Assessment System
The Agency estimated exposure to aldicarb treated commod-
ities utilizing the Tolerance Assessment System (TAS). TAS
estimates of dietary exposure to pesticide residues on a treated
commodity are based on food consumption and residue data files.
A brief description of each of these files is presented below.
1) Food Consumption Data Files
Food consumption estimates were derived from the 1977-78
Nationwide Survey of Food consumption, conducted by the U.S.
Department of Agriculture. These consumption estimates were
generated for specific food items, i.e., pizza, apple pie, etc.
However, tolerances are established for Raw Agricultural Commod-
ities (RACs) as they enter commerce, e.g., apples, milk and beef,
but not for apple pie or pizza. Therefore, a USDA survey food
item was broken down into its component parts (raw agricultural
commodities or RACs) i.e., apple pie was translated into wheat,
apples, sugar, etc. The composition of each food was determined
as a percentage by weight of appropriate RACs. Wherever
possible, the form of the food "as eaten" i.e., cooked, raw,
fried, etc., was noted.
Each survey respondent's consumption of each food (or food
form) was adjusted by their self-reported body weight, so that
all consumption estimates are expressed as grams of food per
kilogram body weight per day (g/kg/day). Each person»s food
record is also associated with demographic and socio-economic
information about that person (age, sex, ethnic origin, region of
the country, season surveyed, pregnant or nursing).
2) Residue Data Files
There are two principal types of residue data used by TAS:
tolerances and anticipated residues. The tolerance is used by
FDA to tell whether there are illegal residue levels. The tol-
erance represents a level of residue that is not expected to be
exceeded if the pesticide is properly used, and in fact, is a
level unlikely to be encountered on food as it is eaten.
Although the tolerance is not intended to reflect expected levels
of the pesticide in foods at the time of consumption, it is used
to estimate an upper limit of potential dietary exposure to
pesticides.
The value selected for the tolerance also does not consider
the effects of processing on residue levels. Food is generally
processed in some manner prior to consumption. Examples of
processing include: discarding outer leaves, rinsing, cooking,
freezing, canning, refining food oils, etc. These processing
procedures generally lower the amount of pesticide residue in
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II-7
food, although the proportion of parent chemical or toxic
metabolite may remain constant or increase with processing for
some pesticides and some methods of processing.
b. Exposure Estimates
The Agency initially estimated exposure to treated food
commodities in a screening process. These estimates assumed that
all appropriate treated food commodities contained aldicarb
residues at the tolerance level, and that 100 percent of the crop
was treated with no correction for concentration/reduction of
residues during processing. Only two treated commodities, citrus
and potatoes, that required a further, more refined analysis were
identified during this process. All other treated food commod-
ities had a sufficiently low exposure to be of insignificant
dietary concern. The Agency does not expect any concentration of
residues by processing that would result in elevated residues.
The Agency then performed the more refined estimate of
exposure by using the Detailed Acute Analysis function of the
TAS. When the toxicological issue of concern is based on studies
in which exposure is acute, food consumption estimates must be
for "users only" (i.e., the number of people who would consume a
particular commodity on a given day). The estimate must also be
for the amount of food ingested on a given occasion and not the
average consumption over a lifetime, as would be the case for an
estimate of chronic consumption. It is possible to estimate the
distribution of acute exposure within the population using TAS.
TAS estimates the percentage of an entire population, as well as
selected subpopulations, consuming treated commodities (citrus or
potatoes).
1) Population Consuming Citrus and Potatoes
The Agency's estimates of the percentage of people (both in
the general population and certain subpopulations) consuming
citrus and potatoes on a typical day, based on FDA market basket
data, are presented below.
Percent Consuming:
Population Citrus Potatoes
General Pop.
Infants
Children
Adult Males
Adult Females
45.0
19.9
42.6
47.0
44.0
56.2
38.3
60.0
52.4
59.5
As previously discussed, TAS can estimate the percentile of
subpopulations that consume various quantities of treated
commodities, in this case citrus and potatoes. Assuming that
these commodities contain a defined amount of aldicarb residues.
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II-8
the Agency can estimate the size of subpopulations that consume
various quantities of aldicarb residues. TAS estimates of sub-
population sizes are, however, stated as percentiles. Thus, the
estimates of subpopulation size are stated as: "x percent of the
infant subpopulation are exposed to greater than or equal to y
mg/kg of aldicarb residue via consumption of treated citrus
containing 95 percent confidence level, upper 5 percent
residues".
2) Percent of Crop Treated
i. Citrus
Aldicarb is registered for use on four citrus commodities:
oranges, grapefruit, lemons and limes. Oranges and grapefruit
constitute the vast majority of annual citrus production. The
Agency's analysis uses only orange and grapefruit data from
Florida for the following reasons. The four citrus commodities
are grown in Florida, Texas and California/Arizona with only
Florida and Texas using aldicarb in citrus production. Only a
minor amount of aldicarb (less than 1,000 Ibs a.i./yr) is used in
California/Arizona. Limes, grown only in Florida, and Texas-
grown oranges and grapefruit each represent only 1 percent or
less of the national annual citrus production.
Usage of aldicarb on Florida citrus is concentrated on fruit
for the fresh market. About 25 percent of all Florida oranges
for processing are treated with aldicarb and about 89 percent of
all Florida fresh oranges are treated. Approximately seven
percent of Texas grapefruit and 90 percent of Florida grapefruit
are treated with aldicarb.
Florida oranges and grapefruit represent approximately 72
and 81 percent, respectively, of national orange and grapefruit
production. Thus, the Agency's citrus analysis covers the
majority of citrus.
ii. Potatoes
Eleven states produce approximately 97 percent of all U.S.
grown potatoes. The Agency estimated the percent of crop treated
for the nation and found that in 1986, 23 percent of the total
U.S. potato acreage was treated with aldicarb.
3) Crop Residues
The Agency believes that "average" residue values are inap-
propriate to estimate aldicarb exposure because aldicarb causes
acute effects from a single exposure of sufficient magnitude.
Therefore, the Agency used 95 percent confidence limit values of
the anticipated residues derived from field trial data and
residue reduction (processing) data in the TAS analysis. These
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II-9
data, submitted by the registrant, were used to support toler-
ances. A 50 percent reduction factor was applied to potatoes and
certain citrus commodities, based on the average loss of aldicarb
residues during processing (cooking).
The registrant also submitted additional residue data on
citrus and potatoes for the Special Review. These data essen-
tially parallel data submitted in connection with the pesticide
tolerance petitions.
The Agency used the following 95 percent confidence limit
residue values to calculate the exposure used in the food com-
modity risk analysis:
* Citrus - 0.18 ppm
* Citrus (processed) - 0.09 ppm
* Potatoes - 0.82 ppm
* Potatoes (processed) - 0.41 ppm
The calculated residue level for potatoes reflects only
those data used to establish the current tolerance of 1 ppm. The
registrant submitted additional residue data from continuing
field trials indicating average residue values which are lower
than those determined from review of the tolerance petition data.
These new data reflect pre-harvest intervals (the period between
treatment and harvest, "PHI") longer than those approved on the
label. Under optimal conditions, early varieties of potatoes can
be harvested 90 days after planting. Aldicarb is applied either
at planting or at emergence, resulting in either a 90 day or 50
day PHI, respectively. The registrant selected samples at PHl's
ranging from 79 to 246 days, with many samples collected between
110 to 246 days after application. Collection of samples at
these times skews the residues to lower values. For comparison,
the 95 percent confidence level residue for the registrant's new
data is 0.43 ppm for unprocessed potatoes.
Additionally, the Agency reviewed market basket survey data
from the Food and Drug Administration (FDA). The data base
included 491 raw agricultural commodity samples analyzed for
aldicarb residues. Seventy-six samples were found to contain
aldicarb residues (72 white potatoes, 2 sweet potatoes, 1 peach,
1 collard green, and 1 for an unspecified Hawaiian commodity).
The 72 white potatoes with detectable levels represent 40 percent
of the 180 white potatoes sampled in the survey. Two of the
white potato samples had residue values exceeding the tolerance
and were seized by FDA.
A review of the data reveals that detectable residues were
high in 1983 and started to drop in 1984. This latter observ-
ation may be associated with the small sample size in 1984 and
1985. The majority of the FDA potato samples were taken in 1983
(142 samples). Thirty-three potato samples were taken in 1984,
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11-10
and five in 1985. The mean and 95 percent confidence level
residues of positive samples in potatoes are 0.2 ppm and 0.72
ppm, respectively. This corresponds very well to the mean and 95
percent confidence level residues calculated from pesticide
petitions, 0.22 ppm and 0.82 ppm, respectively. Thus, the market
basket survey data support the conclusion that the registrant's
recent data are unrepresentative of actual residue levels likely
to occur.
The Agency has encouraged pesticide registrants to conduct
monitoring studies to give a more accurate representation of the
level of pesticide residues to which the public is exposed. The
registrant has recently submitted the_results of a National Food
Survey which monitored for residues of aldicarb in the market
place. These data are currently under review. These data, along
with the tolerance data and the FDA market basket survey data,
will be used in the final dietary risk assessment.
3. CONTAMINATED GROUND WATER
a. Background Information
The Agency estimated exposure to ground water contaminated
with aldicarb using the TAS by considering water as if it were
another treated commodity. Unlike exposure to treated commod-
ities which are distributed throughout the nation in a reasonably
uniform fashion, contaminated ground water is a highly localized
phenomenon. Because it is impossible or impractical to sample
all ground water, the Agency cannot, as it did with treated
commodities, estimate the maximum proportion of the population
who could be exposed to aldicarb residues in ground water.
Exposure to aldicarb contaminated ground water would most likely
occur in those areas where there is a high vulnerability to
leaching.
b. Exposure Estimates
The Agency's estimate of exposure to contaminated ground
water represents, as with treated commodities, a range of
exposure levels dependent on consumption patterns. This range of
estimated exposures occur because infants, children and adults
(1) consume differing quantities of water in their foods (infants
have essentially an entire liquid diet while adults have both a
liquid and solid food diet), (2) the consumed water may be
treated differently (cold water vs. warm, formula vs. hot coffee)
and (3) personal preferences (sipping all day vs. consuming the
entire quantity at one time).
1) Water Residues
No comprehensive collation of all water samples analyzed for
aldicarb residues has been compiled to-date. However, the Agency
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11-11
developed a distribution of aldicarb residues in 7,809 wells in
Suffolk County, Nev York, in 1981 from data supplied by the
Suffolk County Health Department (Baier and Moran, 1981).
Approximately 25,000 of the over 35,000 water samples, taken
nationally over the years, are from Long Island. All wells in
this survey were within 2,500 feet of potato fields and thus,
represent an area of intensive potato cultivation and aldicarb
use. Additionally., these areas are highly vulnerable to ground
water contamination by aldicarb.
Approximately 74 percent of all the Suffolk County wells
sampled in 1981 contained no detectable aldicarb residues.
Twenty-seven percent of the wells (2,054 samples) were positive.
Fifty-six percent (1,158 samples) of the 2,054 positive samples
ranged from 1 to 10 ppb, 40 percent (815 samples) ranged from 11
to 100 ppb and 4 percent (81 samples) greater than 100 ppb.
Historic information on well contamination in general was also
provided in a separate section of this survey. Five of 68 tested
public wells contained aldicarb residues above 7 ppb. Sixty-seven
of 274 school and commercial establishment wells contained
aldicarb residues, with 22 wells exceeding 7 ppb. The vast
majority of all wells tested to date contain levels of aldicarb
residues of less than 10 ppb.
2) Processing Factors
Aldicarb degrades from heat, especially the high heat asso-
ciated with cooking. The Agency believes that exposure to
heated water contaminated with less than 10 ppb aldicarb will
have levels no higher than 5 ppb; however, this was not factored
into the Agency's .estimates of exposure.
4. RISK ASSESSMENT
The Agency has estimated acute dietary risk from exposure
to legal residues of aldicarb in treated commodities and aldicarb
residues in ground water. This section describes the Agency's
assessment of risk.
This risk assessment differs considerably from previous
assessments because it uses TAS and actual residue estimates
rather than the Theoretical Maximum Residue Concentration (TMRC)
to estimate exposure and risk. Previously, the Agency utilized
the TMRC to determine the maximum possible exposure to legal
residues. That analysis was used primarily to determine whether
additional tolerances should be established by the Agency. That
analysis also assumed average consumption of treated commodities.
The analysis in this document uses TAS and upper 5 percent
residue values at the 95 percent confidence limit to determine
the distribution of exposure, and hence risk, for various
subpopulations.
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11-12
There are two important assumptions inherent in the risk
assessment. First, this assessment assumes that all food
consumed on a single day is consumed at a single sitting. This
is an important consideration because ChE inhibition by aldicarb,
and other carbamates, is immediate, but rapidly reversible.
Secondly, when risk estimates are presented for people exposed by
eating several types of processed foods on a single day, the
Agency assumes that all appropriate commodities contain residues.
a. Introduction
The Agency assumed that consumption of all treated food
commodities, each containing the 95 percentile level of residue,
either with or without contaminated water, on a single occasion,
is highly improbable. Three major sources of dietary exposure
were identified:
Citrus (oranges or grapefruit),
Potatoes, and
Water (contaminated with 10 ppb aldicarb).
These three sources of dietary aldicarb exposure are the
focus of the Agency's risk analysis.
b. Toxicology Endpoints
As previously mentioned, ADls have traditionally been used
to account for chronic consumption, while the current analysis
focusses on acute exposure to aldicarb. The endpoint judged most
appropriate for establishing a Reference Dose (RfD) for this type
of exposure was the extrapolated NOEL for human ChE inhibition,
0.01 mg/kg. A ten-fold uncertainty factor was applied to this
dose to account for inter-subject variability, yielding an RfD of
0.001 mg/kg, or 1 ug/kg/day. This dose has been highlighted in
all of the risk assessment tables.
The Agency, in describing the risks associated with consump-
tion of aldicarb in the diet, has calculated margins-of-safety
(MOS) for the various doses distributed among the populations.
These MOSs are described with respect to both the NOEL for
clinical signs, 0.05 mg/kg from Dernehl and Block, and the
extrapolated NOEL for ChE inhibition, 0.01 mg/kg. Consumption of
doses higher than the RfD represents an MOS less than 10 for ChE
inhibition and less than 50 for clinical signs.
c. Risk from Food Residues
The Agency performed a detailed estimate of the percent of
an affected population which may be exposed to various amounts of
aldicarb via residues in or on citrus and potatoes. A distri-
bution of exposure (risk) was calculated for various affected
populations. These estimates assume exposure to 95th percentile
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11-13
residue values in citrus (oranges and grapefruit) and potatoes.
The distribution reflects differences in amount consumed per unit
body weight.
The most important conclusion from the risk analysis of
treated commodities is that individuals with exposure to the 95th
percent confidence level residue values have MOS levels that are
low in most cases.. The percent of affected populations and MOS
for average residues are presented in Table II-l. The 95 percent
confidence level residue values for oranges, grapefruit, and
potatoes are presented in Table II-2.
1) Oranges
Thirty-four percent of children and 18 percent of infants
are expected to consume oranges on any given day. Of this group,
it is predicted that 10 percent of these children and 3 percent
of infants consuming oranges with 95th percentile aldicarb
residues would have dietary exposures of 1 ug/kg or greater,
which would correspond to an MOS of less than or equal to 10 for
ChE inhibition and an MOS less than or equal to 50 for clinical
signs. (See Table II-2)
2) Grapefruit
Only a small percentage of any subgroup is predicted to be a
consumer of grapefruit on any given day (from 0.5 percent in
infants to 6.4 percent of females of 13+ years). However, large
percentages of the infants (34 percent) and children (42 percent)
consuming grapefruit with 95th percentile aldicarb residues would
be predicted to have exposures of 1 ug/kg or greater, which cor-
responds to an MOS of less than or equal to 10 for ChE inhibition
and less than or equal to 50 for clinical signs. (See Table 11-2)
3) Potatoes
It is predicted that from 20 to 55 percent of the consumers
of potatoes containing 95th percentile aldicarb residues in each
of the subgroups studied would have dietary exposures of 1 ug/kg
or greater, which corresponds to an MOS of less than or equal to
10 for ChE inhibition and less than or equal to 50 for clinical
signs. (See Table II-2)
d. Risks from Contaminated Drinking Water
Table II-3 was compiled from the results of a TAS analysis
to determine exposure to aldicarb from all dietary sources of
water. The TAS analysis is based on the total dietary intake.
The focus of this analysis was on the population at greatest
risk: infants. Infants consume most of their diet as formula and
fruit juice; both of .these are frequently prepared using tap
-------
11-14
TABLE II-l
PERCENT OF AND MOS FOR AFFECTED
POPULATIONS CONSUMING AVERAGE RESIDUES
Population^/
CITRUS
General Pop.
Infants
Children
Females
Males
POTATOES
General Pop.
Infants
Children
Females
Males
Percent
Users^/
45.
19.
42.
47.
44.
56.
38.
60.
52.
59.
0
9
6
0
0
2
3
0
4
5
ug/kg = 0.5
MOS^/ = 100
MOS-47 = 20
Exposure
0.8 1.0 1.5 2.
0
63 50 33 25
13 10 7
5
2.5 5
20
4
.0
10
2
Percent Population/Subpopulation
Exceding Exposure
2
29
18
0
0
6
15
22
3
3
1
11
6
0
0
2
8
7
0
1
RfD
0
6
3
0
0
1
6
6
0
0
0
1
1
0
0
0
3
2
0
0
0
1
0
0
0
0
2
1
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
I/ Infants «1 year), children (1-6 years), females (13+ years), and
males (13+ years).
2/ Percent population anticipated to be exposed to a commodity containing
aldicarb residues.
I/ Compared to the NOEL for clinical signs in the registrant's human
study.
A/ Compared to the extrapolated NOEL for ChE inhibition in the registrant's
human study.
-------
11-15
TABLE I1-2
PERCENT OF AND MOS FOR AFFECTED POPULATIONS
CONSUMING 95 PERCENT CONFIDENCE LEVEL RESIDUES
Population^/
ORANGES
General Pop.
Infants
Children
Females
Males
GRAPEFRUIT
General Pop.
Infants
Children
Females
Males
POTATOES
General Pop.
Infants
Chi Idren
Females
Males
ug/kg =
MO&3-/ =
HOB*/-
0.2
250
50
Percent
Users-2-/
29.
18.
34.
28.
28.
4.7
0.5
1.2
6.4
4.6
56.
38.
60.
52.
59.
6
4
5
7
2
2
3
0
4
5
16
13
20
15
15
65
100
91
66
61
79
89
84
77
80
0.5
100
20
Exposure
0.8 1.0 1.5 2.0
63 50 33 25
13 10 7 5
2.5 5
20
4
.0
10
2
Percent Population/Subpopulation
Exceeding Exposure
8
4
14
6
4
22
61
65
22
14
59
56
71
55
56
3
3
12
1
1
5
44
48
4
2
37
33
61
29
34
RfD
210
321
10 6 3
000
100
3
34
42
2
1
28
28
55
20
24
1 0
26 17
23 8
0 0
0 0
14 8
22 17
41 28
8 3
10 4
0
1
2
0
0
0
9
6
0
0
6
14
21
2
3
0
0
0
0
0
0
0
0
0
0
1
5
4
0
0
I/ Infants (
-------
11-16
TABLE II-3
PERCENT OF AND MOS FOR AFFECTED
POPULATIONS CONSUMING WATER FROM ALL DIETARY SOURCES^/
Exposure
ug/kg = 0.5 1.0 1.5 2.0 2.5 5.0 10.0
MOS^/ = 100 50 38 25 20 10 5
MOS5-/ 20 10 85421
Population^/ Percent
Users^/
Percent Population/Subpopulation
Exceeding Exposure
60th Percentile
General Pop.
Infants
Children
Females
Males
70th Percentile
General Pop.
Infants
Children
Females
Males
80th Percentile
General Pop.
Infants
Children
Females
Males
90th Percentile
General Pop.
Infants
Chi Idren
Females
Males
Residues (10 ppb)&/
99.9
94.9
100.0
99.9
100.0
Residues (20 ppb)^./
99.9
94.9
100.0
99.9
100.0
Residues (30 ppb)2/
99.9
94.9
100.0
99.9
100.0
Residues (70 ppb)2/
99.9
94.9
100.0
99.9
100.0
3
63
15
0
0
15
90
69
4
5
35
95
90
23
23
73
96
98
66
67
RfD
0
13
1
0
0
3
63
15
0
0
7
84
46
1
1
29
94
88
16
17
0
2
0
0
0
1
28
3
0
0
3
63
15
0
0
13
87
68
3
4
0
1
0
0
0
0
13
1
0
0
1
39
5
0
0
7
77
46
1
1
0
0
0
0
0
0
5
0
0
0
0
22
2
0
0
4
64
28
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
12
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-------
11-17
TABLE II-3 (continued)
PERCENT OF AND MOS FOR AFFECTED
POPULATIONS CONSUMING WATER FROM ALL DIETARY SOURCES^/
Exposure
ug/kg = 0.5 1.0 1.5 2.0 2.5 5.0 10.0
MOS4-/ = 100 50 38 25 20 10 5
MOS5-/ 20 10 85421
Population2-/ Percent
Users-3-/
Percent Population/Subpopulation
Exceeding Exposure
95th Percentile
General Pop.
Infants
Children
Females
Males
Residues (100 ppb)2/
99.9
94.9
100.0
99.9
100.0
88
97
99
85
85
RfD
52
95
95
41
42
27
93
86
14
15
15
89
72
4
5
10
82
56
1
2
2
36
9
0
0
0
4
0
0
0
99th Percentile Residues (230 ppb)2/
General Pop. 99.9
Infants 94.5
Children 100.0
Females 99.9
Males 100.0
99
99
100
97
97
92
98
99
90
90
78
96
98
73
73
62
96
97
53
54
47
95
94
35
36
13
87
67
3
4
2
50
16
0
0
I/ Includes water in coffee, tea, soft drinks, infant formula, etc.
2/ Infants (<1 year), children (1-6 years), females (13+ years), and males
(13+ years).
I/ Percent population anticipated to be exposed to a commodity containing
aldicarb residues.
I/ Compared to the NOEL for clinical signs in the registrant's human study.
5_/ Compared to the extrapolated NOEL for ChE inhibition in the registrant's
human study.
Ł/ 10 ppb is the current Health Advisory Level (HAL).
2/ Obtained from the 1981 Sulfolk County Drinking Water Survey.
-------
11-18
water. Infants are also awake about 12 hours a day; thus, the
total daily intake was divided in two, with each half being the
amount expected to be consumed within a six hour period, the
duration of ChE inhibition from a single dose of aldicarb.
e. Conclusions
Infants and children are at highest risk of acute aldicarb
toxicity. As many as 55 percent of these subpopulations con-
suming the 95th percentile residues are exposed to an amount
greater than the RfD, based on analysis of citrus and potatoes.
The Agency calculated that when drinking water containing
aldicarb at 10 ppb, as many as 13 percent of consuming infants
could be exposed to a dose of 0.001 mg/kg or greater of aldicarb.
The corresponding Margin of Safety for cholinesterase inhibition
would then be 10 or less, based on the NOEL estimated by the
National Academy of Sciences.
B. GROUND WATER VUIJ
This analysis is divided into two sections. The first
section summarizes current information on the environmental fate
of aldicarb. The second section summarizes two assessments used
by the Agency in predicting the likelihood of ground water
contamination resulting from the use of aldicarb.
Due to the length and extensive technical scope of this
Technical Support Document, the Ground Water Vulnerability
Analyses have been summarized and only a portion of the
scientific details and documentation have been included in this
Support Document. The Ground Water Vulnerability Analyses and
references can be viewed in the Public Docket, located in room
236, Crystal Mall #2, 1921 Jefferson Davis Highway, Arlington,
Virgina. Two additional references were used extensively in
these analyses and are also part of the Public Docket:
"Ground Water Regions of the United States," United
States Geological Survey, Water Supply Paper 2242,
Ralph C. Heath, 1984.
"Ground Water Vulnerability Assessment in Support of
the First Stage of the National Pesticide Survey,"
Alexander, Liddle, Mason, Yeager. Research Triangle
Institute, February 14, 1986.
The first of these references provides explanatory material
relating to the geographic areas of study in the first method of
assessing ground water vulnerability, i.e. Heath Regions. The
second reference provides documentation for one of the vulner-
ability assessment approaches used for each assessment method,
i.e. DRASTIC.
-------
11-19
1. ENVIRONMENTAL FATE
a. Leaching Potential
Aldicarb is mobile in most types of soil in which it is
applied, with adsorption coefficient values (K^) typically less
than 1.0, often near 0.1 and occasionally lower (Cohen et al,
1984). Kg- values less than the 1-5 range indicate that the
pesticide has considerable mobility. Incidents of ground water
contaminated by aldicarb have been primarily associated with
sandy soils. This is because aldicarb binds poorly to sandy
soils (sands, loamy sands, and sandy loams, primarily) and any
water input to sandy soil (i.e., rain and irrigation) tends to
recharge rapidly through the profile, carrying aldicarb with it
(Cohen et al, 1984).
b. Metabolism and Degradation
Soil half-lives for degradation of aldicarb and its metab-
olites to nontoxic residues in the root zone vary from a week to
greater than two months, but are typically between one and two
months. The primary mode of degradation in the root zone is
oxidative metabolism by microorganisms, although hydrolysis may
also occur. Factors which affect the robustness of the microbial
community also affect the microbial decay of aldicarb in the root
zone. Warm soil temperatures, high soil moisture content, and
high organic matter content all result in more rapid rates of
aldicarb degradation. In a nondegradative pathway, aldicarb
oxidizes to aldicarb sulfoxide in a matter of days, and a portion
of the aldicarb sulfoxide oxidizes to aldicarb sulfone. Aldicarb
sulfoxide and sulfone residues are found approximately in a one-
to-one ratio (Cohen et al, 1984).
The primary mode of degradation below the root zone is
chemical hydrolysis. Typically, the rate of hydrolysis
degradation is slower than microbial degradation. Measured and
extrapolated half-lives vary from several weeks to greater than
20 years under ambient conditions, depending on pH and temp-
erature. An unexpected finding in two studies is that hydrolysis
is significantly slower in Long Island (Lemley and Zhong, 1984)
and Florida (Miles and Delvino, 1985) ground water microcosms
than in conditions found in standard laboratory hydrolysis
studies. Aldicarb sulfoxide (the first degradation product of
aldicarb) is partially reduced to the parent aldicarb in
Floridian aquifer microcosms, possibly explaining the enhanced
half-life under these conditions (Ou et al, 1985a and b).
Other modes of pesticide dissipation include volatilization
and photolysis. Aldicarb's high water solubility and low vapor
pressure preclude volatilization as a loss mechanism. The method
of application, soil incorporation, and stability to sunlight in
-------
11-20
water (93 percent of applied dose remaining after 14 days in one
study (Union Carbide, 1983)) precludes photodegradation.
2. GROUND WATER ASSESSMENT
The Agency does not believe that methods presently exist to
perform accurate quantitative assessments of the amount of a
pesticide which may appear in ground water. Thus, the Agency's
review provides a qualitative, rather than quantitative, assess-
ment of the vulnerability of ground water to aldicarb contamin-
ation.
The objective of performing ground water assessments is to
determine the potential for aldicarb to leach and contaminate
ground water in the U.S. The Agency used two methods to
accomplish this: one involving Heath Regions and one involving
counties. A discussion of the two methods follows:
a. Ground Water Assessment by Heath Region
This assessment evaluates the potential for aldicarb to
reach ground water as a result of its use on the major aldicarb
crops - citrus, potatoes, cotton, soybeans, and peanuts. Those
crops account for over 90 percent of its use. The methodology
developed was aimed at key vulnerable situations, and provides
the background for future evaluations of other aldicarb uses.
This analysis focusses on the first encountered potable aquifer.
In order to structure the ground water contamination
problem, ground water regions, as defined by Heath (Heath, 1985),
were used. These regions were determined by distinct factors
which affect the occurrence and availability of ground water
(mineral composition of the rock matrix, recharge and discharge
conditions, etc.). These regions are shown in Map Il-l. Eleven
of the regions were deemed appropriate for examination based on
extent of crop acreage of the five chosen crops in the regions.
This structuring resulted in 32 crop/region combinations which
were evaluated for their potential for aldicarb contamination of
ground water from aldicarb usage and shown in Map II-2.
For each crop/region combination, three major parameters
were employed to evaluate the ground water vulnerability of these
regions. An evaluation of hydrogeologic vulnerabilities of
counties within the crop/region combination were examined using
two methods. The first method was an evaluation of 138 counties
where aldicarb is used, and the second method a measure of
hydrogeologic vulnerability using a system called DRASTIC. The
second parameter was an evaluation of monitoring results for
aldicarb. The final parameter involved an evaluation of
crop/site-specific parameters. Each of these parameters is
discussed below.
-------
MAP n-i
HEATH REGIONS
-------
Region I
2
3
4
5
6
7
8
9
10
11
MAPII-2
ALDICARB CROP/REGION COMBINATIONS
PoTCtoes
Soybeans
Potatoes
Soybeans
Soybeana
Peanut a
Potatoea
8
CoTton
Soybeana
Ponrtoes
Prnuur n
Cotton
Soybeana
ilng
Western Mountain Rangea
Alluvial Basins
Columbia Lava Plateau
Colorado Plateau and Wyo
High Plains
Nonglaciated Central
Glaciated Central
Piedmont and Blue Ridge
Nortlieust and Uii|>uilor ll|i I
Atlantic (IDA) and Gulf Coastal
Southeast Coastal Plain
II
Cotton
Citrua
Potatoes
Peanuts
Soybeans
(10B) Plain
-------
11-23
1) Hydrogeologic Vulnerability
i) 138 County Evaluation
The vulnerability of the top soil and the depth of the first
encountered potable aquifer were examined in detail for 138
counties. These counties were chosen based on actual aldicarb
usage data, amount of acreage devoted to crops on which aldicarb
could be used (to factor in aldicarb's potential, rather than
current use), and positive monitoring data. These 138 counties
are a subset of the 300-400 counties in which aldicarb is
currently used.
The Agency determined the average vulnerability rating of
each of the 138 aldicarb usage counties by assessing two
principle parameters which affect the ground water contamination
potential of aldicarb: leachability of the topsoil and depth to
ground water. A scale was constructed for each of these para-
meters, numbered from 1 (least) to 5 (most vulnerable). An
average vulnerability rating score was then computed as a simple
arithmetic mean of the topsoil and depth to ground water evalu-
ations, leading to a final ranking of ground water vulnerability
for the counties as either high, medium, or low. For purposes
of this analysis, equal importance was assigned to topsoil and
depth to ground water as they relate to overall ground water
vulnerability.
Topsoil vulnerability ratings were derived in a three step
process. First, topsoils were rated high, medium, or low as a
function of soil properties including: permeability, organic
matter, and hydrologic soil group. Then the percent of land area
for each topsoil rating was estimated. Finally, a weighted
average of these different land areas was calculated as the final
topsoil vulnerability rating. The depth to ground water vulner-
ability rating was similarly calculated by first determining the
percent of land area below which potable ground water was: 0-25
feet (high vulnerability), 25-50 feet (medium vulnerability), and
greater than 50 feet (low vulnerability). Similar to the topsoil
rating scheme, shallow depth to ground water (highly vulnerable)
was assigned a rating of 5.0; medium depth to ground water was
assigned a rating of 3.0; and great depth (low vulnerability) a
rating of 1.0. A weighted average of the land area in each
category determined the final county depth to ground water
vulnerability rating.
Topsoil vulnerability ratings vary from a low of 1.5 to a
high of 5.0 and do not fall within well defined groups. States
containing highly vulnerable (topsoil) counties (of the 138
chosen for the assessment) include: Florida, Michigan, Georgia,
Washington, South Carolina, Virginia, Massachusetts and
Wisconsin.
-------
11-24
Depth to ground water ratings for the Gulf, Atlantic and
Southeastern coastal plains range from 4.1 through 4.9. Michigan
and Wisconsin depth to ground water ratings are 4.2 and 3.5,
respectively. Depth to ground water ratings for Western states
range from 1.0 to 2.8, indicating deep aquifers.
Overall vulnerability ratings (the mean of topsoil and depth
to ground water vulnerability rating) were examined for each
crop/region combination (e.g., cotton in Region 1).
Groupings of counties specific to each crop in each region
were averaged to represent the crop/region combination ranking.
For purposes of this analysis, overall ground water vulnerability
ratings between 1.00-2.30 were classified low, 2.30-3.65 medium,
and 3.65-5.00 high.
In general, the counties in which large amounts of citrus
are grown had the highest average vulnerability scores, followed
by peanut, potato and cotton counties. However, the "medium"
score of counties in which large amounts of potatoes are grown
can be misleading. A separate analysis of Wisconsin counties
evaluated for potatoes showed that the potato-growing regions
were in areas of sandy, highly vulnerable soils. As explained
later in the crop/site-specific analysis, potatoes are typically
grown in sandy, well drained soils. Therefore, the high vari-
ability and average ratings for counties in Wisconsin mask the
fact that potatoes are grown in vulnerable portions of a county
that overall may be classified as having medium vulnerability.
This phenomenon is likely to be true for counties in other potato
growing states as well.
ii) DRASTIC Analysis
The second measure of hydrogeologic vulnerability used a
rating system devised by the National Well Water Association
(Aller et al, 1985) known as DRASTIC. DRASTIC is a screening
system which estimates ground water vulnerability. DRASTIC uses
seven characteristics: Depth to ground water; Recharge; Aquifer
media; Soil media? Topography; Impact of the vadose zone and
hydraulic Conductivity of the aquifer. Weights of the relative
importance of each characteristic are assigned as well as weights
within a characteristic.
Each county in the U.S. was first evaluated using the
DRASTIC methodology. Using the results of this project, all
counties with significant acreage of the five selected crops
within each crop/region combination could be examined for
hydrogeologic vulnerability. DRASTIC scores were then given
qualitative ratings of Low (scores of less than 102) , Medium
(scores of 102 - 142) or High (scores greater than 142).
-------
11-25
See Map II-3. The resulting scores are indicators of the overall
vulnerability of a county.
Comparison and use of both hydr©geologic methodologies on
the 138 counties the Agency evaluated allowed for assessment of
the consistency of the two approaches. In general, all crop/
region combinations were rated medium to high. There was general
agreement between the assessment using DRASTIC and the analysis
rating each county on topsoil and depth to groundwater. Of the
138 counties of the county-level vulnerability assessment, only
three of the 138 counties showed a clear discrepancy between the
assessment using DRASTIC and the vulnerability analysis rating
each county for topsoil and depth to ground water. The East
Coast crop/region combinations were rated highly vulnerable.
In general, the three Heath regions with the highest scores
(in descending order of percentage of counties and average
scores) are the Southeast Coastal Plain (Heath Region 11), the
Atlantic and Gulf Coastal Plain (Heath Region 10), and the
Glaciated Central Region (Heath Region 7). The Southeast Coastal
Plain consists principally of Florida and southern Georgia. The
potential contamination problem in the Atlantic Ocean side of the
Atlantic and Gulf Coastal Plain seems greater than the Gulf of
Mexico side. The Glaciated Central Region includes the
Connecticut River Valley, the Central Sands area of Wisconsin and
other areas of the northern plains.
2) Monitoring Data Evaluation
The second parameter was an evaluation of monitoring
results for aldicarb. Although more ground water monitoring for
aldicarb has occurred nationwide than for any other pesticide,
monitoring data are still lacking for many areas. Overall
monitoring results were summarized, and specific case studies
were examined in detail for trend analysis. Monitoring data,
where available, were given greater emphasis than the other means
of analysis.
The Agency has evaluated sampling programs encompassing over
35,000 samples. The programs chosen for evaluation by the Agency
were those specifically focussing on "impacted" ground water;
that is, the first encountered potable aquifer in the vicinity of
aldicarb treated fields. Included in the analysis were state
monitoring programs which sampled wells in the vicinity of aldi-
carb treated fields, observations from non-drinking water wells
placed in or near treated fields for research or related
purposes, and water quality testing results from national
agencies such as EPA or the U.S. Geologic Survey. Approximately
32 percent of all samples were positive. Over 25,000 of the
35,000-plus samples were taken in Suffolk county, New York, with
-------
MAPII-3
DRASTIC EVALUATIONS
DRflSTIC SCORES
SB - 101
H3 flND ftBOUE
-------
11-27
17 percent containing aldicarb residue levels greater than 10
ppb. Residues of aldicarb have been found in 48 counties within
16 states. A summary of aldicarb monitoring by state is shown in
Table II-4.
The highest residues have been associated with areas pro-
ducing potatoes, tulip bulbs and citrus. Peanut and pecan
producing areas have not been adequately monitored although they
are in hydrogeologically vulnerable areas. Following are observ-
ations from monitoring data and summaries of significant state
programs.
* "Moratorium" areas in Wisconsin (where aldicarb use is
banned for a one mile radius around wells contaminated with
aldicarb at greater than 10 ppb) coincide with areas where
aldicarb is used on potatoes and where top-soil vulnerability is
rated as high (Noren et al, 1985). In a comprehensive monitoring
program by the registrant and the Wisconsin Department of Natural
Resources (Union Carbide, 1986), approximately 53 percent of
2,474 samples taken were positive, with 20 percent of these
positives higher than 10 ppb.
* The Florida (Lake Hamilton) site showed shallow ground
water (5-30 feet below ground surface) aldicarb concentrations
at 63 ppb, more than 400 feet from the boundary of the field
plot, three years after application of 11.2 kg a.i./ha (Union
Carbide, 1985b). There was a stream located over 400 feet from
the field edge, which intercepted residues from traveling
further. At another citrus field site located in Highlands
County, aldicarb had been applied at the label rate of 5.6 kg
a.i./ha in 1984, 1986, and 1987 (no application in 1985).
Monitoring wells were established from 200 to approximately 1,000
feet from the field edge. On four sampling dates in 1987, 80
samples were taken from 25 wells equally spaced between 500 and
1,000 feet from the field edge (not all wells were sampled on all
four dates). These wells tapped the shallow surficial aquifer at
depths between five and 20 feet. Of these 80 samples, 52 were
positive, with 39 samples above 10 ppb, and a mean positive of 57
ppb. High readings of 416 and 276 ppb were noted at 800 and 900
feet, respectively (Jones, 1987).
Both of these field sites were joint projects of the regi-
strant and the Florida Department of Environmental Regulation.
These participants have similar efforts at several other aldicarb
use sites in Florida, including fernery and potato use sites.
Thus far, the citrus and fernery sites have shown high residue
levels in the ground water as well as residue movement off-site.
However, possibly because of the agronomic practices associated
with potato cultivation in Florida, no residues have been found
in ground water at that site.
-------
Table II-4
ALDICARB MONITORING RESULTS
SUMMARIES BY STATE
State
t of Counties
Reporting Posi- Total Total
tive Results Samples Positives
Positive Results in ppb
0-10 11-30 >30
Arizona
Arkansas
California
Florida
Maine
Massachusetts
Minnesota
New Jersey
New York
North Carolina
Oregon
Rhode Island
Texas
Virginia
Washington
Wisconsin
1
1
1
5
2
3
2
2
6
3
1
2
1
3
1
14
2
8
522
4,743
690
385
315
68
25,399
95
1
720
3
97
1
2.543
1
2
381
994
384
70
5
5
8,076
10
1
109
3
24
1
1.312
1
0
232
367
322
39
3
4
3,705
8
1
75
3
19
1
802
0
1
81
175
43
20
1
0
4,319
2
0
25
0
5
0
378
0
1
68
451
19
11
1
1
52
0
0
9
0
0
0
132
Totals
48
35,592 11,378
5,582 5,051 745
-------
11-29
The Florida Department of Agriculture and Consumer Services
(DACS) has been monitoring drinking water wells in the vicinity
of aldicarb treated fields (Inman, 1986). These wells were
located through the DACS program which requires users of aldicarb
to register their use of the pesticide. Thus far, of approx-
imately 950 samples (encompassing roughly the same number of
drinking water wells - some wells were retested), six wells in
four counties contained residues, with the highest reading of 27
ppb.
The apparent discrepancy between the DACS studies and the
DER studies is attributed to the differences in ground waters
which were tested. The DER studies focussed on samples from
water table aquifers drawn from research wells. The DACS studies
involved samples from existing wells, which, in all likelihood,
were drilled to deeper, more protected depths, and which were
also probably further away, and in some cases, upgradient from
the aldicarb use site.
Since aldicarb was banned in Suffolk County, NY in 1979, the
Suffolk County Department of Health has been monitoring all
drinking water wells in which contamination occurred (Andreoli,
1986). The county has located approximately 7,500 wells which
are near potato fields formerly treated with aldicarb. A summary
of sampling results for the six-year period, 1980-1985, is found
in Table II-5. As can be seen, residues have shown little
fluctuation. Residues above the New York health guidance level
of 7 ppb ranged from 13 to 28 percent of the total positives with
23 percent of the positives above 7 ppb in 1985.
In a research study by Porter et al (1986), 150 wells were
sampled in Suffolk County, N.Y., during 1983 and 1984 which had
originally been sampled in 1980. He characterized subsets of
these wells as shallow, medium, and deep and concluded the
following:
- aldicarb contamination in shallow wells is declining;
- aldicarb contamination in moderately deep screened
wells is relatively unchanged; and
- aldicarb contamination at greater depths is increasing.
* The Massachusetts Department of Food and Agriculture
sampled 316 wells associated with potato use as of March 1985
(Sylva, et al, 1985). Approximately 18 percent of the total
samples were positive, with eight percent of all samples greater
than 10 ppb.
* In Maine, wells near potato fields have been sampled since
1980 in a program jointly administered by the University of Maine
-------
11-30
Table II-5
SUFFOLK COUNTY DEPARTMENT OF HEALTH
MONITORING OF IMPACTED WELLS, 1980-1985
Year * Samples >8 ppb 1-7 ppb Mean* Median*
1980
1981
1982
1983
1984
1985
8,595
677
2,905
4,659
3,974
4.022
1,193
190
380
804
670
942
1,167
275
265
661
546
688
24.7
11.7
20.0
19.9
17.2
18.7
8
5
10
8
8
8
Total 24,832 4,187 3,602 20.2 8
* Mean and median of positive wells only
-------
11-31
and the registrant (Union Carbide, 1985). Between 1980 and 1985,
approximately 56 percent of the 690 samples taken have been
positive, with nine percent of all samples above 10 ppb.
* The North Carolina Department of Agriculture collected 138
samples from 104 wells associated with tobacco and cotton fields
in late 1982 (Graham, 1984). Twelve positive samples were found
and two of the 12 well samples associated with cotton fields
contained aldicarb residues of 27 and 28 ppb. Subsequent samples
from the positive wells were found to be negative for aldicarb
residues when retested in early 1983.
* The Rhode Island Department of Health has an extensive
aldicarb monitoring program associated with testing private wells
near potato fields (Rhode Island Department of Health, 1985 and
Union Carbide, 1985a). Thus far, of a total of 720 samples (697
wells), 15 percent of all of the the samples have been positive,
with four percent of all of the samples greater than 10 ppb. The
maximum observation was 73 ppb aldicarb.
* In Del Norte County, California, wells near lily bulb
fields were monitored, starting in 1983 (Union Carbide, 1985a).
As of 1985, 522 samples from 60 wells showed 73 percent positive,
with 28 percent of all of the samples greater than 10 ppb. As a
result of sampling in 1983, the California Department of Food and
Agriculture suspended the use of aldicarb in Del Norte County in
June, 1983. A follow-up study performed by the registrant found
63 positives in 74 total samples.
* The Idaho Department of Health and Welfare conducted a
sampling program in 1981 and monitored three areas adjacent to
potato and sugar beet fields (Brokopp, 1987). There were no
positives out of 251 samples.
* The Agency conducted a comprehensive field study in the
Dougherty Plains of Georgia (Carsel, 1987). This area is
associated with the production of peanuts. The results indicated
that aldicarb has not moved beyond two to three feet below the
soil surface and the field half-life was calculated to be two to
three weeks.
The results of these various monitoring studies have
indicated that most monitoring has been associated with potato
and citrus production areas whereas there has been a lack of
monitoring associated with peanuts, cotton, and soybeans.
Relatively high percentages (5 to greater than 50 percent) of
positive findings occurred in Wisconsin and Northeastern states
(NY, MA, RI, CT, ME) associated with potato use. Also, there was
substantial evidence of leaching to shallow ground water asso-
ciated with citrus use in Florida. Monitoring in several citrus
use sites, within 1000 feet of the field and beyond, showed
several positive findings above 100 ppb and one finding above
-------
11-32
1,000 ppb beneath a field site (Miller et al, 1984). There were
some monitoring efforts associated with peanuts and cotton on the
East Coast, and potatoes in Idaho, all showing few positives.
3) Crop/Site-Specific Correlation Approach
The 138 county and DRASTIC analyses measure and evaluate
hydrogeologic vulnerability. However, they do not consider
factors such as: agronomic practices (irrigation, crop preference
for certain soil types), rate of aldicarb application, and
temperature (which influences degradation). For that reason, an
analysis which considers these factors for each crop/region
combination was undertaken.
Specifically, for each crop/region combination, the
following factors were used: 1) "recharge" (rainfall and irri-
gation practices were used as a surrogate for recharge), 2) air
temperature, 3) rate of application, 4) root-crop consideration,
and 5) regional soil order predominance.
Cotton and soybeans were evaluated as low in terms of rate
of application (0.6-1.7 kg/a.i./ha), potatoes and peanuts medium
(2.2-4.4 kg/a.i./ha), and citrus high (5.6-11.2 kg/a.i./ha).
Root crops prosper in and prefer sandy, well- drained soil pro-
files. Since peanuts and potatoes are root crops, they were
rated high. Conversely, cotton, soybeans, and citrus were rated
low in terms of the root crop consideration. Finally, assess-
ments of high, medium, and low were made for nine soil "orders"
(as defined by the Soil Conservation Service taxonomic system) in
which the crops are typically grown in each region.
The final crop/site-specific ratings were determined by a
weight-of-evidence evaluation of the five factors described
above.
Observations from the crop/site-specific analysis include:
a) Potatoes in Heath Region 11 (Florida) were rated as
medium because agricultural practices in Florida are designed to
avoid saturated soil conditions. There is immediate runoff and
shallow drainage through the use of tiles draining into canals.
These practices minimize leaching. Monitoring has shown no
contamination of ground water. Personal communication with State
Department of Environmental Regulation personnel indicate that
aldicarb has been found in drainage canals associated with potato
(and fern) cultivation.
b) Peanuts were rated medium to high, because it is a root
crop and typically grown in sandy soils in the Southeast and
because in this region, warm temperatures exist at aldicarb
application time, and warm temperatures hasten aldicarb metab-
-------
11-33
olism. Further justification for a medium to high rating is a
medium rate of application.
c) Cotton is irrigated primarily in California, Arizona,
and New Mexico and is rated low to medium. A significant
percentage of Georgia cotton is also irrigated, where it is also
rated as medium. Cotton is not irrigated to any great extent in
other States. California is the only State where it is possible
to generalize about soil types for cotton. California and
Arizona soils, known as "Aridosols", are typically found in arid
climates and require irrigation to be productive. Otherwise,
cotton is grown in a variety of soils.
d) Citrus is rated as high and is grown in sandy soils in
Florida, with approximately two-thirds of the crop irrigated at a
maximum rate of about 20 inches/year.
e) Soybeans were rated low to medium in all growing
regions. The application rates for soybeans are low. Factors
which warranted a medium rating included temperature and high
rate of rainfall in many of the soybean regions.
4) Results of Integrated Ground Water Assessment
by Heath Region
Each of the four methodology factors was given a qual-
itative rating of "high", "medium", "low", or "insufficient
data" (H, M, Lf ID) for each crop/region combination. A
"weight-of-evidence" approach was then used to evaluate each
crop/region combination as high, medium, or low potential to
contaminate ground water and can be defined as follows:
Low - Crop/region combinations which have a low potential
for aldicarb to leach to ground water.
Medium - Crop/region combinations where there exists a
moderate potential for aldicarb to reach ground
water due to many possible factors such as moderate
hydrogeologic vulnerability, agronomic practices, or
geographic variability. Increased monitoring in
these crop/regions could elevate some of them to the
High category or conversely, could alleviate concern
and place them in the Low category.
-•
High - Crop/region combinations where the weight-of-
evidence indicates that aldicarb has a high
probability to leach to ground water. Additionally.-
a crop/region combination will be placed in the
High category if there are positive aldicarb
monitoring data associated with it.
-------
11-34
A tabular summary of the results is provided in Table II-6.
Separate columns for each of the previously discussed methods of
analysis with individual ground water vulnerability ratings are
also shown. Map II-4 illustrates the results of Table II-6,
showing the high, medium, and low vulnerability areas by crop and
depicts the Heath region.
The Agency believes that this weight-of-evidence approach
and corresponding qualitative ground water vulnerability ratings
provide a rational basis for depicting potential ground water
contamination from aldicarb usage.
The overall ground water vulnerability ratings, based on the
four independent approaches, show a high vulnerability for pota-
toes in Heath Regions 7 and 9 and citrus and peanuts in Heath
Region 11. In the first three of these crop/regions, monitoring
data has confirmed the vulnerability rating. In the case of
peanuts in Heath Region 11, the county, DRASTIC, and site-
specific analyses indicated a high vulnerability and if monitor-
ing data were available, positive findings would be expected.
Cotton in Heath Regions 1 and 2 shows a low vulnerability
due primarily to the low application rates and the deep ground
water associated with these regions.
The remaining crop/region combinations were given medium
vulnerability ratings based on the four approaches. It should be
understood that a portion of these medium crop/regions could be
placed in the high or the low vulnerability category if addi-
tional monitoring data were available.
b. Ground Water Assessment by County
Another method developed by the Agency to evaluate the like-
lihood of ground water contamination was to perform an assessment
at the county level. The advantage to this method is that it
focusses on a smaller geographic unit, the county, than the Heath
Region which was used in the first method. This assessment uses
three parameters.
1) DRASTIC Analysis
The first parameter in this assessment was the DRASTIC
rating system, which was also part of the Heath Region assessment
found on page 11-23. The resulting scores, as in the Heath
Region assessment, are then given qualitative ratings of Low
(scores of less than 102), Medium (scores of 102 - 142) or High
(scores greater than 142).
-------
11-35
TABLE II-6
GROUND WATER VULNERABILITY
Heath
Reaion Crop
1
2
3
5
6
7
8
9
10A
10B
11
Citrus
Cotton
Potatoes
Cotton
Citrus
Potatoes
Cotton
Peanuts
Soybeans
Potatoes
Cotton
Peanuts
Soybeans
Potatoes
Soybeans
Cotton
Soybeans
Potatoes
Soybeans
Potatoes
Peanuts
Cotton
Soybeans
Citrus
Potatoes
Cotton
Soybeans
Peanuts
Cotton
Citrus
Potatoes
Peanuts
Soybeans
County-
Level
L
L
L
L
L
L
M
M
ID
M
H
L
H
M
ID
H
H
H
ID
H
H
H
H
M
ID
M
M
H
H
H
H
H
H
DRASTIC
M
M
M
L-H
L-H
M
M
M
M
M-H
M
M
M-L
M-H
L-M-H
H
M-H
M-H
M-H
H
H
H
H
M
H
M-H
M-H
M-H
H
H
H
H
H
Crop/Site
Specific
M-H
M
M-H
L-M
M
M
L-M
M
L
M
L-M
M
L-M
M-H
L-M
L-M
L-M
M-H
L
M
M-H
M
M
M
M
L-M
L-M
M
M
H
M-H
M-H
L-M
Final
Monitorina VR
ID
ID
ID
ID
ID
L
ID
ID
ID
ID
ID
ID
ID
H
ID
ID
ID
H
ID
M
ID-L
ID-L
ID
ID-L
ID
ID-L
ID
ID-L
ID
H
ID-L
ID
ID
M
L
M
L
M
M
M
M
M
M
M
M
M
H
M
M
M
H
M
M
M
M
M
M
M
M
M
M
M
H
M
H
M
H: high concern, M: medium concern, L: low concern, ID: insufficient data
-------
Region 1
2
3
4
5
6
7
8
9
10
11
MAPII-4
FINAL RESULTS OF ALDICARB
INTEGRATED ASSESSMENT
O.BEB
Western Mountain Ranges
Alluvial Basins
Columbia Lava Plateau
Colorado Plateau and Wyoaiing BaVln
High Plalna
Nonglaclated Central
Glaciated Central
PledMont and Blue Ridge
Northeast and Superior Uplands
Atlantic (10A) and Gulf Coastal (10B) Plain
Southeast.Coastal Plain
H
M
llllllll
L
-------
11-37
2) Use and Usage
The second parameter considered the use rates and/or total
amount of aldicarb applied in a county. The Agency assumed that
the greater the rate of application or amount of pesticide used,
the greater the amount which is available to leach to ground
water.
The Agency classified each county's Use/Usage ranking by
first reviewing each county's top three crops, then selecting the
crop with the highest application rate, and finally classifying
each county based on the crop with the highest application rate.
The Agency has obtained crop ranking data from the registrant
which qualitatively describes the primary, secondary and tertiary
aldicarb use crops in each county. The current application rate
for aldicarb ranges from 1 to 10 Ibs. a.i./A. The Agency ranked
aldicarb application rates into three categories: low «1 Ib.
a.i./A), medium (2-5 Ibs. a.i./A) and high (>5 Ibs. a.i./A).
The Agency recognizes the potential disadvantages of such a
design (e.g., a county's top three crops may have low use rates,
but an unidentified 4th top crop may have a high application
rate.) The Agency believes, though, that by taking into account
the usage rate (Ibs. a.i./county/yr) the likelihood of missing a
high use county is reduced. The current poundage data base,
supplied by the registrant, compiles county level usage data from
1979 through 1983. The Agency classified aldicarb county usage
rates into the following two categories: low (<25,000 Ibs.
a.i./county/yr.) and high (>25,000 Ibs. a.i./county/yr.).
The Agency classified a county's final Use/Usage ranking by
using the higher of the application rate ranking and total county
usage data to classify a county as Low, Medium or High. For
example, counties with low application rates and high annual
usage and counties with high application rates and low annual
usage would both be rated as high. The rating system's upward
bias reflects the Agency's concern for exposures to contaminated
ground water.
The Agency recognizes that this method of evaluating
loadings may classify certain counties as High when there is, in
fact, very little exposure (e.g., 200 pounds used annualy at an
application rate of 10 Ibs. a.i./A.). The Agency may, in these
counties, modify its final assessment and would be1 reviewed on a
case-by-case basis.
In order to avoid instances where a county's usage is rated
lower than it should be because of gaps in the Agency's use data
base, the Agency will also consider usage data in assigning a
final aldicarb use rating for a county for the use/usage cri-
teria. The current poundage data base, confidential information
-------
11-38
supplied by the registrant, compiles county level usage data from
1979 through 1983.
3) Monitoring Data Assessment
The ground water assessment by Heath Region section
discusses in detail the many data which are available to the
Agency regarding the absence or presence of aldicarb in ground
water and/or drinking water. The county assessment utilizes
these same data in much the same manner as they were used in that
assessment.
Although there are more monitoring data for aldicarb than
for any other pesticide, many areas still lack adequate data.
This deficiency is even more evident in the county assessment
than in the Heath Region assessment due to the difference in the
geographic unit being evaluated.
Monitoring data for a particular county are evaluated and
assigned a rating of pattern positive, limited positive, or
none/negative. In general, a pattern positive rating will be
assigned in those instances where there are a large number of
samples and a significant percentage of positive detections.
Detections of aldicarb in any county above the Health Advisory
(HA) for aldicarb (10 ppb) will serve to flag that county for
consideration of a pattern positive rating. However, while
performing the monitoring data assessment, levels above or below
the HA will not solely influence the designation assigned to a
county.
Designation of a pattern positive for a county requires a
"weight-of-evidence" assessment of available monitoring data.
As with the Heath Region approach, these monitoring data were
examined with a specific focus on: 1) whether the data are
representative of the quality of the first encountered potable
aquifer in the vicinity of the aldicarb use sites, and 2) how
extensive the data are.
Ranging from most representative to least representative of
the different monitoring data available to the Agency, the first
criterion leads to the following general guidelines.: 1) re-
search or similar field site monitoring near fields of aldicarb
use, 2) U.S. Geologic Survey or similar area-wide water quality
monitoring (within 500 feet of the treated field), 3) private
drinking water well data (within 500 feet of treated fields), 4)
private drinking water wells not near the treated field, 5) on
site irrigation wells, and 5) community or public drinking water
wells (greater than 100 feet deep and far from the treated
fields).
The second criterion (extensiveness of sampling) refers to
the total number of samples required in order for the data to
-------
11-39
definitively show a pattern of positive results. Clearly, the
more sampling available, the better. Also, a fewer number of
samples would be needed for a definitive conclusion if the
samples originate from the most representative monitoring (field
site testing) than samples from wells less representative of the
impacted aquifer. As few as 20 samples from a carefully designed
research field site could be sufficient for a county-wide judge-
ment, if it can be shown that the field site is representative of
aldicarb use sites in that county. If the monitoring data
originates from within 500 feet of a use site, it is presumed
that at least 50 samples are required in order to justify a
pattern positive rating.
Assuming a sufficient data set exists in the county, a final
judgement on pattern positive is dependent only on a percentage
of positive hits. The monitoring data available indicated a rate
from 5 to over 50 percent positives with ±.he lower percentages
for drinking water surveys and the higher rates for research or
other aquifer characterization studies. On that basis, a general
guideline followed for pattern positive is at least a 5 percent
positive rate for sufficient drinking water data, and at least a
10 to 20 percent positive rate for research-oriented monitoring.A
limited positive rating is assigned whenever there is a positive
finding. This rating may be upgraded to pattern positive depend-
ing on the outcome of the assessment. In general, a limited
positive rating would be assigned when there is only a small
number of samples available, regardless of the concentration
detected. Finally, a limited positive rating is assigned if a
small percentage of samples are positive with the highest level
of detection near and not significantly different from the HA.
The third rating which can be assigned is none/negative.
Such rating would be assigned for a county in which no monitoring
data are available or where monitoring has occurred but the study
is considered inadequate. Additionally, the Agency has decided
to assign this rating in those instances where monitoring has
been conducted but aldicarb has not been detected. This decision
is based on the difficulty in concluding that aldicarb will not
leach in a particular county and to reduce resources necessary to
conduct this evaluation.
4) Results of Integrated Ground Water Assessment by
County
Given that the county ground water assessment involves three
criteria, each of which involves three different ratings, there
are 27 possible rating combinations. The Agency believes that it
can use these various rating combinations in order to predict the
likelihood of ground water contamination by aldicarb within a
county.
-------
11-40
Each of the above three parameters would be qualitatively
rated for a particular county. This approach was used to eval-
uate each of the 27 rating combinations as either being class-
ified as having a high, medium or low potential to contaminate
ground water, and can be defined as follows:
Low - Counties which have a low potential for aldicarb to
leach to ground water.
Medium - Counties where there exists a moderate potential
for aldicarb to reach ground water due to many
possible factors such as moderate hydrogeologic
vulnerability, agronomic practices, or geographic
variability. Additional monitoring data from these
counties could elevate some of them to the High
category or conversely, could alleviate concern and
place them in the Low category.
High - Counties where the weight-of-evidence indicates
that aldicarb has a high probability to leach to
ground water. Additionally, a county will be placed
in the High category if there is a pattern of positive
aldicarb residues associated with the county.
The assignment of one of these three classes to each of the
27 combinations is presented in Table II-7. As in the Heath
Region assessment, the Agency believes that the weight-of-
evidence approach and corresponding qualitative leaching poten-
tial ratings provide a rational basis for depicting ground water
vulnerability to aldicarb contamination.
The Agency has not performed a county ground water assess-
ment for all counties. However, the assessment has been
performed for counties in four states (California, Florida, North
Carolina, and Wisconsin). The results of these assessments are
summarized in the following Table II-8.
-------
11-41
Table II-7
COUNTY ASSIGNMENTS
vui.
High
High
High
High
High
High
High
High
High
Medium
Medium
Medium
Medium
Medium
Medium
Medium
Medium
Medium
Low
Low
Low
Low
Low
Low
Low
Low
Low
Use/Usage
High
High
High
Medium
Medium
Medium
Low
Low
Low
High
High
High
Medium
Medium
Medium
Low
Low
Low
High
High
High
Medium
Medium
Medium
Low
Low
Low
Monitoring Potential To Leac
Pattern Positive
Limited Positive
None/Negative
Pattern Positive
Limited Positive
None/Negative
Pattern Positive
Limited Positive
None/Negative
Pattern Positive
Limited Positive
None/Negative
Pattern Positive
Limited Positive
None/Negative
Pattern Positive
Limited Positive
None /Negative
Pattern Positive
Limited Positive
None/Negat i ve
Pattern Positive
Limited Positive
None/Negative
Pattern Positive
Limited Positive
None/Negative
High
High
High
High
Medium
Medium
High
Medium
Medium
High
Medium
Medium
High
Medium
Medium
High
Medium
Medium
High
Medium
Medium
High
Medium
Low
High
Medium
Low
-------
11-42
TABLE II-8
FINAL RESULTS OF COUNTY ASSESSMENT
County
Vul. Use/Usage Monitoring
Leaching Potential
H M L
CALIFORNIA
Kings
Merced
Colusia
Glenn
Sacramento
San Joaquin
Solano
Yolo
H
H
H
H
H
H
H
H
H
H
M
M
M
M
M
M
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
X
X
X
X
X
X
X
Sutter
Fresno
Kern
Los Angeles
Madera
Orange
Riverside
Santa Barbara
Tulare
Ventura
Imperial
Monterey
Nevada
San Luis Obispo
Alameda
Butte
Contra Costa
Del Norte
Humbolt
Inyo
Lake
Marrin
Mendocino
Modoc
Mono
Napa
Plumas
San Benito
San Bernardino
San Francisco
San Mateo
H
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
H
H
H
H
H
H
H
H
H
M
M
M
M
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
pattern positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
x
X
x
x
x
x
x
x
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-------
11-43
Table II-8 (cont'd).
Monitorina
Leaching Potential
H M L_
CALIFORNIA (cont'd)
Santa Clara
Siskiyou
Sonoma
Stanislaus
Tehema
Yuba
Santa Cruz
San Diego
Alpine
Amador
Calaveras
El Dorado
Las sen
Mariposa
Placer
Shasta
Sierra
Trinity
Tuolumne
WISCONSIN
Adams
Barren
Florence
Lang lade
Lincoln
Marathon
Marquette
One i da
Portage
Racine
Shawano
Waupaca
Waushara
Ashland
Bayfield
Burnett
Chippewa
Douglas
Forest
Iron
M
M
M
M
M
M
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
L
L
L
L
L
H
H
L
L
L
L
L
L
L
L
L
L
L
M
M
M
M
M
M
M
M
M
M
M
M
M
L
L
L
L
L
L
L
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
pattern positive
pattern positive
none/neg
pattern positive
none/neg
pattern positive
none/neg
none/neg
pattern positive
none/neg
none/neg
limited positive
pattern positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-------
11-44
Table II-8 (cont'd).
County
Vul.
Use/Usage Monitoring
Leaching Potential
H M L
WISCONSIN {cont'd)
Juneau
Marinette
Menominee
Oconto
Polk
Price
Rusk
Sawyer
Taylor
Vilas
Washburn
Wood
Mi iwaukee
Columbia
Dodge
Jefferson
Kenosha
Walworth
Brown
Calumet
Clark
Dane
Door
Dunn
Eau Claire
Fond Du Lac
Green Lake
Kewaunee
Manitowoc
Monroe
Out garni e
Ozaukee
Pepin
Rock
St. Croix
Sheboygan
Washington
Waukesha
Winnebago
H
H
H
H
H
H
H
H
H
H
H
H
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
L
L
L
L
L
L
L
L
L
L
L
L
H
M
M
M
M
M
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
pattern positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
limited positive
none/neg
none/neg
none/neg
limited positive
none/neg
limited positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
limited positive
none/neg
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sauk
M
limited positive
-------
11-45
Table II-8 (cont'd).
County
Vul. Use/Usage Monitoring
Leaching Potential
H M L
WISCONSIN (cont'd)
Buffalo
Crawford
Grant
Green
Iowa
Jackson
La Crosse
Lafayette
Pierce
Richland
Trempealeau
Vernon
NORTH CAROLINA
Beaufort
Bertie
Bladen
Camden
Carteret
Chowan
Columbus
Craven
Currituck
Duplin
Edgecombe
Gates
Greene
Halifax
Hertford
Johnston
Jones
Martin
Northampton
Pamlico
Pitt
Sampson
Tyrrell
Washington
Wayne
Wilson
Allegheny
Avery
Brunswick
Buncombe
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
M
M
M
M
M
M
M
M
M
. M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
L
L
L
L
none/neg
none/neg
pattern positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
limited positive
none/neg
none/neg
none/neg
none/neg
limited positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-------
11-46
Table II-8 (cont»d).
County Vul. Use/Usage
Mon itori nq
Leaching Potential
H M L_
NORTH CAROLINA (cont'd)
Cherokee
Dare
Hawood
Henderson
Hyde
Jackson
Lee
Macon
Madison
Mitchell
Moore
New Hanover
Onslow
Fender
Perquimans
Richmond
Swain
Transylvania
Watauga
Wilkes
Yancey
Clay
Cumberland
Harnett
Hoke
Lenoir
Nash
Pasquotank
Robeson
Scotland
Almance
Forsyth
Franklin
Granville
Guilford
Person
Rockingham
Stokes
Surry
Vance
Wake
Warren
Yadkin
Alexander
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
M
M
M
M
M
M
M
M
M
M
M
M
M
M
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
L
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
limited positive
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-------
11-47
Table II-8 (cont'd).
Use/Usage Monitoring
Leaching Potential
H M L_
NORTH CAROLINA
Anson
Ashe
Burke
Cabarrus
Caldwell
Caswell
Carawba
Chatham
Cleveland
Davidson
Davie
Durham
Gaston
Graham
Iredell
Lincoln
Mcdowell
Mecklenburg
Montgomery
Orange
Polk
Randolph
Rowan
Rutherford
Stanley
Union
(cont'd)
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
FLORIDA
Brevard H
Broward H
Collier H
Dade H
De Soto H
Glades H
Hardee H
Hendry H
Highlands H
Hillsborough H
Indian River H
Lake H
Manatee H
Marion H
Martin H
Okeechobee H
Orange H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
none/neg X
none/neg X
none/neg X
none/neg X
none/neg X
none/neg X
none/neg X
none/neg X
pattern positive X
pattern positive X
none/neg X
none/neg X
none/neg X
none/neg X
none/neg X
none/neg X
limited positive X
-------
11-48
Table II-8
-------
11-49
Table II-8
County
(cont'd).
Vul.
Use/Usage Monitoring
Leaching Potential
H M L
FLORIDA. (C0nt»d)
Suwannee
Taylor
Union
Wakulla
Walton
Washington
H
H
H
H
H
H
L
L
L
L
L
L
none/neg
none/neg
none/neg
none/neg
none/neg
none/neg
X
X
X
X
X
X
-------
11-50
C. ANALYSIS OF PUBLIC COMMENTS
All public comments submitted in response to Position
Document 1 (PD 1) published by the Agency in the Federal
Register on July 11f 1984 (49 FR 28320) were reviewed. A listing
of 245 respondents are contained in the public docket and appear
in Appendix I of this document. Comments on risk are discussed
below. Comments on benefits are reflected in Chapter III.
Respondent Number 7
Mr. Curtis Mason, Extension Pesticide Coordinator of the
Arkansas Cooperative Extension Service, indicated that the
potential for aldicarb to contaminate wells in his state is
slight because "... Most of our wells in Arkansas are deep wells
with impervious layers between the aquifer and the surface...".
Agency Response
The Agency has not performed any specific analysis of the
conditions in Arkansas. The Agency is appreciative of Mr.
Mason's comments, and will maintain them on file should a review
of Arkansas' hydrogeologic conditions be necessary in the future.
Respondent Number 33
Mr. Louis Steflik, president of Steflik Farms in Bunnell,
Florida, notes that a layer of hardpan clay lies three feet below
the soil surface. He states that this clay layer limits downward
movement of water into the water table. He further states that
tests by both the registrant and the Florida Department of
Agriculture have failed to detect aldicarb residues in shallow
wells.
Agency Response
The Agency agrees that the presence of a clay lens limits
downward movement of aldicarb into the water table. The Agency
also notes that the conditions on Mr. Steflik's farm are not
uncommon in Florida. However, the following is also true for
Florida conditions.
1) The clay hardpan lens common to Florida is not strictly
continuous in nature, that is, there are cracks and channels
through which water and pesticide residues can leach to further
depths (these channels are natural or man-made - drilling of
wells creates channels).
2) The seemingly continuous clay lenses have distinct
endpoints where recharge occurs.
-------
11-51
3) Significant areas in Florida do not have this re-
strictive clay lens and recharge to major water-bearing aquifers
is direct.
4) The hydrogeologic conditions of Florida (sandy soil and
heavy rainfall) virtually guarantee that residues will leach to
the top of the clay lens and travel horizontally off the field
site.
The Florida Department of Agriculture and Consumer Services
(DACS) has recently embarked on a rural well testing program. In
this program, they are specifically targeting drinking water
wells near aldicarb-treated fields (the current Florida law
requires users to file a "notice of intent to use" aldicarb -
which is how the Agriculture Department locates target wells).
Testing has occurred since 1984, and as of May, 1987, approx-
imately 950 samples in 11 high use counties have been analyzed
for aldicarb and its metabolites (there is approximately a
one-to-one correspondence between number of wells and number of
samples - there are more samples than wells since some samples
are second and third tests of the same wells). Thus far, six
wells in four counties have shown positive results, with a high
of 27 ppb aldicarb.
The Florida Department of Health and Rehabilitative Services
has also been conducting monitoring of drinking water wells.
They sampled approximately 50 private drinking water wells per
county, and their program is scheduled to continue through 1990.
Their objective is to get a representative sample from the
aquifer most often tapped for drinking water. As such, they have
not targeted agricultural field sites, and are not concentrating
on any specific pesticides. As of May, 1987, 308 wells in seven
counties have been sampled with no positive findings of aldicarb.
However, the Florida Department of Environmental Regulation
(DER) has been conducting comprehensive testing of specific field
sites, with assistance from the registrant. Most notable in
these field sites is the Lake Hamilton site, discussed earlier in
the ground water assessment. In this field site, a single 10
Ib/A treatment in 1983 resulted in several residue readings above
500 ppb aldicarb in the ground water beneath the field (located
approximately 15 feet deep), with one reading above 1,000 ppb.
Several readings in the 50-60 ppb range were 400 feet from the
edge of the field. Field site testing in another site showed
positives in 65 percent of the 80 samples taken in 1987. The 80
samples were taken from 25 wells equally spaced between 500 and
1,000 feet from the field edge (not all wells sampled on all four
dates). These wells tapped between five and 20 feet into the
shallow surficial aquifer. Of these 80 samples, 52 were
positive, with 39 samples above 10 ppb, and a mean positive of 57
ppb. High readings of 416 and 276 ppb were noted at 800 and 900
feet, respectively (Jones, 1987).
-------
11-52
The difference between DER and DAGS's testing is that DER's
testing involves "research-oriented" wells, which are drilled to
near the top of the water table, whereas DACS is testing existing
drinking water wells, which are almost always in deeper, more
protected portions of aquifers.
Respondent Number 66
Mr. Robert M. Rakich, president of the Arizona Agricultural
Chemicals Association, states that the likelihood of well contam-
ination by aldicarb (which is used primarily for cotton in
Arizona) is slight for the following reasons: 1) drip irrigation
is becoming more prevalent due to rising water costs and its
greater efficiency compared to other methods of irrigation, 2) 90
to 95 percent of all well water used for irrigation is extracted
from wells which are 100 to 450 feet deep, and, assuming properly
set well casings and proper back flushing valves, these wells
themselves stand little chance of contamination, and 3) the soil
pH and temperature is high, environmental conditions conducive to
aldicarb degradation.
Agency Response
The Agency agrees with Mr. Rakich, and has evaluated the use
of aldicarb on cotton in Arizona to have a "low" probability of
leaching into ground water. The Agency's evaluation was based on
hydrogeologic conditions. Mr. Rakich is also correct in noting
that drip irrigation significantly reduces the leaching of pest-
icides in comparison to other, less efficient, means of irriga-
tion.
Respondent Number 67
Mr. R.S. Edsall, president of Edsall Grove Service, Inc., in
Vero Beach, Florida, recommends that the Agency adopt Florida's
regulation that aldicarb not be used within 1,000 feet of a
drinking water well, plus continual close monitoring of wells.
Agency Response
The Agency agrees with Mr. Edsall that close monitoring of
potentially impacted wells is critical to their continued safe
use for drinking purposes.
Respondent Number 97
Dr. Roger Boron, president of Agricultural Chemical Testing
in MeAllen, Texas, has commented on the topsoil characteristics
of Hidalgo, Willacy and Cameron counties in the Lower Rio Grande
Valley of Texas. Dr. Boron states that, "Permeability of our
cropland is classed as slow, moderately slow or moderate. This
-------
11-53
means that water moves in saturated soil at rates of 0.06 to 0.2,
0.2 to 0.6, or 0.6 to 2.0 inches per hour." He also states, "We
have a few sandy areas in which permeability is classed as rapid,
6.0 to 20.0 inches per hour, but these spots are too droughty for
cropping and are used only for rangeland."
Agency Response
The Agency is in general agreement with Dr. Boron's
conclusions concerning topsoil and the probability that aldicarb
will not leach to ground water in the Lower Rio Grande Valley.
The Agency also notes that there are some areas with soils of
high permeability, but disagrees with Dr. Boron that these soils
would only support rangeland. Specifically, there is significant
acreage of farmland in Brooks, Kennedy, and Jim Hogg counties in
an area above the Rio Grande Valley known as the Rio Grande Plain
which is dominated by soils which are prone to leaching.
Examples of "soil series" (lowest classification of soils
according to soil taxonomy) typical of this area and the crops
for which these soils are suited include: Sariata (6.0-20.0 in/hr
permeability) - watermelon, peanuts, and pasture, and Fulfurrias
(6.0-20.0 in/hr) - pasture alone.
Respondent Number 98
The Natural Resources Defense Council (NRDC) presented a
number of comments pertinent to the aldicarb Special Review. The
following are the Agency's review of these comments.
Comment 1 (Pa 1)
The NRDC urges the Agency to carefully consider the
precedent of the Agency's review of ground water contamination
from aldicarb relative to contamination of ground water by other
pesticides.
Agency Response
The Agency has considered the implications of the aldicarb
Special Review relative to ground water contamination by alter-
native pesticides. The Agency's efforts in this area are dis-
cussed in Chapter IV. The reader is referred to that chapter
for a thorough discussion of this subject.
Comment 2 (Pa 2)
The NRDC recommended that the Agency change aldicarb
labeling to include restrictions on aldicarb use based on soil
type and other environmental conditions which affect leaching and
decay of aldicarb.
-------
11-54
Agency Response
The Agency has considered a wide range of regulatory
options, including the above recommended use restrictions. The
reader is referred to Chapter IV for analysis of this option.
Comment 3 (Pg 3)
The NRDC comments that past analyses did not consider expo-
sure via bathing in contaminated water and inhalation of tobacco
treated with aldicarb.
Agency Response
The Agency has not included these exposures in its risk
analysis because they represent a minute amount of exposure due
to the small amount of aldicarb residues in water used for
bathing, the percent absorption through the skin, the small
percent of tobacco crop treated, the mixing/curing of tobacco.
and the lack of a tolerance for this sec. 24(c) FIFRA use.
Comment 4 (Pg 3)
The NRDC comments that non-dietary sources of exposure should
be considered in the Special Review as well as dietary sources of
exposure.
Agency Response
The Agency considered applicator exposure initially in the
Special Review but believes that the exposure to applicators and
workers is expected to be minimal given the label statements
requiring the use of boots in treated fields (e.g., during field
irrigation) and the use of gloves in greenhouses while handling
plants. These label statements are sufficient to reduce worker
exposure and were required in the Registration Standard issued in
1984.
Comment 5 (Pa 3)
The NRDC stated that it was difficult to comment on the
appropriateness of the ADI and requested that the Agency provide
a fuller description of the different ADl's for aldicarb.
Agency Response
The Agency's Office of Drinking Water (ODW) has selected an
ADI of 0.001 mg/kg/day for aldicarb. This ADI is derived from
the NOEL of 0.12 mg/kg/day, in a six month rat feeding study with
aldicarb sulfoxide and use of an Uncertainty Factor of 100. ODW
determined that use of this Uncertainty Factor was appropriate
-------
11-55
for aldicarb because aldicarb's extremely steep dose-response
curve, high acute toxicity and possibility of concurrent exposure
to other acetylcholinesterase (ChE) inhibitors in the diet may
lead to ChE inhibition. The Agency's Office of Pesticide
Programs (OPP) has endorsed ODW's ADI for aldicarb.
However, as previously discussed, OPP believes that an acute
dietary analysis is the most appropriate way to assess the
dietary risks of aldicarb. Thus, OPP conducted its analysis for
dietary exposure to aldicarb using a reference dose from the
extrapolated NOEL for acute human ChE inhibition, and a ten-fold
uncertainty factor. A reference dose of 0.001 mg/kg was used.
Comment 6 (Po 4)
The NRDC is concerned that low level exposure to aldicarb
residues may cause subtle neurologic disorders in humans. They
cite findings from a 1982 Suffolk County, NY study suggesting an
incidence of neurological disorders among residents consuming
water contaminated with high concentrations of aldicarb. Add-
itionally, the NRDC questions whether prenatal and/or perinatal
exposure to aldicarb will impair neurological or behavioral
development.
Agency Response
The Agency's review of epidemiologic studies has not ident-
ified an association between low level aldicarb exposure and
neurologic disorders. Review and evaluation of the 1982 Suffolk
County study by epidemiologists both within and outside the
Agency failed to substantiate the claims in that report.
Although monitoring data show that persons have been exposed to
levels of aldicarb resulting in clinical signs of ChE inhibition,
there is no indication from these data or from extensive studies
in several laboratory animal species that aldicarb affects
neurological or behavioral development at such low levels.
Comment 7 (Pa 4)
The NRDC stated that it is concerned about reaction of
aldicarb with nitrates to form nitrosamines. In some areas,
nitrates are a common contaminant in ground water. Nitrosamines
are a class of chemical, many of which have shown oncogenicity in
laboratory animals.
Agency Response
The Agency is unaware of any evidence which suggests that
aldicarb and nitrates react to form nitrosamines under normal
environmental conditions. The Agency would appreciate the
opportunity to review any evidence that the NRDC might have to
support such a concern.
-------
11-56
Comment 8 (Pa 5)
The NRDC commented that most toxicology studies forming the
data base for aldicarb were conducted prior to 1974. NRDC
requested that the Agency consider whether the quality of these
studies is consistent with the October 1982 Agency Guidelines.
Agency Response
The Agency reviewed all available toxicologic data during
the Registration Standard process. The Agency cited all data
that meet current Agency guideline requirements. Toxicologic
data currently supporting the aldicarb data base, except as noted
in the Registration Standard, are sufficient to conform with
Agency quidelines. Several studies supporting the registration
of aldicarb have been conducted in the late 1970's and as recent
as 1987.
Comment 9 (Pg 5)
The NRDC encouraged the Agency to consider the inclusion of
an ongoing study on the environmental fate and health impacts of
aldicarb use on Florida citrus in the next Special Review
document.
Agency Response
The Agency has received information on several joint studies
on citrus, ferneries, and potatoes being conducted by the reg-
istrant in conjunction with the Florida Department of Environ-
mental Regulation. Summaries of these studies are included
earlier in this chapter.
Comment 10 (Pa 6)
The NRDC asked the Agency to take no action on the pending
registration of aldoxycarb, an aldicarb metabolite. It also
asked that the Agency grant no new uses of aldicarb.
Agency Response
The Agency granted a registration for aldoxycarb, but only
for use in containerized plantings, because it believes that this
use will probably not cause ground water contamination. Leaching
studies for aldoxycarb are currently underway. The Agency has
granted no registrations for new uses of aldicarb. However, NRDC
should be aware of the significant difference between the tox-
icities of aldicarb and aldoxycarb, and furthermore, that aldi-
carb degrades naturally to the less toxic aldoxycarb, but not
vice versa.
-------
11-57
Respondent Number 125
Mr. John Bolduc, with the Conservation Law Foundation of New
England, Inc., had three comments.
Comment 1 (Pa 1)
Mr. Bolduc requested that the Agency provide a brief summary
of the fate and transport characteristics of pesticides which are
alternatives to aldicarb, as well as a brief summary of toxicity
characteristics of the alternatives.
Agency Response
The Agency has provided a brief summary of the environ-
mental fate, toxicology and ecological effects of aldicarb and
its major alternatives in this Technical Support Document, in
Chapter IV.
Comment 2 (Pa 1)
Mr. Bolduc commented on the use of advisory warnings on
labels directing users not to apply aldicarb in areas with well-
drained soils. He notes that this type of label statement is
difficult to enforce.
Agency Response
In Chapter IV of this document, the various regulatory
options are discussed. The requirement for label statements is
discussed in that chapter.
Comment 3 (Pa 1)
Lastly, Mr. Bolduc requested a summary of monitoring infor-
mation for Rhode Island and citations and supporting documen-
tation for monitoring in Connecticut.
Agency Response
A brief summary of this monitoring information can be found
in Chapter II. Additional information on monitoring results for
Rhode Island can be obtained from: Aldicarb Team Leader, Exposure
Assessment Branch, Hazard Evaluation Division, Office of Pest-
icide Programs (TS^769), EPA, Washington, D.C. 20460. Citations
and/or supporting documentation for the findings in Connecticut
were not present in either the Federal Register or the Reg-
istration Standard. Messrs. Paul Marin (Dept. of Env. Pro-
tection, Water Compliance), Greg Piontek (EPA, Connecticut
Pesticide Program) and Jim Murphy (Dept. of Env. Protection) were
contacted by the Agency. These individuals were unaware of
aldicarb findings in Connecticut, and the Agency believes it
-------
11-58
reasonable to conclude that aldicarb has not been found in
Connecticut to date.
Respondent Number 134
Mr. L.O. Nelson (pesticide administrator, Indiana State
Chemist and Seed Commissioner) stated that aldicarb infiltration
and leaching depends heavily on local geology, climate and
agricultural practices. Mr. Nelson states that leaching pest-
icides are best regulated at the local level.
Agency Response
The Agency agrees with Mr. Nelson's first comment. In
reaching its proposed regulatory decision, the Agency took into
account numerous ideas provided by state regulatory agencies on
the role of local, state, and Federal regulators. In formulating
the proposed regulatory decision on aldicarb, the Agency con-
sidered regulation at the local level. The reader is referred to
Chapter IV for further discussion.
Respondent Number 141
Dr. Jeffiey Wyman, associate professor of entomology at the
University of Wisconsin-Madison, submitted detailed comments on
efficacy and a technical paper on leaching. The efficacy
comments are considered in the benefit analysis. Specifically,
the technical paper contained field studies of aldicarb applied
to potato crops in Wisconsin and addressed issues concerning
leaching potential of aldicarb in Wisconsin. There were two
studied field sites and several scenarios examined within those
sites including: permutations of application date, rate, and
irrigation scheduling. A major conclusion was that aldicarb
would not leach in one site with sandy loam soil. "...The mean
concentration of aldicarb residues at the Cameron location ...
demonstrated that residues did not leach below 1.2 m throughout
the 208-day sampling period ..." Conclusions concerning the
second site, which had a loamy sand soil, were not as
definitive."... At Hancock, no aldicarb residues were detected
below 2.4 m following the emergence application under either
medium or heavy irrigation schedules ... Small traces of aldicarb
residue were detected at the 2.4 to 3.0 m level under both
irrigation regimes following the 3.36 kg ai/ha planting applica-
tion ... Some leaching of aldicarb residues probably occurred
below the 3.0 m level in the plots treated at planting and
receiving heavy irrigation while leaching below 2.4 m did not
occur in the emergence treatments receiving medium ET based
irrigation. No conclusions could be drawn about whether leaching
occurred below the 3.0 m level in the planting application with
medium irrigation or the emergence application with heavy
irrigation ...". Leaching was indicated for some of the
scenarios tested for the loamy sand at Hancock.
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Agency Response
One method to estimate the extent of leaching is to use
computer simulation modeling programs. In fact, both these field
sites and the leaching data were evaluated with PRZM, as part of
a technical paper (Lorber and Offutt, "A Method for the
Assessment of Ground Water Contamination Potential Utilizing PRZM
- A Eesticide Boot Łone Model for the Unsaturated Zone, 1986).
In this study, PRZM was calibrated to the field data for the
loamy sand and the sandy loam site. Then, the amount of leaching
below the depth of sampling in these experimental field sites was
estimated by PRZM. Only a minor amount (0.3 percent of applied
rate) was estimated to leach below the depth of sampling for the
sandy loam site. However, aldicarb was estimated to leach below
3 m for all scenarios at the loamy sand site. For the heavy
irrigation scenarios, approximately 25 percent of the applied
rate leached below 3 m. For other scenarios, between 3.6 and
8.9 percent of applied aldicarb was simulated to leach below 3
meters. The author concluded, with these and other simulations
described in the publication, that aldicarb has the potential to
leach in field sites with soil similar to the loamy sand at
Hancock, but little potential to leach on soil types similar to
the sandy loam soil at Cameron.
Dr. Wyman did not state whether his study supported a
conclusion on the leaching potential of aldicarb in Wisconsin
soils. Rather, he concluded that, "... The changes in appli-
cation procedures for Temik, together with effective irrigation
management, cultural management techniques and intelligent state
regulation and use monitoring, thus significantly reduce the risk
portion of any risk/benefit analysis and favor the continued use
of this product." The modeling study (Lorber and Offutt, 1986)
also supports a conclusion that changes in cultural practice
(i.e. application of aldicarb later in the season) would reduce
the amount of aldicarb. However, Lorber and Offutt (1986) also
concluded that aldicarb has the potential to leach in loamy sand
soils similar to the loamy sand of the field site reported in Dr.
Wyman's publication, even when improved cultural practices are in
effect. The Agency believes that the appropriate direction to
take at this point is to determine the extent of loamy sand soils
in Wisconsin, the use of aldicarb on these soils, and current
monitoring, if any, in these areas.
Respondent Number 144
Dr. D.P. Weingartner, a plant pathologist at the University
of Florida, summarized the importance of aldicarb to potato
growers in northeast Florida (NEF) and provided detailed sum-
maries and several publications on potato diseases, nematicide
options and related aldicarb issues. He states that, "The
reasons for regulating aldicarb use due to contamination of well
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11-60
water in some locations do not appear valid in NEF flatwoods
area.n He also reports on surficial runoff from NEF potato
fields. Only these two issues (fate and transport) are con-
sidered in this response.
Dr. Weingartner presents an argument as to why it is
unlikely that drinking water would become contaminated with
aldicarb in NEF due to potato uses. He claims that, "Cultivated
flatwood soils are sublayered by a zone of weakly cemented pan to
cemented pan." This results in a situation of lateral, rather
than vertical, drainage from potato fields. Furthermore, he
claimed that artesian flow below the clay lenses do not easily
allow intrusion by solutes into the ground water. "There is
therefore a greater probability in such a system for contam-
ination of surficial runoff water during heavy rains than ground
water beneath the clay."
Agency Response
In general, the Agency agrees with Dr. Weingartner's con-
clusion that the potato agronomic practices in the potato growing
region of Florida results in a moderate potential to leach into
ground water and it is not likely to contaminate the drinking
water wells located more than 100 feet deep, primarily because of
the existence of the clay pan. The Agency notes, however, that
the top soil in NEF is sandy, as Dr. Weingartner recognizes, and
confirmed by Florida soil maps. Therefore, aldicarb has a high
probability of leaching to the cemented clay layer located three
to six feet below the soil surface. Dr. Weingartner does not
provide information on the extent of this clay layer. His
rebuttal states, "... presence of an impervious zone of clay
sublayering most NEF fields ...". "Most" has not been defined by
the author. Aldicarb contamination of ground water is likely to
be a problem to the extent that there is any extraction of
surficial water from above the clay lenses, for drinking water or
otherwise. The only positive aldicarb sample came from a
surficial aquifer beneath a potato field. Further, ground water
contamination is also possible under treated fields if the clay
layer described by Dr. Weingartner is not present.
In summary, Dr. Weingartner presents a strong argument
against the possibility of ground water contamination in NEF from
aldicarb use on potatoes. He acknowledges aldicarb»s mobility
with evidence of surface runoff into the Deep Creek system and
concentrations of aldicarb (1.1 ppb) at the inlet to the St.
John's River in Florida. Since aldicarb is mobile, it will move
with water. Dr. Weingartner shows why it is more likely to move
with surface runoff rather than ground water recharge.
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Respondent Number 146
Dr. John M. Harkin, Associate Director of the Environmental
Toxicology Center, University of Wisconsin, provided a study
entitled, "Aldicarb in Groundwater." The submitted study
summarizes results of field monitoring of aldicarb used on
potatoes over the Central Sands Aquifer. Dr. Harkin acknowledges
the inevitability of ground water contamination of the Central
Sands Aquifer from aldicarb use, "the contamination of ground
water by aldicarb residues has created some minor localized
problems in Wisconsin, but these are neither unsurmountable nor
permanent."
Dr. Harkin presents a case indicating that aldicarb will
contaminate the Central Sands Aquifer when used on potatoes.
However, the primary contamination will occur near the surface of
the water table and degradation of aldicarb in the ground water
will prevent it from contaminating deeper portions of the
aquifer. He believes that aldicarb use should continue with the
following precautions: 1) all wells in construction should be
completed to deep portions of the aquifer, 2) selected wells
should continually be monitored, 3) contaminated well water could
possibly be handled by consumers of the water by baking soda - "A
tiny pinch of baking soda can be added to water before boiling to
prepare hot beverages ...The ease of hydrolysis of aldicarb
provides a cheap, convenient method of removing it from drinking
water ...", 4) careful irrigation practices should be practiced,
and 5) studies of aldicarb movement should continue.
Agency Response
The Agency agrees with four of the five conclusions, but
does not believe that baking soda is an adequate means to handle
contaminated ground water. Dr. Harkin believes that use in
Wisconsin should continue, but with proper precautions, assuming
that ground water contamination is a price of progress. The
Agency believes that there are many similarities between the
Central Sands of Wisconsin and Long Island, New York, suggesting
that the same regulatory strategy should be carried out in both
places. Some of these similarities include:
1. Strong dependence on ground water for drinking water.
2. Shallow water table.
3. Sandy soils overlying the shallow water table.
4. Cool, wet climate which decreases pesticide degra-
dation (cool climate) and the likelihood of transport
(wet climate).
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11-62
5. Dependence on aldicarb in an extensive potato growing
region.
Respondent Number 157
Mr. James Graham (commissioner, Department of Agriculture,
North Carolina) supports continued use of aldicarb on tobacco and
ornamentals in North Carolina. He summarized the registrant's
data in North Carolina, which includes the results of monitoring
of 23 wells in Northampton and Halifax counties in 1980 and 1981.
Although the total number of samples was not given, only two
samples were positive, one sample showing 1 ppb and another
showing 2 ppb. In addition, he submitted data from the North
Carolina Department of Agriculture (NCDA) which sampled wells in
Cumberland, Edgecombe, Gates, Halifax, Martin, Northampton, Pitt
and Scotland Counties in 1983. Seven samples from 104 wells were
positive, with two samples from Scotland County containing 28.2
and 27.6 ppb aldicarb and three containing 2 ppb. Three samples
from Halifax County contained trace levels of aldicarb, estimated
at less than 1.5 ppb. All wells sampled by NCDA were verified to
be less than 600 feet from fields using aldicarb.
Mr. Graham recommends that, "... future registration of
aldicarb or any other water soluble mobile pesticides be
conditioned upon the establishment of a structured monitoring
program developed and supervised by the Agency. Further, we
recommend that, at registration, it establish maximum allowable
levels for any pesticide likely to impact ground water so that
such monitoring could have a meaningful impact."
Agency Response
The data submitted by Mr. Graham were considered in the
development of the ground water vulnerability assessment.
Aldicarb has a Health Advisory Level (HA) of 10 ppb.
Respondent Number 180
Mr. Thomas J. Dawson, Public Intervenor with the Wisconsin
Department of Justice, submitted extensive comments detailing his
efforts on aldicarb dating back to 1981. His submission contains
eight appendices and concludes that S Ag 29.17 Wis. Adm. Code,
governing the present use of aldicarb, is a failure.
Section Ag 29.17 Wis. Adm. Code which was .adopted in 1982,
imposes restrictions on continuing aldicarb use, rather than a
State-wide moratorium, to "prevent aldicarb residues in ground
water from reaching a level exceeding 10 ppb" and to "afford an
opportunity for groundwater quality recovery.*1 Further, the rule
is based on the requirement that "adequate monitoring and testing
of groundwater supplies would be done, intensive research would
be conducted to refine the regulatory scheme, and that the rule
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11-63
would not be the final word on the aldicarb contamination issue."
Briefly, the regulatory components of 5 Ag. 17 are:
1. Aldicarb shall be used at a rate no higher than 2 Ib/A
and should be used only in alternate years on a site.
2. Aldicarb shall be applied only by certified applicators.
3. Aldicarb shall be applied between 28 and 42 days fol-
lowing planting, and fields treated by aldicarb shall
be harvested no sooner than 50 days following applica-
tion.
4. No person may apply aldicarb unless a report of intended
application has been filed with the department at least
30 days before the pesticide is applied.
5. The State of Wisconsin has the right to prohibit the
intended application of aldicarb with a "summary spe-
cial order" if "the intended application site is lo-
cated within a township quarter-quarter section lying
wholly or in part within one mile of a sample point
at which aldicarb residues have been detected at
a level exceeding 10 ppb." Exemptions to a "summary
special order" are listed in Ag 29.17.
6. Distributors and retail dealers of aldicarb shall keep
records and report sales of aldicarb.
7. All findings of aldicarb in ground water at levels of
1 ppb or more shall be reported to the proper
authorities.
Mr. Dawson believes that, "Ag 29.17 has failed to prevent
aldicarb residues in ground water from reaching unacceptable
levels, that ground water quality in Wisconsin is not recovering
from its aldicarb contamination as hoped, and that there is no
credible evidence showing that the label and use-restrictions are
adequate to protect Wisconsin's ground water ... The Wisconsin
"experiment" has been tried, and it has failed."
The major evidence on which Mr. Dawson bases his contention
is the result of the sampling of 144 drinking water wells for
aldicarb in June of 1984 by the Wisconsin Department of Natural
Resources (DNR) and the Portage County Department of Health. The
results of this survey are: 82 wells showed positive findings,
33 of which were above the 10 ppb level, with a high reported
value of 69 ppb. In addition, "Of wells with previous residue
histories, about 22 were seen to decrease, 11 increased and 36
remained near the same." Mr. Ron Becker of DNR states, "No
distinct overall downward trends were apparent from the June
data ... Aldicarb is moving with the groundwater and has been
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11-64
seen to contaminate new areas as it moves." Mr. Dawson also
believes that other intentions of Ag 29.17 were not met as of
September 1984: "... although groundwater monitoring has
occurred, it has been far from adequate to obtain a fair and
complete picture of the extent to which Wisconsin groundwater is
contaminated by aldicarb residues. At best, the results of the
latest monitoring provide an extremely conservative indication of
contaminated areas."
Agency Response
It is impossible to judge from available data what impact
the Wisconsin restrictions have had on the extent and level of
aldicarb contamination of ground water. It is clear, however,
that ground water contamination continues to be found in
Wisconsin despite these restrictions. Thus, one cannot conclude
that they are completely successful.
The Agency agrees with Mr. Dawson that "... questions about
how aldicarb residues are acting in already contaminated
groundwater, remain unanswered." A recent study by Dr. Miles
(University of Florida) indicates that aldicarb sulfoxide reduces
to aldicarb sulfide under Florida ground water conditions. This
would support the contention that in some conditions aldicarb
persists longer in ground water than previously thought.
Respondent Number 186
Mr. C.D. Besadny, Secretary of the Wisconsin Department of
Natural Resources (DNR), submitted a computer printout summar-
izing the results of testing 840 wells in Wisconsin as of March
1984 for aldicarb residues. In addition, he submitted two
communications between the DNR and Department of Health and
Social Services (DHSS) to the Department of Agriculture, Trade,
and Consumer Protection (DATCP).
Some concerns expressed by DNR and DHSS in their first
letter to DATCP dated August 10, 1982 were not adequately met in
the law governing aldicarb, Ag 29.17. Both agencies preferred
to see a moratorium on aldicarb use when residues are found at
some fraction of the Suggested No Adverse Response Level (SNARL;
this level is not defined in the letter and it is assumed that
SNARL is also 10 ppb), rather than above the SNARL. AG 29.17
reads:
"Aldicarb applications are subject to
prohibition ... if the intended application
site is located within a township quarter-
quarter section lying wholly or in part within
one mile of a sample point at which aldicarb
residues have been detected in ground water at
a level exceeding 10 parts per billion ..."
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11-65
The "purpose" language of Ag 29.17 regarding "2 to 10" ppb
addresses this concern but does not allow for a moratorium.
This letter also addressed a concern that "... The proximity
to irrigation wells should not be a basis for disregarding a
sample. The only criterion should be whether the sample is
indicative of ground water quality. A landowner's rights should
be preserved to assure that he may construct a future well which
will provide a safe water supply." Ag 29.17 reads:
Samples shall not be drawn from a high
capacity irrigation well, or any well located
within 300 feet of a high capacity irrigation
well."
Mr. Besadny suggested that the proposed rule "... require
review after one or, at most, two years allowing for additional
data from research and sampling and input the Legislative
Council's Special Committee on Groundwater Management ..." This
concern was handled in a general manner in the "purpose" section,
which said that "The department shall evaluate the need for
further actions ... when groundwater samples are found to contain
aldicarb residues at a level from 2 to 10 parts per billion."
Agency Response
In the data submitted by Mr. Besadney, of the 840 tested
wells, 180 have shown at least a detectable concentration of
aldicarb, and 75 have produced at least one sample result with an
aldicarb concentration over 10 ppb.
Respondent Number 188
Mr. J.E. Legates, Dean, School of Agriculture and Life
Science, North Carolina State University, summarizes a survey by
the North Carolina Department of Agriculture in 1982 and 1983 of
drinking water wells in or adjacent to treated fields of cotton,
peanuts, and tobacco. Aldicarb residues of 1 to 2 ppb in seven
of 104 wells. He notes that the HA is 10 ppb.
Agency Response
While this evidence would seem to indicate that the pop-
ulation served by these drinking wells is in no immediate danger,
it is difficult to extrapolate further without knowledge of: 1)
depth of these wells, 2) soil type and geology where the samples
were taken, 3) if these wells were "deep", are there also
"shallow" wells used for drinking water, and so on.
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Respondent Number 191
Ms. Lori Johnston, former Assistant Director, Pest Manage-
ment, Environmental Protection and Worker Safety, Department of
Food and Agriculture, California, comments that "we believe
aldicarb is being used safely in California." She notes that
aldicarb was banned in Del Norte county, due to a "combination of
high rates of use, permeable soils, low pH, cool temperatures,
and a shallow water table." She notes that other aquifers over
which aldicarb is being used have been sampled with no findings.
She states that, "If the mechanism of pesticide mobility through
soil to ground water was understood, it might be possible to
print restrictions on the label which would be simple but
accurate enough to" eliminate the possibility of residues in
ground water."
Agency Response
The Agency agrees that the factors identified by Ms.
Johnston as conducive to the leaching of aldicarb in Del Norte
county are factors which increase the likelihood of aldicarb
reaching into the ground water. In Chapter IV, in the proposed
regulatory options section, there is a discussion of using label
restrictions as a means for reducing ground water contamination.
Respondent Number 192
Dr. James P. McKeown, Cotton Entomologist, Jackson,
Mississippi, briefly commented on the continued use of aldicarb,
and does not think there will be a ground water contamination
problem "since the ground water in my area is at least 150 feet
below the surface."
Agency Response
The Agency believes that Dr. McKeown*s statement is not
correct as a generalization for the state of Mississippi, nor for
counties in the state where aldicarb is used. As part of the
exposure assessment for ground water described in this document,
six counties in Mississippi were evaluated on an average basis
for the depth to ground water. On a scale of 1 to 5, (where 5 =
high vulnerability: 0-25 feet below the surface, 3 = medium:
25-50 feet below the surface, and 1 = low: greater than 50 feet
below the surface), results for the Mississippi counties were as
follows: Tallahatchie - 4.8; Bolivar - 4.5; Washington - 3.6;
Yazoo - 2.5; Sunflower - 2.4; and Warren - 1.2. Of these six
counties, Yazoo and Sunflower had significant land area rated
either high or medium such that the average results were 2.5 and
2.4, respectively. Only Warren County, with an average rating of
1.2, can be considered to have low vulnerability as measured by
depth to ground water. It might be noted that Jackson is in
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11-67
Hinds County, which is adjacent to Warren County, so it is quite
possible that ground water is, in fact, deep in Dr. McKeown's
area.
Respondent Number 221
Mr. G. Talmadge Balch, Pesticide Education Specialist,
Alabama Cooperative Extension, Auburn University, commented
mainly on the benefits from the present use of aldicarb on
peanuts, soybeans, pecans, sweet potatoes, Irish potatoes, and
cotton. Additionally, Mr. Balch notes that there is little
danger due to worker exposure, citing its safety record in
Alabama. He also briefly describes a small monitoring program in
order to address issues of potential ground water contamination.
Agency Response
Insufficient data were submitted to draw any conclusions
about the potential for and/or existence of ground water contam-
ination in Alabama. Useful information would include: depth of
water extraction, depth to ground water, surface soil type in the
neighboring cotton fields, etc. Soil type and hydrogeologic
conditions in all areas of Alabama where aldicarb is used are
necessary to determine the potential for ground water contam-
ination in state.
Respondent Number 232
Mr. La Verne Ausman, Secretary of State of Wisconsin
Department of Agriculture, Trade and Consumer Protection, notes
that implementation and enforcement of State regulations re-
stricting aldicarb use in Wisconsin have worked effectively. He
states, though, that the effectiveness of these regulations will
not be determined for several years. He believes that state, as
opposed to Federal, regulation provides an adequate means to
mitigate ground water contamination. Mr. Ausman provided a
number of attachments, including monitoring and fate data.
Agency Response
The Agency has utilized the data supplied by Mr. Ausman in
its risk analysis for aldicarb. The Agency has also contacted
state regulatory agencies to determine the most appropriate
regulatory strategy for aldicarb. The reader is referred to
Chapter IV, Regulatory Options.
Respondent Number 236
Dr. John M. Harkin, Professor of Soil Sciences and Water
Resources, Wisconsin Resource Center, provided monitoring data.
He stated that up to 200 ppb of aldicarb residues have been
observed to date, but that observations of aldicarb in ground
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11-68
water proved to be erratic. He provided numerous observations of
environmental parameters associated with aldicarb contamination.
He closed by stating that the regulatory and remedial actions
taken by the states appear to be adequate.
Agency Response
The Agency has utilized the data supplied by Dr. Harkin in
its risk analysis for aldicarb. The Agency has also contacted
state regulatory agencies to determine the most appropriate
regulatory strategy for aldicarb. The reader is referred to
Chapter IV, Regulatory Options.
Respondent Number 242
The registrant submitted its rebuttal comments which consist
of two appendices. Appendix I specifically addresses Agency
statements presented in the PD 1. Appendix II specifically
addresses risk, exposure and benefits associated with aldicarb in
a narrative fashion, with six volumes of benefits data on
selected crops.
Appendix I
Comment 1
The registrant agreed with the Agency that aldicarb has been
detected in ground water in a large number of States. The
registrant states that the vast majority of tested wells had no
detectable aldicarb residues and that a small percentage of
drinking water wells contained residues above the HA.
Agency Response
The Agency agrees that the majority of tested wells had no
detectable residues of aldicarb. In a compilation of ground
water samples (not wells), the Agency estimates that approx-
imately one-third of the samples were positive. The Agency also
agrees that aldicarb may be the most extensively studied
pesticide, relative to ground water contamination. It must be
noted, though, that approximately two-thirds of the over 35,000
well water samples are from one locality, Long Island. Addition-
ally, most ground water testing for aldicarb has been from
drinking water wells and primarily after ground water contamin-
ation has been detected. The Agency has concluded that, while
ground water contamination by aldicarb may have been extensively
studied, the current data base has not been derived in an
organized and statistically valid fashion.
The Agency agrees with the registrant that the vast majority
of well water samples contain aldicarb residues below the Health
Advisory. The Agency disagrees with the registrant's statement
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that only eight states have detected aldicarb residues above the
Health Advisory. The Agency's review indicates that ten states
have detected aldicarb residues at greater than or equal to the
Health Advisory. The important difference between the data bases
examined by the registrant and the Agency is that the registrant
examined drinking water wells only, whereas the Agency examined
all ground water sampling results that were indicative of ground
water quality in impacted aquifers; the first-encountered aquifer
in the vacinity of the use site. These included results from
drinking water wells, and also observations on other wells not
used for drinking water purposes. The Agency, though, does not
believe it necessary to concentrate on the amount of aldicarb
residues in any particular well. The Agency believes that it is
not necessarily possible to correlate a level of residue contam-
ination with the vulnerability of a specific location at this
time.
Comment 2
The registrant questioned the Agency's statement in the PD 1
that: "... Aldicarb sulfoxide and aldicarb sulfone ... persist
longer under anaerobic conditions — than under aerobic
conditions." The registrant cites two studies which show the
reverse trend, that persistence is longer in aerobic conditions
than in anaerobic conditions.
Agency Response
The registrant statement regarding degradation is accurate.
The Agency does not state that aldicarb sulfoxide and sulfone
persist longer under anaerobic conditions than aerobic
conditions. The Agency refers to laboratory experiments which
show rapid degradation of aldicarb and aldicarb sulfone under
anaerobic conditions. However, it also references studies
performed in Florida with Floridian ground water. Ground water
is considered an anaerobic environment. In these experiments,
the persistence of aldicarb and the sulfoxide and sulfone
degradation products were studied with and without limestone
aquifers (the Floridan Aquifer is a limestone aquifer). Of six
comparisons between half-lives (three products, two comparisons
each), five demonstrated longer half-lives under anaerobic
conditions by a significant amount.
The statement, as originally made by the Agency, was made in
recognition that microbial decay, which predominates in the
aerobic environment of the root zone of crops, is a more robust
degradation process (in that it leads to shorter half-lives) than
chemical hydrolysis which predominates in the anaerobic environ-
ment of the ground water. Exceptions to this rule occur (as
noted in two cited references) when anaerobic microorganisms
promote rapid degradation of aldicarb products.
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Comment. 3
The registrant contends that aldicarb residues exceeding the
Health Advisory have not been identified in Missouri, but have
been seen in Rhode Island. The registrant reiterates that "over
91 percent of all "worst case" wells analyzed show no detectable
levels of aldicarb residues; approximately 1.4 percent exceed 10
ppb and less than 0.6 percent exceed 30 ppb." The registrant
adds that the highest detected aldicarb residue outside of Long
Island is one well at 75 ppb.
Agency Response
The Agency has completely rereviewed its entire monitoring
data base for aldicarb. The registrant is correct that aldicarb
residues have not been detected in Missouri, but have been
detected in Rhode Island. The Agency cannot comment on the
percent of "worst case" wells with no detectable residues because
the registrant has not defined "worst case". The Agency notes
that approximately 15 percent of all samples (not wells) outside
of Long Island contained detectable aldicarb residues greater
than the Health Advisory Level. According to the Agency
compilation, two percent of samples outside Long Island exceed 30
ppb. The registrant's statement that "... the maximum aldicarb
residue in drinking water wells outside Long Island is one well
at 75 ppb." is correct. Much higher levels, however, have been
found in other monitoring. The Agency has determined that
aldicarb residues have been identified in one sample at greater
than 1,000 ppb. That sample was obtained by the registrant from
beneath a citrus field test site. That site was, though, experi-
mental with an application rate twice that currently permitted on
Florida citrus. Additionally, residues of several hundred ppb
were found beneath and downstream from other citrus field sites
that were jointly monitored by the registrant and the Florida
Department of Environmental Regulation.
Comment 4
The registrant commented on the Agency's statement that
levels of aldicarb up to 500 ppb have been found in New York.
The registrant stated that residues were, in fact, 515 ppb and
that residues had declined to 108 ppb as of .September 1984. The
registrant continued by stating that "Of the 445 wells sampled
during the last year, the highest reading has been one well at
207 ppb." The registrant stated that 25 percent of "worst case"
wells had detectable aldicarb residues, with 6 percent of these
"worst case" wells containing 30 ppb. Other New York findings
indicated that only three wells exceeded the Health Advisory
Level.
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Agency Response
The Agency agrees that 515 ppb, not 500 ppb, is the correct
highest level of detected aldicarb residues in New York. The
Agency agrees that the level of contamination has declined since
the 515 ppb level was detected. It must be noted, though, that a
decline in residues can be attributed either to degradation or
to plume movement away from the well. Thus, the cause for a
decline in residues is more important than just stating that the
residues have declined over time. Generally, the Agency believes
that aldicarb residues on Long Island have degraded over time.
Data indicate that plumes of aldicarb residues in Long Island
ground water have moved both laterally off-site and vertically
down to deeper aquifers.
Comment 5
The registrant commented on the Agency's statement that 1 to
10 ppb of aldicarb had been detected in Arizona, Connecticut,
Florida, Washington, South Carolina and possibly other States.
The registrant stated that "States which at last analysis had
(aldicarb residues within) drinking wells..." (emphasis added)
were: Arkansas, Florida, Idaho, North Carolina, South Carolina,
Texas and Washington.
Agency Response
Since the PD 1 was issued, additional monitoring for aldi-
carb has taken place, and hence, more information was available
for analysis in this document. The Agency has specifically
focussed on monitoring results which characterize "impacted"
aquifers associated with aldicarb use. "Impacted" can be defined
as the first encountered aquifer in the vicinity of treated
fields. As such, the Agency's compilation has evaluated rural
drinking water well surveys as well as research oriented
monitoring. Currently, positive results have been found in 48
counties in 16 states.
Comment 6
The registrant disputed the Agency's generalization about
typical degradation rates of aldicarb as being incorrect. The
registrant supplied information to rebut the Agency's statement:
"Because aldicarb residues have half-lives as long as several
years, under conditions typically found in ground water, the time
required for degradation of aldicarb ground water residues to
nontoxic compounds will be long." The registrant then concludes
that "Therefore, in most areas where aldicarb is used, residues
do not persist from year to year."
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11-72
Agency Response
The Agency agrees that the quoted statement is not an
accurate conclusion about degradation under typical conditions.
It is, however, true that in some places the half-lives can be as
long as several years. The data from Long Island, for example,
show that residues have persisted there through 1985 despite
discontinuation of aldicarb use since 1979.
Comment 7
The registrant commented that the Theoretical Maximum
Residue Contribution (TMRC) to the daily diet overestimates
pesticide residue exposure and that exposure is considerably
lower.
Agency Response
The Agency agrees that the TMRC for aldicarb overestimates
dietary exposure. The Agency's assessment of dietary risk is
presented in an earlier section of Chapter II of this document
and utilizes the Tolerance Assessment System.
Comment 8
The registrant commented that the Agency should maintain the
Allowable Daily Intake (ADI) at 0.003 mg/kg/day.
Agency Response
A description of the acceptable daily intake (ADI) for
aldicarb is found earlier in the Agency's response to the NRDC
(Respondent Number 98).
In a human study performed by the registrant, four men/dose
each consumed 0.025, 0.05, and 0.1 mg/kg aldicarb in 100 ml of
water. The high dose produced clear, spontaneously reversible
signs of cholinesterase inhibition. The middle dose produced no
clinical signs, although one man complained of a runny nose.
This dose inhibited ChE activity. The lowest dose also inhibited
ChE activity. The Agency determined that the LOEL and NOEL for
clinical signs are 0.1 mg/kg and 0.05 mg/kg, respectively. The
LOEL for ChE inhibition in this study is 0.025 mg/kg. The NAS
extrapolated the NOEL for whole blood ChE inhibition to be 0.01
mg/kg, and the Agency uses this value in its calculations. A
safety factor of 10 applied to the extrapolated NOEL for ChE
inhibition yields an RfD of 0.001 mg/kg. Thus the RfD for acute
and chronic ChE inhibition are comparable. This estimate is
further supported by several studies in rats, dogs, monkeys, and
rabbits; all of which show a uniform cholinergic response
demonstrating a ChE NOEL at or near 0.01 mg/kg.
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11-73
The doses estimated from the human incidents reported have
been as low as 0.0026 mg/kg body weight. These estimates are
based largely on anecdotal data on consumption, and rarely have
analyses for aldicarb been done on the items consumed. Thus
there is considerable uncertainty regarding these estimated
doses.
The human study previously described (Dernehl and Block,
1971), which found a LOEL and NOEL for clinical signs of 0.1
mg/kg and 0.05 mg/kg, respectively, was based on four subjects
per dose. Thus, there is some uncertainty regarding these values
as well. The frequency of dose estimates from incidents that are
at least an order of magnitude lower than the 0.1 mg/kg LOEL
reported indicates that the true LOEL for clinical signs is
probably lower than this, and that the NOEL reported by Dernehl
and Block could well be an effect level for some individuals.
The NOEL for ChE inhibition extrapolated from this study, 0,01
mg/kg, may also be high as monkeys fed 0.005 mg/kg aldicarb had
slightly depressed ChE (Union Carbide, 1987a and 1987b); no
clinical signs were reported at this dose under controlled
laboratory conditions. The Agency believes that the NOELS for
ChE inhibition and clinical signs of such inhibition are close to
0.01 mg/kg and that at 0.001 mg/kg, it is unlikely that an
individual will show clinical signs or have depressed ChE
activity.
Comment 9
The registrant commented that "... realistic exposure to
aldicarb residues is negligible, as can be confirmed by examin-
ation of FDA market basket surveys. As shown in monitoring
reports, actual exposure to aldicarb residues in drinking
(emphasis added) water is also extremely low. Careful considera-
tion of actual exposure to aldicarb residues should be given."
Agency Response
The Agency is concerned with making the best possible
estimate of likely exposure in determining the potential risk
from aldicarb usage. The Agency has reviewed FDA residue data.
These data confirm that potato residues in the market place
closely parallel residue data developed to establish the aldi-
carb tolerance on potatoes. The FDA data do not confirm the
citrus residue data used to establish the citrus tolerance. The
Agency believes, though, that the small sample size taken by FDA
would make finding aldicarb treated commodities difficult. Rela-
tive to actual exposure, the Agency has concluded that several
hundred parts per billion of aldicarb have been found in ground
water.
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11-74
Appendix II - Chapter One
Comment 1 (Pa 1)
The registrant stated that the Agency intends to "...deter-
mine an acceptable level of aldicarb residues in drinking water,
commonly referred to as the Health Advisory Level (HA)."
Agency Response
The HA is established in accordance with established Agency
guidelines. The Agency believes that these levels are consistent
with the guidance in FIFRA for assessment of risk. Further, the
Agency believes that situations will occur rarely where benefits
exceed this level of risk.
Comment 2 (Pg 4)
The registrant stated that the appropriate HA for aldicarb
is "...30 ppb based on EPA's ADI or 50 ppb based on the World
Health Organization ADI for aldicarb."
Agency Response
The registrant has incorrectly calculated the HA for
aldicarb by using the Agency's past ADI of 0.003 mg/kg/day and
not the current ADI of 0.001 mg/kg/day.
Comment 3 (Pg 5)
The registrant stated that, based on human and test animal
studies, the HA derived by the Agency is extraordinarily
conservative.
Agency Response
The Agency believes that the HA for aldicarb is approp-
riately conservative because water represents a large portion of
the diet, especially an infant's and child's diet.
Comment 4 (Pa 6)
The registrant states that aldicarb degrades, under approp-
riate environmental conditions, in the soil. A supplementary
document describes the microbial degradation of aldicarb, in-
cluding environmental factors enhancing and retarding this
process. The registrant states that the half-lives of aldicarb
and its metabolites range from four to eight weeks.
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11-75
Agency Response
Because of aldicarb's environmental fate characteristics, it
is highly mobile and leaches out of the root zone into other
portions of the unsaturated zone and into the saturated zone.
The registrant fails to address degradation in the saturated
zone. Degradation in this zone is considerably slower than root
zone degradation. While consistent with the discussion of
aldicarb fate and transport, the registrant does not clarify that
this half-life is associated only with microbial decay which
occurs in the root zone of crops. The registrant states that
microbial decay predominates near the soil surface, and that
hydrolysis is the major mode of degradation several feet below
the surface. The registrant does not mention the hydrolysis
half-life, which is significantly longer than microbial half-
lives. Hydrolysis half-lives range from months to years.
Comment 5 (Pg 6)
The registrant states that evaporation can be "an important
factor in limiting downward movement (of aldicarb)-n The regi-
strant also supplied, in a separate document, four references
supporting a conclusion concerning the importance of the upward
movement of aldicarb. Specifically these documents stated that,
"In most agricultural soils, these movements result in little or
no net loss of aldicarb from surface soils due to leaching."
These documents are unpublished studies by the registrant pre-
viously unavailable to the Agency.
Agency Response
To some extent, evaporating water near the soil surface will
play a role in retarding leaching. In a recent modeling study,
(Lorber and Offutt, 1986), evaporating water was listed as one of
four reasons why aldicarb appeared to be staying near the soil
surface longer than would be expected. However, the energy
necessary to pull water upward against gravity is high and would
negate the possibility of this process being significant, if at
all present, lower than a foot below the surface. Since aldicarb
is soil incorporated, residues easily move below a depth where
upwardly moving evaporating water can affect its movement. Thus,
evaporation does not play a significant role in leaching
retardation.
Comment 6 (Pg 7)
The registrant stated that aldicarb "...residues typically
remain in the upper portion of the affected aquifer immediately
beneath or within a short distance down gradient from treated
sites...Aldicarb residues continue to degrade in the saturated
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11-76
zone, with halflives ranging from a few days up to three years,
depending on conditions."
Agency Response
The registrant's statement that residues remain in the upper
portion of the aquifer, immediately below or a short distance
down gradient from treated fields, while generally true, ignores
conclusions of studies performed in Long Island and Florida. The
Long Island study indicates that aldicarb residues are appearing
in deep wells. Data from Florida indicate that aldicarb residues
have moved several hundred feet off-site. In one field site,
residue levels at 416 and 276 ppb were noted at 800 and 900 feet,
respectively. The half-life in Long Island well water has been
estimated at 5.8 years, with a range of 170 to 4,580 days.
Conditions in individual aquifers will alter the half-life
estimates.
Comment 7 (Pa 7>
The registrant states that " — exposure to birds and wild-
life is even more limited since their drinking water is from
surface water sources where aldicarb residues are unstable." The
registrant generally discusses that granular aldicarb is soil
incorporated to minimize potential surface runoff.
Agency Response
Several studies indicate only the amount of pesticide in the
first few centimeters of soil are available for loss via runoff.
However, aldicarb has been found in surface waters in Florida.
In a Congressionally mandated study of drinking water wells in
Florida, no aldicarb was found in wells, but aldicarb was
detected in a river supplying drinking water in Lee County,
Florida. These residues could have appeared in the river either
from runoff or through ground water recharge of the river. The
registrant submitted study indicated that runoff of aldicarb
would not be a problem, although they stated that "total toxic
residues in the runoff water did not exceed 1 ppm." Realizing
that 1 ppm is two orders of magnitude higher than the HA, runoff
from treated fields is a matter of concern. Still, as the
registrant pointed out, these levels were the result of broadcast
application followed by flooding and as such, were highly
atypical of aldicarb use.
Comment 8 (Pa 8)
The registrant states that only shallow wells that are down
gradient from a treated field and pulling water from the upper
portion of the water table are likely to draw contaminated ground
water.
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11-77
Agency Response
The Agency's review of the entire monitoring data base for
aldicarb clearly indicates that aldicarb contamination has
occured in shallow aquifers and that aldicarb residues, under
appropriate conditions (e.g. Long Island), can migrate to deeper
aquifers.
Comment 9 (PQ 8)
The registrant states that aldicarb degrades to non-
detectable levels "within a relatively short and predictable
distance from the point of entry."
Agency Response
The registrant, while correct that aldicarb degrades to non-
detectable levels, has failed to define "relatively short".
Porter (1984) identified aldicarb residues 4,000 feet from an
application site in Wisconsin. The Florida DER has, by con-
trast, established a 1,000 foot drinking water well setback. The
Agency agrees that current technology can be utilized to estab-
lish a rough estimate of the travel distance from the point of
application to and through a shallow, unconfined aquifer, given
adequate knowledge of the appropriate parameters, and adequate
data to verify projected travel distances.
Comment 10 (Pa 9)
The registrant states that "Properly constructed and located
wells are not likely to draw water from the upper portions of a
aquifer."
Agency Response
The Agency believes that the registrant's statement is
relevant to new wells, assuming they are constructed to penetrate
the aquifer at a deep point. The Agency cautions, though, that
it is unlikely that a significant proportion of currently
operated drinking water wells are either properly constructed or
located to intercept a plume. The Agency also doubts that well
owners have the appropriate information about their own wells.
Comment 11 (Po 9)
The registrant states that the national population in
general is not exposed to aldicarb residues in its drinking
water.
-------
11-78
Agency Response
While the Agency agrees that the majority of the population
does not consume drinking water with detectable residues of
aldicarb, the Agency is concerned about the potential for
exposure to individuals in hydrogeologically vulnerable areas.
Comment 12 (Po 10)
The registrant maintained that contamination of drinking
water wells above the HA represent isolated incidents.
Agency Response
The Agency agrees with the registrant that wells contam-
inated with aldicarb above the HA are isolated, but also believes
these contamination incidents might have significant health
impacts. Also, monitoring to date has also been comparatively
isolated.
Comment 13 (Pg 12)
The registrant states that aldicarb residues in shallow Long
Island aquifers have decreased over time and that residues in
deeper aquifers are "less apparent"-
Agency Response
Porter, et al (1984) supports the registrant's contention
that residues in shallow wells have decreased over time. How-
ever, the same study also indicates the residues have increased
in deep wells. Hence, the Agency disagrees that residues in
deeper aquifers are "less apparent".
Comment 14 (Po 12)
The registrant states that "...label changes have been
effective in reducing potential movement of aldicarb residues to
ground water" in Wisconsin and Florida.
Agency Response
The Agency has reviewed data and comments from both states
on the effectiveness of label restrictions to mitigate aldicarb
contamination of ground water. The Agency is not convinced that
these label restrictions are necessarily effective. While the
label restrictions in these states have reduced the amount of
aldicarb that enters ground water, the important point is whether
these additional restrictions have reduced residues below a
toxicologically significant level. The Florida Department of
Agriculture Jias been monitoring wells near fields with registered
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11-79
known use of aldicarb, and, as of early 1987, have found only a
few positives. However, the Florida DER, in cooperation with the
registrant, have established monitoring wells in or near aldicarb
use sites and have positive readings of up to 300 ppb in wells as
much as 400 feet from the application site. Wisconsin, by con-
trast, established a program specifically to test the effect-
iveness of its new regulations. Data from Wisconsin indicate
that label restriction may be insufficient to reduce contam-
ination of shallow potable aquifers in highly vulnerable
environments below a toxicologically significant level.
Comment 15 (Pa 14)
The registrant states no adverse effects and no unreasonable
adverse effects have been observed from consumption of contami-
nated drinking water or ground water, respectively.
Agency Response
The premise of this statement is that no organized effort
currently exists for identifying an association between clinical
signs of aldicarb intoxication and exposure to low levels of
aldicarb residues in ground water. The lack of observed effects
does not preclude the existence of effects. Finally, and most
importantly, it is not the Agency's policy to wait for observed
effects before taking a regulatory action.
Comment 16 (Pg 26)
The registrant stated that "Land-values and potential land
use are not adversely affected by concerns of build-up of
residues or permanent land contamination from toxic residues..."
Agency Response
The registrant has presented no data to substantiate the
above claim. Indeed, the Agency doubts such valid data exists.
The registrant should present such data, if available.
-------
CHAPTER III
BENEFITS SUMMARY
A. INTRODUCTION
Aldicarb is a systemic pesticide formulated as a granular
and used for control of a variety of insects, mites, and
nematodes. Major sites of aldicarb usage include: citrus,
cotton, potatoes, peanuts, and soybeans. Together these sites
utilize about 4.8-5.3 million pounds active ingredient (a.i.) or
about 92 percent of annual aldicarb usage. The remaining eight
percent of aldicarb is used on sugar beets, tobacco, ornamentals,
sweet potatoes, dry beans, pecans, sugarcane, seed alfalfa and
grain sorghum (see Table III-l). In total, about 5.2-5.7 million
pounds a.i. of aldicarb are used on approximately 4.1-5.4 million
acres annually.
The information used to evaluate the benefits of aldicarb
was derived from several sources. These sources include: public
comments in response to PD 1, the U.S. Department of Agriculture,
the registrant, state extension personnel, published state pest
control recommendations, scientific literature from the National
Agricultural Library, analyses prepared by the Agency staff.
Cooperative Agreements between the Agency and the University of
Illinois and the University of Georgia, and an Agency contractor,
Development Planning and Research Associates. Comments received
in response to the PD 1 will not be addressed specifically, but
will be incorporated as appropriate thoughout this chapter.
The general approach of this analysis was to evaluate the
possible economic impacts assuming that the registration for
aldicarb is cancelled, causing users to switch to alternative
pest control technology. The most probable alternatives to
aldicarb were chosen on the bases of cost, efficacy, market
availability and the suggested uses by States. Chemical alter-
natives were determined from a listing of registered pesticides,
without regard to their current Agency status. Future Agency
action could change the availability and use of alternatives.
This analysis does not anticipate or speculate on all combin-
ations of possible effects due to specific regulatory actions on
other chemicals.
Economic impacts on society as well as for users and con-
sumers were based on projected changes in production costs, crop
yield reductions and possible grower shifts to other enterprises.
Impacts on users were considered on a per-unit and per-estab-
lishment basis as well as at the county (for some uses), state,
regional, and national levels. Grower level impacts were
utilized for projections at commodity market levels. Commodity
market impacts were used to estimate the distribution of impacts
among consumers, users, and non-users.
-------
TABLE III-l
SUMMARY OP ALDICARB BENEFITS BY SITE
Producer /Grower
Site/State
Cotton
Potatoes
Citrus3/
Peanuts
Soybeans
Sugar beets
Pecans
Tobacco
Sweet
Potatoes
Ornamental
Seed
Alfalfa
Grain
Sorghum
Dry beans
Sugarcane
Total
a/ First
Lbs.A.I.
x 1
1,400
1,200-1,500
1,200
800
187-375
180-200
95
58
43-60
30-50
9
< 7
3
negligible
usage
5,212-5,757
year impact
Annual Usaqe
Acres
Treated
nnn _____
2,400-3,300
485-607
229
650
250-500
60-85
24
25
10-14
unknown
3-4
< 5
3
negligible
4,144-5,446
following fully
- Assumes Brazilian imports offset
% Crop
Treated
23-32
37-47
18
42
< 1
6-8
3
7
25-35
unknown
< 1
< 1
< 1
negl.
Availability
of
Alternatives
several
several
several
several
several
several
some
several
several
several
several
several
several
several
Impacts
Increased Change in
Production Value of
Costs
20-29
11-15
4.5
17-33
minor
minor
.48
.1-.6
1.3-2.7
higher
slightly
lower
minor
slightly
higher
none
54.38-85.
effective
cancellation.
U.S. orange production
losses
Production
none
none
-50
none
minor
none
none
none
possible
decrease
decrease
decrease
possible
decrease
none
none
none
28 <-50
(by 80%).
Total Revenue
Loss (Gain)
20-29
11-15
54.5
17-33
mihor
minor
.48
.1-.6
1.3-2.7
moderate
yield loss
likely to
offset lower
production
costs
negliglible
none
none
104.38-135.28
Consumer
Impacts
minor
minor
13.5
none
minor
n.a. i .
n.a. i .
none
n.a. i .
b/
n.a. i.
none
none
none
13.5
Loss to
Society
minor
minor
n. e.
minor
minor
n.a. i.
negl.
none
n.a. i .
minor
n.a. i .
n.a. i .
none
none
b/ Possible short supplies of some items.
n.e. = not estimated
n.a.i. = no appreciable impact
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III-3
In preparing the benefit analysis, the Agency reviewed all
rebuttal comments for information needed to perform an economic
impact analysis of aldicarb on a site/pest basis. These data
(e.g., quantity used, units treated, comparative efficacy, use
of the next best alternative, etc.), were often not reported,
were reported in an unusable manner, or were claimed as confi-
dential. In an attempt to clarify rebuttal comments and to
derive the fundamental data needed to quantify the benefits from
aldicarb use, contacts were made with individuals in the pest-
icide industry, the USDA Cooperative Extension Services, state
departments of agricultural, county agricultural commissioners,
and other sources.
B. ANALYSIS OF INDIVIDUAL COMMODITIES AND ALTERNATIVES
1. COTTON
Aldicarb is used as an insecticide, acaricide and nematicide
either at-planting or after emergence of cotton seedlings. Major
target pests include thrips, aphids, nematodes, plant bugs,
cotton leaf perforators, mites, flea hoppers, leafhoppers, white-
flies and boll weevils. In 1984, an estimated 2.4 to 3.3 million
acres of cotton (about 23 to 32 percent of U.S. acreage) were
treated with about 1.4 million pounds a.i. of aldicarb.
If the aldicarb registration is cancelled on cotton, current
users would employ a variety of pesticides and pest management
strategies to control insects, diseases, and nematodes. Depend-
ing on target pest, alternatives include disulfoton, phorate,
carbofuran, dimethoate, carbaryl, oxamyl, dicrotophos, metha-
midophos, and chlorpyrifos. For insect and nematode control, use
of alternatives could increase production costs by about $l.48/A
(a reduction of 1.5-5.2 percent of net cash receipts). Cotton
producers in the southeastern and southwestern states where
aldicarb is used for insect and nematode control would be most
severely affected. Because net cash receipts per acre are modest
for cotton producers in these areas, the estimated $15.75
increase in production costs could reduce net cash receipts by
about 50 percent (southeast) to 56 percent (southwest). The
aggregate annual cost increase would approach $20 to $29 million,
which is less than 1 percent of the value of cotton produced in
the United States.
The impact on cotton producers would be widespread with
large variation in regional impacts. Aldicarb is used exten-
sively in the Southeast (Alabama, Georgia, North Carolina and
South Carolina), Louisiana and Mississippi. Texas has the
largest acreage treated and, because nematodes are the major
pest, Texas cotton producers would incur the highest cost
increases (about $19 per acre compared to $9 per acre for other
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III-4
areas) as well as nearly half of the economic impact of
cancelling aldicarb usage on cotton.
The cancellation of aldicarb registrations would potentially
have a significant impact on cotton growers in Texas and the
southeastern States. Consumers are not expected to be signifi-
cantly affected because overall supplies of cotton are not
expected to decline due to regulatory action.
2. POTATOES
Aldicarb is used to control Colorado potato beetles, aphids,
nematodes and leafhoppers either at-planting or after emergence
of potato seedlings. An estimated 485,000-607,000 acres of
potatoes (about 37-47 percent of the U.S. potato acreage) were
treated with an estimated 1.2-1.5 million pounds a.i. of aldi-
carb in 1984.
If the aldicarb registration is cancelled on potatoes,
aldicarb users will utilize alternative pest management
strategies that are significantly more costly. Where insects are
the target pest, potato growers will utilize combinations of
disulfoton, fenvalerate, methomyl, permethrin, methamidophos,
azinphos-methyl, and endosulfan. Usage of these alternatives
could increase grower insect control costs from $l-$26/A «4
percent increase in variable production costs).
Few alternatives are available for nematode control. Etho-
prop and oxamyl are the only non-fumigant materials available
but both are more expensive than aldicarb. Fumigants that could
be used include 1,3-dichloropropene and metam-sodium, but both
are more expensive. Cost impacts for use of alternatives range
from $58 to $94 per acre where both insects and nematodes are
problem pests. States most affected would be Idaho, Wisconsin,
Michigan and Florida where control cost increases could exceed 20
percent of current variable expenses.
Based on 1984 crop data, some states have reported yield
increases using metam-sodium instead of aldicarb. These
increased yields will partially offset the higher costs where
metam-sodium is used in lieu of aldicarb. While current users of
aldicarb will be impacted if aldicarb is not available, effects
to consumers are not expected to be serious. Potato supplies
should remain adequate if aldicarb is not available.
3. CITRUS
Aldicarb is registered for use on citrus to control a
variety of insects, mites and nematodes. The Agency's analysis
focussed on Florida oranges and Texas grapefruit. An estimated
1.2 million pounds a.i. of aldicarb were used on a total of
228,500 acres in 1982. Approximately 25 percent of all Florida
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III-5
and about 15 percent of all Texas citrus acreage is treated with
aldicarb in normal years. California and Arizona report
negligible aldicarb usage on citrus.
If the aldicarb registration is cancelled on citrus, users
will be forced to utilize available alternatives. In Florida for
nematode control, fenamiphos is the most likely alternative while
oxamyl is the most likely alternative in Texas. Several pest-
icides are available and recommended for control of insects and
mites in both states. For insect control, major alternatives
include dimethoate, ethion, oil and azinphos-methyl. For mite
control, the most widely accepted and effective alternatives
include dicofol, ethion, oil, propargite, fenbutatinoxide and
sulfur.
If the aldicarb registration on citrus is cancelled, Florida
and Texas producers could experience increased production costs
averaging approximately S30.00/A. Aggregate annual production
costs would increase by an average of $4.4 million in Florida and
$70 thousand in Texas. Alternatives appear to be somewhat less
effective than aldicarb. Florida growers currently using
aldicarb could incur yield losses of approximately 15 percent
without aldicarb, while Texas yields could decrease by about 7
percent. The average annual yield reduction statewide would
range from 2.2-7.1 percent in Florida, depending upon efficacy
and usage of aldicarb and alternatives. Texas could experience
average annual statewide yield losses ranging from 0.7-2.3
percent.
Yield reductions to Florida processing oranges producers
would normally result in increased prices because of the rel-
atively inelastic demand for frozen concentrate orange juice
(FCOJ) at the retail level. The final price at the grower level,
however, depends to a large extent upon frozen concentrate
imports, primarily from Brazil. Assuming Brazialian imports
cover an estimated 80 percent of any reduced Florida production,
on-tree price received per box of oranges for processing is
estimated to increase by approximately 3.4 percent, without the
availability of aldicarb. Corresponding yield reductions,
however, will result in an estimated 12 percent overall reduction
in gross revenue per acre. The 12 percent reduction in gross
revenue per acre combined with an average four percent increase
in production costs is estimated to result in average decreased
net returns of $335/acre for the 1988/1989 season. This amounts
to about a 20 percent decline in total net revenue per acre, for
current aldicarb users. Aggregate net returns are projected to
decline by about $54.6 million for the 1988/1989 season. This
figure represents approximately six percent of the average annual
value of all Florida citrus production over the last eight years
and 13 percent of the 1985/1986 total on-tree value of all
Florida oranges produced for processing.
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III-6
Texas fresh grapefruit growers are also expected to be some-
what worse off without the availability of aldicarb. The on-tree
price per box could decline by about 11 percent (due mainly to
quality losses), with corresponding yield losses of 6.5 percent.
These two factors, combined, result in an average annual gross
revenue decrease of $206 per acre, or nearly 17 percent. Accum-
ulated returns for the state show an average annual decrease of
$583,000, without the availability of aldicarb. Fresh grapefruit
imports are not expected to have any significant impact on
returns to Texas growers.
The consumer can be expected to face higher prices for both
orange and grapefruit products if aldicarb is cancelled. The
retail price for fresh grapefruit is expected to increase by
about 7.1 percent while the price for FCOJ would increase by
approximately 1.4 percent. Such price changes at the retail
level are expected to result in an estimated 0.4 percent increase
in consumer orange expenditures and a 1.3 percent decrease in
consumer grapefruit expenditures. This converts to an estimated
increase of $23.7 million nationwide for orange products and a
$10.2 million nationwide consumer expenditure decrease for
grapefruit products. Total nationwide consumer expenditures are
expected to increase, therefore, by approximately $13.5 million.
This figure represents less than 1 percent of the total value of
domestic citrus consumption in the United States each year.
4. PEANUTS
Aldicarb is used by peanut growers in all major producing
regions for both insect and nematode control. Georgia, Alabama,
North Carolina, Texas, Virginia, Florida and Oklahoma comprised
over 98 percent of the 1984 peanut production. In 1984, an
estimated 800,000 pounds a.i. of aldicarb were used to treat
approximately 650,000 acres (42 percent of U.S. acres) of
peanuts. The use of aldicarb rose in 1982 sharply due primarily
to cancellation of ethylene dibromide, a major soil fumigant/
nematicide for peanuts.
If aldicarb is not available for use, peanut producers would
most likely employ other chemicals for nematode and insect
control. The most likely alternatives include fenamiphos, carbo-
furan, ethoprop, and 1,3-dichloropropene. These alternatives are
generally more costly and somewhat less effective than aldicarb.
If the aldicarb registration on peanuts is cancelled,
affected producers could experience lower income because of
higher production costs and lower yields. At a minimum, affected
producers could receive a $30 to $45 per acre reduction in
income which is about 3.8 to 5.7 percent of the per acre value
of peanuts. In the.aggregate, impacts on U.S. peanut producers
could range from $17 million to $33 million annually.
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If the aldicarb registration is cancelled for peanuts,
normal market adjustments in acreage and prices are not expected
because the government sets production quotas and supports price
and therefore adjustment in prices due to changes in production
(quantity) do not fully occur. Affected growers will experience
lower profitability unless government price supports are modi-
fied. If price supports are raised to account for lost revenue,
unaffected producers would receive windfall profits and consumers
of whole peanuts and peanut products would pay slightly higher
prices. Overall, the impact will moderately affect aldicarb
users but is not expected to have serious effects at either the
industry or retail/consumer levels.
5. SOYBEANS
Aldicarb is registered for control of nematodes and Mexican
bean beetles on soybeans. Approximately 250,000 - 500,000 acres
of soybeans were treated with about 187,500 - 375,000 Ibs. a.i.
during 1985. Most usage occurs in the southeastern States where
nematodes are a problem pest. North Carolina and South Carolina
are believed to be important states for aldicarb usage on
soybeans. The remaining usage is divided between Georgia,
Louisiana, Tennessee, Arkansas, Missouri, Illinois, Virginia and
Alabama. In total, less than 1 percent of the nearly 63 million
acres of soybeans harvested were treated with aldicarb in 1985.
Several alternative pesticides are registered and readily
available for control of Mexican bean beetle and nematodes on
soybeans. Alternative nematicides include: fenamiphos, fensul-
fothion and 1,3-dichloropropene. Several insecticides are
registered for control of Mexican been beetle on soybeans. These
include: azinphos-methyl, carbaryl, dimethoate, malathion,
methomyl and methyl parathion.
If the aldicarb registration for soybeans is cancelled,
producers presently using aldicarb for nematode control would be
more likely impacted than users of aldicarb for insect control.
Usage of aldicarb on insect pests of soybeans is a very minor
market. In most cases, current aldicarb users could substitute
a granular material with nominal cost impacts (approximately
$1.00/A) or more extensive use of resistant varieties and crop
rotations. Fumigant alternatives for nematode control are
prohibitively expensive. Some reduction in soybean yield is
possible for aldicarb users with very heavy nematode infest-
ations. Producers in North Carolina and South Carolina could be
most affected if growers abandon nematode control or if alter-
natives prove less cost effective than aldicarb. In situations
where aldicarb is used at high rates, the treatments may not be
cost effective (i.e., treatment cost exceeds the value of
additional yield). Some growth stimulation from aldicarb may
occur but the amount appears to vary with test conditions.
Additional yield does not always exceed the cost of treatment.
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Since soybean yields could fall somewhat for those farms
with more severe nematode infestations that currently use
aldicarb, there could be a slight decrease (less than 1 percent)
in total regional soybean production. This could lead to
slightly higher soybean prices, gains for farmers (both users and
non-users of aldicarb) and higher prices to consumers. Because a
relatively small acreage of soybeans would be affected (less than
1 percent of U.S. acreage treated) and because per acre losses
are severe only to a localized area, no significant impacts are
expected at the national level.
6. SUGAR BEETS
Aldicarb is registered for insect control primarily of the
sugar beet root maggot, along with aphids, leafhoppers and leaf-
miners. Aldicarb also controls the sugar beet cyst and sugar
beet root knot nematodes. There are numerous alternatives
available for insect control, including carbofuran, chlorpyrifos,
diazinon, fonofos, phorate and terbufos. Available alternatives
for nematode control are more limited, including 1,3-dichloro-
propene, methyl isothiocyanate and sodium methyldithiocarbamate.
About 180,000-200,000 pounds a.i. of aldicarb are applied
annually on about 60,000 to 85,000 acres of sugar beets through-
out the north central and western regions of the U.S. This
constitutes roughly 6 percent to 8 percent of total U.S. sugar
beet acreage. About 80 percent of the aldicarb usage is for
insect control, while the remaining 20 percent is used to con-
trol nematodes. Without the use of aldicarb, sugar beet pro-
ducers experiencing insect problems will most likely use either
chlorpyrifos or terbufos. Crops with nematode infestations will
be treated with 1,3-dichloropropene, the primary alternative.
The use of alternative insecticides, particularly chlor-
pyrifos and terbufos, can potentially lower the treatment costs
of producing sugar beets by approximately $12-$21/A (3 percent
of production costs). Assuming no significant yield impacts
from the use of alternative chemicals, a loss of aldicarb for
insect control may reduce the total cost of sugar beet production
by approximately $400,000-$!,200,000 which represents less than
1 percent change in net farm income. By contrast, the use of
the primary alternative nematicide, 1,3-dichloropropene can po-
tentially raise treatment costs by $41.58/A (9 percent/A increase
in production costs). This may result in an increase in total
production costs of $415,000-$580,000 for sugar beet producers
with nematode infestations.
Since there were no data available to determine the relative
efficacy of aldicarb and 1,3-dichlropropene, it was not possible
to evaluate yield effects. However, data suggest that the use
of 1,3-dichlorpropene could increase sugar beet yields over the
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average yield achieved when treated with aldicarb. If 1,3-
dichloropropene use results in higher yields, then the increased
treatment costs could be partially offset by higher production
and revenues.
Overall, the cancellation of this aldicarb registration is
not expected to produce any significant impacts on sugar beet
producers. The change in production costs which may occur from
the cancellation of the insecticidal use could offset potential
increases in production costs if the nematicidal use is
cancelled. Overall production of sugar beets is not expected to
be impacted by a loss of aldicarb. Since the cancellation of
this use is not expected to significantly change the supply of
sugar beets, negligible impacts are expected for the sugar market
and the consumer.
7. PECANS
Aldicarb is registered on pecans for control of aphids and
mites as well as for suppression of phylloxeras. Alternatives
registered to control aphids (the major pest) and mites on pecans
include: phosalone, carbophenothion, fenvalerate, diazinon,
methidathion, dimethoate, ethion, dicofol and fenbutatin-oxide.
Approximately 24,100 acres, (3 percent of the 710,700 acres of
managed pecans) were treated with approximately 95,000 pounds of
aldicarb in 1984. Approximately 68 percent of the acreage
treated is in the southeastern United States; Georgia pecan
growers treated approximately 12,000 acres. Other leading
aldicarb using states include Alabama, Texas, and New Mexico.
The aggregate user impact from a possible cancellation of
the aldicarb registration on pecans could total approximately
$481,000 annually. The impacts would be most severe in Georgia
where aphid problems may lead to an abandonment of some acreage
unless new methods of aphid control are developed. Losses in
Georgia could total approximately $290,000 annually with nearly
50 percent of this loss concentrated in two counties.
The overall market impacts of cancelling the aldicarb reg-
istration on pecans are not expected to be significant. Because
such a small proportion of the U.S. pecan acreage is treated, the
annual loss in production would not significantly affect growers'
prices.
Likewise, consumers would not be seriously effected since
the possible increase in consumer prices will be very small.
8. TOBACCO
Aldicarb is currently registered under FIFRA section 24(c)
in North Carolina and Virginia for field control of aphids, flea
beetles and root knot nematodes on tobacco. Estimated annual
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usage is approximately 58,000 pounds a.i. on 25,000 acres (about
7 percent of flue-cured acreage). North Carolina alone accounts
for nearly three-fourths of the total aldicarb usage on tobacco.
Although growers in recent years have apparently experienced
diminished aphid control with disulfoton, there are a variety of
alternatives available. Acephate, applied foliarly for simul-
taneous control of aphids and worms (hornworm, budworm) is by far
the leading aphicide on flue-cured tobacco. Similarly, ethoprop
used either singularly or in combination with insecticides is
the leading nematicide. Several other nematicides considered
equally efficacious are available and extensively used.
Under certain pest situations, especially a simultaneous
infestation of root knot nematodes and aphids, aldicarb is less
costly (from $8.03 to $41.13 per acre) than its alternatives.
Under other situations, especially a simultaneous infestation of
aphids and worms (hornworm and budworm), various alternatives
are less costly than aldicarb. Use of these chemicals would
cost from $5.32 to $26.74 less per acre than use of aldicarb.
In the event of cancellation of the aldicarb registration
on tobacco, current users would sustain increased production
costs (but no yield-related losses, since equally efficacious
alternatives are available) ranging up to $41 per acre, depending
on whether aldicarb is used as an aphicide or a nematicide. This
increase would represent a change ranging up to 2.4 percent of
variable costs. The average variable cost is about $1,700 per
acre. On a typical farm of 35 acres, this would amount up to
about $1,435. In the aggregate, tobacco users could sustain
annual increases ranging from $0.1 - 0.7 million as a result of
using alternative pesticides.
Given foreseeable supply-demand conditions for flue-cured
tobacco, it is unlikely that the affected producers would be
able to pass their increased costs on either to processors or
consumers of finished tobacco products. Since, for most
producers, tobacco is substantially more profitable than other
crops commonly grown in North Carolina and Virginia, the impacted
growers would absorb these added costs by realizing lower "quota
profits," which are made possible by the existing tobacco price
support program. Since affected producers earn more on tobacco
than on other crops (as verified by existence of quota rents),
they have no incentive to shift acreage. Hence short term and
long term impacts are identical.
9. SWEET POTATOES
Aldicarb is used for nematode control on about 11,900 acres
(0.3 percent of U.S. acres) of sweet potatoes annually. About
30,000-40,000 pounds a.i. aldicarb are used annually to treat
sweet potatoes. North Carolina, being the biggest sweet potato
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producing state with 35 to 40 percent of U.S. sweet potato acre-
age and production, is the major user of aldicarb.
If the aldicarb registration on sweet potatoes is cancelled,
producers will employ alternatives such as 1,3-dichloropropene,
fensulfothion, ethoprop and oxamyl. Alternatives such as metam-
sodium, methyl-isothiocyanate and 1,3-dichloropropene could also
be used but significant usage is not expected due to their
expense. While no yield impacts are expected from substituting
1,3-dichloropropene, lower yields are possible where fensul-
fothion, ethoprop and oxamyl replace aldicarb. While the extent .
of these impacts could not be estimated with available data,
yield changes are not expected to be severe.
Sweet potato production costs could increase by about $1.3
to $2.7 million annually, or about 1-2 percent of the value of
U.S. sweet potatoes, if the aldicarb registration is cancelled.
Since 1,3-dichloropropene is as effective as aldicarb and is
expected to be used on about 50-80 percent of the acreage
currently treated with aldicarb, no serious production losses
are anticipated. Supplies of sweet potatoes should be adequate
to meet consumer demand and no significant retail impacts are
expected.
10. ORNAMENTALS
Aldicarb is registered for use as an insecticide on several
commercial greenhouse floriculture crops as well as field grown
and nursery plantings. Use of aldicarb on field grown and
nursery plantings has declined significantly in recent years and
currently, very little aldicarb is applied to these crops.
Commercial greenhouse usage has also declined to some extent but
aldicarb remains an important pest control in the production of
greenhouse floriculture crops. An estimated 30,000-50,000
pounds a.i. of aldicarb were applied to greenhouse floriculture
crops in 1984. Growers primarily apply aldicarb to control
aphids, thrips, whiteflies, leafminers and spider mites on
several flowering plants, particularly chrysanthemums, poin-
settias, lilies, carnations, snapdragons and gerbera. Foliage
plants (e.g., ferns, ivy) are also frequently treated with
aldicarb at rates ranging up to 10 ibs. a.i./A.
According to state recommendations, several pesticides are
recommended for one or all of the pests previously listed. The
most frequently recommended alternative pesticides are oxy-
demeton-methyl, diazinon, malathion, dimethoate, acephate and
chlorpyrifos. Growers and state extension specialists indicate
that in addition to these, other important controls include
bendiocarb, dicofol, endosulfan, fluvalinate, oxamyl, and res-
met hr in. The alternatives are not completely interchangeable in
terms of host plant tolerance or efficacy against various pests.
Few of the alternatives are as effective as aldicarb on the same
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broad spectrum of plants and pests; several alternatives have
become ineffective due to pest resistance.
Estimating the economic impacts of cancelling aldicarb for
ornamental/floriculture crops is difficult because of the
complexity of the floriculture industry. Floriculture is unlike
other areas of agriculture in that the plants are priced
according to the aesthetic value. While minor insect damage may
not affect the yield or value of an agricultural crop, it signif-
icantly reduces the value of potted plants and often makes them
unmarketable.
Cancellation of the aldicarb registration on ornamentals
could potentially have a significant impact on growers of several
commercially grown floricultural crops including chrysanthemums,
poinsettias, foliage plants and lilies. In the event of cancel-
lation, current users of aldicarb will use one or a combination
of several available alternatives. The extent of the impact will
mainly be determined by the severity of pest infestations without
aldicarb and the effectiveness of the alternative chemicals.
Generally the substitutions for aldicarb and its alternatives are
not made on a one-for-one basis since few of the .alternatives are
as effective on the same broad spectrum of plants and pests.
In addition, aldicarb and the alternatives differ in their
mode of activity as well as timing and mode of application.
Aldicarb is a granular systemic insecticide incorporated into
the soil of individual plants or as a broadcast treatment. Most
of the alternative compounds are contact insecticides and are
typically applied as foliar sprays, fogs or smoke. These types
of applications generally require frequent reapplication.
Substituting the alternatives for aldicarb may have some
effect on growers' production costs, i.e., additional treatment
costs resulting from frequent applications of the alternatives.
However, growers are likely to be less concerned with slight
fluctuations in production costs and more concerned with how
effectively they can control insect infestations and prevent
further development of pesticide resistance.
If the alternatives used in the absence of aldicarb do not
effectively control thrips, leafminers, whiteflies, etc., growers
could incur significant economic losses in the form of decreased
sales and revenues. Since commercially grown floricultural
crops are highly valued, growers could incur significant revenue
losses even if only a small portion of their crop is
unmarketable.
A significant decline in the supply of clean, high quality
plants may result in increased prices to retailers and consumers.
How much prices will increase depends on current market situa-
tions and the perceived value of the product. Because of com-
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petition from imported flowers and the substitutability of other
gift type items (e.g., silk flowers and candy), retail prices
will likely be less responsive to a decrease in supply.
11. SEED ALFALFA
Aldicarb is registered for use on seed alfalfa only in Cali-
fornia with an intrastate product for control of lygus bugs and
aphids. The alternatives to aldicarb are oxydemeton-methyl,
disulfoton and trichlorfon. While aldicarb and its alternatives
provide similar insect control, aldicarb offers longer residuals,
simultaneous control of nematodes and insects, and a lower
toxicity to pollinating bees.
Aldicarb is used on less than 5 percent of the California
seed alfalfa or about 1 percent of the total U.S. crop. Approx-
imately 9,000 Ibs a.i. of aldicarb are used annually on an
average 3,000-4,000 acres of seed alfalfa, primarily in four
central California counties: Fresno, Kings, Imperial and Kern.
If the aldicarb registration on seed alfalfa is cancelled,
production costs could decline by $115,000-$200,000 annually
(less than 1 percent of the value of California seed alfalfa
production) since the alternatives are less expensive. The use
of aldicarb provides other benefits that the alternatives do not
and, as a result, yield effects may occur which more than offset
the decrease in production costs from the use of the alterna-
tives. Given the low magnitude of aldicarb usage as well as the
possibility of benefits offsetting the lower treatment costs of
the alternatives, no serious impacts on the producers, consumers,
or the market are expected.
12. GRAIN SORGHUM
Aldicarb is used on grain sorghum primarily to control
chinch bugs and sorghum greenbugs. Although very little data
are available regarding the usage of aldicarb on grain sorghum,
less than 5,000 acres of grain sorghum, representing less than 1
percent of the total U.S. acreage, are treated annually. At the
recommended rates of 1.3 Ibs a.i./A, a maximum of 6,500 Ibs a.i.
aldicarb would be used annually. If the aldicarb registration
for use on grain sorghum is cancelled, growers will employ
alternatives including carbofuran, parathion, mevinphos, metho-
myl, disulfoton and phorate. These alternatives are readily
available, in current use, and for certain pests, more effective
than aldicarb. In addition, alternatives are similarly priced
and in some cases, less expensive based on chemical costs alone.
Kansas is the only major sorghum producing state recommending
aldicarb, and lists it only for suppression of chinch bug and
sorghum greenbug.
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Because effective alternatives are available at similar or
lower costs per acre, and very small amounts of aldicarb are
used, no appreciable impacts on users, consumers or society are
anticipated if aldicarb use is cancelled on grain sorghum.
13. DRY BEANS
Less than 3,000 acres of dry beans (<1 percent of U.S.
acres) are estimated to be treated with aldicarb. At standard
treatment rates, about 3,000 Ibs a.i. of aldicarb are used on dry
beans. Aldicarb is registered for use to control insects on dry
beans. However, only Michigan and California indicated any sig-
nificant usage of aldicarb on dry beans. Alternatives such as
disulfoton and phorate are available, equally effective, and less
expensive than aldicarb.
Cancellation of the aldicarb registration for use on dry
beans is not viewed as a serious problem for producers of this
crop. Cancellation of the aldicarb registration would have no
measurable economic impacts on users or consumers.
14. SUGARCANE
The aldicarb registration for use on sugarcane is under
section 24(c) of TIFRA in Louisiana for nematode control.
Currently, estimates suggest that negligible amounts of aldicarb
or any other nematicide are used on Louisiana sugarcane. Nema-
tode infestation usually occurs in light sandy soils. Louisiana
sugarcane is grown in a heavier clay soil that is not a
conducive environment for nematodes. Therefore, nematode
infestations are not a severe problem in Louisiana.
Since negligible amounts of aldicarb are used on sugarcane,
a cancellation of the aldicarb registration would not have a
significant economic impact on users, consumers or the market.
C. CONCLUSIONS
After a thorough review of comments and subsequent attempts
to obtain specific data, the Agency determined that data suffi-
ciently detailed to prepare a highly quantitative analysis of
aldicarb benefits on a site/pest basis were limited. Data on
the minor use sites were generally incomplete or unavailable. As
a result, the analyses presented herein often rely on the judge-
ment and estimates provided by experts knowledgeable about
various cropping practices and aldicarb use. Field tests compar-
ing efficacy and performance of aldicarb and alternatives were
unavailable for many site and pest combinations. Registrant and
user data for comparative performance are solicited for all use
sites.
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If aldicarb registrations are cancelled, producer/grower
control costs could increase by an estimated $54 to $85 million
annually. For potato, cotton and peanut producers/growers, the
increased costs could be significant. Significant user losses
and consumer expenditure impacts are expected as a result of
lower citrus production.
In addition to these tangible benefits, a number of existing
benefits are difficult to quantify. Aldicarb simultaneously
controls nematodes, mites and insects, especially if applied at
the higher nematicidal application rates. Many alternatives
cannot provide simultaneous control of these three pests without
being used in combination with other pesticides. The systemic
action o.f aldicarb provides residual pesticide effects. Many
alternatives, by contrast, are applied as foliar sprays and
provide a shorter duration of pest control. Alternatives must
be applied two, three, or more times to provide equivalent pest
control. Aldicarb is applied as a soil incorporated granule,
while most of the probable alternatives are applied as sprays.
Alternatives are, therefore, more subject to off-target drift
and attendant mixer/loader/applicator exposure.
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CHAPTER IV
A. INTRODUCTION
FIFRA requires the Agency to weigh the risks against the
benefits for the pesticide use of concern to determine whether
continued registration would cause unreasonable adverse effects
on man and the environment. In Chapter II the Agency described
the risks posed by exposure to aldicarb through ground water
contamination and the diet. In Chapter III the Agency identified
the major alternative pesticides for the uses for which aldicarb
is registered and described the benefits from aldicarb use.
To determine whether continued registration of aldicarb is
appropriate, this section reviews the Agency's conclusions con-
cerning the risks and benefits of aldicarb and its alternatives.
This section also identifies the regulatory options available to
the Agency to reduce the risks from aldicarb use. Each option
has been evaluated for its impact on the risks and benefits of
the registered uses of aldicarb and the most appropriate regu-
latory options have been proposed. The human risks and potential
for ground water contamination by alternative pesticides have
also been summarized.
B. RISK SUMMARY
1. TOXICITY SUMMARY
Aldicarb has a high acute toxicity via the oral, inhalation
and dermal routes of exposure and has been assigned to toxicity
category I, based on all three routes of exposure. It is a
potent cholinesterase inhibitor with an acute LD50 in rats of 0.9
mg/kg. In a study using human test subjects, the Lowest
Observed Effect Level (LOEL) for clinical signs (e.g., gastro-
intestinal disturbances, unconsciousness, blurred vision,
excessive salivation, seizures, and disorientation) is 0.1 mg/kg
and the No Observed Effect Level (NOEL) for clinical signs is
0.05 mg/kg. There was no NOEL for cholinesterase inhibition in
the registrant's human study; the lowest dose of aldicarb tested,
0.025 mg/kg, caused a 35 to 54 percent decrease in cholinesterase
levels. The National Academy of Sciences used these data to
extrapolate a NOEL of 0.01 mg/kg for cholinesterase inhibition.
No known reports of cholinesterase inhibition and/or
clinical signs have been reported as a result of legal
application of aldicarb. A number of reports of accidental
exposures following misuse of aldicarb indicate that cholinergic
signs, even severe cholinergic signs, may occur at doses
considerably below 0.1 mg/kg, the LOEL for clinical signs in the
human study described above. These effects are reported to occur
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at doses as low as 0.0026 mg/kg. These data are anecdotal,
however, and it is difficult to precisely quantify exposures for
these accident data. The data may indicate a broad range of
sensitivity to aldicarb's acute effects. In light of all
information, the Agency believes that the NOELs for
cholinesterase inhibition and clinical signs associated with such
inhibition are close to 0.01 mg/kg and at 0.001 mg/kg it is
unlikely that many individuals will show clinical signs or have
depressed cholinesterase activity.
The chronic toxicity data base for aldicarb is complete.
Aldicarb is negative for delayed neurotoxicity, oncogenicity and
reproductive effects. It is also negative for teratogenicity.
The one effect of concern is acute cholinesterase inhibition.
There is a 10 ppb Health Advisory level for aldicarb residues
that contaminate drinking water, based on the cholinesterase
inhibition seen during chronic exposure. The Health Advisory is
set by the Agency's Office of Drinking Water, is based on
consideration of risks, and reflects that Office's judgement that
exposures to residues of aldicarb in drinking water above the
Health Advisory would not protect human health adequately.
2. RISKS FROM TREATED COMMODITIES
The Agency has estimated dietary exposure to aldicarb,
resulting from a single exposure, from legally treated potatoes
and citrus using the upper 5 percent residues. The Agency used
data submitted by the registrant in support of tolerances and FDA
market basket survey data. The exposure estimates were then
compared against aldicarb's cholinesterase inhibition
characteristics to determine the margins of safety for these two
crops for different sectors of the population. Infants and
children consuming the treated commodity would be at the highest
risk of acute aldicarb toxicity from the consumption of citrus
and potato products. As many as 55 percent of those consuming
the upper 5 percent residue levels of aldicarb in these food
commodities would have less than a tenfold margin-of-safety for
cholinesterase inhibition.
The Agency has encouraged pesticide registrants to conduct
monitoring studies to give a more accurate representation of the
level of pesticide residues to which the public is exposed. The
registrant has recently submitted the results of a National Food
Survey which monitored residues of aldicarb in the market place.
These data are currently under review and, along with the
tolerance data and the FDA market basket survey data, will be
used in the final dietary risk assessment.
3. RISKS FROM CONTAMINATED DRINKING HATER
The Agency has estimated the percent of the population
consuming various quantities of drinking water in their diet.
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IV-3
The Agency has also calculated a dose of aldicarb and provided a
Margin of Safety estimate for these populations assuming various
levels of contamination. The focus of the analysis was on the
population of greatest risk, infants, because they consume most
of their diet as formula and fruit juice which are both
frequently prepared using tap water. The Agency calculated that
when drinking water containing aldicarb at 10 ppb, as many as 13
percent of consuming infants could be exposed to a dose of 0.001
mg/kg or greater of aldicarb. The corresponding Margin of
Safety for cholinesterase inhibition would then be 10 or less,
based on the NOEL estimated by the National Academy of Sciences.
Clearly not all ground water in the nation contains aldicarb, nor
where contamination is found will it always be above 10 ppb.
Because aldicarb can cause cholinesterase inhibition by a
single acute exposure, and because it is reasonable to assume
that an individual would not consume all of the water in his diet
at one sitting, the Agency has assumed that the daily intake of
drinking water will be composed of two separate doses. The
numbers represent the percentage of consumers who get the dose
from an acute exposure (within a six hour period).
C. BENEFITS SUMMARY
The benefits were assessed in terms of economic impacts
from use cancellation and subsequent switching to alternative
pest management practices. If aldicarb is cancelled in all
areas of the country, significant impacts are expected for
Florida oranges and Texas grapefruit ($54.5 million) and peanuts
($17-33 million). Moderate economic impacts at the national
level are expected for cotton ($20-29 million), potatoes ($11-15
million), tobacco ($0.1-0.7 million), sweet potatoes ($1.3-2.7
million) and pecans ($0.48 million). For all uses, the impacts
result primarily because alternatives are less effective and more
expensive than aldicarb.
If aldicarb is regulated on the basis of vulnerability to
ground water contamination, cancelling use would mostly affect
the southeast (citrus: $49 million, peanuts: $22 million, pecans:
$0.2 million, sweet potatoes: $0.9 million and tobacco: $0.7
million), north central (potatoes: $1.6 million and sugar beets:
$0.6 million), south central (Texas cotton: $14 million), and
the northwest (potatoes: $4 million).
D. ANALYSIS OF ALTERNATIVE PESTICIDES
Alternative pesticides are available for almost all uses of
aldicarb. This section discusses briefly the relative hazards of
these alternative pesticides to humans and wildlife as compared
to aldicarb. Table IV-1 summarizes the human toxicology hazards.
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Aldicarb is at least twice as acutely lethal to humans as
any of the listed alternatives. However, many of the alter-
natives also are acutely lethal and only differ by less than one
order of magnitude from aldicarb. These include azinphos-methyl,
disulfoton, fenamiphos, fensulfothion, phorate, oxamyl, and
terbufos. Chlorpyrifos, dimethoate, and phosalone are two
orders and acephate is three orders of magnitude less acutely
toxic than aldicarb. See Table IV-1 for the LD50s of these
alternative pesticides.
Disulfoton and fenamiphos have also been found to be terat-
ogenic and thus could pose other significant health risks. Fen-
sulfothion, l,3-D, and metam-sodium have not been tested for
teratogenicity.
In terms of oncogenicity, acephate and dicofol have been
categorized as class C oncogens (possible human oncogen), and
1,3-D is a class Bj oncogen (probable human oncogen).
A number of the major alternatives have some potential to
leach, although the leaching potential is variable. Carbofuran
is probably less a ground water threat than aldicarb; however, it
has been found in ground water in Wisconsin, New York and Mary-
land. Oxamyl also has been found in ground water. Ethoprop,
fensulfothion, fenamiphos, and metam-sodium show a moderate po-
tential to leach, based on limited data. Disulfoton has a low
potential to leach. Although 1,3-D is not believed to be a
significant threat to ground water, l,2-D, a contaminant in its
formulation, may be a ground water contaminant. A Special Review
has been initiated on 1,3-D because of its potential oncogenicity
as well as its potential to leach to ground water. Acephate, di-
methoate, and methamidophos all show moderate to high potential
to leach. Terbufos, phosalone, fenvalerate, Chlorpyrifos,
azinphos-methyl, ethion, and phorate show little, if any, poten-
tial to leach. In general, all the other alternatives can be
considered to have less potential to leach as compared to
aldicarb, except for carbofuran and oxamyl. Of these two, only
oxamyl approaches aldicarb in acute toxicity potency.
The Agency has concluded that, within the limitations of
the present analysis, some alternatives appear to be less acutely
hazardous than aldicarb, at the given application rates, to both
birds and aquatic organisms. Oxamyl (for potatoes and sweet
potatoes), ethoprop (for peanuts), fenvalerate (for pecans and
potatoes) and carbophenthion (for pecans) do not meet or exceed
the more restrictive endangered species risk criteria for birds.
It must be noted, though, that all major alternatives meet or
exceed avian and/or aquatic risk criteria for non-endangered and
endangered species. Carbofuran is currently under Special Review
because of its acute toxicity to birds.
-------
TABLE IV-1
TOXICOLOGY OF ALDICARB AND ITS ALTERNATIVES
Aldicarb
Acephate
Azinphos-methyl
Carbofuran
Chlorpyrifos
Carbophenothion
1 ,3-dichloropropene (1,3-D)
Demeton
Dicofol
Dicrotoohos
Dimethoate
Disulfoton
Endosulfan
Ethion
Ethoproo
Fenamipnos
Fensulfothion
Fenvalerate
Met am- Sodium
Methamidoohos
Met homy 1
Monocrotophos
Oxamvl
Phorate
Phosalone
Terbufos
LD50
mq/kq
0.9
900
4.5
11.0
97-276
6.8-36.9
250-500
50
640
15-22
215
2-12
30-110
96-208
61.5
3.0
2-10
3,200
1,700
18-21
17
8-23
3.0
2-4
120
4.5-9.2
Onco.
-
+
-
-
-
-
+
-
+
ID
-
- -
ID
-
ID
-
ID
-
ID
-
-
-
-
-
-
ID
Develop-
mental
-
-
ID
-
-
ID
ID
-
ID
ID
-
+
ID
ID
-
+
ID
-
ID
-
-
ID
-
-
-
ID
Muta.
-
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
-
ID
ID
-
ID
-
ID
-
ID
(+) » Positive
(-) » Negative
(ID)» Insufficient data
-------
IV-6
In conclusion, many of the alternatives have insufficient
data regarding toxicological testing as Table IV-1 indicates.
These data will or are currently being produced in response to
the Agency's reregistration process; data will be required on
the others in the future. Aldicarb is more acutely toxic to
humans than any of the alternatives; however, the acute toxicity
of some alternatives differ by less than one order of magnitude
from aldicarb. Additionally, aldicarb has demonstrated a
potential to leach, posing additional concern. Some of the
alternatives to aldicarb have been found to be contaminants in
ground water. On the other hand, other alternatives have been
identified as oncogens, mutagens, or teratogens, while aldicarb
has been found to be negative in these three categories.
E. PUBLIC COMMENT CONCLUSIONS
The Agency has addressed and incorporated all public com-
ments in its analysis. Few comments were received by the Agency
relative to dietary exposure to aldicarb residues in treated
commodities. These comments focussed on the improbability of
high residues. The Agency agrees with this premise and has used
actual residue data to estimate dietary risk. Additionally, the
registrant has conducted monitoring studies to determine the
level of residues of aldicarb in the market place. The Agency is
currently reviewing these data.
Few comments were received by the Agency relative to dietary
exposure to contaminated drinking water. These comments, how-
ever, focussed primarily on the appropriateness of the Health
Advisory and argued that no unreasonable adverse effects are
probable. The Agency believes that use of the Health Advisory is
appropriate for protection of the public's health and that
regulatory measures to mitigate ground water contamination below
this level are necessary to assure that the public's health is
not jeopardized.
The vast majority of comments focussed on measures to
mitigate ground water contamination. The Agency has considered
these comments in identifying the regulatory options presented in
this document.
The Agency has reviewed comments on the benefits of aldicarb
use as well as the risks and benefits associated with altern-
atives. Again, where appropriate, these comments have been
incorporated into the regulatory options of this document. A
full listing of the respondents to the PD 1 can be found in
Appendix I at the end of this document.
-------
IV-7
F. REGULATORY OPTIONS
This section discusses the regulatory options for mitigating
risks from consumption of aldicarb-contaminated drinking water
and presents three possible options for protecting ground water
from contamination with aldicarb at levels that would cause
unreasonable adverse effects on the environment.
Before proposing any regulatory action concerning dietary
risks due to aldicarb residues on food, the Agency wishes to
examine the data from the registrant's food survey. The final
data have been submitted and are currently being evaluated.
After the data are reviewed, the Agency will conduct a final
dietary risk assessment.
1. PROTECTING GROUND WATER
The Agency recently introduced a number of long-term
strategies on significant environmental issues which require
cross-media coordination. One strategy under development
addresses agricultural chemicals in ground water. As part of the
strategy development process, the Agency sponsored a workshop at
Coolfont, in West Virginia, on June 24-27, 1986 and another on
July 23-24, 1987. The workshop participants discussed, among
other issues, regulatory strategies to limit the amount of
pesticides and fertilizers leaching into ground water. Repre-
sentatives of State health, environmental, and agricultural
offices; other Federal agencies; industry; user groups;
researchers; Cooperative Extension Service; and environmental
groups participated in those workshops. The options in this
section evolved from that process.
On February 26, 1988, the Agency announced its proposed
strategic plan for addressing ground water contamination by
pesticides (Agricultural Chemicals in Ground Water - Proposed
Pesticide Strategy, see also 53FR 5830). A copy of this
document may be obtained from: Environmental Protection Agency,
Public Information Center, PM-211B, 401 M Street, S.W.,
Washington, B.C. 20460. This document is the Agency's proposed
long-term strategic plan for protecting ground water from contam-
ination by pesticides.
The options of the proposed strategy are presented in this
Aldicarb Technical Support Bocument because they are pertinent to
the proposed regulatory decision for aldicarb. The Agency
requests comment on each of these options relative to aldicarb.
By requesting comment on all options, the Agency considers that
all options have been proposed and that any option could be
included in the Final Position Bocument without reproposal.
Individuals commenting on these options in a generic sense (i.e.,
not relating to aldicarb per se) should submit comments in
-------
IV- 8
response to the proposed strategy rather than to this position
document. These options reflect varying amounts of Federal and
state involvement. The amount of Federal and state involvement
reflects the level of concern in the Agency and state regulatory
offices about the potential for and risk associated with ground
water contamination.
The options for regulating the use of aldicarb for the pro-
tection of people exposed through drinking contaminated ground
water are:
Option 1 - Risk Reduction Measures/User Determines
Applicability
Option 2 - Labeling/Monitoring/State Management Plans
Determined by Heath Regions
Option 3 - Labeling/Monitoring/State Management Plans
Determined by County
1 — RISK prenUGTinigr MRASURES/USE
This option reflects a registrant submitted application for
amended registration which includes additional risk reduction
measures on the aldicarb label. Adoption of this option would be
appropriate if the Agency has concluded that the risks of
consuming ground water contaminated by aldicarb above a specified
level could be reduced to acceptable levels , provided various
risk reduction measures were adopted and followed. These
measures are:
a. Drinking Water Well Setbacks
There is a 300 foot well setback for all uses in Florida,
except for citrus in very sandy soils, where the setback is 1,000
feet. The premise of the drinking water well setback is that the
level of aldicarb residues, which leach into ground water, will
degrade sufficiently so that by the time they reach the drinking
water well, the concentration will not exceed 10 ppb. Parameters
affecting the well setback are rate of degradation and ground
water velocity.
The registrant has proposed the following additional
setbacks for wells. For purposes of these instructions, shallow
drinking water wells are defined as those wells which are cased
less than 100 feet deep and are cased less than 30 feet below the
water table. Additionally, for all other areas, there will be a
restriction that aldicarb not be applied within 50 feet of any
well used for drinking water, except where more restrictive state
regulations apply.
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IV-9
USE PROHIBITIONS:
The following environmental conditions, when all are present
in combination, reduce the rate of degradation of this product in
soil and may allow movement of the product residues to ground
water. Therefore, do not use this product when all these
conditions exist:
1) Fields with average soil temperature in the root zone
below 50° F at time of application;
2) Heavy anticipated rainfall within one month after use
(rainfall at rates substantially exceeding evaporation, based on
historical records);
3) Fields with soil averaging less than 15 percent (by
volume) field moisture holding capacity (permeable surface and
subsoils);
4) Fields with soil averaging less than one percent organic
matter in the top foot; and
5) Acidic subsoil (average pH less than 6.0).
USE RESTRICTIONS:
For ME. NH. VT
Do not apply within 500 feet of shallow drinking wells (as
defined above) if both of the following conditions are met:
* Soil type is sandy loam, loamy sand, or sand;
* The water table is less than 50 feet deep.
For NY. MA. RI. CT. NJ. PA. WI
Do not apply within 500 feet of shallow drinking wells if
all four of the following conditions are met:
* Soil type is sandy loam, loamy sand, or sand;
* Subsoil type is loamy sand or sand (with field
capacity less than 15 percent by volume);
* The average organic matter in the upper 12 inches is
less than two percent by weight; and
* The water table is less than 25 feet deep.
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IV-10
For DE. MD. VA
Do not apply within 300 feet of shallow drinking wells if
all four of the following conditions are met:
* Soil type is loamy sand or sand;
* Subsoil type is loamy sand or sand (with field
capacity less than 15 percent by volume);
* The average organic matter in the upper 12 inches is
less than two percent by weight; and
* The water table is less than 20 feet deep.
For NC. SC. GA
Do not apply within 300 feet of shallow drinking wells if
all four of the following conditions are met:
* Soil type is loamy sand or sand;
* Subsoil type is loamy sand or sand (with field
capacity less than 15 percent by volume);
* The average organic matter in the upper 12 inches is
less than two percent by weight; and
* The water table is less than 10 feet deep.
b. Application Rate, Frequency, and Timing Modifications
The registrant proposes to reduce the maximum application
rate for the insecticidal use of aldicarb in Florida on producing
pecan trees from 10 to 5 Ibs. a.i./A, and on newly transplanted
pecan trees from 5 to 3 Ibs. a.i./A. The registrant also pro-
poses to limit application timing for the insecticidal uses of
aldicarb on producing pecan trees and newly transplanted pecan
trees to between January 1 and April 30 (i.e., after the rainy
season) in Florida.
The registrant proposes to limit the number of applications
for non-containerized ornamental plants (flower crops, trees,
shrubs, bulb crops, foliage plants and small woody shrubs) to
once per year. The application rates would not be changed.
The registrant proposes that aldicarb application to potato
fields occur at post-emergence only in the following states: CT,
DE, MA, MD, ME, NH, NJ, NY, PA, RI, VA, VT, and WI. These re-
strictions coincide with warmer temperatures, higher soil micro-
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IV-11
organism activity, higher rate of aldicarb degradation, and
reduced amounts of aldicarb available for leaching.
Finally, the registrant proposes to restrict citrus appli-
cation to once per year.
c. Monitoring
The registrant proposes to monitor statistically represent-
ative drinking water wells and to provide activated carbon
filtration units to individuals with drinking water wells that
contain water with aldicarb contamination greater than 10 ppb.
d. General Restrictions
The registrant proposes a six-month general crop rotation
restriction. The company also proposes to provide a certified
applicator training course on best management practices to
protect ground water.
OPTION 2 - LARKT.TKfR/MONITORING/STATE MANACtKMRMT PLANS DETERMINED
BY HKATH REGIONS
The Agency has developed a second option which would require
a three-phase approach in protecting ground water and better
defining those areas where the possibility of ground water
contamination is the greatest. This option includes labeling
modifications, monitoring of ground water, and establishment of
State Pesticide Ground Water Management Plans (Management Plan)
in certain states. In identifying which states would need to
develop such plans, the Agency utilized the ground water
assessment by Heath Region as described in Chapter II. The
components of this option are described below.
1. LABELING COMPONENT
One means of reducing or eliminating the possibility of
ground water contamination by aldicarb is by imposing certain
label restrictions.
The previous option considered labeling as the sole risk
reduction measure. Option 2 considers labeling as one of several
risk reduction measures, with increasingly stringent measures
being used in increasingly vulnerable areas. Under this option,
labeling would be a minimum requirement applicable to any use of
aldicarb in any area of the country, regardless of whether the
state or county in which it is used has a Management Plan. The
label would prohibit application or mixing/loading operations of
aldicarb within 300 feet of any drinking water well. States
could set more stringent well setback requirements (including
more stringent ones for public wells vs. private wells) if they
so choose. The Agency believes that this measure will serve to
-------
IV-12
reduce contamination of drinking water because it reduces the
likelihood that aldicarb will directly contaminate a drinking
water supply.
The label would also designate aldicarb as a restricted use
pesticide due to ground water concerns. Aldicarb is already
classified as a restricted use pesticide due to its acute
toxicity. The ground water restriction would serve to heighten a
certified applicator's awareness of the concerns regarding the
possibility of ground water contamination and target aldicarb
users for training using the newly-developed ground water
educational module (soon to be available to the states).
The Agency has considered additional site conditional
measures that could be added to the label to deal with situations
where leaching has been shown to occur. For example, the Agency
has information which demonstrates that leaching occurs when
aldicarb is used on soils classified by the USDA Soil
Conservation Service as "sand" or "sandy loam" and when the field
overlies shallow ground water suitable for drinking, where
shallow is defined as an average water table depth of less than
30 feet. A site specific measure prohibiting use of aldicarb in
areas where these two conditions are met could be instituted.
However, the Agency has concerns whether this information is
available to growers and whether these prohibitions are
enforceable. Thus, the Agency is not specifically proposing site
conditional measures at this time but requests comment on their
feasibility.
2. MONITORING COMPONENT
The registrant would be required, under FIFRA section
3(c)(2)(B), to perform monitoring in representative areas rated
as medium. The registrant would be required to design monitoring
programs to evaluate the occurrence of aldicarb residues in
ground water associated with specific areas in states/counties
specified by the Agency.
The Agency would be deferring a proposal regarding the need
for additional regulatory measures (i.e., requirement for imple-
menting Management Plans) to manage the use of aldicarb in areas
not subject to the requirement for a Management Plan until these
additional monitoring data are submitted and assessed. This
deferral is due to information available which suggests that
medium areas are less susceptible to leaching than high
vulnerability areas. Data generated would be evaluated in order
to better characterize these areas. The Agency sees some
potential for leaching in medium vulnerability areas in large
part because of the variability of hydrogeological conditions.
However, because of the limits of the Agency's understanding of
this variability and how specific factors relate to leaching, the
Agency does not have as much basis for concern as in high
-------
IV-13
vulnerability areas. The Agency believes that additional
monitoring would significantly help the Agency to understand the
potential for aldicarb to leach in these medium vulnerability
areas. Consequently, the Agency is not proposing to regulate the
use of aldicarb by requiring additional regulatory measures in
these areas at this time. In the interim period, the use of
aldicarb in the medium vulnerability areas would be regulated
through labeling restrictions/prohibitions described in the prior
section.
The exact design of the monitoring program in the medium
vulnerability areas would be developed at a later date. The
registrant would conduct the monitoring under the provisions of
section 3(c)(2)(B). Monitoring would not be required in all
states/counties growing a particular crop but rather in repre-
sentative areas. The monitoring program would account for key
areas of vulnerability and use.
The protocols would contain at least the following key
ingredients:
1) Delineation of cropping areas of concern based on
aldicarb sales and/or crop acreage.
2) Further delineation of these identified areas on the
basis of hydrogeologic vulnerability (i.e., the more vulnerable
areas should be monitored.)
3) Sampling of existing wells within these delineated
areas. Candidate wells include all well types, e.g. , drinking
water wells, irrigation wells, USGS observation wells, or other
wells will need to be identified and described. There will be no
statistical component to well selection; wells are deliberately
selected and should only be those which could be impacted by
aldicarb use; i.e., in the vicinity of known or strongly
suspected aldicarb use-sites.
3. STATE PESTICIDE MANAGEMENT PLAN COMPONENT
The Agency believes that one of the best methods of pre-
venting ground water contamination by any pesticide is through
restrictions on use imposed under a Management Plan. There are
a number of approaches the Agency could use in providing guidance
to the states in developing Management Plans. These various
approaches range from establishing a performance standard based
on a goal of preventing unacceptable contamination (i.e., the
Maximum Contaminant Level or Health Advisory level) and allowing
the states to develop Management Plans to meet that standard, to
providing a specific Management Plan which all states must adopt.
The Agency favors a middle path of providing a framework for the
plan but providing flexibility to recognize that different states
may use different approaches in accomplishing the same goal of
-------
IV-14
protecting ground water from unacceptable contamination.
However, each state would need to meet the performance standard
through implementation of its Management Plan. The description
of the Management Plan can be found in APPENDIX II of this
document. The Agency is seeking extensive comment on the design
of Management Plans and will be sponsoring a series of regional
workshops beginning in summer 1988 to further explore the
concept.
As envisioned by the Agency, Management Plans would be a
comprehensive description of a state's approach for managing the
use of a pesticide(s) for the purpose of protecting the ground
water resource with specific attention given to preventing
unacceptable contamination of current and potential drinking
water supplies. The plan should:
(1) Describe the state's overall philosophy and approach to
protecting its ground waters from unacceptable pesticide contam-
ination.
(2) List the specific risk reduction measures to be employed
For example, the plan may include one or more of the following:
cancellation of use or moratoriums; reduction in the rate of use;
application method and timing limitations; more stringent well
setback restrictions; wellhead protection of public drinking
water; mixing and loading requirements; changes in agronomic
practices; permit or advance notice programs; and user education
training.
(3) Identify the state's enforcement authorities and capa-
bilities which can be used to assure compliance with the provi-
sions of the plan.
(4) Identify the location of ground water that is currently
and could potentially be a source of drinking water in the future
or that is of ecological importance.
(5) Contain a monitoring scheme designed to ensure that the
efforts to avoid contamination through proper use are effective
or to identify contamination resulting from misuse/accident.
(6) Establish contingency plans to deal with contaminated
ground water.
(7) In cases where contamination is at an unacceptable
level, describe the mechanisms to be used to reduce contam-
ination, including the source of funding.
(8) Describe how the public is kept informed and can become
involved.
-------
IV-15
The Agency requests comments on these and other possible
components of a Management Plan and discussion on whether a
middle path between the performance standard approach and the
specified plan approach is preferred.
The Agency realizes that there could be much variation among
state plans to account not only for differing state conditions
but also varying state approaches. The Agency would be flexible
in its review of the various state plans, recognizing that
different approaches can be used to obtain the same goal (i.e.,
preventing contamination or reducing the likelihood of a pest-
icide in ground water reaching an Agency-designated level).
States may elect to work collectively in developing various
components of a plan; however, each state would be responsible
for the development and implementation of its own plan.
The Management Plan should basically be a two-part strategy:
a generic part to deal with pesticides which are regulated for
ground water purposes and a chemical-specific (aldicarb) part.
The generic part of the plan should set forth the basics for
implementing a plan which could be used for any pesticide. The
chemical-specific part should include only those portions of the
plan that are specific to aldicarb, such as monitoring designs to
ensure compliance with the Health Advisory and identifying areas
of aldicarb use.
Management Plans would be needed for those areas designated
as having the greatest potential for aldicarb to reach ground
water. As described in Chapter II, the Agency used two methods
of assessing the potential for ground water contamination: one
which uses the Heath Region as the geographical unit and one
which uses the county. The need to implement Management Plans
will differ depending on which assessment is relied upon to
identify those areas where there is the greatest possibility of
aldicarb reaching ground water. The following discussion
describes the Heath Region assessment in terms of how it relates
to this option.
Although the Agency believes it would be advantageous for
all states to implement Management Plans, it realizes that it
would be onerous for both states and the Agency. Therefore, the
Agency has developed this option, using the Heath Region approach
of ground water assessment, to identify states that would need to
implement a Management Plan.
To identify which states would need to develop Management
Plans, the Agency first identified the areas where there is the
greatest possibility of ground water contamination resulting from
the use of aldicarb. The ground water assessment by Heath
Region, as discussed previously, identified those areas potatoes
are grown in Heath Regions 7 and 9 and those areas citrus and
\peanuts are grown in Heath Region 11, as having the greatest
-------
IV-16
possibility of ground water contamination resulting from aldicarb
use.
The Agency then looked at the states which account for a
large percent of the areas where aldicarb could be expected to be
used the most and that contained a significant percent of the
acreage of the crop (of the crop/Heath Region combination rated
as highly vulnerable) in the high vulnerability areas.
For example, potato growing areas in Heath Regions 7 and 9
were rated as having a high vulnerability. In order to determine
which states had the greatest number of acres within these Heath
Regions, county totals of potato acreage from the 1980 Ag Census
were summed. (In those instances where a state is divided by a
Heath Region, only the potato acreage within the Heath Region was
considered.) Then, those states with the greatest potato acreage
within the two Heath Regions were identified.
It was determined that seven states (ND, MN, MI, WI, NY, PA,
and ME) account for 98 percent of the potato acreage in Regions 7
and 9. Further, three states in Heath Region 11 (AL, FL and GA)
account for virtually 100 percent of the peanut and citrus
acreage within that Region. Therefore, there are 10 states that
would need to submit Management Plans (ND, MN, MI, WI, NY, PA,
ME, AL, FL, and GA). There are 480 counties in these 10 states
that are considered to be highly vulnerable and in 165 of these,
aldicarb is used. Therefore, this option would cover 68 percent
of the highly vulnerable counties in these three regions in which
aldicarb is used. Other states in these regions with lower
acreage would be covered by national labeling requirements and by
monitoring requirements.
Additionally, as a condition for registration, the reg-
istrant would have to agree to monitor in high vulnerability
areas where aldicarb is used which are not subject to a
Management Plan. This would involve monitoring in the states of
SC, CT, IA, IL, IN, KS, MA, MO, MT, NE, NH, OH, RI, SD, VT, and
HI.
This monitoring effort would involve sampling in fields
where aldicarb is used. The wells to be sampled could either be
suitable existing wells or specially constructed monitoring
wells. Monitoring would be performed over a specified period of
time and the data would be evaluated in order to assess the
effect of the imposed labelling restrictions in terms of elim-
inating or reducing ground water contamination.
OPTION 3 - LABELING/MONITORING/STATE MANAGEMENT PLANS DETERMINED
BY COUNTY
This third option is identical to Option 2 in that it would
have the same labeling and monitoring components. However, the
-------
IV-17
states that would need to develop Management Plans would be
identified using a county approach which identified counties
where the Agency believes aldicarb has the highest tendency to
leaching. Under this approach, states would need to develop and
implement a Management Plan for those counties classified as
such.
The criteria used to identify which counties would need a
Management Plan are very similar to those used to select states
in Option 2. The major difference is the size of the geographic
area being analyzed. The criteria are hydrogeologic vulner-
ability, use/usage of aldicarb, and availability of positive
monitoring data. These criteria are detailed in Chapter II.
In the four states that the Agency selected as examples for
this assessment, California has 3 out of 58 counties, Florida has
26 out of 67 counties, and Wisconsin has 8 out of 72 counties
needing a Management Plan. North Carolina did not have any
counties which were ranked high enough to need the establishment
of a Management Plan. However, the vulnerability to ground water
contamination was sufficiently high in all other counties in each
of these four states to be classified as medium in vulnerability.
The registrant will be required to undertake a monitoring study
that will be representative of those moderately vulnerable areas.
The Agency has not completed an assessment of all counties
within the United States. However, the Agency estimates that
between 15 and 24 states would need to generate a Management Plan
under this option. If this option is adopted, the Agency would
apply these criteria to all counties to identify those which need
a Management Plan.
G. RISK/BENEFIT ANALYSIS OF REGULATORY OPTIONS
1. INTRODUCTION
In the previous two chapters of this document, the Agency
evaluated the risks and benefits of the use of aldicarb and
considered the regulatory means by which the risks might be
reduced. The purpose of this section is to determine the most
appropriate regulatory options and modifications for each use of
aldicarb. To accomplish this, the risks of use are compared with
the benefits of use. If this comparison shows that there are
unreasonable adverse effects to man from the current use pat-
terns, the regulatory options are evaluated to determine which
produces the most favorable balance of the risks and benefits.
2. DIETARY EXPOSURE TO ALDICARB RESIDUES IN TREATED
COMMODITIES
The Agency is deferring a decision regarding the potential
risks due to dietary exposure to aldicarb from consumption of
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IV-18
treated food commodities until the final results from the
registrant's National Food Survey have been evaluated. At such
time, the Agency will consider whether further regulatory action
will be necessary.
3. DIETARY EXPOSURE TO CONTAMINATED GROUND WATER
a. Introduction
This section analyzes the options the Agency explored to
mitigate the risks of ground water contamination due to the use
of aldicarb.
Limitations on the scientific understanding of ground water
contamination, as well as limitations in the available data base,
make it difficult to perform a quantitative risk analysis for
these various options. Traditionally, quantitative risk analyses
have been conducted to assess the impact of various regulatory
mechanisms designed to reduce dietary exposure from consumption
of treated crops and/or applicator exposure. Data are available
or can be generated which can provide fairly accurate estimates
of the levels of such exposure likely to result from application
of a pesticide. In contrast to dietary exposure, many factors
influence how much aldicarb will leach into ground water and
those factors vary greatly from location to location. Therefore,
while available data allow the Agency to predict those conditions
for which there exists the greatest potential for aldicarb to
reach the ground water, the Agency has a limited ability to
estimate levels of exposure or the size of the exposed
population. For example, hydrogeologic variation is so great
that it cannot be predicted with great certainty where
contamination is likely to occur and the level of contamination
in those instances. One of the key problems is the Agency's in-
ability to make general statements, on a national or local basis,
about the proximity of drinking water wells to fields where aldi-
carb is used. As a consequence, neither the number of individ-
uals exposed to drinking water contaminated with aldicarb at
levels of concern nor the length of time they will be exposed can
be estimated accurately. However, given the low level at which
there is a risk from drinking water contaminated with aldicarb
and the numerous areas in which aldicarb has already been de-
tected, the Agency is concerned in all instances where leaching
would appear likely to occur.
Complicating the risk/benefit analysis in this case is the
difficulty of placing a value on ground water. The Agency
believes that ground water is a valuable resource and that its
protection from unacceptable contamination is extremely
important. Once contaminated, clean-up of an aquifer is
exceptionally expensive or technically difficult, especially if
the contamination is at a low level and widespread. If an
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IV-19
alternate water source is to be provided, it can be both costly
and i nc onven i ent.
The Agency has analyzed the risks of aldicarb resulting from
ground water contamination, as well as the associated benefits,
and concludes that use of aldicarb generally causes unreasonable
adverse effects on the environment. As explained below, in the
Agency's judgement, the risks from all uses of aldicarb exceed
the benefits of such use. Because the Agency concludes that the
risks are predominantly associated with use in certain highly
vulnerable areas of the country, and because the Agency has no
reason to think that the corresponding benefits of such use are
disproportionately associated with such use sites, the Agency is
proposing to require Management Plans in highly vulnerable areas.
As explained in Chapter II, people are at risk from
consuming water contaminated with aldicarb residues. Although it
is not possible at this time to generate reliable quantitative
estimates of either the number of people exposed to contaminated
ground water or the levels of such exposure, some information
exists which enables the Agency to put the risks associated with
ground water contamination into perspective. The extent of
aldicarb contamination of ground water is significant. Thousands
of wells have been contaminated with detectable levels of
aldicarb. The Agency evaluated studies which comprise over
35,000 samples of ground water from some vulnerable areas. As
described in Table II-4, nearly one-third of all samples in these
studies were positive, and over half of the positive samples
exceeded the Health Advisory.
Many areas of the country where aldicarb is used are
vulnerable to contamination (see Chapter II), and not all of
these areas have been sampled. Therefore, it is reasonable to
assume that there are other wells which have been contaminated by
aldicarb but which have not yet been identified.
Available information also indicate that the eventual cost
of preventing exposure to drinking water contaminated with
unacceptable levels of aldicarb could be quite sizable. Ground
water contamination in Suffolk County= New York, serves as an
example of how significant these costs can be. Since 1980,
granular activated carbon treatment units have been installed in
3104 households where the water supply had been contaminated by
aldicarb above 7 ppb. (The New York State Health Department
established 7 ppb as the allowable guideline level for aldicarb
residues in drinking water.) The cost of each filter is
approximately $600 and the costs of installation are about $100.
On the average, each filter is effective for one year after which
,time it must be replaced. The costs for a replacement filter and
for installing it are about $150. The total costs for filters
and the initial installation for Suffolk County is approximately
$2.2 million with annual replacement costs of $465,600.
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The Agency believes that the total cost of cleaning up such
wells could approach or even exceed the total benefits of
aldicarb which have been estimated up to $135 million a year.
Obviously, clean-up costs are not the only measure of risk, since
some exposure would occur before filters are installed for a
water supply. In light of all potential risks, therefore the
Agency concludes that the risks posed from consuming water
contaminated by aldicarb above the Health Advisory outweigh the
benefits of use.
When the Agency concludes that the risks of use of a
pesticide outweigh the benefits, it may propose to cancel the
registration of all products containing that pesticide. In the
case of aldicarb, however, the Agency believes that cancellation
of all use is not necessary since less stringent regulatory
restrictions are capable of reducing the risks to a point where
the remaining benefits outweigh the risks. As indicated in
Chapter II, the likelihood of ground water contamination varies
throughout the country. The Agency believes that the greatest
risks are associated with aldicarb use in areas where the ground
water is highly vulnerable to contamination. By prohibiting or
restricting the use of aldicarb in those vulnerable areas, the
Agency concludes that the risks of aldicarb would be signif-
icantly reduced to a level where they would no longer outweigh
the remaining benefits. This conclusion is justified because the
Agency has no reason to believe that the benefits of aldicarb are
significantly greater in highly vulnerable areas than in less
vulnerable areas. Thus, while regulatory actions to reduce the
risk in vulnerable areas may have some impact on benefits, the
overall impact of such actions should be to improve the balance
of risks and benefits. The Agency believes that the combination
of measures recommended in this document would allow the con-
tinued use of aldicarb without unreasonable adverse effects on
the environment.
In summary, the Agency believes that ground water is a
natural resource which must be protected from contamination by
pesticides. There are many instances in which aldicarb, an
acutely toxic pesticide, has contaminated ground water above the
Health Advisory. Data available to the Agency confirm that
aldicarb has a great leaching potential. The Agency's assessment
methods, using the Heath Region or county approach, can target
areas where there is the greatest possibility of aldicarb
leaching to ground water above the Health Advisory. It is in
these areas that the Agency believes that the use of aldicarb
must be regulated most stringently. The Agency believes that the
states can accomplish this most effectively through Management
Plans. Although the Agency considers that aldicarb is an
important agricultural chemical which provides substantial
benefits to growers and producers, it believes that the risks
from unacceptable ground water contamination resulting from
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IV-21
aldicarb use in the vulnerable areas outweigh the benefits.
Consequently, regulatory action to prevent ground water
contamination is necessary.
The following section discusses in detail the various
regulatory options considered to mitigate the risks of ground
water contamination.
b. Discussion of Ground Water Options
1) Option 1 - Risk Reduction Measures/User
Determines Applicability
This option reflects the registrant submitted proposal to
place additional risk reduction measures on aldicarb labels.
These measures would be targeted to the users and the costs of
monitoring ground water contamination and corrective actions
would be borne by the registrant. Preventive measures could be
tailored to specific conditions of the application site in order
to prevent contamination of drinking water wells above the Health
Advisory in high or medium vulnerability areas.
The Agency believes that if implemented accurately by users,
the registrant's proposal would reduce ground water contamin-
ation. The Agency believes, however, that this option would
result in a label which is excessively difficult for users to
interpret and states to enforce. Also, this approach emphasizes
protection of existing drinking water sources rather than ground
water in general. Since ground water can be a potential drinking
water source, simply protecting existing drinking water wells is
insufficient because aldicarb could still reach the ground water.
If this option were adopted, it would have to include a
comprehensive monitoring program which is designed to test a
statistically significant number of sites where aldicarb is
being used.
The Agency concludes, in view of the benefits, that levels
of aldicarb not exceeding the 10 ppb Health Advisory are
sufficiently protective of human health. However, once levels
are detected, even if they are detected at levels below 10 ppb,
there is no assurance that they will stay at that level. Thus,
this option would need to include the additional provision for a
corrective action program whenever aldicarb levels are detected.
Different prevention measures would apply in different areas
depending on the specific climatic and soil conditions associated
with the application site. The risk reduction associated with
this option may be considerable. Not only is there a substantial
reduction in the likelihood that ground water will be contamin-
ated, but there is also a provision for detecting any contamin-
ation which does occur.
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IV-2 2
The costs of this option could be considerable. The risk
reduction measures themselves will result in increased costs in
the use of aldicarb as well as a prohibition on its use on
certain farms where it is now used or at certain times when it
is now used without restrictions. There are additional costs
associated with monitoring and implementing corrective action
plans.
Additionally, the restrictions are very technical, requiring
knowledge of soil type and temperature, and depth to ground
water. It will be difficult in some instances for growers to
obtain this information and for states to determine whether the
use of aldicarb is appropriate.
As stated earlier, the Agency believes that the registrant's
proposal has merits in reducing or eliminating ground water
contamination. Therefore, the Agency is prepared to accept some
of the proposals set forth by the registrant. Specifically, the
Agency will be amending aldicarb registrations to incorporate
modifications relating to reduction of the rate and frequency of
application, and restricting the period of time aldicarb may be
applied. The Agency believes these modifications are straight-
forward to interpret and, thus, generally easier to enforce. It
should be noted, however, that these modifications alone are not
considered to be adequate to mitigate the potential for
contamination of ground water above the Health Advisory.
2) Option 2 - Labeling/Monitoring/State
Management Plans Determined by Heath Region
This option provides states the opportunity to play an
active role in protecting ground water. This option requires
labeling modifications for all aldicarb use which will provide a
basic level of protection against ground water contamination and
a monitoring requirement. It also identifies, using the Heath
Region ground water assessment, those states which would need to
implement Management Plans in areas where there is the highest
likelihood of ground water contamination by aldicarb.
(i) Labeling
Under this option, specific labeling modifications would be
required. Such labeling would apply to aldicarb use throughout
the country. Specifically, the modifications required would be
restricted use due to ground water concerns. Since aldicarb is
already a restricted use pesticide due to its acute toxicity, it
is not believed that this requirement will impact significantly
on the costs associated with applying aldicarb.
Another labeling modification which will be required is a
300 foot drinking water well setback. The Agency believes that
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IV-2 3
this measure will serve to reduce contamination of drinking water
because it reduces the likelihood that aldicarb will directly
contaminate a drinking water supply. It is difficult to estimate
the costs incurred from not using aldicarb in these areas since
the Agency has no basis to estimate the number of wells in areas
treated with aldicarb. Some reduction in use is anticipated,
but the impacts are not expected to be significant. The Agency
requests comment on whether the 300 foot length is appropriate,
or whether a greater or lesser length should be established.
Finally, the Agency is seeking comment on whether site con-
ditional measures should be required for aldicarb labels. A
specific measure has not been proposed. The Agency believes that
unacceptable ground water contamination is likely to occur in
certain situations, e.g., when applied to a certain soil type
when the depth-to-ground water is less than a specified number of
feet. Consequently, a label restriction prohibiting use of
aldicarb in such instances would be useful in preventing
unacceptable ground water contamination. However, given that a
specific measure has yet to be identified, the Agency cannot
comment on the level of risk protection afforded or the cost
impacts resulting from implementing this measure.
(ii) Monitoring
Monitoring in areas representative of medium vulnerability
is an integral part of this option. The data generated will be
used in deciding whether further regulatory action (i.e., imple-
menting Management Plans) will be needed in these areas. The
costs associated with generating these data will not be
considered part of the risk/benefit analysis as it is part of the
expense involved in supporting the continued registration of this
pesticide. However, states with areas classified as medium
vulnerability, depending on the outcome of the review of
monitoring data, may need to implement a Management Plan. Since
this review and identification process will not occur until
sometime in the future, the specific costs associated with the
implementation of Management Plan in such instances cannot be
discussed at this time.
(iii) Management Plans
Management Plans provide the greatest site-specific
assurances of proper use without overly protecting areas where
unacceptable contamination is unlikely. Management Plans put the
primary responsibility on the state for regulating these specific
areas and allows for evaluation of site-specific prevention
measures based on the use, value and vulnerability of ground
waters. The areas where use of aldicarb that will need to be
addressed by Management Plan under this option are entire states.
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IV-2 4
Using the Heath Region ground water assessment, ten "high
vulnerability" states would need to implement Management Plans.
Additionally, monitoring would be required in "high vulner-
ability" states which do not need to implement Management Plans.
It is the intent of the Agency to cancel the use of aldicarb in
those states where a state would need to, but decided not to,
implement a Management Plan.
The estimated cost resulting from cancellation in the ten
states assuming that a Management Plan were not developed, could
exceed $60 million.
The Agency has evaluated the possible costs for developing
and implementing Management Plans in the ten states. Estimates
of the possible costs were developed from available published
data where possible. For some cost components (e.g., number of
wells affected, severity of contamination, exposed population,
duration of contamination,) precise data were not available to
estimate the potential costs associated with these plans.
Furthermore, environmental and geographic conditions vary widely
among and between the states needed to submit Management Plans.
Without knowing in advance the measures each state may wish to
employ to manage the use of aldicarb, precise estimates could not
be developed. The Agency is aware that further refinement of the
estimated costs will be necessary as more data become available.
Given the data limitations, the Agency believes that the cost
estimates are sufficiently accurate to serve as input in
assessing initial economic effects.
The costs associated with the development and implementation
of the Management Plans must also be taken into account for this
option. The following cost estimates have been developed for the
Heath Region approach.
Through conversations with various state agencies that
currently have management programs, it is estimated that the
development and set up costs of Management Plan could range from
about $150,000 to $710,000 per state for the 10 states needed to
submit Management Plans. These costs would include the expenses
associated with the actual development or structuring of the
Management Plan ($10,000 to $25,000), construction of compliance
monitoring wells including easements and land costs ($44,000 to
$488,000), and mapping ($100,000 to $200,000). (Some of the
development costs would roughly be the same for both approaches
as the costs are not dependent on whether the entire state or
only one county needed to be governed by a Management Plan.)
Development and set up costs are a one-time expense. Should a
state need to have Management Plan for another pesticide, part of
the requirements for Management Plan would have been satisfied by
the aldicarb Management Plan. Similarly, compliance monitoring
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IV-25
wells could also be used in detecting ground water contamination
from other pesticides applied to the same fields as aldicarb.
The Management Plans would also have annual costs associated
with implementation. These costs are estimated to range from
$275,000 to $434,000 on a per state basis. These costs would
include the expenses of such activities as enforcement, sampling
and analysis for aldicarb contamination. These costs would occur
on a yearly basis but may decline if fewer samples are analyzed
in later years or if voluntary compliance reduces enforcement
costs.
In its Management Plan, a state will define those conditions
under which the use of aldicarb may be allowed. These include,
for example: banning the use in certain areas or under certain
conditions, specifying how much aldicarb may be used on a per
acre basis, or how many times aldicarb may be applied per year.
The Agency expects that the Management Plan will result in
reducing the probability of ground water contamination by
aldicarb above the Health Advisory in the areas covered by the
Management Plan and thus reduce the risk to an acceptable level.
In determining whether it is worthwhile to implement a
Management Plan or allow use of aldicarb to be banned, one must
also consider the long-term in addition to short-term costs.
Even though it has been estimated that the first year costs for
the development, set up, and implementation of Management Plans
in the 10 states could be as high as $8.17 million; $4.7 million
would be one-time costs. Additionally, if other pesticides which
leach require similar regulation in the future, some of the costs
would already have been borne from regulating aldicarb. For
example, the costs to develop a Management Plan do not occur on a
yearly basis. Once a Management Plan is in place, it would be
fairly easy to apply it to another pesticide which leaches.
Similarly, although construction of compliance monitoring wells
is fairly expensive, this is also a one-time expense. These
wells may be used to determine whether other pesticides being
applied in the same field are reaching the ground water.
Finally, if it is determined that the Management Plan was
successful in eliminating the leaching of aldicarb into ground
water, requirements for sampling, one of the more expensive
yearly costs associated with implementation of Management Plan,
may be greatly reduced or eliminated. In addition, the potential
costs of remedial actions which can range from several hundred
dollars to more than $2,000 per household (annualized for five
years), would also be eliminated if the Management Plan was
successful in protecting ground water from unacceptable
contamination. The estimated cost resulting from cancellation in
the ten states, assuming than a Management Plan were not
developed, could exceed $60 million.
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IV- 2 6
3) Option 3 - Labeling/Monitoring/State Management Plans
Determined by County
This third option is identical to Option 2 in that it would
have the same labeling and monitoring components. However, the
states that would need to develop Management Plans would be
identified using a county approach which identified counties
where the Agency believes aldicarb has the highest tendency to
leaching. Under this approach, states would need to develop and
implement a Management Plan for those counties classified as
such.
The Agency has not completed an assessment of all counties
within the United States. If this option is adopted, the Agency
would apply these criteria to all counties to identify those
which need a Management Plan. Because the total number of
counties needing a Management Plan is not yet identified, the
costs resulting from a cancellation action under the county
approach, assuming none of the states submit Management Plans for
their county(ies), cannot be estimated at this time. However,
the Agency believes this cost would lie in the range of the costs
associated with the Heath Region approach and those resulting
from cancellation of all aldicarb uses (i.e., between $60 million
and $104 to $135 million).
H. PRQpnsF-n ACTIONS
The Agency is deferring a decision regarding the potential
risks due to dietary exposure to aldicarb from consumption of
treated food commodities until the final results from the
registrant's National Food Survey are evaluated. At such time,
the Agency will consider whether further regulatory action will
be necessary.
The Agency believes that ground water is a natural resource
which must be protected from unacceptable contamination by
pesticides. Data available to The Agency confirm that aldicarb
has a great leaching potential and that contamination of ground
water above the Health Advisory has occurred in many instances.
The Agency's ground water assessment methods, using the Heath
Region or county approach, have examined areas of the country
where aldicarb is used and have identified areas which are highly
vulnerable to contamination. The Agency believes that
contamination above the Health Advisory is likely to occur at
sites throughout these areas.
There are risks to people consuming drinking water
contaminated by aldicarb above the Health Advisory. While the
Agency cannot predict the level of exposure to contaminated
drinking water or the number of people exposed to such contam-
ination, it is known that many wells have been contaminated by
aldicarb. Available information suggests that the costs of
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IV-2 7
correcting such contamination would be considerable. The Agency
concludes that on a national basis, the risks posed from contam-
ination outweigh the benefits of use. Consequently, regulatory
action to prevent ground water contamination is necessary to
prevent unreasonable adverse effects on the environment.
The Agency believes that it is possible to reduce the risks
significantly by imposing certain regulatory restrictions short
of cancellation of all use. These restrictions would be a
graduated response to an area's vulnerability in such a way that
the most stringent measures would be required in areas where
there is the highest likelihood of unacceptable ground water
contamination. The Agency believes that such restrictions would
reduce exposure to a point where the remaining benefits would
outweigh the risks of use.
The Agency has evaluated three options to prevent the
unacceptable contamination of the nation's ground water by
aldicarb and believes that Management Plans afford the greatest
assurance of protecting ground water contamination without
overprotecting areas where contamination is unlikely or can
reasonably be prevented. The Agency further believes that it is
necessary to impose certain restrictions on the use of aldicarb
as a basic level of protection nationwide in order to reduce the
potential for ground water contamination. Additionally, The
Agency does not believe that there are adequate data available to
predict the likelihood of the contamination of ground water in
medium vulnerability areas.
Options 2 and 3 both accomplish these goals. They classify
aldicarb as a restricted use pesticide due to its ground water
contamination potential, in addition to its acute toxicity. They
also provide a 300-foot well set-back on aldicarb use and require
monitoring in medium vulnerability areas and Management Plans in
the areas where ground water contamination is most likely to
occur. Option 2 uses the Heath Region approach in identifying
the need for Management Plans on a state basis and Option 3 uses
the county approach in identifying the need for Management Plans
on a county basis. Because of the legal mechanisms established
under FIFRA for accomplishing these goals, the alternative to
establishing Management Plans in those states or counties where a
Management Plan is needed but not implemented is cancellation of
aldicarb use in those areas. The Agency is seeking public
comment as to whether Option 2 (state approach) or Option 3
(county approach) is favored.
The major problem with the Options 2 and 3 is that some
states may not have the legal authority, technical skills, or
resources to establish or implement an effective Management Plan.
Both approaches provide states a strong incentive to submit an
acceptable Management Plan since, without it, use in the entire
state or certain counties would be prohibited. In contrast to
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IV-2 8
the county approach, the Heath Region approach may be more likely
to have areas that are either overly protected or underprotected
since the classification of vulnerability was based on large
Heath Regions. The county evaluation was based on a more
specific geographic unit, the county.
The Agency proposes Options 2 and 3 to impose label
restrictions and monitoring requirements, and to allow the use of
aldicarb in certain states/counties which have approved
Management Plans and cancel the use of aldicarb in certain
states/counties which choose not to implement Management Plans.
In comparing the two options proposed by the Agency, three
basic differences are evident. Under Option 2, the state would
need to implement a Management Plan which addresses all counties
within the state rather than only specified counties as under
Option 3. However, the Agency recognizes that in addressing each
county in a statewide plan, the state may properly conclude that
only certain counties need to implement risk reduction measures.
Another difference is the number of states which would need to
implement a Management Plan. The Agency estimated that the
number of states which would need to implement a Management Plan
under the approach in Option 3 will be between 15 and 24 compared
to the ten states identified under Option 2.
Finally, under Option 3, states would need to implement a
Management Plan in all counties with a high potential to leach.
Under Option 2, there are a number of states containing areas
rated as having a high potential to leach (but with low aldicarb
use) which would not need to implement a Management Plan. In
these states the registrant, as a condition of registration,
would be required to monitor ground water in high vulnerability
areas to assure that the national uniform measures are sufficient
to prevent ground water contamination at levels that would cause
unreasonable adverse effects on the environment.
The Agency is considering two different procedures for
implementing the provisions of Options 2 and 3. Under one
procedure. The Agency would implement the Management Plan
approach using the cancellation procedures in FIFRA section 6.
In general, after appropriate opportunities for public and state
participation, the Agency would seek to cancel the use of
aldicarb in areas where a Management Plan was considered neces-
sary to prevent unreasonable adverse effects on the environment
but for which areas no adequate Management Plan had been
developed. As the first step of this process, once the Agency
decided how it would select the areas for which Management Plans
are needed, it would explain the selection procedure, identify
the areas, and establish a deadline for states to submit a
description of their plans. Following the Agency review and an
opportunity for states to improve any plans which The Agency
might consider inadequate, the Agency would issue a Notice of
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IV-2 9
Intent to Cancel, identifying those areas in which cancellation
would occur. Registrants and other adversely affected persons
would then have an opportunity to challenge the Agency's
determinations in an adjudicatory hearing under FIFRA section 6.
Because the cancellation process can be so lengthy and
consumes so many resources, the Agency is considering an
alternative process. The alternative process would rely on the
authority in FIFRA §3(d)(l)(C) to issue regulations classifying a
pesticide for restricted use and imposing "other regulatory
restrictions" on its use. Generally, the Agency would issue a
proposed and final rule under FIFRA S3(d)(l)(C) which restricted
the use of aldicarb in certain areas (e.g., the areas identified
using Option 4) to use in conformity with Management Plan. The
regulations would establish requirements for the content of
Management Plans; procedures for comment and review of Management
Plans by the Agency; and implementation by the states.
The Agency requests public comment on these alternative
procedures for implementing the Management Plan approach. The
Agency is particularly interested in comments addressing the time
needed for full implementation under each alternative. In
addition, if the rulemaking approach is chosen, the Agency is
interested in the procedures that should be established for
review and approval of Management Plans. Finally, the Agency
would be interested in other proposals on the process that should
be used to implement Management Plan approach.
The Agency is also soliciting public comment on the labeling
requirement that aldicarb not be applied any closer than 300 feet
of a drinking water well. Comment is specifically being
requested on whether a 300-foot setback is appropriate, whether
it should be a greater or lesser length, and whether there should
be a different prohibition for public versus private wells. The
Agency is also interested in the anticipated impacts resulting
from the proposed well setback in terms of decreases expected to
yields.
In addition, because the regulatory approach recommended by
the Agency differs significantly from previous decisions under
FIFRA, the Agency requests comment on the way in which it has
explained and supported its position. In particular, the Agency
invites public comment on the most appropriate analytical
framework for weighing risks and benefits for a pesticide which
has the potential to contaminate ground water. Should a more
quantitative risk assessment be performed and if so, how should
it be performed? What should be included in the assessment,
(e.g., number of people exposed, cost of monitoring, treatment or
clean-up, lost land values, value of potential drinking water)?
At what level of resolution should the benefits analysis be
conducted, (e.g., national, state, county, or local)? In making
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risk/benefit decisions on the county level, the Agency could
consider information such as the following:
1) The importance of aldicarb to the county, including the
relative size of the contribution aldicarb-treated crops make to
the local economy and additional local employment which depends
on these crops (e.g., processing plants).
2) The importance of ground water to the county, including
the extent to which the community depends on ground water as a
drinking water source, the number of people who rely on private
wells for drinking water, the degree to which this dependence is
likely to change, and the importance of ground water in terms of
projected land use (e.g., possible residential, commercial, or
industrial development).
3) Management costs associated with mitigating the effects
of the use of aldicarb in communities, including monitoring,
point-of-use controls, importation of water, and clean-up costs.
4) The importance of conditions on efficacy of alternatives
to aldicarb, including unique or special climatological or
agronomic factors (e.g., age of citrus trees, amount and timing
of rainfall).
5) Aldicarb's effectiveness, use (i.e., application rate by
crop and county and usage), especially for high value (e.g.,
ornamentals), continuous cultivation crops (e.g., bananas), and
crops with rapidly changing usage (e.g., soybeans).
The Agency is soliciting comments on the appropriateness of
the above factors, on additional factors which should also be
considered, and on who should be responsible for developing this
information. The Agency proposes that outside parties (e.g., the
registrant or user groups) interested in retaining the local use
of aldicarb, will be responsible for gathering and providing
local information needed to rebut the Agency's presumption that
risks outweigh benefits when the Health Advisory is exceeded.
When looking at regulatory decisions affecting a particular
geographical area (e.g., a state or county), how should the
Agency evaluate risks and benefits? Who is responsible for
gathering information to support such an analysis and who should
conduct the analysis (i.e., the Agency or the states)? At what
stage of the regulatory process should such an analysis be
performed? Under what circumstances, if any, should a state
perform the analysis?
The Agency also requests comment on the analytical
approaches it has used to identify the areas in which aldicarb
use is most likely to contaminate ground water. In particular,
the Agency invites consideration of alternative criteria in
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applying the county-based analysis such as: setting the break
points between high, medium, and low ratings for vulnerability at
different DRASTIC scores, and giving a higher usage rating to
counties in which root crops constitute a larger percentage of
use. The Agency also invites comment on the break points which
were used in determining where a state needs to implement
Management Plan for all or some of the counties.
The Agency recognizes that the criteria used in assessing
the potential for aldicarb to leach to the ground water and thus
whether a county or state needs Management Plan, create
inconsistencies. For example, under the Heath Region assessment,
counties which have a high potential to leach would not be
subject to Management Plan or monitoring by the registrant if the
counties are not within a state which was part of a crop/Heath
Region combination rated high in terms of potential to leach.
Similarly, under the county assessment, various areas of a county
may have a high potential to leach but the majority of the county
has a medium potential to leach. Consequently, the state would
not have to implement Management Plan for that county.
The Agency is also seeking comments in three other areas
which are pertinent to the regulatory actions proposed. First,
comments are being solicited on whether it is appropriate for the
registrant to be involved in refining assessments regarding the
likelihood of ground water contamination in an area and, if so,
how such an assessment should be performed. The areas where such
an assessment would occur should also be addressed. For example,
instead of relying on a county's DRASTIC rating in a medium
vulnerability area, the registrant could be required to assess
vulnerability to leaching at the sub-county level, based on such
factors as soil type, depth to ground water level, and location
of crops which may be treated with aldicarb. This information
would then be used as a basis to determine whether Management
Plan would be needed.
The Agency is also interested in obtaining additional
information on the costs associated with the development and
implementation of Management Plans. Another related issue the
Agency is concerned with is the level of involvement the
registrant should have in developing Management Plans. Comments
are being solicited both on the appropriateness of registrant
involvement in developing Management Plans, and whether there
should be a limit to their involvement.
Finally, the Agency is soliciting comment regarding the
issue of ground water contamination and liability. One un-
resolved question regarding ground water contamination is who is
responsible for remedial action (e.g. developing, approving, and
implementing corrective action plans such as funding clean-up
costs or providing an alternate water supply) when contamination
results from a registered pesticide use. The Agency's proposed
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IV-3 2
ground water strategy documentf Agricultural Chemicals in Ground
Water; Proposed Pesticide Strategy,, discusses this issue in more
detail. Ground water contamination and liability is a generic
issue which pertains to all pesticides which leach rather than
just to aldicarb; consequently, any comments regarding this issue
should be made in response to the above document.
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V-l
BIBLIOGRAPHY
Alexander, W. J. ; Liddle, S.K. ; Mason, R.E.; and Yeager, W.B.
(1986) Ground Water Vulnerability Assessment in Support of
the First Stage of -the National Pesticide Survey, prepared by
Research Triangle Institute for EPA, Contract 68-01-6646.
Aller, L.T. ; Bennett, J.H. ; and Petty, R.J. (1985) DRASTIC: A
Standardized System for Evaluating Ground Water Pollution
Potential Using Hydrogeologic Settings, EPA/600/2-85/018.
Andreoli, A. (1986) Summary Pesticide Sampling Program,
1980-1985, (unpublished report prepared by the Drinking Water
Section, Bureau of Water Resources, Suffolk County Department
of Health Services).
Baier, J. and Moran, D. (1961) Status Report on Aldicarb Contam-
ination of Groundwater as of September 1981 (unpublished
report prepared by the Bureau of Water Resources , Suffolk
County Department of Health Services, received by EPA on
December 4, 1981).
Brokopp, C.D. (1987) Examination of Drinking Water for Aldicarb,
(unpublished study submitted by the State of Idaho Department
of Health and Welfare) .
Carsel, R.F. (1987) Personal communication with Matt Lorber on
February 2, 1987 [Results of Dougherty Plains Field Evaluation
Project]
Cohen, S.Z.; Creeger, S.M. ; Carsel, R.F. ; Enfiel, C.G. (1984)
Potential Pesticide Contamination of Groundwater from Agri-
cultural Uses, in Treatment and Disposal of Pesticide Wastes,
ACS Symposium Series f259, R.F. Krueger and J.N. Seiber, ed. ,
American Chemical Society, -Washington, D.C-
Cope, R.W. and Romine, R.R. (1973) TEMIK 10G Aldicarb Pesticide
Results of Aldicarb Ingestion and Exposure Studies with Humans
and Results of Monitoring Human Exposure in Working Environ- '
ments, (unpublished study conducted by Union Carbide
Corporation, dated April 17, Project No. 111A13 116A16, File
No. 18269).
Department of Environmental Regulations, Florida (DER) (1984)
Summary of Florida Aldicarb Studies, DER, 2600 Blairstone
Road, Tallahassee, FL 32301, August.
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V-2
Dernehl, C.U. and Block, J.B. (1971) Ingestion of Aldicarb by
Human Volunteers: A Controlled Study of the Effects of Aldicarb
on Man, (unpublished study conducted by Union Carbide Corp.
and presented in an Application for Registration of TEMIK 10G
Aldicarb Pesticide on Ornamental Plants, dated April 1971.)
Environmental Protection Agency (1984) Requirements for
Interim Registration of Pesticides Containing Aldicarb as the
Active Ingredient (Registration Standard prepared by the
Office of Pesticide Programs, March 30).
Environmental Protection Agency (1987) Pesticides in Ground
Water - Proposed Strategic Plan (prepared by the Office of
Pesticides and Toxic Substances, dated June 30).
Fiore, M.C. ; Anderson, H.A.; Hong, R.; Golubjatnikov, R.;
Seiser, J.E. ; Nordstrom, D. ; Hanrahan, L. ; and Bel luck, D.
(1986) Chronic Exposure to Aldicarb-Contaminated Groundwater
and Human Immune Function, Environmental Research 41: 633-645.
Goldman, L. and Jackson, R. (1986) letter to Dr. J.M. Witt of
the California Department of Health Services, dated September
4, 1986, discussing the Summer 1985 watermelon incident in
California, with attachments.
Graham, J.A. (1984) letter sent in response to the Aldicarb PD 1,
dated August 24, 1984, [Preliminary Report, Aldicarb Ground
Water Survey Pilot Project, Winter Spring 1982-83] (unpublished
report prepared by Pesticide Section, Food and Drug Protection
Division, North Carolina Department of Agriculture.)
Heath, R.C. (1984) Ground Water Regions of the United States,
United States Geological Survey, Water Supply Paper 2242.
Inman, R.C. (1986) Personal communication to Matt Lorber on
October 1, 1986, [Florida DACS Monitoring Program].
Lemley, A.T. and Zhong, W.Z. (1984) Hydrolysis of Aldicarb,
Aldicarb Sulfoxide, and Aldicarb Sulfone at Parts per Billion
Levels in Aqueous Mediums, J. Agric. Food Chem. 32: 714-719.
Lorber, M.N. and C.K. Offutt (1986) A Method for the Assessment
of Ground Water Contamination Potential; Using a Pesticide Root
Zone Model (PRZM) for the Unsaturated Zone, in Evaluation of
of Pesticides in Ground Water, ACS Symposium Series t315,
W.Y. Garner, R.C. Honeycutt, and H.N. Nigg, ed. , American
Chemical Society, Washington, D.C.
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V-3
Marti, G.E.; Magruder,L.; Patrick, K.; Vail, M.; Scnuette, W. ;
Keller, R. ; Muirhead, K.; Koran, P.; and Grainick, H.R. (1985)
Normal Human Blood Density Gradient Lymphocyte Subset Analysis:
I. An Interlaboratory Flow Cytometric comparison of 85 Normal
Adults, Amer. J. Hematol. 20: 41
Miles, C.J. and Delfino, J.J. (1985) Fate of Aldicarb, Aldicarb
Sulfoxide, and Aldicarb Sulfone in Floridan Groundwater, J.
Agric. Food Chem. 33: 455-460.
Miller, W.L.; Davidson, J.M.; Foran, J.A.; and Moye, H.A. (1984)
The Florida Temik Study - Ground Water Monitoring, Contract No.
CR811606, P. Arberg, Contract Officer, USEPA, EMSL/ORD, Las
Vegas, NV.
Noren, S.E.; Lorber, M.N.; and Cohen, S.Z. (1986) Aldicarb
Ground-Water Vulnerability Assessment, dated April 9
(unpublished report prepared by the Exposure Assessment
Branch, Hazard Evaluation Division, Office of Pesticide
Programs, EPA).
Ou, L.K.; Edvardsson, S.V.; and Rao, P.S. (1985a) Aerobic and
Anaerobic Degradation of Aldicarb in Soils, J. Agric. and Food
Chem. 33: 72-78.
Ou, L.K.; Edvardsson, S.V.; Thomas, J.E. and Rao, P.S. (1985b)
Aerobic and Anaerobic Degradation of Aldicarb Sulfone in
Soils, J. Agric. and Food Chem. 33: 545-548.
Porter, K.S.; Lemley, A.T.; Hughes, H.B.; Jones, R.L. (1986)
Developing Information on Aldicarb Levels in Long Island
Ground Water (unpublished study submitted by Union Carbide
Agricultural Products Company, Inc.)
Rhode Island Department of Health (1985) Report of Private Well
Testing Program for Pesticides, (Joint study between U.S.
Geological Survey and the Rhode Island Department of Health,
Office of Community Health Services/Health Engineering.)
Sylva, S.R.; Schumacher, A.; Walker, B.; Hoyte, J.S. (1985)
Summary Report: Interagency Pesticide Monitoring Program, (un-
published study submitted by the Massachusetts Department of
Food and Agriculture.)
Union Carbide (1983) Temik Aldicarb Pesticide: A Scientific
Assessment, (unpublished study submitted by Union Carbide,
received by EPA on October 4, 1984, part of comments sent in
response to PD 1).
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V-4
Union Carbide (1984) Aldicarb and Aldoxycarb Field Dissipation
Studies During 1982-1984 (unpublished study submitted by Union
Carbide Agricultural Chemicals Company, no submission number.)
Union Carbide (1985) Letter sent to F. Sanders, dated Mar. 19,
1985, [Latest Tabulated Results of Aldicarb Well Water
Monitoring in Del Norte County, CA; also included portions of
an unpublished report entitled, Control of Pesticide
Discharges to North Coast Waters] (Union Carbide
Correspondance Number 123-85.)
Union Carbide (1985a) Letter sent to M. Branagan, dated August
27, 1985 [Aldicarb Drinking Water Monitoring Results - Maine]
(Union Carbide Correspondance Number 391-85.)
Union Carbide (1985b) Letter sent to M. Branagan, dated August
13, [Florida Aldicarb Test Well Monitoring Results, June 1985]
(Union Carbide Correspondance Number 375-85.)
Union Carbide (1986) Letter sent to M. Branagan, dated January
27, 1986 [Joint Analysis of Well Samples with Wisconsin
Department of Natural Resouces] (Union Carbide Correspondance
Number 628-86.)
Union Carbide (1987a) Aldicarb Foodborne Residue Toxicity Study
in Monkeys - Bananas. (Unpublished study submitted by Union
Carbide Agricultural Products Company, Inc., MRID 40065501).
Union Carbide (1987b) Aldicarb Foodborne Residue Toxicity Study
in Monkeys - Watermelons. (Unpublished study submitted by
Union Carbide Agricultural Products Company, Inc., MRID
40065502).
Varma, A.O.; Zaki, M.H.; Sternman, A.B. (198?) Agricultural
Pesticides: Results of a Preliminary Study (unpublished study
conducted by the Suffolk County Department of Health Sevices).
Whitlock, N.H. ; Schuman, S.H.; Loadholt, C.B. (1982)
Epidemiologic Survey of Potential Acute Health Effects of
Aldicarb in Drinking Water - Suffolk County, NY (unpublished
study conducted by the South Carolina Pesticide Hazard
Assessment Program Center, Medical University of South
Carolina, dated January 6).
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APPENDIX I
LIST OF REBUTTORS TO PD 1
1 Murray, Murray Groves, Inc.
2 Weires, N.Y. Agri. Experiment Station
3 Corban, Miss Coop Extension Service
4 Reinking, Dennison's Mid Valley Chemical
5 McDaniel, A.R. Coop Extension Service
6 Floyd, U.D. Floyd Farms
7 Mason, A.R. Coop Extension Service
8 Jordan, Jordan & Jordan, Inc.
9 Worley, Univ. of Georgia
10 Phillips, Certifine Fruit Co.
11 Ghidiu, Rutgers Coop Extension Service
12 Stuckey, Univ of KY Coop Extension Service
13 Davis, Heart of GA Peanut & Gin Co.
14 Adkinson, Private Individual
15 Johnston, Rutgers Coop Extension Service
16 Smith, Texas Agri. Extension Serv.
17 Mitchener, Mitchener Farms
18 Chapin, Clemson Coop Extension Service
19 Enns, Private Individual
20 Phillips, J.L. Phillips Farms
21 Langlois, Rutgers Coop Extension Service
22 Nabors, Miss Coop Extension Service
23 Craven, Univ. Of GA Coop Extension Service
24 Boaman, Natural Resource Ecology Lab.
25 Averre, Nc Agri. Extension Service
26 McKinley, Southern Agri. Insceticides, Inc.
27 Willingham, J.E.Willingham, Jr, esq.
28 Snapp, G&P Seed Co.
29 Striche, Striche Farms
30 Spilsbury, Wilbur-Ellis Co.
31 Bell, FL Fertilizer Co.
32 Annon.
33 Steflick, Steflik Farms, Inc.
34 Haskett, Asgrow Florida Co.
35 Pustejovsky, Private Individual
36 Eich, AL Coop. Extens. Service
37 Timmer, Univ. of FL
38 Albers, NY Coop. Extens. Service
39 Roe, Wm. G. Roe & CO., Inc.
40 Zipperer, GA Coop. Extens. Serv.
41 Dunaway, pixie Bonded Warehouse & Grain Co.
42 Wilson, Southwestern Peanut Grower's Assn.
43 Lee, TX Agric. Extens. Serv.
44 Miner, Soilserv, inc.
45 Icardo, I & I Farms, Inc.
46 Bagent, LA Coop. Extens. Service
47 Harper, Wilbur-Ellis Co.
48 Pavelski, Pavelski Farms, Inc.
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49 Amalgamated Sugar Co.
50 Sump, Puregro Co.
51 O'Neal, NC Agric. Extens. Service
52 Chalfant, Univ. of GA
53 Rutkowski, NY Coop. Extens. Service
54 Reed, Univ. of AK Agric. Exper. Station
55 Deeter, J.R. Simplet Co.
56 Thomas, NM Univ. College of Agr. & Home Econ.
57 Aitken, Gorsuch & Alverson, Clemson Univ.
58 Bovee, Rio Farms, Inc.
59 Evans, Wilbur/Ellis Co.
60 Mahany, Steuben County Potato Growers Assn.
61 Hirrel, Univ. of AK Div. of Agric.
62 Dilbeck, St. Johns County Coop Exten. Serv.
63 Lloyd, Wilbur/Ellis Co.
64 Vanvranken, Rutgers Univ. Coop. Exten. Serv.
65 MacNeil, Cornell Univ. Coop. Exten. Serv.
66 Rakich, AZ Agric. Chem. Assn.
67 Edsall, R.S. Edsall Co.
68 Small, NC State Univ.
69 Sibbett, Univ. of CA Coop. Exten.
70 Semtner, VA Poly. Inst. & State Univ.
71 Samulis, Rutgers Univ.
72 Cheshire, Univ. of GA Coll. of Agric.
73 Tregaskes, AZ Agrochemical Co.
74 Baldwin, Commonwealth of VA
75 Schwartz, CO State Univ.
76 Diem, VA Coop. Exten. Serv.
77 Burns, Z.V. Pate, Inc.
78 Summers, Golden Kernal Pecan Co.
79 Roman, Univ. of Idaho Coop. Exten. Serv.
80 Burris & Rogers, LA State Univ. Agric. Cntr.
81 Johnson, Walt Johnson
82 Johansen, WA State Univer.
83 Herzog, Univ. of GA
84 Buford, Buford Plantations
85 Trett, F.M. Upton & Sons
86 Minton, USDA
87 Tucker, Univ. of GA Coop. Exten. Serv.
88 Hagenston, Brown & Bryant, Inc.
89 Burch, LA Coop. Exten. Serv.
90 Boykin, W.B. Boykin
91 Obreza, A. Duda & Sons, Inc.
92 James, LA Coop. Extens. Serv.
93 Anderson, The Dune Co. of Imper. Valley
94 Lowder, Lowder Bros. Gin Co.
95 Henninger, Rutgers Univ.
96 Wittmeyer, Ohio State Univ.
97 Boren, Roger Boren, Inc.
98 MOtt, NRDC
99 Lane, McNair Farms
100 Bash, Ohio Farm Bureau Federation
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101 Gonzales, The Fertilizer Place
102 Winstead, None
103 Marley, Bouldin A. Marley
104 King, King Farms
105 LeBlanc, Nutrite Corp.
106 McCleskey, McCleskey Gin
107 Stone, TX A&M Univ.
108 Sturdivant, Duck Land Planting Co.
109 Jackson, Triangle J. Farms
110 Hudson, Tri-State Chemicals,
111 Owens, Wilbur-Ellis
112 West, West Consulting
113 Overstreet, LA Coop. Exten. Serv.
114 Dutcher, Univ. of GA
115 Probasco, Rutgers Coop. Extens. Serv.
116 Spackman, Univ. of WY Agric. Exten. Serv.
117 Noetzel, Univ. of MN Agric. Exten. Serv.
118 Moore, OK Farm Bureau
119 Pitts, Helena Chemical Co.
120 Dunlap, Arizona Agrochemical Co.
121 Larson, Amalgamated Sugar Co.
122 Raski, Univ. of CA at Davis
123 Jones, R.W. Jones
124 Lamm, NC Agric. Exten. Serv.
125 Bolduc, Conserv. Law Found, of N.E.
126 Shenot, Agway
127 Dickson, Univ. of FL
128 Smilowitz, PA State Univ.
129 Updike, Alcoma Packing Co.
130 Barnes, Barnes FArm
131 Parker, TX Agric. Exten. Serv.
132 Tynes, LA Coop. Exten. Serv.
133 Roberts, Univ. of CA Coop. Exten. Serv.
134 Nelson, IN State Chemist and Seed Commissioner
135 Sims, R. Douglas Sims
136 Cleveland, OK Agric. Chem. Assn.
137 Heiden, H-Four Farms
138 Young, Sandyland Farms
139 Fulford, GA Coop. Exten. Serv.
140 Kantzes, Univ. of MD
141 Wyman, Univ. of Wisconson-Madison
142 Crawford, Univ. of GA
143 Hancock, Helena Chemical Co.
144 Weingartner, Univ. of FL
145 Wright, Univ. of Idaho Coop. Exten. Serv.
146 Harkin, Wisconson Water Resource Cntr.
147 Moore, USDA
148 Hafez, Univ. of Idaho
149 Barnes, Wayne Barnes
150 Pearson, Rainbow Plantation
151 Santo, WA State Univ.
152 Sallstrom, MN Plant Food and Chemicals Assn.
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153 Leiby, PA State Univ. Coop. Exten. Serv.
154 Geiger, Lehigh Valley Potato Growers Assn.
155 Tillinghast, SUNY 6 Cornell
156 Leep, Henry G. Leep
157 Graham, NC Dept of Agric.
158 Bailey, Dixie Ag. Supply
159 Musick, Crop-Card Inc.
160 Bonner, AK Coop. Exten. Serv.
161 Cooper, Nat'l. Food Proc. Assn.
162 Turner, Brooks Turner
163 Johnson, Wes Johnson
164 Huelett, Buddy Huelett
165 Lunceford, Marvin L. Lunceford
166 Kelly, Ohio Potato Growers Assn.
167 Matthews, Matthews Farms
168 Sheffield, Helena Chemical Co.
169 Benedict, TX A&M Univ.
170 Mosley, Southern Farmers Assn.
171 Whitehead, Valley Chemical Co.
172 French, TX A&l Univ. citrus Cntr.
173 Thomason, Univ. of CA
174 Raley, Rodney Raley
175 Walden, Enoy Walden
176 Schultz, Commonwealth of VA
177 Lonergan, George L. Lonergan
178 Morgan & Mccarty, MS State Univ.
179 Baughman, Barbara Baughman
180 Dawson, Wisconson Dept. of Justice
181 O»Toole, Union Oil Co.
182 Curswell, Bill Curswell
183 Stuart et al., Red River Co-op.
184 Datt, Amer. Farm Bureau Fed.
185 Harte, Chandler Harte
186 Besadny, State of Wisconson
187 Shiels, Shiels Farms
188 Legates, NC State Univ.
189 Marley, Chritian T. Marley
190 Yandell, West End Planting Co.
191 Johnston, CA Dept. of Food & Agric.
192 McKeown, James P. McKeown
193 Lynn, Grower Service Corp.
194 Myrick, AL Farm Bureau Fed.
195 Hancock, Diamond R Fertilizer Co.
196 Graustein et al., Univ. of Deleware
197 Long, Michigan State Coop. Exten. Serv.
198 O'Tuel, E.M. O'Tuel Cotton Co.
199 Arnold, Professional Agricultural Serv.
200 Zimpel, T.H. Agri-Chemicals
201 Conrad, Estes Chemicals
202 Lambert, GA Coop. Exten. Serv.
203 Sawyer, NC Agric. Exten. Serv.
204 Williamson, Don Williamson
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205 Reilly, VPI
206 Komm, VA Coop. Ext en. Serv.
207 Tugwell, Univ. of Ark.
208 Moore, VA Farm Bureau Fed.
209 Houston, W.H. Houston & Son
210 Murphy. Indian Sun Groves
211 Myrick, Ala. Farm Bureau Fed.
212 Griffiths, Harry J. Griffths
213 Lawson, Lawson Farms
214 Youngker, Chas. Youngker & Son Farms Co.
215 Johnson, Melvin Johnson
216 Walther, L. Walther & Sons
217 Mohr, Rutgers Coop. Exten. Serv.
218 Hofmaster. Commonwealth of VA
219 Crawford, Crawford Farms
220 Orr, USDA
221 Balch, AL Coop. Exten. Serv.
222 Simpson, John Langford Inc.
223 Griffin, NC Agric. Exten. Serv.
224 James, Ruben Earl James
225 Bateman, NC Agric. Exten. Serv.
226 Paul, Carolina Eastern Inc.
227 Price, Bruce G. Price
228 Graugnard, LA Farm Bureau Fed.
229 Lee, Neil C. Lee
230 Child, Childstock Farms
231 Parker, Harris Farms
232 Ausman, State of Wisconsin
233 Flowers, Delta Council
234 Sayers, Asgrow Seed Company
235 Munter, Wm. Gehring Inc.
236 Harkin, WI Water Resource Center
237 Lentz, Univ. of Tenn
238 Williams, Western Growers Chem.
239 Quick, PureGro
240 Irwin, Agvise
241 Lanier, Growers Supply
242 Lovell, Union Carbide (6 vols.)
243 Sears, Nat. Cotton Council
244 Bourret, Wyoming Farm Bureau
245 Smith, NC Dept. of Agriculture
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APPENDIX II
STATE PESTICIDE GROUND WATER MANAGEMENT PLAN FOR ALDICARB
A. BACKGROUND
The general concept of a State Pesticide Ground Water
Management Plan (Management Plan) is presented in the Agency's
proposed strategy to address the pesticides in ground water
concern. The proposed strategy was released for public review
and comment on February 26, 1988 and is available through the
Agency's Public Information Center at (703) 382-2080.
In releasing its proposed strategy to address the pesticides
in ground water concern, the Agency is particularly interested in
receiving public comment on the general concept of a Management
Plan. To facilitate such input, the Agency is planning a series
of workshops beginning in the summer of 1988 to explore with
state agencies and others the Management Plan concept including
appropriate components and emphasis of such plans and the degree
of oversight that the Agency should have in their development and
implementation.
There is a range of approaches that the Agency could use as
guidance to the states in developing their Management Plans. At
one end of the range would be an approach whereby the Agency
establishes an environmental performance standard (i.e., the
Maximum Contaminant Level or Health Advisory level) for each
pesticide, but allows each state the flexibility to decide which
management measures it will utilize to meet that goal.
The other end of the range would be for the Agency to
establish detailed specifications for state management plans
including required adoption of certain.
There are a number of possible approaches between the above
two extremes. The Agency could establish environmental perform-
ance standards and then provide a basic framework for state
Management Plans which would allow a state some flexibility in
deciding the specific pesticide management measures needed to
meet the standard. Which aspects of a Management Plan would be
flexible, and to what degree, provides the variety of approaches
that the Agency can consider in developing guidance for the
states.
At this time, the Agency is generally of the opinion that it
should follow some middle path that establishes an environmental
performance standard but allows some degree of flexibility for
States to determine the specifics of their Management Plans. The
Agency believes that there are likely to be several valid state
Management Plan approaches and that flexibility will be needed
for states to tailor management measures to specific local ground
water protection needs. The Agency requests comments on this
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ii-2
approach, and requests discussion on whether it is preferred over
either the performance standard or specified plan approaches.
A state's Management Plan should be a comprehensive
description of a state's strategy for managing the use of a
pesticide(s) for the purpose of protecting the ground water
resource. To be consistent with the goal of the Agency's
proposed strategy, a state's Management Plan should pay specific
attention to preventing contamination of current and potential
drinking water supplies.
In general, a Management Plan should: 1) describe the
state's overall philosophy and approach to protecting its ground
waters from pesticide contamination, 2) identify a state's
capabilities and authorities in implementing the plan, 3)
identify the location of all ground water that is currently and
could potentially be a source of drinking water in the future or
that is of ecological importance, 4) contain a monitoring scheme
designed to ensure the effectiveness of the Management Plan and
flag contamination problems resulting from misuse/accident, 5)
establish contingency plans to deal with contaminated ground
water, 6) in cases where contamination occurs above the specified
level, describe the mechanisms to be used to reduce contam-
ination, including the source of funding and, 7) describe how the
public is kept informed and can become involved. The plan should
also set forth the state's enforcement authorities and capabil-
ities which can be used to assure compliance with the provisions
of the plan. The Agency requests comment on whether these are
the appropriate components of a plan as well as the appropriate-
ness of the description of information to be included in each of
the components.
Many of the Management Plan components presented above were
derived from discussions at a workshop held during the summer of
1987 to review an earlier draft of the Agency's proposed strategy
to address the pesticides in ground water concern. The workshop
had representatives from other federal agencies and state
agencies as well as from agricultural and environmental interest
groups. These participants provided the Agency with specific
recommendations on possible Management Plan components.
The Agency realizes that there could be much variation among
state plans to account not only for differing state conditions
but also varying state approaches. The Agency will be flexible
in its review of the various state plans, recognizing that
different approaches can be used to obtain the same goal (i.e.,
preventing contamination or reducing the likelihood of a pest-
icide in ground water reaching an Agency-designated level).
States may also elect to work collectively in developing various
components of a plan; however, each state will be responsible for
the development of its own plan.
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A state's Management Plan may have to include a chemical-
specific part, as well as a more generic part that deals with all
pesticides which are of ground water concern. The generic part
of the plan would set forth the basics for implementing a plan
which could be used for any pesticide. The chemical-specific
parts of such a plan would include those portions of the plan
that are specific to a particular pesticide, such as monitoring
designs to ensure compliance with an Agency-designated levels,
identifying specific areas where a certain pesticide is used,
etc.
B. RELATIONSHIP BETWEEN MANAGEMENT PLANS AND OTHER AGENCY/STATE
WATER QUALITY EFFORTS
There are a number of Agency and state drinking water and
water quality programs that can impinge upon or be used to
address various aspects of the pesticides in ground water
concern. Under the Safe Drinking Water Act (SDWA), the Agency is
providing guidance to the states on wellhead protection programs
which are aimed at managing potential sources of ground water
contamination in identified areas around public water wells. The
Agency is also examining possible future SDWA regulations that
will involve the states in controlling Class V injection wells
which could include agricultural drainage wells.
Under the Clean Water Act and more recently, the Water
Quality Act of 1987, the Agency is developing guidance to the
states for implementation of various sections of these acts.
Each state is to develop a State Clean Water Strategy that will
set the overall direction of a state's efforts to address water
quality protection efforts. Specific guidance has been developed
for a state's efforts to address nonpoint source problems with
consideration given to ground water concerns. Under these acts,
most states have also been given support by the Agency to develop
overall ground water protection strategies.
It is the Agency's intent that a state's efforts to develop
a Management Plan to address pesticides in ground water concerns
be coordinated with the above water quality efforts. The Agency
will be taking steps to ensure that consistent guidance is
provided to the states through these various efforts. It is
expected that a state's Management Plan will show how it is
specifically being coordinated with these various strategies and
programs.
C. COMPONENTS OF MANAGEMENT PLANS TO SUPPORT ALDICARB
REGISTRATION
The following constitutes the components of a Management
Plan that will likely be necessary to support the continued
registration of aldicarb in a state or county designated by the
Agency as requiring a Management Plan. Possible aldicarb-
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specific parts of the plan are identified as such; otherwise, the
following guidance relates to the generic Management Plan.
Again, the Agency is seeking comment and discussion on these
components, the need for additional components and the emphasis
that should be given to each in a Management Plan.
1. STATE LEAD AGENCY
The governor should designate a state lead agency to serve
as the contact with the Agency for all matters regarding the
Management Plan. The lead agency will also function as the
coordinator of all agencies within the state involved in carrying
out the functions of the plan. The Management Plan should
identify the agencies involved, contain a discussion of their
respective responsibilities and functions, and contain a
discussion of the mechanisms for assuring coordination of
functions among state agencies.
2. LEGAL AUTHORITY/TECHNICAL EXPERTISE
The plan will describe the general capability of the state
to implement the plan successfully. Included in this description
shall be the legal authorities available to the state with cita-
tion to and copies of the relevant state laws and regulations, a
description of the technical expertise available, and a projec-
tion of the level of resources the state intends to commit to
carry out the Management Plan. The plan must at a minimum demon-
strate the state's authority to: 1) conduct or to require others
to conduct monitoring, 2) supply or require others to supply
alternate sources of water, 3) close wells, 4) impose civil and
criminal penalties for misuse and 5) enforce other relevant
authorities. The Agency is soliciting comments on whether a
Management Plan should be approved without these authorities or
whether additional authorities are necessary.
3. MAPS
The Management Plan will ultimately contain maps for all
areas within the state. These maps will be used in assessing the
vulnerability to contamination in an area (see below). A
suggested set of maps include the following:
1) Soil maps which describe: soil type (e.g., sand, loam,
silt clay loam, etc.), organic matter variations. Soil Conserv-
ation Service runoff classification (i.e., A, B, C, or D).
2) Identification of areas where ground water is a current or
potential drinking water source and identification of high use
and/or high value ground waters, including any wellhead pro-
tection areas or zones or waters of ecological importance.
[States will provide definitions and criteria used to identify
the various types of waters.]
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3) Depth from soil surface to ground waters.
4) Identification of recharge areas.
5) Isopleth maps of recharge including artificial recharge
(e.g., irrigation).
6) Identification of agricultural areas including specific
crop identification or more general agricultural delineations
(e.g., pasture, vegetable crops, grain, etc.).
Aldicarb-specific part of the Management Plan; The
Management Plan will contain maps for all areas (counties or sub-
counties) where aldicarb is normally used and on what crops, the
vulnerability of those different locations, and the use and value
of ground water that may be affected. The Agency is soliciting
public comment on whether it is reasonable for states to develop
aldicarb-specific maps within the time period (two years) that
the Management Plan is developed and accepted and, if not, what a
reasonable time would be for development of these maps.
The Agency has, in this document, classified various states
or counties into three categories of likelihood for ground water
contamination by aldicarb (i.e., high, medium and low). Under
Option 4, proposing a means of regulating the use of aldicarb to
prevent ground water contamination, states should initially adopt
the Agency's ratings for vulnerability. These areas may be
further delineated by applying the Agency criteria to more
specific areas. (The Agency criteria are summarized in the
Aldicarb Technical Support Document.) Refinement of vulner-
ability areas may be made using the suggested maps described in
the generic part of the plan. If an area is placed into a lower
category (from high to medium or medium to low), the state will
be required to provide a justification for the change. The
Agency will review the rating and justification and inform the
state of its decision regarding the change. The Agency is
soliciting public comment on the mechanism described above that a
state must follow for changing an area's vulnerability rating.
4. GROUND WATER CONTAMINATION PREVENTION MEASURES
Aldicarb-specific part of the Management Plan; States will
be required to define specific preventive measures which will, at
a minimum, prevent or reduce any reasonable likelihood of
unacceptable contamination of ground water that is a current or
potential drinking water source. It will be incumbent on the
state not to only identify these specific measures but also to
justify why such measures are believed adequate. The state, in
developing these measures, should consider the capability of the
user in identifying the criteria (i.e., if use is limited to
areas where ground water is at least a specified depth, the plan
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must contain an explanation as to why it is reasonable to assume
that users will know that ground water is at least the specified
depth, that users are likely to follow such a limitation, and an
explanation as to why contamination is not expected to result to
ground water at this depth). Specific measures which may be
imposed, alone or in combination, include:
1) cancellation of use or moratoriums,
2) reduction in the rate of use,
3) more stringent well setback restrictions (a 300 foot set-
back for drinking water wells is being proposed as a national
preventive measure to reduce the potential for contamination),
4) application method limitations,
5) application time of year restriction,
6) wellhead protection of public drinking water,
7) rules on disposal of excess product/unused spray mix/
containers,
8) mixing/loading requirements,
9) changes in agronomic practices (e.g., tilling),
10) permit or advance notice program (if used, identify
criteria for issuing permits or denying use),
11) user education/training, (One of the best defenses in
the protection of ground water is to educate the pesticide
applicator of the problem and provide training on measures
to employ in avoiding contamination. User education/
training heightens the user's awareness to the problem and
the extent of training applicators will be required to
take.), and
12) use restrictions on a farm-specific basis, i.e., restrict
use if farm conditions such as soil type, depth to ground water,
or other hydrogeologic parameters exceed specified limits.
The measures for prevention of contamination should be most
stringent in the most susceptible areas (i.e., those areas where
vulnerability is the greatest) and those areas where the ground
water is most important as a resource.
The plan should provide that the Management Plan's
prevention measures could be modified if it is obvious, based on
experience and/or monitoring results, that such measures are not
providing adequate protection.
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State measures must, at a minimum, provide reasonable
confidence of preventing or reducing the likelihood of aldicarb
contamination reaching the Health Advisory level of 10 ppb in
ground water.
5. RELAYING USE INFORMATION
The Management Plan shall have a detailed discussion of how
information regarding use restrictions/precautions will be
relayed to users. Such discussion should include not only the
form but also the distribution methods. The enforceability of
imposing requirements under this approach should also be
addressed.
6. ENFORCEMENT
The plan should describe the state's enforcement capabil-
ities and authorities in terms of assuring compliance with the
measures imposed to protect ground water from contamination and
in terms of response actions where contamination has already
occurred. Both civil and criminal enforcement authority should
be available to the state under the Management Plan.
7. MONITORING
States must establish a comprehensive monitoring program
which will be statistically designed to evaluate the impact of
use of a pesticide, identified as posing a threat to ground water
contamination. Many monitoring designs are possible and each
Management Plan must provide justification for the design chosen.
In general, acceptable designs would contain the following
objectives and features:
1) The majority of monitoring will occur in areas of most
concern based on hydrogeologic vulnerability and
pesticide use patterns; some sampling should also occur
in areas of less concern.
2) The design should be stratified on use and hydro-
geologic vulnerability in the sense that smaller
areas monitored will be statistically representative of
larger areas similar in hydrogeology and use patterns.
3) Monitoring must be focussed on the quality of the
ground waters that are a current as well as potential
drinking water source. This important objective
often will require the implementation of new monitor-
ing wells, or use of existing high quality wells of
known attributes, such as USGS monitoring wells.
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4) Monitoring designs must contain a quality assurance
program, including participation by the state. The
state role could include, for example, participation
in sample collection and shipment, analytical quality
control including use of an independent state-appointed
laboratory, additional monitoring, etc.
Aldicarb-specific part of the Management Plan: The
following type of information should be included in the plan:
1) the number of wells to be sampled,
2) selection criteria for the wells,
3) statistical evaluation of the sensitivity of the
monitoring plan,
4) identification of the analytical method(s) used
to analyze samples, and
5) frequency of monitoring.
The Agency acknowledges that there two means to require
monitoring for contamination of ground water by aldicarb. One is
to impose the monitoring program, including the program design,
implementation, and cost, on the registrant, as a condition of
registration. The other is to impose this as a requirement of
the state as part of the Management Plan. The Agency is
soliciting comment on the merits of either approach.
8. ACTION IN RESPONSE TO GROUND WATER CONTAMINATION
The Management Plan will specify what measures will be
implemented to ensure that the Agency-designated level (in most
cases the Maximum Contaminant Level or Health Advisory) will not
be reached once ground water contamination is detected in ground
water that is a current or potential drinking water source and,
if this level is reached or exceeded, how the state will prevent
contaminated ground water from being used as a source of drinking
water.
The plan shall specify whose responsibility it will be to
identify how the contamination occurred, to rectify the contam-
ination problem when a specific level is reached, and, when
necessary, to provide (fund) an interim source of drinking
water.
Specifically, the plan must describe the steps that will be
taken to identify, if possible, the source of contamination and,
if possible, to ascertain whether use was in accordance with
label directions and other requirements and the contamination
resulted from normal use, leaching and subsequent ground water
contamination; or whether ground water contamination resulted
from misuse or accident (e.g., spillage). The plan shall also
specify the means which will be employed in reducing pesticide
contamination of ground water to acceptable levels when the
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specified level (Maximum Contaminant Level or Health Advisory) is
exceeded and for providing an interim drinking water source for
contaminated wells.
It is the responsibility of a state under its Management
Plan not only to protect ground water from contamination within
its boundaries but also to mitigate contamination of a source of
drinking water in another state. It may therefore be necessary
for states to inform one another when applications are made in
bordering counties where ground water moves across state
boundaries. In those cases where it can be clearly demonstrated
that ground water contamination above the specified level
occurred as a result of application/accident from a neighboring
state, it will be the responsibility of the state in which the
pesticide use occurred to ensure that corrective action is taken.
Aldicarb-specific part of the Management Plan: In accord-
ance with the generic part of the Management Plan, the plan will
designate the Health Advisory level for aldicarb (10 ppb) as the
maximum level of contamination which will be allowed in ground
water that is a current or potential drinking water source.
Because the level of detection (1 ppb) is so close to the level
of protection, the problem identification and response program
will be initiated when any level above 1 ppb is identified.
9. PUBLIC PARTICIPATION
The Management Plan should provide detail how the public
will be informed of significant findings and important regulatory
actions under the plan. The plan should also address the public
role regarding decision making under a state plan.
10. RECORDS/RECORDKEEPING
The state plan shall include a provision to maintain
Management Plan records on monitoring efforts, including sample
analysis, issuance of permits, etc., and the types and number of
enforcement actions, site-specific regulatory actions,
administrative action, etc. Such records shall be maintained for
a minimum of five years and be made available to the Agency upon
request. An annual report shall be sent to the Agency
Headquarters through the Agency Regional Office.
The plan will require that all findings through monitoring
will be reported immediately to Agency. The plan will also
include a provision that the Agency will be notified on a semi-
annual basis of the results of all routine monitoring.
Aldicarb-specific part of the Management Plan: The Agency
shall be notified immediately of all positive findings of
aldicarb in ground water. Included in the notification will be
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the level of contamination, county of occurrence, and the
measures implemented to curtail further contamination.
11. TIMEFRAME FOR IMPLEMENTATION
Those states desiring to maintain use of aldicarb within
their state will be required to have an Agency-approved
Management Plan within two years.
12. AGENCY OVERSIGHT
The Agency will approve a Management Plan (both generic and
pesticide-specific parts) submitted by any state, or any
modification thereof, if such plan 1) demonstrates a practical
approach to managing the use of a pesticide for the purpose of
protecting ground water from contamination, and specifically
making reasonably sure that no one is exposed to aldicarb
residues in ground water at levels greater than 10 ppb, 2)
contains satisfactory assurances that the state lead agency has
or will have the legal authority and qualified personnel
necessary to carry out the Management Plan, 3) gives satisfactory
assurances that the state will devote adequate funds to the
administration of the plan, and 4) provides that the state will
make reports available as required. Conversely, the Agency may
reject a Management Plan if the Management Plan does not meet the
standards described above.
The Agency's approval of the Management Plan may be
withdrawn at any time that it is determined that the state is not
properly administering the Management Plan in accordance with its
provisions. The Agency will inform the state of its intention to
withdraw its approval of the plan and provide the state the
opportunity to institute corrective actions. If after a
reasonable period, not to exceed 90 days, such action has not
been instituted, the state will be notified that the Agency's
approval of the plan has been withdrawn.
*U. S. GOVERNMENT PRINTING OrFICE J1988-516-002180133
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