United States
Environmental Protection
Agency
Office of
Pesticides and Toxic Substances
Washington, DC 20460
October 1984
Pesticides
s>EF¥V
Dicofol
Special Review Position
Document 2/ 3
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DICOFOL POSITION DOCUMENT 2/3
Office of Pesticide Programs
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
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EXECUTIVE SUMMARY
This Position Document 2/3 (PD 2/3) describes regulatory
actions to reduce the potential adverse environmental effects
from registered uses of dicofol. The proposed action is
based on the Agency's determination that uses of dicofol con-
taminated with DDT and related compounds (collectively referred
to as DDTr) will result in unreasonable adverse effects to non-
target wildlife, especially endangered species. The "Guidance
Document for the Reregistration of Pesticide Products Containing
Dicofol as an Active Ingredient," issued by the Agency in
December, 1983, described the Agency's concerns in detail and
also set forth data and labeling requirements for continued
registration of dicofol. A Special Review was initiated by
the Agency on March 21, 1984, (49 FR 10569) and invited
comments from the registrants as well as from the public.
The comments received durinq the 45-day comment period were
from the registrants, environmental groups, and agricultural
cooperative agents. All of the comments were reviewed for
pertinent information.
The Agency's determination of unreasonable adverse effects
is based on weighing the risks and benefits of dicofol use.
The risk assessment is based in part on models used to determine
the environmental transport and accumulation of these contaminants
in the citrus growing areas of the Arroyo Colorado river basin
and cotton growing areas of Kings County, California. These
models indicated the potential for the DDTr contaminants to
accumulate to levels which cause adverse effects to fish and birds
The determination is also based on the fact that there are
areas of the country in which dicofol usage is high and monitor-
ing data show that DDTr residues are also high in the water
and wildlife inhabiting those areas. The Agency has determined
that the evidence clearly indicates that the use of dicofol
in these areas makes a significant contribution to the ambient
levels of DDTr.
The Agency is also concerned about the potential onco«-
genicity of the DDTr impurities as well as dicofol itself thus,
The Agency is currently reassessing the weight of evidence to
develop appropriate measures of oncogenic potency for the
chemicals so that it can be incorporated into the Agency's
risk assessment. This new assessment should be included in
the Position Document 4 (PD 4).
The annual usage level ranges from 2.0 to 2.5 million
pounds of dicofol active ingredient. The major pesticidal
uses are the applications to citrus and cotton to control
various species of mites. Approximately two-thirds of the
dicofol used in the U.S. is used on these two sites. The
remainder is used on seed crops, stone and pcxtie fruits, figs,
vegetables, small fruits, tree nuts, mint, ornamental plants,
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turf grasses, greenhouse crops
and around domestic dwellings
bui ldings.
, house plants, plus sites in
and commercial and agricultural
The Agency's analysis of the benefits of dicofol use
indicated that, although economic impacts would result from
cancellation, these impacts did not outweigh the risks. An
analysis of the benefits associated with each use reveals
that alternative pesticides are available. Economic impacts
resulting from the cancellation of dicofol will be felt
primarily by cotton producers in the San Joaquin Valley of
California, due mainly to yield reductions. However, these
impacts are not significant at a national level. Economic
impacts to citrus growers from dicofol cancellation would be
due to the use of costlier alternatives. Additional costs
would be realized if there were yield and quality declines
associated with the use of these alternatives. The economic
impacts relating use of dicofol on all minor crops has not
been quantified. Some of these sites may realize negative
economic impacts, the magnitude of which is unknown at this
time. However, alternatives are available for most minor uses
so the impacts should not be significant.
Various options were considered by the Agency to reduce
the potential environmental risks due to the use of dicofol.
One option was to reduce the DDTr levels in dicofol. Lowering
the DDTr contamination in dicofol to the levels suggested by
the registrants would not be adeguate to mitigate the risks
because significant adverse effects are still anticipated to
occur. Another option was to place various restrictions on
dicofol use, i.e., to restrict the use to certain geographic
areas or to reduce the application amounts. The Agency also
concluded that this option would not adequately mitigate the
risks to the environment.
The Agency proposes to cancel all registrations for
dicofol because the risks of continued use outweigh the
benefits. A 30-day comment period, beginning on the date of
the issuance of the Federal Register notice, will allow the
Scientific Advisory Panel and the Secretary of Agriculture
to review and comment on the Agency's proposed decision, and
a 45-day comment period will be given to the registrants, and
the public for review and comment. After analyzing these
comments the Agency will issue a PD 4 containing the Agency's
final decision.
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ACKNOWLEDGEMENTS
Project Team
Edward J
Richard
Kyle R.
W i11i am
Mark H.
Carolyn
Robert K
William
Bruce A.
Joseph C
Maureen
Douglas
Allen
T. Balcomb
Barbehenn
J. Boodee
Glaze
A. Gregorio
Hitch
L. Jordan
Kapner
. Re inert
Smith
Sutherland
Product Manager, RD
Wildlife Biologist,
Science Integration
Chemist, HED
Economist, BUD
Toxicologist, HED
Ecoloqist, HED
Attorney, OGC
Review Manager, RD
Chemist, HED
Attorney, OGC
Entomologist, BUD
HED
Staff, HED
Review Committee
David K. Hanneman
James Holder
John Mason
Suzanne Wells
Compliance Monitorinq Staff
ORD
Compliance Monitorinq Staff
OPPE
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TABLE OF CONTENTS
I. INTRODUCTION 1-1
A. LEGAL BACKGROUND 1-1
1. Regulatory History 1-1
2. Organization of this Position Document 1-1
3. The Special Review Process 1-1
B. CHEMICAL BACKGROUND 1-2
1. Chemical and Physical Characteristics 1-2
2. Registered Uses and Production 1-3
3. Tolerances 1-3
II. ASSESSMENT OF RISK AND ANALYSIS OF REBUTTALS II-l
A. INTRODUCTION II-l
1. Review of DDT Cancellation Decision II-l
2. Ecological Effects of DDT II-2
a. Reproductive Effects in Birds II-3
b. Behavioral Effects on Birds 11-10
c. Effects on Fish Reproduction 11-11
d. Accumulation of DDE in Birds Fed 11-12
Diets Containing Dicofol
3. National Trends in DDTr Residues in Fish 11-13
and Wildlife
a. Fish 11-15
b. Birds 11-15
B. DICOFOL USE AREAS: RESIDUE TRENDS AND POTENTIAL 11-21
EXPOSURE TO SENSITIVE WILDLIFE
1. California 11-21
a. Environmental Residues 11-22
b. Sensitive Wildlife in California 11-38
2. Arizona 11-50
a. Environmental Residues 11-50
b. Sensitive Wildlife in Arizona 11-52
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3. Texas 11-55
a. Environmental Residues 11-55
b. Sensitive Wildlife in South Texas 11-60
4. Florida 11-62
a. Environmental Residues 11-62
b. Sensitive Wildlife in Florida 11-66
C. EXPOSURE ANALYSIS 11-71
1. Introduction 11-71
2. Exposure Analysis for Kings County, 11-71
Cali fornia
a. Kings County Mass Balance Analysis 11-71
b. Results and Conclusion 11-72
3. Aquatic Exposure Analysis for Kings County 11-72
a. Calculation Methodology 11-75
b. Results 11-75
4. Arroyo Colorado Exams Model for Citrus Use 11-76
D. POTENTIAL HUMAN HEALTH EFFECTS 11-79
1. Oncogenicity of DDTr 11-79
2. Human Toxicity of Alternatives to Dicofol 11-79
E. RELATIVE ECOLOGICAL HAZARDS OF DICOFOL 11-84
ALTERNATIVES
F. ANALYSIS OF REBUTTAL COMMENTS 11-87
1. Comments on Exposure 11-87
2. Comments on Risk 11-88
3. Comments on Arroyo Colorado EXAMS Model 11-88
a. Comments Concerning Loading 11-88
b. Agency Response 11-88
c. Comments Concerning Entrapment 11-89
d. Agency Response 11-89
e. Comments Concerning Settlement 11-89
f. Agency Response 11-89
4. Other Comments Received 11-90
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G. SUMMARY OF DICOFOL AND DDTr EFFECTS 11-91
III. BENEFITS SUMMARY FOR DICOFOL III-l
A. INTRODUCTION III-l
B. COTTON II1-4
C. CITRUS II1-6
D. MINOR USES III-8
IV. DEVELOPMENT OF REGULATORY OPTIONS IV-1
A. INTRODUCTION IV-1
B. LEGAL BASIS FOR OPTIONS IV-1
C. DATA GATHERING FOR IDENTIFICATION OF OPTIONS IV-2
1. Additional Data IV-2
2. Information Gathering Hearings IV-2
D. LEGAL OPTIONS AVAILABLE UNDER FIFRA IV-2
1. Classification for Restricted Use IV-3
2. Amend the Terms and Conditions of Regis- IV-3
tration Including Changes in Labeling
3. Summary IV-3
E. REGULATORY OPTIONS FOR DICOFOL IV-3
F. RISK BENEFIT ANALYSIS OF REGULATORY OPTIONS IV-5
1. Cotton Use IV-5
a. Option 1 IV-5
b. Option 2 IV-5
c. Option 3 IV-6
2. Citrus Use IV-7
a. Option 1 IV-7
b. Option 2 IV-7
c. Option 3 IV-8
3. Other Uses IV-8
a. Option 1 IV-8
b. Option 2 IV-9
c. Option 3 IV-9
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G. SUMMARY OF PROPOSED REGULATORY DECISION IV-10
V. BIBLIOGRAPHY V-l
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LIST OF TABLES
Page
DDE and DDTr residues in potential bald
eagle food items in Maine, 1966-1974 II-7
Residues of DDE and DDTr in Atlantic
menhaden regurgitated by brown pelicans
in South Carolina II-8
Eggshell thickness, egg residues and diet-
ary residue exposure in California brown
pelicans (1969-1974) II-9
Comparison of DDTr accumulation in livers
of bobwhite quail fed similar dietary
concentrations of dicofol and DDT 11-14
Historical mean residue levels in starlings
from 14 collection sites that had greater
than 1.0 ppm DDE in the 1979 collection 11-17
Nationwide starling residue geometric means 11-18
DDE residues in duck wings by year and
flyway 11-20
NPMP residues in starlings in California and
U.S., 1967-1979 11-23
Organochlorine residues in starlings at
NPMP sites monitored in 1979 11-24
DDE duck wing residues in California 11-25
DDE in mallard wings - Pacific flyway 11-26
DDTr residues in fish at 2 NPMP stations
in California 11-27
Dicofol use in San Joaquin, Stanislaus,
and Imperial Counties, California, 1970-1983 11-33
DDTr residues in fish fillets at 3 San
Joaquin Valley monitoring stations, 1976-
1983 11-34
Results of regression analysis of DDTr
residue trends in catfish species at 3 San
Joaquin Valley sampling stations, 1976-1983 11-35
DDT homologs in fish collected in routine
sampling 11-36
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Table 11-17
Table 11-18
Table 11-19
Table 11-20
Table 11-21
Results of regression analysis of DDTr trends
for channel catfish and carp at station 37
(New River) and station 38 (Alamo River) 11-37
Table 11-22
Table 11-23
Table 11-24
Table 11-25
Table 11-26
Table 11-27
Table 11-28
Table 11-29
Table 11-30
Analysis of p,p'-DDT as a percentage of
total DDT in channel catfish
Analysis of variance of percent p,p'DDT
in channel catfish at San Juaquin and
Imperial Valley monitoring stations
DDE concentrations in prey species of
California peregrine falcons, 1980
DDE and PCB in eggs of California Peregrine
falcons. Eggs unmatched in the wild or
which did not successfully hatch during
artificial incubation
National Pesticide Monitoring Survey
starling residues at station 4-C-l,
Maricopa County, Arizona
DDE carcass residues in prey species of
peregrine falcons in Arizona
DDE residues in whole fish at NPMP station
16, Mission, Texas
DDE residues in composite samples of blue
catfish and gizzard shad at freshwater sites
in the Arroyo Colorado drainage in 1978
DDTr contamination in dicofol products
sampled in Florida in 1984
Regression statistics for NPMP fish samples
1969-1980, St. Lucie Canal, Florida
Toxicity data base for alternatives to
dicofol
Comparative acute toxicity of dicofol and
its alternatives to certain non-target
organi sms
Comparative chronic toxicity and fish bio-
concentration factor of dicofol and
its alternatives to certain non-target
organi sms
11-39
11-41
11-43
11-45
11-51
11-54
11-58
11-59
11-63
11-64
11-80
11-85
11-86
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LIST OF FIGURES
Page
Figure II-l DDTr residues in freshwater fish 11-16
Figure II-2 Mean DDE residues in starlings in the 4
'high residue' counties in California
1968-1982 11-28
Figure II-3 California pesticide monitoring network
sampling stations 11-30
Figure II-4 DDTr residues in fish fillets at San
Joaguin Valley sampling stations 33,
34, 35. Data plotted are those of
Table 11-15 11-31
Figure II-5 Dicofol use in Kings, Kern, Tulare, and
Ventura Counties, California 11-48
Figure II-6 Geographic range of the California condor 11-49
Figure II-7 Citrus production in Texas in 1981 11-56
Figure II-8 Locations of black skimmer study sites 11-61
Figure II-9 DDE residues in freshwater fish (loglO
transformed) at St. Lucie Canal,
Florida 1969-1980 11-65
Figure 11-10 Lake Apopka, Florida and environs 11-67
Figure 11-11 Peregrine falcon wintering areas 11-70
Figure 11-12 Relative contributions of DDT and dicofol
to the DDTr loading of Kings County,
California 11-73
Figure 11-13 DDTr loading to Kings County with and
without dicofol cancellation (1984-2000) 11-74
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I. INTRODUCTION
A. LEGAL BACKGROUND
1. Regulatory History
The Federal Insecticide, Fungicide, and Rodenticide Act
as amended (FIFRA) and its regulations require the Environmental
Protection Agency (the Agency) to review the risks and benefits
of the uses of pesticides. On March 21, 1984, the Agency
issued a Notice of Special Review (49 FR 10569) of pesticides
containing dicofol. The Agency had determined that registrations
and applications for registration of pesticide products
containing dicofol meet or exceed the risk criteria in 40 CFR
162.11 (a)(3)(ii)(C), which provides that a Special Review
(new name for Rebuttable Presumption Against Registration, RPAR)
shall be conducted if the use of a pesticide "[clan reasonably
be anticipated to result in significant local, regional, or
national population reductions in nontarget organisms, or
fatalities to members of endangered species." The "Guidance
Document for the Reregistration of Pesticide Products Containing
Dicofol as the Active Ingredient" (EPA/540-RS-83-003), issued
December 30, 1983, described the Agency's concerns in detail,
and also sets forth data and labeling reguirements for continued
registration of dicofol.
The Notice of Special Review invited comments from the
registrants as well as from the public. The comment period
lasted 45 days and all comments received were evaluated.
2. Organization of this Position Document
This Position Document 2/3 (PD 2/3) addresses the risks
and benefits of the uses of dicofol. This document contains
four parts. Chapter I is this Introduction. Chapter II
discusses primarily the potential risks of dicofol to wildlife.
It includes descriptions and evaluations of the risk inform-
ation, exposure data, rebuttal submissions and analyses, and
the Agency's risk conclusions. It also addresses the carcino-
genic risk of dicofol products and their DDT related impurities.
Chapter III contains a discussion and quantitative estimate of
the benefits of different dicofol uses, and discusses the
assumptions and limits of these estimates. Chapter IV describes
possible regulatory options to reduce the risks of dicofol, and
evaluates the risks and benefits of these regulatory options,
and summarizes the regulatory actions which the Agency proposes
to take concerning dicofol.
3. The Special Review Process
Issued under FIFRA as amended (7 U.S.C 136-136y), 40 CFR
162.11 provides that a Rebuttable Presumption Against Registration
(RPAR or Special Review) shall be conducted if the Agency
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determines that a pesticide meets or exceeds any of the risk
criteria relating to acute and chronic toxic effects set
forth in 40 CFR 162.11(a)(3). In makinq this determination,
the Agency is guided by section 3(c)(8) of FIFRA which directs
the Agency to begin a Special Review only if it is based on a
"validated test or other significant evidence raising prudent
concerns of unreasonable adverse risk to man or the environment."
If such a determination is made, the registrant(s) will be
notified by certified mail and afforded an opportunity to
submit evidence in rebuttal to the Agency's presumption. Altern-
atively, any registrant may voluntarily petition the Agency
to cancel the registration of its product(s).
Followinq the initiation of the Special Review, the
pesticide use or uses of concern will enter the public
discussions stage of the Special Review process. Registrants
and interested members of the public may submit written
comments, information, or request public discussions on the
Agency's proposed actions and/or other proposals for additional
or alternative actions. Registrants may submit information
indicating that dicofol does not pose a risk to man or the
environment and/or that the benefits exceed the risks associated
with dicofol use. Interested members of the public may submit
information concerning the risks and benefits associated with
the use of dicofol.
If risk issues cannot be resolved through voluntary
actions, the Agency proceeds to evaluate the risks and
benefits of the pesticide and to propose a regulatory solution
in this PD 2/3 and may submit a proposed Notice of Intent to
Cancel to the Scientific Advisory Panel and the Secretary of
Agriculture. After obtaining comments from the Scientific
Advisory Panel, the Secretary of Agriculture, registrants,
and the public on PD 2/3, the Agency would issue a Position
Document 4 (PD 4) supporting the Agency's final regulatory
position, which may include a Notice of Intent to Cancel
pursuant to FIFRA, section 6. If the Agency determines that
the risks of use exceed the benefits, the Agency would
issue a notice of intent to cancel the registration of products
intended for such use. The notice may identify for specific
uses certain changes in the composition, packaging, and/or
labeling of the product which would reduce the risks to
levels that the Agency would consider acceptable. Cancellation
would become effective unless within 30 days of issuance of
the notice, the registrant either requests a hearing to
challenge the cancellation or submits an application to
amend his product's registration in a manner prescribed in
the notice of intent to cancel.
B. CHEMICAL BACKGROUND
1. Chemical and Physical Characteristics
Dicofol is the common name for l,l-bis(p-chlorophenyl)-
2,2,2-trichloro-ethanol. Technical dicofol is a nonflowable
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liquid (or waxy solid) at room temperature. It ranges from
dark brown to yellow brown in color. It is stable under cool
and dry conditions, and is practically insoluble in water,
but readily soluble in most organic solvents. Its melting
point ranges from 58°C to 78°C.
Certain unintentional impurities have been identified in
technical dicofol products which are the result of the
manufacturing process. The identified contaminants of concern
include the p,p' and o,p' isomers of DDT, DDE, DDD (TDE) and
"tetra-chloro" DDT (Cl-DDT). The chemical names for these
contaminants are as follows:
1. l,l-bis-(p-chlorophenyl)-2,2,2-trichloroethane tp,p' DDT]
2. l-(p-chlorophenyl)-l-(o-chlorophenyl-2,2,2-trichloroethane [o,p* DDT]
3. l,l-bis-(p-chlorophenyl)-2,2-dichloroethylene fp,p' DDE]
4. l-(p-chlorophenyl)-l-(o-chlorophenyl)-2,2-dichloroethylene [o,p* DDE]
5. l,l-bis-(p-chlorophenyl)-2,2-dichlonoethane [p,p'DDD]
6. l-(p-chlorophenyl)-l-(o-chlorophenyl)-2,2-dichloroethane [o,p' DDD]
7. l,l-bis-(p-chlorophenyl)-l,2,2,2-tetrachloroethane [p,p' Cl-DDT]
8. l-(p-chlorophenyl)-l-(o-chlorophenyl)-l,2,2,2-
tetrachloroethane [o,p' Cl-DDT]
In this document, the term DDTr will be used to denote
all of these DDT analogs.
2. Registered Uses and Production
The Agency records show registrations for 196 dicofol
products and 86 federally recognized intrastate registrations
of state-registered products. There are three registrants who
are authorized to manufacturer the technical material: Rohm
and Haas Company, Makhteshim-Agan (America), Inc., and Aceto
Chemical Company.
Dicofol was first registered as a pesticide in 1957. It
is used in acaricides to control mites on agricultural crops
and ornamentals and in or around agricultural and domestic
buildings. Over 77 percent of the active ingredient is applied
to five crop groupings: cotton, citrus, dry beans, apples,
and field corn. Approximately ten percent of the dicofol is
applied to ornamentals throughout the country. The remainder
is applied to various minor sites throughout the country.
The active ingredient dicofol is not manufactured
domestically, but is imported. Approximately 2.0 to 2.5
million pounds of the active ingredient is used in the U.S.
annually.
3. Tolerances
Tolerances for residues of dicofol in or on raw agri-
cultural commodities are listed in 40 CFR 180.163 as follows:
30 ppro in or on hops; 25 ppm in or on peppermint hay and
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spearmint hay; 10 ppm in or on apricots, grapefruit, kumquats,
lemons, limes, nectarines, oranges, peaches, tangerines, 5 ppm
in or on apples, beans (dry), snap beans (succulent), lima
beans (succulent), blackberries, bushnuts, butternuts, canta-
loupes, cherries, chestnuts, crabapples, cucumbers, dewberries
(boysenberries and logan berries), eggplant, figs, filberts,
grapes, hazelnuts, hickory nuts, melons, muskmelons, pears,
pecans, peppers, pimentos, plums (fresh plums), pumpkins,
quinces, raspberries, summer squash, strawberries, tomatoes,
walnuts, watermelons, winter squash; and 0.1 ppm in or on
cottonseed.
The Dicofol Guidance Document required additional crop
residue data be developed for dicofol in order to support
existing tolerances for dicofol per se. Because DDT and
related metabolites are impurities present in dicofol, the
Guidance Document required that crop residue data also be
developed on these compounds. These data could be used by
the Agency for further regulatory action on dicofol.
It should be noted that the Agency is in the process of
revoking all existing tolerances for residues of DDT and its
degradation products (DDE, DDD, and Cl-DDT). The Agency is
replacing these tolerances with safe, acceptable residue
limits or "action levels". These action levels are needed
for enforcement purposes to cover the inadvertent residues of
DDT which may be present from the registered uses of dicofol
as well as other sources of DDT contamination. This action is
being taken because DDT was cancelled in 1972, and the current
tolerances may be replaced with lower acceptable residue
action levels. The action level will be based on monitoring
data from numerous crops including beans, cottonseed, sweet
corn, and citrus collected by the Food and Drug Administration
(FDA) during the years 1975-1979. Although these data indicate
that residues of DDT and its degradation products have been
decreasing with time, the actual pesticidal treatment history
of the samples analyzed by FDA is unknown. The proposed
action levels will be based on survelliance of the raw agri-
cultural commodities including those most commonly treated
with dicofol. In the event DDTr is detected above those
action levels in crops treated with dicofol, the Agency
would take appropriate additional regulatory measures at that
t ime.
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II. ASSESSMENT OF RISK AND ANALYSIS OF REBUTTALS
A. INTRODUCTION
This chapter has six parts. The first part reviews the
basic conclusions that have been reached concerning the
hazards of DDT to the environment. These findinqs were first
published in 1972 when the use of DDT was cancelled by the
Agency, and reaffirmed in 1975 after the Agency reviewed the
scientific literature since 1972. The second part discusses
the residue trends of DDT and its related compounds in areas
of high dicofol usage. The potential for exposure to sensitive
species in these areas is also discussed. The third part is
an exposure analysis that uses mathematical models and calcula-
tions to predict the amount of environmental contamination that
might result from the normal use of dicofol. The fourth part
discusses the oncogenicity of dicofol and DDTr, as well as the
toxicology of the alternatives. The fifth part discusses the
relative ecological hazards of dicofol alternatives. The sixth
part of this chapter is an analysis of the rebuttal comments
received by the Aqency from the public and pesticide registrants.
1. Review of Agency Findings in its DDT
Cancellation Decision
When the Agency cancelled DDT (Ruckelshaus, 1972) it
published a series of scientific conclusions regarding the
environmental fate and toxicological effects of the pesticide.
It was determined at that time that the following chemical
properties of DDT exacerbate the potential risk from DDT to
the environment:
° DDT can persist in soils for years and even decades.
0 DDT can persist in aquatic ecosystems for long periods.
0 Because of persistence and other characteristics,
DDT is subject to transport from sites of application.
° DDT can be transported by drift during aerial
applicat ion.
° DDT can vaporize from crops and soils.
° DDT can be attached to eroding soil particles.
° DDT is a contaminant of freshwaters, estuaries
and the open ocean and it is difficult or
impossible to prevent DDT from reaching aquatic
areas and topographically non-adiacent and remote
from the site of application.
The activity of DDT in food chains was determined to represent
an unknown, unquantifiable risk to man and lower organisms because
DDT can be concentrated in and tranferred through terrestrial
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invertebrates, mammals, amphibians, reptiles, birds, freshwater
and marine plankton, insects, molluscs, other invertebrates,
and fish.
The Agency found that DDT can have lethal and adverse
sublethal effects on useful aquatic freshwater invertebrates,
including arthopods and molluscs; that it is toxic to and can
affect the reproductive success of fish. Birds can also mobilize
lethal levels of DDT residues and sublethal levels can cause
chronic problems, i.e., thinning of eggshells and impairment of
reproductive success.
Generally, the Agency concluded that no directions for
use of DDT, even if followed, could over the long run adequately
mitigate DDT's injury to man or other vertebrate animals; that
no warning or caution for use of DDT, even if followed, could
over the long run prevent injury to living man and other verte-
brate animals and useful invertebrate animals; and that use of
DDT in controlled situations in limited amounts might present
less risk than usage in greater amounts, but still would contam-
inate the environment.
At the request of the U.S. Congress the Agency undertook
a review of the scientific evidence on which the cancellation
was based. This review entirely affirmed the scientific judgments
made in the cancellation decision and stated that:
"Voluminous literature published in this area since the
DDT hearings has allowed a more complete picture of DDT's
effects in this area than was available at the time of cancel-
lation. Reproductive, behavioral, lethal, and sublethal effects
on fish and wildlife have been reviewed in detail based on the
additional literature and data. Also, the Agency conducted
intensive onsite field interviews with persons involved in
research on fish and wildlife effects to obtain most recent
data and results as a supplement to the nearly 500 articles
that have been published in this area and reviewed since the
cancellation.
New data were available in the case of most findings on
fish and wildlife effects and none of the findings of the
Agency could be denied on the basis of new data. Certain
adverse behavioral effects on wildlife that were not known in
1972 have been established since that time" (Environmental
Protection Agency, 1975).
2. Ecological Effects of DDT and DDT Analogs
DDE has been the chemical most thoroughly studied for
reproductive effects in wildlife; there is comparatively little
data concerning the potency of DDD to various bird species.
Environmental effects and fate data for Cl-DDT is unavailable,
but the Agency believes that this analog is potentially a DDE
precursor and could lead to adverse effects. Thus, although
the following discussion focuses on DDE, the Agency is
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concerned about all DDT analogs and their potential to result
in adverse effects to wildlife.
a. Reproductive Effects in Birds
Much scientific effort has been directed to documenting
tne accumulation of DDT homologs in the food chains of birds
and its effects on their reproduction. Avian reproduction
impairment is perhaps the most thoroughly documented DDT
effect. Of this phenomenon the Administrator wrote in the
Agency's cancellation opinion (Ruckelshaus 1972):
"Finally, I am persuaded that a preponderance of the
evidence shows that DDE causes thinning of eggshells in
certain bird species. The evidence presented included both
laboratory data and observational data. Thus, results of
feeding experiments were introduced to show that birds in the
laboratory, when fed DDT, produced abnormally tnin eggshells.
In addition, researchers have also correlated thinning of
shells by comparing the thickness of eggs found in nature
with that of eggs taken from museums. The museum eggs show
little thinning, whereas eggs taken from the wild after DDT
use had become extensive reveal reduced thickness.
Based upon previous data available to the Agency, and
additional material which has since become available, the
Agency concludes:
1. There is a mass of information showing that egg-
shell thinning phenomenon was not a problem prior to the
introduction of DDT into the environment, a corresponding
remission in severe shell thinning in many affected species
taking place across the nation since the 1972 cancellation,
and there is a clear-cut time relationship between thin
eggshells, concomitant reproductive failures, and DDT use in
North America.
2. There is a spatial relationship showing that the colonies
of birds of susceptible species most exposed and carrying the
highest residues have been the most affected.
3. Time and time again, negative correlations between tne
DDE content of eggs and parents versus thickness of shells
produced have been shown. The only exceptions were the lack
of correlation found by one mosquito abatement district
manager on a few eggs and one graduate student who found yet
another negative correlation coefficient, albeit a nonstatistic-
ally significant one (Switzer et al., 1971).
4. Controlled studies have shown repeatedly that many species
are susceptible under laboratory conditions of exposure to
environmental levels of DDE. However, cfiicken and related
gallinaceous birds are generally refractory both in laboratory
studies and their natural habitat. A plausible explanation
11-3
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for how thinning occurs in susceptible species but not in
chickens or other non-susceptible species is the biochemical
mechanism...
5. No other chemical has been shown to produce the degree
and duration of shell thinning produced by DDE.
For all these reasons, the Agency concludes that DDE can
cause thinning of bird eggshells, thus impairing reproductive
success. This phenomenon has been so general and widespread
as to present serious environmental risk to the many avian
species involved."
Derek Ratcliffe in his 1967 paper "Decrease in eggshell
weight in certain birds of prey", first identified the correlation
between tne use of organochlorine insecticides and reproductive
failure and eggshell thinning in wild raptors. Subsequent
studies identified eggshell thinning in numerous species in
North America (Anderson and Hickey, 1972) and correlated reductions
in eggshell thickness with DDE levels in the eggs of brown pelicans
(Blus et al., 1972), white pelicans, great blue herons (King
et al., 1978), peregrine falcons (Cade et al., 1971), sparrowhawks
(Newton, 1973), ospreys (Wiemeyer et al., 1975), black ducks
(Longcore and Stendell, 1983), and other bird species (Stickel,
1975). Significant population reductions in bald eagles
(Grier, 1982), ospreys (Spitzer et al., 1978), prairie falcons
(Pimentel, 1971), and brown pelicans (Blus, 1982) have been
linked to these reproductive effects. The extinction of the
American peregrine falcon as a breeding species east of the
Rocky Mountains has been primarily attributed to use of DDT
(U.S. Department of Interior, 1979A).
The causal link between DDE and avian reproductive effects
is clearly supported by a series of laboratory studies showing
that, under controlled conditions, low dietary exposures of
DDE have statistically significant effects on eggshell thickness
and egg viability. Heath et al. (1969) provided the first
laboratory documentation that DDT and DDE caused thin eggshells.
In an experiment with mallards spanning two breeding seasons, DDE
at a concentration of 3 ppm (wet weight basis) thinned eggshells
11 percent, increased cracking 5-fold, and reduced survival
of uncracked, embryonated eggs by 50 percent. Haegele and
Hudson (1974) showed that shell thinning in mallards persisted
11 months after cessation of DDE exposure. In black ducks,
Longcore and Stendell (1983) report shell thinning at dietary
concentrations as low as 0.6 ppm (wet weight). In earlier
work (1977) these authors showed that a dietary concentration
of 3 ppm reduced shell thickness 20 percent and that eggs
remained significantly thinner (ten percent) than controls up
to two years post-treatment. Reproductive performance was
significantly impacted in ring doves fed a diet containing 40
ppm DDE (dry weight): treated doves took an average of 2.5
times longer to renest than controls, produced 13.5 percent
11-4
-------
fewer eggs/clutch, had ten percent thinner eggshells, and
experienced twice as great juvenile mortality (Haegele and
Hudson 1973). Shell thinning in wild populations has been
particularly severe in predatory birds (Anderson and Hickey,
1972). Laboratory testing with the American kestrel, a small
falcon, showed that a dietary concentration of 2.8 ppm (wet
weight) DDE caused a 9.7 percent decline in mean shell thickness
(Wiemeyer and Porter, 1970). Mendenhall et al., (1983) fed
barn owls a diet containing 3 ppm DDE. This exposure caused
eggshell thinning (20 percent), egg breakage, embryo mortality,
and reduced production per pair. Screech owls fed 2.8 ppm
DDE (McLane and Hall, 1972) also showed significant shell
thinning (13 percent).
It is significant from a risk assessment standpoint that
chronic no-effect levels for DDE to sensitive wildlife are
not well established. Most laboratory studies have reported
effects at the lowest treatment level. This is important
because environmental residue monitoring shows that DDE is
ubiguitous and that continuous low-level (0.01-0.5 ppm)
dietary exposure will occur for many species. Laboratory
research with black ducks (Longcore et al., 1971, Longcore
and Stendell, 1983) has demonstrated that a dietary exposure
of 0.6 ppm caused statistically significant reproductive
impairment; this exposure was considered a near " thresho.l d"
level. For black ducks this particular threshold may be
meaningful but chronic DDE effects will vary species to
species based on differences in sensitivity. For example,
black ducks and barn owls have both been tested at a dietary
concentration of 3 ppm. This exposure thinned black duck
eggshells 17.6 percent, but thinned barn ow] eggshells 28
percent. Black ducks were tested at a lower concentration
(0.6 ppm) but barn owls were not. If it is assumed that
responses will be proportionally similar at lower doses, barn
owl eggshells would be reduced 13 percent at 0.6 ppm, black
ducks were eight percent thinner at this level. Moreover,
laboratory exposures have generally been for one to two
laying seasons while actual exposures may occur over far
greater time periods (5-15 years are not uncommon ages for
many of the larger bird species). Thus estimations of effect
thresholds or no-effect levels must be made cautiously,
particularly for endangered species with a history of DDT
effects.
Field monitoring studies lack controlled or precisely
known exposure information. Nonetheless, important inferences
about dietary concentrations of DDE toxic to birds can be
made from them:
(1) Bald eagles in Maine from 1962 to 1970 had young in
only 26 percent of their nesting attempts and produced an
average of 0.35 young per active nest (production of 0.7
young per nesting attempt was estimated as the minimum reguired
for population stability [Sprunt et al., 1973]). Bald eagle
eggs collected in Maine between 1969-1979 had shells 13 percent
thinner than pre-DDT era specimens (Wiemeyer et al., 1984).
11-5
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Fish and eels comprise 90 percent of the bald eagle diet in
Maine, with birds, mostly ducks, making up the remainder of
their food (Wiemeyer et al., 1978). Mean DDE (calculated per
site) in fish and eels (Table II-l) collected in Maine (1966
and 1974) ranged from 0.05 ppm to 0.23 ppm. Heath and Hill
(1974) report DDE residues in black duck wings in Maine at
0.48 ppm in 1966 and 0.60 ppm in 1969.
(2) Field monitoring by Blus (1982) showed that Eastern brown
pelicans have pronounced reproductive impairment when egg
residues are 3 ppm DDE. Total nest failure occurs at roughly
4 ppm DDE. Comparison of residues in fish and eggs hy Blus
et al. (1977) suggested there is a 31x relationship between
DDE in pelican food (menhaden) (Table II-2) and that in fresh
eggs. This bioaccumulation factor (food to eggs) indicates
reproductive effects for this population possibly occurring
at dietary levels >_ 0.096 ppm DDE (3 ppm divided by 31).
(3) California brown pelicans experienced drastic reproductive
effects in the 1960's. Anderson et al. (1975) studied eggshell
thickness, egg residues and dietary-pesticide exposures
(anchovies) (Table II-3) in brown pelicans on Anacapa Island and
Isla Coronado Norte. Residues were very high in anchovies in
1969 (3.24 DDE; 4.27 ppm DDTr) but fell sharply with the
reduction in DDT discharge from the Los Angeles sewer system
after 1970. Anchovy residues (DDE) were 0.84 in 1970, 0.74 in
1972 and 0.12 ppm respectively, by 1974. Eggshell thinning
correspondingly fell from 30 percent (intact eggs) in 1969 to
17 percent in 1974. Pelican reproduction had much improved
by the early 1980's but eggshell thinning persists in a
portion of the population (Gress, 1984), presumably even
though DDE dietary levels have fallen to 0.10 ppm or less.
(4) Thompson et al. (1977) collected fish regurgitated by wild
pelicans in Florida in 1970-71 to estimate dietary exposures.
Fish obtained, by species, had DDE residues ranging from
0.004 to 0.033 ppm (wet weight, whole fish) with a mean of
0.017 ppm. Total DDT homologs were present at (mean) 0.051
ppm. Forty-three eggs collected had an overall mean of 0.9
ppm DDE and DDTr of 1.32 ppm (wet weight). Food to egg
bioaccumulation was 52.7x for DDE and 25.8 for DDTr. Blus
(1970) measured eggshell thickness in 12 pelican colonies in
Florida during this period (1969) finding reductions of 5.9
percent in Gulf coast colonies and 9.0 percent for Atlantic
coast colonies.
(5) Pruett-Jones et al. (1981) measured residues of DDTr in
eggs and shell thickness in peregrine falcons in Australia.
Their research also included measurement of DDTr in 14 species
of birds considered representative prey of peregrines. DDE
residues in eggs ranged from 2.3-82 ppm. Shells were estimated
to be 20.4 percent thinner than eggs collected prior to 1952.
Prey species averaged 0.11 ppm DDE. Most commonly eaten
species by peregrine were the feral pigeon (DDE = 0.05, DDTr =
II-6
-------
Table II-l
DDE and DDTr residues in potential bald eagle food items in
Maine, 1966-1974 (Wiemeyer et al., 1978).
PPM, Wet Weight
County
Area
Year
DDE
GM1
DDTr
Sample
Composition
Washington
1966
0.17
2
Fish
Washington
1974
0.05
2
Fish and eel
Hancock
1966
0.14
0.54
Fish
Penobscot
1974
0.053
2
Eel
Lincoln
1966
0.23
0.42
Fish and eel
Lincoln
1974
0.09
0.20
Fish and eel
Lincoln, Sagadahoc
1966
3.22
2
Herring gulls
Washington
DDE Fish Range (Geo. means) = 0.05 - 0.23
DDTR Fish Range (Geo. means) = 0.20 - 0.54
1Geometric means. Samples with no detectable residue were included as 0.025
ppm (1/2 the limit of sensitivity).
2ddd and DDT were largely or entirely non-detectable.
^Single composite sample, not a geometric mean.
11-7
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Table II-2 Residues of DDE and DDTr in Atlantic menhaden regurgitated
by brown pelicans in South Carolina, 1973 (Blus et al., 1977).
PPM, Vfet Wteiqht
DDE
DDTr
0.04
0.12
0.06
0.15
0.07
0.12
0.06
0.12
0.05
0.10
0.08
0.13
0.15
0.28
Geometric 0.067 0.138
Means
11-8
-------
Table II-3 Eggshell thickness, egg residues and dietary-residue exposure in
California brown pelicans (1969-1974) (Anderson et al., 1975).
Year
DDTr residues are PPM wet weight basis.
Egg Residue^
Anchovy
Residue
1969
DDE DDTr
3.24 4.27
DDE
(1)2 37.5
(C)3 50.8
DDTr
39.9
53.0
Percent Shell
Thinning
Broken
Eggs
50
Intact
Eggs
31
1970
.84 1.40
50
32
1971
1972
.87 1.34
.74 1.12
Not
9.72 Measured.
46
49
20
24
1973
.18
.29
7.7
8.05
41
12
1974
.12
.15
4.25
4.255
35
17
19754
4.975
37
11
1 Original data reported ppn lipid. Conversion to wet weight based on
egg lipid content of 4.4% (Blus 1982).
2 Intact eggs
3 Cracked eggs
4 Anderson et. al. 1977
5 DDT and COD not detected
11-9
-------
0.06 ppm wet weight) and the common starlinq (DDE = 0.13,
DDTr = 0.13 ppm wet weight).
(6) Eggshell thinning and organochlorine residues in pereqrine
falcons and their prey were studied by Enderson et al. (1982)
in Colorado and Northern New Mexico (1973-79). Eggshells in
141 eggs averaged 16 percent thinner than pre-1947 eggs for this
species. A sample of 47 eggs for this species contained a
mean of 20 ppm DDE. Among 12 prey species freguently taken
by peregrine in the area, DDE residues ranged from 0.04 to 6
ppm (wet weight) with a geometric mean of 0.32 ppm (arithmetic
mean = 0.88 ppm DDE).
These data suggest that chronic dietary exposures below
0.5 ppm, and perhaps below 0.1 ppm, may cause eggshell thinning
or otherwise adversely affect reproduction in sensitive avian
species (Blus, 1984). Sections B and C of this report will
demonstrate that avian food chains in major dicofol use areas
are contaminated with DDTr at or above these concentrations.
b. Behavioral Effects on Birds
The relationship of DDE to physiological effects such as
thinning of eggshells has been extensively studied. DDE has
also been linked to abnormal behavior that is more difficult to
document in wild populations but that may also reduce product-
ivity. Ratcliffe (1970) observed peregrines eating their own
eggs and speculated (1972) that pesticide-induced behavioral
disturbances may be important in egg losses. Synder et al.
(1973) studied productivity of wild Cooper's hawks. They
found broken eggs that had thin eggshells but also found egg
breakage when shells were not exceptionally thin? high DDE
content occurred in all cases, however. This fact suggested
that the pesticide contributed to egg loss in ways other than
just by shell thinning. Their observations of poorly constructed
nests and of a female Cooper's hawk inability to properly feed
its young suggested possible behavioral effects.
In controlled DDE-dietary studies, behavioral effects
related to reproduction have been reported. Pisebrough and
Anderson (1975) found that mallards given a diet containing
40 ppm DDE and 40 ppm PCB had significantly greater egg
losses than either controls or mallards exposed to DDE or PCB
(40 ppm) separately; losses were primarily from parental egg-
eating. Wiemeyer and Porter (1970) found that egg disappearance
in kestrels receiving a diet containing 3 ppm DDE was significantly
greater than in control birds. Haegele and Hudson (1977)
found that DDE in the diets (10 and 40 ppm) of ringed turtle
doves suppressed courtship behavior and increased (2.5x) the
time to renesting (Haegle and Hudson, 1973). Body residues in
experimental birds were lower than in some wild species that
experienced reproductive failure suggesting such that effects
may be occurring in contaminated-populations.
11-10
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Heinz (1976) found that offspring of mallards fed a diet
containing 3 ppm DDE (0.6 ppm wet weight equivalent) were
hypersensitive to maternal calls (more approached the call
and more stayed near the call than controls). In testing of
avoidance response, Heinz found offspring of DDE-treated mallards
travelled a shorter distance from a frightening response.
Because the eggs of mallards that received DDE laid eggs containing
residues similar to those in eggs of seme wild birds, Heinz
suggested DDE-induced behavioral effects may be occurring in
nat ure.
c. Effects on Fish Reproduction
Poor viability in hatchery-raised lake trout in New York
state lead to the discovery that DDT can have pronounced
reproductive effects on fish (Dean, 1963). Hatchery reared
eggs, obtained from wild trout in Lake George, showed extensive
mortality. An intensive follow-up study (Burdick et al., 1964)
revealed that a large proportion of sac-fry died if they
contained 2.9 ppm DDT and DDD, and all died when the concentration
was 5 ppm. DDT residues were attributed to sprayinq for
forest insects near Lake George. Similar instances of DDT-related
hatchery mortality were reported in speckled, rainbow and cut-
throat trout in Canada (Cuerrier et al., 1967), in salmon in
Maine (Anderson and Everhart, 1966, Locke and Havey, 1972) and
in rainbow trout in New Zealand (Hopkins et al., 1969, Dacre
and Scott , 1971) .
Macek (1968) held laboratory brook trout on DDT-treated
feed and similarly found sac-fry mortality. Macek concluded
that residues in female brown trout in his study were similar
to those in wild trout in areas sprayed with DDT for forest
insect control and that reductions in trout fry populations
could be occurring.
In 1969, studies correlated residues of DDT in sea trout
in Texas (Laguna Madre) with those in menhaden, a major food
of sea trout. Reproductive failure had been observed since
1964, with young declining from 30 to 0.2 juvenile trout per
acre. In following years, residues in menhaden sharply declined
and the sea trout populations returned to 1964 levels.
Smith and Cole (1973) exposed adult winter flounder to
filtered seawater containing (in separate exposures) 2 ppb
DDT, 1 ppb DDT + 1 ppb dieldrin and 2 ppb dieldrin. Developing
eggs in DDT-exposed fish showed abnormal gastrulation and 39
percent of larvae at-hatching had vertebral deformities. Bone
erosion and hemorrhaging at vertebrate junctures were observed
in eggs in higher DDT concentrations (greater than 2.39 ppm).
Deformities in control and dieldrin groups were greater than
one percent DDT. DDT residues in eggs ranged from 0.39 to
4.6 ppm with a mean of 2.42 ppm; the rate of mortality in
developing eggs was positively correlated with DDT residues.
11-11
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Scott and Crossman (1973) suggested that DDT-induced repro-
ductive failure played a major role in the decimation of the
commercial lake trout fishery in the Great Lakes. Field
research by the U.S. Fish and Wildlife Service and other
groups (U.S. Department of the Interior, 1981) indicates that
lake trout are not reproducing in Lake Michigan though stocked
lake trout survive in the lake. In laboratory experiments,
fry hatched from eggs of Lake Michigan lake trout were exposed
to PCB and DDE concentrations similar to those found in water
and plankton in Lake Michigan to determine if ambient levels
of these contaminants may be affecting productivity. Based
on environmental residues, the researchers established laboratory
water exposures of 1, 5, and 25 ng/L (ppt) DDE and 10, 50 and
250 ng/L PCB. Fish diets were also treated and were, correspond-
ingly, 0.1, 0.5 and 2.5 ppm DDE and 1, 5 and 2 5 ppm PCB. DDE
and PCB esposures were run separately and in concert. Mortality
among fry in all DDE and DDE + PCB exposures was significantly
(PC0.05) greater than in controls. The mortality in the two
lowest PCB concentrations was greater than in controls but
not statistically significant. By the end of the study, the
total cumulative mortality ranged from 30.5 to 46.5 percent
in exposed groups and was 21.7 percent in the control group.
The researchers concluded that "because fry exposed to the lx
PCB + DDE concentration received contaminant doses similar to
those experienced by lake trout fry in Lake Michigan, the
difference in final mortality between these fry (40.7 percent)
and control fry (21.7 percent) is particularly important."
d. Accumulation of DDE in Birds Fed Diets
Containing Dicofol
Heinz et al. (unpubl.) fed 14-day old bobwhite diets
containing different amounts of either DDT or dicofol for a
period of 6-weeks:
Pesticide Dietary Concentrations (nominal)
DDT 0, 5, 10, 25, 50, 100
Dicofol 0, 25, 50, 125, 250, 500
At the conclusion of the test, bird livers were analyzed for
DDTr compounds. Results showed that DDE accumulated in the
livers of all birds fed dicofol. The researchers observed
that:
"The lack of dicofol and high levels of DDE in the livers
of birds fed dicofol was surprising. As a check, we prepared
the carcasses and livers of 2 additional quail that had been
fed dicofol for 2 weeks. The livers contained 9.9 and 10 ppm
DDE, no dicofol, and 1.7 and 1.2 ppm p,p'-DCBP. The carcasses
contained 9.4 and 5.2 ppm DDE, 28 and 17 ppm dicofol, and no
p,p'-DCBP. From this we conclude two things: 1) we cannot
detect dicofol in the liver, and 2) high levels of DDE
resulted from feeding dicofol. The small amounts of DDE
found as a contaminant of dicofol diets probably could not
11-12
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account: for the high levels of DDE in livers. For example,
only 3 ppm DDE was found in the diet mixed to contain 500 ppm
dicofol, but livers from birds fed this diet contained an
average of 36 ppm DDE. Livers of birds fed 100 ppm DDT contained
an average of only 11 ppm DDE. At the present time, we
cannot explain the high residues of DDE in the livers of
birds fed dicofol, but is is possible that the changes in liver
or blood chemistry we found were the result of DDE not dicofol."
Using the data of Heinz et al., a comparison was made of
the relative accumulation of DDT-compounds in bobwhite livers
at equal dietary exposures of DDT and dicofol (Table II-4).
This comparison shows that birds exposed to dicofol acquired
DDTr at levels 15-51 percent that of birds exposed to equal
concentrations of DDT. Heinz et al., as a check on their
initial results, analyzed two bobwhite that were fed dicofol
(500 ppm) for two weeks (previous groups were fed six weeks).
These birds likewise accumulated DDE in their livers (9.9 and
10 ppm). Carcass concentrations were reported for these
check-samples and were similar to the liver residues (9.4 and
5. 2 ppm) .
This experiment does not define residue uptake sufficiently
to allow discrimination between several alternative explanations
for the high DDE accumulation in dicofol-fed birds. However,
the presence of other DDE precursors at high levels in dicofol
(i.e. Cl-DDT) or even metabolism of dicofol to DDE are possibil-
ities that require investigation.
The accumulation of DDE in quail carcasses, at levels
similar to those in liver, increases the possibility that
birds feeding regularly in treated areas may accumulate
sufficient DDE to pose a hazard to higher trophic level
species. The data here are only suggestive but the lower
dicofol exposure levels in this experiment (25 to 50 ppm dry
weight; six to 12 ppm estimated weight wet equivalent) are
within the range expected immediately following treatment at
the higher application rates (two to three pounds active ingred-
ient per acre) (Kenaga, 1973). Birds in these exposures had liver
residues, and possibly carcass residues, of 1.5 to 2 ppm.
3. National Trends in Residues of DDT and its
Related Compounds in Fish and Wildlife
Since 1967, fish and birds have been periodically sampled
for residues of DDT and its related compounds in the United
States as part of the National Pesticide Monitoring Program
(NPMP). Legal use of DDT was largely stopped by the Agency's
1972 ban, and NPMP monitoring since then has indicated general
reductions in DDTr residues. Residues in several regions,
however, are stable or declining slowly and exceed levels
considered potentially harmful.
11-13
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Table II-4 Comparison of DDTr accumulation in livers of bobwhite fed similar
dietary concentrations of dicofol and DOT (Heinz et al., unpub.)
Pesticide
Dicofol
DDT
Nominal
Dietary
Exposure
25
25
DDE
in
Livers
1.45
1.65
DDTr in Liver - PPM
1.45
2.83
DDTr in liver
frcm Dicofol as
% of DDTr in
liver frcm COT
51%
Dicofol
DDT
50
50
1.97
4.33
1.97
7.84
20%
Dicofol
125
3.63
(2.9)1
3.63
(2.9)1
15%
DDT
100
10.98
19.48
lAdjusted to 100 ppm dicofol
11-14
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a. Fish
As part of the NPMP, freshwater fish of various species
have been periodically collected at over 100 designated stations
throughout the U.S. These data show that the concentration of
DDT and related compounds in fish has declined significantly
since 1969 (Figure II-l) (Schmitt et al., 1983), but DDE is still
being detected at each station. These data, however, also
suggest that DDE residues may have stabilized as analysis of
variance indicates that differences between national averages
determined in 1976-77 (0.40 ppm) and 1978-79 (0.37 ppm) were
not statistically significant. Differences between 1974
(0.57 ppm) and 1976-79 were highly significant.
Schmitt et al. in reviewing the most recent set of
fish monitoring data (1978-79), concluded that the whole-fish
residues considered "are representative of the contaminant
levels to which piscivorous fish and wildlife would be exposed
and can therefore be compared with the following criteria
established by the National Academy of Science (NAS) and National
Academy of Engineers (NAE) for the protection of fish-eating
wildlife: DDT and its metabolites, 1.0 mg/kg (total)." Moreover,
they found that the criterion for DDT and metabolites was
exceeded by at least some or all samples at over 10 percent of
the stations monitored in 1978-79. They also concluded, "the
ubiquity of DDT and its metabolites highlights the persistence
and mobility of these toxic compounds."
b. Birds
Starlings have been monitored for organochlorine residues
at over 110 sites in the United States since 1967-68. Recent
monitoring results (Cain and Bunck, 1983) found DDT residues
in only four samples, but DDE, a persistent metabolite
of DDT, was found at 111 of the 112 sites. Starlings collected
from 14 (12.5 percent) sites had greater than 1 ppm (ug/g) DDE
and seven of these sites had DDE residues consistently above
1 ppm in previous sampling periods (Table II-5). This analysis
also indicated that DDE residues, as a nationwide trend, signif-
icantly decreased between 1976 (0.24 ppm) and 1979 (0.17 ppm)
(1979 is the most recently published survey) and reflected the
pattern of decline in DDE in starlings since the beginning of
the monitoring program (Table II-6). Partial results of the
unpublished 1982 survey (Bunck, 1984) were received from the
U.S. Fish and Wildlife Service. These data show that mean
nationwide DDE-residues in starlings declined numerically
between 1979 (0.17 ppm) and 1982 (0.15 ppm), but the difference
was not statistically significant. Though mean residues have
not declined consistently with each sampling period in the
past, the 1982 data suggest that residue dissipation may be
"leveling off' and that residue losses in the second decade
after cancellation of DDT may be much slower than in the
first decade since the ban.
Wings of hunter-shot mallards and black ducks have also
been monitored in the NPMP. The most recently reported survey
11-15
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Figure II-l DDTr residues in freshwater fish. National Pesticide
Monitoring Program (Schmitt et. al., 1983)
1.2
0.9
0.6
0.3
####
####
####
####
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
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####
xxxx
xxxx
xxxx
xxxx
xxxx
xxxx
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////
p,p' EOT HOMDLOGS, 1969-1979
*###
####
####
xxxx
xxxx
xxxx
xxxx
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////
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####
####
xxxx
xxxx
xxxx
xxxx
xxxx]
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////
####
xxxx
xxxx
xxxx
xxxx
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####
xxxx
xxxx
xxxx
xxxx
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####
xxxx
xxxx
xxxx
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r####
xxxx
xxxx
xxxx
[7777"
////
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
Legend: \///\ DDD
XXXX DDE
#### DDT
-------
Table II-5 Historical mean residue levels in starlings fran 14 collection sites
that had greater than 1.0 ppm DDE in the 1979 collection.
(Cain and Bunck, 1983)
State
Site
1979
1976
1974
1972
1970
Arizona
4-C-l
6.44
5.00
9.11
0.13
14.80
Arkansas
3-G-3
1.27
11.10
9.11
7.95
5.24
California
3-A-l
2.11
1.26
3.65
1.90
3.59
California
3-A-3
1.46
2.20
1.04
0.30
0.77
California
3-B-4
1.68
3.14
1.04
2.31
2.75
California
4-B-l
2.72
7.41
2.71
1.44
2.11
Minnesota
1-G-l
1.06
0.05
NS
NS
0.96
New Mexico
4-D-2
2.67
1.71
0.94
0/63
NS
New Mexico
4-D-3
15.80
12.40
3.70
3.52
1.45
North Carolina
3-1-2
1.27
NS
0.40
1.09
0.77
North Carolina
3-J-l
1.49
1.21
0.65
1.11
0.32
South Carolina
4-1-1
2.26
NS
1.88
5.04
3.00
Tennessee
3-H-3
1.41
0.09
0.11
0.44
0.32
Texas
4-E-3
1.42
1.05
0.49
2.06
NS
11-17
-------
Table II-6 Nationwide Starling Residues Geometric Means (NPMP)
DDE, ppm
Year No. Pools Geom. Means
1970 125 0.355
1972 130 0.387
1974 126 0.229
1976 106 0.24
1979 106 0.17
1982 129 0.15
11-18
-------
(1979-80) (Cain, 1981) showed that DDE was found in all samples
(215 pools, drawn from 5268 wings) ranging from 0.02 ppm (Florida,
Kentucky) to 3.28 ppm (Arizona, Western New Mexico). DDE
residues have declined since 1969, but declines were most
pronounced in early monitoring (White and Heath, 1976, White,
1979) (Table II-7) 1969-1972. DDE levels did not significantly
decrease between 1976 and 1979 in any of the flyways and in the
Pacific Flyway DDE increased 59 percent (0.22 + 0.04 ppm to
0.35 + 0.08) but this difference was not statistically significant.
11-19
-------
Table I1-7 DDE residues (ppn) in duck wings by year and flyway.
19691 19721 19762 19792
Species Flyway
Black
Atlantic
1.32
0.35
0.39
0.32
Mallard
Atlantic
1.03
0.44
0.32
0.27
Mississippi
0.40
0.37
0.25
0.17
Cent, ral
0.30
0.15
0.28
0.10
Pacific
0.71
0.34
0.22
0.35
Iwhite and Heath, 1976
2cain, 1981
11-20
-------
B. DICOFOL USE AREAS; RESIDUE TRENDS AND POTENTIAL
EXPOSURE TO SENSITIVE WILDLIFE SPECIES
An Agency investigation of recent dicofol usage estimated
current nationwide application of approximately 2.5 million
pounds (active ingredient) per year. The use of dicofol is
concentrated geographically in California, Florida, Texas and
Arizona (greater than 70 percent of total use).
In the following sections, states with major dicofol
use will be discussed in relation to reported DDTr residues
in wildlife and potential exposure of sensitive animal species.
1. Cali fornia
Usage data, though reported to be incomplete, indicate
that California leads the nation in dicofol use with 1981/82
applications totalling 1,029,700 pounds of active ingredient
or 37 percent of total U.S. use. Major crop uses are as
follows:
Crop Pounds active ingredient
oranges 36,500
1 emons 36,700
dry beans 88,000
corn 88 ,000
alfalfa 51,600
melons 49,300
grapes 21,300
cotton 634 ,600
Dicofol DDTr-contami nation levels are not precisely known.
A Rohm and Haas product composition report received by the Agency
on May 21, 1981 indicates that technical dicofol (85 percent
active ingredient) contains DDT, DDE, DDD, and tetrachloro-DDT
(Cl-DDT), collectively known as DDTr. The estimated 1,029,700
pounds active ingredient used in California 1981/82 is equivalent
to 1,211,412 pounds of technical material (which is 85 percent
dicofol). The technical contamination levels reported by
Rohm and Haas suggest dicofol use in California may result in
annual release of over 120,000 pounds or 60 tons annually of
DDTr (assuming a ten percent contamination level).
11-21
-------
a. Environmental Residues
Monitoring studies of pesticide residues in California
fish and wildlife indicate that DDE, the persistent metabolite
of DDT, is ubiquitous. DDT use in California was extensive
prior to 1972 and undoubtedly much of the past and present
residues in animal samples are from this source (California
State Resource Control, 1977). Nonetheless, the DDTr in
dicofol will also contribute to these residues.
As discussed in Section A, NPMP monitoring of DDE residues
in starlings has shown a pattern of decline nationally since
the early 1970's. In California nine sites have been monitored
consistently and data from these sites show that residues in
California exceed the national average (Table II-8). Of the
sites in the United States currently having high DDE residues,
four are located in California (see Table II-5); these four
sites in California have consistently had residues above 1 ppm
(wet weight) since 1970 (Figure II-2).
Dicofol is used in these areas (Table II-9), but no cor-
relation is apparent between current use estimates (by county)
and starling residues. This is not unexpected as the majority
of DDE residues probably result from past DDT use, the areas
considered are large and the relationship of sample collection
sites to dicofol use areas is unknown, and both starlings and
DDTr are mobile in the environment. To the extent that
starlings reflect DDE trends in other small avian species, it
is significant both that residues are not rapidly dissipating
and that these levels are above levels chronically toxic to
higher food chain species.
DDE residues in mallard wings have been monitored in
California since 1966 in NPMP surveys. Reported residues
(Heath and Hill, 1974; White and Heath, 1976; White, 1979A;
and Cain, 1981) have declined with each monitoring study since
1966 (Table 11-10). The temporal pattern shows stable mean
residues between 1966 and 1969 (1.45 ppm vs 1.52 ppm DDE)
with a large drop subsequently occurring between 1969 and
1972 (0.60 ppm). Since 1972, the rate of decline has
slowed to the point where there is no significant difference
between the 1976 mean and the 1979 mean. Confidence that a
continual decline will occur is undermined by the sizable
increases in state mean values between 1976 and 1979 in the
Pacific Flyway states of Colorado, Oregon, Arizona and New
Mexico and the increase in pooled Pacific Flyway values in
the interval (1976 x = 0.22 ppm; 1979 x = 0.35 ppm DDE)
(Table 11-11).
DDT residues in freshwater fish have been routinely
measured in California by both state and Federal monitoring
programs. Sampling at two locations (Table 11-12) in the central
valley through the the National Pesticide Monitoring Program
11-22
-------
Table II-8 NPMP residues (DDE, geometric means) in starlings in California and
U.S., 1967-1979. Values are ppm wet weight.
Sampling Year U.S. California
1967-68 0.579 1.013 (Fall)*
1970 0.355 0.912
1972 0.387 0.77
1974 0.229 1.09
1976 0.254 0.96
1979 0.17 0.66
1982 0.15 0.42
*First surveys were at different times throughout the year.
Lipids varied seasonally, therefore, fall samples (November 1968) were used
for comparison to later years which were all November-December.
11-23
-------
Table II-9 Organochlorine residues in starlings at NPMP sites monitored in
1979 (Cain and Bunck, 1983).
Residues - ppm Wet ffeight
Dicofol Use (lbs. a.i.)
County Nearest Town Site DDE DDT by county 1981/82
Monterey
Gonzales
3-A-3
1.46
ND1
3800
Inyo
Bishop
3-B-l
0.57
ND
-
Kern
Buttonwillow 3-B-4
1.68
ND
156,100
Imperial
Holtville
4-B-l
2.72
ND
44,600
Colusa
Maxwell
2-A-l
0.30
ND
23,600
Shasta
Redding
2-A-2
0.12
ND
-
Modoc
Alturas
2-A-3
0.67
ND
-
Ventura
Ventura
3-A-l
2.11
ND
34,400
Stanislaus
Modesto
3-A-2
0.12
ND
37,000
1 Not detected
11-24
-------
Table 11-10 DDE Ojck wing residues in California (NPMP).
Mean
Year PPM DDE ( S.E.) Range No. Pools % Change
1965-66 1.45 (+ .17) 0.02 - 3.50 11
1969 1.52 (.19) 0.99 - 2.7 8 +5%
1972 0.60 (.19) 0.30 - 2.3 10 -61%
1976-77 0.44 (.12) 0.15 - 1.18 10 -27%
1979-80 0.34 (.1) 0.06 - 0.72 6 -23%
11-25
-------
Table 11-11 DDE in Mallard wings - Pacific Flyway (NPMP)
Year
PPM DDE
SE
No. Pools
1966
0.70
0.063
117
1969
0.71
0.054
51
1972
0.34
0.043
55
1976
0.22
0.04
50
1979
0.35*
0.08
44
* Residue increases found in Oregon (0.25 to 0.57), Colorado (0.13 to 0.60),
and Arizona and New Mexico (0.33 to 1.22).
11-26
-------
Table 12. DDTR residues in fish at 2 NP
(Unpublished data - L. Ludke,
STATION 39, SACRAMENTO RIVER AT SACRAMENTO, CA
P,
P'-DOT
MEAN MEAN
HOMOLOGUES
TL
WT
LIPID
10
YEAR
SPECIES
(CM 1
(KG)
C/.)
DDE
DDO
ODT
1
69
COMMON CARP
32.8
0.4
4.1
0.94
0.32
0.08
z
69
LARGEMOUTH BASS
27.4
0.3
1.8
0.30
o.ia
0.16
3
69
WHITE CATFISH
35.8
0.6
5.6
0.86
0.32
0.21
4
70
COMMON CARP
27.7
0.4
2.2
2.92
0.37
0.09
5
70
IAG RE-ANALYSIS
-
-
3.3
1.14
0.64
0.00
6
70
COMMON CARP
31.2
0.5
7.2
3.58
1.15
0.34
7
70
Q/A RE-ANALYSIS
-
-
7.6
1.44
1.12
0.01
8
70
LARGEMOUTH BASS
30.2
0.5
3.1
2.51
1.30
0.33
9
70
WHITE CATFISH
21.1
0.1
4.7
1.46
0.57
0.40
10
71
COMMON CARP
33.0
0.6
8.8
2.43
0.78
0.18
11
71
Q/A RE-ANALYSIS
-
-
10.0
6.44
1.72
0.22
12
71
IAG RE-ANALYSIS
-
-
11.1
0.69
1.94
0.00
13
71
COMMON CARP
32.3
0.6
9.5
3.26
0.81
0.16
14
71
LARGEMOUTH BASS
31.7
0.6
5.2
0.86
0.43
0.19
15
71
LARGEMOUTH BASS
28.7
0.5
3.9
1.03
0.68
0.13
16
71
WHITE CATFISH
23.1
0.2
6.6
1.04
0.41
0.16
17
71
WHITE CATFISH
23.9
0.2
5.9
0.58
0.25
0.13
18
72
COMMON CARP
29.5
0.5
4.6
1.20
0.30
0.01
19
72
Q/A RE-ANALYSIS
-
-
4.6
1.67
0.34
0.03
20
72
COMMON CARP
29.2
0.5
6.4
2.00
0.60
0.01
21
72
LARGEMOUTH BASS
28.7
0.4
2.30
0.87
0.15
22
72
WHITE CATFISH
25.9
0.2
6.5
3.50
0.60
0.10
23
73
COMMON CARP
47.8
1.3
12.4
3.20
0.51
0.00
24
73
IAG RE-ANALYSIS
-
-
8.4
3.66
,0.86
0.00
25
73
COMMON CARP
51.6
1.9
9.0
1.70
0.40
0.00
26
73
WHITE CATFISH
30.0
0.3
2.6
1.20
0.24
0.00
27
73
Q/A RE-AHALYSIS
-
-
3.3
0.99
0.18
0.06
28
74
COMMON CARP
42.2
0.6
7.5
2.20
0.68
0.00
29
74
Q/A RE-ANALYSIS
-
-
7.7
0.30
0.20
0.03
30
74
IAG RE-ANALYSIS
-
-
11.4
0.26
0.62
0.00
31
74
LARGEMOUTH BASS
29.7
0.4
5.7
1.10
0.43
0.09
32
74
LARGEMOUTH BASS
29.7
0.4
6.5
1.10
0.40
0.09
33
74
WHITE CATFISH
25.4
0.2
6.2
1.20
0.29
0.10
34
77
GOLOFISH
31.5
0.6
6.0
0.69
.0.19
0.00
35
77
GOLDFISH
25.9
0.3
7.1
0.54
0.22
0.00
36
77
IAG RE-ANALYSIS
-
-
7.1
0.54
0.22
0.00
37
77
LARGEMOUTH BASS
31.7
0.5
5.0
0.46
0,13
0.00
38
79
BROWN BULLHEAD
-
-
2.3
0.23
0.09
0.03
39
79
LARGEMOUTH BASS
-
-
4.0
0.25
0.08
0.01
stations in California.
IFWS, Columbia, Mo)
STATION 40, SAN JOAQUIN RIVER AT LOS BANOS, CA
P.
P'-DDT
MEAN
MEAN
HOMOLOGUES
TL
WT
LIPID
10
YEAR
SPECIES
(CM)
(KG)
m
DDE
ODD
DDT
1
69
BLACK CRAPPIE
26.4
0.3
6.1
0.62
0.49
0.25
2
69
COMMON CARP
37.3
0.6
2.0
0.86
0.40
0.14
3
69
CHANNEL CATFISH
40.9
0.5
5.7
0.78
0.58
0.21
4
70
BLACK CRAPPIE
29.5
0.5
9.5
0.70
0.84
0.44
5
70
Q/A RE-ANALYSIS
-
-
9.6
0.34
1.00
0.71
6
70
BLACK CRAPPIE
27.4
0.5
8.7
0.67
0.71
0.39
7
70
COMMON CARP
38.4
0.8
4.8
1.52
0.60
0.42
8
70
CHAK71EL CATFISH
42.2
1.0
6.7
1.21
0.98
0.59
9
71
BLACK CRAPPIE
25.9
0.4
7.7
0.24
0.46
0.07
10
71
BLACK CRAPPIE
25.4
0.4
7.1
0.22
0.45
0.06
11
71
Q/A RE-AHALYSIS
-
-
7.7
0.27
0.35
0.09
12
71
comon CARP
32.8
0.6
2.3
0.62
0.21
0.04
13
71
COMMON CARP
30.2
0.6
2.6
0.14
0.11
0.02
14
71
CHANNEL CATFISH
39.6
1.1
7.7
0.41
0.59
0.21
15
71
CHANNEL CATFISH
36.1
1.0
8.3
0.72
0.91
0.39
16
72
BLACK CRAPPIE
27.9
0.4
6.3
0.39
0.33
0.01
17
72
COMMON CARP
29.5
0.5
2.8
0.18
0.10
0.00
18
72
COMMON CARP
30.5
0.5
2.9
0.25
0.20
0.00
19
72
SACRAMENTO BLACKFISH
29.0
0.4
12.4
0.20
0.11
0.00
20
73
COMMON CARP
34.8
0.5
1.1
0.07
0.00
0.00
21
73
CHANNEL CATFISH
26.4
0.1
2.4
0.13
0.07
0.00
22
73
CHANNEL CATFISH
32.3
0.3
3.1
0.22
0.14
0.00
23
73
WHITE CATFISH
30.5
0.3
1.3
0.35
0.00
0.00
24
77
SACRAMENTO BLACKFISH
31.2
0.4
8.5
0.20
0.06
0.00
25
77
IAG RE-ANALYSIS
-
-
8.5
0.20
0.06
0.00
26
77
SACRAMENTO BLACKFISH
27.9
0.3
6.5
0.16
0.04
0.00
27
77
STRIPED BASS
33.0
0.4
7.0
0.16
0.06
0.00
28
79
BLACK BULLHEAD
-
-
2.2
0.10
0.04
0.01
29
79
Q/A RE-ANALYSIS
-
-
2.3
0.11
0.03
0.00
30
79
Q/A RE-ANALYSIS
-
-
2.6
0.13
0.00
0.00
31
79
BLACK BULLHEAD
-
-
1.6
0.09
0.02
0.00
32
79
GREEN SUNFISH
-
-
5.1
0.09
0.02
0.00
-------
J.so •
A
/.
3.25
3,00
PPM
2.75
Dfcr
2.50
2.25
2.00
1.T5
1.50
V /
A
\
1 .25
1.00 •
196(1
1970 1972 1974 1976 1978 1980 1982
TIME
Figure 2. Mean DOE residues in starlings in the 4 'high residue' counties
in California 1968-1982 (Kern, Ventura, Imperial, Monterey).
Data 1968-1979 from published NPMP surveys, 1982 results from
Bunck (pers. comm.).
-------
have indicated a decline in DDE in fish. Residues at these
stations in 1969 and 1970 were approximately in the 1-2 ppm
(wet weight-whole fish) range and by 1979 had declined to 0.1
- 0.2 ppm DDE.
Fish pesticide-residue surveys by the state of California
(Figure II-3) were more extensive than NPMP monitoring in the
period 1976-1983. Though residues have fluctuated from year
to year, state monitoring stations in San Joaquin Valley
and the Imperial Valley have repeatedly shown residues that
approach or exceed NAS ecological-hazard levels (1 ppm DDTr).
Dicofol use in these counties is shown in Table 11-13.
Concerning these areas, the California State Water Resources
Control Board (1981) noted that:
"Catfish from both the San Joaauin and Alamo rivers again
exceeded the NAS recommended guideline for total DDT concentra-
tions. Catfish from the New River contained total DDT residues
that essentially equalled this guideline. Levels of DDT and
its derivatives in fish from these three rivers have exceeded
the NAS recommended guidelines of 1.0 ug/g (fresh weight
basis) during all five years."
Fish fillet residue data for these areas were compiled
for the period 1976-1983 from published state reports (California
State Water Resources Control Board, 1979a; 1979b; 1979c; 1981;
1982; 1983; and 1984). Results for San Joaguin Valley stations
are shown in the Table 11-14. DDTr trends were analyzed for
catfish species by station by regression (Statistical Analysis
System 1979; General Linear Model procedure). No significant
declines were evident (Table 11-15). A pooled data set for the
three stations was also analyzed; regression analysis did not
indicate a downward trend in DDTr residues (Table 11-15),
rather levels have remained relatively constant throughout
the monitoring period (Figure II-4).
Fish residue data for station 37 (New River) and station 38
(Alamo River) are shown in Table 11-16. Trend analysis
(regression) for these sites does not show residue dissipation.
Regression of the channel catfish residue data on sampling
year for the Alamo River indicates a significant increase.
Highest values for Alamo River channel catfish and carp, in
the 1976-1983 period, were recorded in the most recent survey
(1983). Available use data (Table 11-13) indicate significant
increases in dicofol use in this region (Imperial County) in
recent years (1981-1983). No other significant regression
trends were demonstrated (Table 11-17). Regarding the DDTr
contamination at these stations California state researchers
stated that:
"The Alamo and New rivers are the two major sources of
freshwater for the Salton Sea. Because concentrations of DDT
and its metabolites in fish from both the Alamo and New rivers
remain elevated, often near or above the level known to
produce shell thinning of bird's eggs, there is special
concern about the adverse effects on nesting colonies of fish-
11-29
-------
ure 11-3 California pesticide monitoring network sampling stations
(after California State Water Resources Control Board 1983, p.6).
1 o.
(1
I 20
A
24
»°
i2Sy
(28
.30
.27
31 *
REGION 5
20 SACRAMENTO RIVER/KESWICK
2 I CLEAR LAKE
22 RECLAMATION SLOUGH
23 SUTTER BYPASS
24 BEAR RIVER
25 FEATHER RIVER
26 CACHE CREEK
27 PUTAH CREEK
28 NO. FK. AMERICAN RIVER
29 AMERICAN RIVER
30 SO. FK. AMERICAN RIVER
3 1 SACRAMENTO RIVER/HOOD
32 COSUMNES RIVER
33 SAN JOAQUIN RIVER
34 STANISLAUS RIVER
35 TUOLUMNE RIVER
%
\
REGION 1
1 INDIAN CREEK
2 MAD RIVER
3 RUSSIAN RIVER
REGION 2
4 COYOTE CREEK
5 GUADALUPE RIVER
6 ANDERSON LAKE
REGION 3
7 LOCH LOMOND
8 PAJARO RIVER
9 SALINAS RIVER/MOUTH
10 SALINAS RIVER/GONZALES
I I SAN CLEMENTE RESERVOIR
I 2 LAKE HERNANDEZ
I 3 LAKE SAN ANTONIO
14 LAKE NACIMIETO
15 WHALE ROCK RESERVOIR
I 6 LAKE CACHUMA
I 7 LAKE GIBRALTAR
18 JAMESON LAKE
33<
h
\
REGION 6
36 E. FK. CARSON RIVER
\
\
klO
«
\
%
\
13v
\
16 O
17
41
>40
REGION 4
I 9 VENTURA RIVER
REGION 8
39 SANTA ANA RIVER/PRAOO DAM
40 SANTA ANA RIVER/NORCO
4 1 SANTA ANA RIVER/RIVERSIDE
39
• 38
Legend
• Primary Sampling Stations
° Supplemental Sampling Stations
REGION 9
42 OTAY RIVER
11-30
REGION 7
37 NEW RIVER
36 ALAMO RIVER
-------
Figure II-4 DDTr residues (ppm wet weight) in fish fillets
at San Joaquin Valley sampling stations 33, 34,
35 (California State Water Resources Control
Board), 1976-1983. Data plotted are those shown
in Table 11-14. The arithmetic means were calc-
ulated for each year by pooling species for the
three stations? means are shown by open circles (°)
and are line-connected.
CORVALLSS tPiVIRONMENYAL
CORVALUS, OREGON 9/33J
11-31
-------
'LOT or DOTmAft LC8CN0I * ¦ 1 08S. H
3,99 •
I
OJ
to
2.TS
2.50
2,25
2*00
1.T5
DOT
ItSO
1.25
1*00
0»T5
0.S0
0.29
0»0« ~
1*76
A
A
A I A
1977 1978
1979 1900
re**
2 OMtt etc#
1981 19H2 1983
-------
e II
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
Dicofol use in San Joaquin, Stanislaus and Imperial Counties,
California, 1970-1983 (California State Department of Food
and Agriculture, Pesticide Use Reporting System, pers. comm.
Susan Reaney).
_ Pounds_ActjLve ^ngredj^ent^
Imperial San Joaquin Stanislaus
7162 - 24823
5087 4082 7833
3862 38514 990
6946 40512 28723
1475 43490 37259
6844 41429 25164
7492 57082 163778
4036 58375 36386
5541 20240 26962
5202 15574 36356
6936 7095 22506
22302 13786 18501
46361 27095 37730
23835 43636 25522
11-33
-------
Table 11-14 DDTr residues in fish fillets at three San Joaquin Valley monitoring
stations, 1976-1983. (California State Water Resources Control Board)
Cbs Year River Species DDTr
1
1976
SJ
WC
1.980
2
1976
SJ
C
1.500
3
1976
ST
WC
0.360
4
1976
ST
C
0.860
5
1976
TO
WC
0.550
6
1976
TO
C
0.720
7
1978
SJ
WC
0.500
8
1978
SJ
c
1.268
9
1978
ST
WC
0.131
10
1978
ST
C
0.094
11
1978
TO
CC
0.267
12
1978
TO
C
0.059
13
1979
SJ
CC
2.420
14
1979
ST
CC
0.505
15
1979
TO
CC
2.570
16
1980
SJ
WC
1.230
17
1980
ST
WC
0.169
18
1980
TO
WC
0.213
19
1981
SJ
CC
1.417
20
1981
SJ
CC
0.983
21
1981
ST
CC
0.369
22
1981
TO
CC
0.301
23
1982
SJ
CC
0.611
24
1982
SJ
C
0.440
25
1982
ST
CC
0.443
26
1982
TO
CC
0.459
27
1983
SJ
CC
1.379
28
1983
SJ
WC
1.094
29
1983
ST
CC
0.479
30
1983
ST
WC
0.472
31
1983
TO
CC
0.935
32
1983
TO
WC
0.824
SJ = San Joaquin
ST = Stanislaus
HI = Tuolumne
C = Carp
CC = Channel catfish
WC = White catfish
11-34
-------
Table 11-15 Results of regression analyses of DDTR-residue trends in catfish
species at 3 San Joaquin Valley sampling stations 1976-1983.
Station
River
Species
F
P>F
R2
33
San Joaquin
WC
0.32
0.63
0.14
CC
2.98
0.18
0.5
WC + CC
2.13
0.18
0.18
34 Stanislaus
WC
0.36
0.61
0.15
CC
0.08
0.81
0.04
WC
+ CC
0.01
0.93
0.001
35 Tuolunne
WC
0.16
0.76
0.14
CC
0.16
0.72
0.05
WC
+ CC
0.03
0.88
0.003
Pooled stations and species
0.22
0.64
0.007
VC= White catfish
CC= Channel catfish
11-35
-------
Table 11-16 DOT hcmologs in fish collected in routine sampling (California State
Water Resources Control Board) 1976-77 to 1983, Alamo and New Rivers.
Alamo River New River
sp ppm* sp ppm*
1976/77 cp 3.11 bnb 1.455
t 0.692
1978 cc 0.882 cc 3.368
cp 1.490 cp 0.124
1979 cc 3.37 cc 2.2
cp 1.423
1980 cc 2.482 cc 0.978
cc 1.609
cc 2.231
1981 cc 3.582 cc 0.852
cp 4.621 cp 0.64
1982 cc 3.248 cc 2.739
cp 2.060 cc 1.723
cp 0.461
1983 cc 5.3 cc 2.794
cp 9.098 cp 0.182
* = total DDT (DDT + COD + DDE + DEMU + DEMS) in fish fillets
cp = carp
cc = channel catfish
bnb = big mouth buffalo
t = tilapia
11-36
-------
Table 11-17 Results of regression analyses of DDTR trends for channel
catfish and carp at station 37 (New River) and station 38
(Alamo River) 1976-1983.
Station Species F P>F r2
37 Channel Catfish 0.07 0.8 0.01
Carp 0.28 0.64 0.08
38 Channel Catfish 9.87 0.035 0.71
Carp 1.52 0.31 0.34
11-37
-------
eating birds around the Salton Sea" (California State Water
Resources Control Board, 1981).
The Alamo and New Rivers flow from Mexico into the U.S.
As DDT is still legally used in Mexico (Schmitt et . al. 1983),
it is reasonable to guestion how much DDT applications in
Mexico contribute to the DDTr fish residues observed at
near-border sites such as those on the Alamo and New Rivers.
Insufficient data are available to fully answer this guestion.
However, the fish-residue analyses have been reported on an
isomer-basis, thus we may test the hypothesis that stations
receiving drainage from Mexico have higher proportions of
p,p-DDT (indicating recent exposure to the parent compound)
than stations which receive no Mexican drainage and are
roughly 400 miles north of the border. Channel catfish were
selected for this analysis as they comprised approximately
one half of all samples reported and occurred at all five
stations. Percentage p,p'-DDT of total-DDT was calculated for
each sample (Table 11-18) and percentages were arc sin transformed
Data were analyzed by two-way ANOVA; stations and years were
examined as sources of variance.
Results (Table 11-19) showed that percentage p,p'-DDT
did not vary over time (P > F = 0.23) but did vary between
stations (P > F = 0.026). Stations near the Mexican border
had lower concentrations of p,p'-DDT (New River, station 37,
x = 4.1 percent; Alamo River, station 38, x = 5.5 percent)
than central valley stations (San Joaguin River, station 33,
x = 11.9 percent? Stanislaus River, station 34, x = 11.8
percent; Tuolumne River, station 35, x = 8.5 percent).
Christopher Schmitt (1984) reports that NPMP fish-residue
surveys indicate a national average for p,p'-DDT at roughly
ten percent of total-DDT over the period 1976 to 1981. From
these data we conclude that the p,p'-DDT concentration in
California fish at San Joaguin and Imperial Valley stations
conform to national trends and that even stations receiving
drainage from Mexico do not indicate significant exposure
from recent DDT applications. This suggests that the apparent
stabilization of DDTr residues at these stations is the
result of the extreme persistence of DDTr or ecosystem loading
of DDTr from sources low in p,p'-DDT (e.g. dicofol).
b. Sensitive Wildlife in California
Peregrine falcons once occurred widely in North America
but are now rare or absent in much of their former range and
have been designated as endangered species by the Fish and
Wildlife Service. Though many factors may have contributed
to their decline the most significant cause of population
reduction was their exposure to DDE (U.S. Department of
Interior, 1982a) . DDE thinned peregrine eggshells such that
egg breakage occurred. DDE may have also resulted in less
well understood behavioral changes such as egg eating, failure
to attempt nesting, reduced nest attentiveness. Though legal
use of DDT stopped in 1972, recent studies have shown that DDE
11-38
-------
Table 11-18 Analysis of p,p-DOT as a percentage of total DDT (DDT + DDD + DDE + DEMU +DEMS)
in channel catfish (Ictalurus punctatus) (California State Water Resources Control
Board 1976 - 1983).
Station
Total DDT
1976- p,p-DDT
77
% p,p-DOT
Tbtal DDT
1978 p,p-DDT
% p,p-DDT
Total DCTT
1979 p,p-DOT
% p,p-Dcrr
Total DDT
1980 p,p-DDT
% p,p-DDT
River
San Joaquin Stanislaus Tuolumne Alamo New
#33 #34 #35 #38 #37
NO CHANNEL CATFISH COLLECTED
0.267
0.028
10.5
0.882
0.066
7.5
3.368
0.159
4.7
2.420 0.505 2.57
0.3 >0.01 0.2
12.4 >2.0 7.8
3.370 1.423 2.200
0.16 0.073 0.1
4.7 5.1 4.5
2.482
0.140
5.6
2.231 1.609 0.978
0.13 0.18 0.15
5.8 11.2 15.3
-------
Table 11-18, continued
River
Station
San Joaquin
#33
Stanislaus
#34
Tuolumne
#35
1981
Total DOT
p,p-DOT
% p,p-DOT
1.417 0.982
0.16 0.046
11.3
4.7
0.369
0.03
8.1
0.301
0.012
4.0
1982
Total DDT
p,p-DDT
% p,p-DOT
0.611
0.083
13.6
0.443
0.08
18.1
0.459
0.039
8.5
1983
Total DDT
p,p-DDT
1.379
0.240
% p,p-DDT 17.4
0.479
0.043
9.0
0.935
0.110
11.8
Alamo New
#38 #37
3.582 0.852
0.063 0.015
1.8 1.8
3.248 1.723 2.739
0.094 0.035 0.045
2.9 2.0 1.6
5.300 2.794
0.121 0.081
2.3 2.9
-------
Table 11-19 Analysis of variance of percent p,p' DDT in channel
catfish at San Joaquin and Imperial Valley monitoring
stations (see Table 11-18).
DEPENDENT VARIABLE: p,p' DDT
SOURCE DF
MODEL 23
ERROR 5
CORRECTED TOTAL 28
SUM OF SQUARES
0.05864255
0.00681323
0.06545578
MEAN SQUARE
0.00254968
0.00136265
F VALUE
1.87
PH > F
0.2520
R-SQUARE
0.895911
C.V.
49.2453
ROOT MSE
0.03691403
p,p* DDT MEAN
0.07495950
SOURCE
YEAR
RIVER
YEAR*RIVER
DF
5
4
14
TYPE I SS F VALUE
0.00548883
0.04095753
0.01219619
0.81
7.51
0.64
PR > F
0.5909
0.0241
0.7664
SOURCE
YEAR
RIVER
YEAR*RIVER
DF
5
4
14
TYPE I SS F VALUE
0.01368727
0.03959420
0.01219619
2.01
7.26
0.64
PR > F
0.2311
0.0259
0.7664
11-41
-------
persists in prey items (i.e. smaller birds: Table 11-20) in
California at levels "sufficiently high to be potentially
deleterious to the reproduction of peregrines" (Risebrough et
al., unpubl). Moreover, DDE is still high in many eggs
(Table 11-21) and shell thinning continues to be a problem.
Migrant species that pick up DDE outside the United States
are likely to be a significant source of DDE to those peregrines
that eat them, but the "comparatively high residues in local
populations of starlings and killdeers suggest that sufficient
DDE still remains in some areas of California to constitute a
potential hazard to peregrines" (Monk et al., unpubl).
Eggshell thinning in California condors, also an endangered
species, has not been clearly correlated with reproductive
failure and "that DDT contamination might have been a major
factor in the recent decline of the species is not obvious
from the nest success and egg breakage data" (Synder, 1983).
The California condor, however, is near extinction with a
current population estimated at fewer than 50 birds (Kiff et
al., 1979) and recent studies suggest that DDE may be a more
important factor in the decline of this species than formerly
thought. Low egg production has precluded collection of
whole eggs for residue analysis but pesticide extraction
from shell membranes has shown DDE in most samples; moreover,
significant shell thinning was documented for pesticide-era
eggs (>1943) and degree of thinning was highly correlated
(r= -.93, P < 0.1) with estimated DDE residues. Eggs of
three pairs of condors are currently being monitored: one
pair is producing eggshells 25-27 percent thinned, a second
pair is showing approximately ten percent thinning and a
third pair is producing eggshells of normal thickness (Synder,
1984.)
The Office of Endangered Species' recovery plan for the
condor (U.S. Department of Interior, 1979b) lists condor habit-
ation of eight counties (Fresno, Tulare, Kern, Ventura, Los
Angeles, Monterey, San Luis Obispo and Santa Barbara). The
Agency estimated total annual dicofol use in these counties
at 317,000 pounds (technical) (Figures II-5 and II—6). This
suggests over (over 30,000 pounds DDTr) added to the environs
of this species each year.
The Pacific population of bald eagles has declined as
have bald eagle populations in most other areas of the
United States. DDT has been related to reproductive failure
(by shell thinning) and direct mortality of adult eagles.
Though eagle reproduction is believed to have improved since
the ban on DDT, "organochlorines (primarily DDE) are still
present in significant levels in some pairs in Oregon" and
"Twenty percent of northwestern eagles examined at Patuxent
Wildlife Research Center (USDI, Fish and Wildlife Service)
recently contained DDT levels high enough to hinder repro-
duction" (U.S. Department of the Interior, 1982). Thelander
(1984) reports that bald eagle reproduction has not
11-42
-------
Table 11-20 DDE Concentrations in prey species of California peregrine
falcons, 1980. (Parts per billion of the wet weight,
nanograms/gram.) (Monk et al. unpubl.)
Collection Arithmetic Standard Geometric Range of
Species Area N Mean Deviation Mean Std. Dev.
Killdeer
2b
3
5000
6300
2000
300-14000
3
2
47
11
46
37-58
5
5
900
900
550
170-1700
7
9
4400
7100
970
95-9800
Short-billed Dowitcher
7
10
250
210
180
72-450
Western Sandpiper
2a
15
290
400
140
41-500
7
10
400
420
210
60-770
Sanderling
7
10
1000
1300
670
280-1600
Red Phalarope
4b
3
630
320
580
360-940
Band-tailed Pigeon
3
3
0.31
0.04
0.
31
0.15-29
Itock Dove
8
3
48
33
42
22-78
Mourning Dove
3
3
65
34
57
29-112
7
3
26
41
6
0.74-59
8
3
44
31
32
11-97
Acorn Woodpecker
3
4
2.0
1.2
1.
7
0.9-3.3
4
4
10
7.1
8.
6
4.4-16
6
10
7
5.8
5.
9
3.4-10
7
5
17
8.7
15
8.4-27
8
5
11
6.4
10
6.1-17
Violet-green Swallow
2b
3
4
4
1
1
380
1600
1200
290
290
120-690
6
10
2400
11-43
1900
1800
790-4000
-------
Table 11-20 (continued)
Species
Collection
Area
N
Arithnetic
Mean
Standard
Deviation
Geometric
Mean
Range of
Std. Dev.
Violet-green Swallow
7
5
3100
2200
2000
1600-2400
(continued)
8
5
5800
1300
5700
5400-7200
Steller's Jay
3
3
3.3
0.58
3.3
2.8-3.9
6
3
76
76
55
21-143
8
3
42
7.2
42
35-49
Robin
1
3
370
420
210
57-800
3
3
490
680
210
39-1100
4
3
880
1400
270
41-1800
Western Bluebird
3
3
29
11
28
19-41
Starling
2
3
91
59
81
45-146
4
3
2100
546
2100
1600-2700
7
3
73
30
69
43-109
Western Meadowlark
3
3
78
48
64
28-147
7
3
43
38
33
12-95
8
3
73
30
67
43-109
Black-headed Grosbeak
6
5
77
52
61
28-135
7
5
54
43
42
21-85
11-44
-------
Table 11-21 DDE and PCB in eggs of California peregrine falcons, 1980-1981. Bggs unhatched in the wild
or which did not successfully hatch during artificial incubation. Parts per million of
the fresh weight as received. (Risebrough et al., unpubl.)
Geographic Area Site* Year DDE PCB % H2O % lipid of dry
Garments
North Interior NI-13 1980 29 12
North Interior NI-13 1980 21 16
North Interior NI-21 1980 30 8
North Interior NI-21 1980 42 18
North Interior NI-21 1980 16 8
North Interior NI-16 1981 19 9
86
63
61
65
81
81
25
23
21
28
31
**
North Interior NI-17 1981 41 12
75
**
Fran first clutch. Died approxi-
mately one week before hatching;
third egg hatched.
Same clutch as above; died
approximately 2-4 days before
expected hatching.
Fran first clutch. Died approxi-
mately two weeks before expected
hatching; other eggs hatched.
Fran second clutch; no developnent,
dehydrated; all eggs died.
Same clutch as above; 1/4 inch
embryo.
Fran first clutch which went
full term in the eyrie. 1V>o
eggs hatched. No development
of this egg.
Fran first clutch of two eggs;
one hatched. Developnent of
this egg - 1/16 inch embryo.
-------
Table 11-21 (continued)
Geographic Area Site* Year DDE PCB
i
cn
North Interior NI-18 1981 2 0.41
North Interior NI-21 1981 31 10
North Interior NI-25 1981 7
Mid Coast MC-2 1980 24 6
Mid Coast MI-2 1980 32 5
Mid Coast MC-3 1980 14 4
Mid Coast MC-4 1980 18 13
% H2O % lipid of dry
Comments
77 ** Frcm first clutch which went
full term in the eyrie. Two
chicks hatched. This egg 1/16
inch embryo.
78 ** Frcm first clutch of two eggs.
None hatched. This egg was
undeveloped.
82 ** Fran second clutch of three eggs;
two hatched. First clutch of
eggs all broken by attending
parent.
84 21 Second clutch;all eggs of first
clutch broken at eyrie; one egg
hatched; this egg 1/4 inch embryo.
80 31 Same clutch as above, no
development.
81 30 First clutch; two other eggs
hatched; 1/4 inch orvbryo.
81 36 No development. Fran second
clutch; second egg hatched.
First clutch all hatched.
-------
Table 11-21 (continued)
Geographic Area Site* Year DDE PCB % H2O % lipid of dry Comments
Mid Coast
MC-2
1981
19
15
79
**
Fran second clutch containing
five eggs; only tvo hatched.
In first clutch two of three
eggs hatched.
Mid Coast
MC-3
1981
27
11
80
**
Fran first clutch in which only
one of three eggs hatched.
Mid Coast
MC-4
1981
26
14
78
**
From first clutch of four eggs.
Three hatched successfully.
South Interior
SI-3
1980
15
5
81
30
Only egg in first clutch; 1/4
inch embryo.
* 1980 U.S. Fish and Wildlife Service designation numbers
** Data unavailable.
-------
AREA
ENLARGED
CALIF
SANTA
VENTURA
V«ntura
NGELCS
Son to
Borbora
Lot ImiIii
Federal Regleter, Vol. 41, No. 187, Sep. 21, 1976
Paragraph 17.64 California Condor
(a)
(1) Se»p«-Plru Condor Area
(2) Haclllja Condor Araa
(3) Slaquoc-San Rafael Condor Araa
(4) HI Mountaln-Beartrap Condor Araa*
(5) Mt. Plnos Condor Araa
(6) Slue Ridge Condor Araa
(7) Tejon Ranch
(8) Karn County rangalanda
(9) Tulare County rangalanda
SO
SCALE IN MILES
UNITED STATES DEPARTMENT OF THE INTERIOR
FISH ANO WILDLIFE SERVICE
DETERMINATION OF CRITICAL HABITAT
FOR
CALIFORNIA CONDOR
Figure 11 -5
DICOFOL USE
1981/82 (lbs a.i.)
Kings County....215,800
Kern County 156,100
Tulare County...113,200
Ventura County.. 34,400
11-48
-------
Figure 11 -6 Geographic range of the California Condor
(U.S. Department of the Interior, 1979b)
SAN JOSE
\ #/
SANTA*
MERCEO
FRESNO
¦\ SAN BENITO
MONTEREY
TULARE
. . . J.
SAN LUIS OBI
BAKERSFIEL
v
SANTA
0 40 hm
1 ' ' 1 i
2*Sn
LOS ANGELES
APPROXIMATE BOUNDARIES
NESTING AREAS
SANTA
BARBARA
ANGELE
1-COAST RANGE POPULATION
AUGUST - DECEMBER
3- SUBPOPULATION
AFFILIATION UNKNOWN
2-COAST RANGE POPULATION
YEARLONG
4- SESPE - SIERRA POPULATION
YEARLONG
5-SESPE - SIERRA POPULATION
MAY - SEPTEMBER
11-49
-------
been studied thoroughly in California; his recent investigations
(with Kiff and Risebrough) indicate significant eggshell
thinning persists and DDE in eggs may reach critical levels.
The four eggs collected in 1983 had greater than 15 percent
shell thinning and one contained over 1100 ppm DDE (wet
weight), one of the highest residue levels ever recorded in a
bird egg (Thelander, 1984). California bald eagles primarily
breed in northern parts of the state but wander widely during
other periods, including southern and central California
where prey items such as fish and ducks are still carrying
potentially hazardous levels of DDE in some areas (see previous
section on environmental residues).
The U.S. Fish and Wildlife Service has begun studies
of black-crowned night herons nesting on San Francisco bay
(Olhendorf, 1984). Preliminary results show some collected
eggs contain DDE residues (wet weight basis) of 15 ppm which
exceed levels (8 ppm) shown to cause effects in previous
studies with this species. Bird-banding recovery data indicate
that a portion of this population winters in the San Joaquin
and Salinas Valleys of central California where they may be
exposed to dicofol application.
2. Arizona
The Agency estimates that dicofol use in Arizona (1981/82)
totalled 126,000 pounds of active ingredient. These applications
were essentially on two crops (cotton - 94,500 pounds and
citrus - 31,700 pounds) and were concentrated in three counties
(Maricopa - 70,100; Pinal - 25,600; and Yuma 18,400 pounds).
A survey of pesticide use in Arizona by the University of
Arizona (Byrne and Roll, unpubl.) indicates increasing dicofol
use in recent years;
1978 1979 1980 1981
18,100 11,000 54,800 106,900
(Dicofol Pounds Active Ingredient)
a. Environmental Residues
Pesticide residue surveys indicate that fish and wild-
life in Arizona are carrying potentially hazardous levels
of DDE (Clark and Krynitisk, 1983; Arizona Department of
Health Services, 1984). Starlings have been monitored at four
sites in the state in NPMP surveys; the station in Maricopa
County, the major agricultural county in the state, has
consistently shown residues among the highest measured in
the U.S. (Table 11-22). Ducks are more migratory than starlings
and perhaps not as good an indicator of local contamination;
however, results of the 1979-80 NPMP duck wing survey show
the Arizona/Western New Mexico sampling area with the
highest mean DDE residue in the nation (1.22 ppm) (Clark
and Krynitsky, 1983). In a separate study (Fleming and
11-50
-------
liable 11-22 National Pesticide Monitoring Survey starling residues at
station 4-C-l, Maricopa County, Arizona.
Rank Nationally
1
5
2
1
1 White, 1976
2 White, 1979b
3 Cain and Bunck, 1983
4 Bunck, 1984
Year
19741
19762
19793
19844
Carcass
DDE (PPM)
9.11
5.00
6.44
8.4
11-51
-------
Cain, in prep.), duck wing residue data from the 1979-80
hunting season were more finely divided geographically in
Arizona. These data show high residues from the eastern
Gila and Verde river areas (1.36 to 5.95 ppm DDE). Most of
these samples were from Maricopa County suggesting the
possible influence of the high local dicofol use.
Monitoring of fish tissue in Arizona has similarly
shown high residues, again particularly in Maricopa County
(Gila River drainage). In Painted Rock Reservoir in 1980
Clark and Krynitsky (1983) reported residues (DDE) in
channel catfish of 9.56 ppm, 6.86 ppm in carp, 7.53 ppm in
largemouth bass and 0.65 ppm in tilapia. In the Gila river,
also for 1980, they report carp with 6.8 and 5.78 ppm DDE.
DDE residues continue at these high levels in 1983 with
Arizona Game and Fish Department (Dahlberg, 1984) reporting
the following information:
Species PPM DDE Location
Carp 7.9 Arlington Canal, Maricopa Count
Catfish 5.0 " "
Carp 1.4 Buckeye Canal, Maricopa County
Carp 5.3 " "
Goldfish 3.4 Gila River, Maricopa County
Though high residues have been concentrated in the
Maricopa County area recent samples (>_ 1980) from southwestern
Arizona (Yuma) have also had DDE residues exceeding NAS (1 ppm)
and FDA (5 ppm) hazard criteria (Arizona Department of
Health Services 1984). NPMP monitoring of fish from station
115 (Colorado River at Yuma) likewise support concern for
elevated residues in this area of the state though
Schmitt et al. (1983) attributed the contamination to use
of DDT in Mexico:
Year
Species
DDT (PPM)*
DDE
1976
Carp
0.03
0.03
1976
Largemouth bass
1.27
0.74
1976
Striped mullet
2.9
1.3
1978
Carp
0.57
0.43
1978
Largemouth bass
1.19
0.83
1978
Striped Mullet
2.91
1.35
*(U.S. Fish and Wildlife Service [NPMP] unpubl.)
b. Sensitive Wildlife in Arizona
Peregrine falcons in Arizona as elsewhere in the U.S. are
endangered. Monitoring in recent years in Arizona indicates
that productivity is normal among many of the pairs studied
(Ellis 1984). Nonetheless, some pairs studied recently nested
unsuccessfully and DDE has been found in unhatchted eggs (1978-
1982) at levels potentially deleterious to reproduction:
11-52
-------
Year
1981
1978
PPM DDE (wet weight except as noted)
33 (dry weight)
14
1982
14
1982
10
1982
6.4
(D. Ellis, 1984)
Peakall (1975) reviewing pesticide residue and repro-
ductive data for the peregrine concluded that a critical
level causing hatching failure was 15-20 ppm DDE (wet weight)
in eggs. Though these values should be used cautiously they
suggest that seme Arizona peregrines are exposed to or
continue carry DDE residues high enough to adversely affect
reproduct ion.
The U.S. Fish and Wildlife Service has made recent
(1981) collections of potential peregrine prey species in
Arizona (Table 11-23) to estimate DDE exposure. These collections
were outside the principal citrus and cotton areas. Residues
in pooled samples for several of the species were considerably
above levels known to cause reproduction effects. Highest
residues were observed in killdeer (8.78 ppm), red-winged
blackbirds (5.55 ppm), cliff swallows (3.2-3.7 ppm), white-
throated swifts (3.06 ppm) and Brewer's blackbird (1.42 ppm).
The southwestern bald eagle reaches its highest density
(12-13 known breeding territories) in central Arizona (US
Fish and Wildlife Service, 1982b). Though these breeding
areas are northeast of the currently known high DDE-
contamination area (Gila river, Painted Rock Reservoir;
Clark and Krynitsky 1983) the eagles wander during non-
breeding periods and both migratory northern bald eagles
and local bald eagles feed on fish and other wildlife in
the Gila drainage, Painted Rock reservoir and lower Colorado
regions (Glintiski, 1984). Recent monitoring in these
areas consistently shows fish residues in excess of 1 ppm
DDE.
Little information is currently available on DDE in
Arizona bald eagles; however, three eggs from two nests in
1977 had DDE ranging from 4.9 - 9.0 (wet weight). These three
eggs had eggshell thickness of 0.513, 0.525 and 0.54 mm. No
historical pre-DDT bald eagle records are available for
Arizona so these thickness values were compared to data
from southern California, Texas, and Florida. These compar-
11-53
-------
Table 11-23 DDE carcass residues in prey species of peregrine falcons in
Arizona. Data supplied by James E. Johnson Albuquerque
Office, U.S. Fish and Wildlife Service.
Pool PPM
Species
Date*
Weiqht (q)
DDE
Killdeer (6)2
7/2/81
367.68
8.78
Mourning dove (10)
6/8/81
830.14
0.04
Mourning dove (11)
7/9/81
554.14
0.03
White-winged dove (5)
6/25/81
550.15
0.01
White-throated swift (11)
7/9/81
234.93
1.5
Ash-throated flycatcher (5)
6/4/81
102.12
0.06
Horned lark (9)
6/28/81
182.98
0.03
Cliff swallow (12)
6/3/81
162.43
3.20
Cliff swallow (12)
6/17/81
179.43
3.70
American robin (7)
7/10/81
416.63
0.21
Western meadowlark (9)
7/2/81
631.16
0.08
Western meadowlark (9)
6/16/81
737.67
0.59
Brewer's blackbird (7)
6/17/81
342.13
1.42
Brewer's blackbird (12)
7/10/81
537.69
0.47
Red-winged blackbird (5)
7/4/81
187.32
5.55
Hooded oriole (8)
6/29/81
148.38
0.26
Steller's jay (9)
7/10/81
720.80
0.05
White-throated swift (11)
6/30/81
233.11
3.06
Brown-head cowbird (4)
7/8/81
108.98
0.43
Brown-headed cowbird (8)
7/8/81
205.98
0.28
1 Species collected over a stretch of dates were assigned a date midpoint
between the earliest and latest collections.
2 Number of birds in pool.
11-54
-------
isons indicated thinning ranging from seven to 15 percent
depending on the historical values used (Grubb and Rubink,
1978) .
From a linear regression relationship of DDE-egg
residues and production of young, Wiemeyer et al. (1984)
projected that 3.5 ppm would result in 0.7 offspring per
nest, the minimum considered necessary for population
stability in bald eagles. Though it is not known how
representative of regional norms the available Arizona egg
residues data are or how applicable the critical offspring
estimate (0.7/nest) is to the Arizona population, the
available egg residue data exceed the 3.5 ppm critical
limit suggesting a potential for DDE-impact on population
stability.
With fish and bird species contaminated with DDE in
parts of Arizona it is reasonable to assume that predatory
birds sensitive to DDE that eat these food resources may be
accumulating residues and showing effects. As elsewhere,
however, such knowledge is restricted by the number of
scientific investigations conducted. In Arizona only one
indepth study of DDE effects on wildlife was located. Synder
et. al. (1973) studied Cooper's hawks in Arizona and New
Mexico in 1969-71. They found evidence of eggshell thinning,
aberrant behavior and nest failure that was positively correlated
with DDE residues in eggs and offspring. The researchers
analyzed prey species of the Cooper's hawk for DDE; though
strict comparisons are not possible, avian species taken had
DDE residues not dissimilar from recent collections made of
the peregrine food base (Table 11-23). No recent follow-up work
was done by the researchers nor is any known to them (Synder,
1984) but it is prudent to assume in the absence of new
information that effects of DDE will not disappear until this
contaminant dissipates from wildlife foodchains.
3. Texas
Dicofol use in Texas is largely confined to citrus
according to Agency records. Citrus production is not widely
dispersed in the state, but essentially occurs in Hidalgo,
Willacy and Cameron counties at the southern tip of Texas
(Figure II-7). Of these counties Hidalgo is the major production
area accounting for roughly 80 percent of the state's citrus
output and probably a similar proportion of the 153,900 pounds
of dicofol used on Texas citrus.
a. Environmental Residues
Hidalgo county has been identified as an area of high
DDE contamination (White et. al., 1983a):
"Over the years, DDE residues have been detected at fairly
high levels in whole-fish composites from NPMP station No. 16
near Mission, Texas. Although DDE residues in fishes at this
11-55
-------
TEXAS
1981
Citrus Production
State Total (boxes)
6,700,000 Grapefruit (G)
4,330,000 Oranges (Or)
Percent of State Total
in Hidalgo County
86% (G)
912 (Or)
Percent of State Total
in Hidalgo,Gameron & Willacy Counties
99.85% (G)
99.72% (Or)
Pounds (a.i.) of Pesticide Applied
To Citrus in Texas (1977)
Dicofol 133,145
Chlorobenzilate 267,101
Arroyo Colorado
Production In
Willacy
100,000 (G)
146,000 (Or)
Production in
Hidalgo
5,740,000 (G)
3,940,000 (Or)
Production in
Cameron
850,000 (G)
232,000 (Or)
Figure 11-7 Citrus production in Texas in 1981 (Texas Crop and Livestock
Reporting Service 1982). Pesticide use estimates are from
Haydu (1981).
11-56
-------
station have varied considerably among years, levels have not
declined appreciably since the use of DDT was banned in 1972,
as they have at most other monitoring stations across the
nation (O'Shea and Ludke, 1979). A survey in 1976 of DDE
levels in fishes from 12 sites along the main stem of the Rio
Grande in Colorado, New Mexico, and Texas, and three sites in
the lower Rio Grande Valley also indicated that residues
varied among sites and among species. With few exceptions,
residues appeared lower at these sites, overall, than those
detected at NPMP station 16. These data are not entirely
comparable since the same species of fishes were not available
at each collecting site. However, the results do suggest
that the major sources of contamination probably were
centered in the lower Rio Grande Valley, especially in the
Llano Grande Lake area, an impounded portion of the Arroyo
Colorado
The NPMP fish residue monitoring at station 16
(Table 11-24) prompted more detailed investigation of fish in
the Arroyo Colorado and also of fish-eating birds. In this
special survey, elevated levels of DDE were detected in
freshwater fish throughout this drainage area- (Table 11-25)
and ranged to 31.5 ppm in channel catfish. Residues were
lowest in the downstream, saltwater stretches of the Arroyo
Colorado and highest in the Llano Grande Lake area which is
an impounded portion of the river. Birds were collected at
several locations in the lower Rio Grande Valley. Residues
were high in all bird species sampled with laughing gulls
showing the greatest DDE contamination. Median residues
in this species were highest in the Llano Grande Lake area
of the drainage (34 ppm) as in fish and lowest in birds
taken in the Laguna Madre (2 ppm). The DDE residues in
great-tailed grackles (14 ppm) and red-winged blackbirds
(4.1 ppm) suggest that terrestrial foodchains are also
contaminated.
Of the birds and fish that were sampled along the
heavily farmed 60 mile stretch of river from McAllen to
Port of Harlinger the researchers concluded:
"The potential impacts of DDE contamination to birds,
especially fish-eating species, of the Arroyo Colorado
flood plain may be great. Birds with body levels of DDE of
the magnitude we report for laughing gulls from this area
would be expected to encounter reproductive difficulties.
"The impacts of DDE and toxaphene on the fishes of the
Arroyo Colorado are unknown. However, experimental studies
have shown that both compounds are toxic to fish in minute
quantities (Johnson and Finley, 1980); DDT and its metabolites
alter certain physiological conditions in fishes including
the normal balance of serum amino acids, thyroid activity,
and the ability to withstand stress. Also, the mortality
of fry produced by treated parents is high.
11-57
-------
Table 11-24 DDE residues (ppm) in whole fish at NPMP Station 16 (Mission, Ttexas)
Year
1969
1970
1971
1972
1973
1974
1976
1978
DDE
Channel Catfish
2.93
7.27
4.17
2.51
7.2
2.7
3.1
1.9
0.21
1.7
DDE
Blue Catfish
1.87
3.98
3.75
6.18
4.4
0.73
1.3
2.53
11-58
-------
Table 11-25 DDE residues (ppm wet weight) in composite samples of
blue catfish (Ictalurus furcatus) and gizzard shad
(Doroscma cepodianun) at freshwater sites in the Arroyo
Colorado drainage in 1978 (White et al., in press)
Site Blue Catfish Gizzard Shad
McAllen 16.7 16.0
San Juan 11.2 18.8
Upper LLano 27.4
Harlingen 10.6 20.8
Port of Harlingen 24.1 9.6
Mean = 18.0 16.3
11-59
-------
"Regardless of the routes of contamination, our data
indicate that fishes and birds of the Arroyo Colorado contain
DDE and toxaphene residues that are within or above the range
known to cause population declines. More importantly, the
contaminated Arroyo Colorado empties into the Laguna Madre,
one of the most extensive breeding and nursery grounds
for fish and wildlife in the United States.
"Studies are under way to determine the reproductive
success of fish-eating birds nesting in the Laguna Madre
near the mouth of the Arroyo Colorado and to evaluate the
effects of pollutants, such as DDE, on reproduction. At
present, results are incomplete, but data thus far indicate
that eggs of some species are high in DDE, eggshells are
thin, and reproduction is poorer than in birds at other
localities along the Texas coast (White, unpubl.).
Additional research is needed to assess the impacts of
pesticides on fishes and aguatic invertebrates in this
heavily contaminated area of the lower Rio Grande Valley,
Texas" (White et al., 1983a).
b. Sensitive Wildlife in South Texas
White et al. (1983b) report that migratory shorebirds
feeding downstream from agricultural areas, at the mouth of
the Arroyo Colorado, significantly accummulate DDE during
their residence in the area and that "potentially dangerous
levels (12 to 68 ppm) in a large proportion (40 percent of
the long-billed dowitchers...and to a lesser extent American
avocets* were observed." Moreover, White et al. note, "In
addition, the shorebirds with high DDE residue levels may
pose a significant hazard to peregrine falcons (Falco peregrinus)
and other sensitive raptors that occasionally prey on them."
The Laguna Madre is an important migratory resting point for
peregrine falcons (Henny, 1984).
Colonies of black skimmers in the Laguna Madre, into
which the Arroyo Colorado empties (Figure II-8), are also
heavily contaminated with DDE (White et al. unpubl.; U.S.
Department of Interior, 1983). Residues in eggs ranged up
to 51 ppm with shells four to 12 percent thinner than museum
specimens (pre-DDT era). Fish eaten by skimmers were collected
where adult birds were seen feeding and from the crops of
chicks; DDE was detected in 87 percent of the fish samples and
ranged from 0.1 to 1.5 ppm with an overall mean of 0.64 ppm
(wet weight). The authors noted that black skimmers migrate
to Mexico and though this is a possible source of the observed
DDE-egg residues, the Texas coastal environment is a more
likely source given the residues found in fish. They also
note that Louisiana and Mississippi colonies of black skimmers
have residues 4-fold lower, even though they also winter in
Mexico. Populations of black skimmers have decreased in
south Texas an estimated 22 percent since the early 1970s for
has yet undetermined reasons.
11-60
-------
Figure 11 - 8 Location of black skimmer study sites. Pesticide concen-
trations shown are the mean DDE residues in eggs at each colony.
(White et al. unpubl.)
study site (5.85 ppm)
Nueces Bay
Corpus Christi
30
km
Port Mansfield
agricultural drains
study sites
Arroyo Colorad
Laguna
Vista *
(8.26 ppm)
Mexico
11-61
-------
4. Florida
The Agency's records show that dicofol use on citrus
accounts for virtually all of the dicofol used in Florida.
Estimated use in Florida in 1980 was 856,800 pounds or roughly
one-third of all U.S. usage.
The Florida Department of Agriculture and Consumer
Services analyzed dicofol products sold in Florida 1984 for
DDTr contamination (Table 11-26). Total DDTr contamination in
ten product samples ranged from 3.0 percent to 15.7 percent
of the advertised dicofol concentration. A 42 percent active
ingredient product (representative of dicofol concentrations
as used in large agricultural treatments, Inman, 1984)
contained 5.9 percent total DDTr of which 1.6 percent was
DDE. Based on the contamination level in this product (5.9
percent and the 1980 state-use total (856,800 pounds) dicofol
applications result in a DDTr release in Florida of 50,551
pounds (which includes 13,700 pounds DDE).
NPMP fish residue sampling occurred at four stations in
Florida: St. John's River, St. Lucie Canal, Suwanee River
and the Apalachicola River. Samples were not collected
after 1973 at St. John's River or Suwanee River station's
thus these sites do not provide adequate data for trend
analysis. DDE residues did not change statistically at
Station 13 on the Applachicola River between 1974-1979
(Schmitt et al., 1983), but this site is in Florida's panhandle
where citrus is not a significant crop. Station .12 on St.
Lucie Canal, which is in a citrus growing region, showed a
statistically significant reduction in DDE from 1974-1979
(Schmitt et al., 1983). The Agency analyzed the data for
Station 12 on a pooled-species basis and found significant
reductions in DDE and DDT (Table 11-27 and Figure II-9) when
the data are considered in their entirety (1969-1980). The
three most recent NPMP surveys at Station 12 however, show
possible recent stabilization in the DDTr residues:
1. Environmental Residues
1976
1978
1980
White catfish
DDE 0.14
DDTr 0.28
0.11
0.17
0.16
0.22
Largemouth Bass
DDE 0.09
DDTr 0.15
0.09
0.15
0.17
0.17
11-62
-------
Tcible 11-26 DDTr contamination in dicofol products sampled in Florida in 1984. Analyzed by
Division of Chemistry, Florida Department of Agriculture and Consuner Services.
Avertised
% Dicofol
10%
18.5%
18.5%
18.5%
3.0%
4.13%
42.0%
18.5%
3.0%
3.0%
Sample #
54331
54131
54651
54235
54341
54210
546251
54927
54662
54769
% Dicofol
11.1
19.1
20.0
19.1
3.3
5.2
45.3
18.9
3.9
3.1
% OP DDT
0.009
0.021
0.045
0.002
0.002
0.002
0.083
0.023
0.002
0.031
% PP cor
0.015
0.007
0.152
0.012
0.017
0.005
0.015
0.015
0.001
0.021
% OP DDE
0.192
0.139
0.159
0.247
0.071
0.013
0.581
0.299
0.077
0.085
% PP DDE
0.026
0.037
0.063
0.040
0.014
0.014
0.080
0.040
0.009
0.009
% OP ER8l
0.004
0.079
0.081
0.052
0.131
0.001
0.324
0.074
0.048
0.035
% PP ER81
0.051
0.975
0.446
0.444
0.235
0.274
1.610
0.961
0.187
0.167
"total DDTEr
as Percent
of
Advertised
Dicofol 3.0 6.8 5.1 4.3 15.7 7.5 5.4
DC® as %
of dicofol 2.2 0.95 1.2 1.55 2.8 0.65 1.6
1 DDT-C1: 1,1-Bis(p-chlorophenyl)-1,2,2,2-tetrachloroethane.
7.6 10.8 11.6
1.8 2.9 3.1
-------
Table 11-27 Regression statistics for NPMP fish samples 1969-80, St. Lucie
Canal, Florida. All values were loglO transformed; samples
with non-detectable residues were assigned a value of 0.005
(1/2 detection limit).
Species
Residue
F
R2
P>F
White catfish
DEC
0.69
0.12
0.44
N=7
cor
3.07
0.38
0.14
1972-78
Blueqill
DDE
0.17
0.03
0.70
N=7
DOT
0.01
0.002
0.93
1969-74
Larqemouth Bass
DDE
4.73
0.32
0.05
N=12
DOT
12.24
0.55
0.006
1969-78
Channel catfish
DDE
5.05
0.46
0.07
N=8
DOT
5.77
0.49
0.05
1969-76
Pooled data
DDE
6.7
0.17
0.01
N= 34
DOT
14.4
0.31
0.006
1969-80
11-64
-------
uts ~
1*00 ~ Figure 11 -9 DDE residues in freshwater fish (loglO transformed) at St.
Lucie Canal, Florida 1969-1980 (NPMP).
0.7®
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
•Ut9 «
69 70 71 72 73 74 75 76 77 78 79 80
TIME
-------
In 1982 the Florida Game and Freshwater Fish Commission
analyzed fish for pesticide residues from Lake Apopka
following reports that catfish contained DDT residues high
enough to raise possible public health concerns (State of
Florida Game and Fish Commission, 1982). Lake Apopka (Figure
11-10) is a large shallow inland lake near citrus groves.
Results of this survey show DDE + DDD residues in pooled
samples of brown bullhead ranging from 0.066 ppm to 0.525
ppm. One yellow bullhead had a residue of 0.403 ppm;
pooled samples of white catfish had residues of 0.319 ppm and
0.40 ppm (DDD + DDE). Sunshine bass had residues ranging
from 0.089 to 0.491 ppm (DDD + DDE). Largemouth bass in two
pooled samples had residues of 0.03 and 0.12 ppm (DDD + DDE).
Florida fish monitoring is of residues in fish flesh
(fillets). Such analysis may be useful for determining
human exposure, but fish-eating wildlife will freguently
consume whole fish which may have residues two or more fold
greater than those found in flesh samples. Viewing the 1982
Lake Apopka fish residue data following application of a 2x
conversion-factor suggests that mean whole-body residues may be
above 0.5 ppm (DDD +DDE). A chronic exposure at this concen-
tration would likely result in adverse reproductive effects
on birds.
b. Sensitive Wildlife in Florida
Wood storks are large wading-birds that occur in the
southern U.S., primarily in Florida. Population levels
have decreased considerably in recent decades (1930: 20,000,
1980: 4,800; Fleming et al. unpubl.) and the species has
recently been added to the Federal Endangered Species List.
Contaminant studies of wood storks were not undertaken
until after the cancellation of DDT; thus the effects of the
pesticide on reproduction during the time of peak DDT
exposure is unknown. The primary reasons given for its
recent listing are destruction and alteration of its feeding
habitat (Endangered Species Technical Bulletin, 1984).
Studies completed since the cancellation of DDT have
shown that wood stork eggshells are significantly thinner
than pre-pesticide era specimens (<1947) and that shell
thickness is negatively correlated with DDE-egg concentrations.
In 1973 (Ohlendorf et al., 1978), ten wood stork eggs were
collected from nests at Merritt Island National Refuge in
Florida. Egg contents contained 4.0 ppm DDE (geometric
mean, wet weight basis) and eggshells were 8.9 percent
thinner than eggs collected before 1947. Residues of DDE
were highest in wood stork eggs relative to those found in
eggs of 12 other species collected at the site. The correlation
of DDE in eggs with decreasing shell thickness approached
significance and was higher than for other contaminants
measured. In 1982, Fleming et al. (unpubl.) collected one
wood stork egg from each of five nests at eight colonies in
central and northern Florida. The previously studied
11-66
-------
Figure 11-10 Lake Apopka, Florida and environs (State of Florida Gama
and Fish Gcnmission 1982).
PUfMOlfTH
APOPKA-
BEAU CLAIR
CANAL
CITRUS
GROVES
GOURD —
HECK ^
SPRING
CTTRUS
GROVES
CITRUS
GROVES
MUCK*
FARMS
WONT-
VERDe
APOPKA
CA
MAGNOLIA
COUNTY
PARK
OC06E
WINTER
GARDEN
11-67
-------
Merritt Island site was included. DDE concentration in egg
contents ranged from 0.16 to 9.4 ppm with a geometric mean
of 1.6 ppm (wet weight). DDE was negatively correlated
with eggshell thickness (r= -0.48, P<^ 0.01). They also report
that DDE concentrations were higher in eqgs from nests in
which at least one egg did not hatch compared to residues
in eggs from nests where all eggs hatched. Flemming et al.
concluded:
"Our data suggest a possible link between DDE and hatching
success of Wood Stork eggs, particularily at DDE concentrations
present in earlier years.
"Thus one must not dismiss organochlorines, DDE in part-
icular, as possibly contributing to the poor reproductive
performance of Wood Storks during the past three decades."
The DDE residues affecting wood storks are probably of
many origins ranging from global atmospheric-borne DDE to
residual pre-cancellation DDT. Wood storks forage for fish
and other aguatic animals in waters that receive drainage
from citrus areas. Therefore dicofol must also be considered a
possible source. The dicofol source is of special concern
for the Merritt Island Refuge population, contract farmers
are permitted to tend citrus groves on the grounds of the
refuge (greater than 2500 acres) (Johnson, 1984). Refuge
records show that between 1979 and 1982 18,000 pounds of
dicofol were used at the site, which (by recent Florida
analysis of dicofol) indicates a possible local release of
approximately 1000 pounds DDTr (estimated from DDTr in sample
#546251, Table 11-26). Use of dicofol at the refuge has not
been permitted since 1982 based on concern over DDTr contami -
nation (Johnson, 1984). Dicofol applications to citrus near
in-land lakes such as Lake Apopka may also contribute to wood
stork DDE-exposure. As Ohlendorf et al. report, wood storks
fly as much as 125 km to obtain food during nesting periods.
Following nesting they disperse over an even greater area.
DDE has been shown to cause poor reproduction in bald
eagles and these effects have played a major role in their
population dynamics (Wiemeyer et al., 1984). Florida bald
eagles have been reported to be reproducing at 'near normal'
levels in recent years (Nesbitt, 1984). Nonetheless, the
estimated 350 pairs in Florida (Kale, 1984) remain on the
federal endangered list.
Wiemeyer et al. (1984) have summarized available bald
eagle egg-contaminant and shell thickness data for the period
1969-79. Their findings show that Florida bald eagles continue
to have hazardous concentrations of DDE in their eggs and
eggshell thinning sufficient to affect at least a portion of
the population. Correlating DDE-egg residue and nest productivity
data for all bald eagles in the U.S. indicated that when egg
residues are below 3 ppm (wet weight) reproduction is approximately
11-68
-------
normal and when residues are greater than 5.1 ppm DDE, productivity
drops remarkedly. Most of the egg residue values reported
since the
cancellation of DDT
(1972)
for Florida exceed
3 ppm.
Year
Site
DDE
DDD
DDT
a/
1975
Camp
Key
13
0.08
—
1976
Pine
Island
12
0.61
0.06
1976
Deer
Key
8.6
0.12
0.04
1977
Pine
Island
3.5
0.07
-
1977
Pine
Island
3.2
0.17
-
1979
Pine
Island
2.0
_
b/
1981
Fort
Meyers
4.9
0.47
-
b/
1983
Brevard County
1.6
-
-
a/ Data from Wiemeyer et al., 1984 except as indicated
b/ Wiemeyer, 1984
Wiemeyer et al. describe eggshell thinning in Florida
in the 1969-79 period as moderate (13 percent compared to pre-1946
samples). They note, however, that 20 percent of the Florida
eggs had severe thinning, i.e. greater than 20 percent.
Bald eagles in Florida occur in both marine and fresh-
water environments. Shallow eutrophic inland lakes (such
as Lake Apopka) that are near or adjacent to citrus production
areas, and thus that have a high potential to receive
dicofol drift or runoff, are used frequently by bald eagles
and other fish-eating birds such as ospreys (Nesbitt, 1984).
Peregrine falcons are not resident in Florida; however,
migratory peregrine falcons occupy habitat in or adjacent
to citrus growing regions in Florida (Figure 11-11). Thus
some DDTr exposure from dicofol may occur by consumption of
small birds (their principal food) that have acquired
residues in treated areas.
11-69
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PRESENT AND FORMER
WINTERING AREAS
Figure Ilall Peregrine falcon wintering areas (U.S. Dept. of Interior 1979A)
~ Present Wintering
Concentrations
!p Matogorda
Island
tPadre Island
Former Wintering and
Present Stop-over Areas
N
Pea Island
^LNWR
CapeHatteras
National Sea
shore
I
-------
C. EXPOSURE ANALYSIS
1. Introduction
The Agency prepared exposure calculations for the two
major dicofol use patterns—citrus and cotton. The Arroyo
Colorado waterway of southern Texas was chosen because of the
high level of dicofol used on citrus and the important aquatic
bird habitats in that drainage area. The Agency selected Kings
County, California, for the exposure calculations for cotton
because of the availability of use data for that area and
information indicating that Kings County is frequented
by winter migrations of waterfowl.
2. Exposure Analysis for Kings County, California
Cotton has historically been treated with dicofol at a
rate of about one pound per year. Exposure calculations for
Kings County are of two types. An overall mass balance
analysis was prepared to demonstrate the potential contribution
of dicofol use to the total DDTr loading of the county.
Additionally, the Agency prepared a specific aquatic exposure
an-alysis related to cotton cultivation in Kings County.
a. Kings County Mass Balance Analysis
In preparing the estimate of exposure in Kings County,
the Agency used the following assumptions.
1. Soil is by far the largest environmental sink for DDTr
and the fate of DDTr in the soil would determine the overall
dissipation rate in Kings County.
2. The dissipation half-life of DDTr in soils is seven
years (Lichtenstein et al., 1971).
This is not a true degradation half-life because volatil
ization of DDT from the soil accounts for much if not most of
the loss. Additionally, it is noted that longer (Buck et
al., 1983) and shorter (Beyer and Gish, 1980) dissipation
half-lives have been determined, and the seven year value
represents an intermediate estimate.
3. DDTr dissipates from Kings County according to first
order kinetics.
4. Apart from insignificant public health use and use of
existing stocks, DDTr soil loading due to the use of DDT
products ended early in 1972.
5. Dicofol is contaminated with DDTr at a level equal to
ten percent of that of the active ingredient.
6. Use on cotton accounts for all significant dicofol and
DDT use in Kings County.
11-71
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7. Dicofol is applied to cotton in Kings County at a rate
averaging one pound per acre.
8. Historically, DDT was applied to cotton at a rate
averaging 4.8 pounds per acre (Eckerman, 1984).
9. In the 60's there was an average of 77,500 acres of cotton
in Kings County and this climbed to an average of 275,000
acres in the 70's. DDT and dicofol were each used at a
constant annual rate from 1958 until 1970 (see assumptions #7
and #8). The Census of Agriculture (U.S. Department of Commerce,
1981) notes that the acreage of cotton in Kings County was in
the 250,000 range by 1978. The Agency assumes, for lack of
better data, that the cotton acreage increased linearly from
77,500 acres to 250,000 in the period of 1971 to 1978 and
that it has remained constant since that date and will remain
at that level in the future.
b. Results and Conclusions
The results of the mass balance analysis demonstrated
that, using reasonable estimates of DDTr dissipation rates and
reasonable estimates of the past, current, and future use of
dicofol and DDT, dicofol could be a significant contributor to
the current and future DDTr contaminant levels found in Kings
County soil, water and biota. Specifically, by 1984, the
Agency estimates that the total loading of DDTr in Kings
County due to DDT use could reasonably be estimated to be
about 850,000 pounds versus an estimate of 200,000 pounds due
to the use of dicofol (see Figure 11-12). By the year 2000, it
is estimated that the total loading of DDTr in the county
could reasonably be expected to fall to 220,000 pounds of
DDTr if dicofol were terminated versus a lowering to 450,000
pounds of DDTr if the uses were maintained (see Figure 11-13).
In other words, by the year 2000, environmental DDTr residues
may be twice as high if dicofol use continues than they would
be if its use was terminated.
3. Aquatic Exposure Assessment for Flooded Fields in
the Old Tulare Lake Basin, Kings County, California
During the late fall and winter, flocks of waterfowl
migrate to the San Joaguin Valley. During this period, most
of the cotton fields of Kings county are flooded in an agricultural
practice called "preirrigation" (Sutherland, 1984).
Euliss (1984) indicates that chironomid midge larvae and
other invertebrates in the preirrigated fields of Kings County,
California may provide important sources of forage to wintering
waterfowl. The exposure to these forage organisms would
presumably be highest during years when the cotton fields
have been planted with alternate crops such as grain which
would tend to be more attractive to foraging waterfowl. In
calculating the aquatic residue level of DDTr in the waters
of the flooded fields, the Agency made the following assumptions:
11-72
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DDT-r 30
Loading
in
100,000 lbs.
20
I
"-J
U>
10
58
Acres of
Cotton
pigure 11-12
—i—
60
70
77,500
—r~
80
Gradual
Increase
77,500-250,000
Relative Contributions of
DDT and Dicofol to the
DDT-r Loading of Kings Co., Calif
(1958-1984)
DDT-r Contribution due to
DDT
r~
84
DDT-r Contribution due to
Dicofol
Held Constant
at 250,000
-------
DDT-r
Loading -
in
100,000 lbs
5-
1-
1984
Figure 11-13 DDT-r Loading to King? County
With and Without Dicofol Cancellation
(1984 to 2000)
DDT-r Loading Without Dicofol Cancellation
4~\
LDDT-r Loading With Dicofol Cancellation
-------
1. Cotton is planted for three consecutive years followed
by four years of other crops.
2. Dicofol is applied only to the cotton.
3. The rate of dicofol application is one pound per acre.
Two applications are made during one of the years in a three
year series and only one application is made during each of
the other two years.
4. The first application is made when the cotton foliage
covers less than 50 percent of the field and the second
application is made when the canopy covers the field.
5. The amount of pesticide reaching the ground immediately
after application is proportional to the canopy cover (Willis,
1984). An additional ten percent reaches the ground subsequently
due to dry and wet fall (U.S. Department of Agriculture, 1980).
This yields 60 percent soil interception on the first application
and 10 percent interception on the second.
6. The soil half-life of DDTr is seven years (Lichtenstein,
1971) .
7. The field is flooded to a depth of two feet.
8. The field is plowed to a depth of one foot prior to
flooding and all pesticide is free to exchange with the
water column.
9. The cotton plant is disced into the soil in the fall,
but no significant loading is contributed because the half-life
from plant surfaces is relatively short (Bailee et al., 1970).
a. Calculation Methodology
To calculate the aquatic residue, DDTr loadings due to
dicofol soil were accrued over a 16-year period considering the
effects of interception by the cotton plants and dissipation.
In the sixteenth year, the soil residues are partitioned to
the water column assuming equilibrium between the water
column and the disced, top two inches of soil.
b. Results
On the basis of fundamental physical-chemical principles,
it is estimated that sixteen years of dicofol use could result
in 70 parts per trillion (ppt) of DDTr in the water column of
preirrigated fields (Hitch, 1984).
In a flow-through laboratory study, Derr and Zablick (1972),
using treatment levels in the range of the Agency's calculated
exposure, demonstrated that the Chironomus midge could be
expected to bioaccumulate DDE 20,000 fold above the aquatic
11-75
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concentrations. A 20,000 fold bioaccumualtion factor would
give rise to an estimate of 1.4 ppm DDTr (wet weight) in the
chi ronomids.
As an example of the possible exposure to peregrine
falcons and bald eagles by waterfowl, the Agency used the
example of a one kilogram duck. It is reasonable to assume
that the ducks would feed heavily for about two months on
the chironomids in flooded fields which had recently been
cultivated in cotton (Euliss, 1984). The biological half-life
of DDTr in large waterfowl is long (Longcore and Stendell,
1977; and Haegele and Hudson, 1974). The Agency therefore
assumes that the amount of DDTr eliminated or metaboli zed by
the ducks within 60 days would be insignificant. The total
accumulation during this period would be equal to the typical
food consumption of a duck (assumed to be 200 grams per day)
multiplied by the chironomid contamination level (1.4 x 10~6):
60 days X 1.4 xl0~® X 200 grams = 0.017 grams DDTr
Dividing the 0.017 grams by the reasonable estimate of an adult
duck's weight (1 kg), one would estimate that the total body
residue of the duck would reach 17 ppm. The Agency would not
project that overwintering ducks feed exclusively in flooded
cotton fields, but cotton culture and dicofol use is so
extensive in Kings County that it is reasonable to assume
that ducks feed in DDTr contaminated fields frequently enough
to drive their body burdens above the reproductive levels
which have been indicated for sensitive raptors. The dietary
effect level for the peregrine falcon may be as low as 0.1 ppm
(wet weight) (Pruett-Jones, 1981), while analysis of prey species
of bald eagles experiencing eggshell thinning were generally
below 0.3 ppm DDE (Wiemeyer et. al., 1978).
4. Arroyo Colorado EXAMS Model
Because fish-eating birds may be exposed to residues of
DDTr exceeding dietary levels known to impair reproduction,
the Agency developed a model to estimate the level of DDTr
residues in water resulting from the use of dicofol (Hitch
and Reinert, 1983). The simulation relies upon the Exposure
Analysis Modeling System (EXAMS). The Arroyo Colorado waterway
of southern Texas was chosen because of the high level of
dicofol used on citrus and the important aquatic bird habitats
in the drainage area. Under the conditions of steady-state
chemical loading, this model predicts the equilibrium concent-
ration in a water body. Although there are various uncertainties
associated with the use of mathematical simulations to describe
environmental processes, the use of this model is believed to
be an appropriate tool to estimate exposure to aquatic environ-
ments. The chemical input to the river system was estimated
based on the following assumptions:
1) The amount of dicofol used each year in this drainage
basin is 100,000 pounds. This is based on the estimate of
25,000 acres of citrus with drainage into the Arroyo Colorado,
11-76
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and the estimate that up to four pounds of dicofol active
ingredient are used once per year on citrus. Using the
highest label rate for a single application may partly compensate
for the legal use of multiple applications at less than the
maximum rate.
2) For purposes of this simulation, the water in the
river basin was assumed to be free of DDTr prior to the
introduction of contaminated dicofol, which yields the
EXAMS steady state concentration. Even though it is documented
that background levels of DDTr occur ubiquitously throughout
the environment, this assumption is necessary to calculate
the DDTr burden in fish that results solely from the use of
dicofol.
3) The amount of DDTr added to the environment was
assumed to be ten percent of the dicofol active ingredient
applied. Ten percent is approximately the average DDTr
content of currently registered technical products. The
model's residue predictions are a direct linear function of
the loading so that aquatic residues for any level of product
contamination can be estimated by proportionality.
4) The physical characteristics of DDT and DDE vary
slightly and the modeling capabilities required the choice
of one set of chemical parameters. From a calculation
standpoint, counterbalancing factors mitigated the importance
of choosing the physical properties of DDT or DDE for the
purpose of aquatic fate modeling to predict the eventual
concentration of DDE precursors in fish (Hitch and Reinert,
1983). For the EXAMS model, the physical parameters for
p,p'-DDT, the most extensively studied analog, were used
throughout the simulation and the environmental exposure
assessment.
5) The Agency assumed that most of the DDTr reaching the
Arroyo Colorado was transported by surface water running
off the immediate drainage area in which dicofol had been
used. A recent review of the available literature (Wauchope,
1980), pesticide runoff concluded that DDT consistently shows
long term losses of two to three percent of the amount applied.
Therefore, two percent of the DDTr applied was assumed to
reach the Arroyo Colorado as a consequence of surface water
runoff.
Using these assumptions, EXAMS predicted a steady
state water column concentration of 9 parts per trillion
(ppt) DDTr. Fish bioaccumulation factors have been estimated
to be over l,000,000x (Reinert, 1970). The Agency, therefore,
estimates that fish residues (total body wet weight) of 9
ppm might be expected. These DDTr residue levels in fish
exceed dietary levels shown experimentally to reduce eggshell
thickness. Effects on avian reproduction have been documented
experimentally at dietary levels as low as 0.6 ppm DDE (wet
weight). Monitoring studies of brown pelicans have indicated
11-77
-------
reproductive effects at lower dietary concentrations.
Because some of the constituents of DDTr are known or
expected to degrade to DDE, the Agency concludes that the
residue levels of DDTr in fish which would result from
currently registered dicofol products pose a significant
risk to certain species of birds.
11-78
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D. POTENTIAL HUMAN HEALTH EFFECTS
1. Oncogenicity of Dicofol and DDTr
As indicated in the Position Document 1, the Agency is
concerned with the oncogenic effects of the DDTr contaminants
of dicofol and found that studies of dicofol per se were un-
acceptable because of uncertainties about the composition of
the test material. The Agency has reexamined the tests done
to confirm the composition and finds little basis for concluding
that the test material was other than technical dicofol.
Steps are underway to establish the validity of the NCI
studies as representative of technical dicofol. Additionally,
because substantive new information on the oncogenicity of
DDTr has been generated since the Agency's last review (EPA,
1980), the Agency has undertaken a thorough review of the
oncogenic data base for dicofol and its DDTr contaminants,
namely DDT, DDE, and DDD. The purpose of this review is to
reassess the weight of evidence for carcinogenicity and to
provide appropriate measures of oncogenic potency for the
chemicals so that a more reliable risk assessment can be
conducted. The data base for dicofol and DDTr under review
includes experimental studies of the following species.
Mouse - Four multigeneration and six single generation
Rat - Nine single generation
Hampster - Two single generation
Dog - One four-year study
Monkey - Four, up to 12 years in the Rhesus monkey
A human epidemiological study is also under review.
The positive effects found in these studies have mainly
involved both benign and malignant liver and lung tumors in
the mouse. Mouse iiver tumors are also associated with
chronic exposure to technical dicofol and some of the other
DDTr analogs and the significance of these for risk assessment
is under review.
Included in the weight of evidence review are numerous
reports dealing with the genotoxic effects of DDTr. The role
of DDT as a promoter of carcinogenesis is also under review.
2. Human Toxicity of Alternatives to Dicofol
A synopsis of the toxicological data base for the major
alternative miticides is provided in Table 11-28. Chlorobenzilate
is oncogenic and, as a result of the Rebuttable Presumption
Against Registration process in 1979, its use was restricted
11-79
-------
Table 11-28
Toxicity Data Base fear Alternatives to Dicofol/Kelthane
Pesticide
Pivotal Data
Data Gaps
Basis for ADI
Toler ance/%ADI
COTTON USE
Sulfur
CAS # 812
CFR 180.2
Proparqite
(Qmite)
CAS # 1301
CFR 180.259
GRAS list
Acute oral LD50 > 3000 mg/kg (HDT)
Mjtagenicity: not on auxotrophic mutant of
E Coli
Oncogenicity: one year dermal, mouse NOEL
50 mg/mouse/day
2 Yr feeding, dog NOEL > 900 ppm (HDT)
2 Yr feeding, rat NOEL > 900 ppm (HDT)
3 generation reproduction, rat NOEL> 300 ppm
(HOT)
18 mo. oncogenicity, mouse NOEL> 1000 ppn
(HDT)
Teratology, rat N0EL> 105 mgAg/day (HDT)
Teratology, rabbit N0EL> 10 mg/kg/day (HDT)
None
Mitagenicity data
Metabolism data
Not established
Material is on
the GRAS list
CFR 180.2
Dog, feeding
NOEL = 900 ppm
Tolerance = 0.1 ppm
(cottonseed)
r n
% ADI
= 5.0 ppm
(oranges)
= 11.22
Cyhexatin
NOT APPROVED FOR COTTON SEED
Monocrotophos
(Azodrin)
CAS # 377
CFR 180.296
Teratology, rabbit NOEL > 2 mg/kg/day (HOT)
3 generation reproduction, rat NOEL = 2 ppm
2 year feeding, rat NOEL = 10 ppm
2 year feeding, dog
ChE NOEL =1.6 ppm
Systemic NOEL = 100 ppm
Mutagenicity
a. Dominant lethal, NOEL > 4 mg/kg (HDT)
b. Host mediated assay, weak mutagen high
concentration (5mg/ml)
c. Chromosome assay, NOEL > 4 mg/kg (HDT)
Metabolism data
Oncogenicity data
Dog, feeding
NOEL = 1.6 ppm
Tolerance = 0.1 ppn
% ADI = 18.79
-------
Table 11-28 (continued)
Toxicity Data Base for Alternatives to Dicofol/Kelthane
Pesticide
Pivotal Data
Data Gaps
Basis for ADI
Tolerance/%ADI
Methyl Parathion
(parathion)
CAS # 372
CFR # 180.121
Teratology, rat NOEL > 6 mg/kg/day (HOT)
Teratology, mouse (ip) NOEL > 60 mgAg (HOT)
Mutagenicity, mouse chromosome aberrations
NOEL = 1100 mgAg (ip)
90 day feeding,dog NOEL = 0.3 wg/kg/day
Oncogenicity, mouse not carcinogenic
Oncogenicity, rat, not carcinogenic
(FR vol 44 #103 pp 30448, 5/25/79)
Note: New chronic rat data; toxicity to
eyes (50 ppm); Tox. Branch may propose
Special Review.
Carbophenothion See Citrus Use
Chicarcbenzilate See Citrus Use
CITRUS USE
Metabolism data
Mutagenicity data
Rat, older
NOEL = 1 ppm
Tolerance =
1.0 ppm
(citrus)
0.75 ppm
(cotton seed
% ADI = 191.88
Oxythioquino
(Mar est an)
CAS # 576
CFR # 180.338
Propargite
Ethion
CAS # 427
CFR 180.173
Teratology, rat NOEL > 750 ppm (HOT)
3 generation reproduction, rat NOEL = 60 ppm
2 year feeding, dog NOEL = 50 ppm
Neurotoxicity, chicken NOEL > 5 mgAg (HOT)
2 year oncogenic, rat NOEL = 12 ppm
(Only dose tested)
Several studies on rat show liver toxicity
See Cotton Use
Teratology, rat NOEL > 2.5 mg/kg/day (HOT)
Teratology, rabbit NOEL =0.6 mg/kg/day
LEL =2.4 mg/kg
(fused sternabrae)
Feto/maternotoxicity NOEL = 0.6 mgAg
Feto/maternotoxicity LEL =2.4 mg/kg
(increased resorptions/1 ewer body weight)
Mutagenicity data
Metabolism data
Oncogeneitity data
Rat NOEL 60 ppm
(3 mgAg)
Tolerance = 0.5 ppm
% ADI = 2.41
Oncogenicity data
Reproduction data
Mutagenicity
Subchronic neurotoxicity;
Hen
Human NOEL 0.1 mg/kg
Tolerance = 2.0 ppm
% ADI = 128.83
-------
Table 11-28 (continued)
Toxicity Data Base for Alternatives to Dicofol/Kelthane
Pesticide
Pivotal Data
Data Gaps
Basis for ADI
Tolerance/%ADl
Carbophenothion
CAS # 165
CFR # 180.156
50'
Fenbutalin oxide
(Vendex/Mit icide)
CAS # 481DD
CFR 180.362
Cyhexatin
(Plictran)
CAS # 884A
CFR # 180.144
Mutagenic
a. Ames NOEL 20,000 mg/plate
b. yeast reccwbination NOEL 1000 ppm
ChE Inhibition, Human
NOEL plasma = 0.05 mg/kg/day
NOEL RBC = 0.15 mg/kg/day
Acute neurotoxic Hen, positive 1900 mgAg (LOT)
3 generation reproduction, rat NOEL = 10 ppn Acute dermal LD
2 year feeding, dog NOEL < 5 ppm rabbits
(INCOMPLETE STUDY) Acute inhalation LC 59
Metabolism, rapidly excreted into urine rats
Acute delayed neurotoxicity NOEL = 330 mg/kg Primary eye irritation
Primary dermal irrita.
Teratology, 2 species
Chronic feeding, rat
Oncogenicity, 2 species
Mutagenicity, 3 tests
Teratology, rat NOEL > 60 mgAg (HOT) Metabolism data
Fetotoxic NOEL > 60 mgAg (HOT)
Mater not ox. NOEL = 30 mgAg/ LEL = 60 mgAg
Teratology, rabbit NOEL > 10 wg/kg/day (HOT)
3 generation reproduction, rat NOEL = 50 ppm
18 month Oncogenic, mouse NOEL 100 ppm
2 year feeding, dog NOEL = 5 mgAg/day
2 year oncogenic, rat NOEL > 600 ppm
Metabolism, rat; mostly excreted unchanged
Primary eye irritation, extremely irritating
3 generation reproduction, rat NOEL = 12.5 ppm Metabolism data
3 generation reproduction, rabbit Mitagenicity data
NOEL = 3 mgAg/day (HOT) Oncogenicity data
2 year oncogenic, rat NOEL > 6 mg/kg/day (HOT) No NOEL for dog feeding
Mutagenicity, AMlS NOEL = 2 mg/plate (< 0.75 mg/kg/day)
Dog, NOEL = 0.125 mgAg
Tolerance = 0.20 ppm
(cotton seed)
=2.0 ppm
(citrus)
% ADI = 77
Rat, NOEL = 5 mgAg/day
Tolerance = 20 ppm
% ADI = 71.33
Rat, older
NOEL = 12 ppm
Tolerance = 2 ppn
% ADI = 89.15
-------
Table 11-28 (continued)
Toxicity Data Base fotr Alternatives to Dicofol/Kelthane
Pesticide
Pivoted Data
Data Gaps
Basis for ADI
Tolerance/%ADI
Chiorobenzilate
CAS #
CFR #
434
180.109
2 generation reproduction, rat
rproduct ion NOEL = 100 mgAg (HOT)
Systemic NOEL = 30 rag/kg
2 year feeding, dog NOEL = 500 ppm
Oncogenic, mouse NOEL far males NOT
reported, increased tumors males
3200 ppm (LOT), no effect females
USE LIMITED TO CITRUS
Reproduction, Dog, feeding
Teratology data NOEL = 12.5 mgAg
Mutagenicity data Tolerance = 5 ppm
(citrus)
= 0.5 ppm
(cotton seed)
% ADI = 9.36
M
W
I
00
w
-------
to citrus with provisions for protecting workers from excessive
exposure. The results of data on the remaining alternative
miticides do not meet or exceed the risk criteria of 40 CFR
162.11.
E. RELATIVE ECOLOGICAL HAZARDS OF DICOFOL ALTERNATIVES
A synopsis of the ecological data base for the major
alternative miticides is provided in Table 11-29. None of
the alternatives (for which data exist) is more chronically
toxic, bioaccumulative, or persistent than dicofol and its
DDTr contaminants.
11-84
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Table 11-29
Comparative Acute Toxicity of Dicofol and its Alternatives
to Certain Non-target Organisms.
Acute Ttoxicity1
Fish
Birds
Aquatic
Inverts
Chemical
ICso (PE*0
LDqn (neAg)
LC™ 4640
3401
0.09
Sulfur
>180
—
> 5620
> 100
M. Parathion
3.7
8.21
90
0.00014
Oxythioquinox
—
—
—
—
Fenbutat in-oxide
0.0017
> 2000
—
—
Cyhexatin
0.0037
300
195
0.00017
Ethion
0.210
45
> 5000
0.000056
Carbophenothion
0.013
121
320
0.0012
Chlorobenzilate
0.7
—
—
0.6
Methidathion
0.002
—
543
0.007
Monitor
25
10
42
0.026
1- Data are from EBB files and are for techmical materials.
References can be supplied upon request.
11-85
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Table 11-30
Comparative Chronic Toxicity and Fish Bioconcentration Factor3 of
Dicofol and some of its Alternatives to Certain Non-target Organisms.
Chronic Tbxicityl (ppn)
Chemical/^CF
Avian
Fish
Aquatic Invertebrates
Dicofol
3,700 + 800
DDT/DDE*
72,000
Methyl Parathion
Mallard duck
EL > 5
Black duck
NEL < 0.6
Mallard duck
EL > 15
Bobwhite quail
EL > 15
Fathead minnow
0.019 > MATC < 0.039
Fathead minnow
0.0005 > MATC < 0.002
Rainbow trout
NEL < 0.08
amphipod
0.019 > MATC < 0.039
daphnia
NEL < 0.00001
daphnia
0.167 > MATC < 2.51
Cyhexatin
Bobwhite quail
EL > 20
Monitor
>2
Bobwhite quail
3 > NOEL < 5
Mallard duck
EL > 715
Azodrin
1.3-2.8
Mallard duck
EL > 3.0
Bobwhite quail
EL > 1.0
1- Data are from EEB files and are for technical material. Reference
can be supplied upon request.
11-86
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F. ANALYSIS OF REBUTTAL COMMENTS
1. Comments on Exposure
Rohm and Haas has provided a statistical analysis (linear
regression) of DDTr fish-residue data (National Pesticide
Monitoring Program) with respect to temporal trends (1969-82)
and trends related to dicofol sales in certain states. They
conclude from their data that DDTr residues generally declined
in the period 1967-81 in major dicofol use states. Also they
report no general correlation of dicofol sales with DDTr fish
residues. Overall, they conclude, "The data do not support
the hypothesis of a correlation between use of dicofol and
DDTr residues in fish."
Upon review of these arguments, the Agency concludes
that Rohm & Haas has not rebutted Agency concerns over dicofol
use contributing to DDTr residues in fish. This conclusion is
based on the following findings.
(1) Correlation of DDTr in fish with dicofol sales data
presumes fluctuations in use may result in corresponding changes
in fish residues. This condition might occur only in very
local high dicofol-use areas (e.g., such as the Arroyo Colorado
drainage in south Texas where the Rohm and Haas analysis
found residues had not significantly declined and a correlation
between residues and dicofol sales exists [p.ll]). It is
unlikely that broadly scattered ambient residue monitoring
stations such as are used in the NPMP would often include small
areas where dicofol use controlled or dominated fish DDTr
trends. In terms of broad trends in ambient DDTr residues,
the Agency believes that prior use of DDT is likely the major
contributor to past and present residues. Hence, it is
understandable and expected that DDTr residues as measured by
NPMP have, for the most part, declined in the interval 1969-82
and that they do not generally correlate with dicofol sales
data. However, this decline and lack of correlation does not
rebut the fact that dicofol will contribute significantly to
DDTr loading in the environment.
(2) DDTr residues in the environment have likely resulted,
in large measure, from past DDT use. Currently, new DDTr is
added to the environment in small amounts relative to past
use. New DDTr may come from global transport, dicofol and other
sources such as illegal use. Elimination of the major source
(DDT cancellation) has resulted in a dissipation of ambient
residues followed by a period of slow decline or stabilization.
The current sources become more important through time, and
the general decline levels off when input to the system
eguals the residues lost from the system by transport or
degradation. A key issue is whether dicofol use will cause
local or regional residues to stabilize at levels that may be
ecologically harmful. The Rohm and Haas rebuttal does not
address this issue. It is significant that the most recently
11-87
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published analysis of NPMP fish data (Schmitt et. al., 1983)
notes that "Results for 1976-1979 continued to illustrate the
effectiveness of the 1972 ban on the use of DDT in the United
States. Residues of the most persistent DDT homolog (p,p'-DDE)
declined after 1974, but appeared to stabilize by 1976-77."
2. Comments on Risk
The ecological toxicity of DDTr is firmly established
and the registrant's rebuttal has not attempted to refute this.
Pesticide registrants bear the burden of demonstrating the
environmental safety of their registered uses. In this instance,
because the toxic effects of DDTr are generally accepted,
this may be done only by showing that dicofol will not significantly
contribute to DDTr accumulations that are hazardous to the
non-target organisms. This task is a considerable scientific
undertaking because not only must environmental residues be
described but also their long-term ecological effects delineated.
The Rohm and Haas submission does not rebut any of the basic
risk concerns.
3. Comments on Arroyo Colorado EXAMS Model
a. Comments Concerning Loading
Rohm and Haas submitted a report by Ketron, Inc. (Weeks,
1984) that commented on the EXAMS simulation of the Arroyo
Colorado (Hitch and Reinert, 1983). Using different loading
assumptions and alternative degradation parameters, Weeks'
comments argue that the loading of DDTr to the Arroyo Colorado
would be far less than the loading projected by Hitch and
Reinert. Furthermore, the Weeks analysis assumed that the
DDTr contamination of dicofol would be lower than the 10 percent
value assumed by the Agency.
b. Agency Response
The substitution of alternative chemical dissipation
rates does not appreciably alter the predicted water column
concentration. The reported values of DDTr degradation
found in the literature vary widely. Due to this variation,
the Agency, in an unpublished sensitivity analysis, multiplied
the degradation parameter values which had been selected by
one hundred fold. The predicted water column concentration
was not affected significantly.
Additionally, Weeks defends a smaller loading on the
basis of assurances from Rohm and Haas that the average
dicofol contamination level has recently been lowered. The
Agency agrees, of course, that loading estimates should
reflect product contamination levels which have been certified
for each manufacturer. The Agency selected a ten percent
contamination level. Fish residue levels can be prorated
from any product contamination level that the registrants may
submit. For example, Weeks used a contamination level of
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6.5 percent, which would result in a fish residue of approximately
6.5 ppm. As discussed earlier, this level of dietary exposure
has produced eggshell thinning (in the laboratory) and is
expected to cause adverse reproductive effects in a number of
avian species.
c. Comments Concerning Entrapment
Most Texas citrus farmers utilize flood irrigation. Water
is pumped onto the fields and held in place by earthen dikes a
few inches high. Weeks contends that these dikes are rarely
destroyed and that they would trap DDTr-contaminated sediments
and hold them on the field.
d. Agency Response
The Soil Conservation Service indicates that the Arroyo
Colorado has been subject to massive flooding at intervals of
approximately seven years. These floods destroy the retaining
levees with the result that the fields have to be regraded.
The DDTr compounds apparently persist to the extent that they
would be available for sediment-borne transport'during flooding
for years after they have been applied. The half-life of DDTr
in desert soils has been determined by Dr. George Ware at the
University of Arizona to be about 12 years. In his rebuttal,
Weeks presents data from a Mississippi Delta cotton study
(Willis et al., 1983) showing that, for a study period lasting
six years after the cessation of DDT use, the average annual
runoff was 1.29 percent of the typical yearly application rate.
At this time the weight of evidence indicates that DDTr will
persist in the soils and be available for transport by periodic
flood ings.
e. Comments Concerning Settlement
Weeks utilizes sediment delivery ratios to estimate that
82 percent of the DDTr leaving the citrus fields would permanently
settle out into the drainage canals before reaching the main
stem of the Arroyo Colorado. This diminished loading estimate
results partly from the entrapment of DDTr-laden sediments
behind irrigation levees.
f. Agency Response
The Agency finds that Weeks' assumptions concerning the
trapping of contaminated sediments in the drainage canals to be
inadeguately supported. Sediment delivery ratios are traditionally
utilized to evaluate sediment entrapment on fields. Without
specific information concerning the presence of catch basins,
or other obstacles to lateral movement, one would assume that
the amount of sediment entering the upstream end of an open
channel will, eventually, exit downstream.
Further development of the "canal entrapment" theory
could, at best, lead only to a geographic reassignment of
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loading (to the drainage canals) and development of the theory
concerning mounded fields would most likely support only the
assumption that loading would be small during a typical nonflood
year. These canals, like the main stem Arroyo Colorado, may
provide forage to sensitive wildlife, and, if the DDTr chemicals
are retained on mounded fields during some years, they would
presumably persist and accrue in the soil to be transported at
unusually high rates during flood years.
4. Other Comments Received
Other comments were received from various user groups
and agricultural extension agents. These comments were mostly
testimonial in nature in that they described the crops and acreage
treated and attested to dicofol's efficacy. No substantive
information was submitted that the Agency could consider in
its risk and benefits assessments.
Two environmental groups, the National Audubon Society
and the Natural Resources Defense Council, responded that
they support the Agency's initiation of the Special Review on
d icofol.
The U.S. Department of Agriculture submitted a draft
report to the Agency containing a survey of agricultural
extension agents. This report contained information on the
usage of dicofol as well as information on alternatives. The
report was used in the development of the Agency's benefits
analysis.
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G. SUMMARY OF DICOFOL AND DDTr EFFECTS
Based on the data reviewed, the following conclusions
were reached concerning the ecological risks posed by continued
use of contaminated dicofol:
1. The miticide dicofol is contaminated with DDT, DDD,
DDE, and Cl-DDT (DDTr). As indicated, a major concern has
been with the conversion of DDT to DDE and subsequent repro-
ductive effects in birds. Although the Agency does not have
adequate information on the environmental fate of Cl-DDT, it
assumes that this chemical is also a DDE precursor. Thus, use
of dicofol products will inevitably result in release of DDTr
into the environment with concomitant exposure of fish and
wildlife.
2. DDTr contamination levels in dicofol are variable.
Based on an estimated ten percent DDTr contamination level
yearly use of two million pounds of dicofol would release
200,000 pounds of DDTr. Given the persistence of these
contaminants, it is prudent to evaluate this pollutant-release
over longer time periods. Thus, another decade of use at
current rates and contaminant levels would indicate release
of two million pounds of DDTr. In view of the toxic effects
of DDTr, this is a significant and threatening amount of
toxic material.
3. Immediate and long term wildlife exposure to DDTr
will occur in areas where dicofol use is concentrated, e.g.,
citrus areas in Arizona, Texas and Florida, and on cotton in
California and Arizona.
4. There is an association between major dicofol use
areas and potentially hazardous levels of DDTr. Of particular
concern are Hidalgo County, Texas and Maricopa County, Arizona
where concentrated dicofol use (150,000 pounds per year and
70,000 pounds per year, respectively) is coincident with DDE
levels among the highest in the nation. Evidence also exists
showing ecologically significant DDTr residues in areas of
heavy dicofol use in California and Florida. Actual contributions
of dicofol to observed residues are not known.
5. Due to the mobility and persistence of DDTr compounds,
use of dicofol will contribute to exposures remote from the
site of application.
6. Though the majority of existing environmental
residues of DDTr is likely the result of applications of DDT
products, which ended in 1972, dicofol use would cause ambient
DDE levels to dissipate at a slower rate and to stabilize at
higher levels than if use were discontinued.
7. DDE residues are ubiquitous in fish in the United
States. NPMP monitoring indicates that concentrations of
the chemical declined immediately following the 1972 DDT
cancellation, but may have stabilized by 1976-77 (Schmitt et
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al., 1983). Concentrations in fish in many areas are near
or within the range believed to cause reproductive effects
in sensitive fish-eating bird species.
8. DDE residues are ubiquitous in birds in the United
States. Recent NPMP surveys and other monitoring studies
show that birds in many areas carry residues potentially
harmful to themselves or birds that might prey upon them.
9. Species of endangered wildlife sensitive to DDTr
inhabit regions where extensive dicofol use occurs. The
Office of Endangered Species (OES) has determined that
continued use of dicofol jeopardizes the continued existence
of the American peregrine falcon and the Arctic peregrine
falcon. OES recommmends cancellation of all dicofol uses for
this reason. The OES biological opinion also found that
continued use of dicofol may affect the brown pelican, wood
stork, and bald eagle.
10. There is evidence that some bird species, such
as California brown pelicans and bald eagles, once severely
affected by eggshell thinning and associated problems are
now in a period of subcritical effects. Some populations
are recovering. Any measurable level of eggshell thinninq
or other evidence of DDTr-effects in wild populations would
be ecological 'costs' that, in view of incomplete knowledge
of long-term conseguences, are considered potentially serious.
11. A preliminary avian feeding study with technical
dicofol indicates that DDE tissue residues in exposed bobwhite
birds exceed levels reasonably anticipated from product
contamination.
12. Field studies conducted since 1980 have shown
continuing DDE residues and eggshell thinning in American
peregrine falcons, bald eagles, black-crowned night herons,
black skimmers, and wood storks. Portions of studied bird
populations were located in dicofol use areas. The great
majority of bird species have not been studied.
In conclusion, the data reviewed indicate DDTr remains
a hazard to wildlife in the United States. Moderate to
high levels of DDTr exist in major dicofol use areas. Continued
use of this pesticide will contribute to these high levels
of DDTr and prolong these hazards to birds, fish, and other
organisms.
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III. BENEFIT SUMMARY FOR DIOOFOL
A. Introduction
Dioofol (010501) is a chlorinated hydrocarbon miticide (acaricide)
registered for use on a variety of agricultural crops as well as for
heme and garden uses to control a wide range of mite species. All registrant-
submitted production and marketing data concerning this miticide are regarded
as confidential business information. Recent OPP estimates indicate that
2.0-2.5 million pounds of dicofol active ingredient are applied annually to
registered sites in the U.S. Registered dicofol usage site groupings
include various small fruits, pome fruits, stone fruits, citrus, nut crops,
vegetables, field crops, ornamental plants, turf grasses, greenhouse crops,
house plants plus sites in and around domestic dwellings, and commercial
and agricultural buildings.
Annual usage for dicofol fluctuates widely fran year-to-year, since mite
populations do not necessarily reach economic threshold levels requiring
treatment of all crops or geographic areas every year. Usage estimates
developed in 1980 and 1981, which are based on late 1970's data, indicate
an annual usage estimate of approximately 2 million pounds active ingredient,
with as much as + 20% variation possible in any given year. Estimates
based on more recent data for many sites, indicate an annual usage level
ranging from 2.0-2.5 million pounds of dicofol active ingredient. Aside
from unpredictable increases in mite populations, this increase may be
partially explained by users deciding to apply dicofol in preference to
alternatives. This switch may be due to use restrictions which were imposed
as a result of regulatory action taken against chlorobenzilate or possibly
due to mite resistance developed to one or more alternatives.
The benefit analysis for citrus uses of dicofol was prepared by both
the Science Support Branch of the Benefits and Use Division, U.S.E.P.A.
and a cooperative agreement between the Economic Analysis Branch and Arizona
State University (Preliminary Benefit Analysis of Dicofol Use on Citrus,
1984). The benefit analysis for cotton use on dicofol and the remaining
benefit reviews including the following site groupings: seed crops, stone
fruits, pome fruits, hops, figs, vegetables, small fruits, tree nuts, mint,
ornamental plants, turf grasses, and heme and garden uses, were completed
by the Benefits and Use Division.
The alternatives to dicofol were evaluated on the basis of their fit
into the treatment schedule, guided by labeling statements such as the
preharvest interval; pre- or post-harvest restrictions; number, timing, and
frequency of application; reentry time; required safety equipment or
restricted applicator use; and pests controlled on which sites. Other factors
include comparative efficacy (degree of control), ccmpatability in mixtures
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with other pesticides, phytotoxicity, local resistance limitations, affect
on beneficials including pollinators (selective vs. broad spectrum pesticides),
and efficacy vs. temperature. Fran these and other factors, significant
benefits can be derived from the use of dicofol. These factors are not
readily quantified in monetary terms. However, they do influence a growers
selection of dicofol over other possible alternatives.
The economic impacts of using alternative miticides were estimated
using partial budgeting and comparative cost evaluation in the case of
cotton and citrus. This approach focuses on changes in control costs
with alternative miticides while holding all other inputs and their costs
constant for citrus. However, impacts on cotton production were further
analyzed in terms of yield and quality effects.
Most of the economic inpacts resulting from the cancellation of
dicofol will be felt by cotton producers in the San Joaquin Valley of
California. The total impacts experienced by U.S. cotton producers
would range between $9.6 and $31.9 million in the short-term (one
crop year), and between $11.0 and $37.1 million 1983 constant dollars
annually in the longer-term. Economic impacts to citrus producers are
expected to range from $3.5 to $4.0 million as a result of using more
expensive alternatives to dicofol. Should there be yield and quality
declines associated with the use of alternatives, inpacts to citrus
producers will be higher. Dicofol usage on cotton and citrus represents
approximately 67 percent of all the active ingredient applied annually
in the U.S.
The economic impacts relating to the cancellation of dicofol use on
all minor use sites has not been quantified to date. However, it is
estimated that production costs will increase from $1.1 to $1.4 million
for producers of apples, nuts (principally pecans) and mint, solely as a
result of using costlier alternatives. The remaining minor use sites are
likely to realize some level of negative economic impacts, the magnitude
of which is unknown at this time.
Insufficient data are available to allow EPA to determine the effects
of a reduction in the number and type (e.g., organophosphate, organo-tin,
chlorinated hydrocarbon) of effective miticides on pest resistance with
the cancellation of dicofol. Increased usage of the remaining miticides
could increase the potential for mite resistance to these chemicals by
increasing the selective pressure cm them. This could accelerate the
development of resistance and shorten the life of the remaining materials.
This and other benefits to IPM programs (e.g. reduction in number of
pesticide applications, selective control) and being able to tailor
pesticide reconvnendations to the existing circumstances of the season,
crop and mite species, as outlined previously, can be critical to maintaining
yield levels, and quality. There is no known method for nonchemical
control (e.g. removing weed hosts, use of predators, and parasites) to
reduce mite populations below economic thresholds. Normal sanitation
practices, such as weed control in fields, along field margins, and beside
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irrigation ditches are carried out and at tiroes have an effect, in
suppressing but not controlling mite population development.
EPA recognizes that the following review does not address certain
factors, in detail, which may affect the availability or usefulness
of alternatives. These include a pesticide not being available (sold) in
small packages, restricted use chemicals unavailable to haneowners, relative
efficacy against species in a mite complex, mite resistance, labeling
limitations, and relative cost effectiveness of dicofol vs. alternatives.
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B. Cotton
U.S. cotton production in 1981 reached a record high of 15.6 million
bales. Cotton producing acreage has tended to increase in the Southwest
and decrease in the Southeast. Between 1971 and 1981 the western cotton
production regions increased their share of U.S. cotton production from
44 to 73 percent, while increasing land area planted from 55 to 73 percent
of the U.S. total. The major cotton production states are Texas, California,
Arizona, and Mississippi.
Spider mites damage the cotton plant by sucking plant juices from the
leaves, status, and fruit. If not controlled, they can cause defoliation,
loss of plant vigor, yield reduction (lint weight) and shortening of the
staple length. High relative humidity and favorable plant growing conditions
tend to be unfavorable to the development of mite populations. Periods of
hot, dry weather, on the other hand, can trigger increases in mite populations
which can cause economic loss. Spider mites generally occur in small
numbers during the early part of the growing season in most cotton producing
areas. An important exception to this is the San Joaquin Valley in California
where cotton growers experience early mite outbreaks at economic levels
almost every year. In this area, dioofol is considered to be the only
available early season control for the strawberry spider mite, V a pest that
can cause yield losses in infested portions of cotton fields of up to 35
percent, with field wide losses of up to 7 percent, cannon.
The two possible alternatives for this early season mite control use
in the San Joaquin Valley, propargite and sulfur, must be ruled out because
propargite is phytotoxic to young plants and sulfur is not effective against
spider mites at temperatures below 95°F. Prolonged temperatures of 95°F+
generally do not occur during the early part of the growing season in the
San Joaquin Valley. Midseason or later infestations of the Pacific spider
mite and twospotted spider mite are controlled by applications of propargite
or sulfur.
Estimates of the number of acre-treatments^/ typically made nationally
with dicofol vary widely, ranging from 656.8 to 1,135.8 thousand per year.
At an assumed dosage of 1.2 pounds of active ingredient per acre, the
aforementioned values for acre-treatments inplies an annual usage of dicofol
ranging from approximately 0.8-1.4 million pounds. The San Joaquin Valley
accounts for over four-fifths (85.0 percent) of all dicofol acre-treatments
made to cotton, while the remainder of California, Arizona, the southeast,
and Arkansas account for 4.0 percent, 9.2 percent, 1.4 percent, and 0.4
percent, respectively.
1/ The twospotted spider mite and, to a lesser extent, the Pacific spider
mite can also build up at this time.
2/ A single acre may be treated more than once per season. Therefore, the
total number of applications equals the number of acre treatments
applied.
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In order to evaluate fully the economic irrpacts of the cancellation of
dicofol, an analysis was conducted with both a short and long-term perspective.
The short-term represents a best estimate of the market conditions which
will prevail in the cotton marketing season following the cancellation of
dicofol (i.e., August 1, 1985-July 31, 1986). As such, the short-term
estimate is based upon predicted (per an agricultural simulation model)
values for acreages, yields, and prices, starting with the present and
continuing through the second quarter of 1986. By contrast, the long-term
estimate is timeless (i.e., not specific to any given year), in that
acreages, yields, and prices (the latter in 1983 constant dollars) are
based upon long-term averages of de-trended time series data. Moreover, in
that the long-term estimate is cast in a comparative static framework, no
allowance was made for acreage shifts due to changing yields, costs, and
prices.
For the purposes of this analysis, it was assumed that in the absence
of dicofol, current users in the Southeast U.S. and Mississippi Delta would
switch to monocrotophos at no incremental cost, while those in Arizona and
California outside of the San Joaquin Valley would switch to propargite, at
an additional cost of $2.26 per acre-treatment. The aggregate increase in
treatment costs would range from $1.2-2.2 million, amounts which hold for
both the shortand long-term perspectives. These are only 'exanples of the
added costs that can occur, because other alternatives also exist. However,
dicofol remains one of a small group of cotton miticides that are needed
when IPM (integrated pest management) programs are implemented and a selective
miticide is required. Most of the others are broad spectrum miticide/
insecticides. The cost of pesticide development works against production
of new selective pesticides needed most in IPM.
In addition to incremental treatment costs, it is assumed that since
growers in the San Joaquin Valley have no effective alternative to dicofol
for early-season spider mite control, their crop would sustain a3-5 percent
loss in the quantity of lint, as well as some unknown reduction in quality
relating to staple length and strength. In the short-term, this loss could
range from $9.2-$29.7 million, depending upon the actual level of yield
losses. In the long-term, losses to San Joaquin Valley growers could range
from $10.7-$34.9 million 1983 constant dollars, again the precise amount
depending upon the yield reduction experienced. In this regard, it should
be noted that the yield-related impacts from cancellation are highly sensitive
for California, due to the fact that lint yields there are approximately
twice that of the national average.
When added treatment costs are combined with yield related losses, the
total impact from cancellation sustained by all current users of dicofol
could range from $9.6-$31.9 million in the short-term, and from $11.0-$37.9
million 1983 constant dollars annually in the long-term. In view of the
fact that cotton prices are presently declining concurrently with an
increased utilization of carry-over stocks, and given that the maximum
projected loss of lint due to cancellation (approximately 85,000 bales, at
480 pounds per bale) would, at most, offset the rise projected between now
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and mid-1986 in the latter ratio, it can be concluded that the prices faced
by the consumers of cotton products most likely would rise only slightly or
not at all. ^Moreover, assuming an unchanged target price of $.81 per pound
for 1985/86, -and an average lint price of 63.2 cents per pound, the Federal
Government would be able to reduce its budgetary outlay for deficiency
payments to San Joaquin Valley growers by an amount ranging frcm $4.4-57.3
million, the precise amount depending upon the yield losses sustained. It
should be recognized that this amount represents neither a net welfare loss
nor gain but rather a transfer of wealth frcm users of dicofol in the San
Joaquin Valley via the Federal Government to all taxpayers.
In view of the foregoing considerations, it can be concluded that
nearly all of the impacts of the cancellation of dicofol would be borne by
San Joaquin Valley cotton producers who typically account for 10-12 percent
of total U.S. cotton acreage or 20-25 percent of the production. While
even the maximum impact shown above amounts to only about 1 percent of the
total value of cotton produced annually (valued at farm-level prices), the
average effect on San Joaquin Valley producers would be to increase their
long-run average break even cost by 5.6 percent, from $.837 to $.884 per pound
of lint. Given that the long-term average real price of cotton received by
California growers is $.852 per pound, it can be seen that the cancellation of
dicofol would most likely result in sate portion of these producers being
forced into the production of relatively less profitable crops than cotton.
As noted above, this issue was not explored in the present analysis.
However, it should be noted that even if a substantial shift out of cotton
occurred in the San Joaquin Valley, the current national base acreage (in
excess of 15 million acres) is at a level which would permit growers in
other areas to fill the supply gap and still be in compliance with the
current USDA cotton support programs.
C. Citrus
In 1977, dicofol was the fourth ranked citrus miticide (in treated
acreage) accounting for 9% of the total acre-treatments with these chemicals.
It was estimated at that time that there were approximately 260,000 acre-
treatments of dicofol on citrus involving over 500,000 pounds a.i. (active
ingredient) of dicofol. By 1980 the estimated usage of dicofol on citrus
was 1.1 million pounds, indicating that usage had doubled between 1977 and
1980. This may be partially accounted for by regulatory restrictions
imposed on the use of chlorobenzilate and yearly fluctuations in mite infestation
levels.
Current usage estimates for dicofol on citrus indicate that approximately
587,000 pounds a.i. are being applied in 290,000 acre treatments in the
major citrus producing states: Arizona, California, Florida and Texas.
Ihis marked decrease in the quantity of dicofol applied between 1980 and
the present may be indicative of the variation in severity of mite infestations.
The majority of dicofol use on citrus occurs in Florida, 73 percent by
weight. Texas, California and Arizona account for 17, 8 and 2 percent
respectively of the remaining citrus use of dicofol.
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Mite infestations on citrus crops can reduce tree vigor and growth,
thus reducing fruit quality and/or yield. Reduced profits may result from
lower quality or lower yields caused by use of less efficacious alternative
pesticides and/or frcm higher costs associated with the use of alternative
pesticides. Citrus production is oriented toward either fresh fruit or
processed fruit. Mites that affect fruit finish can be tolerated to a
greater degree in fruit for processing than crops for the fresh fruit
market. This can result in fewer control treatments for processing fruit.
In general, it is thought that there would not be any significant citrus
yield or quality reductions resulting from a shift to alternative miticides.
Alternatives to dicofol are listed by state below.
Arizona
California
Florida
Texas
cyhexatin*
hexakis*
ethion
propargite*
oxythioquinox
propargite*
hexakis*
cyhexatin*
hexakis*
chlorbenz ilate*
ethion
propargite*
carbophenothion
hexakis*
ethion + oil
formetanate-
hydrochloride
These alternatives are not necessarily as efficacious as dicofol for
controlling all mite species in the various citrus-producing areas. Those
with an asterisk (*) are selective acaricides, as is dicofol. The others
are broad spectrum pesticides (miticide/insecticides). Additional review
could better evaluate how these miticides fit into the various treatment
programs in view of the preharvest interval, frequency of application
allowed, phytotoxicity, restricted use, reentry limitations, mite complexes
present, IPM needs, temperature limitations and/or cornpatability in spray
mixtures.
There are eleven economically important mites and a number of less
significant species attacking citrus in the U.S. Arizona, California, Florida
and Texas and also individual regions within these states all have a unique
primary mite complex plus those of secondary importance. The different
species vary in the degree to which they attack the foliage, fruit, and/or
new growth. These mites develop at varying times in the season, overlap
with other species on the trees and are more easily controlled by one or
more miticides than others.
All four states recommend dicofol. It is efficacious against a larger
number of mite species than other miticides. Dicofol does not control the
citrus bud mite, but is one of only two or three pesticides effective
against the broad mite. Dicofol does not have temperature limitations or
cause phytotoxicity problems, it is corpatable with most pesticides in
mixtures and is an unrestricted use pesticide with no reentry limitations.
It fits well into IPM programs because it is relatively safe to most beneficial
organisms unlike the broad spectrum miticide/insecticides. Mite resistance
to dicofol has been minimal, over the years whereas many of the organcphosphates
and others have been rendered ineffective after a few years of use.
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The minimum economic impact associated with the cancellation of dicofol
use on citrus crops is expected to be between $3.5 and $4.0 million annually.
This would be the result of using costlier alternatives to replace the
current citrus uses of dicofol. The aggregate dollar impact of dicofol
cancellation is expected to be less than 0.02 percent of the value of
annual U.S. citrus production. Insofar as there are resulting yield and
quality declines resulting from the shift to alternative controls, impacts
will be higher.
D. Minor Uses
The following benefit reviews are brief evaluations of the importance
of dicofol use as a miticide on minor use sites. These sites include:
alfalfa and clover seed crops, caneberries, figs, grapes, hops, hone and
garden (non-commercial uses), mint, nuts, ornamental and turf (commercial
uses), pane fruits, stone fruits, strawberries, and vegetables. These
crops are attacked by many species of spider mites, eriophyid mites, and
others. Crops vary in their susceptability to mites, and the importance of
mites vary with the region and season. In general, spider mites are more
likely to build up in mid to late season, during hot, dry years, and tend to
damage stressed plants more than those growing under normal conditions.
The state reoormendations of selected states were reviewed, and the possible
alternatives listed for the major mite pests of each crop. Other pesticides
in registered products for use on these sites (U.S. EPA, PPIS)V have not
been reviewed. Little is known about the current levels of resistance of
these mites to the mi ticides reviewed. There are more broad spectrum
materials cited than selective miticides such as dicofol. As a result, the
latter are more likely to be used as alternatives for dicofol.
The estimated losses presented in these benefit reviews represent only
increased cost for treatment and control of mites using potential alternative
pesticides and do not reflect additional impacts related to labeling
limitations, chemical phytotoxicity of alternatives, other yield and quality
effects, and losses due to the development of mite resistance to the
remaining miticides. In general, the non-monetary benefits cited under
citrus and cotton are applicable to these sites as well.
Alfalfa and Clover Seed Crops
Alfalfa is a perennial crop grown for seed throughout the U.S. but
production is concentrated in the western states. Hie highest yields are
realized in that area because growing conditions approach the ideal:
moderately moist soil and low relative humidity along with warm, sunny
weather and abundant pollinators during bloom and warm, dry weather to
hasten ripening of the seed. Approximately 430 thousand acres of alfalfa
3/ PPIS = Pesticide Product Information System.
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were harvested for seed in 1982. An estimated 40 percent of the alfalfa
seed crop acreage and 80 percent of the seed production in the U.S. is
located in California, Washington, Oregon, Nevada, and Idaho. Approximately
20 percent of that total alfalfa seed acreage is located in California.
Dicofol is used on alfalfa seed crops for control of spider mites
(e.g. carmine, Pacific, strawberry, twospotted). Spider mite infestations
in July can seriously reduce yields, but those occuring later in August
usually do not. In Washington, overwintering spider mite populations can
be reduced and controls minimized by applying dinitrochloro-IPC in April to
control weeds. Various use estimates indicate that 30 to 40 thousand acres
(7-9 percent of the U.S. total) of alfalfa grown for seed are treated with
dicofol annually. Three probable alternative miticides are in state recomen-
dations with propargite used most extensively. Formetanate-hydrochloride
is also recommended, but it is not normally used to control spider mites
because it has a prebloom restriction. Progargite and formetanate-hydrochloride
are both more expensive per acre treatment than dicofol.
Clover is a perennial crop grown for seed throughout much of the
United States. Clover is attacked by a ccnplex of spider mite species
similar to that on alfalfa. They are most likely to cause damage during
hot, dry periods when the crop is under moisture stress. Nearly 320
thousand acres of all types of clover were grown for seed in 1979 with
red clover being the most cormon variety. An estimated 35 percent of the
U.S. clover seed acreage is located in California, Oregon, Washington and
Idaho. As in the case of alfalfa, the growing conditions and abundant
pollinators in these and other western states are conducive to high
yields.
Available information indicates that very little clover grown for
seed is treated with dicofol. It appears that dicofol is applied to an
average of 1,000 acres (about .3 percent of the U.S. total) annually.
Information was not available as to usage of the other recommended miticides,
but propargite and oxydemeton-methyl are listed by USDA as providing
satisfactory and fair levels of control, respectively. Demeton, mevinphos,
and sulfur are also recommended.
Blackberries, Dewberries (Boysenberries and Loganberries) and Raspberries
The economic inpact resulting from am immediate cancellation of
dicofol usage on blackberries, raspberries, and dewberries (boysenberries,
and loganberries) would generally be limited to minor grower level impacts
localized primarily in Washington, and Oregon. Available information on
usage is inconplete and subject to wide variation, but dicofol appears to
be the pesticide of choice nationally. The major mite pests are the
dry berry mite and several species of spider mites in the west and the
spider mite species elsewhere.
It is estimated that dicofol usage on these sites is less than 10,000
lbs. a.i. annually. Since multiple applications may be necessary, total
III-9
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base acres treated would likely represent a small portion of the U.S.
acreage. USDA (1984) indicates treatments on 325 acres with 100 more
acres "treated occasionally."
If dicofol is unavailable, growers would most likely select oxydene ton-
methyl for spider mite control. Its use is limited to one application per
year; it has localized resistance problems, and a 48 hour reentry time.
Cyhexatin, demeton, diazinon, mevinphos, and oxydemeton-methyl are listed
in recommendations but have labeling restrictions that make them of limited
use (e.g. post-harvest use only, pre or postblocm use). For dryberry mite
control, lime sulphur appears to be the principal alternative to dicofol,
but it is caustic and disagreeable to apply. Diazinon is toxic to bees
and, therefore, cannot be applied during bloom. It also appears to have
efficacy and resistance problems.
At present, comparative efficacy data are not available for dicofol
and the other miticides; therefore, estimates of yield impacts could not be
estimated. However, the other chemicals available have problems with
efficacy, pest resistance and label restrictions which limit their usefulness,
therefore, it can be expected that yield and quality will be reduced and
production costs increased.
Hops
Approximately 78.6 million pounds of hops were grown on nearly 40
thousand acres in 1982. Hops are produced primarily in Washington with
nearly 71 percent of the U.S. acreage and 74 percent of the total
production. Hops are also produced in Oregon, Idaho and California. The
total value of U.S. hops production in 1982 was approximately $138 million.
Hops are produced on long-lived, perennial vines, grown on trellises.
The most coimon spider mite attacking hops is the twospotted spider mite.
The Pacific spider mite and strawberry spider mite are also listed as
pests of hops.
Dicofol is annually used on 3 to 4 thousand acres of hops to control
spider mites. Several possible alternative miticides are available, including
phorate, disyston, naled, cyhexatin, sulfur, parathion and methyl parathion.
Dicofol falls approximately in the middle of the range estimated for total
treatment costs on a per acre basis. Information on the extent of usage or
effectiveness of alternatives was not evaluated.
Pigs
About 99 percent of the U.S. fig acreage and production is located
in California. Florida, South Carolina, and Texas are minor producers.
Agricultural Census data (1978) indicate 16,879 acres of fig trees in the U.S.
In 1982, fig production totaled 38.3 thousand tons with a value of $10.3 million
(fresh basis).
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At least three species of spider mites attack figs, but they are usually
not a major pest problem for fig producers. Dicofol is registered for use
on figs to control spider mites, but it is seldom used and it has had
resistance problems in the past. Propargite is the material of choice,
because of superior efficacy and fitting into the IPM program better, even
though it is somewhat more expensive per acre than dicofol. Carbophenothion
is considerably less expensive on a per acre basis than either miticide,
but it is a broad spectrum material and has resistance problems. Another
possible alternative is superior oil but it is of limited use and effectiveness.
Strawberries
An estimated 39,450 acres of strawberries valued at about $422
million were harvested in the U.S. during 1982. California produced over
70 percent of the crop on about 28 percent of the U.S. strawberry acreage.
Other states with significant cortmercial production include: Florida,
Oregon, Washington, Michigan, North Carolina, New Jersey, New York,
Ohio, Pennsylvania and Wisconsin. The remaining states have some strawberry
production for either heme, market garden or pick-your-own operations.
Dicofol is used to control spider mites on at least 3,000-6,000 acres of
commercial strawberries. An additional unknown quantity of heme and pick-
your-own acreage is also treated, but this could not be estimated with
available data. The total quantity of dioofol usage on strawberries is
probably less than 10,000 lbs. a.i. annually.
Only carbophenothion, cyhexatin, and propargite of the eleven chemicals
registered for use on strawberries against the numerous species of spider
mites are considered to be suitable alternatives. However, cyhexatin and
propargite are phytotoxic to some strawberry varieties and this has resulted
in yield losses of up to 20 percent. Carbophenothion is not a choice in an
IPM program, because of its affect on beneficial organisms. Resistance to
it in the Pacific Northwest is a localized problem. Five others appear to
be possible alternatives to dicofol under limited conditions: demeton,
ethion, hexakis, oxydemeton-methyl, and propargite. Comparative performance
data for these chemicals are not available. Current data suggest that
efficacy, label restrictions and cost will combine to increase mite control
costs in infested areas. In the aggregate, a cancellation of dicofol on
strawberries is not expected to have severe economic effects at the regional
or national levels. This conclusion is supported by the relatively minor
extent of usage and the availability of other chemicals.
Ornamentals and Turf (commercial)
In 1978, dicofol sales amounted to an estimated 30% of the total sales
value of miticides used on ornamentals. Since then, dicofol usage has been
increasing steadily. The probable current usage exceeds the 30% market
share noted above.
Estimates of usage of dicofol on ornamentals is 270 thousand pounds
a.i. per year. This represents 9.7% of total dicofol usage. Turf usage
III-ll
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only represents 2.9% of total dicofol usage or 80 thousand pounds a.i.
In a report prepared under contract to EPA, 1981, national usage of dicofol
by Pest Control Operators in the urban environment was estimated at about
29,000 to 39,000 a.i. lbs.
There are scores of ornamentals and many more species of mites that
attack them than for any agricultural crop. Dicofol usage is nationwide.
The number of miticides that can be used overall probably exceeds the 32
listed by USDA, 1984, but for any given site/pest situation the possible
alternatives can be very limiting. An analysis of this complex group of
sites will entail considerable review.
State recommendations for use of dicofol and registered alternatives
on lawns, turf and ornamentals are presented in a USDA survey of state
extension entomologists (USDA, 1984). Of the alternatives listed in a USDA
report, generated from the aforementioned survey, for use on ornamentals,
only dimethoate is recommended as having satisfactory performance without
being too restrictive or too expensive. No alternatives were recommended
for dicofol use on lawns.
The need to control mites on the different turf grasses varies throughout
the U.S. Florida recommends diazinon for Bermudagrass mite control.
California lists dicofol and diazinon against spider mites and eriophyid
mites, and Ohio and West Virginia list dicofol, diazinon and chlorphyrifos for
clover mite control. Only dicofol is a selective miticide. Georgia,
Illinois, Indiana, Louisiana, Maryland, New York, North Carolina, and
Washington did not cite mites on turf as a problem in their reoommendations.
Other miticides in registered products for use on turf have yet to be
evaluated.
A qualitative assessment of the impact of cancellation of dicofol
indicates that there would probably be a significant impact on both
ocmnercial ornamental and turf sites, since alternatives do not appear to
be fully satisfactory from a cost, efficacy, toxicity or next-target organism
perspective.
Mint (peppermint and spearmint)
The 1983 USDA Agricultural Statistics (USDA, 1983) indicates that
peppermint is a ccitmercial crop in Idaho, Indiana, Oregon, Washington and
Wisconsin, and spearmint is ccratiercially grown in Idaho, Indiana, Michigan,
Oregon, Washington and Wisconsin. In 1981, the Pacific Northwestern states
produced 86 percent (Idaho 488,000 lbs.j Oregon 2,470,000 lbs.; and Washington
647,000 lbs.) of the total U.S. peppermint oil and 82 percent (Idaho 177,000
lbs.; Oregon 150,000 lbs.; and Washington 1,459,000 lbs.) of the total U.S.
spearmint oil. The remaining mint oil is produced in the Midwest.
Mint is a perennial crop that requires a 15 hour day length for
maturation and maximum oil production. It, therefore, cannot be grown
commercially below the 41st parallel.
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Dioofol is registered for control of the twospotted spider mite on
mint (peppermint and spearmint). Heavy infestations of the strawberry
spider mite and the twospotted spider mite can result in decreased quality
and yield of mint oil. In the Midwest, mites are not a significant problem
on mint. The weather conditions in the Midwest, the fact it is grown on
muck soil, and that growers irrigate regularly prevent serious mite problems.
Occasionally, during unusually high temperatures and/or dry weather conditions
sporadic mite infestations occur. Spider mite problems occur frequently on
mint grown in the Pacific Northwest, and dioofol is the primary miticide
used there. If a mite problem should occur on mint in the Midwest, dicofol
is the miticide most frequently recommended. Approximately 12,000-20,000
pounds a.i. of dicofol are applied annually to an estimated 10,000-18,000
acres of mint in the Pacific Northwest. The amount applied and the number
of acres treated fluctuates dramatically from year to year depending on the
severity of the spider mite problem. There has been little or no dicofol
applied to mint crops in the Midwest during the last two or three years.
Propargite is the most likely alternative to be used in the Pacific
Northwest if dicofol is cancelled. Propargite is effective and is currently
used alternately with dioofol. Dicofol has a longer residual effect than
propargite and controls mites more quickly. Growers alternate these chemicals
to prevent mites from developing resistance to either pesticide. Dicofol
is applied if mites occur early in the season. If mites occur or re-occur
later in the season, propargite is usually applied.
Oxydemeton-methyl is registered for control of the twospotted spider
mite on mint in the Midwest, but is only registered for the strawberry
spider mite on mint in the Pacific Northwest. Oxydemeton-methyl has a
shorter residual effect than dicofol and often requires two applications.
Depending on the time interval, late applications of oxydemeton-methyl
can cause phytotoxicity.
Cancellation of dioofol for control of the spider mites on mint could
cause short-run economic hardship to some gr ewers in the Pacific Northwest
due to higher pesticide costs. In Idaho, the product cost of dicofol
ranges from $8.50-$12.75 per acre while propargite ranges fran $14.50-$26.60
per acre (USDA, 1984). Similar cost differences would be expected in
Oregon and Washington. Based on the estimated treated area, total production
costs would increase by as much as $250,000 annually. Economic losses
may also result from decreased yields in the early season caused by spider
mite damage that occurs in the time it takes propargite to take effect.
Certain growers may adjust by growing a different crop (most likely wheat
in the Pacific Northwest), in order to reduce economic losses. Mint growers
are concerned that continued use of propargite alone will lead to the
development of resistance by mites. Propargite and dicofol appear to be
the only effective miticides currently available for mite control on mint.
Heme and Garden (non-commercial)
Dioofol is the most widely used miticide on hane and garden sites*
The home and garden sites include various vegetables, small fruits, pome
II1-13
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fruits, stone fruits, citrus, tree nuts, ornamental plants (trees, shrubs,
annual and perennial bedding plants, and greenhouse and house plants).
Dioofol is registered to control many mite species; all of which can cause
aesthetic, as well as yield losses. EPA estimates that roughly 60,000-
80,000 pounds a.i. of dicofol are used on heme and farm sites annually.
There are other chemicals registered for control of mites on home and
garden sites: for instance, chlorpyrifos, diazinon, dimethoate, disulfoton,
endosulfan, malathion, oil, oxydemeton-methy1, and sulfur. There are many
more mite species on the array of ornamental plants than on any agronomic
crop or group of crops. No acaricide can be considered a replacement for
all uses of dicofol. Dimethoate is one of the more efficacious alternatives,
but it requires protective clothing to use which makes it of limited suitability
to the homeowner. Others have a very limited spectrum of activity on mite
species and some other miticides tend to suppress mite populations rather
than control them thereby requiring repeated applications. USDA indicates
that users are concerned with or limited by toxicity, formulation, package
size and types, non-target pest problems (destroying beneficial insects),
phytotoxicity, resistance, restricted uses and expense with respect to the
alternatives. Most importantly, no one chemical appears to have as broad a
spectrum of control as dicofol in terms of the number of species of mites
controlled on as wide a variety of sites. Gardeners are not often aware of
what pesticide controls an individual species of mite nor are they able to
identify them. Therefore, they prefer an all-purpose miticide like dicofol.
Cancellation of dicofol will result in increased control costs for home
and garden sites, because the alternatives are slightly more expensive.
Costs will also increase since users will likely purchase more than one
pesticide depending on the specific mite problem they face and/or the
site they are trying to treat. Sane users may be reluctant to cope with
the problem. This could result in monetary losses in the form of the
replacement costs of damaged plants and shrubs, or the market value of lost
produce from vegetable gardens. The most important factor to the homegardener
is the pleasure of having fresh, quality produce and/or aesthetically
pleasing, healthy, decorative gardens and cut flowers.
Nuts
Dioofol is registered for the control of several species of mites on
chestnuts, filberts, hickory nuts, pecans and walnuts. There are several
spider mites that feed on chestnuts in the U.S. where production is very
limited. USDA recommends dicofol, ethion, or malathion against them.
Filberts are grown primarily in Oregon. Dicofol is the only miticide
recomended for control of the occasional outbreak of spider mite species.
The filbert bud mite is not effectively controlled by dicofol. Data are
not readily available cm the limited U.S. conroercial hickory nut production.
English walnuts are attacked by the walnut blister mite and several species
of spider mites. California is the principal U.S. producer of walnuts. In
addition to dioofol; carbophenothion, phosalone, and propargite are in
products registered for use against spider mites on walnuts. Other possibilities
111-14
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are ethion or dioxathion, but propargite is the material of choice against
spider mites on this crop.
The only nut crop where there appears to be any significant dioofol
usage is on pecans. Pecans are primarily grown in the Southeast (Alabama,
Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina)
and the Southwest (Arkansas, New Mexico, Oklahoma, Texas). Mites are
seldom a problem on pecans in the Southwest, but sporadic mite outbreaks
do cause economic losses in the Southeast.
There are several species of spider mites that can attack pecans
including the pecan leaf scorch mite. Heavy populations, of this mite,
cause defoliation from the lower branches upward. Defoliation results in
failure of the trees to bloom well the next spring, followed by a poor
nut crop.
Approximately 50,000-75,000 pounds a.i. of dicofol are used annually
on 10-17 percent of the pecan acreage in the Southeast (primarily Alabama,
Florida, Georgia, and South Carolina).
In addition to dicofol, USDA recommends the following chemicals for
the control of mites on pecans: aldicarb (Southeast only), azinphos-methyl,
calcium polysulfide, carbophenothion, deneton, diazinon, dimethoate, EPN,
ethion, parathion, malathion, and sulfur (USDA, 1982). Dicofol and
hexakis are the primary miticides used on pecans in Georgia and Alabama.
Overall dicofol is more effective, and it is faster acting than hexakis.
As a last resort, Alabama growers will use demeton and carbophenothion.
Dimethoate was the primary miticide used on pecans in Louisiana until last
spring. However, mites have begun to develop resistance to dimethoate,
and growers have switched to dicofol and to seme extent hexakis. In
addition, there has also been some use of wettable sulfur in Louisiana.
Hexakis is the most likely alternative to replace dicofol. However,
growers in the Southeast appear to have little confidence in the alternative
or are reluctant to pay the higher prices entailed. The per acre chemical
ooet of hexakis is $17.00-$17.50 corpared to $12-$15 per acre for dicofol.
Substituting hexakis for dicofol would increase production costs of
pecans $2.00-$5.50 per acre. Total production cost of dicofol treated acreage
in the Southeast could increase as much as $260,000 annually.
Vegetable Crops
Dioofol is registered for use on a number of vegetables for control
of mites. The major use sites are beans (snap, lima, succulent, and dry),
eggplant, melons, peppers, cucumbers, squash, and tomatoes). Dioofol
is used to treat 4 percent of the bean acreage, 5 percent of the eggplant
acreage, 14 percent of the melon acreage, up to 3 percent of the pepper
acreage, about 1 percent of tomato acreage and up to 10 percent of the
cucumber and squash acreage.
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The principal mite pests of vegetables are the spicier mites, including
the carmine, desert, Pacific, sixspotted, strawberry, tumid and twospotted
spider mite. Their importance varies with the mite species, distribution in
relation to where the crop is grown, their biology, host range, and many
efficacy and resistance factors. Spider mites are primarily foliage feeders
that reduce plant vigor and yield. In addition to spider mites, the tomato
is attacked by the foliage feeding tomato russet mite which can cause
defoliation and loss of grade, when exposure causes sunscald on the fruit.
Spider mites tend to be sporadic problems on vegetables. Usage figures are
low compared to major crops with serious mite problems, however, when
outbreaks occur, control is necessary.
The following is the estimated annual U.S. dicofol use on vegetables.
Site Acres planted Acres treated Pounds applied
(a.i.)
beans
1,916.5
80
65
cucumber &
198.8
1 to 20
1 to 20
squash
eggplant
5.9
0.3
0.5
melons
330.0
45
40
peppers
63.9
2
3
tomatoes
396.5
4
16
Preliminary indications are that a number of possible alternative
materials are available and used for mite control. Dicofol has the
advantages of being lower in cost, having a longer residual activity than
primary alternative materials and is one of the few miticides without
broad spectrum activity.
A review of the states which consider these vegetable crops important
and provide recommendations, indicates that dicofol is generally listed
alone or with several other pesticides to control spider mites and/or the
tomato russet mite depending upon the crop. As with other crops, various
limitations and considerations such as phytotoxicity, preharvest interval,
toxicity level to applicators, pest spectrum present, and costs are important
in determining whether there are any or several alternatives available for
a given set of circumstances.
The following list gives a brief overview of the state reoonmendations
for mites:
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States that States that Dicofol Number of
Crop List Mites Recommend Listed Other Pesticides
as a Pest Dicofol Alone Listed by States
beans
4
of
5
3
—
12
cucumbers
11
of
13
10
—
11
eggplant
9
of
11
3
—
10
melons
12
of
14
12
—
13
peppers
8
of
19
8
—
6
pumpkins
7
of
9
6
2
5
tomatoes
14
of
17
14
—
11
squash
7
of
11
7
3
7
All the pesticides tabulated above, other than dicofol and sulfur on beans,
are broad spectrum materials. No information has been reviewed to attempt
to categorize the resistance picture for miticides used on vegetables.
Contents submitted to EPA by USQA indicate that chlorpyrifos, diazinon,
and malathion are not as effective as dicofol on all crops listed.
Carbophenothin, ethion, naled, parathion, oxydemetort-methyl, and sulfur
were not as effective on one or more of the crops listed.
The possible alternatives to dicofol appear to include: (1) beans -
carbophenothion, demeton, endosulfan, and oxydemeton-methyl; (2) cucumbers -
dimethoate, carbophenothion; (3) eggplant - carbophenothion and demeton;
(4) melons - carbophenoth ion and demeton; (5) peppers - carbophenoth ion
and demeton; (6) pumpkin - carbophenothion and dimethoate; (7) tomatoes -
carbophenothion and demeton; and (8) squash - carbophenothion and
dimethoate. None of the alternatives are selective miticides and their
use would result in problems for IPM programs.
The information available indicates that the overall loss of dicofol
use on vegetables would not create serious problems for the producer.
Those producers currently using dicofol would have increased production
costs due to the higher cost of alternative materials and an increased
number of chemical applications for satisfactory mite control.
Grapes
Ccnmercial grape production is concentrated in California with 93%
followed by Washington and New York with 2.4% each. Other states producing
grapes commercially include Michigan, Pennsylvania, Arizona, Arkansas,
Ohio, North Carolina, Georgia, Missouri, and South Carolina. Hie three
grape species grown are Vitus vinifera (mostly west coast), Vitus labrusca
(concentrated in the northeast) and Vitus rotundifolia (in the south).
Although there is a grape bud mite, grape erineum mite and grape rust
mite, the major mite pests of grape are the spider mites (four principal
species), against which most of the miticide use is directed.
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In all, about 30,000 to 50,000 of the 762,500 acres of U.S.
grapes are treated with dicofol. Each area has unique mite problems:
California has the Pacific spider mite and twospotted spider mite; Washington,
the McDaniel spider mite; and the Northeast has the twospotted spider
mite and European red mite.
Of the nine pesticides listed in state recommendations for use against
spider mites on grape, hexakis and propargite are the primary alternatives
to dicofol. Dimethoate and phosalone may also be useful. The five remaining
active ingredients plus several others listed by NPIAP (USDA) or the PPIS
listing appear to have major limitations when oorpared to dicofol.
The major usage area for dicofol against spider mites is in New York.
Additional indications are that propargite is preferred for mite control
under the growing conditions in California and Washington. Dicofol,
dimethoate and hexakis appear to be the next most desirable. In the northeast,
dicofol is preferred with hexakis and phosalone as the best alternatives.
Dicofol appears to be preferred when spider mites are the only significant
problem and the grower needs a material with residual action. Growers who
have spider mite problems in conjunction with insect pests would probably
utilize a broader spectrum material to control the pest complex (e.g.
carbophenothion, dimethoate, ethion, phosalone).
A preliminary examination of the loss of dicofol indicates that
severe financial impacts to grape growers are not expected. The shift to
alternative materials would result in the use of more expensive controls
and having to apply these materials more frequently, since the alternatives
have limited residual activity. More review is necessary to compare the
possible alternatives to the various field conditions and pest populations,
at least in the major grape production areas.
Pcme Fruits
Dicofol is registered for control of apple rust mite on apples and
spider mites on apples, pears, quinces, and crabapples. The principal
spider mite species on pcme fruits include the following: brown mite,
European red mite, McDaniel spider mite, Pacific spider mite, Schoene
spider mite, twospotted spider mite, Willamette spider mite, and yellow
spider mite.
Among pcme fruits, apples represent by far the most important use of
dicofol, with pears a distant second. No acreage or dicofol usage data
on quinces and crabapples were found, therefore, only apples and pears
will be considered in the following analysis.
Apples
While apples are grown throughout the continental United States, the
USDA routinely reports production statistics for only thirty-five states.
In teems of volume, however, apple production is geographically concentrated.
The three leading states, Washington, New York, Michigan, ranked in
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descending order of importance, accounted for approximately 60 percent of
total apple production in 1983.
Dicofol is used against the apple rust mite and the spider mite
conplex which varies with the state or region and the season. There are
at least eight spider mite species that can be a pest problem, each with
its own biology, behavior and response to chemical control.
The correlation of labeling restrictions, the pest complex, and
field conditions to the possible alternatives for dicofol are critical.
In the evaluation process, we must consider the well established apple
IPM programs, utilizing the limited number of selective miticides as
opposed to the broad spectrum materials is an important consideration.
The dormant/delayed dormant oil application is inportant to any mite
control program on apples. However, oil only controls those mites over-
wintering on the host (e.g. European red mite) and not those that overwinter
on cover crops, etc. (e.g. twospotted spider mite). Rotation of miticides
among their various classes (e.g. organophosphate, organo-tin, chlorinated
hydrocarbon) is necessary to slew the development of resistance to any
one or all of them.
Dicofol fits well into early season spider mite control programs
because it is relatively safe to most beneficial insects. Though moderately
to highly toxic to the predatory mite Amblyseius fallacis, dicofol has
minimal inpact if applied early because these overwintering mites don't
start moving up the tree until early spring through the post-bloom
stage. Late season applications of dicofol can disrupt the predatory
mite populations and cause a resurgence of spider mite populations.
However, because of its quick action and residual effects, dicofol is
reccmended in IPM programs when other miticides and predatory mites
have failed to keep spider mites below economic threshold levels.
Among the registered alternatives to dicofol, the most widely used
is cyhexatin. Recently, dicofol has been gaining in the market share
relative to cyhexatin, due to the observations of growers and extension
experts that mites have become resistant to the latter chemical, especially
in the State of New York. The best available estimate of current annual
dicofol usage on apples nationally ranges from 120,000-180,000 pounds of
active ingredient or 40,000-60,000 treated acres. This estimate assumes
an average of two applications per season at a rate of 1.5 pounds a.i.
per acre. Although the foregoing estimate of acres treated is substantially
less than that suggested by USDA, it is consistent with industry submitted
sources.
Should dicofol be cancelled for use on apples, the resulting inpact
would be an increase in annual production co6ts, ranging frcm $0.6-0.9
million. This estimate assumes that the alternative miticides; cyhexatin,
propargite, and formetanate-hydrochloride would afford a level of control
equivalent to that of dicofol. While it has been widely stated that
various species of mites have become resistant to cyhexatin, it is also
generally acknowledged that apple growers have encountered similar
problems with dicofol, propargite and hexakis.
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Given that the increased production costs cited are miniscule in
comparison to the total farm-gate value of apple production (approximately
$850 million in 1983), it is unlikely that the cancellation of dicofol
would result in a reduction of the national supply of either fresh or
processing apples; and as a corollary, consumer prices (excepting for
possible localized fresh-market situations) would be unaffected. For
those growers currently using dicofol, however, the impact of cancellation
on a per-acre basis, estimated at approximately $14, might contribute to a
per-acre net revenue loss as high as 3-5 percent. Because dicofol usage
has recently increased significantly in New York, it would be reasonable to
conclude that a substantial portion of the $0.6-0.9 million cost increase
cited above would be borne by producers of that state.
Pears
While the 1978 Census of Agriculture reports pear production in nearly
all of the forty-eight continental states, roughly 95 percent of the total
1983 crop was produced in the three states of Washington, California and
Oregon, ranked in descending order of importance. According to USDA, over 7,000
acres of pears are treated with dicofol, but only in Minnesota, New York, and
Oklahoma. By contrast, an industry source reported that less than 1,000 acres
were treated in 1979. The same industry source, while updating its apple
estimate to 1983, felt it unnecessary to do so for pears. Other data
sources indicate that dicofol is used only sporadically on pears.
Mites became abundant in dry, hot weather. Pear orchards that are
not irrigated are most likely to be affected. The five most common plant
feeding species of mites found on pears are the European red mite, twospotted
spider mite, pear rust mite, McDaniel spider mite (Washington) and the pear
leaf blister mite. The latter species is not controlled by dicofol.
Mites on pears should be controlled because low numbers of mites can
cause foliage injury and the pear rust mite and the pear leaf blister mite
cause direct fruit damage.
Dicofol is used on pears, albeit only minimally. With the information
presently available, it is impossible to determine whether this dicofol
usage reflects a price advantage, a superior mode of action, or both in
certain localized situations. Overall, the impact from the cancellation of
dicofol would have only negligible impacts on pear supplies and prices.
Stone Fruits
Dicofol is registered for the control of mites on the following
stone fruits: apricots, cherries, peaches/nectarines, and plums/prunes.
USDA has reported that approximately 91,000 pounds of active ingredient
are used to treat about 51,000 acres. As was the case with pears, this
estimate greatly exceeds those fran industry sources. The Agency has
estimated the combined total usage of dicofol on peaches/nectarines and
cherries to be approximately 6-7 thousand acre-treatments, accounting
111-20
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for 9-14 thousand pounds of active ingredient. Use of dioofol on plums/prunes
would appear to be negligible, presumably reflecting the fact that mites
are not a serious problem on this crop.
Based on the fact that dioofol accounts for only a small percentage of
the miticides used on peaches/nectarines, it can be concluded that its
cancellation would have relatively little impact on either producers or
consumers, on the other hand, dicofol accounts for a significant share
of cherry miticide market. Cancellation of dicofol use on this site might
result in market inpacts.
Apricots
Although apricots are grcwn widely throughout the United States,
virtually all commercial production occurs in Utah, Washington and
California with the latter accounting for approximately 97 percent of
U.S. production. Data from California indicate that less than 40 pounds
a.i. of dicofol were used on apricots in 1982. No other usage information
on this site is currently available.
At least eight species of spider mites (e.g. European red mite,
twospotted spider mite) and two ericphyid mites (peach silver mite, plum
rust mite) attack apricots.
Feeding of the eriophyid species can affect the vigor of the trees,
and cause silvering of foliage, defoliation and reduction of fruit size
and quality. The spider mites affect plant vigor by extracting plant
juices and yellowing foliage, reducing fruit size and quality.
Possible alternatives to dicofol include propargite and endosulfan
for the peach silver mite and plum rust mite. For spider mite control,
propargite, and cyhexatin are the alternative selective miticides listed.
The broad spectrum pesticides include phosalone, azinophos-methyl, demeton,
ethion, methiocarb, and oil.
Cherries (sweet and tart)
Major states for sweet cherry production (79 percent combined) include
Wcishington, Oregon, California, and Michigan in descending order. Michigan
produces over 75 percent of the tart cherries followed by New York with
9 percent.
Mites attacking cherries include the: brown mite, European red mite,
McDaniel spider mite, Pacific spider mite, Schoene spider mite, twospotted
spider mite, Willamette spider mite and yellow spider mite. The eriophyid
mites include the cherry rust mite, peach silver mite and plum rust mite.
Effect on the trees are similar to that on apricots. The cherry rust
mite bronzes foliage, but is generally not a problem in bearing orchards.
Dicofol accounts for a significant share of the acaricides applied
to cherries. This cancellation might result in market impacts for cherries.
II1-21
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Possible alternatives for spider mite control in the Northwest, as specified
in the USDA handbook include: hexakis and propargite among the selective
acaracides and azinphos-methy1, oil, methiocarb, parathion and ethion from
the broad spectrum pesticides. Recent California recormendations were
unavailable. Fruit specialists in Michigan feel that there is no suitable
alternative for dicofol. New York lists carbophenothion, malathion and
parathion along with dicofol for a post-harvest application. For the
plum rust mite, only endosulfan is recommended.
Nectarines/Peaches
Peaches are produced conroercially in about two-thirds of the states.
However, California produces almost all of the clingstone and 30% of the
freestone varieties, followed by South Caroline (23%), Georgia (9%), New
Jersey (6.5), and Pennsylvania (6%).
Virtually all the commercially produced nectarines are produced in
California. Nectarine production is about l/30th of that for peaches.
The spider mite species and eriophyid mites attacking peaches and
nectarines are generally the same as those on apricots and cherries,
except for the cherry rust mite.
Dicofol is one of the principal miticides applied to peaches. Data
on nectarines is lacking. The recortmended selective miticides which
are possible alternatives to dicofol include cyhexatin, hexakis, formetanate-
hydrochloride, and propargite. The broad spectrum materials include oil,
carbophenothion, azinphos-methyl, malathion, mesurol, methiocarb, oxydematon-
methyl, demeton, ethion, endosulfan, and phosalone. Most of these are
also contained in products registered for use on nectarines.
Plums/Prunes
California is the principal grower of plums with production about
twice that of Oregon, Washington, Michigan and Idaho which produce appreciable
amounts of prunes and plums combined. Of the approximately 60,000 tons
grown annually in those four states, production on a percentage basis
is Oregon (48%), Washington (23%), Michigan (18%) and Idaho (10.5%).
There are at least six spider mite species (brown mite, European red
mite, McDaniel spider mite, Pacific spider mite, Schoene spider mite and
twospotted spider mite as well as two eriophyid mites (the peach silver
mite and plum rust mite) which are pests on plums. Plum rust mites can
cause leafrolling and fruit russeting. Spider mites cause yellowing of
the foliage and together they can reduce tree vigor and therefore fruit
size and quality.
For plum rust mite, endosulfan, wettable sulfur and hexakis are
possible alternatives. Alternatives for spider mite control include:
propargite, ethion, hexakis, cyhexatin, oil, azinphos-methyl, demeton,
and parathion.
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IV. DEVELOPMENT OF REGULATORY OPTIONS
A. INTRODUCTION
As previously explained, FIFRA mandates the Agency to
weigh the risks against the benefits for the uses of a pesticide
in order to determine whether continued registration would
cause unreasonable adverse effects on the environment. In
Chapters II and III, the risks posed by exposure to dicofol
and the benefits derived from its registered uses have been
discussed. To determine whether continued registration of
dicofol is appropriate, the Agency has identified a number of
regulatory options, and has evaluated each option for its
impacts on both sides of the risk/benefit eguation.
In addition, the Agency has identified available alternative
pesticides for the various uses of dicofol. The general
risks of alternative pesticides have been evaluated based on
the available data.
This section identifies the regulatory options available
to -the Agency to reduce the risks from the registered uses of
dicofol. The legal basis for these options is also discussed
and each option will be evaluated for its impact on the risks
and benefits of the registered uses of dicofol; then the most
appropriate regulatory option is selected.
B. LEGAL BASIS FOR OPTIONS
FIFRA provides the Agency with three legal courses of
action concerning a registered pesticide. These are suspension/
cancellation, continued registration with no restrictions, or
amendment of the terms and conditions of registration.
To make a determination as to which course of action is
appropriate, the Agency weighs the risks and benefits of the
uses of a pesticide. If the risks of use outweigh the benefits,
and the risks cannot be lowered, registration may be cancelled.
In the case of cancellation, the Agency issues a notice of
intent to cancel the registrations of a pesticide [FIFRA, section
6(b)(1)]. Such a cancellation notice becomes effective auto-
matically 30 days after publication or receipt by the affected
registrants, unless a registrant or other adversely affected
party reguests a hearing regarding the cancellation.
If the benefits of continued use outweigh the risks and
any actions taken to reduce the risk result in a significant
reduction in benefits, the registration of that use may
continue with no restrictions. In the case of continued
registration without restrictions for a chemical which was
initially identified as a potential cause of unreasonable
adverse effects and subjected to Special Review, the Agency
IV-1
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may publish a final Special Review document (PD 4) stating a
rationale for choosing that course of action.
A wide range of possible regulatory actions exists for
cases when the risks exceed the benefits or when the benefits
are greater than the risks, and the reduction in risk would
not result in a significant reduction in benefits. FIFRA
requires the Agency to "consider restricting a pesticide's
use or uses as an alternative to cancellation..." [FIFRA
Secion 6(b)]. Although FIFRA does not specify what kinds of
restrictions are to be examined, the Agency interprets this
to mean amending the terms and conditions of registration in
any fashion necessary to lower risks without counterbalancing
reduction in benefits.
C. DATA GATHERING FOR IDENTIFICATION OF OPTIONS
In the process of varying the terms and conditions of
registration, the Agency can investigate many regulatory options.
In order to facilitate the development of viable regulatory
options, FIFRA provides the Agency with certain legal mechanisms
to be used in the process of gathering information on available
options. The legal mechanisms which FIFRA provides are:
1. Additional Data
Under FIFRA section 3(c)(2)(B), the Agency may require a
registrant to submit any additional data necessary to maintain
an existing registration. When conducting a special review of
a pesticide, the Agency may identify areas in its risk and benefit
analyses where data are inadequate or lacking. The Agency
may then require a registrant to provide specific data within
a certain time. If the registrant fails to comply, his regis-
trations may be suspended. If the newly submitted data
justify doing so, the appropriate regulatory course of action
can be reconsidered.
2. Information-Gathering Hearings
If the Agency is uncertain whether to cancel or restrict
a pesticide, he may publish a notice of intent to hold a
formal hearing to resolve the issue [FIFRA section 6(b)(2)].
At the end of the hearing, the Agency makes a decision based
on the hearing record. As an alternative to a formal hearing,
the Agency may conduct an informal hearing to gather information
[FIFRA section 21(b)] and then use that information to propose
a recommended decision.
D. LEGAL OPTIONS AVAILABLE UNDER FIFRA
The following regulatory options are available to the
Agency under FIFRA to reduce the risks from the registered
uses of a pesticide.
IV-2
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1. Classification for Restricted Use
FIFRA Section 3(d) enables the Agency to restrict a
pesticides use(s) if such use(s) cause unreasonable adverse
effects. This classification means that the pesticide may only
be applied by or under the supervision of a certified applicator,
one who is trained and approved by a state as competent to use
restricted pesticides.
2. Amend the Terms and Conditions of Registration
Including Changes in Labeling
One of the reguirements for registration as specified in
FIFRA section 3(c)(5) is that labeling of a pesticide product
comply with the reguirements of FIFRA. That is, the product
when used in accordance with directions for use will not
result in unreasonable adverse effects to man or his environment.
The Agency may require a registrant to amend the registration
by revising labeling or otherwise modifying the conditions of
use in order to keep the product in compliance with FIFRA.
Examples of labeling changes include removal of certain
uses from those registered, requiring protective clothing,
respirators, hazard warning to applicators, changes in application
rates or methods, and other use or handling directions which
are designed to reduce risks to man or his environment.
3. Summary
In summary, FIFRA and the FFDCA provides the Agency
with several legal authorities for a number of regulatory
options for special review pesticides. Given this legal
authority, the Agency next must explore possible use restrictions
(i.e., amendments to the terms and conditions of registration),
and evaluate the extent to which these restrictions would
reduce the risks of dicofol.
E. REGULATORY OPTIONS FOR DICOFOL
Three basic regulatory options have been developed:
Option 1 — Allow the registrants to continue to
manufacture and market their current dicofol products with no
further reduction in the amount of DDTr contamination levels.
This option would mean that the Agency has found that the
risks of the current levels of DDTr in dicofol would be
acceptable in light of the benefits.
Option 2 — Amending the terms and conditions of regis-
tration, to require registrants to reduce DDTr contamination
in the manufacturing-use products to a level below that of
the current products. Two registrants have proposed lowering
the DDTr levels in their manufacturing-use products. This
option would mean that the Agency would have to find the
IV-3
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risks from the lowered DDTr levels acceptable in light of the
benefits.
Option 3 -- Cancel registrations of dicofol. This option
would mean that the sale or distribution of the pesticide
would be prohibited. This option would be based on a determin-
ation that the risks from dicofol with either current levels
or reduced levels of DDTr would be unreasonable in light of
the benefits.
A fourth option, to place various restrictions on the use of
dicofol products, was examined but rejected. These various
restrictions and the reason why the Agency discounted them
are discussed below:
1. Reduce the application rate or freguency of application.
The Agency agrees that a sufficiently reduced application
rate or freguency could reduce the potential effects, but
they would have to be extremely low. One registrant noted
that a restriction such as this would leave the product ineffective.
2. Restrict application of dicofol products geographically,
either away from areas where DDT background .levels are
already high, or away from areas where sensitive birds
nest.
This alternative does not appear to be viable. Since
the adverse effects to wildlife can occur solely from a
single application of dicofol, use directions relating to the
background level cannot avoid the unreasonable adverse effects
on the environment. The Agency believes that there is no
agriculturally important area where the product could be
applied that would not result in exposure to sensitive birds.
3. Restrict application to a time of year when birds are
not reproducing.
This alternative would not be effective since the DDTr
ingested at any time of year is bioaccumulated in the fat of
the birds, and since DDTr persists in the environment long after
application.
The Agency also considered a fifth option -- a phase-out
for dicofol products, rather than an immediate cancellation.
This was also rejected because the adverse effects to wildlife
would still be occurring during that time period and the
continued addition of DDTr to the environment would continue
to slow the rate of decline. The benefits of dicofol remain
the same, i.e., alternatives are currently available for most
uses of dicofol, and the nationwide impact of cancellation is
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expected to be minimal. Thus, the Agency has concluded that
the use of dicofol during any phase-out period would result in
unreasonable adverse effects.
F. RISK/BENEFIT ANALYSIS OF REGULATORY OPTIONS, USE BY USE
1. Cotton
a. Option 1
If registrations of dicofol products for use on cotton
were continued without restriction, an estimated 72,000
pounds of DDTr would be released into the environment, mostly
concentrated in the San Joaquin Valley in California. As
detailed in Chapter II, this release of DDTr would likely
cause adverse effects on wildlife, both in California and
neighboring states.
Under Option 1 the economic benefits would continue un-
affected. These benefits are estimated to be between $10.2
and $30.1 mil]ion over the short term and between $11.9 and
$41.2 million over the long term to cotton producers in the
San Joaquin Valley. The nonmonetary benefits would also
continue, i.e., the usefulness of dicofol in integrated pest
management programs and having dicofol available to slow
development of pest resistence to alternatives. The minimal
benefits to the consumer would also continue.
The Agency has compared the risks to wildlife and the
benefits of dicofol use and has concluded that continuing the
registration of dicofol on cotton will present an unreasonable
adverse effect to the environment. Therefore, this option is
rejected.
b. Option 2
If the level of DDTr in dicofol products were lowered
below the current certified levels, there would still be
exposure and adverse effects to wildlife to DDTr. Even though
the registrants have proposed to lower DDTr to almost half of
the current levels, the Agency believes that this level would
still cause adverse effects. In addition, because the Agency
has no data showing a level of DDTr exposure below which
adverse effects on wildlife will not occur, it has no basis
for specifying a level of DDTr in dicofol that would result
in environmental residues that would be free of adverse
effects.
Under Option 2 the economic benefits would also continue
unaffected. These benefits are estimated to be between
$10.2 and $30.1 million over the short term and between $11.9
and $41.2 million over the long term to cotton producers in
the San Joaquin Valley. The nonmonetary benefits would also
continue, i.e., the usefulness of dicofol in integrated pest
IV-5
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management programs and having dicofol available to slow
development of pest resistence to alternatives. The minimal
benefits to the consumer would also continue.
Based on a weighing of the continued risks of a lowered
amount of DDTr to wildlife against the benefits of dicofol,
the Agency concludes that these risks outweigh the benefits
and that this option is unacceptable.
The Agency may give further consideration to this option
if the registrants were to substantially reduce the DDTr
levels further and provide new evidence demonstrating that
this reduced DDTr level would not pose an unreasonable adverse
effect to wildlife.
c. Option 3
If the registrations of dicofol products for use on
cotton were cancelled, all DDTr-related risks, from the use
of dicofol, to the environment would be eliminated.
Benefits from the use of dicofol for cotton production
would be lost. Current cotton producers in the Southeast
could switch to alternative miticides at no increased costs,
while those in Arizona and California (outside of the San
Joaguin Valley) may switch to alternatives, but would incur
an added insubstantial increase in treatment costs. The
cotton producers in the San Joaguin Valley would be most
affected by cancellation. In the short term, losses ranging
from $10.2 and $30.1 million, and in the long-term, losses to
these producers could range from $11.9 - $41.2 million,
depending upon the yield reduction experienced. It is possible
that some of the San Joaguin Valley producers might be forced
to switch to alternative crops. Even if a substantial shift
out of cotton occurred in the San Joaguin Valley, the current
national acreage would continue at a level which would permit
growers in other areas to fill the supply gap. In addition,
the prices faced by consumers of cotton products most likely
would rise only slightly, or not at all.
Significant nonmonetary benefits of dicofol could also
be lost. The most important ones are: 1) Dicofol is only
effective against mites, unlike many of the possible broad
spectrum insecticide/miticides, and this makes dicofol the
choice of many integrated pest management programs, 2) Tolerance
or resistance of mites to alternatives and dicofol is a
critical factor in selecting and alternating these pesticides,
and 3) Reduction in the number and type of miticides will
increase usage of the remaining miticides, increase selective
pressure, and accelerate development of resistance to the
remaining pesticides.
IV-6
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After weighing these benefits against the substantial risks
to the environment, the Agency has concluded that the continued
use of DDTr contaminated dicofol would cause unreasonable
adverse effects to the environment and that registrations of
dicofol products intended for use on cotton should be cancelled.
2. Citrus
a. Option 1
If registrations of dicofol products for use on citrus
were continued without restriction, an estimated 100,000 pounds
of DDTr would be released into the environment, principally in
the citrus growing regions of Florida, southern Texas, Arizona,
and California. This resulting exposure to the environment
would likely cause adverse effects to wildlife in these local
growing areas, as well as potential effects to wildlife
throughout the country due to the uncontrollable mobility of
DDTr.
Under Option 1 the economic benefits would continue
unaffected. These benefits are estimated to range from
between $3.5 and $4.0 million annually, which is less than
0.02 percent of the total U.S. production. The nonmonetary
benefits would be similar to that of cotton.
The Agency has compared the risks to wildlife and the
benefits of dicofol use and has concluded that continuing the
registration of dicofol on citrus will present an unreasonable
adverse effect to the environment. Therefore, this option is
rej ected.
b. Option 2
If the level of DDTr in dicofol products were lowered
below the current certified levels, there would still be
levels of exposure resulting in adverse effects to wildlife.
Even though the registrants have proposed to lower DDTr to
almost half of the current levels, the Agency believes that
this level would still cause adverse effects. In addition,
the Agency has no data showing a level of DDTr exposure below
which adverse effects on wildlife will occur. The Agency has
no basis for for specifying a level of DDTr in dicofol that
would result in environmental residues that would be free of
adverse effects.
The benefits consideration would be the same as described
under Option 1. Based on a weighing of the continued risks of
a lowered amount of DDTr to wildlife against the benefits of
dicofol, the Agency concludes that these risks outweigh the
benefits and that this option is unacceptable.
IV-7
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The Agency may give further consideration to this option
if the registrants were to substantially reduce the DDTr
levels further and provide new evidence demonstrating that
this reduced DDTr level would not pose an unreasonable adverse
effect to wildlife.
c. Option 3
If the registrations of dicofol products for use on
citrus were cancelled, all DDTr-related risks from further
use of dicofol to the environment would be eliminated.
The economic impact associated with the cancellation of
dicofol use on citrus crops is expected to range from $3.5 to
$4.0 million annually. These increased costs are due to the
higher cost of using alternatives. There is no anticipated
reduction in yields. The average value of U.S. citrus production
between 1977 and the present has been approximately $1.8
billion based on the equivalent packinghouse-door fresh
and processed sales. The aggregate dollar impact of dicofol
cancellation ($3.5 - $4.0 million) is expected to be less
than 0.02 percent of the value of total U.S. production.
The nonmonetary benefits would be similar as those for the
cotton use.
After evaluating the environmental risks and the economic
benefits associated with dicofol use in the citrus industry,
especially in the citrus growing areas of Florida, Texas,
Arizona, and California, the Agency has determined that the
continued use of DDTr contaminated dicofol on citrus would
cause unreasonable adverse effects to the environment and
concludes that registrations of dicofol products intended for
use on citrus should be cancelled.
3. Other Uses
Dicofol is used to control many species of mites on
other minor sites, i.e., seed crops, pome and stone fruits,
ornamental plants, turf grasses, vegetables, tree nuts, small
fruits, mint, and home and garden uses. About a third of
dicofol produced is applied to these sites.
a. Option 1
The Agency does not have specific risk data on these
sites. However, based on the known effects of and mobility
of DDTr in the environment, it is reasonable to assume that
the same adverse effects that could appear in the citrus and
cotton growing areas would likely occur in these use sites.
Under Option 1 the economic benefits would continue
unaffected. The benefits of dicofol use on all minor use
sites has not been guantified to date. However, for a few
sites, it is estimated that these benefits are between $1.1
and $1.4 million for producers of apples, nuts, and mint.
IV-8
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The nonmonetary benefits would also continue, as well as the
benefits to the consumer.
The Agency has compared the potential risks to wildlife
and benefits of dicofol use and concluded that continuing the
registration of dicofol for use on these minor sites will
present an adverse effect on the environment. Therefore,
this option is rejected.
b. Option 2
If the level of DDTr in dicofol products were lowered
below the current certified levels, there would still be an
exposure resulting in adverse effects to wildlife. Even
though the registrants have proposed to lower DDTr to almost
half of the current levels, the Agency believes that this
level would still cause adverse effects. In addition, because
the Agency has no data showing a level of DDTr exposure below
which adverse effects on wildlife will not occur, it has no
basis for specifying a level of DDTr in dicofol that would
result in environmental residues that would be free of adverse
effects.
The benefits consideration would be the same as described
under Option 1. Based on a weighing of the continued risks of
a lowered amount of DDTr to wildlife against the benefits of
dicofol, the Agency concludes that these risks outweigh the
benefits and that this option is unacceptable.
The Agency may give further consideration to this option
if the registrants were to substantially reduce the DDTr
levels further and provide new evidence demonstrating that
this reduced DDTr level would not pose an unreasonable adverse
effect to wildlife.
c. Option 3
If the registrations of dicofol products for use on
these other sites were cancelled, all DDTr-related risks
from further use of dicofol to the environment would be
eliminated.
The economic impacts relating to the cancellation of
dicofol use on all minor use sites has not been guantified to
date. However, it is estimated that production costs will
increase from $1.1 to $1.4 million for producers of apples,
nuts (principally pecans) and mint, solely as a result of
using costlier alternatives. The remaining minor use sites are
likely to realize some level of negative impacts, the magnitude
of which is unknown. The nonmonetary benefits to these other
uses that would be lost would be similar to that of cotton
and citrus.
After evaluating the environmental risks and the economic
benefits associated with dicofol use in these other sites,
IV-9
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the Agency has determined that the continued use of DDTr
contaminated dicofol on these other sites would cause unreason-
able adverse effects to the environment and concludes that
registrations of dicofol products intended for use on these
other sites should be cancelled.
The Agency will consider rebuttal comments on the benefits
of dicofol use on each individual site in its final decision
and will consider retaining uses for which benefits are high
and the risks are low.
G. SUMMARY OF PROPOSED REGULATORY DECISION
1. Cotton Use
Cancel all registrations for dicofol use on cotton.
2. Citrus Use
Cancel all registrations for dicofol use on citrus.
3. Minor Uses
Cancel registrations for all minor uses of dicofol.
IV-10
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