Sr^. UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
15 Q \ WASHINGTON D C. 20460
OFFICE OF CHEMICAL SAFETY AND
POLLUTION PREVENTION
MEMORANDUM
Date: June 26, 2019
SUBJECT: Paraquat Dichloride: Draft Human Health Risk Assessment in Support of
Registration Review
PC Code: 061601 DP Barcode: D430827
Decision No.: 512268 Regulatory Action: Registration Review
Risk Assessment Type: Single Reregistration Case No.: 0262
Chemi cal/Aggregate
TXRNo.: NA CAS No.: 1910-42-5
MRIDNo.: NA 40 CFR: §180 205
FROM: Wade Britton, MPH, Environmental Health Scientist
Thurston Morton, Chemist /A-
Austin Wray, Ph.D., Toxicologist ' "i I\jA^
Risk Assessment Branch 4 (RAB4)
Health Effects Division (HED; 7509P)
THROUGH: Kristin Rickard, Acting Branch Chief v
RAB4/HED (7509P)
And
Christine Olinger, RARC Management Lead
Michael Metzger, RARC Designated Reviewer ^
HED Risk Assessment Review Committee (RARC)
TO: Marianne Mannix, Chemical Review Manager
Risk Management and Implementation Branch III (RMIB III)
Pesticide Re-evaluation Division (PRD; 7508P)
Office of Pesticide Programs
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Table of Contents
1.0 Executive Summary 4
2.0 HED Conclusions 11
2.1 Data Deficiencies 11
2.2 Tolerance Considerations 12
2.2.1 Enforcement Analytical Method 12
2.2.2 Recommended Tolerances 12
2.2.3 International Harmonization 19
2.3 Label Recommendations 19
3.0 Introduction 19
3.1 Chemical Identity 20
3.2 Pesticide Use Pattern 20
3.3 Anticipated Exposure Pathways 21
3.4 Consideration of Environmental Justice 21
4.0 Hazard Characterization and Dose-Response Assessment 21
4.1 Toxicology Studies Available for Analysis 21
4.2 Absorption, Distribution, Metabolism, and Excretion (ADME) 23
4.3 Toxicological Effects 25
4.3.1 Epidemiology Review Summary 26
4.3.2 Parkinson's Disease Systematic Review 29
4.4 Safety Factor for Infants and Children (FQPA Safety Factor) 32
4.4.1 Completeness of the Toxicology Database 32
4.4.2 Evi dence of Neurotoxi city 33
4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal 33
4.4.4 Residual Uncertainty in the Exposure Database 34
4.5 Toxicology Endpoint and Point of Departure Selections 34
4.5.1 Dose-Response Assessment 34
4.5.2 Recommendations for Combining Routes of Exposure for Risk Assessment 37
4.5.3 Cancer Classification and Risk Assessment Recommendation 37
4.5.4 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk
Assessment 38
4.6 Endocrine Disruption 40
5.0 Dietary Exposure and Risk Assessment 40
5.1 Residues of Concern Summary and Rationale 40
5.2 Summary of Plant and Animal Metabolism Studies 41
5.3 Summary of Environmental Degradation 42
5.4 Comparison of Metabolic Pathways 42
5.5 Food Residue Profile 42
5.6 Water Residue Profile 43
5.7 Dietary Risk Assessment 43
5.7.1 Overview of Residue Data Used 43
5.7.2 Percent Crop Treated Used in Dietary Assessment 44
5.7.3 Acute Dietary Risk Assessment 44
5.7.4 Chronic Dietary Risk Assessment 44
5.7.5 Cancer Dietary Risk Assessment 45
6.0 Residential (Non-Occupational) Exposure/Risk Characterization 45
7.0 Aggregate Exposure/Risk Characterization 45
8.0 Non-Occupational Spray Drift Exposure and Risk Estimates 45
9.0 Non-Occupational Bystander Post-Application Inhalation Exposure and Risk Estimates 49
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10.0 Cumulative Exposure/Risk Characterization 49
11.0 Occupational Exposure/Risk Characterization 50
11.1 Occupational Handler Exposure/Risk Estimates 50
11.2 Occupational Handler Biomonitoring Data Evaluation 52
11.3 Occupational Post-Application Exposure/Risk Estimates 56
11.3.1 Occupational Post-Application Dermal Exposure/Risk Estimates 57
11.3.2 Occupational Post-Application Inhalation Exposure/Risk Estimates 64
12.0 Public Health Incident Data Review 65
Appendix A. Toxicology Profile and Executive Summaries 67
A. 1 Toxicology Data Requirements 67
A.2 Toxicity Profiles 68
A.3 Executive Summaries 80
A.3.1 Studies Used for Points of Departure (POD) 80
A.3.2 Other Studies Updated for Registration Review 85
A.4 Paraquat General Literature Review Results 86
Appendix B: Physicochemical Properties of Paraquat Dichloride 90
Appendix C: International Residue Limit Status Sheet 91
Appendix D. Summary of Paraquat Occupational Handler Exposure and Risk Estimates 94
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1.0 Executive Summary
This assessment has been conducted to support the Registration Review of the insecticide
paraquat dichloride, herein referred to as paraquat. As part of Registration Review, the PRD of
the Office of Pesticide Programs (OPP) has requested that HED evaluate the hazard and
exposure data and conduct dietary and occupational/residential exposure assessments, as needed,
to estimate the potential risk to human health that could result from the currently registered uses
of paraquat. This memorandum contains HED's human health exposure and risk estimates from
paraquat. The current paraquat human health risk assessment contains the following updates
from the most recent published risk assessment (D415809, T. Morton, 09/25/2014):
• New points of departure (POD) were selected for all exposure scenarios;
o The new acute dietary POD (5 mg paraquat ion/kg) is based on clinical signs and
mortality in the rat developmental study. The previous acute POD was 1.25 mg
paraquat ion/kg.
o The new chronic dietary POD (0.5 mg paraquat ion/kg/day) is based on
respiratory toxicity in two co-critical dog oral toxicity studies. The previous
chronic POD was 0.45 mg paraquat ion/kg/day.
o The new incidental oral POD (0.5 mg paraquat ion/kg/day) is based on the same
effects as the chronic dietary POD. An incidental oral POD was not selected in
previous risk assessments,
o The new dermal POD (6 mg paraquat ion/kg/day) is based on the systemic
NOAEL from a route specific dermal study. Previously, the dermal POD was
based on an oral endpoint and the extrapolated dermal dose would be
approximately 25 mg paraquat ion/kg/day.
o The inhalation POD (0.01 |ig paraquat ion/L/day) is based on portal of entry
effects in a route specific inhalation study. Previously, the paraquat human health
risk assessment selected a respirable (same as new POD) and non-respirable POD
(1.25 mg paraquat ion/kg/day) and inhalation risk was assessed using the non-
respirable POD based on the assumption that inhalation exposure would only be
to particulates in the non-respirable range. The current risk assessment does not
make this assumption.
• The conclusions from the epidemiology and Parkinson's disease systematic reviews were
incorporated into hazard characterization and accounted for in the POD selection;
• The occupational handler and occupational post-application assessments were updated to
incorporate recent updates to the dermal and inhalation PODs, and policy changes for
body weight, unit exposure, transfer coefficient, and area/amount treated assumptions;
• A non-occupational spray-drift exposure/risk assessment was completed; and
• The history of human incidents associated with paraquat di chloride use were reviewed in
a Tier II human incident report.
Use Pattern
Paraquat dichloride (l,r-dimethyl-4,4'-bipyridinium dichloride) is a non-selective herbicide
currently registered for the control of weeds and grasses in agricultural and non-agricultural
areas. It is a contact herbicide that desiccates and destroys plant cell membranes within hours of
application. Paraquat is only formulated as a soluble concentrate/liquid (SC/L) formulation. The
active ingredient, paraquat dichloride, exists as a mixture of paraquat cations (dications) and
chloride anions. Paraquat cation is the toxic moiety and, therefore, the form evaluated for
purpose of exposure and risk assessment. Paraquat can be used pre-plant or pre-emergence, at
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planting, post-emergence, as a desiccant or harvest aid, as well as a postharvest desiccant. It may
be applied to agricultural and non-agricultural areas (e.g., non-crop lands, and pasture lands)
with aerial, ground, and handheld spray equipment. Paraquat is a restricted use pesticide (RUP)
based on acute toxicity; therefore, there are no paraquat products registered for homeowner use
and no products registered for application to residential areas. Tolerances have been established
for paraquat under 40CFR§ 180.205(a) for multiple commodities, and range from 0.01 ppm for
egg and milk to 210 ppm for animal feed items. Tolerances with regional registration have been
established under 40CFR§ 180.205(c) at 0.05 ppm for pigeon pea seed and tyfon, and at 0.1 ppm
for taro corm.
Exposure Profile
Humans may be exposed to paraquat in food and drinking water since paraquat may be applied
directly to growing crops and application may result in it reaching surface and ground water
sources of drinking water. Non-occupational exposures may occur as a result of spray drift from
off-target applications of paraquat. Occupational handler and post-application exposures are
expected from paraquat usage. This risk assessment considers all the aforementioned exposure
pathways based on the existing paraquat uses.
All registered labels require occupational handlers (mixers and loaders) to wear "baseline"
clothing (i.e., a long-sleeved shirt, long pants, shoes and socks), chemical resistant gloves, a
National Institute of Occupational Safety and Health (NIOSH) approved half-mask [assigned
protection factor (APF) 10; 90% exposure reduction] respirator, as well as a chemical resistant
apron and face shield. Applicators and other handlers (other than mixers and loaders) must wear
baseline clothing, chemical resistant gloves, a NIOSH approved half-mask respirator, as well as
protective eyewear. Occupational handler exposures are expected to be both short- (1 to 30
days) and intermediate-term (1 to 6 months).
Based on the high number and severity of human health incidents associated with paraquat
involving the ingestion of paraquat, both accidental and intentional, the EPA determined that risk
mitigation measures were necessary for paraquat pesticide products to meet the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA) standard for registration. This mitigation
decision[1] was published in January 2017. The following mitigation measures were implemented
in three phases. Submission deadlines and implementation timeframes for these measures are
discussed below.
1. Label amendments to emphasize paraquat toxicity and restrict use of all paraquat
products to certified applicators only (i.e., prohibiting use by uncertified persons
working under the supervision of a certified applicator), and supplemental warning
materials
a. Implementation timing:
i. Revised labels and supplemental materials were submitted to EPA in
March 2017
ii. Revised labels and supplemental materials were stamped approved by
EPA in late Summer/Fall 2018
iii. New products released into commerce must bear this new labeling by
late Summer/Fall 2019
M. Mannix. Amended: Paraquat Dichloride Human Health Mitigation Decision. January 12, 2017. This document supersedes
the December 14, 2016 Paraquat Dichloride Human Health Mitigation Decision.
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2. Targeted training materials for paraquat users
a. Implementation timing:
i. Released online in March 8, 2019
ii. New products released into commerce must bear new labeling
specifying the requirement to take the targeted paraquat training by
late Summer/Fall 2019
3. Closed-system packaging for all non-bulk (less than 120 gallon) end use product
containers of paraquat
a. Implementation timing:
i. Revised labels specifying the closed system requirement were due to
EPA on March 29, 2019
ii. The revised labels are currently under review in EPA and should be
stamped in Summer/Fall 2019
iii. All non-bulk products must be in closed systems one year from the
date that the labels are stamped by EPA
iv. EPA's existing stock provision applies
Due to the additional requirement for closed-system packaging for all non-bulk (less than 120
gallons) end use product containers, this occupational handler exposure and risk assessment
considers the currently required levels of PPE described above, as well as the closed-system
packaging for mixers and loaders.
The likelihood of occupational post-application exposures is dependent on whether paraquat
applications are "directed" or "broadcasted." Directed spray applications of paraquat are
targeted for control of individual weeds and grasses. Such applications are made with the intent
of minimizing the risk of injuring the crop and/or non-target vegetation which are not tolerant of
directed paraquat applications. Since applications to the foliage of the crop are not expected to
occur, occupational post-application exposures are not likely for directed applications and have
not been assessed. Broadcast applications of paraquat are applied directly to the crop for foliage
desiccation (to the crop and any weeds in the field) to expedite harvest and reduce seed loss upon
harvest. Therefore, occupational post-application exposures are expected for broadcast
applications and have been assessed herein. Occupational post-application exposures are
expected to be both short- and intermediate-term in duration. Labeled restricted entry intervals
(REIs) range from 12 to 24 hours.
Spray drift exposures may also occur following applications of paraquat to agricultural and non-
agricultural areas and are expected to be short-term in duration.
Hazard Characterization
Paraquat is poorly absorbed and efficiently eliminated following oral administration. The
fraction that is absorbed is excreted primarily as unchanged parent in the urine. The primary
target organ of paraquat is the lungs with evidence of lung inflammation, scarring, and
compromised lung function observed throughout the toxicity database in different species and
across routes of exposure (oral and inhalation). Other target organs identified in the toxicity
database include the kidneys (mice and rabbits), and eyes (rats). Paraquat caused minimal to
moderate skin irritation in rabbits and rats following acute dermal exposure and was not acutely
lethal in rats up to 2000 mg technical concentrate/kg (paraquat ion not calculated). Prolonged
dermal exposure, however, is more corrosive to the skin. Repeat dermal exposure in rabbits at
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doses >2.6 mg paraquat ion/kg/day elicited a varied dermal response (scabbing, epidermal
erosion/ulceration, surface exudation, acanthosis, and inflammation) that increased in frequency
and severity with duration and dose. These effects are consistent with dermal toxicity described
in the human incident report. Skin damage was the most commonly reported symptom for
incidents resulting from occupational use and ranged from blisters and dry skin to chemical
burns and lesions. Despite evidence of dermal toxicity, no systemic toxicity was observed in
rabbits following 21 days of exposure up to 6 mg paraquat ion/kg/day (the highest dermal dose
evaluated). Although the skin was an effective barrier within the dose range characterized in the
toxicity database, systemic toxicity is anticipated at higher dermal doses that further erode the
integrity of the skin and allow unimpeded access to the bloodstream. No evidence of pre- or
post-natal sensitivity was observed across the toxicity database. Developmental (reduced body
weight/gain and delayed skeletal ossification) and offspring effects (sporadic histopathology
lesions) were observed only at parentally toxic doses that were above the selected points of
departure (PODs). Limited evidence of age-related sensitivity was observed in the open
literature, but only from exposure to a high purity paraquat product (purity >98%), which is not
representative of the paraquat products (purity <48%) undergoing Registration Review. The
PODs selected for risk assessment account for toxicity from exposure to paraquat sources that
are analogous to the technical product (the highest purity products registered) and are thus
protective of the developmental and offspring effects resulting from exposure to the registered
technical products and lower purity formulations. There was also no evidence of
immunotoxicity in response to paraquat.
The relationship between paraquat exposure and Parkinson's disease was assessed based on
results reported in guideline and non-guideline studies in the toxicity database and relevant
human, animal, and in vitro studies identified in two systematic reviews (a focused Parkinson's
disease review and a general epidemiology review) of the open literature. The focused
Parkinson's disease (PD) systematic review was conducted with support from the National
Toxicology Program (NTP). As part of the PD systematic review, NTP and the agency
collaborated on a scoping review of the open literature to identify and summarize studies that
were relevant to the Agency's evaluation of the paraquat-PD association. In addition to the
collaboration, experts from NTP provided technical support on the systematic review process
and addressed questions pertaining to neuropathology and PD that aided interpretation of study
results. After comprehensive review of the relevant studies, the Agency concluded that the
weight of evidence was insufficient to link paraquat exposure from pesticidal use of US
registered products to PD in humans. Moreover, the few studies from the open literature that
report PD-like effects in animal models from exposure routes anticipated for pesticidal uses (e.g.
oral, dermal, inhalation) observed them following subchronic exposure to dose levels at least 14
times above the current subchronic and chronic PODs. Thus, the risk assessment accounts for
and is protective of the limited evidence of neurotoxic effects reported in the open literature for
routes of exposure relevant to the paraquat human health risk assessment.
PODs were selected for dietary (acute and chronic), incidental oral (short-term), dermal (short-
and intermediate-term) and inhalation (short- and intermediate-term) exposure scenarios.
Uncertainty factors for interspecies extrapolation (UFa = lOx) and intraspecies variation (UFh =
lOx) were applied to each exposure scenario. The Food Quality Protection Act (FQPA) Safety
Factor (SF) was reduced to lx for all relevant scenarios based on the following: 1) the toxicity
database, with contributions from the open literature, is adequate to evaluate the potential for
susceptibility in infants and young children resulting from exposure to paraquat, 2) the dietary
assessments are based on reliable data and will not underestimate exposure, and 3) the PODs are
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protective of all known health effects resulting from paraquat exposure including evidence of
susceptibility and neurotoxicity in the open literature.
The acute and chronic dietary, incidental oral, dermal, and inhalation PODs were updated during
Registration Review. The acute dietary POD (5 mg paraquat ion/kg) for all populations was
based on clinical signs of agonal toxicity and mortality during the first week of exposure in the
developmental rat study. Although these effects occurred several days after the initial exposure,
they were consistent with a pattern of delayed mortality described in other acute studies in the
paraquat toxicity database and human incidents that were attributed to a single dose. The acute
reference dose (aRfD) and acute population-adjusted (aPAD) dose are both 0.05 mg paraquat
ion/kg. The chronic dietary POD (0.5 mg paraquat ion/kg/day) was based on increased lung
weight, incidence of gross lung lesions, and severity of chronic pneumonitis in two co-critical
subchronic and chronic dog oral toxicity studies. The chronic reference dose (cRfD) and chronic
population-adjusted dose (cPAD) are both 0.005 mg paraquat ion/kg/day. The incidental/adult
oral POD (0.5 mg paraquat ion/kg/day) is based on the same endpoints used for the chronic
dietary POD.
The dermal POD (6 mg paraquat ion/kg/day) is based on the systemic No Observed Adverse
Effect Level (NOAEL) from the route specific 21-day dermal toxicity study in rabbits. Six mg
paraquat ion/kg/day was the highest dermal dose tested (HDT) in the subchronic dermal study
and there are no additional studies in the toxicity database that investigate systemic or dermal
toxicity from repeat exposure at higher dermal doses. Although the toxicity database indicates
paraquat is not well absorbed across intact human skin, the corrosive properties of the chemical,
detailed in the dermal study and human incident reports, affect the integrity of the skin,
particularly after repeat exposure. Further corrosion of the dermal layer is anticipated at doses
above the HDT in the subchronic dermal study, which increases the likelihood of systemic
toxicity from dermal exposure. Consequently, the HDT from the route specific dermal study was
selected to be protective of the potential for systemic toxicity at higher dermal doses.
The inhalation POD (0.01 |ig paraquat ion/L/day) is based on evidence of increased incidence of
squamous keratinizing metaplasia and hyperplasia of the epithelium of the larynx observed when
exposed to respirable particles in the route specific subchronic inhalation study in rats. This
respirable particle POD was used to assess risk for all inhalation scenarios for Registration
Review. Previously, inhalation PODs were selected for both respirable and non-respirable
particles and the non-respirable particle POD, based on effects observed in an oral study, was
used for purpose of quantifying inhalation exposures and risks. A non-respirable particle POD
was not selected for Registration Review because there are no data to confirm that particulates
are non-respirable/greater than the respirable particle size range when paraquat is applied in an
occupational setting. The level of concern (LOC) for all non-dietary scenarios is 100.
Paraquat is classified Category E - evidence of non-carcinogenicity for humans - and does not
require a separate cancer assessment.
Dietary (Food and Water) Exposure and Risk
Acute and chronic dietary exposure assessments were performed for paraquat. The acute
assessment is based on tolerance-level residues, 100% crop treated (CT) and uses Dietary
Exposure Evaluation Model default processing factors for some commodities. The chronic
dietary exposure assessment is a partially refined assessment based on tolerance-level residues
and average estimates of percent crop treated. An Estimated Drinking Water Concentration
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(EDWC) of 0.15 ppb, as recommended by the Environmental Fate and Effects Division (EFED),
was used for both analyses. For the acute assessment, the general U.S. population and all
population subgroups have risk estimates that are below HED's level of concern (i.e., 100% of
the aPAD). The most highly exposed population subgroup is Children 1-2 years old which
utilizes 38% of the aPAD. The general U.S. population utilizes 20% of the aPAD. For the
chronic assessment, the general U.S. population and all population subgroups have risk estimates
that are below HED's level of concern (i.e., 100% of the cPAD). The most highly exposed
population subgroup is Children 1-2 years old which utilizes 25% of the cPAD. The general
U.S. population utilizes 6.6% of the cPAD.
Residential Exposures and Risks
Paraquat is a RUP; therefore, there are no paraquat products registered for homeowner use and
no products registered for application to residential areas. No residential handler or post-
application exposures are expected.
Non-Occupational Spray Drift
A quantitative non-occupational spray drift assessment was conducted for paraquat to assess the
potential for exposures from spray drift following agricultural applications. Adult dermal and
children 1 to < 2 years old dermal and incidental oral risk estimates from indirect exposure to
paraquat result in estimated distances from the field edge to reach the LOC ranging from 0 feet
to 150 feet depending on the application rate and equipment type combination assessed and
assuming screening level droplet sizes and boom heights. Results indicate that the major spray
drift risk concern is from aerial applications.
Aggregate Exposure and Risk
There are no residential uses of paraquat; therefore, the only relevant aggregate risk assessment
includes acute and chronic exposures to residues in food and drinking water. Both the acute and
chronic food and drinking water analyses are below HED's level of concern. The most highly
exposed population subgroup is Children 1-2 yrs old which utilizes 38% of the aPAD, and 25%
of the cPAD.
Occupational Handler Exposures and Risks
Occupational handler dermal and inhalation exposure and risk estimates were calculated for the
registered uses of paraquat. Dermal and inhalation risks were not combined since the PODs
selected are not based on the same toxicological effects. Inhalation exposures are the risk driver
for all paraquat occupational handler exposure scenarios assessed except for the
mixer/loader/applicator exposure scenarios for which dermal exposures are the highest
contributor. Estimated occupational handler risks for paraquat are as follows:
• Mixer/loaders: assuming the currently registered level of respiratory personal protection,
(a NIOSH approved half-mask, APF 10 respirator), inhalation risks are of concern [i.e.,
the margins of exposure (MOEs) are < the LOC of 100] for 13 of 26 exposure scenarios.
When considering the risk mitigation decision for these mixer/loader scenarios that
require enclosed systems, 21 of 26 remain of concern.
• Loader/applicators: assuming the currently registered level of respiratory personal
protection (a NIOSH approved half-mask, APF 10 respirator), the one exposure scenario
assessed results in an inhalation risk estimate of concern.
• Applicators and flaggers: assuming the currently registered level of respiratory personal
protection (a NIOSH approved half-mask, APF 10 respirator for flaggers, and a closed
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system for applicators), inhalation risks are of concern for 19 of 26 exposure scenarios
assessed.
• Mixer/loader/applicators: dermal risks are of concern for 6 of the 8 exposure scenarios
assessed at the currently required level of personal protection (baseline clothing and
chemical resistant gloves). Dermal risks of concern remain for all (6 of the 8) exposure
scenarios assessed despite the addition of double layer clothing.
Occupational Post-Application Exposure and Risks
Directed applications of paraquat are made with the intent of minimizing the risk of injuring the
crop and/or non-target vegetation which are not tolerant of directed applications. Since
applications to the foliage of the crop are not expected to occur, occupational post-application
exposures are not likely for directed applications and have not been assessed. Broadcast
applications of paraquat are applied directly to the crop for foliage desiccation to expedite
harvest and reduce seed loss upon harvest and, therefore, have been assessed. Due to the lack of
available dislodgeable foliar residue (DFR) data for paraquat, this assessment uses HED's
default assumption that 25% of the application is available for transfer on day 0 following the
application and the residues dissipate at a rate of 10% each following day.
Occupational post-application exposure and risks estimated for scouting activities are not of
concern (i.e., an MOE > 100) on the day of product application for all crops assessed except for
alfalfa. For alfalfa, reentry risks are not of concern 4 days following product application.
Occupational post-application exposure and risk estimated for cotton mechanical harvesting
activities (module builder operator, picker operator, raker, and tramper) range from 11 to 27 days
following product application.
Paraquat acute toxicity is low via the dermal route (Category III) and not irritating to the skin
(Category III); however, it is severely irritating to mucous membranes (Category I for eye
irritation). It is not a skin sensitizer. Under 40 CFR 156.208 (c) (2), active ingredients classified
as Acute I for acute dermal, eye irritation and primary skin irritation are assigned a 48-hour REI.
Therefore, the currently labeled REIs which range from 12 to 24 hours do not conform with 40
CFR 156.208 (c) (2) requirements. Further, the number of days required for estimated post-
application risks associated with paraquat usage estimated for reentry range from 0 to 27 days
and may require revision of the labeled REIs to address these concerns.
Occupational Handler Exposure and Risks Using Biomonitoring Data
Occupational handler and post-application biomonitoring studies are available for paraquat. To
characterize the occupational handler risk estimates calculated using surrogate, passive
dosimetry exposure data, HED has also estimated risks using an available paraquat occupational
handler biomonitoring study. The occupational handler biomonitoring study was reviewed, and
no human ethics concern was identified. Occupational handler risk estimates were quantified
using the absorbed doses measured from the biomonitoring study. The resulting MOEs for
mixing/loading and applying paraquat via groundboom range from 13 to 97 (LOC = 100)
depending on the combination of application rate and area treated daily.
A paraquat occupational post-application biomonitoring study was also available; however, this
study was reviewed and determined to have human ethics concerns, thus no post-application risk
estimates were quantified with use of these data.
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Environmental Justice
Potential areas of environmental justice concerns, to the extent possible, were considered in this
human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions
to Address Environmental Justice in Minority Populations and Low-Income Populations1."
Human Studies Review
This risk assessment relies in part on data from studies in which adult human subjects were
intentionally exposed to a pesticide or other chemical. These data, which include Pesticide
Handlers Exposure Database Version 1.1 (PHED 1.1); the Agricultural Handler Exposure Task
Force (AHETF) database; the Outdoor Residential Exposure Task Force (ORETF) database; the
Agricultural Reentry Task Force (ARTF) database; and a chemical-specific biomonitoring study
(MRID 43644202) are (1) subject to ethics review pursuant to 40 CFR 26, (2) have received
that review, and (3) are compliant with applicable ethics requirements. For certain studies, the
ethics review may have included review by the Human Studies Review Board (HSRB).
Descriptions of data sources, as well as guidance on their use, can be found at the Agency
website2.
2.0 HED Conclusions
There are no aggregate risks of concern identified for paraquat. However, risks of concern are
identified for occupational handlers and workers engaged in post-application activities. Further,
there are risks of concern identified from non-occupational spray drift at the field edge.
Please refer to Table 2.2.2 for tolerance recommendations.
2.1 Data Deficiencies
Enforcement Analytical Method: Analytical standards for paraquat di chloride need to be
submitted.
In vitro Skin Corrosion: Although not a requirement of registration, in vitro data on skin
corrosion, such as those reported for Organisation for Economic Co-operation and Development
(OECD) Guideline 431, would provide useful information on the interaction between paraquat
and skin cells that could be used to refine the assumptions in the dermal toxicity characterization
and dermal assessment.
Dislodgeable Foliar Residue (DFR): In accordance with 40CFR158, DFR data are required for
all occupational (e.g., crop, nursery, greenhouse use sites) or residential (e.g., ornamental and
vegetable gardens, pick your own farms, retail tree farms) uses that could result in post-
application exposure to foliage. Chemical-specific DFR data have not been submitted for
paraquat. The highest estimated occupational post-application exposure using default DFR
values is not minimal in comparison to the level of concern (i.e., the calculated MOE is not
greater than 2 times higher than the level of concern, MOE = 68 compared to the LOC of 100);
therefore, HED is recommending that DFR data (Guideline # 875.2100) be required to facilitate
1 http://www.archives.gov/federal-register/executive-orders/pdf/12898.pdf
2 https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handler-exposure-data
and https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-post-application-
exposure
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any necessary exposure assessment refinements and to further EPA's general understanding of
the availability of dislodgeable foliar pesticide residues.
Further, during cotton harvesting workers are expected to contact residues on cotton bolls
directly for which a "dislodgeable boll residue (DBR)" study would be required to refine
occupational post-application risks estimated for the crop. These chemical- and crop-specific
data are unique; DFR data for other crops cannot be used as a surrogate in the absence of a DBR
study. HED is recommending a DBR study be required to further EPA's general understanding
of the availability of cotton dislodgeable boll residues. These data should be conducted in
accordance with Guideline # 875.2100.
2.2 Tolerance Considerations
2.2.1 Enforcement Analytical Method
An adequate spectrophotometric method, Method I of the Pesticide Analytical Manual (PAM)
Vol. II, is available for enforcing tolerances for residues of paraquat in/on plant commodities.
For the method, samples are heated at reflux with 0.5 M sulfuric acid and then applied to a cation
exchange column. Paraquat residues are eluted with saturated ammonium chloride solution.
Samples are first subjected to Soxhlet extraction in hexane, and the hexane extract is refluxed
with sulfuric acid and then applied to the cation exchange column. An aliquot of the column
eluate is mixed with 0.2% (w/v) sodium hydrosulfite in 0.3 M sodium hydroxide, which reduces
paraquat to a free radical. Residues are determined using a variable wavelength
spectrophotometer, measuring the light absorption of the paraquat free radical. The validated
limits of quantitation (LOQ) vary from 0.01 ppm up to 0.5 ppm. PAM Vol. II lists a
spectrophotometric method, designated as Method la (LOD = 0.005 ppm), as available for the
enforcement of tolerances for paraquat residues in animal commodities. In addition, an adequate
HPLC/UV method is available for the enforcement of tolerances for paraquat residues in
livestock tissues and eggs (RAM 004/04, MRID 43226902; this method has not yet been
published in PAM Vol. II); the reported LOQ is 0.005 ppm for livestock tissues and eggs.
2.2.2 Recommended Tolerances
In 2009, HED issued guidance on tolerance expressions (S. Knizner, 05/27/2009). HED
concludes the tolerance expression for paraquat should be as follows:
Tolerances are establishedfor the residues of paraquat, including its metabolites and
degradates, in or on the commodities specified in the following table resulting from the
application of the dichloride salt ofparaquat. Compliance with the following tolerance
levels is to be determined by measuring only paraquat (1,1 '-dimethyl-4,4'-bipyridinium):
In addition, there are several tolerance level changes.
Page 12 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances for Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Commodity/Correct Commodity Definition
Established
Tolerance
Revised
Tolerance
Comments
Acerola
0.05
0.05
Almond, hulls
0.5
0.5
Animal feed, nongrass, group 18, forage
75.0
75
Corrected value to be
consistent with OECD
Rounding Class Practice.
Animal feed, nongrass, group 18, hay
210.0
200
Corrected value to be
consistent with OECD
Rounding Class Practice.
Artichoke, globe
0.05
0.05
Asparagus
0.5
Remove
Remove; covered by 22A
Atemoya
0.05
0.05
Avocado
0.05
0.05
Banana
0.05
0.05
Barley, grain
0.05
0.05
Barley, hay
3.5
3.5
Barley, straw
1.0
1.0
Beet, sugar, roots
0.5
0.5
Beet, sugar, tops
0.05
0.05
Berry and small fruit, group 13-07
0.05
Commodity definition
revision
Berry group 13
0.05
remove
Biriba
0.05
0.05
Cacao, dried bean
Commodity definition
correction
Cacao bean, bean
0.05
0.05
Canistel
0.05
0.05
Carrot, roots
0.05
0.05
Cattle, fat
0.05
0.05
Cattle, kidney
0.5
0.5
Cattle, meat
0.05
0.05
Cattle, meat byproducts, except kidney
0.05
0.05
Cherimoya
0.05
0.05
Coffee, green bean
Commodity definition
correction
Coffee, bean, green
0.05
0.05
Page 13 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances for Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Corn, field, forage
3.0
3
Corn, field, grain
0.1
0.1
Corn, field, stover
10.0
10
Corrected value to be
consistent with OECD
Rounding Class
Corn, pop, grain
0.1
0.1
Corn, pop, stover
10.0
10
Corrected value to be
consistent with OECD
Rounding Class
Corn, sweet, kernel plus cob with husks
0.05
0.05
Cotton, gin byproducts
110.0
100
Corrected value to be
consistent with OECD
Rounding Class
Cotton, undelinted seed
3.5
3.5
Cowpea, forage
0.1
0.1
Cowpea, hay
0.4
0.4
Cranberry
0.05
0.05
Custard apple
0.05
0.05
Egg
0.01
0.01
Endive
0.05
0.07
Feijoa
0.05
0.05
Fig
0.05
0.05
Fruit, citrus, group 10-10
0.05
Commodity definition
revision
Fruit, citrus, group 10
0.05
Remove
Fruit, pome, group 11-10
0.05
Commodity definition
revision
Fruit, pome, group 11
0.05
Remove
Fruit, stone, group 12-12
0.05
Commodity definition
revision
Fruit, stone, group 12
0.05
Remove
Goat, fat
0.05
0.05
Goat, kidney
0.5
0.5
Goat, meat
0.05
0.05
Goat, meat byproducts, except kidney
0.05
0.05
Page 14 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances for Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Grain, aspirated fractions
65.0
65
Corrected value to be
consistent with OECD
Rounding Class
Grape
0.05
0.05
Grass, forage
90.0
90
Corrected value to be
consistent with OECD
Rounding Class
Grass, hay
40.0
40
Corrected value to be
consistent with OECD
Rounding Class
Guar, seed
0.5
0.5
Guava
0.05
0.05
Hog, fat
0.05
0.05
Hog, kidney
0.5
0.5
Hog, meat
0.05
0.05
Hog, meat byproducts, except kidney
0.05
0.05
Hop, dried cones
0.5
0.5
Horse, fat
0.05
0.05
Horse, kidney
0.5
0.5
Horse, meat
0.05
0.05
Horse, meat byproducts, except kidney
0.05
0.05
llama
0.05
0.05
Jaboticaba
0.05
0.05
Kiwifruit
0.05
0.05
Lentil, seed
0.3
0.5
Harmonization with
Codex
Lettuce
0.05
0.05
Longan
0.05
0.05
Lychee
0.05
0.05
Mango
0.05
0.05
Milk
0.01
0.01
Nut, tree, group 14-12
0.05
Commodity definition
revision
Nut, tree, group 14
0.05
Remove
Okra
0.05
0.05
Page 15 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances for Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Olive
0.05
0.1
Harmonization with
Codex
Onion, bulb, subgroup 3-07A
0.1
Commodity definition
revision
Onion, bulb
0.1
Remove
Onion, green, subgroup 3-07B
0.05
Commodity definition
revision
Onion, green
0.05
Remove
Papaya
0.05
0.05
Passionfruit
0.2
0.2
Pawpaw
0.05
0.05
Pea and bean, dried shelled, except soybean,
subgroup 6C, except guar bean
0.3
0.5
Harmonization with
Codex
Pea and bean, succulent shelled, subgroup 6B
0.05
0.05
Pea, field, hay
0.8
0.8
Pea, field, vines
0.2
0.2
Peanut
0.05
0.05
Peanut, hay
0.5
0.5
Peppermint, fresh leaves
Commodity definition
correction
Peppermint, tops
0.5
0.5
Persimmon
0.05
0.05
Pineapple
0.05
0.05
Pineapple, process residue
0.25
0.3
OECD Rounding Class
(0.25 to 0.3 ppm)
Pistachio
0.05
Remove
Covered by Nut, tree,
group 14-12
Pomegranate
0.05
0.05
Pulasan
0.05
0.05
Rambutan
0.05
0.05
Rhubarb
0.05
0.05
Page 16 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances for Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Rice, grain
0.05
0.05
Safflower, seed
0.05
0.05
Sapodilla
0.05
0.05
Sapote, black
0.05
0.05
Sapote, mamey
0.05
0.05
Sapote, white
0.05
0.05
Sheep, fat
0.05
0.05
Sheep, kidney
0.5
0.5
Sheep, meat
0.05
0.05
Sheep, meat byproducts, except kidney
0.05
0.05
Sorghum, forage, forage
0.1
0.1
Sorghum, grain, forage
0.1
0.1
Sorghum, grain, grain
0.05
0.05
Soursop
0.05
0.05
Soybean, forage
0.4
0.4
Soybean, hay
10.0
10
Corrected value to be
consistent with OECD
Rounding Class
Soybean, hulls
4.5
4.5
Soybean, seed
0.7
0.7
Spanish lime
0.05
Spearmint, fresh leaves
Commodity definition
correction.
Spearmint, tops
0.5
0.5
Star apple
0.05
0.05
Starfruit
0.05
0.05
Strawberry
0.25
0.3
Corrected values to be
consistent with OECD
Rounding Class Practice.
Sugar apple
0.05
Sugarcane, cane
0.5
0.5
Sugarcane, molasses
3.0
3
Corrected values to be
consistent with OECD
Rounding Class Practice.
Page 17 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances for Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Sunflower, seed
2.0
2
Corrected values to be
consistent with OECD
Rounding Class Practice.
Turnip, greens
0.05
Remove
Remove; covered by 4-
16B
Turnip, roots
0.05
0.05
Vegetable, Head and Stem Brassica, Group 5-
16
0.07
Crop group
conversion/revision*
Vegetable, brassica, leafy, group 5
0.05
Remove
Brassica leafy greens subgroup 4-16B
-
0.07
Change in crop group 5.
Brassica leafy greens
subgroup 4-16B*
Stalk and Stem Vegetable Subgroup 22A
-
0.05
Change in crop group 5.
Stalk and Stem Vegetable
Subgroup 22A *
Vegetable, cucurbit, group 9
0.05
0.05
Vegetable, fruiting, group 8-10
Crop group
conversion/revision.
Vegetable, fruiting, group 8
0.05
0.05
Vegetable, legume, edible podded, subgroup 6A
0.05
0.05
Vegetable, tuberous and corm, subgroup 1C
0.50
0.5
Corrected values to be
consistent with OECD
Rounding Class Practice.
Wax jambu
0.05
0.05
Wheat, forage
0.5
0.5
Corrected value to be
consistent with OECD
Rounding Class
Wheat, grain
1.1
1.1
Wheat, hay
3.5
3.5
Wheat, straw
50.0
50
Corrected value to be
consistent with OECD
Rounding Class
c) Tolerances with regional registrations. Tolerances with regional registration as defined in §180.1(1). arc
established for residues of Daraaual. including its metabolites and dcaradatcs. in or on the commodities in the
table below. Compliance with the tolerance levels specified below is to be determined by measuring only
paraquat dichloridc and calculated as the paraquat cation in or on the following food commodities:
Page 18 of 103
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Tabic 2.2.2. Summary of Paraquat Established and Recommended Tolerances f<
r Registration Review.
(a) (ieneral. (I) Tolerances arc established for residues of Daraaual. including its metabolites and
dcgradatcs. in or on the commodities in the table below. Compliance with the tolerance levels specified
below is to be determined by measuring only paraquat dichloridc and calculated as the paraquat cation in
or on the following food commodities:
Pea, pigeon, seed
0.05
0.05
Taro, corm
0.1
0.1
Tyfon
0.05
0.05
* These recommended conversions of existing tolerances in/on crop subgroup 5A to crop group 5-16 (Brassica, head and stem
vegetable) and subgroup 5B to subgroup 4-16B (,Brassica leafy greens) are consistent with the document entitled "Attachment -
Crop Group Conversion Plan for Existing Tolerances as a Result of Creation of New Crop Groups under Phase IV (4-16, 5-16,
and 22)," dated 11/3/2015.
2.2.3 International Harmonization
The Codex Alimentarius Commission and Canada have established maximum residue limits
(MRLs) of paraquat for many commodities. The International Residue Limit (IRL) status sheet
is included as Appendix C. The Agency is currently harmonized with respect to the residue level
with Canada where both have established tolerances. The Agency is currently harmonized with
respect to the residue level and residue definition with Codex with many commodities. The US
tolerance of 0.05 ppm for endive, Vegetable, Head and Stem Brassica, Group 5-16, and Brassica
leafy greens subgroup 4-16B is recommended to be increased to 0.07 ppm to harmonize with
Codex. The US tolerance of 0.3 ppm for Lentil, seed, and Pea and bean, dried shelled, except
soybean, subgroup 6C, except guar bean is recommended to be increased to 0.5 ppm to
harmonize with Codex. The US tolerance of 0.05 ppm for olive is recommended to be increased
to 0.1 ppm to harmonize with Codex. Numerous U.S. tolerances are based on field trials where
detectable residues have been found so harmonization with Codex LOQ MRLs is not possible.
2.3 Label Recommendations
No specific label recommendations are being made; however, there are several risk estimates of
concern for occupational handlers. Some of these risk estimates are not of concern with the
addition of PPE beyond what is currently on labels. Product label changes regarding PPE and
engineering controls for paraquat may be required based on the occupational handler risks of
concern identified in this memorandum.
The registered paraquat labels currently specify REIs ranging from 12 to 24 hours which do not
conform with 40 CFR 156.208 (c) (2) requirements. Further, the number of days required for
estimated post-application risks associated with paraquat usage estimated for reentry range from
0 to 27 days and may require revision of the current REIs to address these concerns.
3.0 Introduction
Page 19 of 103
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3.1 Chemical Identity
Table 3.1. Nomenclature of Paraquat Dichloride
Compound
_ r„ CI
L Jz
h3c
Common name
Paraquat dichloride
IUPAC name
1,1' -dimethyl-4,4' -bypyridinium dichloride
CAS name
1,1' -dimethyl-4,4' -bypyridinium dichloride
CAS registry number
1910-42-5
(4685-14-7 for the cation)
End-use product (EP)
2.0 lb paraquat cation/gal SC
3.2 Physical/Chemical Characteristics
Physiochemical properties for paraquat are shown in Appendix B.
Paraquat dichloride is freely soluble in water. It has a very low vapor pressure (<10"8 kPa) and
has a low octanol water partition coefficient of log Kow = -4.5 at 20 °C. Paraquat was shown to
be very immobile in soil. It does not hydrolyze, does not photodegrade in aqueous solutions, and
is resistant to microbial degradation under aerobic and anaerobic conditions. The primary route
of environmental dissipation of paraquat is adsorption to biological materials and soil clay
particles. Due to the apparent adsorption strength of paraquat for soil clays, these bound residues
do not appear to be environmentally available.
3.2 Pesticide Use Pattern
Paraquat dichloride is a non-selective herbicide currently registered for the control of weeds and
grasses in agricultural and non-agricultural areas. It is a contact herbicide that desiccates and
destroys plant cell membranes within hours of application. Paraquat is only formulated as a
soluble concentrate/liquid (SC/L) formulation. It can be applied pre-plant, pre-emergence, at
plant, or post-emergence; or as a desiccant/harvest aid or a postharvest desiccant. Paraquat may
be applied to agricultural and non-agricultural areas (e.g., conservation reserve program areas,
non-crop lands, and pasture lands) with aerial, ground, and handheld spray equipment. It is a
RUP; therefore, there are no paraquat products registered for homeowner use and no products
registered for application to residential areas.
All registered labels require occupational handlers (mixers and loaders) to wear baseline
clothing, chemical resistant gloves, aNIOSH approved half-mask respirator, as well as a
chemical resistant apron and face shield. Applicators and other handlers (other than mixers and
loaders) must wear baseline clothing, chemical resistant gloves, a NIOSH approved half-mask
respirator, as well as protective eyewear.
Page 20 of 103
-------
The registered uses of paraquat are summarized in the Line by Line, and Maximum Use Scenario
Pesticide Label Usage Summary (PLUS) Reports as generated by OPP's Biological and
Economic Analysis Division (BEAD). Application rates provided by these sources are presented
in Appendix D, Table D.l. For purpose of the occupational and non-occupational spray drift risk
assessments, HED has used the maximum application rates for all crops and equipment types.
3.3 Anticipated Exposure Pathways
Humans may be exposed to paraquat in food and drinking water since paraquat may be applied
directly to growing crops and application may result in it reaching surface and ground water
sources of drinking water. Paraquat is a RUP; therefore, there are no paraquat products
registered for homeowner use and no products registered for application to residential areas.
Non-occupational exposures may occur as a result of spray drift from off-target applications of
paraquat. Occupational handler and post-application exposures are expected from paraquat
usage. This risk assessment considers all the aforementioned exposure pathways based on the
existing paraquat uses.
3.4 Consideration of Environmental Justice
Potential areas of environmental justice concerns, to the extent possible, were considered in this
human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions
to Address Environmental Justice in Minority Populations and Low-Income Populations3." As a
part of every pesticide risk assessment, OPP considers a large variety of consumer subgroups
according to well-established procedures. In line with OPP policy, HED estimates risks to
population subgroups from pesticide exposures that are based on patterns of that subgroup's food
and water consumption, and activities in and around the home that involve pesticide use in a
residential setting. Extensive data on food consumption patterns are compiled by the USDA's
NHANES/WWEIA and are used in pesticide risk assessments for all registered food uses of a
pesticide. These data are analyzed and categorized by subgroups based on age and ethnic group.
Additionally, OPP is able to assess dietary exposure to smaller, specialized subgroups, and
exposure assessments are performed when conditions or circumstances warrant. Whenever
appropriate, non-dietary exposures are also evaluated based on home use of pesticide products
which includes calculating associated risks for adult applicators and for toddlers, youths, and
adults entering or playing in previously treated areas. Spray drift can also potentially result in
exposure and it was also considered in this analysis. Further considerations are currently in
development, as OPP has committed resources and expertise to the development of specialized
software and models that consider exposure to bystanders and farm workers as well as lifestyle
and traditional dietary patterns among specific subgroups.
4.0 Hazard Characterization and Dose-Response Assessment
4.1 Toxicology Studies Available for Analysis
The toxicology database for paraquat is complete and adequate for Registration Review.
Characterization of paraquat toxicity in mammals was informed both by guideline and non-
guideline studies submitted to the Agency and relevant mammalian toxicity studies identified in
3 Available: http://www.archives.gov/federal-register/executive-orders/pdf/12898.pdf
Page 21 of 103
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the open literature. The paraquat toxicology database consists of the following guideline and
non-guideline studies:
• Acute oral, dermal, inhalation, eye irritation, dermal irritation, and skin sensitization
studies
• 90-day oral toxicity study - dog
• 21-day dermal toxicity study - rabbit
• 21-day inhalation study - rat
• Prenatal developmental toxicity study - rat and mouse
• Multi-generation reproduction study - rat
• Combined oral chronic toxicity/carcinogenicity study - rat
• Carcinogenicity study - mouse
• Chronic oral toxicity study - dog
• Acute and sub chronic neurotoxicity studies - rat
• Mutagenicity battery
• Immunotoxicity study - mouse
• Non-guideline in vivo dermal absorption study - human
• Non-guideline intraperitoneal injection neurotoxicity studies - mouse
A guideline non-rodent developmental study and guideline metabolism and pharmacokinetics
study were not available at the time of Registration Review. These are not considered gaps in
the toxicity database, as the Hazard and Science Policy Council (HASPOC; TXR 0056294, K.
Rury, 04/12/2012) recommended waiving the requirement for a prenatal developmental study in
non-rodents, and suitable open literature studies were submitted to fulfil the metabolism and
pharmacokinetics requirement. Therefore, there are no outstanding guideline data gaps in the
paraquat toxicity database.
As part of Registration Review for paraquat, a broad survey of the literature was conducted to
identify studies that report toxicity following exposure to paraquat via exposure routes relevant
to human health pesticide risk assessment not accounted for in the Agency's paraquat toxicology
database. The search strategy employed terms restricted to the name of the chemical plus any
common synonyms, and common mammalian models to capture as broad a list of publications as
possible for the chemical of interest. The search strategy returned 3971 studies from the
literature. During title/abstract and full text screening of these studies, nine were identified as
containing potentially relevant information (either quantitative or qualitative) for the paraquat
human health risk assessment. An additional 17 relevant studies were identified in the
Parkinson's disease (PD) systematic review discussed in the next paragraph. In total, 26 studies
from the open literature were evaluated. Full text review of this subset pared down the list to 10
studies that were of sufficient quality and contained either quantitative or qualitative information
relevant to the risk assessment. Only one study, Lou et al. (2016) 4, reported evidence of adverse
health effects in mice at doses that were similar to the current POD. This study was formally
reviewed (MRID 50733301; TXR 0057886) and was considered in the selection of the PODs.
The data reported in the other nine publications did not have a quantitative impact on the risk
assessment; however, the studies did report novel findings, including toxicokinetic and
neurotoxicity information, that were incorporated into the hazard characterization of the
Registration Review risk assessment. Refer to the paraquat general literature review memo
4 Lou D, Wang Q, Huang M, and Zhou Z. 2016. Does age matter? Comparison of neurobehavioral effects of paraquat exposure
on postnatal and adult C57BL/6 mice. Toxicol Mech Method. 26(9): 667-673.
Page 22 of 103
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(D449107; TXR 0057887, A. Wray, 06/26/2019) and Appendix A.4 for more details on the
search strategy, inclusion/exclusion criteria, literature review criteria, and the conclusions of the
general literature review.
In addition to the general literature review, two focused systematic reviews were conducted: 1) a
review of the human, animal, and in vitro literature evaluating the strength of evidence
associating paraquat exposure from pesticidal use to PD (the PD systematic review); and 2) a
review of the epidemiology literature evaluating all reported outcomes related to paraquat
exposure including PD (the epidemiology review). The PD data gathered for the epidemiology
review were also incorporated into the PD systematic review. The results of the systematic
reviews and their implications on the Agency's risk assessment for current paraquat registrations
are summarized in Sections 4.3.1 and 4.3.2. More details on the PD systematic review and the
epidemiology systematic review can be found in the PD systematic review memo (D449106;
TXR 0057888, A. Wray, 06/26/2019) and paraquat epidemiology review memo (D449108, A.
Niman, 06/26/2019), respectively.
4.2 Absorption, Distribution, Metabolism, and Excretion (ADME)
A guideline metabolism and pharmacokinetics study is not available for paraquat. Previous risk
assessments relied on data from published studies submitted to fulfill the metabolism data
requirement [Daniel and Gage 19665 (MRID 00055107) Litchfield et al. 19736 (MRID
00065592)]. Much of the information presented in those studies is consistent with more recent
investigations; therefore, those data are discussed below alongside distribution data from the
guideline oral toxicity studies (MRID 00132474, 00138637, and 49009501) and new data from
more recent publications that address aspects of the ADME not investigated by the older
literature or guideline studies.
Paraquat is poorly absorbed and efficiently eliminated by rats following oral administration
(Daniel and Gage 1966). Oral absorption (based on urinary data) from a low dose (4-6 mg/kg)
gavage exposure was approximately 6% of the administered dose (AD) and increased to 8-14 %
when the dose was increased 10-fold (50 mg/kg). No evidence of biliary excretion was observed
following an oral dose of 0.5 mg/kg in the same study; however, the study authors did not
determine the extent of biliary excretion at higher doses. Hughes et al. (19737) reported a similar
finding: <1% of the AD in the bile 24 hours after intraperitoneal (IP) injection of 15 mg/kg
aqueous paraquat diiodide in rats. Collectively, these data suggest biliary excretion is not a
prominent elimination pathway for absorbed paraquat. At low doses, rats primarily excreted
ingested paraquat in the feces (93-96% of the AD) with minor contribution from the renal system
and a majority of the AD (>95%) was eliminated within 48 hours. It appears this pattern persists
at higher doses based on the urine data, but no fecal data were provided to confirm. Rabbits
exhibited a similar pattern of limited oral absorption and efficient elimination at low oral doses
(2 mg/kg); however, elimination was impeded by reduced urinary and fecal output at higher
doses (30 mg/kg) that was likely related to kidney toxicity that altered renal function (MRID
49009501). The excretion profile of paraquat changed markedly with the route of
administration. After subcutaneous injection (12.5-13.2 mg/kg paraquat) in rats, 80-98%) of the
5 Daniel JW and Gage JC. 1966. Absorption and excretion of diquat and paraquat in rats. BritJIndustrMed. 23(2): 133
6 Litchfield MH, Daniel JW, and Longshaw S. 1973. The tissue distribution of the bipyridylium herbicides diquat and paraquat in
rats and mice. Toxicology. 1: 155-165.
7 Hughes RD, Millburn P, and Williams RT. 1973. Biliary excretion of some diquaternary ammonium cations in the rat, guinea
pig and rabbit. Biochem. J. 136: 979-984.
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AD was identified in the urine within 24 hours of dosing (Daniel and Gage 1966). Likewise,
84% of the AD was quantified in the urine 24 hours after an IP injection (15 mg/kg paraquat
diiodide; Hughes etal. 1973).
Orally absorbed paraquat was distributed to the lungs, kidneys, and liver in rats and rabbits
(Litchfield et al. 1973, MRID 00138637, and MRID 49009501) and to the lungs and kidneys in
dogs (MRID 00132474). Paraquat content accumulated in rats from up to 8 weeks of exposure
did not persist longer than a week in the lung, kidney, or liver tissue after returning to a normal
diet. Persistence following chronic exposure in dogs and rats was not investigated. Brain tissues
were not identified as a primary site of distribution in the Litchfield etal. (1973) study; however,
recent studies from the open literature demonstrate distribution of paraquat to brain tissue in
rodents (Widdowson etal. 19968; Minnema etal. 20149) and specifically to midbrain tissues in
mice (Prasad et al. 200710) following acute and repeat oral dosing.
The available data suggest that absorbed paraquat is excreted mostly as unchanged parent.
Although -30% of an orally administered dose was identified in the feces as chemically distinct
from parent, in vitro studies indicate it was likely due to microbial degradation in the gut (MRID
00055107). A small fraction (1.2-2.1% of the AD) of the urinary excreta was also determined to
be structurally different from parent. However, this finding more likely represents absorption of
the degradates rather than metabolites formed after absorption, which is supported by the lack of
metabolites in the urine of rats exposed subcutaneously (same study) or IP (Hughes et al. 1973).
4.2.1 Dermal Absorption
Dermal absorption was estimated based on the results of an in vivo dermal absorption study
conducted in humans (MRIDs 00126097, 00126098, 00126099). These studies were reviewed
by an Agency Human Research Ethics reviewer and it was determined that they were ethically
acceptable for use in risk assessment11. The reviewer also indicated a review by the Human
Studies Review Board was not required because the studies did not measure or identify a toxic
effect. Human volunteers were administered 8.6 |ig paraquat ion/cm2 on the forearms, back of
hands, and back of the lower legs and instructed to refrain from washing the application site for
24 hours. The dermal dose (~ 0.008 mg paraquat ion/kg based on 80 kg human) was well below
that which elicited skin irritation in the repeat dose dermal study. Dermal absorption was
estimated based on total paraquat content excreted in the urine within a 5-day period (collecting
during the exposure and every 24 hours for four days after the wash) and corrected for
incomplete urinary excretion based on the excretion patterns observed in Rhesus monkeys
(MRID 00126096). The study did not indicate if they looked for dermal lesions on the human
volunteers; however, it is assumed that the skin was intact based on the low dermal dose
selected. Average dermal absorption estimates ranged from 0.23 to 0.30% of the administered
dose indicating it is poorly absorbed across intact skin.
8 Widdowson PS, Farnworth MJ, Upton R, and Simpson MG. 1996. No changes in behavior, nigro-striatal system
neurochemistry or neuronal cell death following toxic multiple oral paraquat administration to rats. Hum. Exp. Toxicol. 15(7):
583-591.
9 Minnema DJ, Travis KZ, Breckenridge CB, Sturgess NC, Butt M, Wolf JC, Zadory D, Beck MJ, Mathews JM, Tisdel MO,
Cook AR, Botham PA, and Smith LL. 2014. Dietary administration of paraquat for 13 weeks does not result in a loss of
dopaminergic neurons in the substantia nigra of C57BL/6J mice. Regul Toxicol Pharm. 68(2): 250-258.
10 Prasad K, Winnik B, Thiruchelvam MJ, Buckley B, Mirochnitchenko O, and Richfield EK. 2007. Prolonged toxicokinetics and
toxicodynamics of paraquat in mouse brain. Environ. Health Persp. 115(10): 1448-1453.
11 K. Sherman. Ethics Review of Excretion Study with Human Subjects. 06/11/2012.
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The assumption that paraquat does not readily cross the skin may not, however, hold true for
higher dermal doses. Repeat dermal dosing is known to elicit dermal toxicity at relatively low
topical doses (2.6-6 mg paraquat ion/kg/day) in the laboratory and skin damage is the most
common symptom observed in human incidents related to dermal exposure. Observations in the
toxicity database and human incident report suggest that, at its most severe, the damage elicited
by paraquat could compromise the dermal barrier, allowing greater access to circulation
compared to intact skin and increasing the likelihood of systemic toxicity. Understanding the
relationship between the corrosive behavior of paraquat and dermal absorption is thus critical to
estimating systemic toxicity for paraquat dermal exposures; however, the toxicity database does
not explore this relationship at doses > 6 mg paraquat ion/kg/day, in part due to welfare concerns
for in vivo models. In lieu of data suggesting otherwise, the progressive skin damage observe in
the toxicity database is anticipated to progress in severity with increasing dose resulting in higher
dermal absorption at dermal doses that exceed the range characterized in the toxicity database.
4.3 Toxicological Effects
The primary target organ of paraquat is the lungs. Evidence of lung inflammation, scarring, and
compromised lung function in response to paraquat exposure are observed throughout the
toxicity database in different species (rats, mice, and dogs). Effects in the respiratory tract are
observed after single and repeat dose exposures regardless of the route of exposure (oral or
inhalation); however, inhalation was a more sensitive route of exposure than the oral route in
both acute (Category I and II, respectively) and repeat dose studies. Paraquat dichloride is
moderately to severely irritating to mucous membranes (Toxicity Category II for eye irritation)
leading to portal of entry toxicity in the upper respiratory tract (squamous keratinizing
metaplasia and hyperplasia of the larynx epithelium) from repeated inhalation. In dogs,
respiratory toxicity was consistently observed following oral exposure regardless of duration and
at doses below those observed in the other species tested. The toxicity profile in rodents was
more diverse with effects observed in other organ systems following longer duration oral
exposure. These effects include inflammation and necrosis of the kidneys in mice and lenticular
(eye lens) changes in rats. In mice, the kidney effects were observed in the absence of notable
lung toxicity suggesting the mouse renal system was more vulnerable to prolonged repeated
exposure. Rodents also exhibited various clinical signs (piloerection, pinched sides, hunched
posture, hypoactivity, weight loss/thin appearance and respiratory distress) when exposed via
gavage and were considered to represent an agonal response to a bolus dose. Mortality was
observed in all species tested and at doses/concentrations as low as 3 mg paraquat ion/kg/day and
1.3 |ig paraquat ion/L/day for oral and inhalation exposure, respectively. Death from acute
exposure was not always immediate; mortalities after acute oral gavage exposure, for example,
were noted up to a week after exposure in rats and were preceded by the clinical signs described
above. A similar delay between single dose exposure and death was described in several human
ingestion incidents in the incident report.
Renal toxicity was also a hallmark of paraquat toxicity in rabbits. Acute oral exposure elicited
loss of appetite, body weight loss, and progressive proximal tubule degeneration, resulting in
reduced fecal output and urine flow. Interestingly, none of the characteristic lung effects that
define the paraquat toxicity profile in other species were observed in rabbits following acute
exposure. Nevertheless, rabbits were more sensitive to acute oral exposure compared to rodents
with at least a 2-fold separation in the estimated median lethal dose.
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Paraquat causes minimal skin irritation in rabbits following acute dermal exposure (Toxicity
Category IV) and elicits a more varied and corrosive dermal response (scabbing, hyperkeratosis,
epidermal erosion/ulceration, surface exudation, acanthosis, and inflammation) with prolonged
exposure. This response is consistent with dermal toxicity described in the human incident
report. Skin damage was the most commonly reported symptom for human incidents resulting
from occupational use and ranged from blisters and dry skin to chemical burns and lesions. The
first signs of skin irritation and damage in rabbits from repeat dosing occurred at relatively low
topical doses (2.6 mg paraquat ion/kg/day) and evolved in diversity and severity with duration
and dose. No evidence of systemic toxicity was observed in rabbits following 21 days of dermal
exposure up to 6 mg paraquat ion/kg (the highest dermal dose evaluated in the toxicity database)
indicating that the skin remained an effective barrier in this dose range despite the structural
damage elicited by paraquat. Systemic toxicity is anticipated to result from higher dermal doses
that further corrode the skin integrity and allow unimpeded access to the bloodstream. No
mortalities were noted following acute dermal exposure in rats up to 2000 mg technical
concentrate/kg (paraquat ion was not calculated; Toxicity Category III), though all animals
exhibited signs of slight to moderate skin irritation. Paraquat is not a skin sensitizer.
Paraquat did not cause reproductive toxicity. Developmental and offspring toxicity observed in
the guideline studies in response to paraquat exposure always occurred in the presence of
parental toxicity; therefore, there was no evidence of quantitative susceptibility. Developmental
effects included reduced body weight/gain and delayed skeletal ossification and were observed at
the same doses that elicited respiratory distress, reduced body weight, lung lesions, and mortality
in maternal animals. Offspring effects were limited to sporadic histopathology lesions at
parentally toxic doses that were approximately 10X higher than the doses eliciting lung effects in
dogs (the most sensitive species). However, a review of the open literature identified age-
dependent quantitative sensitivity that was not captured in the guideline studies. Mortality in
three-week-old mice was observed at a lower dose level compared to 8-week old mice following
acute and subchronic gavage exposure to a high purity paraquat product (>98% a.i.; Lou el al.
2016).
The guideline studies did not report evidence of neurotoxicity or immunotoxicity in rodents up to
doses that are known to cause respiratory distress. The impact of paraquat exposure on the
nervous system and its relationship to PD was further characterized in the PD and epidemiology
systematic reviews. The results of the epidemiology review including the evaluation of the body
of evidence for PD is presented in Section 4.3.1. The conclusions of the PD systematic review
are discussed in Section 4.3.2.
4.3.1 Epidemiology Review Summary
OPP performed a systematic review of the epidemiologic literature on paraquat exposure and
identified 74 articles that investigated a range of health outcomes, including PD, lung function
and respiratory effects, cancer, and other health outcomes. Further information on OPP's review
and evaluation of the available epidemiologic literature is available in the Paraquat Tier II
Epidemiology Report (D449108, A. Niman, 06/26/2019).
PD had the most comprehensive body of epidemiologic literature with a total of 13 study
populations, including three agricultural cohorts, nine hospital-based populations, and one PD
registry in Nebraska (26 articles). Based on the findings from these studies, it was concluded:
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• There is limited, but insufficient epidemiologic evidence at this time to conclude that there
is a clear associative or causal relationship between occupational paraquat exposure and
PD. This conclusion is based on mixed findings reported in the Agricultural Health
Study (AHS) and Farming and Agricultural Movement Evaluation Study ' - with
respect to incident and prevalent cases - and the potential for recall bias. In examination
of evidence from other occupational studies, no association was observed in either the
French Agriculture and Cancer Cohort14 or the cohort from Washington State.15
Similarly, mixed evidence was reported in the remaining three case-control studies, with
one study reporting evidence of a positive association in Taiwan,16 one study reporting a
non-significant positive association based on only nine exposed cases,17 and one study
reporting no evidence of an association in the Netherlands.18 However, these case-control
studies contributed less weight in OPP's determination because of their weaker study
designs, more limited exposure assessment approach, and potential for recall bias.
• There is insufficient epidemiologic evidence at this time to conclude there is a clear
associative or causal relationship between non-occupational paraquat exposure and PD.
This conclusion was based on the limited number of studies on non-occupational
populations, lack of consistent evidence of a positive association, and the potential for
bias in the available studies. The California Parkinson's Environment and Genes Study
reported evidence of a positive association between paraquat exposure and PD in some
publications, for example, but reported no evidence of an association when restricting
analysis to paraquat exposure only.19 A similar case-control study conducted in the
Netherlands reported no evidence of a positive association.20 Both studies relied on
geospatial data to estimate exposure which eliminated the potential for recall bias, but
may have limited ability to distinguish between proximity to agricultural land, pesticide
exposure in general, and specific pesticides as potential PD risk factors with confidence.
The results of the ecologic Nebraska Parkinson's Disease Registry Study contributed
limited weight to Agency OPP's evaluation because of its more limited study design, but
12 Kamel F, Tanner CM, Umbach DM, Hoppin JA, Alavanja MCR, Blair A, Comyns K, Goldman SM, Korell M, Langston JW,
Ross GW, Sandler DP. Pesticide exposure and self-reported Parkinson's disease in the Agricultural Health Study. Am J
Epidemiol. 2007, 165(4):364-374.
13 Tanner CM, Kamel F, Ross GW, Hoppin JA, Goldman SM, Korel M, et al. Rotenone, paraquat, and Parkinson's disease.
Environ Health Perspect. 2011, 119:866-872.
14 Pouchieu C, Piel C, Carles C, Gruber A, Helmer C, Tual S, Marcotullio E, Lebailly P, Baldi I. Pesticide use in agriculture and
Parkinson's disease in the AGRICAN cohort study. Int J Epidemiol. 2018, 47(1):299-310.
15 Engel LS, Checkoway H, Keifer MC, Seixas NS, Longstreth WT Jr, Scott KC, Hudnell K, Anger WK, Camicioli R.
Parkinsonism and occupational exposure to pesticides. Occup Environ Med. 2001, 58(9):582-9.
16 Liou HH, Tsai MC, Chen CJ, Jeng JS, Chang YC, Chen SY, Chen RC. Environmental risk factors and Parkinson's disease: A
case-control study in Taiwan. Neurol. 1997, 48:1583-1588.
17 Tanner CM, Ross GW, Jewell SA, Hauser RA, Jankovic J, Factor SA, Bressman S, Deligtisch A, Marras C, Lyons KE,
Bhudhikanok GS, Roucoux DF, Meng C, Abbott RD, Langston JW. Occupation and risk of parkinsonism: a multicenter case-
control study. Arch Neurol. 2009 Sep; 66(9): 1106-13.
18 van der Mark M, Vermeulen R, Nijssen PCG, Mulleners WM, Sas AMG, van Laar T, Brouwer M, Huss A, Kromhout H.
Occupational exposure to pesticides and endotoxin and Parkinson disease in the Netherlands. Occup Environ Med. 2014,
71(ll):757-764.
19 Costello S, Cockburn M, Bronstein J, Zhang X, Ritz B. Parkinson's disease and residential exposure to maneb and paraquat
from agricultural applications in the central valley of California. Am J Epidemiol. 2009, 169(8):919-926.
20 Brouwer M, Huss A, van der Mark M, Nijssen PCG, Mulleners WM, Sas AMG, van Laar T, de Snoo GR, Kromhout H,
Vermeulen RCH. Environmental exposure to pesticides and the risk of Parkinson's disease in the Netherlands. Environ Int. 2017,
107:100-110.
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• highlight the need to carefully account for rurality in the design and analysis of studies on
paraquat exposure and PD.21
In order to strengthen the available evidence, future epidemiologic studies on PD should aim to
minimize recall bias and more systematically evaluate paraquat exposure specifically using an
approach that addresses co-exposure to other pesticides and evaluates other factors that may be
associated with rural living.
Lung function and respiratory effects were examined in nine study populations (17 articles) that
included general lung function, wheeze, allergic rhinitis, asthma, and chronic bronchitis. Based
on the findings from these studies, it was determined there is insufficient epidemiologic evidence
at this time to conclude that there is a clear associative or causal relationship between
occupational paraquat exposure and the health outcomes investigated, including: general lung
function and respiratory symptoms, wheeze, allergic rhinitis, asthma, and chronic bronchitis.
While 17 articles were identified, the quality of evidence was determined to be low for all studies
because they used a cross-sectional design that could not evaluate the temporal association
between paraquat exposure and onset of the health outcomes of interest. Additionally, many
studies were conducted outside the United States and may not be generalizable because they
focused on regions with different agricultural practices and study populations with different
demographic and lifestyle characteristics.
Cancer outcomes were only investigated in four study populations (eight articles) that examined
occupational paraquat exposure. Most cancer outcomes investigated in only a single study,
typical AHS. Based on the findings from these studies, it was determined that there is
insufficient epidemiological evidence to conclude that there is a clear associative or causal
relationship between occupational paraquat exposure and the health outcomes investigated,
including: general lung function and respiratory symptoms, wheeze, allergic rhinitis, asthma, and
chronic bronchitis. While 17 articles were identified, all studies were determined to be low
quality because they used cross-sectional designs and could not evaluate the temporal association
between paraquat exposure and onset of the health outcomes of interest. Additionally, some
studies were conducted outside the United States and may not be generalizable because they
focused on regions with different agricultural practices and study populations with different
demographic and lifestyle characteristics.
Seventeen other health outcomes (25 articles) were investigated in the literature primarily
examined occupational paraquat exposure. Most outcomes were only investigated in a single
study population. OPP concluded there was no epidemiological evidence of an association for the
health outcomes general mortality, suicide, and infant birth weight. For health outcomes with a
single study with positive findings (OR >1.0 and significant), it was generally concluded there
was insufficient evidence of an association for health outcomes. This included the health
outcomes diabetes, myocardial infarction, eye disorders, injury mortality, renal/liver function,
oxidative stress, abnormal skin pigmentation, actinic keratosis, depressive symptoms, thyroid
disease, and aplastic anemia. OPP concluded there was limited, but insufficient evidence of a
clear associative or causal relationship for end-stage renal disease, based on AHS studies on
21 Wan N and Lin Y. Parkinson's Disease and Pesticides Exposure: New Findings From a Comprehensive Study in Nebraska,
USA. J Rural Health. 2016; 32(3): 303-13.
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male farmers that both reported evidence of a positive association.22,23 While positive
associations were reported, there were only a small number of paraquat cases in both studies (21
and 33, respectively), so the ability to assess the exposure-response relationship was limited. As
such, while both AHS studies reported positive findings, further investigation is warranted to
replicate the results in studies with a larger number of cases and other study populations that may
experience chronic paraquat exposure.
4.3.2 Parkinson's Disease Systematic Review
The central nervous system has received considerable attention in the paraquat literature with an
emphasis on PD hallmarks including accumulation of a-synuclein in neurons (Lewy bodies),
degeneration of vulnerable neuron populations including dopaminergic neurons in the midbrain,
depletion of dopamine in the striatum, and impairment of motor and non-motor function. The
OPP toxicity database does include several studies that explore general neurotoxicity and PD-
specific hallmarks; however, the Agency recognizes that these studies represent a small fraction
of the available literature on neurotoxic outcomes related to paraquat exposure and PD.
As part of Registration Review, the Agency conducted a fit-for-purpose systematic review to
evaluate the significance and environmental relevance of the postulated association between
paraquat exposure and PD. A literature database for the PD systematic review was compiled
from three primary sources of data: the OPP paraquat toxicity database for registration, the OPP
paraquat epidemiology review (summarized in 4.3.1), and the National Toxicology Program
(NTP) scoping review of open literature relevant to evaluating the association between paraquat
exposure and PD. Data from the studies were separated into three lines of evidence - human,
animal, and in vitro - and evaluated for quality, substance, and environmental relevance.
Environmental relevance was defined as the likelihood that a given effect would result from an
exposure scenario anticipated to occur from typical use of registered paraquat products (e.g. oral
including dietary, dermal and inhalation exposure). The Agency integrated environmental
relevance considerations into the systematic review in order to contextualize hazard information
in terms of risk. Studies that were of sufficient quality and investigated environmentally relevant
exposure scenarios were then evaluated in their respective body of evidence and collectively
across lines of evidence in the weight of evidence analysis. The conclusions of the PD systematic
review are presented here and more information on the methods, review criteria, and study
evaluations can be found in the PD systematic review memo (D449106; TXR 0057888, A. Wray,
06/26/2019).
A screen of the open literature and OPP toxicity database returned 28, 217, and 244 human,
animal, and in vitro studies, respectively, that were relevant to evaluating the association
between paraquat exposure and PD. Further review of the relevant animal open literature
revealed that many of the studies used injection as the route of administration or were conducted
with alternative mammalian models. The Agency acknowledges that a number of injection
studies report PD-like effects in rodents following exposure to paraquat; however, injection is
not representative of the anticipated exposure scenarios for registered uses of paraquat due to
differences in toxicokinetic behavior. These studies were thus excluded from consideration in the
PD systematic review due to a lack of environmental relevance. Likewise, studies conducted
22 Lebov JF, Engel LS, Richardson D, Hogan SL, Hoppin JA, Sandler DP. Pesticide use and risk of end-stage renal disease
among licensed pesticide applicators in the Agricultural Health Study. Occup Environ Med. 2016, 73:3-12.
23 Lebov JF, Engel LS, Richardson D, Hogan SL, Sandler DP, Hoppin JA. Pesticide exposure and end-stage renal disease risk
among wives of pesticide applicators in the Agricultural Health Study. Environ Res. 2015,143(Pt A): 168-210.
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with alternative mammalian models were excluded because they were determined to be of
limited use to evaluating human health risk. Study evaluation of the in vitro database focused on
the studies that reported the most sensitive response for relevant outcomes within the human and
rodent models due to the density of relevant studies available. The in vitro studies excluded from
study evaluation either presented results that were not meaningfully different from those reported
in the evaluated studies, reported outcomes that were not relevant to the weight of evidence
analysis, and/or the reported results indicated the in vitro model examined was not more
sensitive than the relevant models discussed for a particular outcome. Additional studies from all
three lines of evidence were excluded based on insufficient quality. In total, data from 26, 11,
and 34 studies were considered in the evaluation of the human, animal, and in vitro evidence,
respectively, and integrated in the weight of evidence analysis. In addition, the 11 acceptable
animal studies were considered in the selection of PODs for the Registration Review risk
assessment.
Evaluating the link between paraquat exposure and PD is reliant on the strength, consistency, and
coherence of PD or PD-like hallmarks within and across the human, animal, and in vitro lines of
evidence, and concordance with toxicokinetic and mechanistic data. Some evidence connecting
environmentally relevant paraquat exposure to motor, neuropathological, and/or neurochemical
hallmarks of PD was reported in the acceptable literature compiled for this systematic review;
however, confidence in these positive findings was diminished by gaps in the dose and temporal
concordance, mixed and conflicting results between and across lines of evidence, and unresolved
uncertainties in the studies and overall weight of evidence.
The 26 human studies were the same epidemiology studies identified in the paraquat
epidemiology review (discussed in more detail in Section 4.3.1). These studies reported findings
on 13 study populations, including three agricultural cohorts, nine hospital-based populations,
and one PD registry in Nebraska. These study populations may have been exposed to paraquat
through occupational and non-occupational exposure pathways that vary in terms of magnitude,
frequency, and duration, with occupational study populations being more likely to experience
exposure as a result of direct use of paraquat. With respect to occupational exposure, it was
determined that there is limited, but insufficient epidemiologic evidence of a clear associative or
causal relationship. This conclusion was based on mixed findings in both the AHS cohort and
other study populations. These studies may all be subject to uncertainty due to limitations in their
design, exposure assessment approach, and potential for bias. With respect to non-occupational
study populations, evidence from three study populations was evaluated and it was determined
that there is insufficient epidemiologic evidence of a clear associative or causal relationship.
This conclusion was based on the small number of studies on non-occupational populations, lack
of consistent evidence of a positive association, and the potential for bias.
Empirical evidence of motor impairment in laboratory animals was observed in male mice
following oral exposure for at least 28 days to doses >7.2 mg paraquat ion/kg/day (10 mg
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dichloride/kg/day)24'25'26. These findings were the strongest evidence of neurotoxicity attributed
to paraquat in the animal literature evaluated for this systematic review. The behavioral changes
were observed across several studies that used a high purity paraquat product and exhibited a
large magnitude of change from controls. Motor impairment was, however, not observed in
female mice nor in rats of either sex after oral exposure to paraquat. Only one animal study (Ren
et al. 2009)24 presented evidence to suggest the observed motor impairment in male mice was
connected to dopaminergic neuron degeneration and neurochemical disruption - two hallmarks
integral to the pathology of PD in humans - but there was not enough information in this study
nor collectively in the animal literature to evaluate consistency, dose response, or temporal
concordance of these findings. Toxicokinetic, in vitro, and mechanistic data added credibility to
the positive findings in male mice but the lack of supporting empirical evidence for tissue,
cellular, and biochemical PD-like hallmarks in the animal studies diminish confidence that the
observed motor impairment was a result of a PD-like pathology in mice. Other environmentally
relevant routes of exposure were less studied in the literature. No reliable evidence of PD-like
hallmarks was observed in mice or rats after repeated intranasal exposure, which was consistent
with the toxicokinetic data indicating paraquat did not distribute to the ventral midbrain or
striatum after acute exposure. No data were available to evaluate PD-like hallmarks following
dermal exposure; however, systemic paraquat concentration is expected to be low following
dermal exposure provided the dermal dose does not reach levels that affect the integrity of the
skin. Overall, the limited, mixed findings in the animal literature were considered weak evidence
of a PD-like response to paraquat exposure.
Qualitative similarities in the positive findings for in vitro and behavioral outcomes between
rodents and humans indicated some interspecies coherence in the neurological response to
paraquat exposure; however, there was a lack of coherence for tissue, cellular, subcellular, and
biochemical PD hallmarks, in part because few animal studies and no human studies investigated
these hallmarks. The small number of positive findings and the lack of consistency in the
findings in the human studies also diminished confidence in the biological plausibility of the
animal and in vitro findings. Occupational and dietary exposure in humans resulting from
pesticidal use of paraquat products currently registered in the United States is not estimated to
reach external dose levels that elicited PD-like effects in whole animal studies. These estimates
may not apply for uses outside of the United States but do suggest that the PD-like outcomes
observed in the laboratory are not likely to occur from label-directed use in the US. Given the
weakness within and across lines of evidence and the exposure considerations outlined above,
the Agency concluded that the weight of evidence was insufficient to link paraquat exposure
from pesticidal use of US registered products to PD in humans. The Agency did not evaluate the
adverse outcome pathways (AOP) proposed in the open literature nor develop one from the data
gathered in the systematic review. Given the lack of sufficient evidence for a causal association,
the Agency did not consider an AOP necessary to characterize paraquat toxicity and evaluate risk
for registered products.
24Ren JP, Zhao YW, and Sun XJ. 2009. Toxic influence of chronic oral administration of paraquat on nigrostriatal dopaminergic
neurons in C57BL/6 mice. Chin Med J. 122(19): 2366-2371.
2BSatpute RM, Pawar PP, Puttewar S, Sawale SD, and Ambhore PD. 2017. Effect of resveratrol and tetracycline on the subacute
paraquat toxicity in mice. Hum Exp Toxicol. 36(12): 1303-1314.
26 Lou D, Wang Q, Huang M, and Zhou Z. 2016. Does age matter? Comparison of neurobehavioral effects of paraquat exposure
on postnatal and adult C57BL/6 mice. Toxicol Mech Method. 26(9): 667-673.
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The findings of this systematic review were integrated with the rest of the paraquat toxicity
profile in the hazard characterization and were considered in the POD selection and uncertainty
factor determination for the Registration Review human health risk assessment. In selecting the
most sensitive POD to estimate risk, the Registration Review risk assessment accounted for all
forms of treatment-related adversity reported for paraquat including the neurotoxic effects
discussed in this systematic review. The toxicity profile for paraquat indicates that contact
toxicity and effects in the respiratory and renal system occur at lower doses than those eliciting
neurotoxicity in animal models. Paraquat is also lethal to pregnant rats at the doses reported to
elicit neurotoxicity. Based on these findings, it is expected that a multitude of contact and
systemic effects would precede the PD-like neurotoxic effects reported in the literature. Contact,
renal, and respiratory toxicity are, therefore, of greater concern to human health and more
relevant to assessing risk from paraquat exposure during routine use of pesticidal products with
US registration. PODs selected for risk assessment were thus based on the more sensitive
respiratory effects and are protective of the neurotoxic effects attributed to paraquat exposure
discussed in the PD systematic review.
4.4 Safety Factor for Infants and Children (FQPA Safety Factor)27
The paraquat risk assessment team recommends reducing the FQPA SF to IX. The dietary
assessments are based on reliable data and will not underestimate exposure. The paraquat
toxicity database, with contributions from the open literature, is adequate to evaluate the
potential for susceptibility in infants and young children resulting from exposure to paraquat.
There was no evidence of quantitative developmental or offspring susceptibility in the guideline
rodent studies and the HASPOC recommended waiving the non-rodent developmental study
requirement because it was not anticipated to provide data or information that would impact risk
assessment (TXR 0056294, K. Rury, 04/12/2012). Limited evidence of age-related sensitivity
was observed in the open literature, but only from exposure to a high purity paraquat product
(>98% purity), which is not representative of the lower purity technical paraquat products and
formulations (<48% purity) undergoing Registration Review. The PODs selected for risk
assessment account for toxicity from exposure to paraquat sources that are analogous to the
technical product and are thus protective of the developmental and offspring effects resulting
from exposure to the registered technical products and lower purity formulations. Limited
evidence of neurotoxicity including PD-like outcomes was noted in the toxicology database and
in the open literature; however, the weight of evidence compiled from relevant human, animal,
and in vitro studies was considered insufficient to conclude that there is a causal relationship
between paraquat exposure from pesticidal use and PD. Lung and respiratory tract toxicity were
more sensitive endpoints compared to the neurotoxic and other systemic effects reported in the
open literature, thus the PODs selected for risk assessment based on these effects are protective
of all known health effects resulting from paraquat exposure.
4.4.1 Completeness of the Toxicology Database
The paraquat toxicology database coupled with the general literature review and the Parkinson's
disease systematic review provided adequate information to assess risk for infants and young
children. Acceptable guideline developmental, multi-generation reproduction, and acute and
subchronic neurotoxicity studies were used to characterize toxicity for these critical life-stages.
27 HED's standard toxicological, exposure, and risk assessment approaches are consistent with the requirements of EPA's
children's environmental health policy ('https://www.epa.gov/children/epas-policv-evaluating-risk-children').
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Although a developmental study in non-rodents is a conventional requirement to register
pesticides with food-uses, the HASPOC determined the study was unlikely to have an impact on
the risk assessment and thus recommended waiving the requirement for paraquat (TXR 0056294,
K. Rury, 04/12/2012). The general literature review and PD systematic review confirmed that
the toxicology database reported the most sensitive endpoints for risk assessment. Furthermore,
the PD systematic review was used to characterize neurotoxic outcomes resulting from paraquat
exposure that were not addressed in the database.
4.4.2 Evidence of Neurotoxicity
Recent studies from the open literature demonstrated accumulation of paraquat in brain tissue
following oral exposure, yet guideline, non-guideline, and open literature studies present little
evidence to suggest the nervous system is a primary target tissue. Clinical signs of toxicity
(hunched posture and piloerection) noted in the guideline acute neurotoxicity study (ACN) and
rodent developmental studies were determined to be an agonal response to the bolus dose
administered via gavage and were not considered evidence of treatment induced neurotoxicity.
This is supported by the lack of neuropathology or motor activity findings following acute
exposure. Likewise, no behavioral changes including motor activity or abnormal
neuropathology findings were noted during and at the end of a 90-day dietary exposure in the
subchronic neurotoxicity study (SCN). In addition to the guideline studies, several non-guideline
studies were submitted to the Agency that investigated neurotoxic outcomes specific to
Parkinsonism (MRID 49122301-04). Although there is little evidence of PD-like symptoms in
the non-guideline studies, deficiencies related to the exposure design limit their usefulness for
characterizing paraquat neurotoxicity from pesticidal uses. The connection between paraquat
exposure and PD was further explored in the PD and epidemiology systematic reviews. The two
systematic reviews concluded that the weight of evidence was insufficient to link paraquat
exposure from pesticidal use of US registered products to PD in humans.
Across the guideline, non-guideline, and open literature studies, it is apparent that neurotoxicity
is not a common response in exposure scenarios that are anticipated to result from pesticidal use
of paraquat. The few studies that reported PD-like effects in animal models observed those
neurotoxic effects at doses at least 14 times above the current subchronic and chronic PODs,
indicating that the respiratory effects are a more sensitive endpoint and the risk assessment
accounts for and is protective of the limited evidence of neurotoxicity.
4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal
No evidence of increased quantitative or qualitative susceptibility was seen in rat developmental
toxicity and reproduction studies. All fetal and offspring effects were observed in the presence
of comparable maternal toxicity. An acceptable rabbit developmental study was not available;
however, the HASPOC determined the study was unlikely to have an impact on the risk
assessment and thus recommended waiving the requirement for paraquat (TXR 0056294, K.
Rury, 04/12/2012). One study in the open literature (Lou et al. 2016) reported increased
sensitivity to oral exposure to a high purity paraquat product based on age (3 weeks vs. 8 weeks),
which is counter to the lack of age and lifestage susceptibility reported in the toxicity database.
Although this is a unique finding relative to the rest of the toxicity database, the product used
was of higher purity (>98%) than those registered for pesticidal use (<48%), thus the exposure
design and results in the Lou et al. (2016) study are not considered to be representative of the
anticipated exposure scenarios for pesticidal uses of paraquat dichloride. The PODs selected for
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risk assessment account for the developmental and offspring effects observed in the database
from exposure to risk assessment relevant paraquat products (e.g. technical products and lower
purity formulations) and are thus protective.
4.4.4 Residual Uncertainty in the Exposure Database
The dietary risk assessment is conservative and will not underestimate dietary exposure to
paraquat. The non-occupational spray drift exposure assessments are based upon the 2012
Residential Standard Operating Procedures (SOPs) and are unlikely to underestimate risks.
4.5 Toxicology Endpoint and Point of Departure Selections
PODs were selected for dietary (acute and chronic), incidental oral (short-term), dermal (short-
and intermediate-term) and inhalation (short- and intermediate-term) exposure scenarios. The
PODs, uncertainty factors, and calculated reference dose /population adjusted dose or LOCs for
each exposure scenario are detailed below. Toxicity studies used to select PODs for each
exposure scenario are presented in Table 4.5.4.1 and 4.5.4.2. The toxicology database was re-
evaluated during Registration Review to incorporate new toxicity data and to update endpoints
selected for PODs to be consistent with current HED practices. HED recognizes that the toxicity
database contains studies with established endpoints that are considered conservative in light of
current HED practices for determining adversity in toxicity studies (e.g., study endpoints based
on decreased bodyweight gain in the absence of decreases in absolute bodyweight). However, it
was determined that these studies did not impact endpoints for the risk assessment and, therefore,
were not updated for Registration Review.
4.5.1 Dose-Response Assessment
Acute Dietary (All Populations)
The POD for acute dietary exposure for all populations (5 mg paraquat ion/kg) was based on the
lowest dose without an acute effect in the developmental rat study (MRID 00113714). At 10 mg
paraquat ion/kg, mortality was observed following progressive deterioration of health in three
animals. Clinical signs of toxicity (staining of neck and subdued nature) were noted in these
animals within 2-3 days of the first dose and evolved to more severe signs of distress (thin,
hunched, piloerection, staining around nose, forepaws and eyes) prior to death 5-7 days after the
initial exposure. Given evidence in other acute oral studies and human incidents reports of
delayed symptoms and lethality from acute exposure, the clinical signs and mortalities observed
in these three animals were conservatively assumed to be the result of the initial dose and thus
were considered appropriate for assessing acute dietary exposure. Delayed mortalities also
considered conservative evidence of an acute effect were noted at a lower dose (3.6 mg paraquat
ion/kg) in the Lou et al. (2016) study (MRID 50733301) identified in the open literature screen
(D449107; TXR 0057887, A. Wray, 06/26/2019); however, the paraquat product used in this
study was of much higher purity (> 98%) than the registered products undergoing Registration
Review (< 48%) and thus the results were reflective of an exposure scenario that is not relevant
to the pesticidal uses of paraquat. The previous acute POD (1.25 mg paraquat ion/kg) was based
on alveolar histiocytes noted in the parental population of the multi-generation reproduction
study. It was not retained, however, because this lung effect could not be unequivocally
attributed to a single dose and thus was considered less robust for an acute POD compared to the
clinical signs and mortality in the rat developmental study. Uncertainty factors for interspecies
extrapolation (10X) and intraspecies variation (10X) were applied to the NOAEL to calculate the
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acute reference dose (aRfD = 0.05 mg paraquat ion/kg). The acute population adjusted dose
(aPAD = 0.05 mg paraquat ion/kg/day) is equivalent to the POD divided by all applicable
uncertainty factors, including the FQPA SF (IX).
Chronic Dietary (All Populations)
The POD for chronic dietary exposure for all populations was established based on the lung
effects observed in the subchronic and chronic dog oral toxicity studies (MRIDs 00072416 and
00132474). These two dog studies were considered compatible because the lung effects were
consistent between the two studies and occurred at similar doses despite the difference in
duration. The NOAEL (0.5 mg paraquat ion/kg/day) from the subchronic dog study was selected
as the chronic dietary POD because it was comparable to the chronic study NOAEL (0.45 mg
paraquat ion/kg/day) and was protective of the respiratory effects observed at 0.93-1.5 mg
paraquat ion/kg/day in the dog studies including gross lung lesions, increased severity of chronic
pneumonitis, and increased lung weights. The critical effects in these studies were appropriate
endpoints for the chronic dietary risk assessment because they were consistent with the known
targets of paraquat exposure and were the most sensitive endpoints observed in the paraquat
toxicity database for repeated oral exposures. The current chronic dietary POD is consistent with
the POD previously selected for chronic dietary assessments (0.45 mg paraquat ion/kg/day) that
was based on the respiratory effects in the chronic dog oral toxicity study. Uncertainty factors for
interspecies extrapolation (10X) and intraspecies variation (10X) were applied to the NOAEL to
calculate the chronic reference dose (cRfD = 0.005 mg paraquat ion/kg/day). The chronic
population adjusted dose (cPAD = 0.005 mg paraquat ion/kg/day) is equivalent to the POD
divided by all applicable uncertainty factors, including the FQPA SF (IX).
Short- and Intermediate-Term Incidental/Adult Oral
The co-critical dog studies were also used to establish the short-term adult/incidental oral POD
(0.5 mg paraquat ion/kg/day). The co-critical dog studies are appropriate for assessing short-
term oral exposure because the lung effects observed in this study are consistent with the known
targets of paraquat toxicity and were observed in a timeframe relevant to the exposure scenario.
Furthermore, these were the most sensitive endpoints for oral exposure and are thus protective of
all toxicity reported in the paraquat toxicity database. An incidental oral endpoint was not
selected prior to this risk assessment. The LOC for oral exposure is 100 based on a combination
of uncertainty factors for interspecies extrapolation (10X), intraspecies variation (10X), and
FQPA SF (IX).
Short- and Intermediate-Term Dermal
The systemic NOAEL (6 mg paraquat ion/kg/day) from the route specific 21-day dermal study in
rabbits (MRID 00156313) was selected to be the POD for the occupational dermal assessment
and spray drift assessment. Six mg paraquat ion/kg/day was the highest dose tested (HDT) in the
21-day dermal study and there are no additional studies in the toxicity database that investigate
systemic or dermal toxicity from repeat exposure at higher dermal doses. The 21-day study did
not test higher due to animal welfare concerns based on the slight to severe skin damage
observed at relatively low topical doses (2.6 - 6 mg paraquat ion/kg/day). Reports of skin
damage were also noted in human incidents that involved dermal exposure to concentrated or
dilute solutions of paraquat. 28 The severity of dermal toxicity in the incident report ranged from
28 These incidents from 2016 cases show typical paraquat exposures & delayed onset of dermal symptoms:
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blisters and dry skin to complete corrosion requiring skin grafts. Although the toxicity database
indicates paraquat is not well absorbed across intact human skin, the corrosive properties of the
chemical, detailed in the dermal study and human incident reports, affect the integrity of the skin.
Further corrosion of the dermal layer is anticipated at doses above the HDT in the subchronic
dermal study, which increases the likelihood of systemic toxicity as the barrier separating
dermally applied paraquat from the bloodstream erodes. Consequently, the HDT from the route
specific dermal study was selected to be protective of the potential for systemic toxicity at higher
dermal doses. The rabbit is ostensibly a conservative model for dermal toxicity of paraquat
based on evidence of greater sensitivity to acute dermal exposure compared to rats.
Nevertheless, regulating based on the systemic NOAEL from the dermal study is appropriate
given the lack of data on the mammalian systemic response to repeat dermal dosing above 6 mg
paraquat ion/kg/day and the corrosive properties of the chemical that will impact the ability of
the skin to restrict paraquat absorption at higher dermal doses. The previous dermal POD (1.25
mg paraquat ion/kg/day) was based on the parental endpoint from the multi-generation
reproduction study. Accounting for the low oral absorption (6-14%), the most conservative
estimate for a dermal equivalent dose based on this oral POD and the DAF for intact skin (0.23-
0.3%) is 25 mg paraquat ion/kg/day29. Note that this calculation assumes the skin is intact at the
estimated dermal dose level. The LOC for dermal exposure is 100 based on a combination of
uncertainty factors for interspecies extrapolation (10X) and intraspecies variation (10X), and, for
non-occupational scenarios, theFQPA SF (IX).
Short- and Intermediate-Term Inhalation
The NOAEC (0.01 |ig paraquat ion/L/day) from the route specific inhalation study (MRID
00113718) was selected to be the POD for the occupational and residential inhalation
assessments. The NOAEC was based on an increased incidence of squamous keratinizing
metaplasia and hyperplasia of the epithelium of the larynx observed in animals exposed to 0.1 |ig
paraquat ion/L/day (LOAEC). The route-specific study was appropriate for assessing inhalation
risk because the duration and route of administration used in the study were similar to the
anticipated inhalation exposure scenarios and life-stage susceptibility was not a concern for
inhalation exposure. Previously, the inhalation PODs were selected for respirable and non-
respirable particles. The respirable particle POD was the same as the inhalation POD selected
currently for Registration Review and the non-respirable particle POD (1.25 mg paraquat
ion/kg/day) was based on lung effects observed in the multi-generation reproduction study. For
Registration Review, the respirable particle POD was used to assess risk for all inhalation
scenarios. A non-respirable particle POD was not selected. Particle size data reported in the
study were not sufficient to calculate a human equivalent dose for risk assessment; therefore, an
animal equivalent dose (AED) was calculated (see footnote of Table 4.5.4.1 and 4.5.4.2). The
One case was a certified applicator was loading paraquat into a tank and he accidentally splashed some product which
got inside of the chemical resistant gloves he wore. He decontaminated immediately but he developed a burning
sensation about 30 minutes later.
A farmworker sprayed weeds all morning with a backpack sprayer; he wore a waterproof coverall, required mask,
gloves and eye protection. He was sweating in the heat and his skin began to burn. The protective overall had broken
and paraquat had gotten onto his skin. He went home and decontaminated. His symptoms worsened over time and he
went to the emergency room for pain and symptoms several days after the application.
A 16-vear old summer farm employee was told to apply paraquat on his employer's farm when the hose broke and
sprayed his pants. He was unaware of danger (under supervision of certified applicator who was not on site that
day). The cases continued working and did not become symptomatic with dermal irritation and burning until that
evening.
29 Dermal equivalent dose = (oral POD * oral absorption)/DAF = (1.25 mg paraquat ion/kg/day * 0.06)/0.003 = 25 mg paraquat
ion/kg/day
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AED for the occupational and non-occupational inhalation scenarios is 0.0026 mg paraquat
ion/kg/day. The LOC for inhalation exposure is 100 based on a combination of uncertainty
factors for interspecies extrapolation (10X) and intraspecies variation (10X), and, for non-
occupational scenarios, the FQPA SF (IX).
4.5.2 Recommendations for Combining Routes of Exposure for Risk Assessment
For all durations, incidental/adult oral and dermal exposures can be combined. Although the
dermal assessment is based on the lack of systemic effects from dermal exposure, given the lung
is a target organ, it is possible that higher dermal doses would elicit lung toxicity similar to the
response observed in the co-critical dog studies that was used to assess incidental/adult oral
exposure. The respiratory effects in the route specific inhalation study were observed in a
different region of the respiratory tract and thus cannot be combined with the oral and dermal
exposures.
4.5.3 Cancer Classification and Risk Assessment Recommendation
Paraquat is currently classified as Category E (evidence of non-carcinogenicity for humans).
The carcinogenic potential of paraquat was evaluated by the Toxicology Branch Peer Review
Committee (now Carcinogenicity Assessment Review Committee (CARC)) in 1986, 1988, and
1989, and by the Scientific Advisory Panel (SAP) in 1989 (TXR 0007828). In 1986, the
Toxicology Branch Peer Review Committee classified paraquat as a Category C carcinogen
(limited evidence of carcinogenicity in animals), based on an apparent increase in erroneously
combined squamous cell carcinomas in different locations in the head region. In 1988, the
Toxicology Branch Peer Review Committee re-evaluated the tumors observed in rats and
reclassified paraquat as Category E (evidence of non-carcinogenicity in humans). In February of
1989 the SAP classified paraquat as Category D (equivocal evidence of carcinogenicity) based
on squamous cell carcinoma in the nasal cavity of 2 high-dose rats. However, the SAP also
commented that endpoints other than carcinogenicity were more relevant for the regulation of
paraquat. The following month (March 1989) the Toxicology Branch Peer Review Committee
reviewed the carcinogenicity of paraquat, again in light of the SAP conclusions, and determined
its previous classification, Category E, was still appropriate based on the available data.
Paraquat was found to induce sister chromatid exchange in Chinese hamster lung fibroblasts and
increase the number of aberrant cells at cytotoxic concentrations in human peripheral blood
lymphocytes in the presence and absence of metabolic activation. Conversely, paraquat was not
mutagenic in the Salmonella typhimurium assay, not genotoxic in the unscheduled DNA
synthesis assay in vivo or in vitro, negative for chromosomal aberration in the bone marrow test,
and no evidence was found for suppressed fertility or dominant lethal mutagenicity in mice.
Based on these considerations there is no concern for mutagenicity.
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4.5.4 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk
Assessment
Table 4.5.4.1. Sun
Non-Occupationa
nmary of Toxicological Doses and Endpoints for Paraquat for Use in Dietary and
Human Health Risk Assessments
Exposure/
Scenario
POD
U nccrtaintv/FQPA
Safety Factors
RfD, PAD, Level
of Concern for
Risk Assessment
Study and Toxicological
Effects
Acute Dietary (All
Populations)
Acute NOAEL =
5 mg paraquat
ion/kg
UFa = 10X
UFh = 10X
FQPA SF = IX
Acute RfD = 0.05
mg paraquat
ion/kg
aPAD = 0.05 mg
paraquat ion/kg
Developmental- rat
MRID 00113714
Acute LOAEL= 10 mg paraquat
ion/kg, based on clinical signs of
toxicity and mortality
Chronic Dietary
(All Populations)
NOAEL = 0.5 mg
paraquat
ion/kg/day
UFa = 10X
UFh = 10X
FQPA SF = IX
Chronic RfD =
0.005 mg
paraquat
ion/kg/day
cPAD = 0.005 mg
paraquat
ion/kg/day
Co-critical Dog Oral Studies
Subchronic MRID 00072416
LOAEL = 1.5 mg paraquat
ion/kg/day based on increased
lung weight and incidence of
alveolitis in both sexes.
Chronic MRID 00132474
LOAEL = 0.93 mg paraquat
ion/kg/day, based on increased
severity of chronic pneumonitis
and gross lung lesions in both
sexes, and focal pulmonary
granulomas in males
Incidental
Oral/Adult Oral
Short-Term (1-30
days)
NOAEL = 0.5 mg
paraquat
ion/kg/day
UFa = 10X
UFh = 10X
FQPA SF = IX
Non-Occupational
LOC for MOE =
100
Co-critical Dog Oral Studies
Subchronic MRID 00072416
LOAEL = 1.5 mg paraquat
ion/kg/day based on increased
lung weight and incidence of
alveolitis in both sexes.
Chronic MRID 00132474
LOAEL = 0.93 mg paraquat
ion/kg/day, based on increased
severity of chronic pneumonitis
and gross lung lesions in both
sexes, and focal pulmonary
granulomas in males
Dermal Short-
Term (1-30 days)
NOAEL = 6 mg
paraquat
ion/kg/day
UFa = 10X
UFh = 10X
FQPA SF = IX
Non-Occupational
LOC for MOE =
100
21-day Dermal toxicity study -
rabbits
MRID 00156313
NOAEL = 6 mg paraquat
ion/kg/day (HDT)
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Table 4.5.4.1. Sur
Non-Occupationa
nmary of Toxicological Doses and Endpoints for Paraquat for Use in Dietary and
Human Health Risk Assessments
Exposure/
Secnario
POD
U nccrtainty/FQPA
Safety Factors
RfD, PAD, Level
of Concern for
Risk Assessment
Study and Toxicological
Effects
Inhalation Short-
Term (1-30 days)
NOAEC = 0.01
|ig paraquat
ion/L/day
AED = 0.0026 mg
paraquat
ion/kg/day
UFa = 10X
UFh = 10X
FQPA SF = IX
Non-Occupational
LOC for MOE =
100
21-Day inhalation toxicity study
- rat
MRID 00113718
LOAEL = 0.10 (ig paraquat
ion/L/day, based on squamous
keratinizing metaplasia and
hyperplasia of the epithelium of
the larynx
Cancer (oral,
dermal, inhalation)
Classification: Category E (evidence of non-carcinogenicity for humans) (TXR 0007828)
Point of departure (POD) = A data point or an estimated point that is derived from observed dose-response data and used to mark
the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures. NOAEL =
no-observed adverse-effect level. LOAEL = lowest-observed adverse-effect level. UF = uncertainty factor. UFa = extrapolation
from animal to human (interspecies). UFh = potential variation in sensitivity among members of the human population
(intraspecies). UFl = use of a LOAEL to extrapolate a NOAEL. UFs = use of a short-term study for long-term risk assessment.
UFdb = to account for the absence of key data (i.e., lack of a critical study). FQPA SF = FQPA Safety Factor. PAD =
population-adjusted dose (a = acute, c = chronic). RiD = reference dose. MOE = margin of exposure. LOC = level of concern.
N/A = not applicable. HDT = Highest dose tested. AED = Animal Equivalent Dose (mg/kg/day) = duration adjusted POD
(mg/L) * animal specific conversion factor (44 L/hr-kg BW) * animal daily duration (hr).
Table 4.5.4.2. Summary of Toxicological Doses and Endpoints for Paraquat for Use in Occupational
Human Health Risk Assessments
Exposure/
Scenario
POD
Uncertainty Factors
Level of
Concern for
Risk
Assessment
Study and Toxicological
Effects
Dermal Short- and
Intermediate-Term
(1 day to 6
months)
NOAEL = 6 mg
paraquat ion/kg/day
UFa = 10X
UFh = 10X
Occupational
LOC for MOE
= 100
21-day Dermal toxicity study
- rabbits
MRID 00156313
NOAEL = 6 mg paraquat
ion/kg/day (HDT)
Inhalation Short-
and Intermediate-
Term (1 day to 6
months)
NOAEC = 0.01
|ig paraquat ion/L/day
AED = 0.0026 mg
paraquat ion/kg/day
UFa = 10X
UFh = 10X
Occupational
LOC for MOE
= 100
21-Day inhalation toxicity
study in rats
MRID 00113718
LOAEL = 0.10 |ig paraquat
ion/L/day, based on
squamous keratinizing
metaplasia and hyperplasia
of the epithelium of the
larynx
Cancer (oral,
dermal, inhalation)
Classification: Category E (evidence of non-carcinogenicity for humans) (TXR 0007828)
Point of departure (POD) = A data point or an estimated point that is derived from observed dose-response data and used to mark
the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures. NOAEL =
no-observed adverse-effect level. LOAEL = lowest-observed adverse-effect level. UF = uncertainty factor. UFa = extrapolation
from animal to human (interspecies). UFh = potential variation in sensitivity among members of the human population
(intraspecies). UFl = use of a LOAEL to extrapolate a NOAEL. UFs = use of a short-term study for long-term risk assessment.
UFdb = to account for the absence of key data (i.e., lack of a critical study). MOE = margin of exposure. LOC = level of
concern. N/A = not applicable. HDT = Highest dose tested. AED = Animal Equivalent Dose (mg/kg/day) = duration adjusted
POD (mg/L) * animal specific conversion factor (44 L/hr-kg BW) * animal daily duration (hr).
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4.6 Endocrine Disruption
As required by FIFRA and the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA reviews
numerous studies to assess potential adverse outcomes from exposure to chemicals.
Collectively, these studies include acute, subchronic and chronic toxicity, including assessments
of carcinogenicity, neurotoxicity, developmental, reproductive, and general or systemic toxicity.
These studies include endpoints which may be susceptible to endocrine influence, including
effects on endocrine target organ histopathology, organ weights, estrus cyclicity, sexual
maturation, fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For
ecological hazard assessments, EPA evaluates acute tests and chronic studies that assess growth,
developmental and reproductive effects in different taxonomic groups. As part of its most recent
registration decision for paraquat, EPA reviewed these data and selected the most sensitive
endpoints for relevant risk assessment scenarios from the existing hazard database. However, as
required by FFDCA section 408(p), paraquat is subject to the endocrine screening part of the
Endocrine Disruptor Screening Program (EDSP).
EPA has developed the EDSP to determine whether certain substances (including pesticide
active and other ingredients) may have an effect in humans or wildlife similar to an effect
produced by a "naturally occurring estrogen, or other such endocrine effects as the Administrator
may designate." The EDSP employs a two-tiered approach to making the statutorily required
determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a
chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal
systems. Chemicals that go through Tier 1 screening and are found to have the potential to
interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA
will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2
testing is designed to identify any adverse endocrine-related effects caused by the substance and
establish a dose-response relationship between the dose and the E, A, or T effect.
Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between
October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67
chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list
of chemicals identified for EDSP screening was published on June 14, 201330 and includes some
pesticides scheduled for Registration Review and chemicals found in water. Neither of these
lists should be construed as a list of known or likely endocrine disruptors.
For further information on the status of the EDSP, the policies and procedures, the lists of
chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our
website.31
5.0 Dietary Exposure and Risk Assessment
5.1 Residues of Concern Summary and Rationale
The qualitative nature of residues in plant commodities is understood based upon studies
depicting the metabolism of paraquat in carrots and lettuce following preemergence treatment
and in potatoes and soybeans following desiccant treatment. The residue of concern in plants is
30 See https://www.regulations.gov/document?D=EPA-HO-OPPT-2009-0477-0Q74 for the final second list of chemicals.
31 https: //www.epa. go v/endocrine-disruption
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the parent paraquat. The qualitative nature of residues in livestock is adequately understood
based on the combined results of studies conducted with ruminants (goats and cows), swine, and
poultry. The residue of concern in eggs, milk, and poultry and livestock tissues is also parent
paraquat.
Table 5.1. Summary of Metabolites and Degradates to be Included in the Risk Assessment and
Tolerance Expression
Matrix
Residues included in
Risk Assessment
Residues included in Tolerance
Expression
Plants
Primary Crop
Parent Paraquat
Parent Paraquat
Rotational Crop
Parent Paraquat
Parent Paraquat
Livestock
Ruminant
Parent Paraquat
Parent Paraquat
Poultry
Parent Paraquat
Parent Paraquat
Drinking Water
Parent Paraquat
N/A
5.2 Summary of Plant and Animal Metabolism Studies
In plant metabolism studies reflecting preemergence treatment, the total radioactive residues
were 0.0048 ppm in carrot root and 0.0034 ppm in lettuce leaf samples following a single
preemergence application of [14C] paraquat at rates of 13.1 lb ai/A for carrots and 12.8 lb ai/A
for lettuce (~13x the maximum rate of 1 lb ai/A for each crop). These data suggest that
radioactive residues of paraquat are not readily taken up from the soil in significant quantities by
these crop commodities following this mode of treatment. No further residue characterization
and identification was conducted on these samples because of the low magnitude of radioactivity
obtained. In plant metabolism studies reflecting desiccant treatment, the total radioactive
residues were 0.075 and 0.087 ppm in potatoes, 0.652 and 0.841 ppm in soybeans, and 506.3 and
768.5 ppm in soybean foliage following a single foliar desiccant application of uniformly
ring-labeled [14C] paraquat at 7.8 or 7.9 lb ai/A for potatoes and 7.3 lb ai/A for soybeans (~6x the
maximum seasonal rate of 1.25 lb ai/A for potatoes and 29x the maximum single application rate
of 0.25 lb ai/A for soybeans). Paraquat cation was the major 14C-residue identified and
accounted for -91% of the total radioactivity in potatoes, -84% of the total radioactivity in
soybeans, and virtually all of the total radioactivity in soybean foliage. Other minor metabolites
found in soybean foliage were QINA (quaternary iso-nicotinic acid, a photodegradant) and
monoquat (l-methyl-4,4'-bipyridinium ion), each at 0.3% of TRR.
In a ruminant metabolism study, a lactating goat was dosed with ring-labeled [14C] paraquat at
103 ppm in the diet for seven days. The total radioactive residue, expressed as ppm paraquat,
was 0.02-0.03 ppm in fat (peritoneal and subcutaneous), 0.08-0.12 ppm in muscles (fore- and
hind-quarter), 0.56 ppm in liver, and 0.74 ppm in kidney. The maximum total radioactivity in
milk increased daily to a maximum of 0.0092 ppm paraquat ion equivalents four hours before
slaughter; 15.1% of the TRR of this sample was found to be paraquat. In edible tissues, paraquat
accounted for the majority of the identified residues including -49-120%) of TRR in fat, -90-
100% of TRR in muscles, -48% of TRR in liver, and -95% of TRR in kidney. Other
metabolites that were identified in tissues were the monopyridone of paraquat (l,2-dihydro-l,l'-
dimethyl-4,4'-bipyridinium ion) which accounted for 3.2% of TRR in liver and monoquat which
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accounted for 3.4% of TRR in liver and 6.5% of TRR in peritoneal fat. A pig metabolism study
reflecting use of ring-labeled [14C] paraquat and a feeding level of 2.44 ppm is also available.
Total radioactive residues were 0.20 ppm paraquat equivalents in liver, 0.38 ppm in kidney, 0.05
ppm in muscle, and 0.01 ppm in fat. Paraquat was found to comprise -70% of TRR in liver,
101% of TRR in kidney, 95% of TRR in muscle, and 106% of TRR in fat. Liver tissue, the only
tissue analyzed for residues other than paraquat, was found to contain monoquat at -4% of TRR.
In a poultry metabolism study, laying hens were dosed with ring-labeled [14C] paraquat at 30
ppm in the diet for ten consecutive days. Radioactive residues were found in all examined
tissues (including liver, abdominal and subcutaneous fat, and leg and breast muscle). Paraquat
was the major residue (-80-98% of TRR) identified in all poultry tissues; monoquat was a minor
metabolite (-4% of TRR each) in liver and kidney. The total radioactive residues in the yolks
and albumen of the eggs increased irregularly from nondetectable (<0.01 ppm paraquat ion
equivalents) on the first two days of the study to a maximum of 0.1812 ppm in the yolk and
0.0014 ppm in the albumen on the eighth day. Virtually all the radioactivity in the yolk was
identified as paraquat; no analysis of albumen was reported.
5.3 Summary of Environmental Degradation
Paraquat undergoes minimal degradation in the environment, and thus is very persistent (as
parent). However, it's very high propensity to bind to solids, particularly clay, makes it very
immobile. In addition, paraquat does not readily appear to desorb from clay. The greatest cause
for concern is likely to be erosion of contaminated sediments off-site and subsequent re-
deposition onto non-target areas (especially surface water bodies). There is an additional (minor)
concern for the one use (wheat) that includes aerial spray; however, this use entails very small
amounts (relative to all other uses), so spray drift onto nearby surface water drinking water
sources should be fairly limited. Because of its very low mobility and strong tendency to bind
tightly to soils, paraquat contamination of drinking water supplies derived from groundwater is
expected to be highly unlikely. In addition, the strong binding characteristics of paraquat are
likely to render most residues in raw drinking water sources removable through sedimentation
processes, which are typically included as part of standard drinking water treatments.
5.4 Comparison of Metabolic Pathways
Paraquat is very stable. In both primary crops and rotational crops, parent paraquat was the only
major residue. In goats, pigs, and poultry, paraquat was again the only residue of concern.
Paraquat was not metabolized by rats. It was poorly absorbed after oral administration to rats,
dogs and mice. Once absorbed, paraquat was rapidly distributed to most tissues but especially to
lungs and kidneys. Tissues other than lungs did not retain paraquat. In the environment,
paraquat is very persistent and undergoes minimal degradation. As a result of the findings of the
plant and animal metabolism studies as well as the environmental degradation studies, parent
paraquat is the only residue of concern considered in this human health risk assessment.
5.5 Food Residue Profile
Adequate field trial data, following treatments according to the maximum registered use patterns,
have been submitted for all registered crops, and adequate feeding studies have been submitted
to support tolerances for residues in livestock commodities. No additional data are required.
Residues in plants are generally low. For example, many crops show residues which were below
the limit of quantification (LOQ; 0.05 ppm). Processing studies indicate that paraquat residues
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do not concentrate except in sugar cane molasses and pineapple processed residue. Feeding
studies with cattle and hens indicate that livestock commodity residues resulting from
consumption of potentially treated feed items will be generally
-------
5.7.2 Percent Crop Treated Used in Dietary Assessment
BEAD's Usage and Label Use Team (ULUT) provided a screening-level usage analysis (SLUA)
for paraquat (9/19/2016). The acute assessment assumed 100 % crop treated. For the chronic
analysis, the following average percent crop treated values were used: almond (25%), apple
(25%), apricot (10%), artichoke (25%), asparagus (10%), avocado (1%), barley (2.5%), green
beans (2.5%), blueberries (15%), broccoli (2.5%), cabbage (2.5%), caneberries (50%),
cantaloupe (5%), carrots (2.5%), cauliflower (1%), celery (2.5%), cherry (20%), corn (2.5%),
cotton (20%>), cucumber (5%), dry beans/peas (5%), figs (20%), garlic (1%), grapefruit (5%),
grapes (20%), hazelnut (50%), kiwifruit (25%), lemon (2.5%), lettuce (2.5%), nectarine (15%),
olive (5%>), onion (5%), orange (10%), peach (25%), peanut (30%), pear (10%), green peas (1%),
pecan (5%), peppers (5%), pistachio (25%), plum/prune (10%), pomegranate (15%), potato
(5%>), pumpkin (5%), rice (1%), soybean (2.5%), spinach (2.5%), squash (5%), strawberry (5%),
sugar beet (1%), sugarcane (5%), sunflower (2.5%), sweet corn (1%), tangelo (10%), tangerine
(5%>), tomato (10%), walnut (15%), watermelon (5%), and wheat (1%).
5.7.3 Acute Dietary Risk Assessment
The general U.S. population and all population subgroups have risk estimates that are below
HED's level of concern (i.e., 100% of the aPAD). The most highly exposed population
subgroup is Children 1-2 yrs old which utilizes 38% of the aPAD. The general U.S. population
utilizes 20% of the aPAD.
Table 5.7.3. Results of Acute Dietary Exposure Analysis for Paraquat (Food and Drinking Water)
Population Subgroup
aPAD
95th Percentile
(mkd)*
Exposure (mkd)
% aPAD
General U.S. Population
0.009760
20
All Infants (< 1 year old)
0.013165
26
Children 1-2 years old
0.019239
38
Children 3-5 years old
0.017447
35
Children 6-12 years old
0.05
0.012849
26
Youth 13-19 years old
0.007915
16
Adults 20-49 years old
0.006213
12
Adults 50+ years old
0.005243
10
Females 13-49 years old
0.006024
12
*mkd: milligram per kilogram per day
5.7.4 Chronic Dietary Risk Assessment
The general U.S. population and all population subgroups have risk estimates that are below
HED's level of concern (i.e., 100% of the cPAD). The most highly exposed population
subgroup is Children 1-2 yrs old which utilizes 25% of the cPAD. The general U.S. population
utilizes 6.6% of the cPAD.
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Table 5.7.4. Results of Chronic Dietary Exposure Analysis for Paraquat (Food and Drinking
Water)
Population Subgroup
cPAD
(mkd)*
Exposure (mkd)
% cPAD
General U.S. Population
0.000329
6.6
All Infants (< 1 year old)
0.000850
17
Children 1-2 years old
0.001250
25
Children 3-5 years old
0.000841
17
Children 6-12 years old
0.005
0.000494
9.9
Youth 13-19 years old
0.000264
5.3
Adults 20-49 years old
0.000244
4.9
Adults 50+ years old
0.000236
4.7
Females 13-49 years old
0.000229
4.6
*mkd: milligram per kilogram per day
5.7.5 Cancer Dietary Risk Assessment
An assessment of cancer risk was not performed because paraquat was classified as being a
Category E chemical (evidence of non-carcinogenicity in humans).
6.0 Residential (Non-Occupational) Exposure/Risk Characterization
Paraquat is a restricted use pesticide (RUP); therefore, there are no paraquat products registered
for homeowner use and no products registered for application to residential areas.
7.0 Aggregate Exposure/Risk Characterization
In accordance with the FQPA, HED must consider and aggregate (add) pesticide exposures and
risks from three major sources: food, drinking water, and residential exposures. In an aggregate
assessment, exposures from relevant sources are added together and compared to quantitative
estimates of hazard (e.g., a NOAEL or PAD), or the risks themselves can be aggregated. When
aggregating exposures and risks from various sources, HED considers both the route and
duration of exposure.
There are no residential uses of paraquat; therefore, the only relevant aggregate risk assessments
include acute and chronic exposure to residues in food and drinking water. The aggregate risk
estimates are equivalent to the acute and chronic dietary (food and water) exposure assessments.
8.0 Non-Occupational Spray Drift Exposure and Risk Estimates
W. Britton. Paraquat Dichloride: Occupational and Residential Registration Review Exposure and Risk
Assessment. D448252. 06/26/2019.
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Off-target movement of pesticides can occur via many types of pathways and it is governed by a
variety of factors. Sprays that are released and do not deposit in the application area end up off-
target and can lead to exposures to those it may contact. They can also deposit on surfaces where
contact with residues can eventually lead to indirect exposures (e.g., children playing on lawns
where residues have deposited next to treated fields). The potential risk estimates from these
residues can be calculated using drift modeling onto 50 feet wide lawns coupled with methods
employed for residential risk assessments for turf products.
The approach to be used for quantitatively incorporating spray drift into risk assessment is based
on a premise of compliant applications which, by definition, should not result in direct exposures
to individuals because of existing label language and other regulatory requirements intended to
prevent them.32 Direct exposures would include inhalation of the spray plume or being sprayed
directly. Rather, the exposures addressed here are thought to occur indirectly through contact
with impacted areas, such as residential lawns, when compliant applications are conducted.
Given this premise, exposures for children (1 to < 2 years old) and adults who have contact with
turf where residues are assumed to have deposited via spray drift thus resulting in an indirect
exposure are the focus of this analysis analogous to how exposures to turf products are
considered in risk assessment.
To evaluate the drift potential and associated risks, an approach based on drift modeling coupled
with techniques used to evaluate residential uses of pesticides was used. Essentially, a residential
turf assessment based on exposure to deposited residues has been completed to address drift from
the agricultural applications of paraquat. In the spray drift scenario, the deposited residue value
was determined based on the amount of spray drift that may occur at varying distances from the
edge of the treated field using the AgDrift (v2.1.1) model and the Residential Exposure
Assessment Standard Operating Procedures Addenda 1: Consideration of Spray Drift Policy.
Once the deposited residue values were determined, the remainder of the spray drift assessment
was based on the algorithms and input values specified in the recently revised (2012) Standard
Operating Procedures for Residential Risk Assessment (SOPs).
In accordance with 40CFR158, TTR data are required for all occupational (e.g., sod farms, golf
courses, parks, and recreational areas) or residential turf uses that could result in post-application
exposure to turf. For paraquat, chemical-specific TTR data are not available, therefore, the
estimated TTR value is based on a default assumption from the 2012 Residential SOPs that the
transferable residue available for exposure is 1% of the total deposited residue, which is assumed
to be equivalent to the maximum application rate. TTR data are not required since paraquat is
not registered for use on residential turf; however, if submitted, these data could potentially
refine the spray drift risks.
A screening approach was developed based on the use of the AgDrift® model in situations where
specific label guidance that defines application parameters is not available.33 AgDrift® is
appropriate for use only when applications are made by aircraft, airblast orchard sprayers, or
groundboom sprayers. When AgDrift® was developed, a series of screening values (i.e., the Tier
1 option) were incorporated into the model and represent each equipment type and use under
varied conditions. The screening options specifically recommended in this methodology were
selected because they are plausible and represent a reasonable upper bound level of drift for
32 This approach is consistent with the requirements of the EPA's Worker Protection Standard.
33 http://www.agdrift.com/
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common application methods in agriculture. These screening options are consistent with how
spray drift is considered in a number of ecological risk assessments and in the process used to
develop drinking water concentrations used for risk assessment. In all cases, each scenario is to
be evaluated unless it is not plausible based on the anticipated use pattern (e.g., herbicides are
not typically applied to tree canopies) or specific label prohibitions (e.g., aerial applications are
not allowed). In many cases, risks are of concern when the screening level estimates for spray
drift are used as the basis for the analysis. In order to account for this issue and to provide
additional risk management options additional spray drift deposition fractions were also
considered. These drift estimates represent plausible options for pesticide labels.
The spray drift risk estimates are based on an estimated deposited residue concentration resulting
from screening level agricultural application scenarios. Paraquat is used on various agricultural
and non-agricultural crops and can be applied via groundboom and aerial application equipment.
Paraquat is not applied by airblast equipment and, therefore, has not been assessed for this
equipment type. The recommended drift scenario screening level options are listed below:
• Groundboom applications are based on the AgDrift option for high boom height and
using very fine to fine spray type using the 90th percentile results.
• Aerial applications are based on the use of AgDrift Tier 1 aerial option for a fine to
medium spray type and a series of other parameters which will be described in more
detail below (e.g., wind vector assumed to be 10 mph in a downwind direction for entire
application/drift event).34
In addition to the screening level spray drift scenarios described above, additional results are
provided which represent viable drift reduction technologies (DRTs) that represent potential risk
management options. Different spray qualities have been considered as well as the impact of
other application conditions (e.g., boom height, use of a helicopter instead of fixed wing aircraft,
crop canopy conditions). Further, if chemical-specific TTR data were submitted, these data
could be used for refinement of spray drift risk estimates.
Dermal and incidental oral risk estimates are combined for children 1 to < 2 years. Although the
dermal assessment is based on the lack of systemic effects from dermal exposure, given the lung
is a target organ, it is possible that higher dermal doses would elicit lung toxicity similar to the
response observed in the co-critical dog studies that was used to assess incidental oral exposure.
Summary of Residential Post-Application Non-Cancer Exposure and Risk Estimates
Results of the adult and children 1 to < 2 years old non-occupational spray drift risk assessment
for paraquat are presented in Table 8.1.1 and 8.1.2, respectively.
Adult dermal and children 1 to < 2 years old combined dermal and incidental oral risk estimates
from indirect exposure to paraquat result in estimated distances from the field edge ranging from
the field edge (0 feet) to 150 feet to reach the LOC (i.e., an MOE > 100) depending on the
application rate and equipment type combination assessed and assuming screening level droplet
sizes and boom heights. Results indicate that the major spray drift risk concern is from aerial
applications.
34 AgDrift allows for consideration of even finer spray patterns characterized as very fine to fine. However, this spray pattern
was not selected as the common screening basis since it is used less commonly for most agriculture.
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Appropriate drift reduction technologies such as changing the spray type/nozzle configuration to
coarser spray applications may result in less drift and reduced risk concerns (i.e., higher MOEs)
from aerial applications. Similarly, using coarser sprays and lowering boom height for
groundboom sprayers reduces risk concerns.
Tabic 8.1.1 Adult Sprav Drift Assessment for Paraquat
Exposure
Secnarios
Applieation Type
Spray Tvpe/Nozzlc
Configuration
Applieation
Rate
(lb ai/A)
Distance to
Dermal
MOE> 100
Aerial
Fine to Medium
75 feet
Groundboom
High Boom Very Fine
to Fine
1.5
10 feet
Aerial
Fine to Medium
50 feet
Groundboom
High Boom Very Fine
to Fine
1.0
10 feet
Adult
Groundboom
High Boom Very Fine
to Fine
0.94
10 feet
Dermal
Aerial
Fine to Medium
Exposure to
Turf
Groundboom
High Boom Very Fine
to Fine
0.80
Following
Aerial
Fine to Medium
Spray Drift
Groundboom
High Boom Very Fine
to Fine
0.60
Field Edge
Aerial
Fine to Medium
Groundboom
High Boom Very Fine
to Fine
0.50
Aerial
Fine to Medium
Groundboom
High Boom Very Fine
to Fine
0.30
Table 8.1.2 Children 1 to < 2 Years Old Sprav Drift Assessment for Paraquat
Exposure
Seenarios
Application
Type
Spray Type/Nozzle
Configu ration
Application
Rate
(lb ai/A)
Distance to
Dermal
MOE> 100
Distance to
Oral HtM
MOE> 100
Aerial
Fine to Medium
150 feet
10 feet
Groundboom
High Boom Very Fine to
Fine
1.5
50 feet
Aerial
Fine to Medium
100 feet
Groundboom
High Boom Very Fine to
Fine
1.0
25 feet
Children
Groundboom
High Boom Very Fine to
Fine
0.94
25 feet
1 to <2 Years
Aerial
Fine to Medium
75 feet
Old Exposures
to Turf
Groundboom
High Boom Very Fine to
Fine
0.80
10 feet
Field Edge
Following
Aerial
Fine to Medium
50 feet
Spray Drift
Groundboom
High Boom Very Fine to
Fine
0.60
10 feet
Aerial
Fine to Medium
50 feet
Groundboom
High Boom Very Fine to
Fine
0.50
10 feet
Aerial
Fine to Medium
Groundboom
High Boom Very Fine to
Fine
0.30
Field Edge
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9.0 Non-Occupational Bystander Post-Application Inhalation Exposure and Risk
Estimates
Volatilization of pesticides may be a source of post-application inhalation exposure to
individuals nearby pesticide applications. The agency sought expert advice and input on issues
related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act
Scientific Advisory Panel (SAP) in December 2009, and received the SAP's final report on
March 2, 2010 flittps://www.regulations.gov/document?D=EPA-HO-OPP-2009-0687-0037V
The agency has evaluated the SAP report and has developed a Volatilization Screening Tool and
a subsequent Volatilization Screening Analysis (https://www.regulations.gov/docket?D=EPA-
HO-QPP-2014-0219V
HED used this screening analysis to determine if data (i.e., flux studies, route-specific inhalation
toxicological studies) or further analysis were required for paraquat. Air monitoring data are
available from California Air Resources Board (CARB) for paraquat, although the study dates to
1987 and all samples collected were below the minimum detection limit (MDL) of 0.022 |ig/m3.
The following is a summary from the CARB website35 regarding the air monitoring study and
results:
Paraquat (Gramoxone®) is a non-selective herbicide used to control broadleaf weeds and
grasses. It is also used as a pre-harvest defoliant for cotton and hops. The greatest use in
California in 2000 was on cotton (268,477pounds). Paraquat is regulated as a restricted
material.
Ambient air monitoring was conductedfrom August 31 to November 5, 1987, at four sites in
Fresno County. The background sites were located at the ARB air monitoring stations in Fresno
and Bakersfield. Monitoring was scheduled to coincide with expected applications to cotton. All
of the 318 samples analyzed (field blanks included) were below the MDL (0.022 fig/m3 for a 24-
hour sample).
Based on the results of the study which were all below the MDL, no bystander post-application
inhalation exposures would be expected from volatilization following applications of paraquat to
cotton in CA.
It should be noted these ambient air monitoring data have several uncertainties; the older study
may not be reflective of current agricultural practices and is limited to a single geographic area
and crop. Additional air monitoring studies would be necessary to make a more definitive risk
finding relating to paraquat volatilization exposures. HED will continue to monitor for data to
determine if further analysis is required for paraquat during Registration Review.
10.0 Cumulative Exposure/Risk Characterization
Unlike other pesticides for which EPA has followed a cumulative risk approach based on a
common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as
to paraquat and any other substances and paraquat does not appear to produce a toxic metabolite
produced by other substances. For the purposes of this action, therefore, EPA has not assumed
that paraquat has a common mechanism of toxicity with other substances. In 2016, EPA's Office
35 https://www.cdpr.ca.gov/docs/emon/pubs/ehapreps/EHQ201.pdf
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of Pesticide Programs released a guidance document entitled, Pesticide Cumulative Risk
Assessment: Framework for Screening Analysis rhttps://www.epa.gov/pesticide-science-and-
assessing-pesticide-risks/pesticide-cumulative-risk-assessment-frameworkl. This document
provides guidance on how to screen groups of pesticides for cumulative evaluation using a two-
step approach beginning with the evaluation of available toxicological information and if
necessary, followed by a risk-based screening approach. This framework supplements the
existing guidance documents for establishing common mechanism groups (CMGs)36 and
conducting cumulative risk assessments (CRA)37 During Registration Review, the Agency will
utilize this framework to determine if the available toxicological data for paraquat suggests a
candidate CMG may be established with other pesticides. If a CMG is established, a screening-
level toxicology and exposure analysis may be conducted to provide an initial screen for multiple
pesticide exposure.
11.0 Occupational Exposure/Risk Characterization
W. Britton. Paraquat Dichloride: Occupational and Residential Registration Review Exposure and Risk
Assessment. D448252. 06/26/2019
11.1 Occupational Handler Exposure/Risk Estimates
HED uses the term handlers to describe those individuals who are involved in the pesticide
application process. HED believes that there are distinct job functions or tasks related to
applications and exposures can vary depending on the specifics of each task. Job requirements
(amount of chemical used in each application), the kinds of equipment used, the target being
treated, and the level of protection used by a handler can cause exposure levels to differ in a
manner specific to each application event.
Based on the anticipated use patterns and current labeling, types of equipment and techniques
that can potentially be used, occupational handler exposure is expected from the registered uses
of paraquat. The quantitative exposure/risk assessment developed for occupational handlers is
based on the exposure scenarios presented in Appendix D, Table D.l.
Occupational Handler Exposure Data and Assumptions
A series of assumptions and exposure factors served as the basis for completing the occupational
handler risk assessments. Each assumption and factor is detailed below on an individual basis.
Application Rate: A summary of the maximum application rates used for the occupational
handler risk assessment are presented in the Line by Line, and Maximum Use Scenario PLUS
Reports as generated by BEAD. Also, the maximum application rates are presented in the
summary of occupational handler exposures and risks provided in Appendix D, Table D.l.
Unit Exposures: It is the policy of HED to use the best available data to assess handler exposure.
Sources of generic handler data, used as surrogate data in the absence of chemical-specific data,
include PHED 1.1, the AHETF database, the ORETF database, or other registrant-submitted
occupational exposure studies. Some of these data are proprietary (e.g., AHETF data), and
36 Guidance for Identifying Pesticide Chemicals and Other Substances that have a Common Mechanism of Toxicity (USEPA,
1999)
37 Guidance on Cumulative Risk Assessment of Pesticide Chemicals That Have a Common Mechanism of Toxicity (USEPA,
2002)
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subject to the data protection provisions of FIFRA. The standard values recommended for use in
predicting handler exposure that are used in this assessment, known as "unit exposures", are
outlined in the "Occupational Pesticide Handler Unit Exposure Surrogate Reference Table38",
which, along with additional information on HED policy on use of surrogate data, including
descriptions of the various sources, can be found at the Agency website39.
Area Treated or Amount Handled: The area treated/amounts handled are presented in Appendix
D, Table D.l. The assumptions are based on guidance in the Science Advisory Council for
Exposure (ExpoSAC) Policy 9.1.
Exposure Duration: HED classifies exposures from 1 to 30 days as short-term and exposures 30
days to six months as intermediate-term. Exposure duration is determined by many things,
including the exposed population, the use site, the pest pressure triggering the use of the
pesticide, and the cultural practices surrounding that use site. For most agricultural uses, it is
reasonable to believe that occupational handlers will not apply the same chemical every day for
more than a one-month time frame; however, there may be a large agribusiness and/or
commercial applicators who may apply a product over a period of weeks (e.g., completing
multiple applications for multiple clients within a region). Based on the registered uses of
paraquat, short- and intermediate-term exposures are expected. However, the dermal and
inhalation PODs are the same for both durations; therefore, the assessment is applicable to both
short- and intermediate-term exposures.
Personal Protective Equipment: Estimates of dermal and inhalation exposure were calculated
for various levels of PPE. Results are presented starting at the lowest level of PPE consistently
required on all registered labels. Paraquat product labels direct mixers, loaders, and applicators
and other handlers to wear baseline clothing, chemical resistant gloves, and a NIOSH approved
half-mask, PF10 respirator.
Estimates of inhalation exposure and risk for occupational handler exposure assessments
consider the reduction in exposure afforded by respirators. Typically, results are presented for
"baseline," defined as no respirator, and then, because they are the occupational standard in the
pesticide industry, for half-face filtering facepiece or elastomeric respirators, quantified via
application of their corresponding APF of 10 (90% exposure reduction). This format, in some
cases along with risk estimates for engineering controls, provides a variety of options for risk
management decisions.
Occupational Handler Non-Cancer Exposure and Risk Estimate Equations
The algorithms used to estimate non-cancer exposure and dose for occupational handlers can be
found in the supporting paraquat occupational and residential risk assessment.
Combining Exposures/Risk Estimates
Dermal and inhalation exposures have not been combined for paraquat since the effects selected
for these routes of exposure are not the same.
Summary of Occupational Handler Non-Cancer Exposure and Risk Estimates
38 Available: https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handler-exposure-data
39 Available: https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handler-exposure-data
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Inhalation exposures are the risk driver for all paraquat occupational handler exposure scenarios
assessed with the exception of the mixer/loader/applicator exposure scenarios for which dermal
risks are the driver. The summary of occupational handler risks is presented in Appendix D,
Table D. 1. Estimated occupational handler risks for paraquat are as follows:
• Mixer/loaders: assuming the currently registered level of respiratory personal protection,
a NIOSH approved half-mask, APF 10 respirator, inhalation risks are of concern [i.e., the
margins of exposure (MOEs) are < the LOC of 100] for 13 of 26 exposure scenarios.
When considering the risk mitigation decision for these mixer/loader scenarios that
requires enclosed systems, 21 of 26 remain of concern.
• Loader/applicators: assuming the currently registered level of respiratory personal
protection (a NIOSH approved half-mask, APF 10 respirator), the one exposure scenario
assessed results in an inhalation risk estimate of concern.
• Applicators and flaggers: assuming the currently registered level of respiratory personal
protection (a NIOSH approved half-mask, APF 10 respirator for flaggers, and a closed
system for applicators), inhalation risks are of concern for 19 of 26 exposure scenarios
assessed.
• Mixer/loader/applicators: dermal risks are of concern for 6 of the 8 exposure scenarios
assessed at the currently required level of personal protection (baseline clothing and
chemical resistant gloves). Dermal risks of concern remain for all exposure scenarios (6
of the 8) assessed despite the addition of double layer clothing.
The Agency matches quantitative occupational exposure assessment with appropriate
characterization of exposure potential. While HED presents quantitative risk estimates for
human flaggers where appropriate, agricultural aviation has changed dramatically over the past
two decades. According the 2012 National Agricultural Aviation Association (NAAA) survey of
their membership, the use of GPS for swath guidance in agricultural aviation has grown steadily
from the mid 1990's. Over the same time period, the use of human flaggers for aerial pesticide
applications has decreased steadily from -15% in the late 1990's to only 1% in the most recent
(2012) NAAA survey. The Agency will continue to monitor all available information sources to
best assess and characterize the exposure potential for human flaggers in agricultural aerial
applications.
HED has no data to assess exposures to pilots using open cockpits. The only data available is for
exposure to pilots in enclosed cockpits. Therefore, risks to pilots are assessed using the
engineering control (enclosed cockpits) and baseline attire (long-sleeve shirt, long pants, shoes,
and socks); per the Agency's Worker Protection Standard stipulations for engineering controls,
pilots are not required to wear protective gloves for the duration of the application.
11.2 Occupational Handler Biomonitoring Data Evaluation
An occupational handler biomonitoring study is available for paraquat. The study, as
summarized below, was previously reviewed by HED40 and risk estimates were previously
presented using these data. In March 2000, the HED Exposure Science Advisory Committee
(ExpoSAC) reviewed the study and determined it to be acceptable for use in risk assessment.
40 T. Brennan. Review of Paraquat: Worker Exposure During Mixing, Loading, and Application of GRAMOXONE® EXTRA to
Pecans Using Vehicle-Mounted Ground Boom Equipment. MRID 43644202. D278099. 09/26/2001.
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For the purposes of characterizing the risks based on surrogate, passive dosimetry occupational
handler exposure data (AHETF and PHED), the chemical-specific biomonitoring study data have
been used to quantify occupational handler risks estimates from the absorbed doses measured.
An ethics review of the occupational handler biomonitoring study was conducted41, and it was
concluded that, "there is no barrier in law or regulation to EPA relying on the study in its actions
under FIFRA or §408 of FFDCA."
The following summarizes the occupational handler biomonitoring study, MRID 43644202:
Paraquat: Worker Exposure During Mixing, Loading, and Application of GRAMOXONE®
EXTRA to Pecans Using Vehicle-Mounted Ground Boom Equipment.
The biomonitoring study was submitted by the registrant, Zeneca Inc., to support label revisions
related to personal protective equipment requirements for mixers, loaders and applicators.
Paraquat formulated as GRAMOXONE® EXTRA herbicide in water was applied at a maximum
application rate of 0.94 lb ai/A by groundboom spray to pecan orchards in southwestern Georgia
and southeastern Alabama in September 1994. Depending on worker preference, PPE worn in
the study was varied and consisted of gloves, respirator, face shield, goggles, apron, and/or
Tyvek suits.
Urinary excretion of paraquat was measured as the indicator of exposure to workers who mixed,
loaded, and applied the herbicide. A total of 17-combined mixer/loader/applicator monitoring
units were monitored. The following samples were taken for each subject: a complete 24-hour
pre-exposure urine sample, a 24-hour exposure day (Day 0) urine sample, and 24-hour urine
samples on days 3 through 5. Field fortified urine samples and controls were prepared and were
stored with the experimental samples. Storage stability tests showed that paraquat was stable in
urine over the storage period.
Air monitoring was also conducted during mixing and loading and application of paraquat. Each
subject wore two personal air sampling pumps, one for each activity. Per the study report, the
raw data from air monitoring were never analyzed by the authors since the concentrations of
paraquat in urine were so low.
Urinary paraquat was measured by radioimmunoassay procedure described and validated in
volume one of the study (MRID 43644201). It is not clear whether laboratory fortification and
control samples were run concurrently with each set of field samples. The limit of quantitation
(LOQ) was 1.0 ng/ml for a 1 ml sample. The level of detection was 5 ng/ml. Urinary creatinine
was measured by the Jaffe reaction and a Kone Specific Analyzer.
Application of paraquat was conducted on fifteen separate pecan farms using groundboom spray
equipment mounted on open-cab tractors. GRAMOXONE® EXTRA herbicide was mixed with
surfactant and water to produce 13 to 42 gallons/acre spray mixture. Workers either poured the
formulated product directly into the spray tank or measured it into an open calibrated container
before transferring it to the spray tank.
Although the study sponsor requested that the workers comply with label requirements for PPE,
they did not interfere with the individual subject's typical practices. As a result, a wide variety
41 M. Arling. Ethics Review of Paraquat Biomonitoring Study of Handlers Mixing, Loading, and Applying Gramoxone to Pecans
via Groundboom Equipment. 10/29/2018.
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of PPE was employed. For mixing and loading activities, this ranged from 9 workers wearing
only baseline clothing, 4 wearing baseline clothing plus chemical resistant gloves, 3 wearing
baseline clothing plus gloves and face/eye protection, and 1 worker wearing apron in addition to
baseline clothing plus gloves, face/eye protection, and a half face respirator. All 17 applicators
wore baseline attire, and two workers also wore Tyvek suits during application. The time spent
mixing and loading ranged from 14 to 104 minutes, and the total time of exposure from 230 to
660 minutes. All activities relevant to worker exposure were reported and all workers conducted
both mixing/loading and applying activities. The total amount of formulated product handled
ranged from 2.9 to 27.6 gallons dependent on the type of application and field acreage.
Applications were made with typical commercial application equipment, which varied from site
to site.
Absorbed paraquat was estimated from the results of the biomonitoring study using a urine
excretion rate of 59% (over a 7-day period) derived from a paraquat pharmacokinetics study in
monkeys (MRID 00126096). The pharmacokinetics study measured urinary excretion of
paraquat dichloride for 7 days following a single dose injected intramuscularly into the thighs of
adult Rhesus monkeys.
The biomonitoring study results showed that 6 of the 17 urine samples collected contained
detectable paraquat. All 6 samples were taken from Day 0 (day of product application) samples.
Of the 6 workers with detectable paraquat exposure, none wore protective equipment while
handling the formulation. There was no discernable trend between the amount of pesticide
handled and the exposure incurred.
The mean unit dose calculated from the biomonitoring study was 3.6 x 10"6 mg/kg/lb ai. This
value was calculated using the actual body weights of the test subjects.
Estimated Biomonitoring Risks and Characterization
The occupational handler biomonitoring data were used to estimate an internal dose reflective of
exposures associated with mixing/loading and applying paraquat via groundboom spray
equipment. All registered maximum groundboom application rates (0.30 - 1.5 lb ai/A) for
paraquat were used to estimate a range of potential risks. The resulting MOEs for
mixing/loading and applying paraquat via groundboom range from 13 to 97 where the level of
concern is 100 (Table 11.2).
While the biomonitoring data do not result in estimated risks of concern for paraquat, there are
several uncertainties related to its interpretation: 1) The study participants wore a variety of attire
and personal protective clothing not reflective of currently registered labels. 2) The same
participants that conducted mixing/loading activities also performed the product application,
while in the deterministic assessment these activities are assessed separately. 3) The relative
contribution for dermal and inhalation exposures and their relative impact to the measured
urinary outputs is unclear; however, comparison of the estimated biomonitoring risks to
deterministic estimates assuming the highest contribution from dermal exposures is consistent
with monitoring data in available occupational handler exposure databases (i.e., PHED and
AHETF). 4) The selected inhalation endpoint for paraquat is based on portal of entry effects.
These uncertainties are explained in detail below.
All current registered labels require occupational handlers (mixers and loaders) to wear baseline
clothing, chemical resistant gloves, aNIOSH approved half-mask respirator, as well as a
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chemical resistant apron and face shield. Applicators and other handlers (other than mixers and
loaders) must wear baseline clothing, chemical resistant gloves, a NIOSH approved half-mask
respirator, as well as protective eyewear. Sixteen of the 17 biomonitoring study workers
conducting mixing/loading activities wore less PPE than is required by current labeling (all wore
baseline attire at a minimum). For the applicator activities, all 17 workers wore attire and PPE
less than that currently required (12 of the 17 wore less than baseline attire). Therefore, the
resulting biomonitoring data are not reflective of current practice which would likely offer
greater personal protection if worn as directed by product labeling. Interpretation of the
biomonitoring results cannot be attributed to any specific level of attire or PPE; rather, the data
can be interpreted only as less than currently required by product labeling. Protection factors that
allow for scaling exposures to increased levels of personal protection are utilized where
empirical monitoring data are not available. However, given the wide variety of attire and PPE
donned by study participants, scaling the resulting doses to be reflective of additional PPE would
be inappropriate. Further complicating the interpretation of the biomonitoring outcomes as they
relate to the occupational handler deterministic estimates, all 17 occupational handlers monitored
conducted both mixing/loading and application activities. Typical deterministic risk assessments
conducted for occupational handlers, including that completed for paraquat, estimate these
activities individually which limits direct comparison of the findings to the deterministic risk
assessment outputs. Further, the current mitigation measures being enacted for the mixers and
loaders require closed-system packaging for all non-bulk (less than 120 gallons) end use product
containers. Thus, the comparison of the biomonitoring risk estimates to the deterministic
occupational handler estimates must also consider the deterministic risk estimates generated to
reflect the mixing and loading non-bulk engineering control requirement.
The relative contribution of dermal vs inhalation exposures to the biomonitoring workers cannot
be determined. Passive dosimetry monitoring for dermal exposures was not conducted. Further,
while inhalation monitoring was conducted analysis of these samples was not performed since
"exposures to paraquat were so low." Per the study report, "The data (urinary measures) confirm
that the inhalation exposure to paraquat during both mixing, loading and application was
negligible despite the fact that only one worker wore a respirator during mixing and loading and
none during application." The surrogate unit exposure data recommended for use in
deterministic assessment of occupational handler exposures from mixing/loading for and
application activities via groundboom equipment, along with the inhalation monitoring issues
above, support that the dermal route is anticipated to be the major contributor to overall
exposure. Therefore, for purpose of estimating occupational handler risks from the
biomonitoring data, it was assumed that dermal exposures lead to all of the measured exposures.
Evaluation of the biomonitoring data was conducted based on comparison of the measured
urinary excretion of paraquat (corrected using a 59% excretion rate from the above referenced
study in monkeys), to the equivalent internal dose of 0.014 mg/kg/day as the dermal point of
departure after adjusting for absorption (i.e., 6 mg/kg/day dermal point of departure x 0.23%
dermal absorption). This approach allows for dermal risks to be calculated, though the
biomonitoring study did not measure for the portal of entry effects which is the basis of the
inhalation POD selected for paraquat. Occupational handler dermal and inhalation deterministic
risk estimates were presented separately since the endpoints are not the same. Thus, the
biomonitoring estimated risks should be compared to the dermal risks estimated for
mixing/loading activities for liquid formulated products and for groundboom activities.
There is uncertainty associated with the equivalent internal dose approach in that the data sources
being relied upon are from different species. That is, the dermal POD is derived from a 21-day
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dermal toxicity study in rabbits; the DAF is derived from an in vivo study conducted in humans;
and the metabolic study used to back calculate internal dose in the biomonitoring study was
conducted in monkeys. Despite these species differences and the associated uncertainties across
species, these are the best available data.
There is also uncertainty associated with the reverse dosimetry approach to derive an internal
POD to compare the bio-monitored doses for quantification of risk. The use of the DAF applied
to an external dose to estimate the equivalent internal dose may over or under estimate potential
worker exposures but is consistent with the assumption that dermal exposures are the drivers.
Additionally, the use of the chronic dietary POD was also considered for quantitation of risk
estimates with use of the biomonitoring data. However, this approach may underestimate risks.
The chronic dietary POD is based on an external dose administered via gavage. Oral absorption
of paraquat is estimated to be low in mammals thus the external dose and internal dose cannot be
assumed equivalent. It would, therefore, not be appropriate to compare the external dose used to
derive the chronic dietary POD to the unit dose calculated using the urinary measures from the
biomonitoring study because the urinary data reflect the internal, systemic paraquat
concentration in the workers.
Tiihlc 11.2. l-lsliniiilcd OcciiiKilion.il Ihinrilcr Risks with I so of liiomoniiorin^ l);il;i
r.\|NIMIIV
Si'iii;irin
I nil l)nsi-
(m»/k»/ll>
r.(iiii|)iiu-ni
i sid / Nil. or
()l>M-r\ :i 1 i< i n s
Cliilhin^ Si'i'ii;irii>
Miinilinvd
K;ik-(ll>
;ii/;niv)
Aiv;i
Tivuk'd
l);iil\
CllIVS)
l iil;il l);iil\
Dose ;l
(lll»/k»/il;i\ )
MOT.11
Ground
Application
3.60E-06
Open Cab
Tractor / 17
9 reps no PPE worn; 4 reps
gloves worn only when
mixing; 2 reps gloves, face
shield, and apron, 1 rep
respirator, face shield,
goggles, apron, gloves, and
Tyvek for applying; 1 rep
face shield, goggles, apron,
gloves, and Tyvek for
applying
1.5
200
0.0011
13
1.0
200
0.00072
20
80
0.00029
48
0.94
80
0.00027
52
0.80
200
0.00058
24
80
0.00023
61
0.60
80
0.00017
81
0.50
200
0.00036
39
80
0.00014
97
0.30
200
0.00022
65
a. Total Daily Dose (mg/kg/day) = Unit Dose (mg/kg/lb ai) x appl rate (lb ai/A) x acres per day.
b. MOE = Equivalent Internal Dose (mg/kg/day) / Total Daily Dose (mg/kg/day). Where: Equivalent Internal Dose = 0.0014 mg/kg/day. LOC is
anMOE = 100.
11.3 Occupational Post-Application Exposure/Risk Estimates
HED uses the term post-application to describe exposures that occur when individuals are
present in an environment that has been previously treated with a pesticide (also referred to as re-
entry exposure). Such exposures may occur when workers enter previously treated areas to
perform job functions, including activities related to crop production, such as scouting for pests
or harvesting. Post-application exposure levels vary over time and depend on such things as the
type of activity, the nature of the crop or target that was treated, the type of pesticide application,
and the chemical's degradation properties. In addition, the timing of pesticide applications,
relative to harvest activities, can greatly reduce the potential for post-application exposure.
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11.3.1 Occupational Post-Application Dermal Exposure/Risk Estimates
HED collaborated with BEAD for the evaluation of the potential for, and types of, occupational
post-application exposures from paraquat usage.42 Based on input from BEAD it was
determined that the likelihood of paraquat occupational post-applications exposures is dependent
on whether applications are "broadcasted" or "directed". Broadcast applications of paraquat are
applied directly to the crop for foliage desiccation (to the crop and any weeds in the field) to
expedite harvest and reduce seed loss upon harvest. Therefore, occupational post-application
exposures are expected for broadcast applications and have been assessed. Per BEAD, at this
late stage of the crops, scouting to make sure the application was effective would be the only
activity conducted since all crops assessed are generally mechanically harvested. Additionally,
HED expects cotton mechanical harvest activities to result in the potential for post-application
worker exposures.
Directed spray applications of paraquat are targeted for control of individual weeds and grasses.
Such applications are made with the intent of minimizing the risk of injuring the crop and/or
non-target vegetation which are not tolerant of directed applications. Since these applications are
not expected to result in foliar residues on the crop and/or non-target vegetation, occupational
post-application exposures are not likely for directed applications and have not been assessed.
Occupational Post-Application Dermal Exposure Data and Assumptions
A series of assumptions and exposure factors served as the basis for completing the occupational
post-application risk assessments. Each assumption and factor is detailed below on an individual
basis.
Exposure Duration : HED classifies exposures from 1 to 30 days as short-term and exposures 30
days to six months as intermediate-term. For paraquat, based on the registered uses, short- and
intermediate-term exposures are expected. However, the POD for dermal exposures is the same
for both durations; therefore, the assessment is applicable to both short- and intermediate-term
exposures.
Transfer Coefficients : It is the policy of HED to use the best available data to assess post-
application exposure. Sources of generic post-application data, used as surrogate data in the
absence of chemical-specific data, are derived from ARTF exposure monitoring studies, and, as
proprietary data, are subject to the data protection provisions of FIFRA. The standard values
recommended for use in predicting post-application exposure that are used in this assessment,
known as "transfer coefficients", are presented in the ExpoSAC Policy 343" which, along with
additional information about the ARTF data, can be found at the Agency website44.
Scouting Transfer Coefficient: On November 1, 2018, the HED ExpoS AC discussed
occupational post-application exposures to desiccated crops and whether the associated post-
application activities and exposures would be significant. A proposal to reduce the scouting
activity transfer coefficient (TC) for reentry into fields with desiccated commodities was
discussed. Several factors were considered in the discussion, including: the likelihood of
42 William Chism (BEAD). Personal email communication, 07/5/2018. Subject: Re: Paraquat Post-Application Crops/Activities
Input Needed.
43 Available: https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handler-exposure-data
44 Available: https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handler-exposure-data
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scouting exposures for paraquat; exposures expected for defoliants vs desiccants; residue
availability following paraquat application and commodity desiccation; and the surrogate TCs
associated with scouting activities.
Likelihood of Scouting Exposures for Paraquat
A chemical-specific occupational post-application biomonitoring study in cotton was previously
reviewed by HED.45 The study, which monitored workers conducting scouting activities, was
conducted by the registrant as a worst-case representation of worker activities following paraquat
application: "This exposure study was representative of the normal work pattern of the crop
consultant during inspection of cotton following paraquat application as a harvest aid and
ensured that the timing of dermal exposure and absorption was as representative as possible."46
Study scouting activities consisted of walking 100 feet into the field, handling and attempting to
crack a few bolls, bending foliage and stems, and then crossing three or four rows and exiting the
field. The subjects spent 15 minutes in the field and 15 minutes out and then proceeded in
another untouched area of the field for a total of 10 trips into the field or 2.5 hours of field
exposure and 2.5 hours of between field activities. The selection of scouting activities by the
registrant is consistent with preliminary information provided by BEAD relating to the use
pattern and is thought to represent typical scouting activities following paraquat application.
However, it is unclear whether scouting practices have changed significantly from the time of the
biomonitoring study, 1994, to present.
As described above, BEAD indicated that scouting activities for all applicable crops and
mechanical harvesting for cotton would likely occur following broadcast application of paraquat
as a harvest aid/desiccant to make sure the application was effective. BEAD provided additional
information47 that these scouting activities could be conducted without spending a lot of time in
the field and scouting for cotton boll opening could occur either in the field or from a vehicle if
the leaf desiccation had occurred quickly. Further, BEAD provided a reference3 that described
that crops treated with paraquat could experience leaf desiccation in the range of 5 to 7 days;
thus, reducing the potential for exposures to foliage treated with paraquat.
Exposures Expectedfor Defoliants us. Desiccants
A previous meeting of the ExpoSAC resulted in the determination that post-application
assessment of scouting was not required for commodities treated with a defoliant. The July 1,
2004 ExpoSAC Meeting Minutes state, "The scouting that follows defoliant application would
consist only of looking at the plants from a distance to see if the leaves are falling off and does
not involve a typical scouting exposure. REI calculations are not needed for these exposures."
This determination was discussed in the November 1, 2018 ExpoSAC meeting; specifically, how
it should be interpreted for the assessment for paraquat which is a desiccant. A defoliant is a
chemical which causes leaves to drop from plants by resulting in more rapid development of
abscission layers. In contrast, desiccants are chemicals used to hasten harvest by accelerating the
drying of plant tissues. With desiccants, leaves are often cleaned from the seeds or plants
following harvest since these have not been abscised from the plant. Further, a link provided in a
BEAD email communication (http://ipm.ucanr.edu/PMG/rl 14800111.html) provided the
45 T. Manville. Review of Paraquat Worker Reentry Biomonitoring Study. D215539. 02/05/1996.
46 T. Iwata. Worker Exposure During Re-Entry into Paraquat-Treated Cotton Fields; Biological Monitoring in Georgia in 1994.
MRID 436182-02. 3/29/95.
47 Caleb Hawkins. Personal email communication, 11/16/2018. Subject: RE: EtED Paraquat Post-Application Activity Inquiry,
Cont'd.
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following information relating to paraquat usage in cotton: "PARAQUAT COMMENTS:
Considered a desiccant because at label rates it rapidly desiccates leaves and can cause them to
stick to the plants rather than to abscise. Used to help open mature bolls by causing direct injury
but is not generally applied as a desiccant until after 80% or more of bolls are open because it
can prevent further boll development and opening if applied too early." Since paraquat is not
particularly effective at leaf abscission, it is likely that the desiccated leaves can remain on the
plant; thus, resulting in the potential for paraquat exposures from scouting activities.
Residue Availability Following Paraquat Application
Typically, HED determines measures of available residue on treated commodities through
evaluation of submitted chemical-specific dislodgeable foliar residue (DFR) data. Chemical-
specific dislodgeable foliar residue data have not been submitted for paraquat. Therefore, the
potential for paraquat residues on treated commodities remains an uncertainty. However, since it
is likely that the desiccated leaves remain on the plant, there is the potential for paraquat residues
to remain on foliar surfaces. In the absence of DFR data, and the potential for residues to
remain, HED evaluated available field trial data for paraquat residues on desiccated commodities
and determined residues are present up to 3-4 weeks following application. Residues were
detectable in the following commodities/PHIs: undelinted cotton seed up to 14 day PHI; cotton
gin byproducts at 3 day PHI; wheat grain up to a 10 day PHI; wheat hay up to a 43 day PHI;
heat forage up to a 41 day PHI; soybean seed up to a 17 day PHI; soybean hay up to a 43 day
PHI; and soybean forage up to a 53 day PHI. Field trial data are not typically used for
quantitative assessment of occupational post-application exposures and risks since these data
represent residues available in/on the plant and, therefore, potentially overestimate the foliar
residues to which a worker would be exposed. However, these data confirm the presence of
paraquat residues in desiccated commodities and were considered relevant for qualitative
characterization of potential occupational post-application exposures.
TCs Associated with Scouting Activities
The TCs recommended for occupational post-application scouting activity assessments are 210
and 1,100 and are based on exposure studies conducted in non-desiccated fields and represent
significant foliar contact to the treated foliage. For the 1,100 TC, study participants walked
through high density, 3-6 foot crops of beans, corn, and peas touching and pulling leaves. The
210 TC is based on scouting activities in less dense crops of cotton and tomatoes. Since the
leaves of commodities treated with paraquat desiccate, but don't abscise from the plant, post-
application foliar exposures are expected. However, the levels of potential paraquat exposure
derived from using TCs generated from exposure studies conducted in higher density crops are
conservative, particularly for the highest of the TCs, 1,100.
Conclusion
The ExpoSAC evaluated all lines of evidence presented and determined 1) scouting activities are
likely following paraquat usage 2) as a desiccant, there is the potential for foliar contact
following application 3) paraquat residues are likely present on previously treated commodities
and 4) the higher surrogate scouting TC of 1,100, which represents activities in high density
crops, likely overestimates the exposures from scouting activities in desiccated commodities.
Ultimately, the ExpoS AC recommended that the lower scouting TC, 210, be used exclusively
since it allows for a more reasonable, albeit health protective, estimate of the anticipated post-
application exposures following paraquat application.
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Sunflower Scouting Transfer Coefficient: A default TC of 90 is recommended for sunflowers.
This TC is considered unique since it is applicable only to sunflowers and is the only hairy leaf
crop to which paraquat is applied. Therefore, HED recommends the default TC of 90 be used for
assessment of scouting exposures in sunflowers following paraquat usage.
Mechanical Cotton Harvest Transfer Coefficients: The recommended mechanical cotton harvest
TCs were recently reviewed due to the submission of summary information from a 2016 survey
by the National Cotton Council48 and an October 18, 2018 meeting with OPP and the National
Cotton Council. The summary of the survey was submitted as a response to public comments for
Registration Review of the active ingredient, cypermethrin, to make the case that the use of
trailers for harvesting cotton had become obsolete, indicating that tramping cotton should no
longer be included as a worker activity in cotton harvest post-application assessments. Due to
the timing of the submission and the potential implications for cotton harvest post-application
assessment for other active ingredients, this issue was also considered for paraquat. The
submitted summary information presents the results from a national survey of cotton mechanical
harvest practice, specifically the transition from conventional harvest activities for cotton
(mechanically or manually packed trailers), to the newer round mini module harvesters. The
survey results as presented in the submitted comment are as follows including a summary graph:
"A survey was sent to 436 cotton ginning operations inquiring how cotton was delivered to the
gin from fields. A total of 152 responses were received and were summarized by region of
operation. The survey shows high adoption of new harvest technology utilizing round bale or
mini module cotton harvesters (% Rd/Mini Mod). Many still utilize the conventional module
builders that are mechanically packed (% Conv. Mod). For the U.S. cotton crop, the wagon or
trailer transport method (% Trailers) is only used for a very small percentage of cotton and most
cotton transported in trailers is not packed. The manual packing method is used by a few
producers on a very small number of bales.
According to survey respondents (n=152):
• 0.17% of the harvested cotton is transported in trailers in the Southeast
• 0.29% of the harvested cotton is transported in trailers in the Midsouth
• 0.01%) of the harvested cotton is transported in trailers in the Southwest
• 0.16%o of the harvested cotton is transported in trailers in the West.
Of the 0.17%o of cotton transported in trailers in the Southeast, 18.57%) is manually packed and
81.43%o is not packed. Of the 0.29% of cotton transported in trailers in the Midsouth, 20%> is
mechanically packed and 80%> is not packed. In the Southwest and West regions, no cotton
transported in trailers is packed. The Southeast was the only region reporting the use of trailers
combined with manual packing of harvested cotton.
Applying the survey results from 2016 production to determine an estimate of manually packed
seed cotton at harvest yields: 3,891,000 total bales produced in the Southeast in 2016 with 0.17%>
transported in trailers = 6,615 bales originally transported in trailers. 18.57%) of those 6,615
bales manually packed = 1,228 bales manually packed (which would likely be lower if weighting
was applied). Therefore 1,228/16,524,000 (total U.S. production in bales of ginned lint) =
48 Steve Hensley. Response: Docket ID Number EPA-HQ-OPP-2012-0167. 4/30/2018.
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0.00743% of total U.S. cotton production was transported in trailers to the gin that were
manually packed."
National Cotton Council
December 2016 Gin Survey of Harvest Transport Practices.
Harvest Transport Methods
Mdsouin
Similar to HED's policy relating to the assessment of occupational handler exposures and risks
for human flaggers, which has also become an outdated practice, HED matches quantitative
occupational exposure assessment with appropriate characterization of exposure potential.
While HED will continue to present quantitative risk estimates for tramping cotton, we
acknowledge that cotton harvest practice is moving increasingly toward the newer round mini
module harvesters and use of trailers is becoming obsolete. Further, while HED expects that the
round mini module harvesters will potentially result in a reduced potential for post-application
exposures: 1) the TCs derived from the conventional harvest methods are the only exposure data
available for assessment of these activities and HED will continue to rely on these data; 2)
although < 1% of all cotton harvested nationally is manually packed, the potenti al remains for
manual tramping of cotton; and 3) although the mini module harvesting technique is becoming
more regularly used, the 2016 survey results suggest that the number of national respondents
using the mini module vs conventional harvest techniques is approximately equivalent (i.e., 40 -
60% reporting use of either dependent upon the area of the country surveyed). Following the
October 18, 2018 meeting with the National Cotton Council, HED provided information relating
to cotton harvest post-application risk assessment and identified the need for exposure data
specific to harvest activities with the round mini module and requested the raw survey data to be
formally submitted in order to confirm the summary information provided. The Agency will
continue to engage the National Cotton Council and monitor all available information sources,
including any new exposure or survey data, to best assess and characterize the cotton harvest
post-application harvest exposure potential.
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Application Rate: The application rates used in the assessment are presented in the Line by Line,
and Maximum Use Scenario Pesticide Label Usage Summary (PLUS) Reports as generated by
BEAD.
Exposure Time: The average occupational workday is assumed to be 8 hours.
Dislodgeable Foliar Residues: Chemical-specific dislodgeable foliar residue data have not been
submitted for paraquat. Therefore, this assessment uses HED's default assumption that 25% of
the application is available for transfer on day 0 following the application and the residues
dissipate at a rate of 10% each following day.
In the absence of chemical-specific DFR data, EPA uses default values. The 2012 Standard
Operating Procedures for Residential Pesticide Exposure Assessment includes an analysis of a
number of DFR studies, which resulted in the selection of a revised default values for the
fraction of the application rate available for transfer after a foliar application (Far). These values
are based on an analysis of 19 DFR studies. Since that time, the Agricultural Re-entry Task
Force has submitted information (MRID 49299201) that corrects an application rate error made
in the original submission of "ARF039 - Determination of Dermal and Inhalation Exposure to
Reentry Workers During Chrysanthemum Pinching in a Greenhouse" (EPA MRID 45344501).
As a result, the range of Far values was revised from 2% - 89% to 2% - 47%. In the data, a large
range of transferability is observed and this variability can potentially be attributable to many
factors such as active ingredient; formulation; field conditions in the studies; weather conditions
(e.g., humidity); or many other difficult to quantify factors. Although witnessed across multiple
chemicals, this range in Far values is not expected when considering DFR data for a single
chemical. At this time, the ARTF submission did not alter the selection of 25% as the
reasonable, high-end default value. Because DFR data are not available for paraquat, EPA is
using the default value of 25%. Although there may be a small degree of uncertainty in the use
of the default DFR value (i.e., there is a small chance that the Far value may exceed the
applicable default value), it is likely that the health-protective aspects of EPA's occupational
post-application assessment methodology will more than compensate for this potential
uncertainty. For example, when assessing residential and occupational post-application exposure
to gardens and ornamentals, EPA assumes the following: exposures occur to zero-day (i.e., day
of application ) residues every day of the assessed exposure duration (i.e., EPA assumes that no
dissipation or degradation occurs, it doesn't rain, etc.); individuals perform the same post-
application activities performed in the transfer coefficient study day after day (e.g., weeding,
harvesting, pruning, etc.); and individuals engage in these post-application activities for a high-
end amount of time every day (represented by data reflecting time spent gardening based on
survey data). Given these conservatisms and their potential compounding nature, EPA can rely
upon the calculated exposure estimates with confidence that exposure is not being
underestimated.
The highest estimated occupational post-application exposure using default DFR values is not
minimal in comparison to the level of concern (i.e., the calculated MOE is not greater than 2
times higher than the level of concern, MOE = 68 compared to the LOC of 100); therefore, HED
is recommending that DFR data (Guideline # 875.2100) be required to facilitate any necessary
exposure assessment refinements and to further EPA's general understanding of the availability
of dislodgeable foliar pesticide residues.
Page 62 of 103
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During cotton harvesting and scouting activities workers are expected to contact residues on
cotton bolls directly for which a "dislodgeable boll residue (DBR)" study would be required to
refine occupational post-application risks estimated for the crop. These chemical- and crop-
specific data are unique; DFR data for other crops cannot be used as a surrogate in the absence of
a DBR study. A DBR study should be conducted in accordance with Guideline # 875.2100.
Biomonitoring Exposure Data
An occupational post-application biomonitoring study available for paraquat was previously
reviewed by HED.49 These data are not used for occupational post-application risk quantitation
due to human ethics concerns relating to a 17-year-old study participant.50 "Under §26.1703,
EPA is prohibited from relying on research involving intentional exposure to human subjects
who are pregnant women (and therefore, their fetuses), nursing women, or children. Children are
persons under 18 years old. This study falls within that category." Therefore, HED does not rely
on this biomonitoring study as a part of the paraquat occupational post-application quantitative
exposure and risk assessment.
Occupational Post-Application Non-Cancer Dermal Exposure and Risk Estimate Equations
The algorithms used to estimate non-cancer exposure and dose for occupational post-application
workers can be found in the occupational and residential exposure assessment that supports this
document.
Occupational Post-Application Non-Cancer Dermal Risk Estimates
Occupational post-application exposure and risks estimated for scouting activities are not of
concern (i.e., an MOE > 100) on the day of product application for all crops assessed except for
alfalfa. For alfalfa, reentry risks are not of concern 4 days following product application. Cotton
post-application risks are not of concern 11 days following application for the mechanical
harvesting activity, module builder; not of concern 20 days following application for the
mechanical harvesting activities, picker operator and raker; and not of concern 27 days following
application for the mechanical harvesting activity, tramper. The summary of the anticipated post-
application activities and associated transfer coefficients for the registered crops/use sites is
presented in Table 11.3.1.
Tabic 11.3.1. Occupational Post-Application Non-Canccr Exposure and Risk Estimates for Paraquat
Crop/Site
Activities
Transfer
Coefficient
(cm2/hr)
Application
Rate
DFR/DBR1
Dermal Dose
(mg/kg/dav)2
MOE on Day 0J
DAT4
Alfalfa
Scouting
210
1.5
4.2
0.088
68
4
Guar, Lentils
1.0
2.8
0.059
100
0
Corn, field
1.0
2.8
0.059
100
0
Corn, pop
1.0
2.8
0.059
100
0
Cotton
1.0
2.8
0.059
100
0
Harvesting,
Mechanical,
Module Builder
Operator
900
2.0
0.18
33
11
49 T. Manville. Review of Paraquat Worker Reentry Biomonitoring Study. D215539. 02/05/1996.
50 M. Arling. Ethics Review of Paraquat Biomonitoring Study (MRID 43618202). 12/11/2018.
Page 63 of 103
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Tabic 11.3.1. Occupational Post-Application Non-Canccr Exposure and Risk Estimates fo
rParaquat
Crop/Site
Activities
Transfer
Coefficient
(cm2/hr)
Application
Rate
DFR/DBR1
Dermal Dose
(mg/kg/day)2
MOE (in Day 0J
DAT4
Harvesting,
Mechanical,
Picker Operator
2,400
0.48
13
20
Harvesting,
Mechanical,
Raker
2,400
0.48
13
20
Harvesting,
Mechanical,
Tramper
5,050
1.0
5.9
27
Grasses
Grown for
Seed
1.0
2.8
0.059
100
0
Forage Crop
1.0
2.8
0.059
100
0
Clary, Sage
210
0.80
2.2
0.047
130
0
Peanut
Scouting
1.0
2.8
0.059
100
0
Potato
1.0
2.8
0.059
100
0
Soybean
1.0
2.8
0.059
100
0
Sugarcane
1.0
2.8
0.059
100
0
Sunflower
90
1.0
2.8
0.025
240
0
1 DFR = Application Rate (lb ai/A) x F x (l-D)' x 4.54E8 |xg/lb x 2.47E-8 acre/cm2; where F = 0.25 and D = 0.10 per day
DBR = Application Rate (lb ai/A) x F x (l-D)' x 4.54E8 |xg/lb x 2.47E-8 acre/cm2; where F = 2 and D = 0.10 per day
2 Daily Dermal Dose = [DFR/DBR (|xg/cm2) x Transfer Coefficient x 0.001 mg/^g x 8 hrs/day] 4- BW (80 kg).
3 MOE = POD (6 mg/kg/day) ^ Daily Dermal Dose.
4 DAT = Day after treatment/application for MOE to be greater than the LOC (100).
Restricted Entry Interval
Paraquat acute toxicity is low via the dermal route (Toxicity Category III) and not irritating to
the skin (Toxicity Category IV); however, it is severely irritating to mucous membranes
(Toxicity Category I for eye irritation). It is not a skin sensitizer. Under 40 CFR 156.208 (c) (2),
active ingredients classified as Acute I for acute dermal, eye irritation and primary skin irritation
are assigned a 48-hour REI. Therefore, the currently labeled REIs which range from 12 to 24
hours do not comport with 40 CFR 156.208 (c) (2) requirements. Further, the number of days
required for estimated post-application risks associated with paraquat usage estimated for reentry
range from 0 to 27 days and may require revision of the labeled REIs to address these concerns.
11.3.2 Occupational Post-Application Inhalation Exposure/Risk Estimates
There are multiple potential sources of post-application inhalation exposure to individuals
performing post-application activities in previously treated fields. These potential sources
include volatilization of pesticides and resuspension of dusts and/or particulates that contain
pesticides. The agency sought expert advice and input on issues related to volatilization of
pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel
(SAP) in December 2009, and received the SAP's final report on March 2, 2010
(https://www.regulations.gov/document?D=EPA-HO-OPP-2009-0687-0Q37). The agency has
evaluated the SAP report and has developed a Volatilization Screening Tool and a subsequent
Volatilization Screening Analysis Qittps://www.regulations.gov/docket?D=EPA-HO-OPP-2Q14-
0219). During Registration Review, the agency will utilize this analysis to determine if data (i.e.,
Page 64 of 103
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flux studies, route-specific inhalation toxicological studies) or further analysis is required for
paraquat.
12.0 Public Health Incident Data Review
E. Evans and S. Recore. Paraquat: Tier IIHuman Incidents Report. D446902. 07/25/2018.
HED performed an updated Tier II review of human incidents for paraquat using the following
sources: OPP Incident Data System (IDS); and the Centers for Disease Control and
Prevention/National Institute for Occupational Safety and Health (CDC/NIOSH) Sentinel Event
Notification System for Occupational Risk-Pesticides (SENSOR); the Agency-sponsored
National Pesticide Information Center (NPIC); and California's Pesticide Incident Surveillance
Program (PISP) databases.
Paraquat is highly acutely toxic when inhaled or ingested. HED found that the acute health
effects reported to the incident databases queried are consistent across the databases. These
health effects primarily include dermal, ocular, and neurological effects. HED did not identify
any aberrant effects outside of those anticipated.
Most incidents were classified as low to moderate severity. The effects reported were generally
mild/minor to moderate and resolved rapidly. However, high severity incidents and deaths did
occur due to accidental ingestion, exposure, and misuse.
Across the databases reviewed, the majority of paraquat incidents were occupational exposure
accidents which occurred during application or handling - primarily from leaks/spills/splashes or
equipment malfunctions. Dermal symptoms were the most frequently reported symptoms among
cases including: welts, hives, peeling skin, chemical burns, swelling, blisters, lesions; followed
by ocular symptoms, including: blurred vision, ocular pain, chemical conjunctivitis, corneal
abrasion, vision problems
Main IDS 2012-2018 identified 63 paraquat incidents. 81% were moderate severity (systemic
health effects). Also, five were bystander exposures (drift). Four paraquat deaths & four high
severity incidents were also identified: two severe applicator/handler accidents, two fatal
accidental ingestions, and four intentional harm cases (2 suicides, one attempted suicide, and one
malicious poisoning attempt)
SENSOR-Pesticides (aggregate data through 2014) found 140 paraquat case reports; most cases
were occupational and involved applying, mixing/loading or repairing equipment when
exposed. Many cases involved PPE issues, including spray/splash getting into eyes although
wearing safety glasses. Many cases involved application equipment failures, including backpack
leaks. Many cases were not adequately trained when applying under supervision, but these cases
are not a violation of federal requirements as the new safety requirements are not yet in effect.
Finally, a review of paraquat incidents for trend over time in IDS was conducted. The number of
paraquat incidents reported to IDS from 2008 to 2017 has remained relatively constant. There
has been an average of 22 paraquat incidents (ranging from a low of 15 incidents to a high of 32
incidents) reported to IDS per year over the last 10 years.
Page 65 of 103
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13.0 References
A. Wray. Paraquat Dichloride: Systematic Review of the Literature to Evaluate the Relationship
Between Paraquat Dichloride Exposure and Parkinson's Disease. D449106; TXR 0057888.
06/26/2019.
A. Wray. Paraquat Dichloride: Review of the Paraquat Dichloride Open Literature for
Registration Review. D449107; TXR 0057887. 06/26/2019
A. Niman. Paraquat Dichloride: Tier II Epidemiology Report. D449108. 06/26/2019.
T. Morton. Paraquat Dichloride: Acute and Chronic Aggregate Dietary Exposure and Risk
Assessments for the Registration Review of Paraquat Dichloride. D447108. 06/13/2019.
T. Morton. Paraquat Dichloride. Registration Review Summary for Paraquat Dichloride.
D447109. 06/13/2019.
W. Britton. Paraquat Dichloride: Occupational and Residential Registration Review Exposure
and Risk Assessment. D448252. 06/26/2019.
J. Lin. Review of Jar Test Results for Drinking Water Assessment Purpose. D396402.
01/10/2012;
E. Evans and S. Recore. Paraquat: Tier II Human Incidents Report. D446902. 07/25/2018.
Page 66 of 103
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Appendix A. Toxicology Profile and Executive Summaries
A.l Toxicology Data Requirements
The requirements (40 CFR 158.500) for food uses for paraquat are in Table A. 1. Use of the new guideline numbers
does not imply that the new (1998) guideline protocols were used.
Tabic A.l. Toxicology Data Requirements for Paraquat Food Use Registrations
Studv
Technical
Required
Satisfied
870.1100
870.1200
870.1300
870.2400
870.2500
870.2600
Acute Oral Toxicity
Acute Dermal Toxicity
Acute Inhalation Toxicity.
Primary Eye Irritation
Primary Dermal Irritation.
Dermal Sensitization
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
870.3100
870.3150
870.3200
870.3250
870.3465
Oral Subchronic (rodent)
Oral Subchronic (nonrodent).
21-Day Dermal
90-Day Dermal
90-Day Inhalation
no
yes
yes
CR
yes
yes
yes
yes
870.3700a Developmental Toxicity (rodent)
870.3700b Developmental Toxicity (nonrodent).
870.3800 Reproduction
yes
waived2
yes
yes
yes2
yes
870.4100a Chronic Toxicity (rodent)
870.4100b Chronic Toxicity (nonrodent).
870.4200a Oncogenicity (rat)
870.4200b Oncogenicity (mouse)
870.4300 Chronic/Oncogenicity
yes
no
yes
yes
yes
yes
yes3
yes
yes3
870.5100 Mutagenicity—Gene Mutation - bacterial
870.5300 Mutagenicity—Gene Mutation - mammalian
870.5375 Mutagenicity—Structural Chromosomal Aberrations.
870.5395 Mutagenicity—Other Genotoxic Effects
yes
yes
yes
yes
yes
yes
yes
yes
870.6100a Acute Delayed Neurotoxicity (hen)
870.6100b 90-Day Neurotoxicity (hen)
870.6200a Acute Neurotoxicity Screening Battery (rat)....
870.6200b 90-Day Neurotoxicity Screening Battery (rat).
870.6300 Develop. Neurotoxicity
no
no
yes
yes
no
yes
yes
870.7485 General Metabolism.
870.7600 Dermal Penetration...
870.7800 Immunotoxicity
yes
CR
yes
yes
yes
yes
1 Subchronic oral exposure in rodents was evaluated in the developmental, reproduction, and chronic/oncogenicity
rodent guideline studies. Consequently, a separate oral subchronic study is not required.
2Recommended for a waiver by HASPOC (TXR 0056294, K. Rury, 04/12/2012).
3Chronic toxicity (rat) and Oncogenicity (rat) study requirements were satisfied by the combined Chronic/
Oncogenicity study in rats.
CR = conditionally required
Page 67 of 103
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A.2 Toxicity Profiles
Table A.2.1. Aeute Toxicity Profile - Paraquat Dichloride
Guideline
N o./Stu d v/S pccies/St rai n
MRID/TXR
#/Pu rity/Classification
Results
Toxicity
Category
870.1100
Acute oral (rat)
Alpk:APfSD SPF Wistar
rats
43685001 (1994)
TXR 0011944
33.0% paraquat
Acceptable
Male LDso = 344 mg/kg1
Female LDso = 283 mg/kg1
II
870.1200
Acute dermal (rat)
Alpk:APfSD SPF Wistar
rats
43685002 (1994)
TXR 0011944
33% paraquat dichloride
Acceptable
Male/Female LDso > 2000 mg/kg
III
870.1300
Acute inhalation (rat)
Alderley Park SPF rats
00046105 (1968)
TXR 0000248
Crystalline Paraquat CI2
Male/Female LCso = 1 |ig paraquat
ion/L2
I3
870.2400
Eye irritation (rabbit)
NZ White rabbits
43685004 (1994)
TXR 0011944
33.0% paraquat ion
Acceptable
Moderate to severe irritation
II
870.2500
Dermal irritation (rabbit)
NZ White rabbits
43685004 (1994)
TXR 0011944
33.0% paraquat ion
Acceptable
Minimal irritation
IV
870.2600
Skin sensitization
43685005 (1994)
TXR 0011944
Acceptable
Negative
N/A
1 LD50 values are reported based on mg paraquat dichloride technical product. Assuming the purity is referring to
paraquat cation, the male and female LD5o values are 114 and 93 mg paraquat ion/kg, respectively.
2 Estimated by the study authors. Results are supported by 2005 study conducted with technical paraquat dichloride (0.36
|ig paraquat ion/L< Female LCso <2.49 |ig paraquat ion/L; MRID 48877203)
3 Reviewer for this study did not determine a Toxicity Category or provide a classification; however, the estimated LCso
falls into Toxicity Category I. This is supported by the conclusions of MRID 48877203 that paraquat dichloride technical
is Toxicity Category I for acute inhalation.
Page 68 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.3150
90-Day oral toxicity (dog)
Beagle dogs
00072416 (1981)
TXR 0053747
Acceptable/
Guideline
32.2% w/w paraquat ion
0, 0.2, 0.5, 1.5, 3 mg
paraquat ion/kg/day via diet
for 13 weeks
NOAEL = 0.5 mg paraquat ion/kg/day
LOAEL = 1.5 mg paraquat ion/kg/day based on increased
lung weight and incidence of alveolitis in both sexes.
*Maximum tolerated dose was exceeded at 3 mg/kg/day
870.3200
21-Day dermal toxicity
(rabbit)
NZ White rabbits
00156313 (1986)
TXR 0057886
Acceptable/
Guideline
43.5% w/w paraquat ion
0,0.5, 1.15,2.6, 6 mg
paraquat ion/kg/day applied
6 hrs/day, 7 days/week over
a 21-day period
Systemic NOAEL = 6 mg paraquat ion/kg/day (HDT)
Systemic LOAEL = not established
Dermal NOAEL = 1.15 mg paraquat ion/kg/day
Dermal LOAEL = 2.6 mg paraquat ion/kg/day based on
small scabs at the treatment site in both sexes, and
epidermal erosion/ulceration, surface exudation, acanthosis,
and inflammation in males
870.3465
21-Day inhalation toxicity
SD rats
00113718 (1979)
TXR 0053747
Acceptable/Guideline
40% w/v paraquat ion
0,0.01,0.1,0.5, 1.3 ng
paraquat ion/L, whole body
for 6 hrs/day, 5 days/week
for 3 weeks
NOAEC = 0.01 |ig paraquat ion/L
LOAEC = 0.1 |ig paraquat ion/L based on squamous
keratinizing metaplasia and hyperplasia of the epithelium of
the larynx
*Mortality at 1.3 |ig paraquat ion/L
870.3700a
Prenatal developmental
(rat)
Alderly Park Wistar-
derived (Alpk:SPF SD) rats
00113714 (1978)
TXR 0057886
Acceptable/
Guideline
38% w/v paraquat ion
0, 1, 5, 10 mg paraquat
ion/kg/day via gavage on
gestation day 6 through 15,
inclusive
Maternal NOAEL = 1 mg paraquat ion/kg/day
Maternal LOAEL = 5 mg paraquat ion/kg/day based on
mortality, clinical signs of toxicity (piloerection, thin and
hunched appearance, croaking), and decreased body weight
gains.
Developmental NOAEL = 1 mg paraquat ion/kg/day
Developmental LOAEL = 5 mg paraquat ion/kg/day based
on slightly decreased fetal body weights and on delayed
ossification.
870.3700a
Prenatal developmental
(rat)
Alderly Park Wistar-
derived (Alpk:SPF SD) rats
43964701 (1992)
TXR 0053747
Acceptable/
Guideline
38.2% w/v paraquat ion
0, 1, 3, 8 mg paraquat
ion/kg/day via gavage on
gestation day 7 through 16,
inclusive
Maternal NOAEL = 8 mg paraquat ion/kg/day
Maternal LOAEL = not established
Developmental NOAEL =8 mg paraquat ion/kg/day
Developmental LOAEL = not established
Page 69 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.3700a
Prenatal developmental
(mouse)
SPF Alderley Park mice
00096338 (1978)
TXR 0053747
Acceptable/
Guideline
38% w/v paraquat ion
(100% paraquat dichloride)
0, 1, 5, 10 mg paraquat
ion/kg/day via gavage on
gestation days 6-15,
inclusive
Maternal NOAEL = 1 mg paraquat ion/kg/day
Maternal LOAEL = 5 mg paraquat ion/kg/day based
decreased maternal body weight gain.
Developmental NOAEL = 10 mg paraquat ion/kg/day
Developmental LOAEL = not established
870.3700a
Prenatal developmental
(mouse)
Crl:CD-l (ICR) BR mice
43949902 (1992)
TXR 0053747
Acceptable/
Guideline
38.2% w/v paraquat ion
0, 7.5, 15, 25 mg paraquat
ion/kg/day via gavage on
gestation days 6-15,
inclusive
Maternal NOAEL = 15 mg paraquat ion/kg/day
Maternal LOAEL = 25 mg paraquat ion/kg/day based on
mortality, clinical signs of toxicity, decreased body
weights, and body weight gains, increased lung weights,
and gross lesions in the lung
Developmental NOAEL = 15 mg paraquat ion/kg/day
Developmental LOAEL = 25 mg paraquat ion/kg/day based
on retardation of the skeleton and decreased fetal body
weights
870.3700b
Prenatal developmental
(rabbits)
NZ White rabbits
49009505 (1991)
TXR 0056764
Unacceptable
33.6% w/w paraquat ion
0, 1, 1.5, 2 mg paraquat
ion/kg/day via gavage on
gestation days 7 through 19,
inclusive
Study was not conducted in compliance with GLP, no
Quality Assurance statement was provided, and no
individual data were provided.
870.3700b
Prenatal developmental
(rabbits)
Recommended to be waived by HASPOC (TXR 0056294)
870.3800
Reproduction and fertility
effects (rats)
Wistar-derived Alderley
Park rats
00126783 (1982), 00149749,
00149748 (1985)
TXR 0053747
Acceptable/
Guideline
32.7% w/w paraquat ion
0, 1.25, 3.75, 7.5 mg
paraquat ion/kg/day
administered via diet
Parental NOAEL = 1.25 mg paraquat ion/kg/day
Parental LOAEL = 3.75 mg paraquat ion/kg/day based on
increased incidences of alveolar histiocytes in both sexes.
Offspring NOAEL = 7.5 mg paraquat ion/kg/day
Offspring LOAEL = not established
* sporadic evidence of histopathology lesions in offspring
were observed at 7.5 mg paraquat ion/kg/day, but due to the
sample analysis methods it could not be determined if they
were treatment related. These lesions were not observed at
dose levels that impact the paraquat risk assessment;
therefore, the DER for this study was not updated.
Reproduction NOAEL = 7.5 mg paraquat ion/kg/day
Reproduction LOAEL = not established
Page 70 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.4100a
Chronic toxicity
(rat)
See 870.4300
870.4100b
Chronic toxicity (dog)
Beagle dogs
00132474 (1983)
TXR 0053747
Acceptable/
Guideline
32.2% w/w paraquat ion
M: 0,0.45,0.93, 1.51 mg
paraquat ion/kg/day
F: 0, 0.48, 1, 1.58 mg
paraquat ion/kg/day via diet
for 52 week
NOAEL = 0.45 mg/kg/day in males and 0.48 mg/kg/day in
females
LOAEL = 0.93 mg/kg/day in males and 1 mg/kg/day in
females based on increased severity of chronic pneumonitis
and gross lung lesions in both sexes, and focal pulmonary
granulomas in males
870.4200
Carcinogenicity (mouse)
Swiss-derived mice
00059727, 00087924 (1981)
TXR 0053747
Acceptable/
Guideline
32.7% w/w paraquat ion
(44.6% w/w paraquat
dichloride)
0, 0 (2nd control), 1.9, 5.6,
15.0/18.8 mg paraquat
ion/kg/day administered via
diet for 99 weeks
*Doses estimated by
reviewers
NOAEL = 1.9 mg paraquat ion/kg/day
LOAEL = 5.6 mg paraquat ion/kg/day based on decreased
body weights and food consumption in females, and
increased incidences of renal tubular necrosis, tubular
dilation, and interstitial nephritis in males
*No evidence of increased tumor incidence when compared
to controls
870.4200
Carcinogenicity (mouse)
JCL:ICR mice
40202403 (1982)
TXR 0053747
Acceptable/
Guideline
98% paraquat dichloride
(% paraquat ion not
reported)
0,0.3, 1.5,4.5, 15 mg
/kg/day administered via diet
for 104 weeks
*Doses estimated by
reviewers
NOAEL = 4.5 mg/kg/day
LOAEL =15 mg/kg/day based on reduced survival
(females)
*No evidence of increased tumor incidence when compared
to controls
Page 71 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.4300
Combined chronic
toxicity/carcinogenicity
(rats)
Fischer 344 rats
00138637 (1983), 00153223
(1985), 40202401, 40202402
(1987), 41317401 (1989)
TXR 0053747
Acceptable/
Guideline
32.7% w/w paraquat ion
(96.1% paraquat dichloride)
0, 0 (2nd control), 1.25, 3.75,
7.5 mg paraquat ion/kg/day
administered via diet for 117
weeks in males and 124
weeks in females
*Doses estimated by
reviewers
NOAEL = 1.25 mg paraquat ion/kg/day
LOAEL = 3.75 mg paraquat ion/kg/day based on ocular
opacity in females corroborated by microscopic lenticular
changes.
870.4300
Combined chronic
toxicity/carcinogenicity
(rats)
Wistar rats
40218001 (1982)
TXR 0053747
Acceptable/
Guideline
98% paraquat dichloride
(% paraquat ion not
reported)
M: 0,0.25, 1.26,4.15, 12.25
mg/kg/day
F: 0, 0.3, 1.5,5.12, 15.29
mg/kg/day
administered via diet for 104
weeks
NOAEL = 4.15 mg/kg/ day in males and 5.12 mg/kg/day in
females
LOAEL = 12.25 mg/kg/day in males and 15.29 mg/kg/day
in females based on mortality
870.5100
Gene Mutation
Bacterial reverse mutation
Salmonella typhimurium
TA98, 100, 1535, 1537,
1538
00100440 (1977)
TXR 0053747
Acceptable/
Guideline
99.9 % paraquat dichloride
0-1000 nl/plate - /+ S9
No evidence of induced mutant colonies over
background up to cytotoxic concentrations (>100 |il/plate -
/+ S9)
870.5100
Gene Mutation
Bacterial reverse mutation
Salmonella typhimurium
TA98, 100, 1535, 1538
00100441 (1977)
TXR 0053747
Acceptable/
Guideline
99 % paraquat dichloride
0-5000 nl/plate - /+ S9
No evidence of induced mutant colonies over
background up to cytotoxic concentrations (>500
ug/plate).
Page 72 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.5375
Cytogenetics
In vitro mammalian cell
chromosomal aberration
assay
Human peripheral blood
lymphocytes
00152692 (1985)
TXR 0053747
Acceptable/
Guideline
99.6% paraquat dichloride
0.75 - 3500 ng/mL -/+ S9
for 3 hours with a 25 hour
recovery period
Increases in aberrant cells only observed at cytotoxic
concentrations in presence and absence of S9-activation
870.5385
Cytogenetics
Mammalian bone marrow
chromosomal aberration
test (rat)
Wistar rats
40202405 (1987)
TXR 0053747
Acceptable/
Guideline
33.0% w/w paraquat ion
0, 15, 75, 150 mg paraquat
ion/kg via oral gavage
No evidence of chromosome aberration induced over
background
870.5450
Other Geneotoxicity
Dominant lethal assay
(mouse)
Male CD-I mice
00100442 (unknown)
TXR 0053747
Acceptable/
Guideline
23.8% w/v paraquat ion
0, 0.04, 0.4, 4 mg/kg/day via
gavage for 5 days
No time-related positive response of increased pre- or post-
implantation loss compared to controls.
870.5900
Other Geneotoxicity
In vitro sister chromatid
exchange assay
Chinese hamster lung
fibroblasts
00152695 (1985)
TXR 0053747
Acceptable/
Guideline
99.4% paraquat dichloride
0 - 2470 ug/mL +/- S9
Positive response of SCE induced over background with
clear dose response in presence of S9-activation; Positive
response of SCE induced over background w/o clear dose-
response in absence of S9-activation.
870.5550
Other Geneotoxicity
Unscheduled DNA
synthesis in primary rat
hepatocytes
Primary rat hepatocytes
00152693 (1985)
TXR 0053747
Acceptable/
Guideline
99.6% paraquat dichloride
0 - 10"9 M
No evidence of unscheduled DNA synthesis
Page 73 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.5550
Other Geneotoxicity
Unscheduled DNA
synthesis in primary rat
hepatocytes
Male Alderly Park albino
rats
40202404 (1987)
TXR 0053747
Acceptable/
Guideline
33.0% w/v paraquat ion
0, 45, 78, 120 mg/kg
administered via drinking
water
No evidence of unscheduled DNA synthesis
870.6200a
Acute neurotoxicity
screening battery
Alpk:ApfSD rats
47994201 (2006)
TXR 0057886
Acceptable/
Guideline
33.4% w/w paraquat ion
(46.1% w/w paraquat
dichloride)
0, 8.4, 25.1, 84 mg paraquat
ion/kg administered via
gavage in deionized water
Neurotoxicity NOAEL = 84 mg paraquat ion/kg
Neurotoxicity LOAEL = not established
Systemic NOAEL = 25.1 mg paraquat ion/kg
Systemic LOAEL = 84 mg paraquat ion/kg based on
clinical signs of toxicity (piloerection, irregular breathing,
flaccidity, pinched sides, upward spinal curvature, ocular
discharge) and mortality
870.6200b
Subchronic neurotoxicity
screening battery
Alpk:ApfSD rats
47994202 (2006)
TXR 0055342
Acceptable/
Guideline
33.4% w/w paraquat ion
(46.1% w/w paraquat
dichloride)
M: 0, 1, 3.4, 10.2 mg
paraquat ion/kg/day
F: 0, 1.1,3.9, 11.9 mg
paraquat ion/kg/day
administered via diet for 13
weeks
NOAEL = 10.2-11.9 mg paraquat ion/kg/day
LOAEL = not established
870.6300
Developmental
neurotoxicity
Study not submitted
870.7485
Metabolism and
pharmacokinetics (rat)
Guideline study not submitted, see non-guideline study
Page 74 of 103
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Tabic A.2.2 Subchronic, Chronic and Other Toxicity Profile - Paraquat Dichloridc
Guideline No./ Study
Type/Animal Species and
Strain
MRID No. or Study
Authors (vcar)/TXR #/
Classification /Doses
Results
870.7800
Immunotoxicity (mouse)
Female B6C3F1 mice
48667301 (2011)
TXR 0056276
Acceptable/
Guideline
99.9% w/w paraquat
dichloride
(% paraquat ion not
reported)
0, 6.9, 19.9, 27.3 mg/kg
bw/day administered via diet
for 28 days
Immunotox/Systemic NOAEL = 27.3 mg/kg/day
Immunotox/Systemic LOAEL = not established
No suppression of the humoral or innate components of the
immune system.
Tabic A.2.3 Special (Non-guidclinc) Studv Toxicity Profile - Paraquat
Guideline No./ Study
Type/Animal Species
and Strain
MRID No. or Study Authors
(year)/ Classification /Doses
Results
Non-guideline
Sub-chronic
neurotoxicity
C57BL/6J mice
49122304 (2013)
TXR 0056764
Unacceptable
99.9% a.i.
M: 0, 1.7, 10.2 mg paraquat
ion/kg/day
F: 0, 2.7, 15.6 mg paraquat
ion/kg/day
Administered via diet for 13
weeks
Positive Control: MPTP 10
mg/kg injected 4 times every 2
hours on a single day
The study presented null results for the paraquat exposed
animals; however, homogeneity and stability data for the
paraquat-treated diet were inadequate and created
uncertainty in the exposure analysis and reported dose
levels.
Positive Control Results: Reversible clinical signs including
hunched posture, piloerection, hypoactivity, and/or tremors,
and weight loss after dosing in both sexes, significant
decrease in TH+ neurons and total contour volume in SNpc,
decreases in DA, DOPAC, and HVA concentration, and
increase in DA turnover in striatal tissues in males only. No
effect on brain weight.
Non-guideline
Sequential
neuropathology
C57BL/6J male mice
49122301 (2013)
TXR 0057437
Acceptable/Non-guideline
99.9% a.i.
0, 10, or 15 mg/kg/week
Administered via IP injection
once per week for up to 3
weeks
Positive Control: MPTP 10
mg/kg injected 4 times every 2
hours on a single day
No treatment related clinical signs observed and no
difference in brain appearance. Paraquat concentration
increased with cumulative dose. No evidence of
neuropathology anomalies in the SNpc; however,
stereology of immunostained sections demonstrated a
decrease in TH+ and total neurons in the SNpc in animals
treated with 3x15 mg/kg paraquat. Total neuron counts
with CVO stained did not corroborate finding of decreased
total neuron count.
Positive Control Results: Evidence of neuron damage and
neuron death in SNpc based on staining and stereology. As
with the paraquat treated animals, total neuron count of
CVO stained samples did not demonstrate significant
decrease in total neuron count.
Page 75 of 103
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Tabic A.2.3 Special (Non-guideline) Studv Toxicity Profile - Paraquat
Guideline No./ Study
Type/Animal Species
and Strain
MRID No. or Study Authors
(year)/ Classification /Doses
Results
Non-guideline
Neurotoxicity range-
finding
C57BL/6J male mice
49122302 (2012)
TXR 0057437
Acceptable/Non-guideline
99.9% a.i.
0, 10, 15, or 25 mg/kg/week
Administered via IP injection
once per week for 3 weeks
Positive Control: MPTP 10
mg/kg injected 4 times every 2
hours on a single day
Mortality at 25 mg/kg/week. No treatment-related effects
on dopamine, dopamine metabolites, or dopamine turnover.
Non-significant decrease in TH+ neurons in the SNpc and
significant decrease in mean total contour volume in brain
sections at 15 and 25 mg/kg/week. Total neuron count was
not statistically different from controls in any treatment
group.
Positive Control Results: Decrease in total contour volume
and TH+ neurons with variable statistical significance
based on the staining procedure, non-significant decrease in
total neurons, decrease in dopamine and dopamine
metabolite concentrations and increase in dopamine
turnover in striatal samples
Non-guideline
Multi-time and multi-
dose neuropathology
C57BL/6J male mice
49122303 (2013)
TXR 0057437
Acceptable/Non-guideline
99.9% a.i.
0, 10, 15, or 25 mg/kg/week
Administered via IP injection
once per week for up to 3
weeks
Positive Control: MPTP 10
mg/kg injected 4 times every 2
hours
No neuropathology effects observed in the striatal and
substantia nigra brain tissues, transient decrease in body
weight, two 25 mg/kg animals euthanized in extremis
Positive Control Results: Evidence of neuron damage and
neuron death in the SNpc
Non-guideline
Sub-chronic study
3 and 8-week-old
C57BL/6J male mice
50733301 (Lou etal. 2016)
TXR 0057886
Acceptable
>98% a.i.
0, 3.6, or 7.2 mg paraquat
ion/kg/day via gavage for 28
consecutive days
NOAEL = not established
LOAEL = 3.6 mg paraquat ion/kg/day based on mortality in
the 3-week-old mice
*mortality in 8-week-old mice only observed at 7.2 mg
paraquat ion/kg/day
**mortalities observed on days 2, 3, 5, and 6 in the 3-week-
old mice are considered to conservatively represent an acute
response to exposure
Page 76 of 103
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Tabic A.2.3 Special (Non-guideline) Studv Toxicity Profile - Paraquat
Guideline No./ Study
Type/Animal Species
and Strain
MRID No. or Study Authors
(year)/ Classification /Doses
Results
Non-guideline
Sub-chronic study
8-week-old Wistar male
rats
Chen et al. 2017
Acceptable
Not reported (assumed high
purity based on source)
0, 0.5, 2, or 8 mg paraquat
/kg/day via gavage for 8 weeks
Sperm, tissue weight, and testis tissue effects were observed
in all dose groups, though the magnitude of change in these
effects were small in the 0.5 mg/kg/day treatment group.
Absolute testis and epididymis weight in the 0.5 mg/kg/day
group were <13% different from controls and the changes
in weight were not significant after normalizing for body
weight. Sperm number in the 0.5 mg/kg/day treatment
group decreased by <10% relative to controls, the increase
in total percentage of abnormal sperm was marginal, and no
significant impact on sperm motility or viability was
observed. Testis tissue from rats in this treatment group also
did not exhibit evidence of oxidative stress or apoptosis.
Given the low magnitude of the change from controls, none
of the reproductive effects observed in rats from the 0.5
mg/kg/day treatment group were indicative of an adverse
response to treatment. Rats from the 2 and 8 mg/kg/day
treatment groups exhibited a wider array of changes in the
male reproductive tissues (decreased testis weight,
decreased sperm number concurrent with decrease in sperm
viability and increase in percent of head, tail and multiple
sperm abnormalities, and evidence of oxidative stress and
apoptosis in testis tissue) that were significantly different
from the controls and generally of higher magnitude
relative to the 0.5 mg/kg/day group.
Non-guideline
Urinary excretion in
monkeys
00126096(1982)
TXR 0053747
Acceptable/Non-guideline
99.8% radiochemical purity
Single intramuscular injection
of 607 ug paraquat dichloride
*Monkeys eliminated 43.5-51.5% of the administered
radioactivity in the urine within 24 hours post-dose and
52.3-72.3% (average 58.6%) within 7 days post-dose.
Page 77 of 103
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Tabic A.2.3 Special (Non-guideline) Studv Toxicity Profile - Paraquat
Guideline No./ Study
Type/Animal Species
and Strain
MRID No. or Study Authors
(year)/ Classification /Doses
Results
Non-guideline
Metabolism
00055107
Daniel and Gage 1966
TXR 0005824
Acceptable
0.5, 0.7, 4 ,6, 50 mg/kgvia
oral gavage
Oral absorption from a low dose (4-6 mg/kg) gavage
exposure was estimated to be approximated 6% of the
administered dose (AD) based on the amount excreted in
the urine up to 96 hours after exposure (no biliary data for
these dose groups were available). Absorption from a 50
mg/kg oral dose was estimated to be 8-14% of the AD
based on the urinary content alone. The study authors did
not provide information on radioactivity content in fecal or
biliary excretion nor calculate a percent recovery in rats
exposed to the higher dose. Regardless of dose, paraquat
dichloride was primarily excreted in the feces with minor
contribution from the renal system. A majority (95-101%)
of the dose was eliminated within 48 hours in animals
exposed to 4 or 6 mg/kg. Despite a marginal difference in
dose, there was a notable difference in the elimination
efficiency, particularly in the fecal elimination. Eighty
percent of the 4 mg/kg dose (5% in urine, 75% in feces)
was present in excreta at 24 hours compared to 43% of the
6 mg/kg dose (5% in urine, 38% in the feces). There was no
evidence of biliary excretion in rats receiving an oral dose
of 0.5 mg/kg suggesting it is not a prominent elimination
pathway; however, the study does not provide enough
information to determine if this behavior persists at higher
doses. The excretion profile of paraquat dichloride changed
markedly with the route of administration. After
subcutaneous injection (12.5-13.2 mg/kg), 80-98% of the
AD was identified in the urine within 24 hours of dosing.
Paraquat dichloride appears to undergo a form of
metabolism after ingestion. Thirty to forty percent of the
dose eliminated in the feces of a rat orally exposed to 0.7
mg/kg was not parent. Likewise, 1.2-2.1% of the urine
content eliminated from a rat orally exposed to 50 mg/kg
was structurally different from paraquat dichloride. The
identify of these metabolites or degradates was not
elucidated nor the metabolic pathways involved; however,
an in vitro study suggested microbial degradation
contributed to the formation of compounds in the fecal
excreta that were not identical to parent.
Non-guideline
Metabolism
Male mice and M/F
Wistar albino rats
00065592
Litchfield et al. 1973
TXR 0005824
Acceptable
50, 120, and 250 ppm paraquat
ion in the diet for 8 weeks
Audioradiography analysis indicated that paraquat
dichloride was rapidly distributed throughout most tissues
(brain and spinal cord excluded) following intravenous
administration in male mice. At 24 hours post dose,
paraquat was still observed in the lungs and in the brain and
spinal cord despite not being part of the initial distribution.
Following dietary administration, the kidneys, liver, and
lungs of male rats contained quantifiable amounts of
paraquat dichloride. Content in the brain was near or below
the detection limit regardless of dose or exposure duration.
Paraquat was not detected in any tissue after returning to
normal diet for 7 days indicating it does not accumulate in
these tissues. Data for female rats was not shown.
Page 78 of 103
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Tabic A.2.3 Special (Non-guideline) Studv Toxicity Profile - Paraquat
Guideline No./ Study
Type/Animal Species
and Strain
MRID No. or Study Authors
(year)/ Classification /Doses
Results
Non-guideline
Metabolism
Rats
Hughes etal. 1973
Acceptable
Single 15 mg/kg paraquat
diiodide dose via IP injection
<1% of the AD in the bile 24 hours. No urinary metabolites
identified suggesting lack of paraquat metabolism.
Non-guideline
Dermal absorption
(human)
00126097, 00126098,
00126099 (1982)
TXR 0053747
Acceptable/Non-guideline
99.8% radiochemical purity
Single dose of 11.8 ug
paraquat dichloride/cm2 to 6
community volunteers
In dermal absorption study with healthy adult male
volunteers, 0.23-0.3% of the applied paraquat dichloride
was absorbed through the intact skin (dosing sites were the
forearms, back of the hands, and lower legs) during the 24
hr exposure period. Differences in absorption due to
application site were noted.
Non-guideline
Acute Oral Toxicity and
Metabolism
New Zealand rabbits
49009501 (1993)
TXR 0056764
Acceptable/Non-guideline
33% paraquat ion
Acute Oral Study: Single dose
of 2, 4, 8, 12, 16, 20, 24, 30,
40, or 50 mg paraquat ion/kg
via gavage
Metabolism Study: Single
dose of 0, 2, or 30 mg paraquat
ion/kg
NOAEL = not established.
LOAEL = 30 mg paraquat ion/kg bw based on renal
damage revealed by azotemia and by microscopic
pathology findings of multifocal hydropic change in the S2
segment of the proximal tubules and additional renal
damage.
*No NOAEL is indicated because of the limited testing of
only 2 animals at all but one of the lower doses tested.
Metabolism Study: The peak concentration in blood plasma
was reached within one hour after treatment and the
concentration rapidly returned to near zero following
treatment. At the lower dose (2 mg paraquat ion/kg), 94%
of the total dose was excreted over 7 days, of which about
7% was eliminated in the urine, with 6% of the total dose
being eliminated by that route in the first 24 hours. The
remainder of the dose was excreted in the feces, with about
60% of the total dose being eliminated by that route in the
first 24 hours. While the lower dose of paraquat had no
effect on urinary output, the higher dose (30 mg paraquat
ion/kg) reduced the urine flow by about 50% over the
duration of the experiment and also produced a marked
reduction in fecal output. As a result of the reduced urine
and fecal outputs, only a small proportion of the
administered dose was eliminated by these routes during the
72 hours studied. Urine and feces only accounted for
elimination of 8% and 3% of the dose, respectively.
Page 79 of 103
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A.3 Executive Summaries
A.3.1 Studies Used for Points of Departure (POD)
Acute Dietary POD
Rat Developmental Study (MRID 0011374)
In a developmental toxicity study (MRID 00113714), paraquat dichloride (100% technical grade;
Batch # ADYM76/C; 38% w/v paraquat ion) in 0.5% aqueous Tween 80 was administered daily
via oral gavage to 29-30 presumed pregnant Alderly Park Wistar-derived (Alpk:SPF SD)
rats/group at a dose volume of 10 mL/kg at dose levels of 0, 1, 5, or 10 mg/kg/day of paraquat
ion from gestation day (GD) 6 through 15. All surviving dams were killed on GD 21. The lungs
and kidneys from at least 11 surviving dams/group were examined microscopically. The fetuses
were removed by cesarean section and examined.
At > 5 mg paraquat ion/kg/day, dams exhibited clinical signs of toxicity including subdued
nature, staining, piloerection, weight loss, hunched appearance, and respiratory distress. Clinical
signs were first observed on GD 7 and increased in prevalence (both in number of animals
affected and frequency of observation) and severity with dose and exposure duration. Body
weight gains at doses > 5 mg paraquat ion/kg/day were decreased by 37-74% during the
treatment (GD 6-16) interval (calculated by the reviewers; statistics not performed) and by 24-
29%) for the overall (GD 0-21) study (p<0.001).
A total of 13 dams across the three dose groups and the controls died or were sacrificed
moribund prior to scheduled termination. The study authors attributed the lone mortality in the
control and the two mortalities in the 1 mg paraquat ion/kg/day dose group to intubation error.
One 5 mg paraquat ion/kg/day dam had excessive blood loss from the vagina that was considered
to be treatment related and was euthanized on GD 18. The other mortality in the 5 mg paraquat
ion/kg/day dose group was attributed to intubation error. At 10 mg paraquat ion/kg/day, eight
dams died or were sacrificed moribund and an additional dam delivered prematurely on GD 21,
but was not sacrificed. Of these eight mortalities, six were attributed to the test substance and
two were attributed to intubation error.
Three dams that died or were killed in extremis in the 10 mg paraquat ion/kg/day group exhibited
clinical signs of toxicity related to treatment within one to three days of the first dose (GD 7-9)
that progressed in severity until death or sacrifice between five and seven days after the first dose
(GDI 1-13). Although these mortalities did not appear to be the result of a single dose given the
length of time between the initial dose and death, acute studies in the paraquat toxicity database
and human incidents indicate that death can be delayed up to a week after exposure to a single
oral dose of paraquat dichloride and are often preceded by clinical signs of deteriorating health.
The similarities between the three treatment-related mortalities in the 10 mg paraquat ion/kg/day
group that occurred during the first week of exposure and the pattern of delayed mortality
observed in the acute studies suggest these mortalities may have been a result of the initial dose
rather than a compounding effect from the repeated dosing. Consequently, the three mortalities
observed in 10 mg paraquat ion/kg/day group during the first week were conservatively
attributed to the initial dose and identified as an acute response to treatment. The treatment-
related mortality in 5 mg paraquat ion/kg/day and the other three treatment-related mortalities in
the 10 mg paraquat ion/kg/day group occurred more than a week after the start of the exposure
Page 80 of 103
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and thus were considered to reflect toxicity from repeat dosing rather than an acute effect. Gross
necropsy of the six dams that died or were sacrificed moribund in the 10 mg paraquat ion/kg/day
dose group indicated that the lungs were red and patchy, and microscopic examination revealed
large amount of edema fluid and polymorph infiltration in the alveoli, while the kidneys showed
widespread degenerative change in the proximal tubules.
The maternal LOAEL is 5 mg paraquat ion/kg/day based on mortality (GD18), clinical
signs of toxicity, and decreased body weight gains. The maternal NOAEL is 1 mg paraquat
ion/kg/day.
There was no effect on the proportion of dams having one or more resorptions, and there were no
treatment-related effects on sex ratio or embryonic or fetal survival. There were no increases in
fetal external visceral, or skeletal malformations or variations at any dose tested, indicating that
paraquat dichloride is not teratogenic in rats at the dose levels tested.
At > 5 mg paraquat ion/kg/day, fetal body weights were reduced by 3-6%. Skeletal ossification
was slightly retarded in these groups, as indicated by decreased ossification of the caudal
vertebrae and decreased degree of ossification in the digits in the fore- and hind-limbs. The
percent of fetuses with 7 or 8 caudal vertebrae ossified was decreased (p<0.05) at this dose (8%
treated vs 26% controls). The percent of fetuses with "good" (Grade 2) ossification in the digits
in the fore-limbs was dose-dependently decreased at 5 (29%) and 10 (23%) mg paraquat
ion/kg/day compared to controls (42%). The percent of fetuses with Grade 2 or 3 ossification in
the digits in the hind-limbs was dose-dependently decreased at >5 mg paraquat ion/kg/day (20%
each treated) compared to controls (42%). Likewise, the percent of fetuses with "poor" (Grade
5) ossification in the digits of the hindlimbs was increased at >5 mg paraquat ion/kg/day (23-
32%) compared to controls (13%). These decreases in growth and development are probably
associated with the maternal toxicity observed at this dose.
The developmental LOAEL is 5 mg paraquat ion/kg/day based on slightly decreased fetal
body weights and on delayed ossification. The developmental NOAEL is 1 mg paraquat
ion/kg/day.
This study is classified Acceptable/Guideline and satisfies the guideline requirements (OCSPP
870.3700a; OECD 414) for a developmental study in the rat.
Chronic Dietary and Incidental Oral POPs
Subchronic Dog Oral Toxicity Study (MRID 00072416)
In a subchronic toxicity study (MRID 00072416), technical grade paraquat dichloride (32.2%
w/w paraquat cation, Mond Reference No.: Y00061/009/004) was administered in the diet to 3
beagle dogs/sex/dose at nominal concentrations of 0, 7, 20, 60, or 120 ppm paraquat cation for
up to 13 weeks. Actual intakes are estimated to be 0, 0.2, 0.5, 1.5, and 3 mg/kg/day based on
Subdivision F conversion factor of 1 ppm = 0.025 mg/kg/day.
No treatment-related adverse effects were observed on ophthalmoscopic examination,
hematology, clinical chemistry, or urinalysis parameters findings, or during auscultation.
Page 81 of 103
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At 60 ppm, absolute and relative to body lung weights were increased by 39-56% in 1 dog/sex.
Alveolitis, characterized by a mixture of exudative and proliferative reactions resulting in
alveolar collapse, distortion, and interstitial hypercellularity, was observed in 5/6 dogs (vs 0
controls).
The maximum tolerated dose was exceeded at 120 ppm. Two dogs/sex were sacrificed in
extremis during the first month, suffering from marked dyspnea, harsh rales, slow and/or
irregular heartbeat, and weight loss. These two dogs lost 0.90-1.20 kg. Only 1 dog/sex survived
until terminal sacrifice. Decreased food consumption was noted in the female survivor.
Absolute and relative to body lung weights were increased, and alveolitis was observed in all 6
dogs.
The LOAEL is 60 ppm (approximately equivalent to 1.5 mg/kg/day) based on increased
lung weight and incidence of alveolitis in both sexes. The NOAEL is 20 ppm
(approximately equivalent to 0.5 mg/kg/day).
This study is classified as Acceptable/Guideline and satisfies the guideline requirement (OCSPP
870.4100b; OECD 452) for a subchronic oral toxicity study in dogs.
Chronic Dog Oral Toxicity Study (MRID 00132474)
In a chronic toxicity study (MRID 00132474), technical grade paraquat dichloride (32.3% w/w
paraquat cation, Mond Reference No.: S358/2) was administered in the diet to 6 beagle
dogs/sex/dose at nominal concentrations of 0, 15, 30, or 50 ppm (equivalent to 0/0, 0.45/0.48,
0.93/1.00, and 1.51/1.58 mg/kg/day paraquat cation in males/females) for up to 52 weeks.
No treatment-related adverse effects were observed on mortality, body weights, body weight
gains, or on ophthalmoscopic examination, hematology, clinical chemistry or urinalysis
parameters.
Increased incidences of the following clinical signs were observed at 50 ppm in both sexes:
hypernea (4/6 vs 1/6, each sex), increased vesicular sound (3-4/6 vs 0/6), and reddening of
tongues (6/6 vs 4/6, each sex). The frequency of these observations was also increased at 50
ppm. These signs were first observed at Week 13 (hypernea and increased vesicular sound) and
week 9 (tongue reddening). Food consumption was decreased in one 50 ppm dog/sex. The
hypernea was corroborated by further findings of pulmonary toxicity. The other findings are
considered equivocal.
Lungs were the target organ. Absolute and relative to body lung weight were each increased by
36%) in males and 61%> in females at 50 ppm. Chronic pneumonitis was observed in 44 of the 48
dogs that were evaluated; therefore, an increased incidence was not observed. However, an
increase in severity was observed in the 30 and 50 ppm groups; the incidence (# affected/6,
treated vs controls) of slight to marked chronic pneumonitis was 5-6 treated males vs 2 controls
and 3-6 treated females vs 1 control. This lesion correlated to yellow discoloration and
consolidation of areas of the lungs observed grossly. Additionally, the incidence and severity of
minimal to moderate focal granuloma was increased in the 30 and 50 ppm males (5/6 each
treated vs 4/6 controls). Focal pleural fibrosis was observed in 3/6 males at 50 ppm vs 2/6
controls and may have been treatment-related.
Small amounts of the paraquat cation were detected in the lungs of all treated groups (0.13-1.04
M-g/g) ar|d in the kidney of the 30 and 50 ppm groups (0.12-0.19 |ig/g).
Page 82 of 103
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The LOAEL is 30 ppm (equivalent to 0.93/1.00 mg/kg/day in males/females) based on
increased severity of chronic pneumonitis and gross lung lesions in both sexes, and focal
pulmonary granulomas in males. The NOAEL is 15 ppm (equivalent to 0.45/0.48
mg/kg/day in males/females).
At the doses tested, there was no treatment-related increase in tumor incidence when compared
to controls. Dosing was considered adequate based on an increase in pulmonary toxicity.
This study is classified as Acceptable/Guideline and satisfies the guideline requirement (OCSPP
870.4100b; OECD 452) for a chronic oral toxicity study in dogs.
Dermal POD
21-Day Rabbit Dermal Toxicity Study (MRID 00156313)
In a 21-day dermal toxicity study (MRID 00156313 [Accession # 260635]), paraquat dichloride
(43.5% w/w paraquat cation; Lot/Batch # SX-1465) in distilled water was applied directly to the
hair-clipped intact skin of 6 New Zealand white rabbits/sex/dose at dose levels of 0, 0.50, 1.15,
2.60, or 6.00 mg/kg/day paraquat cation for 6 hours/day, 7 days/week during a 21-day period.
No treatment-related effects were observed on clinical signs, body weight, body weight gain,
food consumption, on hematology or clinical chemistry parameters, or organ weights. All
animals survived until scheduled sacrifice. No evidence of systemic toxicity was noted.
At 2.60 mg paraquat ion/kg/day, small scabs were noted at the treatment site in 2 males (Days 18
and 21) and 1 female (Days 15, 18, and 21). Microscopically evidence of dermal irritation was
found in 3 males and included: epidermal erosion/ulceration, surface exudation, acanthosis,
and/or inflammation.
At 6.00 mg paraquat ion/kg/day, very slight to well-defined erythema was noted in 4-6
rabbits/sex at Days 11, 15, 18, and 21. Small scabs were found at the treated site in 1-2
rabbits/sex on Day 11 and 12/12 rabbits at Days 15, 18, and 21. Large scabs were noted in 2-3
rabbits/sex. Grossly, crusty scabs, redness, thickened appearance, and/or prominent
subcutaneous vessels were noted. Microscopically, the same lesions were observed as in the 7.8
mg/kg/day group.
The dermal LOAEL is 2.60 mg paraquat ion/kg/day, based on small scabs at the treatment
site in both sexes and epidermal erosion/ulceration, surface exudation, acanthosis, and/or
inflammation in males. The dermal NOAEL is 1.15 mg paraquat ion/kg/day.
The systemic LOAEL was not established. The systemic NOAEL is 6 mg paraquat
ion/kg/day.
This study is classified as Acceptable/Guideline and satisfies the guideline requirements
(OCSPP 870.3200; OECD 410) for a 21-day dermal toxicity study.
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Inhalation POD
21-Day Rat Inhalation Toxicity Study (MRID 00113718)
In a subchronic inhalation toxicity study (MRID 00113718), Sprague-Dawley rats were exposed
by whole body inhalation to paraquat dichloride (approximately 40% paraquat ion) administered
as a respirable (particle size < 2 (j,m) aerosol at nominal concentrations of 0, 0.01, 0.1, 0.5, or 1.0
[j,g/L paraquat ion (equivalent to analytical concentrations of 0, 0.012, 0.112, 0.487, and 1.280
[j,g/L, respectively) for 6 hours/day, 5 days/week for 3 weeks. The numbers of rats of each sex
assigned to these groups were as follows: 32 (control group); 16 (0.5 (J,g/L); and 36 (remaining
groups). Parameters examined included clinical observations, body weights, food consumption,
and water consumption. At the end of the three-week treatment period (15 total exposures), 16
rats/sex from the control group and 8 rats/sex/group from the remaining groups were terminated
and examined; 8 rats/sex/group were euthanized and examined after a two-week recovery period.
Gross and microscopic examinations were restricted to the respiratory tract (nasal passages,
pharynx, tongue, larynx, trachea, and lungs). The remaining rats (4/sex/dose) in the control,
0.01, and 0.1 [j.g/L groups were euthanized after the 5th exposure, the 15th exposure, and 1, 2, and
3 days after the 15th exposure for paraquat estimations
There were no treatment-related effects on body weights, food consumption, water consumption,
or gross pathology at any concentration.
The 1.0 [j,g/L group was not exposed after Day 1 because 28/36 males (78%) and 29/36 females
(80%>) died from respiratory failure in the subsequent 14 days.
All rats in the 0.1 [j,g/L group exhibited nasal discharge and squamous keratinizing metaplasia,
and/or hyperplasia of the epithelium of the larynx. The changes in the epithelium were still
observed in 11/16 (69%>) of the rats euthanized at the end of the recovery period.
Additionally, in the 0.5 [j,g/L group, the following findings were observed after 3 weeks: (i)
extensive ulceration, necrosis, inflammation and squamous keratinizing metaplasia, and
marked/moderate hyperplasia of adjacent epithelia in larynx of all rats; and (ii) aggregations of
foamy macrophages in the bronchioles or alveoli, hypertrophy of the epithelium and thickened
alveolar walls in the lungs of most or all rats. After the 2-week recovery period, no ulceration or
necrosis was observed in the larynx, but changes in the lungs were still seen. In addition,
disruption of bronchi olar epithelium, adjacent to the macrophage aggregation, was noted.
At 0.01 |ig/L, there were no treatment-related effects on any parameter.
The LOAEL is 0.10 jig/L based on squamous keratinizing metaplasia and hyperplasia of
the epithelium of the larynx. The NOAEL is 0.01 jig/L.
At the request of the Agency, this study was conducted for a duration of three weeks, instead of
the 90 days required by Guideline OPPTS 870.3465. Aside from the different study duration,
this study was conducted in accordance with Guideline OPPTS 870.3465.
This 21-day inhalation toxicity study is classified as acceptable/guideline and satisfies the
guideline requirement (OPPTS 870.3465; OECD 413) for a subchronic inhalation study in the
rat.
Page 84 of 103
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A.3.2 Other Studies Updated for Registration Review
Acute Neurotoxicity Study (MRID 47994201)
In an acute neurotoxicity study (MRID 47994201), groups of fasted 42 day-old Alpk:ApfSD rats
10/sex/dose were given a single oral dose of paraquat technical (33.4% w/w paraquat ion, 46.1%
w/w paraquat dichloride, preparation P47) in deionized water orally (by gavage) at 10 mL/kg at
doses of 0, 25, 75, or 250 mg/kg paraquat technical/kg body weight. This corresponded to doses
of 0, 8.4, 25.1, and 84 mg paraquat ion/kg. Animals were observed for 14 days after dosing.
Neurobehavioral assessment (functional observational battery and motor activity testing) was
performed in 10/sex/group one week prior to dose administration, at approximately 2 hours after
dose administration on Day 1, and at one week (Day 8) and two weeks (Day 15). At study
termination, 5/sex/group were euthanized and perfused in situ for neuropathological
examination. Of the perfused animals, 5/sex/group of control and 84 mg paraquat ion/kg animals
were subjected to histopathological evaluation of brain and peripheral nervous system tissues.
No effects of the test chemical were observed in the functional observational battery (FOB), or
on motor activity and nervous system histopathology.
One 84 mg paraquat ion/kg male dosed with paraquat technical was found dead on Day 5. This
male had shown a slightly reduced foot splay reflex on Days 1-4 with piloerection and "sides
pinched in" on Day 4. One 84 mg paraquat ion/kg female was killed on Day 4, due to adverse
clinical signs of irregular breathing (indicative of respiratory distress), flaccidity, "sides pinched
in", and upward spinal curvature from Days 2-4, and piloerection and ocular discharge on Days
3-4. The clinical signs preceding death in these two animals were consistent with an agonal
response to treatment and were not considered evidence of neurotoxicity. The lack of significant
findings in the FOB, motor activity, and neuropathology assessments further supports this
conclusion. Similar clinical signs were not observed in the other animals from this treatment
group nor the other treatment or control groups. All other animals survived to scheduled
sacrifice.
The LOAEL for neurotoxicity was not observed. The NOAEL is 84 mg paraquat ion/kg
(250 mg/kg paraquat technical).
The systemic LOAEL is 84 mg paraquat ion/kg (250 mg/kg paraquat technical) based on
clinical signs and mortality in males and females. The NOAEL is 25.1 mg paraquat ion/kg
(75 mg/kg paraquat technical).
This neurotoxicity study is classified as Acceptable/Guideline and satisfies the guideline
requirement for an acute neurotoxicity study in rats (OCSPP 870.6200a; OECD 424).
Page 85 of 103
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A.4 Paraquat General Literature Review Results
Paraquat Search
Date and Time of Search: 01/29/2018; 8:00 am
Search Details:
((Paraquat) AND (rat OR mouse OR dog OR rabbit OR monkey OR mammal))
Studies Identified in PubMed*: 3974
SWIFT-Review** Tags:
2517 for Animal
2343 for Human (1454 studies tagged as "Human" were not included in the "Animal" tag)
0 for NO TAG
Paraquat Dichloride Search
Date and Time of Search: 01/29/2018; 8:00 am
Search Details:
((Paraquat dichloride)) AND (rat OR mouse OR dog OR rabbit OR monkey OR mammal))
Studies Identified in PubMed*: 132
SWIFT-Review** Tags:
99 for Animal
67 for Human (33 studies tagged as "Human" were not included in the "Animal" tag)
0 for NO TAG
All studies identified in the PubMed search were screened when the citation list was <100.
Screening of larger citations lists (>100 citations) was conducted after prioritization in SWIFT-
Review and focused on studies identified with the "Animal" and/or "Human" tag.
After screening both citation lists, it was determined that all 132 publications identified in the
paraquat dichloride search were captured in the paraquat search. An additional 17 relevant
animal studies were identified in a separate systematic review that focused on Parkinson's
disease (D449106; TXR 0057888 A. Wray, 06/26/2019) and were included in the general
literature review.
Number of Articles Identified as Relevant for Risk Assessment: 26
Citations of Articles Identified as Relevant for Risk Assessment:
1. Anderson D, McGregor DB, and Purchase IFH. 1976. Dominant lethal studies with
paraquat and diquat in male CD-I mice. Mutat Res. 40: 349-358.
2. Anselmi L, Bove C, Coleman FH, Le K, Subramanian MP, Venkiteswaran K,
Subramanian T, and Travagli RA. 2018. Ingestion of subthreshold doses of environmental
toxins induces ascending Parkinsonism in the rat. npj Parkinson's Disease. 4(30): 1-10.
3. Benzi G, Marzatico F, Pastoris O, and Villa RF. 1990. JNeurosci Res. 26(1): 120-128.
Page 86 of 103
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4. Caroleo M, Rispoli V, Arbitrio M, Strongoli C, Rainaldi G, Rotiroti D, and Nistico G.
1996. Chronic administration of paraquat produces immunosuppression of T lymphocytes
and astrocytosis in rats. Tox SubstMech. 15: 183-194.
5. Chen Q, Niu Y, Zhang R, Guo H, Gao Y, Li Y, and Liu R. 2010. The toxic influence of
paraquat on hippocampus of mice: Involvement of oxidative stress. Neurotoxicology.
31(3): 310-316.
6. Chen Q, Zhang X, Zhao JY, Lu XN, Zheng PS, and Xue X. 2017. Oxidative damage of
the male reproductive system induced by paraquat. JBiochem Mol Toxicol. 31(3):e21870.
7. Clark DG, McElligott TF, and Hurst EW. 1966. The toxicity of paraquat. Brit J Industry
Med. 23: 126-132.
8. Endo T, Hara S, Kano S, and Kuriiwa F. 1998. Effects of a paraquat-containing herbicide,
Gramoxon, on the central monoamines and acetylcholine in mice. Res Commun Psych
Psy. 13 (4): 261-270.
9. Fredriksson A, Fredriksson M, and Eriksson P. 1993. Neonatal exposure to paraquat or
MPTP induces permanent changes in striatum dopamine and behavior in adult mice.
ToxicolApplPharmacol. 122(2): 258-264.
10. Gorkin V, Amanov K, Mamadiev M, Medevdev A, and Khuzhamberdiev M. 1993. The
biochemical mechanisms of the toxic effects of some pyridine derivatives. 1. Study on the
deamination of biogenic amines and other nitrogenous compounds in paraquat
intoxication. Arch Environ Contam Toxicol. 26(4): 534-539.
11. Hassuneh MR, Albini MA, and Talib WH. 2012. Immunotoxicity induced by acute
subtoxic doses of paraquat herbicide: Implication of shifiting cytokine gene expression
toward T-helper (Th)-17 phenotype. Chem Res Toxicol. 25: 2112-2116.
12. Li HF, Zhao SX, Xing BP, and Sun ML. 2015. Ulinastatin suppresses endoplasmic
reticulum stress and apoptosis in the hippocampus of rats with acute paraquat poisoning.
Neural Regen Res. 10:467-472.
13. Lou D, Wang Q, Huang M, and Zhou Z. 2016. Does age matter? Comparison of
neurobehavioral effects of paraquat exposure on postnatal and adult C57BL/6 mice.
Toxicol Mech Method. 26(9): 667-673.
14. Luty S, Latuszynska J, Halliop J, Tochman A, Obuchowska D, Korczak B, Przylepa E,
and Bychawski E. 1997. Dermal toxicity of paraquat. Ann Agric Envron Med. 4(2): 217-
227.
15. McElligott TF. 1972. The dermal toxicity of paraquat: Differences due to techniques of
application. Toxicol Appl Pharmacol. 21: 361-368.
16. Minnema DJ, Travis KZ, Breckenridge CB, Sturgess NC, Butt M, Wolf JC, Zadory D,
Beck MJ, Mathews JM, Tisdel MO, Cook AR, Botham PA, and Smith LL. 2014. Dietary
administration of paraquat for 13 weeks does not result in a loss of dopaminergic neurons
in the substantia nigra of C57BL/6J mice. Regul ToxicolPharm. 68(2): 250-258.
17. Naudet N, Antier E, Gaillard D, Morignat E, Lakhdar L, Baron T, and Bencsik A. 2017.
Oral exposure to paraquat triggers earlier expression of phosphorylated a-synuclein in the
Page 87 of 103
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enteric nervous system of A53T mutant human a-synuclein transgenic mice. J
NeuropatholExp Neurol. 76(12): 1046-1057.
18. Okabe M, Nishimoto S, Sugahara T, Akiyama K, and Kakinuma Y. 2010. Oral
administration of paraquat perturbs immunoglobulin productivity in mouse. J Toxicol Sci.
35(2): 257-263.
19. Peled-Kamar M, Lotem J, Wirguin I, Weiner L, Hermalin A, and Groner Y. 1997.
Oxidative stress mediates impairment of muscle function in transgenic mice with elevated
level of wild-type Cu/Zn superoxide dismutase. Proc Natl Acad Sci. 94(8): 3883-3887.
20. Prasad K, Tarasewicz E, Mathew J, Strickland PA, Buckley B, Richardson JR, and
Richfield EK. 2009. Toxicokinetics and toxicodynamics of paraquat accumulation in the
mouse brain. Exp Neurol. 215(2): 358-367.
21. Prasad K, Winnik B, Thiruchelvam MJ, Buckley B, Mirochnitchenko O, and Richfield
EK. 2007. Prolonged toxicokinetics and toxicodynamics of paraquat in mouse brain.
Environ Health Persp. 115(10): 1448-1453.
22. Ren JP, Zhao YW, and Sun XJ. 2009. Toxic influence of chronic oral administration of
paraquat on nigrostriatal dopaminergic neurons in C57BL/6 mice. Chin Med J. 122(19):
2366-2371.
23. Rojo AI, Cavada C, de Sagarra MR, and Cuadrado A. 2007. Chronic inhalation of
rotenone or paraquat does not induce Parkinson's disease symptoms in mice or rats. Exp
Neurol. 208(1): 120-126.
24. Salovsky P and Shopova V. 1993. Synergic lung changes in rats receiving combined
exposure to paraquat and ionizing radiation. Environ Res. 60:44-54.
25. Satpute RM, Pawar PP, Puttewar S, Sawale SD, and Ambhore PD. 2017. Effect of
resveratrol and tetracycline on the subacute paraquat toxicity in mice. Hum Exp Toxicol.
36(12): 1303-1314.
26. Widdowson PS, Farnworth MJ, Upton R, and Simpson MG. 1996. No changes in
behavior, nigro-striatal system neurochemistry or neuronal cell death following toxic
multiple oral paraquat administration to rats. Hum Exp Toxicol. 15(7): 583-591.
Conclusion of Literature Search: Full text review of the 26 relevant studies pared down the list
to 10 studies (Widdowson et al. 1996; Rojo et al. 2007; Ren etal. 2009; Satpute et al. 2017;
Naudet et al. 2017; Endo et al. 1988; Minnema et al. 2014; Prasad et al. 2007; Lou et al. 2016;
Chen et al. 2017) that were of sufficient quality and contained either quantitative or qualitative
information relevant to the risk assessment. Only one study, Lou et al. 2016, reported evidence
of adverse health effects in mice at doses that were similar to the current PODs. This study was
formally reviewed (MRID 50733301; TXR 0057886) and was considered in POD selection. The
data reported in the other nine publications did not have a quantitative impact on the risk
assessment; however, the studies did report novel findings, including toxicokinetic and
neurotoxicity information, that were incorporated into the hazard characterization of the
Registration Review risk assessment.
*PubMed is a freely available search engine that provides access to life science and biomedical
references predominantly using the MEDLINE database.
Page 88 of 103
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**SWIFT-Review is a freely available software tool created by Sciome LLC that assists with
literature prioritization. SWIFT-Review was used to prioritize citations lists that were larger than
100. Studies identified in the PubMed search were tagged and grouped based on the model of
interest in the study (e.g. human, animal, in vitro, etc.).
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Appendix B: Physicochemical Properties of Paraquat Dichloride
Tabic B.l. Physicochemical Properties of Technical Grade Paraquat Dichloride
Parameter
Value
Reference
Melting point/range
decomposes at ca. 340 °C
Product Chemistry Chapter
of the Paraquat Dichloride
Update, 10/10/1991
pH
6.4 at 20 °C
Density
1.5 g/cm3 at 25 °C
Water solubility (20 °C)
freely soluble in water:
618-620 g/L atpH 5.2, 7.2, and 9.2
Solvent solubility (20 °C)
<0.1 g/L in acetone, dichloromethane,
toluene, ethyl acetate, and hexane;
143 g/L in methanol
Vapor pressure
«10"8 kPa at 25 °C
Octanol/water partition coefficient,
Log(Kow)
logK0w = -4.5 at 20 °C
UV/visible absorption spectrum
Not available
Page 90 of 103
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Appendix C: International Residue Limit Status Sheet
Paraquat Dichloride (061601; 06/13/2018)
Tabic C.l. Summary of US and International Tolerances and Maximum Residue Limits
Residue Definition:
US
Canada
Codex3
40 CFR 180.205:
Tolerances are established for residues of Daraciuat. including its
metabolites and degradates, in or on the commodities in the table below.
Compliance with the tolerance levels specified below is to be determined
by measuring only paraquat dichloride and calculated as the paraquat
cation
Paraquat: 1,1'-
dimethyl-4,4'-
bipyridinium
Paraquat
cation
Commodity1
Tolerance (ppm) /Maximum Residue Limit (mg/kg)
US
Canada
Codex
Acerola
0.05
—
—
Almond, hulls
0.50
0.01
Animal feed, nongrass, group 18, forage
75
—
—
Animal feed, nongrass, group 18, hay
200
—
—
Artichoke, globe
0.05
0.05
Atemoya
0.05
—
0.01
Avocado
0.05
—
0.01
Banana
0.05
—
0.01
Barley, grain
0.05
0.05
—
Barley, hay
3.5
—
—
Barley, straw
1.0
—
—
Beet, sugar, roots
0.50
—
0.05
Beet, sugar, tops
0.05
—
—
Berry and small fruit, group 13-07
0.05
0.05 individual
0.01
Biribi
0.05
—
Cacao, dried bean
0.05
—
Canistel
0.05
0.01
Carrot, roots
0.05
0.05
0.05
Cattle, fat
0.05
0.05
Cattle, kidney
0.50
—
Cattle, meat
0.05
0.005
Cattle, meat byproducts, except kidney
0.05
—
Cherimoya
0.05
0.01
Coffee, green bean
0.05
—
Corn, field, forage
3.0
—
Corn, field, grain
0.10
0.1
0.03 maize
0.05 flour
Corn, field, stover
10
10
Corn, pop, grain
0.10
0.1
0.03
Corn, pop, stover
10
—
Corn, sweet, kernel plus cob with husks removed
0.05
0.05
0.03
Cotton, gin byproducts
100
—
Cotton, undelinted seed
3.5
2
Cowpea, forage
0.10
—
Cowpea, hay
0.40
—
Cranberry
0.05
0.01
Custard apple
0.05
0.01
Egg
0.01
0.005
Endive
0.07
0.07
Feijoa
0.05
0.01
Fig
0.05
0.01
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Tabic C.l. Summary of US and International Tolerances and Maximum Residue Limits
Residue Definition:
US
Canada
Codex3
Fruit, citrus, group 10-10
0.05
0.02
Fruit, pome, group 11-10
0.05
0.05 individual
0.01
Fruit, stone, group 12-12
0.05
0.05 individual
0.01
Goat, fat
0.05
0.05
Goat, kidney
0.50
—
Goat, meat
0.05
0.005
Goat, meat byproducts, except kidney
0.05
—
Grain, aspirated fractions
70
—
Grape
0.05
0.01
Grass, forage
90
—
Grass, hay
40
—
Guar, seed
0.50
0.5
Guava
0.05
0.01
Hog, fat
0.05
0.05
Hog, kidney
0.50
—
Hog, meat
0.05
0.005
Hog, meat byproducts, except kidney
0.05
—
Hop, dried cones
0.50
0.10
Horse, fat
0.05
0.05
Horse, kidney
0.50
—
Horse, meat
0.05
0.005
Horse, meat byproducts, except kidney
0.05
—
llama
0.05
0.01
Jaboticaba
0.05
—
Kiwifruit
0.05
0.01
Lentil, seed
0.50
0.5
Lettuce
0.05
0.07
Longan
0.05
0.01
Lychee
0.05
—
Mango
0.05
0.01
Milk
0.01
0.005
Nut, tree, group 14-12
0.05
0.05
Okra
0.05
0.05
Olive
0.10
0.10
Onion, bulb, subgroup 3-07A
0.10
0.1
—
Onion, green, subgroup 3-07B
0.05
0.05
—
Papaya
0.05
0.01
Passionfruit
0.20
0.01
Pawpaw
0.05
0.01
Vegetable, legume, edible podded, subgroup 6A
0.05
0.05 individual
0.5
Pea and bean, succulent shelled, subgroup 6B
0.05
0.05 individual
0.5
Pea and bean, dried shelled, except soybean,
subgroup 6C
0.50
0.5
Pea, field, hay
0.80
—
Pea, field, vines
0.20
—
Peanut
0.05
—
Peanut, hay
0.50
—
Peppermint, fresh leaves
0.50
—
Persimmon
0.05
0.01
Pineapple
0.05
0.01
Pineapple, process residue
0.30
—
Pistachio
0.05
0.05
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Tabic C.l. Summary of US and International Tolerances and Maximum Residue Limits
Residue Definition:
US
Canada
Codex3
Pomegranate
0.05
0.01
Pulasan
0.05
0.01
Rambutan
0.05
0.01
Rhubarb
0.05
—
Rice, grain
0.05
0.05
Safflower, seed
0.05
—
Sapodilla
0.05
0.01
Sapote, black
0.05
0.01
Sapote, mamey
0.05
0.01
Sapote, white
0.05
0.01
Sheep, fat
0.05
0.05
Sheep, kidney
0.50
—
Sheep, meat
0.05
0.005
Sheep, meat byproducts, except kidney
0.05
—
Sorghum, forage, forage
0.10
—
Sorghum, grain, forage
0.10
—
Sorghum, grain, grain
0.05
0.03
Soursop
0.05
0.01
Soybean, forage
0.40
—
Soybean, hay
10
—
Soybean, hulls
4.5
—
Soybean, seed
0.70
0.5
Spanish lime
0.05
0.01
Spearmint, fresh leaves
0.50
—
Star apple
0.05
0.01
Starfruit
0.05
—
Strawberry
0.30
0.01
Sugar apple
0.05
0.01
Sugarcane, cane
0.50
—
Sugarcane, molasses
3.0
—
Sunflower, seed
2.0
2
Turnip, roots
0.05
0.05
Vegetable, Head and Stem Brassica, Group 5-16
0.07
0.07
Brassica leafy greens subgroup 4-16B
0.07
0.07
Stalk and Stem Vegetable Subgroup 22A
0.05
Vegetable, cucurbit, group 9
0.05
0.02
Vegetable, fruiting, group 8-10
0.05
0.05
Vegetable, tuberous and corm, subgroup 1C
0.50
0.05
Wax jambu
0.05
—
Wheat, forage
0.50
—
Wheat, grain
1.1
—
Wheat, hay
3.5
—
Wheat, straw
50
—
Completed: T. Morton; 05/30/2018
1 Includes only commodities of interest for this action.
2Mexico adopts US tolerances and/or Codex MRLs for its export purposes.
Page 93 of 103
-------
Appendix D. Summary of Paraquat Occupational Handler Exposure and Risk Estimates
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
1\ posu IV
Scena rio
Dermal In it
1,1'Vl'l of
1'1'li or
Engineering
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
Level of
1'1'li or
Engineering
control
Maximum
Area
Treated
or
Amount
Handled
Dailv4
Dermal
L<)( = 100
Inhalation
L()C= 100
Crop or Target
Exposure'
(|ig/l l> :ii)
Application
Rate'
Dose5
(ing/kg/day)
MOE"
Dose7
(mg/kg/day)
MOE8
Mixer/Loader
37.6
SL/G
0.0219
APF10R
0.000283
21000
0.000000164
16000
All Use Sites
29.1
DL/G
0.015
lb ai/gallon
0.000219
27000
Liquid,
Backpack,
Broadcast
8.6
EC
0.083
EC
40
0.0000645
93000
0.000000623
4200
37.6
SL/G
0.0219
APF10R
gallons
0.000358
17000
0.000000208
13000
Pastureland
29.1
DL/G
0.019
lb ai/gallon
0.000276
22000
8.6
EC
0.083
EC
0.0000818
73000
0.000000789
3300
37.6
SL/G
0.0219
APF10R
0.00705
850
0.00000411
630
All Use Sites
29.1
DL/G
0.015
lb ai/gallon
0.00546
1100
Liquid,
Mechanically-
pressurized
Handgun,
Broadcast
8.6
EC
0.083
EC
1000
gallons
0.00161
3700
0.0000156
170
37.6
SL/G
0.0219
APF10R
0.00893
670
0.0000052
500
Pastureland
29.1
DL/G
0.019
lb ai/gallon
0.00691
870
8.6
EC
0.083
EC
0.00204
2900
0.0000198
130
Nursery (ornamentals,
vegetables, trees, container
stock)
37.6
SL/G
0.0219
APF10R
0.0283
210
0.0000164
160
29.1
DL/G
1.0
lb ai/A
60 A
0.0219
270
Liquid, Aerial
8.6
EC
0.083
EC
0.00645
930
0.0000623
42
Field crop, typical: Asparagus;
Brassica (head and stem)
Vegetables; Carrots (Including
37.6
SL/G
0.0219
APF10R
1.0
lb ai/A
350 A
0.165
36
0.0000959
27
Page 94 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
1\ posu IV
Scrim i'i<>
Dcrniiil In it
1,1'Vl'l of
1'1'li or
Engineering
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
Miiximum
A reii
Trented
or
Amount
I In ml led
Dnilv4
Dcrniiil
LOC= 100
Inhiiliition
L<)('= 100
( j'op or Tiirget
Exposure'
(fig/lb :ii)
Application
Riite'
Dose5
(mg/kg/diiv)
MOE"
Dose7
(nig/kg/diiv)
MOE8
Tops); Corn, Sweet; Cucurbit;
Vegetables; Eggplant; Fruiting
Vegetables; Leafy Vegetables;
Lettuce; Melons; Peas
29.1
DL/G
0.128
47
(Unspecified); Pepper; Sugar
Beet; Tomato; Turnip Greens
8.6
EC
0.083
EC
0.0376
160
0.000364
7.1
Orchard/Vineyard; Almond
37.6
SL/G
0.0219
APF10R
0.131
46
0.0000766
34
Field crop, typical: Legume
Vegetables; Sage, Clary
29.1
DL/G
0.80
lb ai/A
350 A
0.102
59
8.6
EC
0.083
EC
0.0301
200
0.00029
9
Field crop, typical: Lentils; Peas,
Dried Type; Tuberous and Corm
Vegetables;
37.6
SL/G
0.0823
73
29.1
DL/G
0.0219
APF10R
0.50
lb ai/A
350 A
0.0636
94
0.0000479
54
Orchard/Vineyard; Grapes
8.6
EC
0.083
EC
0.0189
320
0.000181
14
37.6
SL/G
0.0219
APF10R
0.0494
120
0.0000288
90
Field crop, typical: Root and
Tuber Vegetables
29.1
DL/G
0.30
lb ai/A
350 A
0.0383
160
8.6
EC
0.083
EC
0.0113
530
0.000109
24
37.6
SL/G
0.0219
APF10R
0.846
7.1
0.000493
5.3
Field crop, high acreage:
Alfalfa; Clover
29.1
DL/G
1.5
lb ai/A
1200 A
0.655
9.2
8.6
EC
0.083
EC
0.194
31
0.00186
1.4
Field crop, high-acreage; Barley;
Beans, Dried-Type; Corn, Field;
Corn, Pop; Cotton;
Deciduous/Broadleaf/Hardwood;
Fallowland; Forestry; Grasses
Grown for Seed; Mint;
Nonagricultural Areas;
Pastureland/Rangeland; Peas
(Unspecified); Potato,
White/Irish (or Unspecified);
37.6
SL/G
1.0
lb ai/A
0.564
11
29.1
DL/G
0.0219
APF10R
1200 A
0.436
14
0.000329
7.9
Page 95 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
1\ posu IV
Scrim i'i<>
Dcrmiil In it
1,1'Vl'l of
1'1'li or
En ginee ring
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
M ii xi ill u ill
A reii
Trented
or
Amount
I In ml led
Diiilv4
Dcrniiil
LOC= 100
Inhiiliition
L<)('= 100
( j'op or Tiirget
Exposure'
(fig/lb :ii)
Application
Riite'
Dose5
(mg/kg/diiv)
MOE"
Dose7
(mg/kg/diiv)
MOE8
Rice; Root and Tuber
Vegetables; Safflower;
Sorghum; Soybeans; Sugarcane;
Sunflower; Tuberous and Corm
Vegetables; Wheat
8.6
EC
0.083
EC
0.129
47
0.00125
2.1
37.6
SL/G
0.0219
APF10R
0.451
13
0.000263
9.9
Field crop, high acreage:
Legume Vegetables
29.1
DL/G
0.80
lb ai/A
1200 A
0.349
17
8.6
EC
0.083
EC
0.103
58
0.000996
2.6
37.6
SL/G
0.0219
APF10R
0.283
21
0.000164
16
Field crop, high acreage: Peas,
Dried-Type
29.1
DL/G
0.50
lb ai/A
1200 A
0.219
27
8.6
EC
0.083
EC
0.0645
93
0.000623
4.2
Nursery (ornamentals,
vegetables, trees, container
stock)
37.6
SL/G
0.0219
APF10R
0.0283
210
0.0000164
160
29.1
DL/G
1.0
lb ai/A
60 A
0.0219
270
8.6
EC
0.083
EC
0.00645
930
0.0000623
42
Orchard/Vineyard: Arecola
(West Indies Cherry); Apple;
Apricot: Avocado; Banana;
Bushberries; Caneberries;
Citrus; Cocoa; Coffee; Fig;
Grapes; Guava; Kiwi; Nectarine;
Olive; Papaya; Passion Fruit
(Granadilla); Peach; Pear;
Persimmon; Pistachio; Plum;
Prune; Subtropical/Tropical
Fruit; Tree Nuts
37.6
SL/G
0.0219
APF10R
0.0188
320
0.000011
240
Liquid,
Groundboom
29.1
DL/G
1.0
lb ai/A
40 A
0.0145
410
8.6
EC
0.083
EC
0.0043
1400
0.0000415
63
Orchard/Vineyard: Macadamia
Nut (Bushnut)
37.6
SL/G
0.0219
APF10R
0.50
lb ai/A
0.0094
640
0.00000548
470
29.1
DL/G
40 A
0.00728
820
8.6
EC
0.083
EC
0.00215
2800
0.0000208
130
Page 96 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk Estimates for Paraquat
1\ posu IV
Scrim i'i<>
( j'op or Tiirget
Dcrniiil In it
Exposure'
(fig/lb :ii)
1,1'Vl'l of
1'1'li or
Engineering
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
Miiximum
Application
Riitc'
A reii
Trented
or
Amount
I In ml led
Diiilv4
Dcrniiil
LOC= 100
Inhiiliition
L<)('= 100
Dose5
(mg/kg/diiv)
MOE"
Dose7
(nig/kg/diiv)
MOE8
Field crop, typical: Artichoke;
Asparagus; Brassica (head and
stem) Vegetables; Carrots
(Including Tops); Corn, Sweet;
Cucurbit Vegetables; Eggplant;
Flowering Plants; Fruiting
Vegetables; Garlic; Ginger;
Leafy Vegetables; Lettuce;
Manioc (Cassava); Melons;
Okra; Onions; Peas
(Unspecified); Pepper;
Pineapple; Root and Tuber
Vegetables; Rhubarb; Sugar
Beet; Tomato; Turnip Greens;
Yam
37.6
SL/G
0.0219
APF10R
1.0
lb ai/A
80 A
0.0376
160
0.0000219
120
29.1
DL/G
0.0291
210
8.6
EC
0.083
EC
0.0086
700
0.000083
31
Field crop, typical: Tobacco
37.6
SL/G
0.0219
APF10R
0.94
lb ai/A
80 A
0.0354
170
0.0000206
130
29.1
DL/G
0.0274
220
8.6
EC
0.083
EC
0.00809
740
0.000078
33
Field crop, typical: Legume
Vegetables; Sage, Clary; Taro;
Vegetables (Unspecified)
37.6
SL/G
0.0219
APF10R
0.80
lb ai/A
80 A
0.0301
200
0.0000175
150
29.1
DL/G
0.0233
260
8.6
EC
0.083
EC
0.00688
870
0.0000664
39
Field crop, typical: Guar;
Lentils; Peas, Dried Type; Peas,
Pigeon; Strawberry; Tuberous
and Corm Vegetables;
37.6
SL/G
0.0219
APF10R
0.50
lb ai/A
80 A
0.0188
320
0.000011
240
29.1
DL/G
0.0145
410
8.6
EC
0.083
EC
0.0043
1400
0.0000415
63
Field crop, high acreage:
Alfalfa; Clover
37.6
SL/G
0.0219
APF10R
1.5
lb ai/A
200 A
0.141
43
0.0000821
32
29.1
DL/G
0.109
55
8.6
EC
0.083
EC
0.0323
190
0.000311
8.4
Page 97 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
l.xposu IV
Seeiui rio
Dernuil Iinit
Level of
1'1'U or
Engineering
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
Miiximum
A reii
Trented
or
Amount
Mil ml led
Diiilv4
Derniiil
LOC= 100
Inhiiliition
L<)('= 100
Crop or Tiirget
Exposure1
(fig/lb :ii)
Application
Riite'
Dose5
(ing/kg/diiv)
MOli"
Dose7
(nig/kg/diiv)
MOli8
Field crop, high acreage:
Barley;
37.6
SL/G
0.0219
APF10R
0.094
64
0.0000548
47
Coniferous/Evergreen/Softwood
(non-food); Corn, Field; Corn,
Pop; Cotton; Fallowland;
Peanuts; Peas (Unspecified);
Rice; Safflower; Sorghum;
Soybean; Sugarcane; Sunflower;
Tyfon; Wheat
29.1
DL/G
1.0
200 A
0.0728
82
8.6
EC
0.083
EC
lb ai/A
0.0215
280
0.000208
13
37.6
SL/G
0.0219
APF10R
0.0753
80
0.0000438
59
Field crop, high acreage:
Legume Vegetables; Mint
29.1
DL/G
0.80
lb ai/A
200 A
0.0583
100
8.6
EC
0.083
EC
0.0173
350
0.000166
16
Field crop, high acreage:
Grasses Grown for Seed; Potato,
White/Irish (or Unspecified)
37.6
SL/G
0.0219
APF10R
0.0564
110
0.0000329
79
29.1
DL/G
0.60
lb ai/A
200 A
0.0436
140
8.6
EC
0.083
EC
0.0129
470
0.000125
21
Field crop, high acreage: Beans,
Dried-Type; Hops; Pastureland;
Peas, Dried-Type; Peas, Pigeon;
37.6
SL/G
0.0219
APF10R
0.047
130
0.0000274
95
29.1
DL/G
0.50
lb ai/A
200 A
0.0364
160
Tuberous and Corm Vegetables
8.6
EC
0.083
EC
0.0108
560
0.000104
25
37.6
SL/G
0.0219
APF10R
0.047
130
0.0000164
160
Field crop, high acreage: Root
and Tuber Vegetables
29.1
DL/G
0.30
lb ai/A
200 A
0.0219
270
8.6
EC
0.083
EC
0.00645
930
0.0000623
42
Applicator
Spray
(all starting
formulations),
Aerial
Field crop, typical: Asparagus;
Brassica (head and stem)
Vegetables; Carrots (Including
Tops); Corn, Sweet; Cucurbit;
Vegetables; Eggplant; Fruiting
Vegetables; Leafy Vegetables;
2.08
EC
0.0049
EC
1.0
lb ai/A
350 A
0.0091
660
0.0000215
120
Page 98 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk Estimates for Paraquat
Exposu re
Sceiui rio
Crop or Tiirget
Dernuil Iinit
Exposure1
(fig/lb :ii)
Level of
1'1'E or
Engineering
control2
Inhsilsition
Unit
Exposure1
0ig/lb iii)
Level of
l'l'Eor
Engineering
control
Miiximum
Application
Riite'
A mi
Trented
or
Amount
I In ml led
Diiilv4
Derniiil
LOC= 100
Inhiiliition
L<)('= 100
Dose5
(mg/kg/diiv)
MOl!'
Dose7
(mg/kg/diiv)
MOli8
Lettuce; Melons; Peas
(Unspecified); Pepper; Sugar
Beet; Tomato; Turnip Greens
Orchard/Vineyard; Almond
Field crop, typical: Legume
Vegetables; Sage, Clary
2.08
EC
0.0049
EC
0.80
lb ai/A
350 A
0.00728
820
0.0000171
150
Field crop, typical: Lentils; Peas,
Dried Type; Tuberous and Corm
Vegetables;
Orchard/Vineyard; Grapes
2.08
EC
0.0049
EC
0.50
lb ai/A
350 A
0.00455
1300
0.0000107
240
Field crop, typical: Root and
Tuber Vegetables
2.08
EC
0.0049
EC
0.30
lb ai/A
250 A
0.00195
3100
0.0000046
570
Field crop, high acreage:
Alfalfa; Clover
2.08
EC
0.0049
EC
1.5
lb ai/A
1200 A
0.0468
130
0.00011
24
Field crop, high-acreage; Barley;
Beans, Dried-Type; Corn, Field;
Corn, Pop; Cotton;
Deciduous/Broadleaf/Hardwood;
Fallowland; Forestry; Grasses
Grown for Seed; Mint;
Nonagricultural Areas;
Pastureland/Rangeland; Peas
(Unspecified); Potato,
White/Irish (or Unspecified);
Rice; Root and Tuber
Vegetables; Safflower;
Sorghum; Soybeans; Sugarcane;
Sunflower; Tuberous and Corm
Vegetables; Wheat
2.08
EC
0.0049
EC
1.0
lb ai/A
1200 A
0.0313
190
0.0000735
35
Field crop, high acreage:
Legume Vegetables
2.08
EC
0.0049
EC
0.80
lb ai/A
1200 A
0.025
240
0.0000588
44
Field crop, high acreage: Peas,
Dried-Type
2.08
EC
0.0049
EC
0.50
lb ai/A
1200 A
0.0156
380
0.0000368
71
Spray
(all starting
formulations),
Groundboom
Nursery (ornamentals,
vegetables, trees, container
stock)
5.1
EC
0.043
EC
1.0
lb ai/A
60 A
0.00383
1600
0.0000323
80
Orchard/Vineyard: Arecola
(West Indies Cherry); Apple;
Apricot: Avocado; Banana;
Bushberries; Caneberries;
Citrus; Cocoa; Coffee; Fig;
Grapes; Guava; Kiwi; Nectarine;
5.1
EC
0.043
EC
1.0
lb ai/A
40 A
0.00255
2400
0.0000215
120
Page 99 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
l.xposu IV
Seeiui rio
Dernuil Iinit
Level of
1'1'U or
Engineering
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
Miiximum
A reii
Trented
or
Amount
Mil ml led
Diiilv4
Derniiil
LOC= 100
Inhiiliition
L<)('= 100
Crop or Tiirget
Exposure1
(fig/lb :ii)
Application
Riite'
Dose5
(ing/kg/diiv)
MOli"
Dose7
(nig/kg/diiv)
MOli8
Olive; Papaya; Passion Fruit
(Granadilla); Peach; Pear;
Persimmon; Pistachio; Plum;
Prune; Subtropical/Tropical
Fruit; Tree Nuts
Orchard/Vineyard: Macadamia
Nut (Bushnut)
5.1
EC
0.043
EC
0.50
lb ai/A
40 A
0.00128
4700
0.0000108
240
Field crop, typical: Artichoke;
Asparagus; Brassica (head and
stem) Vegetables; Carrots
(Including Tops); Corn, Sweet;
Cucurbit Vegetables; Eggplant;
Flowering Plants; Fruiting
Vegetables; Garlic; Ginger;
Leafy Vegetables; Lettuce;
Manioc (Cassava); Melons;
Okra; Onions; Peas
5.1
EC
0.043
EC
1.0
lb ai/A
80 A
0.0051
1200
0.000043
60
(Unspecified); Pepper;
Pineapple; Root and Tuber
Vegetables; Rhubarb; Sugar
Beet; Tomato; Turnip Greens;
Yam
Field crop, typical: Tobacco
5.1
EC
0.043
EC
0.94
lb ai/A
80 A
0.0048
1300
0.0000404
64
Field crop, typical: Legume
Vegetables; Sage, Clary; Taro;
Vegetables (Unspecified)
5.1
EC
0.043
EC
0.80
lb ai/A
80 A
0.00408
1500
0.0000344
76
Field crop, typical: Guar;
Lentils; Peas, Dried Type; Peas,
5.1
EC
0.043
EC
0.50
0.00255
2400
0.0000215
120
Pigeon; Strawberry; Tuberous
and Corm Vegetables;
lb ai/A
Field crop, high acreage:
Alfalfa; Clover
5.1
EC
0.043
EC
1.5
lb ai/A
200 A
0.0191
310
0.000161
16
Field crop, high acreage:
Barley;
Coniferous/Evergreen/Softwood
(non-food); Corn, Field; Corn,
Pop; Cotton; Fallowland;
5.1
EC
0.043
EC
1.0
lb ai/A
200 A
0.0128
470
0.000108
24
Peanuts; Peas (Unspecified);
Rice; Safflower; Sorghum;
Soybean; Sugarcane; Sunflower;
Tyfon; Wheat
Page 100 of 103
-------
Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
l.xposu IV
Seeiui rio
Dernuil Iinit
Level of
1'1'U or
Engineering
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
Miiximum
A reii
Trented
or
Amount
Mil ml led
Diiilv4
Derniiil
LOC= 100
Inhiiliition
L<)('= 100
Crop or Target.
Exposure1
(fig/lb ai)
Application
Riite'
Dose5
(ing/kg/diiv)
MOli"
Dose7
(nig/kg/diiv)
MOli8
Field crop, high acreage:
Legume Vegetables; Mint
5.1
EC
0.043
EC
0.80
lb ai/A
200 A
0.0102
590
0.000086
30
Field crop, high acreage:
Grasses Grown for Seed; Potato,
White/Irish (or Unspecified)
5.1
EC
0.043
EC
0.6
lb ai/A
200 A
0.00765
780
0.0000645
40
Field crop, high acreage: Beans,
Dried-Type; Hops; Pastureland;
Peas, Dried-Type; Peas, Pigeon;
Tuberous and Corm Vegetables
5.1
EC
0.043
EC
0.5
lb ai/A
200 A
0.00638
940
0.0000538
48
Field crop, high acreage: Root
and Tuber Vegetables
5.1
EC
0.043
EC
0.3
lb ai/A
200 A
0.00383
1600
0.0000323
80
Flagger
Field crop, high acreage:
Alfalfa; Clover
1.5
lb ai/A
350 A
0.0788
76
0.00023
11
Field crop, typical: Asparagus;
Brassica (head and stem)
Vegetables; Carrots (Including
Tops); Corn, Sweet; Cucurbit;
Vegetables; Eggplant; Fruiting
Vegetables; Leafy Vegetables;
Lettuce; Melons; Peas
(Unspecified); Pepper; Sugar
Beet; Tomato; Turnip Greens
Orchard/Vineyard; Almond
Spray
(all starting
formulations),
Aerial
Field crop, high-acreage; Barley;
Beans, Dried-Type; Corn, Field;
Corn, Pop; Cotton;
Deciduous/Broadleaf/Hardwood;
Fallowland; Forestry; Grasses
Grown for Seed; Mint;
Nonagricultural Areas;
Pastureland/Rangeland; Peas
(Unspecified); Potato,
White/Irish (or Unspecified);
Rice; Root and Tuber
Vegetables; Safflower;
Sorghum; Soybeans; Sugarcane;
Sunflower; Tuberous and Corm
Vegetables; Wheat
12
SL/G
0.035
APF10R
1.0
lb ai/A
350 A
0.0525
110
0.000154
17
Field crop, typical: Legume
Vegetables; Sage, Clary
0.80
lb ai/A
350 A
0.042
140
0.000123
21
Page 101 of 103
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Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk
Estimates for Paraquat
1\ posu IV
Scrim i'i<>
Dcrmiil In it
1,1'Vl'l of
1'1'li or
En ginee ring
control2
Inhiiliition
Unit
Exposure1
(fig/lb :ii)
level of
1'1'li or
Engineering
control
M ii xi ill u ill
A reii
Trented
or
Amount
I In ml led
Diiilv4
Dcrniiil
LOC= 100
Inhiiliition
L<)('= 100
( j'op or Tiirget
Exposure'
(fig/lb :ii)
Application
Riite'
Dose5
(mg/kg/diiv)
MOE"
Dose7
(mg/kg/diiv)
MOE8
Field crop, typical: Lentils; Peas,
Dried Type; Tuberous and Corm
Vegetables;
Orchard/Vineyard; Grapes
0.50
lb ai/A
350 A
0.0263
230
0.0000766
34
Field crop, high acreage: Peas,
Dried-Type
Field crop, typical: Root and
Tuber Vegetables
0.30
lb ai/A
350 A
0.0158
380
0.000046
57
lYIixcr/Loiider/Applinitor
8260
SL/G
0.015
lb ai/gallon
0.062
97
Liquid,
Backpack,
Ground/soil-
directed
All Use Sites
4120
DL/G
0.0309
190
0.00000194
1300
Pastureland
8260
SL/G
0.258
APF10 R
0.019
0.0785
76
0.00000245
1100
4120
DL/G
lb ai/gallon
0.0391
150
All Use Sites
30500
SL/G
0.015
0.229
26
0.0000519
50
Liquid,
Backpack,
16900
DL/G
6.91
APF10R
lb ai/gallon
40
gallons
0.126
48
Broadcast
Pastureland
30500
SL/G
0.019
0.29
21
0.0000656
40
16900
DL/G
lb ai/gallon
0.16
38
All Use Sites
430
SL/G
0.015
0.00323
1900
0.0000225
120
Liquid,
Manually-
pressurized
Handwand,
Broadcast
365
DL/G
430
APF10R
lb ai/gallon
0.00274
2200
Pastureland
430
SL/G
0.019
0.00409
1500
0.0000285
91
365
DL/G
lb ai/gallon
0.00346
1700
Liquid,
Mechanically-
All Use Sites
2050
SL/G
0.868
APF10R
0.015
lb ai/gallon
1000
gallons
0.385
16
0.000163
16
pressurized
1360
DL/G
0.255
24
Page 102 of 103
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Tabic D.l. Occupational Handler Non-Canccr Exposure and Risk Estimates for Paraquat
Exposu re
Sceiui rio
Handgun,
Broadcast
(foliar);
Drench/Soil-
/Ground-
directed
Crop or Tiirget
Dernuil Iinit
Exposure1
(fig/lb :ii)
I A'Vt'l Of
PPE or
Engineering
control2
Inhsilsition
Unit
Exposure1
0ig/lh iii)
Level of
PPE or
Engineering
control
M;ixi mil in
Application
Riite'
A mi
Trented
or
Amount
I In ml led
Dnilv4
Derniiil
LOC= 100
Inhiiliition
L()C'= 100
Dose5
(nig/kg/diiv)
MOli"
Dose7
(nig/kg/diiv)
MOli8
Pastureland
2050
SL/G
0.019
lb ai/gallon
0.488
12
0.000206
13
1360
DL/G
0.323
19
Losidcr/Applicsitor
Liquid,
Backpack,
Broadcast
Rights-of-Way
30500
SL/G
6.91
APF10R
0.015
lb ai/gallon
40
gallons
0.229
26
0.0000519
50
16900
DL/G
0.126
48
1. Based on the "Occupational Pesticide Handler Unit Exposure Surrogate Reference Table" (https://www.epa. goy/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handler-exposure-data):
Level of mitigation: Baseline, PPE, Eng. Controls.
2. SL/G = single layer clothing/gloves; DL/G = double layer clothing/gloves; APF 10 R = assigned protection factor 10 respirator; EC = engineering control.
3. Based on registered labels as summarized in the Line by Line, and Maximum Use Scenario Pesticide Label Usage Summary (PLUS) Reports as generated by OPP's Biological and Economic Analysis Division
(BEAD).
4. Exposure Science Advisory Council Policy #9.1.
5. Dermal Dose = Dermal Unit Exposure (jug/lb ai) / Conversion Factor (0.001 mg/jig) x Application Rate (lb ai/acre or gal) / Area Treated or Amount Handled Daily (A or gal/day) x DAF (%) -5- BW (80 kg).
6. Dermal MOE = Dermal NOAEL (6 mg/kg/day) Dermal Dose (mg/kg/day).
7. Inhalation Dose = Inhalation Unit Exposure (jug/lb ai) / Conversion Factor (0.001 mg/jig) x Application Rate (lb ai/acre or gal) / Area Treated or Amount Handled Daily (A or gal/day) -5- BW (80 kg).
8. Inhalation MOE = Inhalation NOAEL (0.0026 mg/kg/day) + Inhalation Dose (mg/kg/day).
Page 103 of 103
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