Dicrotophos Dietary Exposure and Risk Assessment DP No: D418103 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: July 10, 2014 

SUBJECT: Dicrotophos: Acute and Steady State Aggregate Dietary (Food and Drinking 

Water) Exposure and Risk Assessments to Support Registration Review 

PC Code: 035201 

Decision No.: 454409 

Petition No.: NA 

DP Barcode: 0418103 

Registration No.: NA 

Regulatory Action: Registration Review 

Risk Assessment Type: Dietary Case No.: 0145 

TXRNo.: NA CAS No.: 141-66-2 

MRIDNo.:NA 

FROM: 

THROUGH: 

TO: 

Thurston Morton, Chemist 

Risk Assessment Branch IV 

40 FR· 180.299~ 

Health Effects Division (7509P) / 

Sheila 

Don Wi

Piper

lbur, 

, 

Chemist 

Chemist ~ ~ ~ 

Dietary Exposure Science Advisory oun 1 ESAC) 

And 

Elissa Reaves, Ph.D., Branch Chief 

Risk Assessment Branch IV, HED (7509P) 

Russell Wasem 

Risk Management and Implementation Branch 1 

Pesticide Re-evaluation Division (7508P) 

Executive Summary 

Acute and steady state aggregate dietary food and drinking water exposure and risk assessments 

for dicrotophos were conducted using the Dietary Exposure Evaluation Model and Calendex 

software with the Food Commodity Intake Database (FCID). This software uses 2003-2008 food 

consumption data from the U.S. Department of Agriculture's (USDA's) National Health and 

Nutrition Examination Survey, What We Eat in America, (NHANES/WWEIA). This dietary 

analysis is updated to reflect the latest consumption data and to support registration review. This 

memorandum was reviewed by two peer reviewers of the DESAC per the current DESAC 

Standard Operating Procedure (SOP). 

Page I of20 
Acute Dietary (Food and Drinking Water) Exposure Results and Characterization 

Dicrotophos is a broad spectrum organophosphate insecticide. The only dicrotophos end-use 

formulation currently registered is a water-miscible formulation which may be foliarly applied to 

established cotton plants or used as a tree injection treatment for ornamental and non-food 

producing trees. 

An unrefined acute dietary exposure assessment was conducted to estimate the dietary exposure 

and risk associated with registration review. The acute dietary exposure assessment incorporated 

tolerance level residue and 100% crop treated for the acute analysis. The drinking water 

concentration was based on the use of dicrotophos from three cotton scenarios. 

The acute aggregate dietary exposure estimates are below HED' s level of concern ( < 1 00 % the 

acute population adjusted dose (aPAD)) for the U.S. population and all population subgroups. 

Combined dietary exposure from food and drinking water at the 951

h percentile of exposure is 

13% ofthe aPAD for the U.S. population and 27% ofthe aPAD for all infants (<1 yrs old), the 

most highly exposed population subgroup. 

Steady State Dietary (Food and Drinking Water) Exposure Results and Characterization 

Organophosphate may exhibit a phenomenon known as steady state acetylcholinesterase (AChE) 

inhibition which is the most sensitive endpoint for alllifestages. After repeated dosing at the 

same dose, the amount of AChE inhibition in a given dose remains consistent across duration. 

For this reason, a steady-state point of departure (PoDs) was selected for oral exposure to 

dicrotophos (see Table 3). 

An unrefmed steady state dietary exposure assessment was conducted to estimate the dietary 

risks associated with the registration of dicrotophos. The steady state dietary exposure 

assessment incorporated tolerance level residues and 100% crop treated. The steady state 

aggregate dietary exposure estimates from Calendex are above HED's level of concern(> 100% 

of the PAD) for the U.S. population and all population subgroups. Combined dietary exposure 

from food and drinking water is 136% of PAD for the U.S. population and 358% of the PAD for 

children 1-2 years, the most highly exposed population subgroup. 

Cancer Dietary (Food and Drinking Water) Exposure Results and Characterization 

Dicrotophos is classified as showing "Suggestive evidence of carcinogenicity, but not sufficient 

to assess human carcinogenic potential ". Quantitative risk assessment for dicrotophos using the 

Reference Dose (RID) approach will adequately account for all chronic toxic effects, including 

carcinogenicity. 

Page 2 of20 
Page 3 of 20

I. Introduction

Dietary risk assessment incorporates both exposure and toxicity of a given pesticide. For acute 

and steady state assessments, the risk is expressed as a percentage of a maximum acceptable dose 

(i.e., the dose that HED has concluded will result in no unreasonable adverse health effects). 

This dose is referred to as the population adjusted dose (PAD). The PAD is equivalent to the 

point of departure (POD, NOAEL, LOAEL, e.g.) divided by the required uncertainty or safety 

factors.

For acute and non-cancer chronic exposures, HED is concerned when estimated dietary risk 

exceeds 100% of the PAD. References that discuss the acute and chronic risk assessments in 

more detail are available on the EPA/pesticides web site: “Available Information on Assessing 

Exposure from Pesticides, A User’s Guide,” 21-JUN-2000, web link: 

http://www.epa.gov/fedrgstr/EPA-PEST/2000/July/Day-12/6061.pdf; or see SOP 99.6 (20-AUG1999).

The most recent dietary risk assessment for dicrotophos was conducted by B. Daiss(October 30, 

2001, D278883).

II. Residue Information

Dicrotophos (dimethyl phosphate of 3-hydroxy-N,N-dimethyl-cis-crotonamide) is a contact, 

systemic acaricide/insecticide registered for use on cotton. Permanent tolerances are established 

for the residues of dicrotophos and monocrotophos at 0.20 ppm in cotton, undelinted seed and at 

2.0 ppm in cotton gin byproducts (40CFR §180.299). 

The residues of concern in plants are dicrotophos and monocrotophos.

Residue Data used for Acute and Steady state Dietary Assessments

An unrefined acute dietary exposure assessment was conducted using tolerance level residues 

and 100% crop treated. 

The USDA Pesticide Data Program (PDP) monitored pesticide residues in catfish in 2008. PDP 

analyzed 552 samples of catfish for dicrotophos residues. None of the samples contained 

detectable residues. As a result, residues in fish were not included in the assessment.

III. Percent Crop Treated Information

The acute and steady state aggregate dietary analyses were performed assuming 100% of each 

commodity was treated with dicrotophos.
Page 4 of 20

IV. Drinking Water Data

This assessment uses maximum rates but considers typical rates though monitoring data exceeds 

the resulting EDWCs in some instances. The assessment considers a parent only approach but 

also considers the major degradates as parent in a total toxic residue (TTR) approach. Toxicity 

data and acceptable environmental fate data is unavailable for dicrotophos degradates. Inclusion 

of the TTR approach is provided for a complete characterization of EDWCs. Submission of 

degradate environmental fate data and/or toxicity data for the identified degradates could reduce 

uncertainty in the TTR approach and potentially reduce acute and chronic risk. However, 

EDWCs are reduced by <10% from a TTR approach to a parent only approach thus other 

opportunities for refinement or mitigation may reduce EDWCs further. Additionally, a single 

soil metabolism study is used for the derivation of the aerobic soil metabolism input parameter 

which necessitates incorporation of a 3x factor for use as a model input. This input parameter is 

intended to represent the many varieties of soil and microbial communities that may metabolize 

dicrotophos at differing rates which is the rationale for the 3x factor. Additional aerobic soil 

metabolism data would allow for better characterization of the half life, remove the need for the 

3x factor, and reduce uncertainty. Given current uncertainty, the following degradates are 

included in the TTR approach:

Daily time series outputs for the thirty year simulation were provided to HED for use in dietary 

exposure modeling.

Table 5.3 Summary of Estimated Surface Water and Groundwater Concentrations 

for Dicrotophos.

Scenario Surface Water Conc., ppb a Groundwater Conc., ppb b

Acute 12.44 0.06

Chronic (non-cancer) 0.80 0.06

Chronic (cancer) 0.41 0.06

a From the Tier II PRZM-EXAMS based on 3 cotton scenarios (NC, MS, TX)

b From the PRZM-GW model.

D399359, A. Shelby, 8/1/2013.

V. DEEM-FCID Program and Consumption Information

A dicrotophos acute dietary exposure assessment was conducted using the DEEM-FCID, 

Version 3.16, which incorporates 2003-2008 consumption data from USDA’s 

NHANES/WWEIA. The data are based on the reported consumption of more than 20,000 

individuals over two non-consecutive survey days. Foods “as consumed” (e.g., apple pie) are 

linked to EPA-defined food commodities (e.g., apples, peeled fruit - cooked; fresh or N/S; baked; 

or wheat flour - cooked; fresh or N/S, baked) using publicly available recipe translation files 

developed jointly by USDA/ARS and EPA. For chronic exposure assessment, consumption data 

are averaged for the entire U.S. population and within population subgroups. However, for acute 

exposure assessment, consumption data are retained as individual consumption events. Based on 

analysis of the 2003-2008 WWEIA consumption data, which took into account dietary patterns 

and survey respondents, HED concluded that it is most appropriate to report risk for the 

following population subgroups: the general U.S. population, all infants (<1 year old), children 
Page 5 of 20

1-2, children 3-5, children 6-12, youth 13-19, adults 20-49, females 13-49, and adults 50-99

years old.

For an acute exposure assessment, individual one-day food consumption data are used on an 

individual-by-individual basis. The reported consumption amounts of each food item can be 

multiplied by a residue point estimate and summed to obtain a total daily pesticide exposure for a 

deterministic exposure assessment, or “matched” in multiple random pairings with residue values 

and then summed in a probabilistic assessment. The resulting distribution of exposures is 

expressed as a percentage of the aPAD on both a user (i.e., only those who reported eating 

relevant commodities/food forms) and a per-capita (i.e., those who reported eating the relevant 

commodities as well as those who did not) basis. In accordance with HED policy, per capita 

exposure and risk are reported for analyses performed at all levels of refinement. However, for 

deterministic assessments, any significant differences in user vs. per capita exposure and risk are 

specifically identified and noted in the risk assessment.

VI. CALENDEX-FCID Program 

Calendex-FCIDTM provides a focus detailed profile of potential exposures to individuals across a 

calendar year. A calendar-based approach provides the ability to estimate daily exposures from 

multiple sources over time to an individual and is in keeping with two key tenets of aggregate 

risk assessment: 1) that exposures when aggregated are internally consistent and realistic; and 2) 

that appropriate temporal and geographic linkages or correlations/associations between exposure 

scenarios are maintained. Calendex also enables HED to identify potential risks caused by cooccurrence of exposures from multiple routes and pathways (e.g., near simultaneous same-day 

exposures through drinking water and residential uses). 

HED’s steady state assessment considers the potential risk from a 21-day exposure duration 

using a 3-week rolling average (sliding by day) across the year. For this assessment, the same 

food residue values used in the acute assessment were used for the 21-day duration. In the 

Calendex software, one diary for each individual in the WWEIA is selected to be paired with a 

randomly selected set of residue values for each food consumed. For the water residue values, 

Calendex incorporates PRZM-EXAMs drinking water residue by selecting a year at random 

from those available in the designated drinking water residue file. It then retrieves the residue 

value assigned to the day being evaluated and multiplies it to the food-based water consumption 

value as designated during the analysis setup by the user. For weekly exposure (e.g. exposure 

averaged over one week) which uses 30 years of PRZM-EXAMs data, Calendex will randomly 

choose a year for the first iteration. It will then take the residue from the first day of the week 

and multiply it by the consumption amount for the individual from the WWEIA. Calendex will 

continue this process for the entire week (several sequential days) and average the exposures to 

estimate a weekly exposure. Calendex will randomly choose another year and continue the 

process until all of the iterations designated for this analysis have been completed.
Page 6 of 20

VII. Toxicological Information

Dicrotophos is a member of the organophosphate (OP) class of pesticides. Like other OPs, the 

initiating event in the adverse outcome pathway (AOP), also often called the mode of action 

(MOA), for dicrotophos involves inhibition of the enzyme acetylcholinesterase (AChE) via 

phosphorylation of the serine residue at the active site of the enzyme. This inhibition leads to 

accumulation of acetylcholine and ultimately to neurotoxicity in the central and/or peripheral 

nervous system. For dicrotophos, AChE inhibition is the most sensitive endpoint in the 

toxicology database in multiple species, durations, lifestages, and routes. AChE inhibition is the 

focus of this hazard characterization; the availability of reliable AChE inhibition dose response 

data is one of the key determinants in evaluating the toxicology database. In general, OPs reach 

steady state within 2-3 weeks but this can vary among OPs. In the case of dicrotophos, the 

results show a clear pattern of steady state reached at or near 15 days of exposure. In addition to 

the consistency across durations, the data across multiple studies (repeat CCA study, gestational 

data from the DNT, subchronic neurotoxicity study, and subchronic rat toxicity study) are 

similar. Although the durations of the toxicity and exposure assessments may differ, an exact 

match is not necessary and would suggest a level of precision that the toxicity data do not 

support. Furthermore, humans would be expected to be slower and closer to the typical 2-3 

week window of duration. Given this, the 21-day and longer exposure assessment is 

scientifically supportable and also provides consistency across the OPs. Given the results in 

Table 3, for dicrotophos, acute (single day) and steady state durations are appropriate for human 

health risk assessment. HED’s ToxSAC met (07/18/2013) to consider the endpoints of 

toxicological concern for the dietary exposure. 

Table 3. Summary of Toxicological Doses and Endpoints for Dicrotophos for use in Human Health 

Risk Assessments.

Exposure/

Scenario

Point of 

Departure

Uncertainty/ 

FQPA Safety 

Factors

RfD, PAD, Level 

of Concern for 

Risk Assessment

Study and Toxicological 

Effects

Acute Dietary (all 

populations, 

including females 

13-49)

BMDL10 = 

0.07mg/kg/day

UFA = 10x

UFH = 10x

FQPA SF = 

1x

Acute PAD = 

0.0007 mg/kg/day 

CCA Study (MRID 4615205) 

in the rat – PND 8, 15, & 22 

Inhibition of brain ChE in 

male and female rat pups.

Steady-State 

Dietary (all 

populations)

BMDL10 = 

0.03 mg/kg/day

UFA = 10x

UFH = 10x

FQPA SF = 

1x

Steady State PAD 

= 0.0003 

mg/kg/day

Subchronic and chronic 

toxicity studies (OP CRA 

2002, 2006; MRID’s 

43980201 and 44527802)

Inhibition of brain ChE in 

adult rat

Cancer (oral, 

dermal, 

inhalation)

Classification: "Suggestive evidence of carcinogenicity, but not sufficient to assess 

human carcinogenic potential”.

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. BMDL10= benchmark dose lower limit for 10% response. UFA = extrapolation from animal to human 

(interspecies). UFH = potential variation in sensitivity among members of the human population (intraspecies). 

FQPA SF = FQPA Safety Factor. RfD = reference dose. 
Page 7 of 20

VIII. Results/Discussion 

As stated above, for acute and steady state assessments, HED are concerned when dietary risk 

exceeds 100% of the PAD. The DEEM-FCID and Calendex-FCID analyses estimate the dietary 

exposure of the U.S. population and various population subgroups. The results reported in tables

4 and 5 are for the general U.S. Population, all infants (<1 year old), children 1-2, children 3-5, 

children 6-12, youth 13-19, females 13-49, adults 20-49, and adults 50-99 years. 

For food and drinking water, the acute dietary risk estimate is below HED’s level of concern at 

the 99.9th percentile of exposure. The acute dietary exposure using DEEM was estimated for 

the U.S. population is 13% of the aPAD and 27% of the aPAD for all infants (<1 yrs old), the 

most highly exposed population subgroup. The steady state aggregate dietary (food and 

drinking water) exposure estimates using Calendex are above HED’s level of concern for the 

U.S. population and all population subgroups. Combined dietary exposure from food and 

drinking water is 136% of PAD for the U.S. population and 358% of the PAD for children 1-2 

years, the most highly exposed population subgroup.

Results of Acute Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) MS Cotton Typical Rate

Population Subgroup

aPAD 

(mkd)*

95th Percentile 99th Percentile 99.9th Percentile

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

General U.S. Population

0.0007

0.000035 5.1 0.000091 13 0.000236 34

All Infants (< 1 year old) 0.000069 10 0.000237 34 0.00630 90

Children 1-2 years old 0.000060 8.6 0.000150 21 0.000400 57

Children 3-5 years old 0.000057 8.1 0.000128 18 0.000320 46

Children 6-12 years old 0.000042 6.0 0.000101 14 0.000244 35

Youth 13-19 years old 0.000030 4.3 0.000076 11 0.000190 27

Adults 20-49 years old 0.000032 4.6 0.000087 12 0.000209 30

Adults 50-99 years old 0.000030 4.3 0.000077 11 0.000190 27

Females 13-49 years old 0.000032 4.6 0.000085 12 0.000213 30
Page 8 of 20

Results of Acute Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) MS Cotton Max Rate

Population Subgroup

aPAD 

(mkd)*

95th Percentile 99th Percentile 99.9th Percentile

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

General U.S. Population

0.0007

0.000047 6.7 0.000132 19 0.000360 51

All Infants (< 1 year old) 0.000103 15 0.000362 52 0.001037 150

Children 1-2 years old 0.000076 11 0.000214 31 0.000547 78

Children 3-5 years old 0.000071 10 0.000181 26 0.000468 67

Children 6-12 years old 0.000052 7.5 0.000145 21 0.000333 48

Youth 13-19 years old 0.000037 5.3 0.000107 15 0.000287 41

Adults 20-49 years old 0.000045 6.4 0.000127 18 0.000340 49

Adults 50-99 years old 0.000042 6.1 0.000117 17 0.000309 44

Females 13-49 years old 0.000044 6.3 0.000126 18 0.000343 49

Results of Acute Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) TX Cotton Typical Rate

Population Subgroup

aPAD 

(mkd)*

95th Percentile 99th Percentile 99.9th Percentile

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

General U.S. Population

0.0007

0.000034 4.8 0.000086 12 0.000224 32

All Infants (< 1 year old) 0.000065 9.3 0.000219 31 0.000613 88

Children 1-2 years old 0.000057 8.2 0.000141 20 0.000402 57

Children 3-5 years old 0.000055 7.8 0.000122 17 0.000320 46

Children 6-12 years old 0.000040 5.8 0.000096 14 0.000237 34

Youth 13-19 years old 0.000029 4.2 0.000072 10 0.000180 26

Adults 20-49 years old 0.000031 4.4 0.000082 11 0.000198 28

Adults 50-99 years old 0.000029 4.1 0.000072 10 0.000182 26

Females 13-49 years old 0.000030 4.4 0.000080 11 0.000203 29
Page 9 of 20

Results of Acute Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) TX Cotton Max Rate

Population Subgroup

aPAD 

(mkd)*

95th Percentile 99th Percentile 99.9th Percentile

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

General U.S. Population

0.0007

0.000045 6.5 0.000126 18 0.000342 49

All Infants (< 1 year old) 0.000096 14 0.000344 49 0.001005 140

Children 1-2 years old 0.000074 11 0.000206 29 0.000517 74

Children 3-5 years old 0.000069 9.9 0.000174 25 0.000441 63

Children 6-12 years old 0.000050 7.2 0.000141 20 0.000323 46

Youth 13-19 years old 0.000036 5.2 0.000103 15 0.000273 39

Adults 20-49 years old 0.000043 6.2 0.000121 17 0.000322 46

Adults 50-99 years old 0.000041 5.8 0.000111 16 0.000299 43

Females 13-49 years old 0.000043 6.1 0.000120 17 0.000327 47

Results of Acute Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) NC Cotton Typical Rate

Population Subgroup

aPAD 

(mkd)*

95th Percentile 99th Percentile 99.9th Percentile

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

General U.S. Population

0.0007

0.000034 4.8 0.000085 12 0.000218 31

All Infants (< 1 year old) 0.000066 9.4 0.000216 31 0.000588 84

Children 1-2 years old 0.000057 8.2 0.000141 20 0.000400 57

Children 3-5 years old 0.000055 7.8 0.000120 17 0.000319 46

Children 6-12 years old 0.000040 5.8 0.000094 13 0.000233 33

Youth 13-19 years old 0.000029 4.2 0.000071 10 0.000175 25

Adults 20-49 years old 0.000031 4.4 0.000081 12 0.000193 28

Adults 50-99 years old 0.000028 4.1 0.000071 10 0.000176 25

Females 13-49 years old 0.000030 4.3 0.000078 11 0.000193 28
Page 10 of 20

Results of Acute Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) NC Cotton Max Rate

Population Subgroup

aPAD 

(mkd)*

95th Percentile 99th Percentile 99.9th Percentile

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

Exposure 

(mkd)

% 

aPAD

General U.S. Population

0.0007

0.000046 6.6 0.000127 18 0.000339 48

All Infants (< 1 year old) 0.000100 14 0.000348 50 0.000980 140

Children 1-2 years old 0.000074 11 0.000207 30 0.000518 74

Children 3-5 years old 0.000070 10 0.000175 25 0.000442 63

Children 6-12 years old 0.000051 7.3 0.000140 20 0.000323 46

Youth 13-19 years old 0.000037 5.2 0.000104 15 0.000270 39

Adults 20-49 years old 0.000044 6.3 0.000122 17 0.000316 45

Adults 50-99 years old 0.000041 5.9 0.000113 16 0.000293 42

Females 13-49 years old 0.000043 6.2 0.000121 17 0.000318 45
Dicrotophos Dietary Exposure and Risk Assessment DP No: D418103

______________________________________________________________________________

Page 11 of 20

For the steady state dietary exposure analyses, All infants <1 yr old was the population subgroup with the highest exposure ranging 

from 40 to 63 % ssRfD at the 70th percentile of exposure. At the 90th percentile of regulation, All infants <1 yr old was the population 

subgroup with the highest exposure ranging from 87 to 150 % ssRfD. And at the 95th percentile of exposure, All infants <1 yr old was 

the population subgroup with the highest exposure ranging from 120 to 210 % ssRfD.

Results of Steady State Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) MS Cotton Max Rate

Population Subgroup

PAD 

(mkd)*

70th Percentile 90th Percentile 95th Percentile 99.9th Percentile

Exposure 

(mkd) % PAD

Exposure 

(mkd) % PAD

Exposure 

(mkd)

% 

PAD

Exposure 

(mkd)

% 

PAD

General U.S. Population

0.0003

0.000150 50 0.000221 74 0.000277 92 0.000750 250

All Infants (< 1 year old) 0.000179 60 0.000440 150 0.000632 210 0.001863 620

Children 1-2 years old 0.000166 55 0.000279 93 0.000367 120 0.001220 410

Children 3-5 years old 0.000160 53 0.000249 83 0.000315 110 0.000950 320

Children 6-12 years old 0.000152 51 0.000205 68 0.000258 86 0.000690 230

Youth 13-19 years old 0.000149 50 0.000192 64 0.000237 79 0.000600 200

Adults 20-49 years old 0.000155 52 0.000222 74 0.000277 92 0.000650 220

Adults 50-99 years old 0.000124 41 0.000178 59 0.000228 76 0.000590 200

Females 13-49 years old 0.000154 51 0.000223 74 0.000281 94 0.000680 230
Page 12 of 20

Results of Steady State Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) MS Cotton Typical Rate

Population Subgroup

PAD 

(mkd)*

70th Percentile 90th Percentile 95th Percentile 99.9th Percentile

Exposure 

(mkd) % PAD

Exposure 

(mkd) % PAD

Exposure 

(mkd)

% 

PAD

Exposure 

(mkd)

% 

PAD

General U.S. Population

0.0003

0.000150 50 0.000188 63 0.000206 69 0.000480 160

All Infants (< 1 year old) 0.000119 40 0.000289 96 0.000399 130 0.001086 360

Children 1-2 years old 0.000152 51 0.000211 70 0.000262 87 0.000840 280

Children 3-5 years old 0.000149 50 0.000191 64 0.000229 76 0.000660 220

Children 6-12 years old 0.000145 48 0.000186 62 0.000197 66 0.000480 160

Youth 13-19 years old 0.000144 48 0.000185 62 0.000195 65 0.000410 140

Adults 20-49 years old 0.000146 49 0.000188 63 0.000206 69 0.000420 140

Adults 50-99 years old 0.000116 39 0.000149 50 0.000160 53 0.000360 120

Females 13-49 years old 0.000146 49 0.000188 63 0.000208 69 0.000430 140
Page 13 of 20

Results of Steady State Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) NC Cotton Max Rate

Population Subgroup

PAD 

(mkd)*

70th Percentile 90th Percentile 95th Percentile 99.9th Percentile

Exposure 

(mkd) % PAD

Exposure 

(mkd) % PAD

Exposure 

(mkd)

% 

PAD

Exposure 

(mkd)

% 

PAD

General U.S. Population

0.0003

0.000152 51 0.000213 71 0.000265 88 0.000750 250

All Infants (< 1 year old) 0.000188 63 0.000413 140 0.000590 200 0.001774 590

Children 1-2 years old 0.000166 55 0.000277 92 0.000356 120 0.001250 420

Children 3-5 years old 0.000159 53 0.000242 81 0.000302 100 0.000950 320

Children 6-12 years old 0.000151 50 0.000201 67 0.000250 83 0.000720 240

Youth 13-19 years old 0.000148 49 0.000191 64 0.000230 77 0.000600 200

Adults 20-49 years old 0.000153 51 0.000212 71 0.000263 88 0.000650 220

Adults 50-99 years old 0.000122 41 0.000168 56 0.000215 72 0.000551 180

Females 13-49 years old 0.000153 51 0.000214 71 0.000265 88 0.000650 220
Page 14 of 20

Results of Steady State Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) NC Cotton Typical Rate

Population Subgroup

PAD 

(mkd)*

70th Percentile 90th Percentile 95th Percentile 99.9th Percentile

Exposure 

(mkd) % PAD

Exposure 

(mkd) % PAD

Exposure 

(mkd)

% 

PAD

Exposure 

(mkd)

% 

PAD

General U.S. Population

0.0003

0.000144 48 0.000187 62 0.000197 66 0.000480 160

All Infants (< 1 year old) 0.000120 40 0.000261 87 0.000369 120 0.001038 350

Children 1-2 years old 0.000151 50 0.000202 67 0.000251 84 0.000800 270

Children 3-5 years old 0.000148 49 0.000190 63 0.000219 73 0.000630 210

Children 6-12 years old 0.000144 48 0.000186 62 0.000196 65 0.000470 160

Youth 13-19 years old 0.000143 48 0.000184 61 0.000195 65 0.000390 130

Adults 20-49 years old 0.000145 48 0.000186 62 0.000197 66 0.000420 140

Adults 50-99 years old 0.000115 38 0.000148 49 0.000156 52 0.000346 120

Females 13-49 years old 0.000145 48 0.000187 62 0.000197 66 0.000420 140
Page 15 of 20

Results of Steady State Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) TX Cotton Max Rate

Population Subgroup

PAD 

(mkd)*

70th Percentile 90th Percentile 95th Percentile 99.9th Percentile

Exposure 

(mkd) % PAD

Exposure 

(mkd) % PAD

Exposure 

(mkd)

% 

PAD

Exposure 

(mkd)

% 

PAD

General U.S. Population

0.0003

0.000150 50 0.000211 70 0.000261 87 0.000690 230

All Infants (< 1 year old) 0.000182 61 0.000415 140 0.000573 190 0.001588 530

Children 1-2 years old 0.000170 57 0.000268 89 0.000345 120 0.001080 360

Children 3-5 years old 0.000159 53 0.000239 80 0.000244 81 0.000890 300

Children 6-12 years old 0.000150 50 0.000199 66 0.000245 82 0.000650 220

Youth 13-19 years old 0.000148 49 0.000190 63 0.000225 75 0.000540 180

Adults 20-49 years old 0.000180 60 0.000212 71 0.000259 86 0.000600 200

Adults 50-99 years old 0.000123 41 0.000166 55 0.000210 70 0.000490 160

Females 13-49 years old 0.000153 51 0.000214 71 0.000264 88 0.000590 200
Page 16 of 20

Results of Steady State Dietary Exposure Analysis for Dicrotophos (Food and Drinking Water) TX Cotton Typical Rate

Population Subgroup

PAD 

(mkd)*

70th Percentile 90th Percentile 95th Percentile 99.9th Percentile

Exposure 

(mkd) % PAD

Exposure 

(mkd) % PAD

Exposure 

(mkd)

% 

PAD

Exposure 

(mkd)

% 

PAD

General U.S. Population

0.0003

0.000140 47 0.000186 62 0.000197 66 0.000440 150

All Infants (< 1 year old) 0.000119 40 0.000265 88 0.000360 120 0.000929 310

Children 1-2 years old 0.000150 50 0.000199 66 0.000246 82 0.000720 240

Children 3-5 years old 0.000147 49 0.000189 63 0.000217 72 0.000590 200

Children 6-12 years old 0.000144 48 0.000185 62 0.000196 65 0.000440 150

Youth 13-19 years old 0.000143 48 0.000184 61 0.000195 65 0.000360 120

Adults 20-49 years old 0.000145 48 0.000186 62 0.000196 65 0.000390 130

Adults 50-99 years old 0.000116 39 0.000149 50 0.000157 52 0.000310 100

Females 13-49 years old 0.000145 48 0.000186 62 0.000197 66 0.000390 130
Dicrotophos Dietary Exposure and Risk Assessment DP No: D418103

______________________________________________________________________________

Page 17 of 20

IX. Characterization of Inputs/Outputs

HED has conducted unrefined acute and steady state dietary risk assessments for coumaphos. 

OPs exhibit a phenomenon known as steady state AChE inhibition and for coumaphos a steady 

state endpoint was selected. Although, there are rat data at a shorter time period (i.e., 15 days) 

than 21 days, exposure assessments of 21 days and longer were conducted for all routes of 

exposure (i.e., oral, dermal and inhalation) for all single chemical OP assessments using 

Calendex. Given this, the 21-day and longer exposure assessment is scientifically supportable 

and also provides consistency across the OPs.

The acute aggregate dietary exposure for food and drinking water were below HED level of 

concern for U.S. population and all population subgroups. The steady state aggregate dietary

(food and drinking water) exposure estimates are above HED’s level of concern for the U.S.

population and all population subgroups. The acute critical exposure contribution (CEC) 

analysis shows that drinking water is the driver. Drinking water PRZM/EXAMS time series 

for dicrotophos were based on 3 cotton scenarios. 

X. Conclusions

These unrefined analyses demonstrate that the requested uses for dicrotophos will not result in 

acute dietary risk estimates that exceed HED’s level of concern for any of the regulated 

population subgroups, including those comprised of infants and children. However, the steady 

state dietary exposure estimates are above HED’s level of concern for the U.S. population and all 

population subgroups. 

XI. List of Attachments

Attachment 1: Example Acute (Food + Drinking Water) Residue Input File

Attachment 2: Example Acute (Food + Drinking Water-PRZM-EXAM) Results File

Attachment 3: Example Steady State (Food + Drinking Water-PRZM-EXAM) with Steady State

Endpoint Results File with Calendex
Page 18 of 20

Attachment 1: Example Acute (Food + Drinking Water) Residue Input File

Filename: C:\Documents and Settings\tmorton\My Documents\MyFiles\DEEM Files\035201 

Dicrotophos\2013 Working Files USE THESE\035201 Acute MS Cotton Max Rate.R08

Chemical: Dicrotophos

RfD(Chronic): .0003 mg/kg bw/day NOEL(Chronic): 0 mg/kg bw/day

RfD(Acute): .0007 mg/kg bw/day NOEL(Acute): 0 mg/kg bw/day

Date created/last modified: 02-06-2013/06:53:57 Program ver. 3.16, 03-08-d

-----------------------------------------------------------------------------------

RDL indices and parameters for Monte Carlo Analysis:

Index Dist Parameter #1 Param #2 Param #3 Comment

 # Code 

----- ---- ------------ -------- -------- -------

 1 6 DrinkingWaterDicrotophosMScottonMaxRate Parent Only.rdf

 EPA Crop Commodity Name Def Res Adj.Factors RDLComment

 Code Grp (ppm) #1 #2 Pntr

---------- ---- ------------------------------- ---------- ------ ------ --- -------

2003128000 20C Cottonseed, oil 0.200000 1.000 1.000 

2003128001 20C Cottonseed, oil-babyfood 0.200000 1.000 1.000 

8601000000 86A Water, direct, all sources 0.012600 1.000 1.000 1 

8602000000 86B Water, indirect, all sources 0.012600 1.000 1.000 1 

Attachment 2: Example Acute (Food + Drinking Water-PRZM-EXAM) Results File

U.S. EPA Ver. 3.16, 03-08-d

DEEM-FCID ACUTE Analysis for DICROTOPHOS NHANES 2003-2008 2-Day

Residue file: 035201 Acute MS Cotton Max Rate.R08 Adjustment factor #2 NOT used.

Analysis Date: 02-06-2013/07:05:23 Residue file dated: 02-06-2013/06:53:57

RAC/FF intake summed over 24 hours

MC iterations = 1000; MC list in residue file; MC seed = 50; RNG = MS VB

Run Comment: ""

===============================================================================

Summary calculations--per capita:

 95th Percentile 99th Percentile 99.9th Percentile

Exposure % aRfD Exposure % aRfD Exposure % aRfD 

 ---------- -------- ---------- -------- ---------- --------

Total US Population:

 0.000047 6.72 0.000132 18.84 0.000360 51.40 

All Infants:

 0.000103 14.67 0.000362 51.64 0.001037 148.14 

Children 1-2:

 0.000076 10.91 0.000214 30.60 0.000547 78.09 

Children 3-5:

 0.000071 10.19 0.000181 25.90 0.000468 66.88 

Children 6-12:

 0.000052 7.47 0.000145 20.77 0.000333 47.64 

Youth 13-19:

 0.000037 5.34 0.000107 15.27 0.000287 40.98 

Adults 20-49:

 0.000045 6.43 0.000127 18.13 0.000340 48.61 

Adults 50-99:

 0.000042 6.05 0.000117 16.77 0.000309 44.12 

Female 13-49:

 0.000044 6.32 0.000126 17.94 0.000343 49.06 

 

 
Page 19 of 20

Attachment 3: Example Acute (Food + Drinking Water-PRZM-EXAM) with Steady State

Endpoint Results File with Calendex

CALENDEX-FCID Analysis for STEADY STATE WITH TX COTTON MAX RATE GEN POP

 

Analysis Date 02-27-2013/13:38:13/0

Exposure analysis for 3 combined weeks: starting on day 1

Exposure amounts adjusted for body weight

Dietary Residue file: C:\Documents and Settings\tmorton\My Documents\MyFiles\DEEM 

Files\035201 Dicrotophos\2013 Working Files with New Version 914\Steady State with TX 

Cotton Max Rate.R08 Last saved: 2/6/2013 6:57:41 AM

Dietary Adjustment factor #2 used.

Dietary Matching File not used.

No non-dietary (residential) analysis

PRZM-EXAMS file: C:\Documents and Settings\tmorton\My Documents\MyFiles\DEEM Files\035201 

Dicrotophos\2013 Working Files with New Version 914\dicrotophos TX cotton max parent 

only1961 deleted.PE1 Last saved: 1/23/2013 7:03:28 AM

 PE Analysis applied to Direct Water 

 PE Analysis applied to Indirect Water

RfD Oral = 0.0003 mg/kg-BodyWt/day

Est'd max exposure: Oral = 100 mg/kg-BodyWt/day

MC iterations = 5 MC seed = 50 RNG = Microsoft VB

NHANES Stat Wghts used.

Analyst Comments:

-------------------------------------------------------------------------------

Population parameters: Ages 0 to 100 All Seasons

All Regions Sex: M F-all 

All Races

Nursing Status: Nursing and Non-Nursing

Summary calculations (mg/kg-BodyWt/day, per capita):

 Mean 95th Percentile 99th Percentile 99.9th Percentile

 Exposure % of RfD Exposure % of RfD Exposure % of RfD Exposure % of RfD

---------- --------- ---------- --------- ---------- --------- ---------- ---------

Dietary Exposure

 0.000005 2 0.000096 32 0.000100 33 0.000101 34

PRZM-EXAMS Water Exposure

 0.000000 0 0.000000 0 0.000000 0 0.000000 0

Dietary + PRZM-EXAMS Water Exposure

 0.000005 2 0.000096 32 0.000100 33 0.000101 34

===============================================================================

===============================================================================

 ver. 9.14, 03-08-d

CALENDEX-FCID Analysis for STEADY STATE WITH TX COTTON MAX RATE GEN POP

 

Analysis Date 02-27-2013/13:38:36/0

Exposure analysis for 3 combined weeks: starting on day 2

Exposure amounts adjusted for body weight

Dietary Residue file: C:\Documents and Settings\tmorton\My Documents\MyFiles\DEEM 

Files\035201 Dicrotophos\2013 Working Files with New Version 914\Steady State with TX 

Cotton Max Rate.R08 Last saved: 2/6/2013 6:57:41 AM

Dietary Adjustment factor #2 used.

Dietary Matching File not used.

No non-dietary (residential) analysis

PRZM-EXAMS file: C:\Documents and Settings\tmorton\My Documents\MyFiles\DEEM Files\035201 

Dicrotophos\2013 Working Files with New Version 914\dicrotophos TX cotton max parent 

only1961 deleted.PE1 Last saved: 1/23/2013 7:03:28 AM

 PE Analysis applied to Direct Water 

 PE Analysis applied to Indirect Water
Page 20 of 20

RfD Oral = 0.0003 mg/kg-BodyWt/day

Est'd max exposure: Oral = 100 mg/kg-BodyWt/day

MC iterations = 5 MC seed = 50 RNG = Microsoft VB

NHANES Stat Wghts used.

Analyst Comments:

-------------------------------------------------------------------------------

Population parameters: Ages 0 to 100 All Seasons

All Regions Sex: M F-all 

All Races

Nursing Status: Nursing and Non-Nursing

Summary calculations (mg/kg-BodyWt/day, per capita):

 Mean 95th Percentile 99th Percentile 99.9th Percentile

 Exposure % of RfD Exposure % of RfD Exposure % of RfD Exposure % of RfD

---------- --------- ---------- --------- ---------- --------- ---------- ---------

Dietary Exposure

 0.000005 2 0.000096 32 0.000100 33 0.000101 34

PRZM-EXAMS Water Exposure

 0.000000 0 0.000000 0 0.000000 0 0.000000 0

Dietary + PRZM-EXAMS Water Exposure

 0.000005 2 0.000096 32 0.000100 33 0.000101 34

===============================================================================

===============================================================================