UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: September 15, 2015 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Dicrotophos: Response to Comments on the Human Health Risk Assessment for 

Registration Review of Dicrotophos. 

PC Code: 035201 

Decision No.: 497854 

Petition No.: NA 

Risk Assessment Type: Human Health Risk Assessment 

TXR No.: NA 

MRID No.: NA 

FROM: Thurston G. Morton, Chemist, RAB IV 

Wade Britton, Biologist, RAB IV 

Health Effects Division (7509P) 

DP Barcode: 424292 

Registration No.: NA 

Regulatory Action: Reg Review 

Case No.: 0 145 

CAS No.: 14 1-66-2 

40 FR: §I 80.299 

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TO: Khue Nguyen and Neil Anderson 

Risk Management and lmplementation Branch 1 

Pesticide Re-Evaluation Division (PRD) (7508P) 

Page 1 of 4 
AMVAC's Response to EPA's Preliminary Drinking Water Exposure and Acute and Steady State 

Aggregate Dietary Risk Assessments for Dicrotopbos 

./. 1.2 EPA memorandum of July 10, 2014: (PC Code: 035201,· DP BarcodeD418103); 

"Dicrotophos: Acute and Steady State Aggregate Dietmy (Food and Drinking Water Exposure and 

Risk Assessments to Support Registration Review", by Thurston Morton (Chemist) Risk Assessment 

Branch IV. Health Effects Dhiision (7509?). 

I. Within the "Executive Summary" section, "Steady State Dietary (Food and Drinking Water) Exposure 

results and Characteri zation'', 2nd pp., EPA states, "An unrefined 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 I 00% crop treated. 

The steady state aggregate dietary exposure estimates from Calendex are above RE D's level of concern(> 

I 00% of the PAD) for the U.S. population and all population subgroups. Combined dietary exposure from 

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

2 years, the most highly exposed population subgroup." 

AMV AC's comment: We have already confirmed with EPA that these values are in error and the highest 

exposed subpopulation group is the all infants (< I year old). The combined dietary exposure from food 

and drinking water at the 95th percentile for the U.S. population ranges from 66 to 92% of the PAD, 

which does not exceed RED's level of concern. The combined dietary exposure from food and drinking 

water at the 95•h percentile for the all infants (<I year old) population subgroup ranges from 120 to 210% 

of the PAD, wh ich exceed RED's level of concern. As EPA has indicated, these exceedances result in a 

slight overestimation of exposure as the assessment assumes tolerance level residues and I 00% crop 

treated. Also, water exposure is based on a screening level assessment of surface water exposure using 

PRZMIEXAMS that can be refined as indicated previously in this document. 

H ED Response: This error will be corrected in the revised dietary exposure assessment memorandum. 

2. Within the "IV. Drinking Water Data" section, I st pp., EPA states, "This assessment uses maximum 

rates but considers typical rates though monitoring data exceeds the resulting EDWCs in some instances." 

AMV A C's comment: The only EDWC exceedance of which we are aware is the single NA WQA 

sample finding of 6.83 ppb out of a database of 8,500 samples. These findings, especially when 

considered on the basis a statistical distribution would indicate that the PAD would not be exceeded or at 

most only at a probabilistic level exceeding the 99 .91

" percentile. 

HED Response: This comment is under the purview of EFED. 

3. Within the "IV. Drinking Water Data" section, I st pp., EPA states, "The assessment considers a parent 

only approach but also considers the major degradates as parent in a total toxic residue (TRR) approach." 

AMVAC's comment: Within our comments to the EPA memorandum of July I 0, 2014: (PC Code: 

035201; DP Barcode 393772); "Dicrotophos: Drinking Water Assessment for Reregistration Review". by 

Andrew Shelby (Physical Scientist) Environmental Risk Branch 6, we explained our views for proposing 

that the total toxic residue definition be redefined to exclude metabolites/degradates that do not maintain 

an organophosphate based structural functionality. On this basis, the EDWC exceedanccs overstate 

exposure. 

H ED Response: This comment is under the purview of EFED. 

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4. Within the ''Drinking Water Data" section, I st pp., EPA states, "Given current uncertainty, he 

following degradates are included in the lTR approach:" 

AMV A C's comment: The referenced infonnation is not provided. 

HED Response: This error will be corrected in the revised dietary exposure assessment memorandum. 

5. Within the "VI. CALENDEX-DCID Program" section, 2nd pp., EPA states, "RED'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 2 1-day duration. In the Calendex, 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 drin king water residue file." 

AMVAC's comment: Although the process being used by RED represents a reasonable initial screening 

approach. the availability of a large surface water monitoring database that includes targeted sampling 

provides an opportunity for refining the water exposure based and aggregate risk assessments. 

HED Response: This comment is under the purview of EFED. 

6. Within the "VIII. Results/Discussion" section, 2nd pp., EPA states, "For food and drinking water, the 

acute dietary risk estimate is below RED's level of concern at the 99.91h percentile of exposure. The acute 

dietary exposure using DEEM was estimated for the U.S. population is 13% of the aPAD and 27% 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 RE D'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." 

AMVAC's comment: Based on conversations with EPA, we have conftnned that the information within 

this text is incorrect and refers to that of another chemical. 

HED Response: This error will be corrected in the revised dietary exposure assessment memorandum. 

7. Within the "IX. Characterization of Inputs/Outputs" section, I st pp., EPA states, "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 period (i.e. 15 days) than 21 days, exposure assessments of 2 1 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 2 1-day and longer exposure assessment is scientifically 

supportable and also provides consistency across the OPs." 

AMV AC's comment: Based on conversations with EPA, we have con finned that the infonnation within 

this text is incorrect and refers to that of another chemical. 

HED Response: This error will be corrected in the revised dietary exposure assessment memorandum. 

8. Within the "X. Conclusions" section, I st pp., EPA states, "these unrefined analyses demonstrate that 

the requested uses for dicrotophos will not result in acute dietary risk estimates that exceed HED's level of 

Page 3 of 4 
concern for any of the regulated population subgroups. including those comprised of infants and 

children." 

AMVAC's comment: The acute dietary risk estimates at the 9Sth percentile does not exceeds the aPAD 

for any of the subpopulation groups. This would indicate that acute aggregate exposure would not of 

concern. 

HEO Response: This error will be corrected in the revised dietary exposure assessment memorandum. 

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