UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

PC Code: 084001 

MEMORANDUM 

Date: 

Subject: Registration Review - Preliminary problem formulation for the Ecological Risk 

Assessment of Dichlorvos (DDVP) 

To: Joy Schnackenbeck 

Special Review and Reregistration Division 

From: Christina Wendel, Biologist s/rqlog 

Lucy Shanaman, hemi is* -2LA-4 7%- L&+ f&qsq 

Environmental Fate and Effects Division 

Through: 'Tom ~aile~, w ranch chief* 6 $-S,#E> WfV9? 

Environmental Risk Branch 2 

Environmental Fate and Effects Division 

Office of Pesticide Programs 

Attached is the preliminary problem formulation for the ecological risk assessment to be 

conducted as part of the Registration review of the insecticide DDVP. 

TEXT SEARCHABLE DOCUMENT 2009
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDW 5/14/2009 

ECOLOGICAL RISK ASSESSMENT 

PROBLEM FORMULATION FOR: 

Dichlorvos (DDVP) 

Christina Wendel, Biologist 

Lucy Shanaman, Chemist 

Environmental Risk Branch 2 

Tom Bailey, Branch Chief 

Environmental Risk Branch 2 

Environmental Fate and Effects Division 

Office of Pesticide Programs 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DD W 5/14/2009 

STRESSOR SOURCE AND DISTRIBUTION 

Dichlorvos (2,2-Dichlorovinyl dimethyl phosphate), also known as DDVP is an insecticide 

belonging to the organophosphate class of pesticides. Organophosphate toxicity is based on the 

inhibition of the enzyme acetylcholinesterase, which cleaves the neurotransmitter acetylcholine. 

Inhibition of acetylcholinesterase by organophosphate insecticides interferes with proper 

neurotransmission in cholinergic neurosynapses and neuromuscular junctions. 

DDVP was originally registered for use in the United States in 1948. Target pests are flies, 

gnats, mosquitoes, chiggers, ticks, cockroaches and other nuisance insect pests. Current labeled 

usage of DDVP includes agricultural sites (e.g. mushroom houses); commercial, institutional and 

industrial sites; and domestic use in and around homes (i.e., resin strips). It is also registered for 

treatment of cattle, poultry, and swine. DDVP is not registered for direct use on any field grown 

commodities. DDVP is applied with aerosols, fogging equipment, spray equipment, and through 

use of impregnated materials such as resin strips which result in slow release of the pesticide. 

DDVP is closely related to the pesticides naled and trichlorfon. Naled and trichlofon both 

metabolize or degrade to DDVP in the environment. 

The risk assessments available in the docket, and which serve as the basis for this problem 

formulation, include the following: 

Dichlorvos: Interim Reregistration Eligibility Decision - Environmental Fate and 

Effects Division's Response to Public Comments (1 211 012007). 

Revised EFED Risk Assessment for the Dichlowos Reregistration Eligibility 

Document (612212005). 

EFED Response to Registrant's Error Correction Comments on Dichlowos RED 

(6/22/2005). 

EFED Response to Public Comments on Dichlorvos Ecological Risk Assessment 

(8/3 112006). 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DD W 5/14/2009 

ECOLOGICAL EFFECTS 

The purpose of this problem formulation is to provide an understanding of what is known about 

the environmental fate and ecological effects of the registered uses of DDVP. As described in 

the Agency's Overview Document (U.S. USEPA, 2004), the most sensitive endpoint for each 

taxa is evaluated. Assessment endpoints include direct toxic effects on the survival, 

reproduction, and growth of terrestrial and aquatic life, as well as indirect effects, such as 

reduction in prey base andlor modification of habitat. This problem formulation evaluates 

current information regarding DDVP use effects on taxa including freshwater fish and aquatic 

invertebrates, estuarine marine fish and invertebrates, birds, mammals, terrestrial invertebrates, 

terrestrial plants, and algae. 

Acute (short-term) and chronic (long-term) toxicity information is characterized based on 

registrant-submitted studies and a comprehensive review of the open literature on DDVP. Other 

sources of information include review of the Ecological Incident Information System (EIIS). A 

summary of the available ecotoxicity information and the incident information for DDVP are 

provided below. \ 

Table 1 and Table 2 summarize the most sensitive ecological toxicity endpoints based on an 

evaluation of both the submitted studies and the open literature, as previously discussed. These 

endpoints are deemed applicable to this problem formulation for registration review. 

A brief summary of submitted and open literature data considered relevant to this ecological risk 

assessment is presented below. 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDVP 5/14/2009 

Table 1. Applicable DDVP measurement endpoints and values for use in RQ calculations 

Abundance (i.e., 

survival, 

reproduction, and 

growth) of 

individuals and 

populations of birds 

Abundance (i.e., 

survival, 

reproduction, and 

growth) of 

individuals and 

populations of 

mammals 

Survival of 

beneficial insect 

populations 

Survival and growth 

of terrestrial plants 

Mallard duck MRID # 

Avian (single dose) (Anas LD50 = 7.78 mg/kg ~~~~~

001 60000 

acute oral LDS0 platyrhynchos) ai (Hudson et al. 

1984) 

Avian subacute LCro = 568 mglkg Acceptable MRID # 

8-day dietary LC50 (Phasianus ai 00022923 (Hill 

colchicus) et al. 1975) 

Mallard Duck MRID # 

Avian reproduction (Anas NOAEC = 5 mdkg Acceptable 44233401 

NOAEL . platyrhynchos) ai (diet) (Redgrave and 

Mansell 1997) 

Mammalian acute 

oral (single dose) Laboratory Rat LD50 = 56 mglkg ai 

LD5o (Rattus (female) Supplemental 

nowegicus) 

Mammalian acute 

inhalation toxicity 

LC50 

Mammalian 

reproductive 

NOAEC or NOAEL 

Honey bee acute 

contact 

Laboratory Rat 

(Rattus ' mgiL Supplemental ai nowegicus) 

Laboratory Rat 

1 (Rattus 

NOAEC = 20 

mgkg ai (diet) Supplemental 

novvegicus) 

Honey bee LDso = 0.495 

(Apis mellifera) pglbee ai Acceptable 

MRID # 

0005467 

MRID # 

00137239 

Acc. # 010174 

MRID # 

424839001 

I I I I 

Seedling emergence I 

EC25 

Seedling emergence 

No Data No Data No Data Data Gap 

EC25 

Vegetative vigor I NOAEC 

LD50 = Lethal dose to 50% of test population 

NOAEC = No observed adverse effect concentration 

LOAEC = Lowest observed adverse effect concentration 

LC5o = Lethal concentration to 50% of the test population 

EC5dECzs = Effect concentration to 50%/25% of the test population 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDW 5/14/2009 

Table 2. Applicable DDVP measurement endpoints and values for use in RQ calculations 

Freshwater fish acute 

freshwater fish Freshwater fish early NOAEC = 5.2 ppb 

ECSo = 0.07 ppb ai 

Freshwater invertebrate NOEAC = 0.0058 

reproductive NOAEC 43890301 Ward 

= 7350 ppb ai 

individuals and 

communities of 

estuarine and marine 

Estuarine and marine NOAEC = 960 

Estuarine and marine 

invertebrate acute = 19.1 ppb ai 

individuals and 

communities of 

NOAEC = 1.48 

Standing crop or 

biomass and growth of 

aquatic plants 

LD5a = Lethal dose to 50% of test population 

NOAEC = No observed adverse effect concentration 

LOAEC = Lowest observed adverse effect concentration 

m50 = Lethal concentration to 50% of the test population 

EC5dEC25 = Effect concentration to 50%/25% of the test population 

Freshwater green 

algae, cyanobacteria or 

diatom 96-h IC50 for 

biomass. 

Freshwater green 

algae, cyanobacteria or 

diatom 96-h NOAEC 

(or ECo5) for biomass 

*lgae 

(unknown 

species) 

48 hr ECsO = 14000 

ppb ai Supplemental 

MFUD # 

40228401 (U.S. 

EPA, F.L. Maya 

1986) 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DD W 5/14/2009 

There have been 7 incidents related to DDVP reported in the Environmental Incident 

Information System (EIIS) database (reported to the Agency fiom 1991 to 2002). Of these 7 

incidents, 4 were of undetermined use, and 3 were registered uses. 

Avian Incidents 

Six of the incidents were terrestrial, with 5 related to bird kills. One incident involved an avian 

outdoor exposure from a site (apples) for which DDVP was never registered. Two bluebird 

chicks died in their nest box in the town of Redhook New York. The nest was within 300 yards 

of an apple orchard. The cause of death was DDVP poisoning (reported by: Wildlife Pathology 

Unit, NY State Dept. Of Environmental Conservation Annual Report 1/1/94 -513195. Ward 

Stone, Wildlife Pathologist. 1994 incident). Another incident involved a registered use of DDVP 

crystals in treated feed that resulted in 8 mallard ducks dying in an agricultural area. Afiother 

incident involved an avian exposure resulting fiom an undetermined use of DDVP in British 

Columbia, Canada. The red tailed hawk was incapacitated as a result of secondary poisoning by 

DDVP (1 1/16/97). The last two incidents involved the use of DDVP in the home residence 

resulting in canary deaths (6 total deaths). 

Mammalian Incidents 

There is one mammalian incident reported involving indoor exposure to animals. Amvac 

Chemical Corp. (Letter to Agency Dated 7/3/95) reported potential adverse effects exposure 

relating to a pest strip in which several exotic and wild native and non-native animals that 

included skunks and several fennec foxes (native of Egypt) were in a room of roughly 4000 

cubic feet. The room had a pest strip placed in it 3-4 days previously to control insects. The pest 

strip was labeled as covering 1000 cubic feet. Four fennec fox pups died. A veterinarian treated 

three other pups with atropine; two recovered. The foxes were the only animals that recovered. 

Two of the animals recovered after treating with atropine, indicating it is possible that the cause 

of poisoning was exposure to DDVP fumes. 

Aquatic Incidents 

One aquatic incident of undetermined use in Tennessee involving fish kills was reported 

affecting 3 79 organisms (species undetermined). No residue analysis was conducted. 

Currently, no systematic or reliable mechanism exists for the accurate monitoring and reporting 

of wildlife kill incidents to the Agency. oreo over, before a pesticide incident can be reported or 

investigated, the dead animals must first be found, In the absence of monitoring following 

pesticide applications, kills are not likely to be noticed in ago-environments which are generally 

away from human activity. Even if onlookers are present, dead wildlife species, particulqrly 

small song birds and mammals, are easily overlooked, even by experienced and highly motivated 

observers. Even in sparse vegetative cover, wildlife carcass detection is difficult and as 

vegetative cover increases the difficulty in detection is exacerbated. Under some circumstances 

intoxicated animals may seek heavy cover before dying which decreases the probability of 
Regrgrstration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDVP 5/14/2009 

detection further. Poisoned birds may fly from the sites, succumbing outside of the area or 

scavengers may remove carcasses before they can be observed, significantly reducing the chance 

of detection. , 

Balcomb (1 986) reported that songbird carcasses removal rate ranged fiom 62 to 92 percent in 

the first 24 hours following placement, with a mean loss at 24 hours of 75% (S.D. 2 12.4). 

Overall, by the end of the 5-day monitoring period, 72 of the 78 carcasses had been removed by 

scavengers. In addition, the number of birds per acre alone, not considering these other factors, 

makes detection of kills difficult. Best (1990) reported fiom 0.57 live birds per acre in the center 

to 2.8 live birds per acres in the perimeter of corn fields in Iowa and Illinois. Even if all the birds 

in a field were killed and remained on the field, the probability of observing carcasses, 

particularly when not systematically searching, at these densities, is not high. Research has 

shown that even when intense systematic searches are conducted by highly trained individuals 

for placed carcasses in agro-environments, recovery rates rarely exceed 50 percent (Madrigal et 

a1.1996). 

Even if dead animals are observed, they might not be reported to the Agency. Persons unfamiliar 

with the toxicity of pesticides to non-target species may fail to associate the finding with the 

pesticide application, especially if the two events are separated by several days and only a few 

birds are observed dead. Even if the association is made, the observer must be aware or have the 

motivation to find out where to report the incident. Therefore, the reporting of a few dead birds 

associated with the use of a chemical is believed to provide evidence that substantial effects may 

be occurring. 

Volatilization (1.2 x rnrn Hg) is expected to be the main route of dissipation for DDVP in 

the environment. DDVP is not expected to persist in either soil or water. DDVP is susceptible 

to both hydrolysis (tin = 5 days) and photolysis (tin = 10-17 days). DDVP also degrades in 

aerobic (til2 = 0.43 days) and anaerobic (tli2 = 6.3 days) environments. 

DDVP is expected to be mobile in the open environment. The high vapor pressure indicates that 

DDVP will dissipate primarily through volatilization. This is confirmed by two submitted 

terrestrial field dissipation studies which report that DDVP was measured in the air above the 

field test plots located in Missouri and California at 12.5% (MRID 44386701) and 89.2% (MRID 

44297701) of the total applied DDVP, respectively. The organic carbon partition coefficients 

(LC = 15-41) for DDVP predicts mobility in water. A summary of the environmental fate 

properties may be found in Table 3 below. 

Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DD~P 5/14/2009 

community water systems in a few states in 2004. In 2001, PDP analyzed 214 finished drinking 

water samples from CA and NY. In 2002 and 2003, PDP sampled 371 and 699 finished drinking 

water samples, respectively, in CA, CO, KS, NY, and TX. In 2004, PDP sampled raw and finished 

water fiom 171 community water systems fiom MI, NC, OH, OR, PA, and WA. DDVP was one of 

the analytes. No detectable residues of DDVP were found at limits of detection-(LOD) of 0.4 - 22.5 

pptrillion. Naled and trichlorfon were not among the analytes tested, but PDP would have detected 

DDVP coming fiom naled and trichlorfon. 

However, the PDP monitoring of water fiom community water systems are not completely 

reflective of the drinking water consumed by the population for the following reasons: the PDP 

samples large community water systems in a limited number of states; the sampling sites are not 

necessarily in DDVP, naled, and trichlorfon use areas, and the data may not be reflective of 

drinking water concentrations in areas of high dichlorvos use; the community water systems 

sampled by PDP are generally deep ground water or surface water systems; and the PDP does 

not sample individual, private wells. Use of the PDP data would not be protective of people 

whose drinlung water source is a private well. e 

Clean Water Act 

DDVP is not identified as a cause of impairment for any water bodies listed as impaired under 

section 303(d) of the Clean Water Act, based on information provided at 

http://oaspub.epa.gov/trndl/waters list.impairments?p impid=3. The Agency invites submission 

of water quality data for this To the extent Fossible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired Water 

Body and Other Water Quality Data in OPP's Registration Review Risk Assessment and 

Management Process (see: http://www.epa.gov/oppfeadl /cb/p~dc/2006/november06/session1- 

sop.~df), in order to ensure they can be used quantitatively or qualitatively in pesticide risk 

assessments. 

For DDVP and pesticides in general, the ecosystems at risk are those in close proximity to the 

use areas. These would include the DDVP use sites and the surrounding terrestrial habitats, and 

water bodies directly adjacent to treated areas (e.g. feedlots) that may receive chemical residues 

via drift, volatilization, or runoff. Within water bodies, the water column, sediment, and pore 

water are all compartments of concern; however, grven DDVP's solubility it is most likely to be . found in the water column. 

Organisms of potential concern broadly include birds, mammals, reptiles, fish, amphibians, and 

terrestrial and aquatic invertebrates, plants, beneficial insects, and amphibians. 

The assessment endpoints are intended to reflect population sustainability and community 

structure within ecosystems and hence relate back to ecosystems at risk. If risks are expected for 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Inseciicide DDVP 5/14/2009 

given speciesltaxa based on the screening-level assessment, then risks might be expected to 

translate to higher levels of biological organization. 

The predominate uses of DDVP in California (the only usage data available to the Agency) were 

the impregnated pest strip and structural pest control. Table 4 gives estimates of DDVP usage in 

California. The uses of DDVP which may pose a potential risk to terrestrial and aquatic 

organisms would be insect control on dairy and beef cattle. Table 5 gives estimates of DDVP 

use on dairy cattle for 1999,2001, and 2006 and Table 6 gives estimates of DDVP use on beef 

cattle for 1997 and 1999. DDVP use on dairy cattle and beef cattle appears to have decreased. 

I I CHICKEN 1 45.20 1 59.15 1 I 

COMMODITY FUMIGATION 

DATE 

254.84 

47.71 

607.91 

1,760.90 

1.464.28 

FOOD PROCRESSING PLANT 

FUMIGATION, OTHER 

LANDSCAPE MAINTENANCE 

POULTRY 

REGULATORY PEST CONTROL 

I STRUCTURAL PEST CONTROL I I I 

1 1.775.58 1 1,974.86 1 1.491.48 I 

370.56 

533.87 

59.30 

230.49 

23.52 

1.77 

RESEARCH COMMODITY 

RIGHTS OF WAY 

STORAGE AREAIBOX 

Prepared: November 7,2008 

Cal DPR Data: http://www.cdpr.ca.gov/docs/pur/purmain.htm 

Empty cells indicate no available usage. 

549.50 

114.89 

619.19 

13.77 

22.60 

16.39 

23.11 

1.25 

59.67 

VERTEBRATE CONTROL 

Chemical Total 

19.69 

24.22 

30.21 

3.807.15 

Table 5. DDVP Use on Dairy Cattle and Dairy for 1999,2001,2006 

Dairy Cattle 

Year 1 National Use I RateIhead~Year 

1999 

2001 

2006 

13.17 

4,898.19 

Number cattle ( Oh Cattle treated 

14.80 

6.527.38 

(lb) 

96,200 

9,000 

4,900 

(lb) 

0.25 

0.03 

0.01 

treated 

384,800 

300,000 

245,000 

4.2 

3.3 

2.7 
Regisfration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDW ' 5/14/2009 

Assessment endpoints are defined as "explicit expressions of the actual environmental value that 

is to be protected." Defining an assessment endpoint involves two steps: 1) identifjing the 

valued attributes of the environment that are considered to be at risk; and 2) operationally 

defining the assessment endpoint in terms of an ecological entity (i.e., a community of fish and 

aquatic invertebrates) and its attributes (i.e., survival and reproduction). Therefore, selection of 

the assessment endpoints is based on valued entities (i.e., ecological receptors), the ecosystems 

potentially at risk, the migration pathways of pesticides, and the routes by which ecological 

receptors are exposed to pesticide-related contamination. The selection of clearly-defined 

assessment endpoints is important because they provide direction and boundaries in the risk 

assessment for addressing risk management issues of concern. Changes to assessment endpoints 

are typically estimated from the available toxicity studies, which are used as the measures of 

effects to characterize potential ecological risks associated with exposure to a pesticide, such as 

DDVP. 

Table 6. DDVP Use on Beef Cattle for 1997 and 1999 

Beef Cattle 

To estimate exposure concentrations, the ecological risk assessment considers a single 

application at the maximum application rate to fields that have vulnerable soils. The most 

sensitive toxicity endpoints are used from surrogate test species to estimate treatment-related 

direct effects on acute mortality and chronic reproductive, growth and survival assessment 

endpoints. Toxicity tests are intended to determine effects of pesticide exposure on birds, 

mammals, fish, terrestrial and aquatic invertebrates, and plants. These tests include short-term 

acute, sub-acute, and reproduction studies and are typically arranged in a hierarchical or tiered 

system that progresses from basic laboratory tests to applied field studies. The toxicity studies 

are used to evaluate the potential of a pesticide to cause adverse effects, to determine whether 

further testing is required, and to determine the need for precautionary label statements to 

minimize the potential adverse effects to non-target animals and plants. 

Year 

1997 

1999 

DDVP is classified as very highly toxic to birds on an acute oral basis, moderately toxic to birds 

on a sub-acute dietary exposure basis, and is classified as moderately toxic to mammals on an 

acute oral exposure basis. It is also highly toxic to the honey bee on an acute basis. Indirect 

effects on species consuming these animals are also possibly a concern due to loss of prey base. 

DDVP is very highly toxic to both freshwater and in marinelestuarine invertebrates on an acute 

exposure basis. It is highly toxic to freshwater fish and moderately toxic to marinelestuarine fish 

on an acute basis. Chronic effects in aquatic animals include reduced survival (freshwater and 

estuarinelmarine fish), reproduction (freshwater invertebrates), and growth (fi-eshwater and 

estuarinelmarine invertebrates and estuarinelmarine fish). 

Site 

Beef Cattle 

Beef Cattle 

National 

Use 

(Ib) 

32,700 

18,700 

Rate I head I yr 

Qb) 

0.01 

0.01 

Number of 

Cattle treated 

3,270,000 

1,870,000 

% Cattle treated as 

percentage of all 

insecticides used 

9.5 

5.5 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDVP 5/14/2009 

In order for a chemical to pose an ecological risk, it must reach ecological receptors in 

biologically significant concentrations. An exposure pathway is the means by which a pesticide 

moves in the environment fi-om a source to an ecological receptor. For an ecological exposure 

pathway to be complete, it must have a source, a release mechanism, an environmental transport 

medium, a point of exposure for ecological receptors, and a feasible route of exposure. 

The conceptual model (Figure 1) depicts the potential pathways for ecological risk associated 

with DDVP use. The conceptual model provides an overview of the expected exposure routes 

for organisms within the DDVP action area. The focus of this model is application via spray 

(aerial and ground). 

Based on an examination of the physical/chemical properties of DDVP, the fate and disposition 

in the environment, and method of application, a conceptual model was developed that 

represents the possible relationships between the stressor, ecological receptors, and the 

assessment endpoints. The major transport pathway for DDVP is expected to be volatilization. 

While DDVP is also expected to be mobile in water, short laboratory half-life values in soil and 

water, along with a high vapor pressure, will allow volatilization to dominate as the main route 

of dissipation in the open environment. 
Registration Review 

Ecologicnl Risk Assessment 

Problem Formulation for the Insecticide DDW 5/14/2009 

FIGURE 1. ECOLOGICAL CONCEPTUAL DIAGRAM FOR DDVP 

TRANSPORT 

EXPOSURE 

ROUTE 

1 RECEPTORS 

Application of Dichlorvos (DDVP) via Sprayer, Mister or Fogger 

--------3----------- 

) Leach~ng (Infiltrat~on) I Percolabon I I I-- - - ---- ---,---, - ---, 

,--- L ----- 

+ - - - - 4 Groundwater I 1 --------- J 

Populabon lnd~v~dual 

Reduced Invertebrates, 

Populat~on Vertebratks 

Growth Reduced Su~~val, 

Growth, - Re~roduct~on 

In Registration Review, pesticide ecological risk assessments will follow the Agency's 

Guidelines for Ecological Risk Assessment, u;ill be consistent with the paper titled "Overview of 

the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental 

Protection Agency" ("Overview Document") (January 2004), and will be done in accordance 

with Section 7 of the Endangered Species Act. 

Previously completed screening level risk assessments and exceedances of Agency levels of 

concern indicate a need to further examine and refine acute risk to terrestrial animals. Analysis 

of potential indirect effects on listed species is also required. This analysis plan will be revisited 

and may be revised depending upon the data available in the open literature and the information 

submitted by the public in response to the opening of the Registration Review docket. 

DDVP's fate characteristics, results of toxicity data, and use pattern including multiple outdoor 

applications to cattle suggests potential risk concerns to terrestrial and aquatic organisms. The 

range of potential exposure of DDVP to non-target organisms can vary greatly based on the 

application method, number of applications applied, application intervals, and number of cattle 

treated. 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDW 5/14/2009 

The registered uses of DDVP, which suggest a potential risk concern to terrestrial and aquatic 

organisms, would be insect control on dairy and beef cattle. All other uses are indoor uses or 

spot treatments. The method of spray application varies widely with varying degrees of potential 

exposures. In the case of dairy herds, smaller herds are most likely treated as a group rather than 

individually by small hand held sprayers (Thomas 2007), larger operations favor automated 

systems that trigger sprays as animals enter or exit the milking parlor. The most effective 

method of application in large beef cattle operations is the mist blower (Holscher 2007); 

however, other application methods include foggers, hydraulic spryer handguns and back 

rubbers. The Agency's analysis indicates that when DDVP is used, it is applied in 

approximately 37 applications per year (Pest Management Strategic Plan for Lactating (Dairy) 

Cattle - North Central Region, 2004). The frequent use suggests that when a herd is treated, 

such treatment is often done on a daily or every-other-day basis during the part of the season 

insects are present. With regard to the exposure variation associated with the number of cattle 

treated, the Agency's analysis indicate that of states reporting DDVP usage on dairy cattle, the 

average herd size ranges from 44 to 800 head per dairy operation with a national average herd 

size of 126. Beef cattle herd sizes range from less than 6 to more than 4,539 head per bleef 

operation with a national average herd size of 43 head. On a feedlot, there is a range of 174 - 622 

headlacre. 

Based on DDVP's use patterns, there are uncertainties associated with potential; 1) risks to 

passerine birds, 2) inhalation risks to birds; 3) risks to terrestrial and aquatic plants; and 4) risk to 

aquatic organisms with DDVP use on beef and dairy cattle. 

In addition, given that volatilization is potentially a major route of dissipation for DDVP, there is 

a need to assess the volatility associated with DDVP use. Also, available toxicity data indicate 

that DDVP is very highly toxic to avian species on an acute oral basis and is classified as 

category I1 for acute inhalation toxicity to mammals. In order to fbrther understand the volatility 

of DDVP in the field and laboratory, as well as determine any toxicological responses, volatility 

and acute avian inhalation studies are being requested. The acute avian inhalation study and 

volatility data will be used to assess potential acute risks associated with avian inhalation. 

Due to DDVP's use pattern, specifically the outdoor insecticidal use on dairy and beef aattle, 

there is a potential risk to non-target terrestrial and aquatic plants. Currently, there is na 

acceptable data conducted with DDVP on terrestrial or aquatic plants. Terrestrial and aquatic 

plant toxicity data would assist in the evaluation of potential plant risks associated with DDVP 

use. 

Due to the potential for DDVP to volatilize there is some uncertainty regarding the exposure of 

DDVP to the aquatic environment and subsequent potential risks to aquatic organisms. A quick 

screen of the potential exposure to DDVP in surface water indicate that the potential EECs for 

aquatic exposure are greater than some toxicity endpoints identified in available fish and aquatic 

invertebrate studies. This screen, however, did not consider volatility. During registration 

review, aquatic risks will need to be assessed with a Tier 2 model whch addresses the potential 

volatility of a compound. The application of DDVP for each animal was derived after review of 

the label (The insecticide is 10 lblgal DDVP = 100% solution, dilute with 99 gal of water to get a 

1 % treatment solution and you have 12,800 fl oz which contains 10 lbs of DDVP or 0.000781bs 
Registration Review 

Ecological Risk Assessmerzt 

Problem Formulution for the Insecticide DDW 5/14/2009 

DDVPIfl oz. Each animal is treated with 2 fl oz. therefore; each animal is treated with 0.0015 

lbs. of DDVP). Also, degradate information for DDVP is limited, a more through analysis of 

the following degradates, and the risk associated with them needs to be examined. Major 

degradates of DDVP are 2,2-dichloroacetic acid, 2,2-dichloroacetaldehyde, desmethyl 

dichlorvos, and glyoxylic acid 

During Registration Review, the terrestrial risks associated with DDVP use will be assessed with 

T-REX, TerrPlant and AgDRIFT. Potential aquatic risks will be assessed using with a Tier 2 

model which addresses the potential volatility of DDVP. 

If the planned ecological risk assessment indicates that DDVP exceeds the Agency's Level of 

Concern for Listed species, either directly or indirectly, a preliminary "May Affect" 

determination will be made for the affected taxa (e.g., birds, mammals, fish, invertebrates, etc). , 

A map of the DDVP use "footprint," consisting of all land cover types for whch the LOC is 

exceeded will be generated, along with a narrative description of the area outside the footprint 

where effects are expected to occur. These maps and narrative descriptions will be provided to - the U.S. Fish and Wildlife Service and the National Marine Fisheries Service (the Services) for 

them to determine which Listed species may be affected. 

The data that are needed for registration review include: 

A. Environmental Fate 

The fate date set for DDVP is complete except for the following. Field and Laboratory 

Volatility studies, which are needed because volatilization is expected to be the main route of 

dissipation for DDVP in the environment. 

83 5.14 10 Volatility -- laboratory 

835.8 100 Volatility -- field 

B. Ecological Effects 

Data Gaps 

Several toxicity studies are needed to better assess the potential risk of DDVP exposure to 

non-target organisms. The studies listed below should be submitted to increase certainty in 

the risk estimation. 

850.41 00 (1 23- 1 a) Terrestrial plant toxicity, Tier I (seedling emergence) 

850.4150 (123-la) Terrestrial plant toxicity, Tier I (vegetative vigor) 

850.5400, 850.4400 Tier 1 aquatic plant growth 

850.2100 Acute Avian, Passerine 

885.4100 Avian Inhalation, Tier I 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDW 511 412009 

The Agency will also conduct a search of the open literature to ensure that all best available 

science is utilized. The Agency uses the ECOTOX database as its mechanism for searching the 

open literature for ecological effects information. ECOTOX integrates three previously 

independent databases - AQUIRE, PHYTOTOX, and TERRETOX - into a system which 

includes toxicity data derived predominately from the peer-reviewed literature, for aquatic life, 

terrestrial plants, and terrestrial wildlife, respectively. 

The analysis plan will be revisited and may be revised depending upon the data available in the 

open literature and the information submitted by the public in response to the opening of the 

Registration Review docket. 

The Environmental Fate and Effects Division (EFED) has completed a Data Call-In (DCI) table 

for DDVP environmental fate and effects data gaps identified in registration review. The effects 

data gaps may change if relevant toxicity data are identified fiom the ECOTOX literature review. 

The attached DCI tables, which include the guideline number and study title for required data, 

also provides a rationale for requiring the data, an explanation of how the data will be used, and a 

brief description of how the data could impact the Agency's future decision-making. 

Guideline Number: 835.1410,835.8100 

Study Title: FieId and Laboratory Volatility Studies 

Rationale for Requiring the Data 

Since DDVP has a vapor pressure of (1.2 x 1 0-2 rnm Hg), it triggers the requirement for field and 

laboratory volatility studies. These studies will assist the Agency in understanding the vapors 

resulting from volatilization of DDVP as well as to what degree volatilization occurs. This study 

will help determine any biological effects in non-target organisms at some distance from the treated 

site. This is au~licable since DDVP can be used on dairv and beef cattle. I I I 

Practical Utility of the Data I 

How will the data be used? 

There are no currently available or acceptable volatility studies that track the formation and decline 

of DDVP and its degradates. These data will be used to characterize the environmental fate of 

DDVP. For quantitative exposure estimation, these data will be used to determine appropriate 

inputs for simulation modeling. 

How could the data impact the Agency's future decision-making? 

Without these required data, the fate of DDVP cannot be fully characterized. In the absence of 

acceptable data, conservative assumptions will be made. Therefore, the use of DDVP might need 

to be restricted in areas where endangered species could be exposed. The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act and could result in use restrictions for DDVP which are unnecessarily 

severe. 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDVP 

including the likelihood of potential risks to endangered species, either by direct effects or by 

indirect effects such as reducing food sources to listed predators and scavengers. Results of this 

study would be used to calculate acute risks to passerine species.fi-om exposure to DDVP and to 

identify whether current labeling is appropriate and whether fk-ther mitigation is necessary. 

How could the data impact the Agency's future decision-making? 

If the data indicate that DDVP poses a significant acute risk to passerine birds, the Agency may 

explore additional decision options to minimize the risk of DDVP to these species. If htwe 

endangered species risk assessments are performed without these data, the Agency would have to 

assume that DDVP "may affect" passerine birds directly and other endangered species indirectly 

through loss of prey. The lack of these data will limit the flexibility the Agency and registrants 

have in complying with the Endangered Species Act and could result in inappropriate mitigation 

measures. 

Guidelipe Number: Special Study 

Study Title: Acute Avian inhalation, Tier I 

Rationale for Requiring the Data 

Volatilization is potentially a major route of dissipation for DDVP. Also, available toxicity 

data indicate that DDVP is very highly toxic to avian species on an acute oral basis and is 

classified as category I1 for acute inhalation toxicity to mammals. In order to determine 

toxicological responses associated with the volatization of DDVP, an acute avian 

inhalation study is being requested 

Practical Utility of the Data --- I How will the data be used? 1 

The acute avian inhalation data are needed to asses potential acute risks to birds associated with the 

inhalation route of exposure. The data will allow the Agency to better assess the risks to these 

organisms, including the likelihood of potential risks to endangered species, either by direct effects 

or by indirect effects such as reducing food sources to listed predators and scavengers. Results of 

this study would be used to calculate acute risks to birds fi-om exposure to DDVP and to identify 

whether current labeling is appropriate and whether further mitigation is necessary. 

How could the data impact the Agency's future decision-making? 

If the data indicate that DDVP poses a significant acute risk to birds, the Agency may explore 

additional decision options to minimize the risk of DDVP to these species. If future endangered 

species risk assessments are performed without these data, the Agency would have to assume that 
Regcgcstration Review 

Ecological Risk Assessment 

Problem Formulatwn for the Insecticide DDVP 5/14/2009 

DDVP "may affect" birds directly and other endangered species indirectly through loss of prey. 

The lack of these data will limit the flexibility the Agency and registrants have in complying with 

the Endangered Species Act and could result in inappropriate mitigation measures. 

most habitats and significantly contribute to overall environmental quality, and therefore a solid 

understanding of the potential risks to plants is essential for sound environmental management. 

Since the DDVP RED was signed, the Agency has finalized its update to the data requirements in 

40 CFR Part 158. In these updated data requirements, which were promulgated on October 26, 

2007, Tier I seedling emergence (guideline 850.4100), and Tier I vegetative vigor (guideline 

850.4150) are required for terrestrial uses. DDVP is registered for terrestrial use, and therefore 

these data are required under the new 40 CFR Part 158 data requirements. 

Practical Utility of the Data 

How will the data be used? 

The data will be used to estimate potential risks to terrestrial plants, including the likelihood of 

potential risks to endangered species, either by direct effects or by indirect effects, and to reduce 

uncertainties associated with the current ecological risk assessment. By refining the assessment, 

the Agency will be able to determine whether current labeling is appropriate and whether further 

mitigation is necessary. . In the absence of Tier I data, risks to terrestrial plants will be presumed. 

How could the data impact the Agency's future decision-making? 

These data, once submitted, will allow the Agency to characterize the risk of DDVP to terrestrial 

and aquatic ecosystems. Primary producers (i.e. plants) provide oxygen, food and habitat vital to 

ecological processes. Therefore, a solid understanding of the potential risks to plants is essential 

in order to assess the environmental risks the use of DDVP may pose. If the data indicate that 

DDVP poses significant risks to these plant species, the Agency may explore additional decision 

options to minimize the risks to these species. 

The lack of these data will limit the flexibility the Agency and registrants have in complying with 

the Endangered Species Act and could result in use restrictions for DDVP which may otherwise be 

avoided, or which are unnecessarily severe. 

Guideline Number: 850.4400,850.5400 

Study Titles: Tier 1 aquatic plant growth 

Rationale for Requiring the Data 

DDVP toxicity data for vascular and non-vascular aquatic plants are not available. Tier 1 aquatic 

plant toxicity data would provide enough data to screen for potential $quatic plant risks associated 

with DDVP use. Plants form the basis of most habitats and significantly contribute to overall 

environmental quality, and therefore a solid understanding of the potential risks to aquatic plants is 

essential for sound environmental management. 

I Since the DDW RED was signed, the Agency has finalized its update to the data requirements in I 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDP 5/14/2009 

imate potential risks to aquatic vascular and non-vascular plants, 

indirect effects, and to reduce uncertainties associated with the current ecological risk assessment. 

By refining the assessment, the Agency will be able to determine whether current labeling is 

appropriate and whether further mitigation is necessary. In the absence of Tier I data, risks to both 

vascular and non-vascular aquatic plants will be presumed. 

How could the data impact the Agency's future decision-making? 

Because aquatic vascular and non-vascular plants form the basis of the food chain for aquatic 

habitats and significantly contribute to overall water quality, a solid understanding of the potential 

risks to aquatic plants is essential for sound environmental risk management decision-making. 

These data, once submitted, will allow the Agency to characterize the risk of DDVP to terrestrial 

and aquatic ecosystems. Primary producers (i.e. plants) provide oxygen, food and habitat vital to 

ecological processes. Therefore, a solid understanding of the potential risks to plants is essential 

in order to assess the environmental risks the use of DDVP may pose. If the data indicate that 

DDVP poses significant risks to these plant species, the Agency may explore additional decision 

options to minimize the risks to these species. 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DDVP 5/14/2009 

National Resource Defense Council. 2006. Petition of Dichlorvos (DDVP) Revised Ecological 

Risk Assessment. June 2,2006. Attn: Docket ID Number OPP-2002-0302. 

U.S. Environmental Protection Agency. 1995. ~dtice of Preliminary Determination (Position 

Document 213) in the Federal Register September 28, 1995. Washington, D.C. 

U.S. Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment. 

Risk Assessment Forum, Office of Research and Development, Washington, D.C. 

EPA/630/R-951002F. April 1998. 

U.S. Environmental Protection Agency. 2000. Risk Characterization Handbook. Science Policy, 

Council, U.S. Environmental Protection Agency, Washington, D.C. 20460. EPA 100-B00-002. December 2000. 

U.S. Environmental Protection Agency. 2004. Overview of the Ecological Risk Assessment 

Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency. 

Endangered and Threatened Species Effects Determinations. Office of Prevention, 

Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. 

January 23,2004. 

U.S. Environmental Protection Agency. 2005a. DDVP RED 084001 D312675 January 3 1,2005 

Dichlorvos: Interim Reregistration Eligibility Decision-Environmental Fate and Effects 

Division's Response to Public Comments. Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Washington, D.C. 

U.S. Environmental Protection Agency. 2005b. Revised EFED Risk Assessment for the 

Dichlorvos Reregistration Eligibility Document. June 22,2005. Office of 

Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, 

Washington, D.C. 

U.S. Environmental Protection Agency. 2005c. EFED Response to Registrant's Error Correction 

Comments on Dichlorvos RED. June 22,2005. Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington, D.C. 

U.S. Environmental Protection Agency. 2006a. EFED Response to Public Comments on 

Dichlorvos Ecological Risk Assessment 084001 D290605. March 20,2006. Office of 

Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, 

D.C. 

U.S. ~hvironmental Protection Agency. 2006b. Interim Reregistration Eligibility Decision for 

Dichlorvos (DDVP). Office of Prevention, Pesticides and Toxic Substances, Office of 

Pesticide Programs, Washngton, D.C. June 2006. 
Registration Review 

Ecological Risk Assessment 

Problem Formulation for the Insecticide DD W 5/14/2009 

U.S. Environmental Protection Agency. 2006c. EFED Response to Public Comments on 

Dichlorvos Ecological Risk Assessment. August 3 1,2006. Office of Prevention, 

Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. 

U.S. Environmental Protection Agency. 2007a. Response to petition brought by the National 

Resource Defense Council November 16,2007. Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington, D.C. 

U.S. Environmental Protection Agency. 2007b. Dichlorvos (DDVP) Usage on Dairy Cattle, 

Beef Cattle, Swine, and Poultry (Animals and Facilities) 'D340495 Decision # 379882. 

Product Review Panel June 27,2007 and November 7,2007. Biological and Economic 

Analysis Division (BEAD). Office of Prevention, Pesticides and Toxic Substances, 

Office of Pesticide Programs. Washington, D.C. 

U.S. Environmental Protection Agency. 2007c. DDVP RED 084001 D292980 December 10, 

2007. Revised EFED Risk Assessment for the Dichlorvos Reregistration Eligibility 

Document. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide 

Programs. Washington, D.C.