Implementing Pesticide Use Data and GIS To Improve Treated Area

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Chapter 12

Implementing Pesticide Use Data and GIS To Improve Treated Area Estimates in Agricultural and Residential Exposure Assessments Nathan Snyder*,1 and Michael Winchell2 1Waterborne

Environmental, 897-B Harrion Street S.E., Leesburg, Virginia 20175, United States 2Stone Environmental, 535 Stone Cutters Way, Montpelier, Vermont 05602, United States *E-mail: [email protected]

Pesticide application data is a key component in all risk assessment activities. At early tiers of an assessment, regulators make the conservative assumption of all labeled acres treated at the maximum label rate. As refinements to the risk assessment are made, or added spatial or temporal complexity is desired, the simplifying assumptions need to be refined to capture a more realistic range of exposure, otherwise exposure estimates will always be upper-end conservative values. Currently, no data is available on a large scale that explicitly identifies exact location, time, and rate of applications that would be useful in large scale risk assessments (state or national). Applications are influenced by agronomic practices which vary by (grower practice) which lead to variations compared to the labeled maximums. Market and efficacy forces lead producers to make choices on products, rates, and locations. Historic application data does exist at various scales (state, county, district, or township) that when combined with detailed cropping and land use patterns, allow for refinements to use assumptions for risk assessments that can be used to provide context to the maximum assumptions. For predictive assessments, it is useful and appropriate to give risk managers context around anticipated use ranges, spatial likelihood, watershed distribution, or context in predicted exposures based on recent application data. This

© 2018 American Chemical Society

ang et al.; Managing and Analyzing Pesticide Use Data for Pest Management, Environmental Monitoring, Public Health, and Public Pol ACS Symposium Series; American Chemical Society: Washington, DC, 2018.

paper outlines methods in both residential and agricultural crop protection practices where historical data is used to refine use pattern estimates so that inputs to exposure estimates could be modified to reflect past and anticipated future use pattern variations. With the adoption of these methods, the risk assessor can make informed decisions based on upper end exposure estimates as well as refined more realistic use estimates based on best available data.

Introduction The quantification of pesticide use in both agricultural and residential settings is critical to environmental exposure modeling and accurate estimates of the potential for pesticide exposure. This paper provides a review of methods and results using best available survey data using pyrethroid use data to provide input assumption refinements for standard environmental exposure modeling as a case example.

Materials and Methods Agricultural Pesticide Use Analysis Agricultural Pesticide Use Background Understanding the extent and frequency of agricultural pyrethroid use is a critical component to accurately modeling exposure in aquatic environments. The simplest and most conservative approach is to assume that all the labeled agricultural area receives a treatment. This approach is acceptable for lower tier, screening level assessments, when the use of worst case assumptions can be used to quickly determine whether the risk of exposure exceeds effects metrics. Worst case assumptions are often very different than actual practices, do not account for spatial variations and can result in unrealistic over-estimations of exposure. It is therefore necessary to adopt refined approaches for determining more realistic estimates of the extent of pyrethroid use when this is likely to be important for regulatory risk assessments. In response to USEPA’s ongoing Registration Review of the synthetic pyrethroids, the Pyrethroid Work Group (PWG) examined national use from 2009-2012 on all crops identified in the GfK Kynetec AgroTrak® database, and California specific use from the CA DPR Pesticide Use Report database (1) for 2009-2012. The AgroTrak® data reported reflect the best-available information across the US. They provide important insights into the use of pyrethroids across the US at national, state and more local scales and provide key information regarding pyrethroids as a class as well as for individual AIs. Additionally, California-specific Pesticide Use Reporting program data are provided for CA crops since this is even more specific to CA regional agriculture. The active ingredients (AIs) examined include bifenthrin, cyfluthrin, beta-cyfluthrin, 242


cypermethrin, zeta-cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, lambda-cyhalothrin, gamma-cyhalothrin, permethrin, and tefluthrin. For the 9 PWG pyrethroids, data on AI, crop, application method, pounds applied and acres treated were reported at the Crop Reporting District (CRD) and US state levels (2). These data were examined to understand: • • • •

the relative contribution of each AI to the recent total national use of pyrethroids by individual crop and for all crops, the fraction of crops grown that were treated with pyrethroids, the geographic distribution of individual AI usage, and the geographic distribution of crop-specific usage for all actives and application methods combined.

Variation of insecticide use from one year to the next is to be expected. To attempt to take account of this source of variability, data were aggregated over a four year period (2009-2012 – the most recent set of four year AgroTrak® data available at the start of the evaluation). The AgroTrak® database identifies over 50 crops to which pyrethroids have been reported being applied to between 2009 and 2012. Information for each AgroTrak® crop was aggregated into the PWG key crop classes to facilitate interpretation and implementation into the probabilistic exposure refinement process.

Agricultural Use Surveys The AgroTrak® database reports the method of application for both the Row Crop and Specialty Crop databases. Using this information, estimates of the percentage of crop area treated (PTA) and pounds applied via aerial applications (as opposed to ground) were generated.

Definitions To ensure clarity for the reader, the following definitions are provided: • • • • • •

Active Ingredient (AI): Individual active ingredient(s) contained in the product. Brand: Summation of products with similar chemistries and product names. Product: A specific formulation containing one or more AIs, with unique chemistries and concentrations. Pounds AI: The pounds of active ingredient applied to a crop. Acres grown: Total acres of crop grown in US Base Acres: The area treated at least once with a spray of products. Does not take into account the number of products in the spray. Multiple applications of the same product to the same field are considered the same base acres. 243


•

•

Total Acres/Product Acres: The area treated by each product in the spray of defined composition, multiplied by the number of treatments. OR the number of times the tractor passes over the same area applying the same spray. Application Method: How a product was applied to the crop (e.g., aerial, ground, banded, etc.).

Since some PWG risk assessments focused on California-specific crop scenarios, similar data were also accessed from the California Pesticide Use Reporting program (PUR) for the same four year period (2009-2012). These data were used to verify or supplement the results acquired from the AgroTrak® data in CA. Similar to the national review of pyrethroid usage, the CA PUR data (coupled with NASS 2012 Census of Agriculture) were used to determine PTA and market share metrics. Recent data on pyrethroids applications (2009-2012) were accessed from the GfK Kynetec AgroTrak® database in 2013 for the following pyrethroids: bifenthrin, cyfluthrin, beta-cyfluthrin, cypermethrin, zeta-cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, lambda-cyhalothrin, gammacyhalothrin, permethrin, tefluthrin, and tralomethrin (3). The following table (Table 1) list the crops recorded as having pyrethroid applications between 2009 and 2012 in the Row Crop and Specialty Crop database nationally. Records in these databases can be queried to be reported at the level of both US county and Crop Reporting District (CRD, a collection of counties very similar to the USDA Agricultural Statistics Units). The data extract requested by PWG included the fields listed in Table 2. Base Acres are not available at the county or CRD level in the Specialty Crop database; the smallest spatial reporting unit for base acres was by state. Therefore, to obtain comparable values for specialty crop Base Acres, an query was performed for both row crops and specialty crops at the state level including the fields listed in Table 3.

Processing Environment and Methods The AgroTrak® query data were imported into a Microsoft Access 2010 database for processing and query generation. Data are provided at the county level, but because of the statistical sampling methods employed by GfK Kynetec during the collection and synthesis of survey results, tabular summarizations should be at the CRD level (a collection of counties very similar to the USDA Agricultural Statistics Units) or higher. The row crop and specialty crop data were combined into a single table. Base Acres were not present in the CRD level specialty crop database this field is NULL in the combined table for each record for each specialty crop. In addition, the Who Applied field for specialty crops is set to “not applicable” as this is not recorded in the source data.

244


Table 1. List of row and specialty crops in AgroTrak® databases receiving pyrethroid applications between 2009 and 2012 Row (Field) Crops

Specialty Crops

Alfalfa

Almonds

Lemons

Canola (oilseed rape)

Apples

Lettuce

Corn

Apricots

Lima Beans

Cotton

Artichoke

Onions

Dry Beans/Peas

Asparagus

Oranges

Peanuts

Beans (Snap, Bush, Pole, String)

Peaches

Potatoes

Broccoli

Pears

Rice

Cabbage

Peas (Fresh/Green/Sweet)

Sorghum (Milo)

Caneberries

Pecans

Soybeans

Cantaloupes

Peppers

Sugar Beets

Carrots

Pistachios

Sugarcane

Cauliflower

Plums/Prunes

Sunflowers

Celery

Pumpkins

Tobacco

Cherries

Spinach

Wheat, Spring

Cucumbers

Squash

Wheat, Winter

Garlic

Strawberries

Grapefruit

Sweet Corn

Grapes, Raisin

Tomatoes

Grapes, Table

Walnuts

Grapes, Wine

Watermelons

Hazelnuts

PWG Crop Grouping (“key crops”) The AgroTrak® data contained records for over 50 crops to which pyrethroids had been applied between 2009 and 2012 (Table 1). These crops were grouped into twelve crop groups (“key crops”). These key crops represent both high pyrethroiduse crops, as well as those where modeling with EPA standard Tier II PRZM/ EXAMS scenarios suggests refinement to estimated environmental concentrations (EECs) are desired.

245


Table 2. AgroTrak® data fields extracted at the US county level Row (Field) Crops

Specialty Crops

Year

Year

Active Ingredient

Active Ingredient

Brand

Brand

Product

Product

Company

Company

Application Timing

Crop Stage

Application Method

Application Method

Who Applied

Who Applied

Crop

Crop

State

State

CRD (numeric)

CRD (numeric)

FIPS (county code)

FIPS (county code)

Base Acres

Total Acres

Total Acres

Pounds AI

Pounds AI

Table 3. AgroTrak® data fields extracted at the US state level Row (Field) Crops (state level)

Specialty Crops (state level)

Year

Year

Crop

Crop

State

State

Acres Grown

Acres Grown

Base Acres

Base Acres

Total Acres

Total Acres

Pounds AI

Active Ingredient

Active Ingredient

The PWG key crop groups are: corn, soybeans, cotton, vegetables/ground fruit, tree nuts, citrus, alfalfa, sweet corn, spring wheat, winter wheat, sunflower and peanut. Summaries of the pyrethroid usage data are reported by PWG key crop groupings and individual crops as originally listed in the AgroTrak® database were generated. 246


Estimating Percentage of Crop Treated with Pyrethroids Using information in the AgroTrak® database, it is possible to estimate the percentage of crops being treated with pyrethroids. The base acres treated can be compared to the acres grown (which encompass all acres of that crop, regardless of pesticide applications). Base acres relate to the area treated at least once with a product, so that multiple applications of a single product to the same field do not increase the base acres. Total base acres were extracted at the state level to be used for PTA estimation. The PTA for each crop was calculated nationally or regionally for each of the four years as:

Due to the way data are collected and reported for specialty crops in the AgroTrak® database, the sum of base acres treated is sometimes greater than actually treated, resulting in higher (i.e., more conservative) PTA values for these crops. This can happen if individual applications to the same field had different active ingredients, or a product applied contained more than one pyrethroid active ingredient. Crops with more allowable applications (e.g., sweet corn) are more likely to have ‘over counting’ of base acres when summed. This applies to crops in the specialty crop database only, and not those in the row crop database. The AgroTrak® database provides an estimate of acres grown for each year/crop/state combination. To obtain external validation of these estimates, the AgroTrak® data for 2012 were compared to the 2012 USDA Census of Agriculture for the PWG key crops/crop groupings.

CA Pesticide Use Reporting Usage data for the 12 pyrethroids were summarized for CA, and total acres treated were compared to the NASS 2012 Census of Agriculture harvested acres for CA in 2012 (USDA NASS, 2014) to estimate PTA for each crop in CA for each of the four years. Using only the PUR data, total acres treated for each individual active ingredient were compared to the sum total of all pyrethroid uses to estimate a market share in CA. Isomer variants for cyfluthrin, cyhalothrin and cypermethrin were combined into single ‘combined’ values for each AI.

Estimating Percentage of Pyrethroid Applications Made Aerially The potential exposure of receiving water bodies adjacent to agricultural fields resulting from possible spray drift transport is heavily influenced by the method of application (i.e. ground or aerial spray equipment specifically). Aerial applications are often the default in regulatory modeling because these result 247


in the greatest potential drift fraction (all other variables being equal). The AgroTrak® database provides information on the numbers of aerial applications in the Application Method (specialty crops) and Who Applied (row crops) database fields. For row crops, aerial applications were defined as records having a value of “Custom Aerial” in the Who Applied field. For specialty crops, aerial applications were defined as records having a value of “Aerial” in the Application Method field (Table 4).

Table 4. Listing of possible values for Application Method and Who Applied fields in the two AgroTrak® databases Row (Field) Crops

Specialty Crops

Who Applied

Application Method

(only pyrethroid entries listed)

Aerial

Farmer Applied

Chemigation

Custom Ground

Ground

Custom Aerial

Spot Treatment Strip Spray Trunk to Trunk Spray

To estimate the percent of pyrethroid treated acres that was applied aerially, the total of acres aerially applied was compared to the total acres treated (total acres aerial / total acres). To estimate the percent of pyrethroid pounds that was applied aerially, the total of pounds aerially applied was compared to the total pounds applied (total pounds aerial / total pounds).

Temporal Aspects The use of insecticides is governed by a number of factors, but is largely driven by the impact of weather conditions on pest population dynamics; therefore variation from one year to the next is to be expected. To attempt to take account of this source of uncertainty, data were aggregated over a four year period (2009-2012 – the most recent four year period for which AgroTrak® data were available at the time of this evaluation). Results are reported as this four year period aggregate unless otherwise specified. However, summary information on annual trends of pyrethroid use is also presented for the individual years between 2009 and 2012. 248


Use Survey Analysis To Parameterize Exposure Models Ecological Risk Assessments (ERAs) conducted by USEPA or registrants typically follow a sequential, tiered, exposure assessment process. Initially, a wide range of the crops labelled for a given active ingredient (AI) is examined using the appropriate EPA Tier II exposure modeling scenarios to provide a relative ranking of exposure potential related to the numbers of applications and the application rate. After identifying the relative significance of the labelled crops for a given AI (and pyrethroids as a group) refinement opportunities for crops (or crop groupings) are considered at higher tiers of the assessments. The other applications of the data relate to addressing sources of uncertainty relating to assumptions inherent at various stages of the risk assessment. One key area addresses the assumption typically used in exposure modeling whereby the model assumes that every acre of a given crop is treated with the AI-of-interest. The data collected here allow the Percent Treated Area (PTA) for a given crop to be expressed both in terms of the percent treated with any pyrethroid AI as well as the percent treated with each specific AI (e.g. market share). The second key area addresses the standard exposure model assumption that all applications are made via aerial sprays. Data reported here allow informed assessments of the fraction of applications made via aerial sprays expressed nationally, regionally and by crop or across all crops. Finally, the individual market shares of each pyrethroid AI (nationally and by crop) are another important factor in the uncertainty analyses. The analysis and data allows for refinement to key inputs to exposure tools including application rate, frequency, and method based on best available data.

Residential Pesticide Use Analysis Residential Pesticide Use Background Understanding the extent and frequency of households using outdoor pyrethroids is a critical component to accurately modeling pyrethroid exposure in residential aquatic environments. The simplest and most conservative approach is to assume that all of the households in a given neighborhood apply outdoor pyrethroids. This approach is acceptable for lower tier, screening level assessments, when the use of worst case assumptions can be used to quickly determine whether the risk of exposure exceeds effects metrics. Worst case assumptions are often times very different than reality and can result in vastly unrealistic over-estimations of exposure. It is therefore necessary to adopt refined approaches for determining more realistic estimates of the extent of outdoor residential pyrethroid use when this is likely to be important for regulatory risk assessments. More realistic and accurate quantification of the extent of residential pyrethroid use can be obtained from surveys of homeowner use of outdoor insecticides. Several such surveys have been conducted in recent years, 249


providing a solid foundation for quantifying the extent of pyrethroid use and in characterizing application practices. These surveys, conducted both in California (4, 5); and across diverse regions of the United States (6), can serve as the basis for quantification of several key inputs required for higher tier residential exposure modeling. The Pyrethroid Working Group (PWG) has developed a residential exposure modeling scenario capable of representing pyrethroid applications to a heterogeneous landscape (7). The approach uses a version of EPA’s watershed scale urban pollutant transport model, SWMM (Stormwater Management Model) (8). In SWMM, a residential watershed can be divided into many different sub-catchments and land uses. Using SWMM’s sub-catchment and land use structure, different pyrethroid use sites within the residential environment can be represented. In a residential neighborhood, there are several potential pyrethroid use sites that are open to the impact of rainfall/irrigation and potential off-site pyrethroid transport, and can be quantified spatially using geographic information systems. These use sites include:

1.

2.

3.

4.

Building foundation perimeters: This use site consists of the ground surface extending several feet out from a structure’s foundation and several feet up the foundation wall, and is intended to protect the home’s perimeter from invading insects. During a foundation perimeter application, both pervious and impervious surfaces near the home are treated, including the driveway and patios/walkway areas within a several foot perimeter around the main house and garage. The treatment of these areas was specifically targeted for application reductions by more recent pyrethroid label changes. Patios and walkways (away from the building): Applications made to patios and walkways away from the building are not explicitly associated with a foundation perimeter application, and tend to be targeted to portions of the surface showing evidence of insect activity. Driveways (away from the garage door and wall): Similar to patios and walkways, applications made to driveways away from the building are not explicitly associated with a foundation perimeter application, and tend to be targeted to portions of the surface showing evidence of insect activity. Lawns/landscape areas: Lawn applications include both localized applications (such as ant mounds) as well as broadcast applications intended to treat the entire lawn. The landscape component of this use site includes pervious landscaped areas that are not part of the turf portion of the lawn, with typically more localized applications than the lawn component.

A planimetric map delineating these surfaces is provided in Figure 1 to aid in the description of these use sites. This analysis of residential pesticide use is focused on the characteristics of applications to these four types of use sites. 250


Figure 1. Spatial Delineation of Outdoor Household Pyrethroid Use Sites (see color insert) There are several important characteristics of pyrethroid applications, both neighborhood level information and use site specific information, which require quantification for the residential exposure model scenario developed. The general neighborhood level characteristics include the following: 1.

The fraction of neighborhood households receiving outdoor insecticide treatments: This characteristic is represented schematically in Figure 2. In this example, six out of the eight households in the neighborhood receive outdoor insecticide treatments, equal to fraction treated of 0.75. An insecticide “treatment” is equivalent to a visit by a Pest Control Operator (PCO), a Lawn Care Operator (LCO), or an application made by a homeowner, where at least one use site receives an application. In the residential exposure model parameterization, this value will be a factor in calculating the fraction of all possible use sites in a neighborhood that could receive a pyrethroid application (but will also require an understanding of the prevalence of pyrethroids compared to other insecticides). 251


Figure 2. Schematic of a Neighborhood Showing Fraction of Households and Types of Use Sites Treated (see color insert) The characteristics that are use site specific include the following: 1.

The fraction of use sites treated with each active ingredient: This application characteristic describes, for those households that receive an outdoor insecticide treatment, which use sites receive applications and with which active ingredients. In the example shown schematically in Figure 2, building foundation perimeters, driveways, patios/walkways, and lawn/landscape areas are marked as either included or not included in an insecticide treatment (with a “T”). In the example shown, bifenthrin is applied to building foundation perimeters for two of the six households that receive insecticide treatments, resulting in a fraction of building foundation perimeters treated with bifenthrin of 0.33. The other actives applied to building foundation perimeters were fipronil and cyfluthrin (with fractions treated of 0.33 and 0.17 respectively). Similar calculations can be made for the other use sites. It is important to note that when used to parameterize the residential exposure model, the “fraction of use site treated with each active ingredient” value must be adjusted by the “fraction of neighborhood households receiving outdoor insecticide treatments” described earlier. This adjustment process is demonstrated in the Results and Discussion section. Throughout this residential use chapter section, the phrase “fraction of use sites treated” 252


2.

3.

will always be used to describe whether or not a use site (e.g., driveway) on a given house lot is or is not treated. The seasonal frequency of applications made to each use site: This characteristic describes how often and when applications to use sites are made. For example, a lawn may receive one application in the spring, two applications in the summer, and one application in the fall. In a residential exposure model parameterization, this data will determine when in a calendar year that applications will be made to each use site. The percentage of a use site’s surface area that is treated: This important application characteristic is shown schematically in Figure 3. This figure shows a driveway (away from the garage door) that has been split into treated and untreated sections. In this example, 20% of the driveway surface area (away from the garage door) is treated and 80% of the driveway surface area is untreated. In an residential exposure model parameterization, this value will be a factor in determining the total surface area of a particular use site within a neighborhood that will receive a pyrethroid application. Throughout this report, the phrase “percentage of a use site’s surface area” will always be used to describe how much surface area of a typical use site (e.g., driveway) receives coverage during an application.

Figure 3. Schematic of the Percentage of a Use Site Surface Area Treated (see color insert) 253


This chapter section details the approaches followed to estimate the extent and frequency of pyrethroid applications to support regionally specific residential exposure modeling. The analysis quantifies these application characteristics for the highest use pyrethroid active ingredients independently. The resulting pyrethroid use characteristics describing the extent and frequency of applications provided in this analysis were designed to parameterize regionally distinct residential pyrethroid aquatic exposure models.

Residential Use Surveys The primary survey evaluated in this analysis was commissioned by the PWG to collect information on the extent of pyrethroid use by homeowners and professional applicators, as well as the application practices followed by professional Pest Control Operators (PCOs) and Lawn Care Operators (LCOs) (6). This study, the PWG Regional Residential Use Survey, was designed to quantify the regional variability in use extent and application practices by sampling from six distinct geographic regions. The study compiled data from two different sources. The primary data source that contributed to the PWG Regional Residential Use Survey (6) was a custom survey based on interviews of PCO/LCO organizations spread across metro areas of the Northeast, Mid-Atlantic, Southeast, South Central, North Central, and Northwest United States (Figure 4). The objective in selecting thee regions was to acquire information on professional application practices beyond the state of California, where previous detailed pyrethroid and pesticide use surveys have already provided valuable data (4, 5). The survey questionnaire was developed with the intention of gathering information on application practices representative of the year 2012 (one prior to the survey year), and thus did not reflect adoption of recently revised or amended pyrethroid labels. It should be noted that while the survey was conducted among PCO’s and LCO’s within a limited number of metro areas as shown, it is referred to as regional. This reflects the fact that PCO’s and LCO’s tend to be concentrated in metro areas. The survey of 502 individual companies collected information from both PCOs and LCOs on the types of outdoor insecticides they use, where they apply them, and how they apply them. Of the 502 organizations interviewed, 67% performed PCO services only, 16% performed LCO services only, and 17% of the sample group worked in both pest control and lawn care segments. This survey was designed specifically to provide following the data required to parameterize pyrethroid applications in residential exposure models: 1. 2. 3. 4. 5.

The fraction of households receiving outdoor pyrethroid applications The prevalence of pyrethroid use on different outdoor use sites The relative use of different pyrethroid active ingredients on each use site The seasonal frequency of applications on each use site The application methods and surface coverage fraction for each use site 254


The pyrethroid active ingredients that were focused on this survey were: 1. 2. 3. 4. 5. 6.

Bifenthrin Cyfluthrin/beta-cyfluthrin Deltamethrin Lambda-cyhalothrin Permethrin Cypermethrin.

Additional active ingredients reported in the survey were very few, and were lumped into an “other active” category.

Figure 4. Association between Metropolitan Areas Surveyed and Six National Geographic Regions (see color insert)

A second report concerning homeowner use of outdoor insecticides (9) provided additional information to characterize residential pesticide use. The report is a bi-annual survey of 1,500 homeowners to determine pesticide and fertilizer use in and around homes, including: 1) outdoor non-plant insecticides, and 2) lawn and garden insecticides. The survey includes brand information and interpreted active ingredient use. In addition to consumer purchased product use, the report includes data on homeowner use of pest control services and lawn care service. This survey divided the US into four geographic regions: the Northeast, Midwest, South, and West. A map of these regions is shown in Figure 5. Information contained in this survey was used primarily to estimate regional differences in the fractions of households applying outdoor insecticides. 255


Figure 5. Geographic Boundaries for Consumer Regions (Corresponding to U.S. Census Regions) (see color insert)

Use Survey Analysis To Parameterize Exposure Models The PWG Regional Residential Use Survey (6) described previously was the primary source used to characterize residential pyrethroid applications for parameterizing residential exposure model scenarios. The analysis included all six geographic regions reported in the survey, and focused on the four dominant use sites previously described: foundation perimeters, patios/walkways, driveways, and lawns. The derivation of these regional application characteristics are described in the sections that follow.

Quantification of Households Using Outdoor Insecticides The consumer markets report, summarized in the PWG Regional Residential Use Survey (6) divided the US into four regions (Figure 5). This summary of the market survey showed that the purchase of PCO service ranges from 18% of respondents in the Midwest to 32% of respondents in the South, with a nationwide average of 26%. The purchase of services from LCOs is less common, ranging from 11% in the South to 17% in the Midwest, with a nationwide average of 14%. The summary of outdoor insecticide use by homeowners themselves (i.e., non-professional) indicated that non-professional application of lawn or garden insecticides is more common than for outdoor non-plant insecticides (i.e. compounds applied to structures and hard surfaces), with regional ranges from 256


41% to 57% for lawn/garden insecticides (47.3% nationwide) and 26% - 30% for non-plant insecticides (28.3% nationwide). A separate survey focused on Orange County, California (4) was commissioned by the California Department of Pesticide Regulation (CDPR) to better understand residential behavior regarding the use of outdoor insecticides. The information from this survey that is of greatest value for parameterizing residential exposure models is the fraction of the population that applied outdoor pest control products by residence type and ownership, and was used to help refine the estimates of use across geographic regions outside of California. The data reported in this survey distinguished between home owners that applied themselves, had professional applications, and both applied themselves and had professional applications. A summary of this data from is provided in Table 5 (4). Based on this survey, the fraction of households applying outdoor insecticides in a California neighborhood would be set at 75.9%. This value is representative of ALL outdoor insecticides, not individual products or active ingredients, and not yet representative of the use on specific outdoor use sites.

Table 5. Residential Use of Outdoor Pest Control Products in Orange County, California (4)

Rent an Attached Home

All Single Family and Detached Homes

All Single Family and Detached Homes (%)

Own a Single Family Detached Home

Own an Attached Home

Rent a Single Family Detached Home

Home Applied

229

38

37

16

320

32.7

Professional Applied

143

122

29

78

372

38.0

Home & Professional Applied

40

7

3

0

50

5.1

No outdoor pest controlproducts are applied

127

31

56

22

236

24.1

Total

539

198

125

116

978

100

The total percentage of households receiving outdoor lawn/garden and non-plant insecticide treatments is shown in Table 6. Here, the percentages of those receiving professional services (PCOs and LCOs) is added to the percentage of residents applying themselves, with several adjustments made to account for a fraction of respondents applying products themselves and also hiring professionals. The adjustments assume that the trends found in California (4) regarding the fraction of households where outdoor insecticides area applied both 257


by the homeowner and also by professionals is similar in the other regions of the United States. The PWG residential use survey report (6) provides additional details on the derivation of these homeowner applied and professional applied pesticide use statistics.

Table 6. Total Professionals and Non-Professional Outdoor Insecticide Use by Region % Receiving Each Product/Service By Region Type of Outdoor Insecticide Treatment Received

Total US

Northeast

Midwest

Estimated Lawn or garden insecticides (non-professional) ONLY

41.1

37.4

36.6

49.3

35.6

Estimated Outdoor non-plant insecticides (non-professional) ONLY

24.6

22.8

25.5

26.2

22.2

Estimated Receiving LCO Services ONLY

12.3

13.2

15.0

9.7

10.6

Estimated Receiving PCO Services ONLY

22.9

21.2

15.9

28.2

22.9

Estimated Total Percentage Receiving Lawn/Garden Treatments

57.3

54.3

55.4

63.3

49.5

Estimated Total Percentage Receiving non-Plant Treatments

50.9

47.2

44.4

58.4

48.4

South

West

The data in Table 6 (“Estimated Total Percentage Receiving Lawn/Garden Treatments” and “Estimated Total Percentage Receiving non-Plant Treatments” rows) shows that both lawn/garden and non-plant treatments are more prevalent in the South region than in the other three. The non-plant treatment percentages are similar for the Northeast, Midwest, and West, while lawn treatments in the Northeast and Midwest are slightly more common than the West. From these baseline fractions of treated households, more specific data on the prevalence of individual active ingredients and the treatment patterns for different outdoor use sites can be incorporated to better define pyrethroid application characteristics. Based upon the review of additional public and proprietary datasets, the extent of outdoor insecticide use summarized in Table 5 (for California) and in Table 6 (for the remainder of the USA) represent conservative estimations (i.e., the values are on the high side of potential use extent). One source specific to California that was reviewed was a survey conducted in the Sacramento and San Francisco Bay areas of Northern California between 2006 and 2010 (10). Based on Figure 1 in Wu et al. (2013), the total number of households applying pesticides outdoors (the sum of “Outdoor Spray” (~44%) and “Professional Application” (~26%)) is equal to 70%. This value of 70% makes the conservative 258


assumption that all of the “Professional Applications” are outdoors, yet it is still less than the 75.9% derived for California based on the Wilen report (4). In addition, pyrethroid registrants regularly commission proprietary studies to estimate the market extent for professional and home-applied outdoor insecticides. Recent survey data from 2012 suggests that at the national level, only about 15% of households hire PCO services. This is substantially less than the 38% estimated for California (Table 5) and the national average estimate of 26% (6). Based on these additional sources, the estimates of households applying outdoor insecticides presented here are conservative (over) estimates suitable for “worst case scenario” modeling of potential exposure.

Quantification of Pyrethroid Fraction of Use Site Treated by Region One of the questions asked of PCOs and LCOs was the percentage of outdoor insecticide applications that included a pyrethroid. The responses to this question showed that between 50% and 63% of applications (depending upon region) included a pyrethroid. In addition, PCOs and LCOs were asked which use sites they treated with outdoor insecticides. Furthermore, for each use site, PCOs and LCOs indicated which active ingredients they used in applications. From these three sets of data, the fraction of each use site treated with a given active ingredient was calculated. The calculations of the fraction of use sites treated for foundation perimeters, patios/walkways (away from building), driveways (away from garage door/wall), and lawns were made for the North Central, Mid-Atlantic, Southeast, South Central, Northwest, and Northeast regions. In these calculations, the “Percent of Treatments Using Pyrethroids” represents the percent of all outdoor insecticide applications that include pyrethroids and is the constant for all active ingredients. The “Percent Treating Use Site” represents the percent of PCOs/LCOs in that region that reported treating the specific use site, and is also constant for all active ingredients. The values for “Percent Treating Use Site” extracted from the PWG Regional Use Survey (6) are from the “PCO Only” responses for non-plant use sites (building foundation perimeters, patios/walkways, and driveways) and from the “LCO Only” responses for the lawns and landscape area use sites. The “Percent of Pyrethroid Active Ingredients” values represent the fraction of pyrethroid applications on that use site that each active ingredient accounts for (these percent values will sum to 100%). The final result of this calculation is the “Estimated Percent of Use Sites Treated by Each AI”, which is calculated according to Equation 1 below:

where, PT_AI = Estimated percent of use sites treated by (each) AI PT_UP = Percent of (outdoor insecticide) treatments using pyrethroids PT_US = Percent (of PCOs/LCOs) Treating Use Site 259


P_PAI = Percent of pyrethroid active ingredients (that this AI represents on this use site) An example of the detailed data that went into these calculations is shown for foundation perimeter treatments in the Southeast region in Table 7. The percent of treatments using pyrethroids of 57% in the Southeast indicates that 43% of PCOs us non-pyrethroids in their treatments. Of the PCOs that use pyrethroids, 94% of them treat the foundation perimeter. Bifenthrin was by far the most commonly used pyrethroid, at 48.4% of pyrethroid use, which is more than four times greater than the second most commonly applied pyrethroid. Looking at all pyrethroids combined, it was estimated that for households that use outdoor insecticides, 53.6% of foundation perimeters are treated with a pyrethroid.

Table 7. Calculation of Estimated Fraction of Use Sites Treated with Each Active Ingredient, Southeast Region, Foundation Perimeter Percent of Treatments Using Pyrethroids (%)

Percent Treating Use Site (%)

Percent of Pyrethroid Active Ingredients (%)

Estimated Percent of Use Sites Treated by AI (%)

Bifenthrin

57.0

94.0

48.4

25.9

Cyfluthrin/ beta cyfluthrin

57.0

94.0

10.3

5.5

Cypermethrin

57.0

94.0

11.3

6.1

Deltamethrin

57.0

94.0

10.3

5.5

Lambda cyhalothrin

57.0

94.0

7.2

3.9

Permethrin

57.0

94.0

7.4

4.0

Other

57.0

94.0

5.1

2.7

100.0

53.6

Active Ingredient

Total

A summary of the fractions of foundation perimeters treated with each pyrethroid by region (for households using outdoor insecticides) is summarized in Table 8. With exception of the Mid-Atlantic region, the fractions foundation perimeters treated with pyrethroids is consistent across regions, ranging from 53% to 56%. Among the different active ingredients, bifenthrin and cyfluthrin/beta cyfluthrin are the most commonly used.

260


Table 8. Estimated Fraction of Use Sites Treated with Each Active Ingredient, Foundation Perimeter (NC = North Central; MA = Mid-Atlantic; SE = Southeast; SC = South Central; NW = Northwest; NE = Northeast) NC

MA

SE

SC

NW

NE

Bifenthrin

21.5

21.6

25.9

19.5

21.4

20.9


10.8

7.5

5.5

9.7

13.2

10.7

Cypermethrin

2.3

3.8

6.1

6.3

2.8

3.4

Deltamethrin

5.7

3.8

5.5

5.2

4.4

11.2

Lambda cyhalothrin

10.1

4.7

3.9

7.4

2.8

6.7

4

3.7

4

6.8

6.6

2.7

Other

1.1

0.9

2.7

0

2.2

0.6

Total

55.5

46

53.6

54.8

53.4

56.1

Active Ingredient

Permethrin

A summary of the fractions of patios/walkways treated with each pyrethroid by region (for households using outdoor insecticides) is summarized in Table 9. The fractions foundation patios/walkways treated with pyrethroids is consistent across regions, ranging from 15% to 26%, with the South Central region PCOs most commonly treating patios/walkways and the Mid-Atlantic least commonly treating patios/walkways. Among the different active ingredients, bifenthrin and cyfluthrin/beta cyfluthrin are generally the most commonly used, but in the South Central region, deltamethrin was more common than all other active ingredients used. A summary of the fractions of driveways (away from the garage door) treated with each pyrethroid by region (for households using outdoor insecticides) is summarized in Table 10. The fraction of driveways treated with pyrethroids is generally from 8% to 15%, with the South Central region somewhat of an outlier at 20.8%. Among the different active ingredients, bifenthrin and cyfluthrin/beta cyfluthrin are generally the most commonly used, but in the South Central region, cypermethrin was nearly as common as bifenthrin. A summary of the fractions of lawns treated with each pyrethroid by region (for households using outdoor insecticides) is summarized in Table 11. The fraction of lawns treated with pyrethroids is generally from 41% to 2%, with the Northwest region an outlier at 25.3%. Among the different active ingredients, bifenthrin is dominant. Permethrin is the second most common active ingredient in four out of the six regions, with cyfluthrin/beta cyfluthrin the second most common in the other two regions.

261


Table 9. Estimated Fraction of Use Sites Treated with Each Active Ingredient, Patios/Walkways (NC = North Central; MA = Mid-Atlantic; SE = Southeast; SC = South Central; NW = Northwest; NE = Northeast) NC

MA

SE

SC

NW

NE

Bifenthrin

8.2

6.2

6.9

6.2

5.6

4.8


3.2

3.3

2.5

6

5.9

5

Cypermethrin

1.5

3.3

2.5

1.2

3.4

2.9

Deltamethrin

1.5

0.7

3.5

7.1

1.7

1.5

0

0.7

2.1

2.7

4.2

3.6

Permethrin

2.4

0.9

0.8

3.3

1.3

1.1

Other

0.8

0

0

0

0

0

Total

17.7

15

18.2

26.5

22

18.9

Active Ingredient

Lambda cyhalothrin

Table 10. Estimated Fraction of Use Sites Treated with Each Active Ingredient, Driveways (away from garage door) (NC = North Central; MA = Mid-Atlantic; SE = Southeast; SC = South Central; NW = Northwest; NE = Northeast) NC

MA

SE

SC

NW

NE

Bifenthrin

5.3

3.9

4

5.5

4.7

7


2.4

3.9

1.2

3.3

2.4

1.5

Cypermethrin

0

0

1.6

4.4

0.8

0

Deltamethrin

0.6

0.6

0.4

2.7

1.6

3

Lambda cyhalothrin

2.4

1.1

0.4

2.7

0.8

2.5

Permethrin

0.6

0.6

0.4

2.2

0.8

0

Other

0.6

0.6

0

0

0

0.5

Total

11.8

10.5

8

20.8

11

14.5

Active Ingredient

Overall, foundation perimeters were the most commonly treated use site among the households making outdoor insecticide applications. After foundation perimeters, lawns were the second most commonly treated use site. The patios/walkways were the third most commonly treated use site, with driveways (away from the garage door) seeing the lowest likelihood of treatments. 262


Table 11. Estimated Fraction of Use Sites Treated with Each Active Ingredient, Lawns (NC = North Central; MA = Mid-Atlantic; SE = Southeast; SC = South Central; NW = Northwest; NE = Northeast) NC

MA

SE

SC

NW

NE

Bifenthrin

27.6

25.6

35.9

19.2

12

33.5


1.3

2.5

0.9

3.3

6.7

5.2

Cypermethrin

1.3

0

3.5

6

1.3

2.1

Deltamethrin

0

3.9

3.5

2.2

1.3

5.2

Lambda cyhalothrin

5.3

3.9

0

2.7

1.3

0

Permethrin

5.3

3.9

3.5

8.2

2.7

4.2

Other

0

1.3

0

0.5

0

2.1

Total

40.7

41

47.3

42.2

25.3

52.3

Active Ingredient

Quantification of Pyrethroid Fraction of Use Site Treated by Region In the PWG Regional Residential Use Survey (6) data on the frequency of applications for each of the four seasons was collected independently for each type of use site. An example of these data for foundation perimeter applications is shown in Table 12. Also included in the table are the adjusted number of applications per season and year represented as whole numbers (this is necessary because fractions of applications are not a valid model input). The rules of thumb used in adjusting the raw application frequency data into numbers of whole applications were as follows: 1.) If the annual application total was greater than 0.33 above a whole number (e.g., 4.33), the total number of annual applications was rounded up to the nearest whole number (e.g., 5), otherwise, it was rounded down. This results in a slightly more conservative calculation of applications per year than standard rounding. 2.) Applications per season were adjusted to match the total annual applications. If rounding seasonal applications to the nearest whole number did not result in a high enough total number of applications per year, then the season with the average applications closest to the next higher whole number was selected to be increased. In the example in Table 12, this was the case for the summer season in the Southeast and South Central regions. These calculations of application frequency to adjust to whole numbers of applications were performed for each of the types of use sites required for residential exposure modeling. The results of these calculations for the other types of use sites considered are reported in Table 13, Table 14, and Table 15. 263


The foundation perimeter use site had four to five applications annually, whereas both patio/walkways and driveways had three to four applications annually. Lawns had the widest range in the number of applications per year, with three to five, depending upon region. The Northwest and Northeast had fewer total applications across all the use sites, with the Southeast and South Central regions having the highest number of total applications.

Table 12. Foundation Perimeters, Mean Number of Applications Per Season by USA Region Mean Number of Applications per Season North Central

Mid Atlantic

Southeast

South Central

Northwest

Northeast

Winter (Dec-Feb)

0.21

0.59

1.14

0.96

0.58

0.29

Spring (Mar-May)

1.18

1.27

1.21

1.24

1.15

1.38

Summer (June-Aug)

1.32

1.2

1.32

1.39

1.12

1.26

Fall (Sept-Nov)

0.98

1.08

1.19

1.08

1.06

1.08

Total of Means

3.69

4.14

4.86

4.67

3.91

4.01

60

58

71

68

53

77

Season

Number of Responses

Adjusted Number of Applications Per Season and Per Year Winter (Dec-Feb)

0

1

1

1

1

0

Spring (Mar-May)

1

1

1

1

1

2

Summer (June-Aug)

2

1

2

2

1

1

Fall (Sept-Nov)

1

1

1

1

1

1

Total Applications/ Year

4

4

5

5

4

4

264


Table 13. Patios/Walkways, Mean Number of Applications Per Season by USA Region Adjusted Number of Applications Per Season and Per Year North Central

Mid Atlantic

Southeast

South Central

Northwest

Northeast

Winter (Dec-Feb)

0

1

1

1

1

0

Spring (Mar-May)

2

1

1

1

1

1

Summer (June-Aug)

1

1

1

1

1

1

Fall (Sept-Nov)

1

1

1

1

1

1


4

4

4

4

4

3

Season

Table 14. Driveways (away from garage), Mean Number of Applications Per Season by USA Region Adjusted Number of Applications Per Season and Per Year North Central

Mid Atlantic

Southeast

South Central

Northwest

Northeast

Winter (Dec-Feb)

0

1

1

1

0

0

Spring (Mar-May)

2

1

1

1

1

1

Summer (June-Aug)

1

1

1

1

1

1

Fall (Sept-Nov)

1

1

1

1

1

1


4

4

4

4

3

3

Season

265


Table 15. Lawns, Mean Number of Applications Per Season by USA Region Adjusted Number of Applications Per Season and Per Year North Central

Mid Atlantic

Southeast

South Central

Northwest

Northeast

Winter (Dec-Feb)

0

0

1

1

0

0

Spring (Mar-May)

1

1

2

1

1

1

Summer (June-Aug)

1

1

1

1

1

1

Fall (Sept-Nov)

1

1

1

1

1

1


3

3

5

4

3

3

Season

Quantification of Pyrethroid Percentage of a Use Site’s Surface Area that Is Treated by Region For applications to some types of use sites, the surface area is not always 100% treated in an application event. The PWG Regional Residential Use Survey asked PCOs and LCOs explicitly, what fraction of the surface area for a particular use site is typically treated. The responses allowed were, “The entire area (100%)”, “Most of the area (about 75%)”, “About half the area (50%)”, “Less than half of the area (about 25%)”, or “Only parts of the area (10% or less)”. To estimate an average fraction of area covered, these qualitative classifications were equated to 100%, 75%, 50%, 25%, and 5% respectively. In 2010, the US EPA began approving revised pyrethroid labels that restrict treatments of hard surfaces to crack and crevice/spot treatment applications. Product packages bearing these revised labels took several years to make their way into the marketplace. The responses to the questions on the fraction of surface area covered appear to be more representative of historical label practices, where larger portions of concrete surface such as patios, walkways, and driveways would receive treatment. Explicitly modeling the current pyrethroid label language would require that a substantial reduction in the fraction of surface area coverage be accounted for in the model parameterization, including a reduction of the driveway treated in front of the garage door from a 5-ft band down to a 2-in band, and a restriction of applications directly to the garage door. The results from the question of surface area treated for patios and walkways (away from building), is provided in Table 16. This table reports information on the probability of pyrethroid application surface area coverage in terms of ranges (e.g., over 50% of the patio/walkway treatments will treat less than 50% of the patio walkway area surface area). There is moderate variation reported between regions. For example, 25% of respondents in the North Central region treat < 10% of the surface area, while 43.3% in the Northeast report treating 266


Implementing Pesticide Use Data and GIS To Improve Treated Area

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