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ENVIRONMENTAL
HEALTH
PERSPECTIVES

Acute Pesticide Illnesses Associated with
Off-Target Pesticide Drift from Agricultural
Applications — 11 States, 1998–2006
Soo-Jeong Lee, Louise Mehler, John Beckman,
Brienne Diebolt-Brown, Joanne Prado,
Michelle Lackovic, Justin Waltz, Prakash Mulay, Abby Schwartz,
Yvette Mitchell, Stephanie Moraga-McHaley, Rita Gergely,
Geoffrey M Calvert
doi: 10.1289/ehp.1002843 (available at http://dx.doi.org/)
Online 6 June 2011

National Institutes of Health
U.S. Department of Health and Human Services

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Acute Pesticide Illnesses Associated with Off-Target Pesticide Drift from Agricultural
Applications — 11 States, 1998–2006
Soo-Jeong Lee1, Louise Mehler2, John Beckman3, Brienne Diebolt-Brown4, Joanne Prado5,
Michelle Lackovic6, Justin Waltz7, Prakash Mulay8, Abby Schwartz9, Yvette Mitchell10,
Stephanie Moraga-McHaley11, Rita Gergely12, Geoffrey M Calvert1
1

Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for
Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio
2

California Environmental Protection Agency, Sacramento, California

3

Public Health Institute, Oakland, California

4

Texas Department of State Health Services, Austin, Texas

5

Washington State Department of Health, Olympia, Washington

6

Louisiana Department of Health and Hospitals, New Orleans, Louisiana

7

Oregon Health Authority, Portland, Oregon

8

Florida Department of Health, Tallahassee, Florida

9

Michigan Department of Community Health, Lansing, Michigan

10

New York State Department of Health, Troy, New York

11

New Mexico Department of Health, Albuquerque, New Mexico

12

Iowa Department of Public Health, Des Moines, Iowa

Corresponding author: Geoffrey Calvert, MD, MPH
NIOSH
4676 Columbia Parkway, R-17
Cincinnati, OH 45226
Phone: 513-841-4448
E-mail: jac6@cdc.gov

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Running Title: Illnesses Associated with Agricultural Pesticide Drift
Key Words: Agriculture, drift, pesticides, poisoning, surveillance
Acknowledgements: Funding support was provided by NIOSH, EPA, and the state agencies that
contributed data. The authors thank Walter Alarcon, Sangwoo Tak and Jia Li for assistance in
conducting this study and Marie Sweeney, Michael O’Malley, Jennifer Sass, Misty Hein, and
EPA for providing comments to improve this manuscript.
Conflict of interest: The authors have no conflicts of interest to declare. Mr. Beckman is
assigned to the California Department of Public Health by his employer (Public Health Institute
[PHI]), and has never been involved in any advocacy activities of PHI.
Disclaimer: The findings and conclusions in this report are those of the authors and do not
necessarily represent the views of NIOSH or each author’s state agency.

Abbreviations:
CDC
CDPR
CI
CIC
EPA
FIFRA
NIOSH
OR
PISP
SENSOR

Centers for Disease Control and Prevention
California Department of Pesticide Regulation
Confidence Interval
Census Industry Codes
U.S. Environmental Protection Agency
Federal Insecticide, Fungicide, and Rodenticide Act
National Institute for Occupational Safety and Health
Odds Ratio
Pesticide Illness Surveillance Program
Sentinel Event Notification System for Occupational Risks

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Abstract
Background: Pesticides are widely used in agriculture and off-target pesticide drift results in
exposures to workers and the public. Objective: Estimate the incidence of acute illnesses from
pesticide drift from outdoor agricultural applications, and describe drift exposure and illness
characteristics. Methods: Data were obtained from the National Institute for Occupational Safety
and Health’s Sentinel Event Notification System for Occupational Risks-Pesticides Program and
the California Department of Pesticide Regulation. Drift included off-target movement of
pesticide spray, volatiles, and contaminated dust. Acute illness cases were characterized by
demographics, pesticide and application variables, health effects, and contributing factors.
Results: During 1998–2006, 2,945 cases associated with agricultural pesticide drift were
identified from 11 states. Forty-seven percent had exposures at work, 92% experienced low
severity illness, and 14% were children (<15 years). The annual incidence ranged from 1.39 to
5.32 per million persons over the 9-year period. The overall incidence (in million person-years)
was 114.3 for agricultural workers, 0.79 for other workers, 1.56 for nonoccupational cases, and
42.2 for residents in 5 agriculture-intensive counties in California. Soil applications with
fumigants were responsible for the largest proportion (45%) of cases. Aerial applications
accounted for 24% of cases. Common factors contributing to drift cases included weather
conditions, improper seal of the fumigation site, and applicator carelessness near non-target
areas. Conclusions: Agricultural workers and residents in agricultural regions were found to
have the highest rate of pesticide poisoning from drift exposure, and soil fumigations were a
major hazard causing large drift incidents. These findings highlight areas where interventions to
reduce off-target drift could be focused.

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Introduction
Pesticide drift, which is the off-target movement of pesticides, is recognized as a major
cause of pesticide exposure affecting people as well as wildlife and the environment. In the
United States in 2004, more than 1,700 investigations were conducted in 40 states due to drift
complaints and 71% of the incidents confirmed that drift arose from pesticide applications to
agricultural crops (Association of American Pesticide Control Officials, 2005). Pesticide drift
has been reported to account for 37-68% of pesticide illnesses among U.S. agricultural workers
(California Department of Pesticide Regulation [CDPR] 2008; Calvert et al. 2008). Community
residents, particularly in agricultural areas, are also at risk of exposure to pesticide drift from
nearby fields. Agricultural pesticides are often detected in rural homes (Harnly et al. 2009;
Quandt et al. 2004). Alarcon et al. (2005) reported that 31% of acute pesticide illnesses that
occurred at U.S. schools were attributed to drift exposure.
The occurrence and extent of pesticide drift is affected by many factors such as the nature
of the pesticide (e.g., fumigants are highly volatile, increasing their propensity for off-site
movement [U.S. Environmental Protection Agency (EPA), 2010]), equipment and application
techniques (e.g., size and height of the spray nozzles), the amount of pesticides applied, weather
(e.g., wind speed, temperature inversion), and operator care (Hofman and Solseng 2001).
Pesticide applicators are required to use necessary preventive measures and comply with label
requirements to minimize pesticide drift. Pesticide regulations such as the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA) and the Worker Protection Standard, an amendment to
FIFRA, require safety measures for minimizing the risk of pesticide exposure, and many states
have additional regulations for drift mitigation (Feitshans 1999).
Better understanding about the magnitude, trend, and characteristics of pesticide

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poisoning from drift exposure of agricultural pesticides would assist regulatory authorities with
regulatory, enforcement, and education efforts. The purpose of this study was to estimate the
magnitude and incidence of acute pesticide poisoning associated with pesticide drift from
outdoor agricultural applications in the U.S. during 1998–2006 and describe the exposure and
illness characteristics of pesticide poisoning cases arising from off-target drift. Factors associated
with illness severity and large events were also examined.
Materials and Methods
Data on acute pesticide poisoning cases were obtained from the National Institute for
Occupational Safety and Health (NIOSH)’s Sentinel Event Notification System for Occupational
Risks (SENSOR)-Pesticides program and CDPR’s Pesticide Illness Surveillance Program
(PISP). The SENSOR-Pesticides program has collected pesticide poisoning surveillance data
from 12 states, using standardized definitions and variables available since 1998 (Calvert et al.
2010). This study included data from 11 states for the following years: Arizona (1998–2000),
California (1998–2006), Florida (1998–2006), Iowa (2006), Louisiana (2000–2006), Michigan
(2000–2006), New Mexico (2005–2006), New York (1998–2006), Oregon (1998–2006), Texas
(1998–2006), and Washington (2001–2006). North Carolina, which joined SENSOR-Pesticides
in 2007, was not included. Because each state removes personal identifiers from the data prior to
submission to the Centers for Disease Control and Prevention (CDC), this study was exempt
from consideration by the federal Human Subjects Review Board.
Participating surveillance programs identify cases from multiple sources including health
care providers, poison control centers, workers’ compensation claims, and state or local
government agencies. They collect information on the pesticide exposure incident through
investigation, interview, and/or medical record review. On some occasions such as large drift

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events, active surveillance is undertaken for further case finding by interviewing individuals
living or working within the vicinity affected by the off-target drift (Barry et al. 2010). Although
SENSOR-Pesticides focuses primarily on occupational pesticide poisoning surveillance, all of
the SENSOR-Pesticides state programs except California collect data on both occupational and
nonoccupational cases. In California, PISP captures both occupational and nonoccupational
cases. SENSOR-Pesticides and PISP classify cases based on the strength of evidence for
pesticide exposure, health effects, and the known toxicology of the pesticide, and use slightly
different criteria for case classification categories (Calvert et al. 2010). This study restricted the
analyses to cases classified as definite, probable, possible, or suspicious by SENSOR-Pesticides
and definite, probable, or possible by PISP. Analyses restricted to definite and probable cases
only were also performed. Because these findings were similar to those that included all four
classification categories (i.e., definite, probable, possible, or suspicious), only the findings that
used the four classification categories were reported.
In this study, a drift case was defined as acute health effects in a person exposed to
pesticide drift from an outdoor agricultural application. Drift exposure included any of the
following pesticide exposures outside their intended area of application: 1) spray, mist, fumes, or
odor during application; 2) volatilization, odor from a previously treated field, or migration of
contaminated dust; and 3) residue left by offsite movement. It should be noted that our drift
definition is broader than EPA’s “spray or dust drift” definition, which excludes post-application
drift caused by erosion, migration, volatility, or windblown soil particles (EPA 2001). A drift
event was defined as an incident where one or more drift cases experienced drift exposure from a
particular source. Both occupational and nonoccupational cases were included. An occupational
case was defined as an individual exposed while at work. Among occupational cases,

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agricultural workers were identified using 1990 and 2002 Census Industry Codes (CIC): (1990
CIC = 010, 011, 030; 2002 CIC = 0170, 0180, 0290) (U.S. Census Bureau 1992, 2005).
The process of case selection is presented in Figure 1. We selected cases if exposed to
pesticides applied for agricultural use including farm, nursery, or animal production, and
excluded cases exposed by ingestion, direct spray, spill, or other direct exposure. We then
manually reviewed all case reports and excluded persons exposed to pesticides used for indoor
applications (e.g., greenhouses, produce packing facilities), persons exposed within a treated area
(e.g., pesticide applicators exposed by pesticides blown back by wind, workers working within
or passing through the field being treated), and persons exposed to pesticides being mixed,
loaded, or transported. Drift cases therefore represented the remaining 9% and 27% of all
pesticide illness cases identified by the SENSOR-Pesticides and PISP, respectively. We also
searched for duplicates from the two programs identifying California cases. Since personal
identifiers were unavailable, date of exposure, age, sex, active ingredients, and county were used
for comparison. A total of 60 events and 171 cases were identified by both California programs.
These were counted only once and were included in the PISP total only.
Drift events and cases were analyzed by the following variables: state, year and month of
exposure, age, gender, location of exposure, health effects, illness severity, pesticide
functional/chemical class, active ingredient, target of application, application equipment,
detection of violations, and factors contributing to the drift incident. EPA toxicity categories
ranging from toxicity I (the most toxic) to IV (the least toxic) were assigned to each product
(EPA 2007). Cases exposed to multiple products were assigned to the toxicity category of the
most toxic pesticide they were exposed to. Illness severity was categorized into low, moderate,
and high using criteria developed by the SENSOR-Pesticides program (Calvert et al. 2010). Low

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severity refers to mild illnesses that generally resolve without treatment. Moderate severity refers
to illnesses that are usually systemic and require medical treatment. High severity refers to lifethreatening or serious health effects that may result in permanent impairment or disability.
Contributing factors were retrospectively coded with available narrative descriptions. One
NIOSH researcher (SJL) initially coded contributing factors for all cases. Next, for SENSORPesticides cases, state health department staff reviewed the codes and edited as necessary. Any
discrepancies were resolved by a second NIOSH researcher (GMC). For PISP cases, relatively
detailed narrative descriptions were available for all incidents. These narratives summarize
investigation reports provided by county agriculture commissioners, who investigate all
suspected pesticide poisoning cases reported in their county. After initial coding, two NIOSH
researchers discussed those narratives that lacked clarity to reach consensus.
Data Analysis
Data analysis was performed with SAS v 9.1. Descriptive statistics were used to
characterize drift events and cases. Incidence rates were calculated by geographic region, year,
sex, and age group. The numerator represented the total number of respective cases in 1998–
2006. Denominators were generated using the Current Population Survey microdata files for the
relevant years (U.S. Census Bureau 2009). For total and nonoccupational rates, the denominators
were calculated by summing the annual average population estimates. A nonoccupational rate for
agriculture-intensive areas was calculated by selecting the five counties in California where the
largest amount of pesticides were applied in 2008 (Fresno, Kern, Madera, Monterey, and Tulare)
(CDPR 2010). For occupational rates, the denominators were calculated by summing the annual
employment estimates including both “employed at work” and “employed but absent.” The
denominator for agricultural workers was obtained using the same 1990/2002 CIC codes used to

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define agricultural worker cases (U.S. Census Bureau 1992, 2005). Moreover, in California
where data on pesticide usage are available, incidence was calculated per number of agricultural
applications and amount of pesticide active ingredient applied (CDPR 2009). Incidence trend
over time was examined by fitting a Poisson regression model of rate on year and deriving the
regression coefficient and its 95% confidence intervals (CIs).
Drift events were dichotomized by the size of events into small events involving < 5
cases and large events involving ≥ 5 cases. This cut point was based on one of the criteria used
by CDPR to prioritize event investigations (CDPR 2001). Illness severity was dichotomized into
low and moderate/high. Simple and multivariable logistic regressions were performed. Odds
ratios (OR) and 95% CIs were calculated.
Results
Number and Incidence of Drift Events and Cases
From 1998 through 2006, we identified 643 events and 2,945 illness cases associated
with pesticide drift from agricultural applications (Figure 1). Of these, 382 events (59%) and 791
cases (27%) were identified by SENSOR-Pesticides (excluding 60 events and 171 cases also
identified by PISP), and 261 events (41%) and 2,154 cases (73%) were identified by PISP. Drift
cases consisted of 53 definite (1.8%), 2,019 probable (68.6%), 823 possible (27.9%), and 50
suspicious (1.7%) cases. Among drift cases, 1,565 (53%) were nonoccupational and 1,380 (47%)
were occupational. Agricultural workers accounted for 73% (n=1,010) of the occupational cases.
A total of 340 events (53%) occurred between May and August and these involved 1,407 cases
(48%).
The overall incidence rate of drift-related pesticide poisoning was 2.93/million personyears (Table 1). The rates of nonoccupational and occupational drift-related pesticide poisoning

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were 1.56 and 2.89, respectively. Among occupational cases, the rate was 114.3 for agricultural
workers and 0.79 for all other workers. Among nonoccupational cases identified in California,
the rate was 42.2 for residents in the 5 agriculture-intensive counties and 0.61 for residents of all
other California counties (data not shown). The rate was highest in the western states for both
nonoccupational and occupational cases (Table 1). In California, per 100,000 agricultural
applications, 1.6 drift events and 11.8 cases were identified; per 10 million pounds applied, 1.9
events and 14.4 cases were identified (data not shown).
The total annual incidence rate ranged from 1.39 to 5.32 per million persons over the 9year time period (Table 1). Over time, the rate of drift cases involved in large events showed the
same pattern as the rate of all drift cases, showing a spike every three years (Figure 2). The rate
of drift cases involved in small events varied within a narrow range from 0.49 to 1.11 and there
was no significant rate change over this time period; however, for the 5 states that provided data
for all 9 years, a significant decrease in the rate was found (i.e., an estimated 9% decrease per
year, 95% CI 3–15%, p = 0.004).
Men comprised 53% of all cases (Table 1). The rate by gender was similar among
nonoccupational cases. For occupational cases, the rate was 1.25 times higher in male workers
than female workers, but 2.89 times higher in female agricultural workers than male agricultural
workers. Among nonoccupational cases, children aged < 15 years accounted for 33% of cases
with known age and showed the highest rate (1.88/million person-years) (Table 1).
Responsible Pesticides, Application Targets, and Application Equipment
In 430 (67%) of 643 drift events, exposure was to pesticides from a single functional
class (Table 2). Insecticides were the most commonly identified (31% of events), accounting for
23% (n=678) of all cases. Fumigants were involved in only 8% of drift events but accounted for

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45% (n=1,330) of all cases. Organophosphorous compounds were the most common pesticide
chemical class involved in drift events (28%). Most cases (66%) were exposed to toxicity I (high
toxicity) pesticides.
For the intended application targets, 71% of events involved applications to fruit,
grain/fiber/grass, or vegetable crops (Table 2). Soil applications accounted for 9% of drift events
and 45% of all cases. For application equipment, aerial applications (e.g., by airplane) were
responsible for 39% of drift events, accounting for 24% of all cases. Chemigation (i.e.,
application via an irrigation system) or soil injectors were used in 7% of drift events and
accounted for 44% of cases. All soil injector events and 95% of chemigation events involved the
use of fumigants applied to soil (data not shown).
Location of Exposure and Health Effects
Common exposure locations were private residences (44%) and farms/nurseries (37%)
(Table 3). More than half of cases experienced ocular (58%) or neurological (53%)
symptoms/signs and illness severity was low for most cases (92%) (Table 3). Moderate/high
severity illness was significantly associated with female sex, older age groups, and exposure to
multiple active ingredients, before and after controlling for other case and pesticide
characteristics (p < 0.05) (Table 4). Compared to fumigants, exposures to herbicides,
insecticides, or multiple classes were significantly associated with moderate/high severity illness.
Table 5 provides the list of 15 active ingredients most commonly found among drift cases and
their distribution according to illness severity.
Size of Drift Events
Most drift events involved a single case (n=387, 60%). For multi-person events, 168
events (26% of the total) involved 2–4 cases, 78 events (12%) involved 5–29 cases, and 10

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events (1.5%) involved ≥ 30 cases. Table 6 provides details on the 10 largest events. Detailed
investigation reports of some of these events are available elsewhere (Barry et al. 2010; CDC
2004; O'Malley et al. 2005). The occurrence of large versus small events (events with ≥5 cases
compared with <5 cases) was significantly associated with the use of fumigants (compared to
insecticides), and applications to soil, small fruit crops, or leafy vegetable crops (compared to
other targets) (p < 0.05) (Table 7).
Contributing Factors to Drift Incidents
Of 299 drift events with information on violations of pesticide regulations, 220 (74%)
had one or more violations and accounted for 2,093 cases (89% of cases with violation
information) (Table 8). However, not all of the observed violations may have directly
contributed to the drift exposure. Factors contributing to the drift exposure were identified in 164
events accounting for 1,544 (52%) cases. Common contributing factors identified for drift events
included applicators’ carelessness near/over non-target sites (e.g., flew over a house, did not turn
off a nozzle at the end of the row), unfavorable weather conditions (e.g., high wind speed,
temperature inversion), and poor communication between applicators/growers and others.
Improper seal of the fumigation site (e.g., tarp tear, early removal of seal), identified in 9 events,
accounted for the largest proportion (60%) of cases with contributing factors identified.
The distance between the application and exposure site was identified in 1,428 (48%)
cases (Table 8). Occupational cases accounted for 68% of cases exposed within 0.25 miles of the
application site, and nonoccupational cases accounted for 73% of cases exposed over 0.25 miles
away.
Discussion
To our knowledge, this is the first comprehensive report of drift-related pesticide

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poisoning in the US. We identified 643 events involving 2,945 illness cases associated with
pesticide drift from outdoor agricultural applications during 1998–2006. Pesticide drift included
pesticide spray, mist, fume, contaminated dust, volatiles and odor that moved away from the
application site during or after the application. While the incidence for cases involved in small
drift events (<5 cases) tended to decrease over time, the overall incidence maintained a
consistent pattern chiefly driven by large drift events. Large drift events were commonly
associated with soil fumigations.
Occupational Exposure
Occupational pesticide poisoning is estimated at 12–21/million U.S. workers per year
(Calvert et al. 2004; Council of State and Territorial Epidemiologists n.d.). Compared to those
estimates, our estimated incidence of 2.89/million worker-years suggests that 14–24% of
occupational pesticide poisoning may be attributed to off-target drift from agricultural
applications. It should be noted that our study included pesticide drift from outdoor applications
only and excluded workers exposed within the application area. Our findings show that the risk
of illness resulting from drift exposure is largely borne by agricultural workers, and the incidence
(114.3/million worker-years) was 145 times greater than that for all other workers. Current
regulations require agricultural employers to protect workers from exposure to agricultural
pesticides, and pesticide product labels instruct applicators to avoid contacting humans directly
or through drift (EPA 2009).
Our study found that the incidence of drift-related pesticide poisoning was higher among
female and younger agricultural workers and in western states. These groups were previously
found to have a higher incidence of pesticide poisoning (Calvert et al. 2008). It is not known why
the incidence is higher among female and younger agricultural workers, but hypotheses include

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that these groups are at greater risk of exposure, that they are more susceptible to pesticide
toxicity, or that they are more likely to report exposure/illness or seek medical attention.
However, consistent patterns were not observed among workers in other occupations, requiring
further research to identify the explanation. The higher incidence in the western states may
suggest that workers in this region are at higher risk of drift exposure; however, it may also have
resulted from better case identification in California and Washington states through their higherstaffed surveillance programs, extensive utilization of workers’ compensation reports in these
states, and use of active surveillance for some large drift events in California.
Nonoccupational Exposure
This study found that more than half of drift-related pesticide poisoning cases resulted
from nonoccupational exposures and 61% of those were exposed to fumigants. California data
suggest that residents in agriculture-intensive regions have a 69 times higher risk of pesticide
poisoning from drift exposure compared to other regions. This may reflect California’s use of
active surveillance for some large drift events. Children were found to have the greatest risk
among nonoccupational cases. The reasons are not known but may be because children have
higher pesticide exposures, greater susceptibility to pesticide toxicity or greater medical attention
seeking by concerned parents. Recently several organizations submitted a petition to the U.S.
EPA asking the agency to evaluate children’s exposure to pesticide drift and adopt interim
prohibitions on the use of drift-prone pesticides near homes, schools, and parks (Goldman et al.
2009).
Contributing Factors
Soil fumigation was a major cause of large drift events, accounting for the largest
proportion of cases. Due to the high volatility of fumigants, specific measures are required to

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prevent emissions after completion of the application. Given the unique drift risks posed by
fumigants, EPA regulates the drift of fumigants separately from non-fumigant pesticides. EPA
recently adopted new safety requirements for soil fumigants which took effect in early 2011, and
include comprehensive measures designed to reduce the potential for direct fumigant exposures,
reduce fumigant emissions, improve planning, training, and communications, and promote early
detection and appropriate responses to possible future incidents (EPA 2010). Requirements for
buffer zones are also strengthened. For example, fumigants that generally require a > 300 foot
buffer zone are prohibited within 0.25 miles (1,320 feet) of “difficult-to-evacuate” sites (e.g.,
schools, daycare centers, hospitals). We found that, of 738 fumigant-related cases with
information on distance, 606 (82%) occurred > 0.25 miles from the application site, which
suggests that the new buffer zone requirements, independent of other measures to increase
safety, may not be sufficient to prevent drift exposure.
This study also showed the need to reinforce compliance with weather-related
requirements and drift monitoring activities. Moreover, applicators should be alert and careful,
especially when close to non-target areas such as adjacent fields, houses, and roads. Applicator
carelessness contributed to 79 events (48% of 164 events where contributing factors were
identified), of which 56 events involved aerial applicators. Aerial application was the most
frequent application method found in drift events, accounting for 249 events (39%). Drift
hazards from aerial applications have been well documented (CDC 2008; Weppner et al. 2006).
Applicators should use all available drift management measures and equipment to reduce drift
exposure, including new validated drift reduction technologies as they become available.
Limitations
This study requires cautious interpretation especially for variables with missing data on

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many cases (e.g., age, violation, contributing factors, distance). This study also has several
limitations. First, our findings likely underestimate the actual magnitude of drift events and cases
because case identification principally relies on passive surveillance systems. Such underreporting might have allowed the totals to be appreciably influenced by a handful of California
episodes in which active case-finding located relatively large numbers of affected people.
Pesticide-related illnesses are underreported due to individuals not seeking medical attention
(because of limited access to health care or mild illness), misdiagnosis, and health care provider
failure to report cases to public health authorities (Calvert et al. 2008). Data from the National
Agricultural Workers Survey suggests that the pesticide poisoning rates for agricultural workers
may be an order of magnitude higher than those identified by the SENSOR-Pesticides and PISP
programs (Calvert et al. 2008). Second, the incidence of drift cases from agricultural
applications may have been underestimated by using crude denominators of total population and
employment estimates which may also include those who are not at risk. On the other hand, the
incidence for agricultural workers may have been overestimated if the denominator data
undercounted undocumented workers. Third, the data may include false-positive cases because
clinical findings of pesticide poisoning are nonspecific and diagnostic tests are not available or
rarely performed. Fourth, when data from SENSOR-Pesticides and PISP were combined, some
duplication of cases and misclassification of variables may have occurred although steps were
taken to identify and resolve discrepancies. Also there may be differences in case detection
sensitivity between SENSOR-Pesticides and PISP since the two programs use slightly different
case definitions. Lastly, contributing factor information was not available for 48% of cases,
either because an in-depth investigation did not occur, or sufficiently detailed findings were not
entered into the database. The retrospective coding of contributing factors was often based on

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limited data and may have produced some misclassification.
Conclusion
The study findings suggest that the incidence of acute illness from off-target pesticide
drift exposure was relatively low during 1998–2006 and most cases presented with low-severity
illness. However, the rate of poisoning from pesticide drift was 69 times higher for residents in 5
agriculture-intensive California counties compared with other counties, and the rate of
occupationally exposed cases was145 times greater in agricultural workers than in nonagricultural workers. These poisonings may largely be preventable through proper prevention
measures and compliance with pesticide regulations. Aerial applications were the most frequent
method associated with drift events, and soil fumigations were a major cause of large drift
events. These findings highlight areas where interventions to reduce pesticide drift could be
focused.

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Chloropicrin Soil Fumigant into a Residential Area --- Kern County, California, 2003.
MMWR 53(32):740-742.
Centers for Disease Control and Prevention. 2008. Acute pesticide poisoning associated with
pyraclostrobin fungicide--Iowa, 2007. MMWR 56(51-52):1343-1345.
Council of State and Territorial Epidemiologists. n.d. Introduction and Guide to the Data Tables
for Occupational Health Indicators. Available:
http://www.cste.org/dnn/ProgramsandActivities/OccupationalHealth/OccupationalHealth
Indicators/tabid/85/Default.aspx [accessed 1December 2009].
Feitshans TA. 1999. An analysis of state pesticide drift laws. San Joaquin Agric L Rev 9:37:3793.
Goldman P, Brimmer JK, Ruiz V. 2009. Pesticides in the air- Kids at risk: Petition to EPA to
protect children from pesticide drift. Available:
http://earthjustice.org/sites/default/files/library/legal_docs/petition-pesticides-in-the-airkids-at-risk.pdf [accessed 17 May 2011].
Harnly ME, Bradman A, Nishioka M, McKone TE, Smith D, McLaughlin R, et al. 2009.
Pesticides in dust from homes in an agricultural area. Environ Sci Technol 43(23):87678774.

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Hofman V, Solseng E. 2001. Reducing spray drift. Available:
http://www.ag.ndsu.edu/pubs/ageng/machine/ae1210w.htm [accessed 16 December
2009].
O'Malley M, Barry T, Ibarra M, Verder-Carlos M, Mehler L. 2005. Illnesses related to shank
application of metam-sodium, Arvin, California, July 2002. J Agromedicine 10(4):27-42.
Quandt SA, Arcury TA, Rao P, Snively BM, Camann DE, Doran AM, et al. 2004. Agricultural
and residential pesticides in wipe samples from farmworker family residences in North
Carolina and Virginia. Environ Health Perspect 112(3):382-387.
U.S. Census Bureau. 1992. 1990 census of population and housing. Alphabetical index of
industries and occupations, Washington, DC: US Department of Commerce.
U.S. Census Bureau. 2005. Industry and Occupation 2002. Washington, DC; United States
Census Bureau. Available:
http://www.census.gov/hhes/www/ioindex/ioindex02/view02.html [accessed 30
November 2008].
U.S. Census Bureau. 2009. Current Population Survey. Available:
http://www.bls.census.gov/cps_ftp.html [accessed 28 October 2010].
U.S. Environmental Protection Agency. 2001. Pesticide registraion (PR) notice 2001-X draft:
Spray and dust drfit lable statements for pesticide products. Available:
http://www.epa.gov/PR_Notices/prdraft-spraydrift801.htm [accessed 30 November
2009].
U.S. Environmental Protection Agency. 2007. Label review manual - Precautionary statements
Available: http://www.epa.gov/oppfead1/labeling/lrm/2007-lrm-chap-07.pdf [accessed 30
November 2009].

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U.S. Environmental Protection Agency. 2009. Pesticides: Health and safety - Worker safety and
training. Available: http://www.epa.gov/opp00001/health/worker.htm [accessed
November 30 2009].
U.S. Environmental Protection Agency. 2010. Implementation of risk mitigation measures for
soil fumigant pesticides.
Available:http://www.epa.gov/oppsrrd1/reregistration/soil_fumigants/ [accessed 1
November 2010]
Weppner S, Elgethun K, Lu C, Hebert V, Yost MG, Fenske RA. 2006. The Washington aerial
spray drift study: children's exposure to methamidophos in an agricultural community
following fixed-wing aircraft applications. J Expo Sci Environ Epidemiol 16(5):387-396.

 Page 22 of 32

22

Table 1. Number and incidence ratea of off-target drift events and pesticide poisoning cases by year, region, sex, and age, 11 States, 1998-2006
Drift Cases
Drift Events

Variable
Total
Year of exposure
(# of states included)
1998 (6)
1999 (6)
2000 (8)
2001 (8)
2002 (8)
2003 (8)
2004 (8)
2005 (9)
2006 (10)
Region
Weste
Southf
East/Centralg
Sex
Male
Female
Unknown
Age
< 15
15–24
25–34
35–44
45–54
55–64
65+
Unknown

Nonoccupational
Cases

All Cases
Population
estimateb
1004.1

Rate
2.93

Count
1,565

Ratec
1.56

Occupational Cases
Ag Worker Casesd
Other Worker Cases
Employment
Employment
Count
estimateb,d
Rate
Count
estimateb
Rate
1,010
8.83
114.33
370
468.0
0.79

Total

Count
643

%
100

Count
2,945

60
82
64
88
81
75
47
70
76

9.3
12.8
10.0
13.7
12.6
11.7
7.3
10.9
11.8

130
407
193
177
580
348
232
642
236

93.6
95.0
110.3
112.6
113.7
116.4
117.4
120.6
124.5

1.39
4.28
1.75
1.57
5.10
2.99
1.98
5.32
1.90

46
273
76
98
271
265
43
409
84

0.49
2.87
0.69
0.87
2.38
2.28
0.37
3.39
0.67

45
72
93
43
281
43
177
168
88

1.11
1.12
1.24
1.12
1.11
0.79
0.75
0.75
0.84

40.46
64.22
74.94
38.47
252.33
54.64
235.33
224.77
104.53

39
62
24
36
28
40
12
65
64

43.2
44.1
51.8
52.5
52.2
53.7
54.7
56.8
59.1

0.90
1.41
0.46
0.69
0.54
0.74
0.22
1.14
1.08

1.90
2.97
2.21
1.47
5.80
1.52
3.41
4.05
2.54

433
193
17
n/a

67.3
30.0
2.6

2,484
426
35

397.9
365.6
240.6

6.24
1.17
0.15

1,240
311
14

3.12
0.85
0.06

933
59
18

4.44
3.25
1.15

210.20
18.17
15.68

311
56
3

1.68
0.33
0.03

6.57
0.66
0.18

1560
1360
25

491.6
512.5
--

3.17
2.65

742
807
16

1.51
1.57

554
448
8

6.90
1.93

80.27
231.90

1.05
0.49

3.16
2.53

--

--

264
105
1

184.9
170.7
112.5
0.0
251.6
216.5

--

--

418
398
453
458
306
164
92
656

221.2
142.0
140.0
156.7
136.1
90.9
117.2

1.89
2.80
3.24
2.92
2.25
1.80
0.78

415
182
140
181
172
103
80
292

1.88
1.28
1.00
1.16
1.26
1.13
0.68

-1.44
1.81
2.08
1.59
1.10
0.81

-126.39
132.53
89.89
49.00
33.61
11.11

--

--

--

--

--

Rate
2.89

n/a

--

--

--

3
182
240
187
78
37
9
274

0
34
73
90
56
24
3
90

a. Per 1,000,000 persons.
b. Numbers (in million) were estimated using the Current Population Survey data. Participating years vary by state. Only years of participation were included.
c. Denominators were population estimates.
d. Cases and employment estimates of agricultural workers were defined with 1990/2002 Census Industry Codes (010, 011, 030; 0170, 0180, 0290).
e. Arizona, California, New Mexico, Oregon, Washington
f. Florida, Louisiana, Texas
g. Iowa, Michigan, New York

-67.8
106.8
122.3
104.6
52.0
14.6

--

--

--

0.50
0.68
0.74
0.54
0.46
0.21

3.12
2.88
2.23
1.26
1.15
0.78

--

--

 Page 23 of 32

23
Table 2. Off-target drift events and pesticide poisoning cases by pesticide and application
characteristics, 11 states, 1998-2006
Drift Events
(n=643)
Variable
Pesticide functional class
Insecticide only
Herbicide only
Fungicide only
Fumigant only
Other, single
Multiple
Unknown
Common pesticide chemical classa
Organophosphorous compound
Inorganic compound
Pyrethroid
Dithiocarbamatesb
N-methyl carbamates
Chlorophenoxy compound
Triazines
Maximum toxicity category
I
II
III
Unknown
Application target
Fruit crops
Grain/fiber/grass crops
Vegetable crops
Soil
Landscape/forest
Undesired plants
Other (e.g., misc. crops, seed, livestock farm)
Unknown
Application equipment
Aerial applicator
Handheld or backpack sprayer
Chemigation
Soil injector
Other ground applicator
Multiple
Unknown

Total
(n=2,945)
N
%

Drift Cases
Occupational Nonoccupational
(n=1,380)
(n=1,565)
%
%

N

%

198
108
29
52
43
207
6

30.8
16.8
4.5
8.1
6.7
32.2
0.9

678
195
64
1,330
87
585
6

23.0
6.6
2.2
45.2
3.0
19.9
0.2

32.9
4.0
3.7
27.0
2.8
29.4
0.2

14.3
8.9
0.8
61.2
3.1
11.4
0.2

181
87
52
47
33
26
11

28.1
13.5
8.1
7.3
5.1
4.0
1.7

660
231
207
726
71
47
34

22.4
7.8
7.0
24.7
2.4
1.6
1.2

36.7
11.1
9.6
22.5
4.1
0.9
1.1

9.8
5.0
4.7
26.5
1.0
2.2
1.2

203
167
154
119

31.6
26.0
24.0
18.5

1,944
468
327
206

66.0
15.9
11.1
7.0

59.9
21.2
13.6
5.2

71.4
11.2
8.9
8.6

189
185
85
55
32
29
27
41

29.4
28.8
13.2
8.6
5.0
4.5
4.2
6.4

588
411
374
1,337
64
44
66
61

20.0
14.0
12.7
45.4
2.2
1.5
2.2
2.1

27.6
12.8
22.9
27.5
2.8
0.9
2.0
3.6

13.2
15.0
3.7
61.2
1.7
2.0
2.5
0.8

249
24
22
20
254
8
66

38.7
3.7
3.4
3.1
39.5
1.2
10.3

695
63
752
558
747
41
89

23.6
2.1
25.5
18.9
25.4
1.4
3.0

32.0
3.8
16.4
10.0
32.6
0.2
4.9

16.2
0.6
33.5
26.8
19.0
2.4
1.4

a. Categories with the largest numbers of cases. Events/Cases can be exposed to multiple categories.
b. Mostly from single products.

 Page 24 of 32

24
Table 3. Location of exposure, health effects, and illness severity of drift cases (n=2,945)
Variable
Location of exposure
Private residence
Farm/Nursery
Road/Right-of-way
School
Agricultural processing facility
Other/Unknown
Health effecta
Eye (e.g., pain/irritation/inflammation, lacrimation)
Neurological (e.g., headache, paresthesia, dizziness)
Respiratory (e.g., dyspnea, respiratory tract pain/irritation, cough)
Gastrointestinal (e.g., vomiting, nausea, diarrhea, abdominal pain)
Skin (e.g., pruritus, pain/irritation, rash)
Cardiovascular (e.g., chest pain)
Other (e.g., fatigue, fever)
Illness severity
Low
Moderate
High
a. Cases can be included in multiple categories.

%
44.5
36.7
5.6
3.6
2.4
7.2
58.2
52.8
47.8
41.5
14.7
5.1
11.4
92.2
7.3
0.5

 Page 25 of 32

25
Table 4. Illness severity by case and pesticide characteristics
High/Moderate
Severity (n=230)
N
%

Variable
Sexa
Female
Male
Age
< 15
15-24
25-34
35-44
45-54
55-64
65+
Unknown
Work-related
Yes
No/Unknown
No. of active ingredients
One
More than one
Pesticide functional class
Fumigant
Herbicides
Insecticide
Fungicides
Multiple
Other/Unknown
a. Excluded unknown cases.
b. Adjusted for all other variables.

Low severity
(n=2,715)
N
%

OR

High/Moderate severity (versus Low)
95% CI
aORb
95% CI

126
104

54.8
45.2

1,234
1,456

45.5
53.6

1.43
Ref

(1.09,1.87)

16
28
48
48
38
21
16
15

7.0
12.2
20.9
20.9
16.5
9.1
7.0
6.5

402
370
405
410
268
143
76
641

14.8
13.6
14.9
15.1
9.9
5.3
2.8
23.6

Ref
1.90
2.98
2.94
3.56
3.69
5.29
0.59

126
104

54.8
45.2

1,254
1,461

46.2
53.8

1.41
Ref

90
140

39.1
60.9

1,719
996

63.3
36.7

Ref
2.72

(2.07,3.58)

Ref
1.42

(1.02,1.99)

35
33
79
2
71
10

15.2
14.3
34.3
0.9
30.9
4.3

1,295
162
599
62
514
83

47.7
6.0
22.1
2.3
18.9
3.1

Ref
7.54
4.88
1.19
5.11
4.46

(4.56,12.46)
(3.24,7.35)
(0.28,5.08)
(3.37,7.76)
(2.13,9.32)

Ref
4.10
3.34
0.77
3.09
2.82

(2.34,7.19)
(2.10,5.32)
(0.18,3.37)
(1.85,5.16)
(1.29,6.15)

(1.01,3.57)
(1.66,5.33)
(1.64,5.27)
(1.95,6.52)
(1.87,7.27)
(2.54,11.03)
(0.29,1.20)
(1.08,1.85)

1.53
Ref
Ref
1.34
1.95
1.91
2.34
2.42
3.67
0.63
0.99
Ref

(1.15,2.04)

(0.68,2.62)
(1.02,3.71)
(1.02,3.58)
(1.24,4.41)
(1.20,4.91)
(1.72,7.86)
(0.30,1.33)
(0.70,1.40)

 Page 26 of 32

26
Table 5. Fifteen most common active ingredients for drift cases and percentage of high/moderate severity
Active ingredient

Functional class
Metam-sodium
Fumigant
Chloropicrin
Fumigant
Chlorpyrifos
Insecticide
Sulfur
Insecticide/Fungicide
Mancozeb
Fungicide
Methamidophos
Insecticide
Malathion
Insecticide
Spinosad
Insecticide
Methyl-bromide
Fumigant
Dimethoate
Insecticide
Cyfluthrin
Insecticide
Methomyl
Insecticide
Atrazine
Herbicide
lambda-Cyhalothrin
Insecticide
Propargite
Acaricide/miticide
a. Can be exposed to other active ingredients also.
b. High (n=7), Moderate (n=83)

Chemical class
Dithicarbamate
Trichloronitromethane
Organophosphate
Inorganic compound
Dithicarbamate
Organophosphate
Organophosphate
Spinosyn
Alkyl bromide
Organophosphate
Pyrethroid
N-methyl carbamate
Triazine
Pyrethroid
Sulfite ester

Casesa
(N=2,945)
664
637
240
147
144
133
122
107
84
68
59
56
54
52
52

Cases exposed to single active ingredient
Total
% of High/Moderate
(n=1,809)
Severity (n=90)b
664
3
532
1
49
10
32
25
4
0
0
0
96
11
1
0
11
27
10
20
2
0
13
15
8
0
39
3
10
30

 Page 27 of 32

27

Table 6. 10 largest drift events, 1998-2006
State

Year

California
California
California
California
California
California
California
California
California
Texas

1999
2000
2002
2002
2003
2004
2005
2005
2005
2005

Total
(n=1,293)
170
33
250
123
161
122
324
42
34
34

Cases
Occupational
(n=452)
6
33
72
123
10
122
1
42
34
9

Pesticide application
Non-occupational
(n=841)
164
0
178
0
151
0
323
0
0
25

Target

Equipment

Active ingredient

Soil
Almonds
Soil
Soil
Soil
Potatoes
Soil
Soil
Oranges
Cotton

Chemigation
Aerial application
Soil injector
Chemigation
Soil injector
Aerial application
Chemigation
Chemigation
Ground sprayer
Ground sprayer

Metam-sodium
Chlorpyrifos, propargite
Metam-sodium
Metam-sodium
Chloropicrin
Methamidophos
Chloropicrin
Metam-sodium
Cyfluthrin, spinosad
Lambda-cyhalothrin

 Page 28 of 32

28

Table 7. Factors associated with large drift events (≥5 cases)
Small Event (n=555)

Large Event (n=88)

Large Event
(versus Small)
OR
(95% CI)

N
%
N
%
Pesticide functional class
Insecticide
172
31.0
26
29.5
Ref
Fumigant
29
5.2
23
26.1
5.25
(2.64,10.41)
Multiple combination
178
32.1
29
33.0
1.08
(0.61,1.91)
Other single pesticide class or unknown
176
31.7
10
11.4
0.38
(0.18,0.80)
Application target
Soil
31
5.6
24
27.3
8.50
(4.57,15.79)
Small fruit cropsa
38
6.8
14
15.9
4.04
(2.03,8.06)
Leafy vegetable cropsb
25
4.5
8
9.1
3.51
(1.49,8.27)
Otherc
461
83.1
42
47.7
Ref
Application method
Aerial application
223
40.2
26
29.5
0.91
(0.54,1.53)
Chemigation
20
3.6
22
25.0
8.58
(4.31,17.09)
Otherd
312
56.2
40
45.5
Ref
a. e.g., berries, grapes, currant.
b. e.g., beets, celery, broccoli, lettuce, spinach
c. Includes tall fruit or other vegetable crops, other crop categories, landscape/forest, undesired plants, livestock farms, unknown.
d. Includes other ground application equipment, multiple, and unknown.

 Page 29 of 32

29
Table 8. Violation in and contributing factors to occurrence of drift incidents/exposures
Drift Events
(n=643)
Variable
Violation of federal/state pesticide regulation
Yes
No
Unknown/Pending

N
220a
79
344

At least one contributing factor identifiedb
Applicator carelessness near non-target sitesc
By aerial applicator
Weather (wind, temperature inversion)
Poor/ineffective communication
Improper seal of fumigation sited
Inappropriate monitoringe
Applicator not properly trained or supervised
Excessive application
Use of inadequate equipmentf
Otherg

164
79
56
75
19
9
7
5
4
2
8

Distance from application site
≤ 50 feet
> 50–100 feet
> 100–300 feet
> 300 feet–0.25 mile
> 0.25–0.5 mile
> 0.5–1 mileh
> 1 milei

n/a

%

Occupational
(n=1,380)
N %

Drift Cases
Nonoccupational
(n=1,565)
N %

73.6
26.4

971
164
245

85.6
14.4

1122
82
361

93.2
6.8

(100)
(48.2)
(34.1)
(45.7)
(11.6)
(5.5)
(4.3)
(3.0)
(2.4)
(1.2)
(4.9)

486
49
21
309
102
94
118
45
20
125
28

(100)
(10.1)
(4.3)
(63.6)
(21.0)
(19.3)
(24.3)
(9.3)
(4.1)
(25.7)
(5.8)

1,058
98
66
593
11
837
199
0
6
2
206

(100)
(9.3)
(6.2)
(56.0)
(1.0)
(79.1)
(18.8)
(0.0)
(0.6)
(0.2)
(19.5)

700
66
77
113
267
175
0
2

(100)
(9.4)
(11.0)
(16.1)
(38.1)
(25.0)
(0.0)
(0.3)

728
54
29
69
93
256
116
111

(100)
(7.4)
(4.0)
(9.5)
(12.8)
(35.2)
(15.9)
(15.2)

Note: Percentages in parentheses were calculated only among cases with available data
a. 159 (72%) were identified by the California Department of Pesticide Regulation
b. Cases can be included in multiple categories.
c. e.g., the applicator didn't turn off a nozzle at the end of the row, the crop duster flew overhead.
d. e.g., leakage from torn tarp, early removal of seal, use of contaminated water
e. e.g., did not measure wind speed, did not monitor drift from the application site
f. e.g., used longer spray boom than specified on the label, used sprinklers without required calibration device.
g. e.g., treated additional rows without permission, permeable soil type, aerial application with very low height, building/vehicle
ventilator system sucking outside air in
h. Cases are from three events in California, Louisiana, and Washington.
i. Cases are from two events in California.

 Page 30 of 32

30
Figure 1. Eligible pesticide drift events and cases, 11 States, 1998-2006

Figure 2. Incidence rate of pesticide poisoning associated with off-target drift
exposure over time, 11 states, 1998-2006

 Page 31 of 32

Figure 1. Eligible pesticide drift events and cases, 11 States, 1998-2006
190x142mm (300 x 300 DPI)

 Page 32 of 32

Figure 2. Incidence rate of pesticide poisoning associated with off-target drift exposure over time,
11 states, 1998-2006
50x13mm (300 x 300 DPI)