AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 51:883–898 (2008)



# Acute Pesticide Poisoning Among Agricultural Workers in the United States, 1998–2005

GeoffreyM. Calvert, MD , MPH, 1  Jennifer Karnik, MPH , 1 Louise Mehler, PHD , MD , 2 John Beckman, BS , 3 Barbara Morrissey, MS , 4 Jennifer Sievert, BA , 5 Rosanna Barrett, MPH , 6 Michelle Lackovic, MPH , 7 Laura Mabee, BA , 8 AbbySchwartz, MPH , 9 Yvette Mitchell, MS , 10 and Stephanie Moraga-McHaley, MS 11



### Background Approximately 75% of pesticide usage in the United States occurs in agriculture. As such, agricultural workers are at greater risk of pesticide exposure than non-agricultural workers. However, the magnitude, characteristics and trend of acute pesticide poisoning among agricultural workers are unknown. Methods We identified acute pesticide poisoning cases in agricultural workers between the ages of 15 and 64 years that occurred from 1998 to 2005. The California Department of Pesticide Regulation and the SENSOR-Pesticides program provided the cases. Acute occupational pesticide poisoning incidence rates (IR) for those employed in agriculture werecalculated, as were incidence rate ratios (IRR) among agricultural workers relative to nonagricultural workers. Results Of the 3,271 cases included in the analysis, 2,334 (71%) were employed as farmworkers. The remaining cases were employed as processing/packing plant workers (12%), farmers (3%), and other miscellaneous agricultural workers (19%). The majority of cases had low severity illness (N 1⁄4 2,848, 87%), while 402 (12%) were of medium severity and 20 (0.6%) were of high severity. One case was fatal. Rates of illness among various agricultural worker categories were highly variable but all, except farmers, showed risk for agricultural workers greater than risk for non-agricultural workers by an order of magnitude or more. Also, the rate among female agricultural workers was almost twofold higher compared to males. Conclusion The findings from this study suggest that acute pesticide poisoning in the agricultural industry continues to be an important problem. These findings reinforce the need for heightened efforts to better protect farmworkers from pesticide exposure. Am. J. Ind. Med. 51:883–898, 2008. Published 2008 Wiley-Liss, Inc. {



### KEY WORDS: pesticides; surveillance; poisoning; agriculture; farmworkers

Published 2008 Wiley-Liss,Inc. {This article is a US Government work and, as such, isin the public domain in the United States of America. 9 Division of Environmental Health, Michigan Department of Community Health, Lansing, Michigan

10 Bureau of Occupational Health, NewYork State Department of Health,Troy, NewYork
11 NewMexico Occupational Health Registry, University of NewMexico, Albuquerque, NewMexico

The findings and conclusions inthisreport are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health or each author’s state agency.

*Correspondence to: Geoffrey M. Calvert, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, R-17, Cincinnati, OH 45226. E-mail: jac6 @ cdc.gov Accepted 23 June 2008

DOI10.1002/ajim.20623. Published online in Wiley InterScience (www.interscience.wiley.com) 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 Department of Pesticide Regulation, California Environmental Protection Agency, Sacramento, California

3 Public Health Institute, Oakland, California
4Office of Environmental Assessments,Washington State Department of Health,Olympia, Washington

5 Environmental and Injury Epidemiology and Toxicology Branch, Texas Department of State Health Services, Austin,Texas

6 Florida Department of Health,Tallahassee, Florida
7 Louisiana Department of Health and Hospitals, NewOrleans, Louisiana
8Office of Environmental Public Health, Oregon Department of Human Services, Portland, Oregon

### INTRODUCTION

Pesticides are widely used in agriculture to control insects, microorganisms, fungi, weeds, and other pests. The control of these pests serves to increase crop yield and decrease manual labor [Litchfield, 2005]. In 2000 and 2001, over 5 billion pounds of pesticides were used annually throughout the world. The United States was responsible for 24% of this total usage [Kiely et al., 2004]. Within the US, the agricultural industry accounts for approximately 75% of the annual poundage used. Farming is an essential component of our economy, but agricultural workers suffer elevated rates of injuries, hearing loss, and respiratory disease [Rust, 1990; Linaker and Smedley, 2002; Tak and Calvert, 2008]. Pesticides are also an important source of injury and illness among farmers and farm workers [Calvert et al., 2004]. Previous work has suggested that the agricultural industry’s disproportionately high pesticide use puts farmers and farm workers at greater risk of pesticide exposure than others [Reeves and Schafer, 2003; Calvert et al., 2004]. Farmers and farmworkers may be exposed by mixing, loading and applying pesticides, or while performing duties not involved with pesticide application (e.g., weeding, harvesting, thinning, irrigating, or planting). Recognizing the need for increased worker protections from pesticide exposures, the U.S. Environmental Protection Agency (EPA) promulgated rules in 1974 known as the Worker Protection Standard for Agricultural Pesticides (WPS; 40 CFR 170) and aimed at reducing pesticide exposures among agricultural workers. However, by 1992, EPA estimated that hired farmworkers alone experienced up to 10,000–20,000 illnesses and injuries from pesticide exposures each year [US EPA, 1992] and concluded that the WPS was inadequate in its requirements and scope of coverage. That year, EPA revised and expanded the WPS rules to include changes in labeling, coverage of more workers and agricultural operations, prohibition of employer retaliation against workers attempting to comply with the standard, and the following requirements: notification of workers about pesticide applications; restriction of re-entry into pesticide-treated areas; and, provision of personal protective equipment (PPE), decontamination supplies, emergency assistance, and pesticide safety training. Detailed information on the magnitude, characteristics and trend of acute pesticide poisoning since the revised WPS went into effect in 1995 are unavailable. The National Institute for Occupational Safety and Health (NIOSH) developed the Sentinel Event Notification Systemfor Occupational Risks-Pesticides (SENSOR-Pesticides) program [Calvert et al., 2001] to monitor risks from pesticide exposure. Data from this program are available beginning in 1998, when standardized definitions for cases and data elements were adopted [Calvert et al., 2001]. The California Department of Pesticide Regulation (CDPR) has a similar surveillance program that has been tracking pesticide-related illnesses for more than 30 years [Calvert et al., 2001]. To assess the magnitude, characteristics and trend of acute pesticide poisoning among agricultural workers in the United States since the revised WPS went into effect in 1995, an analysis of data obtained from these surveillance systems was performed.



### MATERIALS AND METHODS

Data were obtained on individuals age 15 through 64 who developed an acute pesticide-related illness or injury and whowere employed in the agricultural industry when the occupational pesticide exposure occurred. Census 1990 industry codes (1990 CIC) and Census 2002 industry codes (2002 CIC) were used to identify cases employed in agriculture [US Bureau of the Census, 1992; US Census Bureau, 2005]. The agricultural industry was defined as: agricultural production, excluding livestock (1990 CIC 1⁄4 010; 2002 CIC 1⁄4 0170); agricultural production, including livestock (1990 CIC 1⁄4 011; 2002 CIC 1⁄4 0180); and agricultural services (1990 CIC 1⁄4 030; 2002 CIC 1⁄4 0290). All agricultural industry cases also had their occupation coded using Census 1990 occupation codes (1990 COC) and Census 2002 occupation codes (2002 COC) [US Bureau of the Census, 1992; US Census Bureau, 2005]. Agricultural occupations included: farmworkers (1990 COC 1⁄4 477, 479, 484; 2002 COC 1⁄4 6050, 6120, 8710, 8960); farmers (1990 COC 1⁄4 473–476; 2002 COC 1⁄4 0200, 0210); processing/packing plant workers (1990 COC 1⁄4 488, 699; 2002 COC 1⁄4 6040, 7830, 7850, 8640, 8720, 8800, 8860, 9640); and, other miscellaneous agricultural workers (workers employed in agriculture but whose 1990 COC and 2002 COC did not match any of those specified for the other three agricultural occupations). A pesticide handler was defined as an individual who mixed, loaded, transported and/or applied pesticides, or an individual who repaired or maintained pesticide application equipment at the time of pesticide exposure (insufficient information was available to determine pesticide handler status for 68 individuals). This analysisexcluded illnesses associated with non-occupational exposures and illnesses associated with intentional (e.g., suicidal, malicious intent) exposures. Cases under 15 years of age and those 65 years and older were omitted from analysis. The age range was chosen a priori, and is considered to include the vast bulk of workers who are gainfully employed. A total of 66 cases age 65 and older were identified but not included in this analysis (this represents a rate of 13/100,000 agricultural workers age 65 and older). Furthermore, Current Population Survey (CPS) data, the source of our denominator data, are unavailable on workers less than 15 years of age.



### Data Sources

Data for this analysis were obtained from CDPR and the SENSOR-Pesticides program. State health departments in 884 Calvert et al.ten states participated in the SENSOR-Pesticides program and contributed data. These ten state health departments were the: Arizona Department of Health, California Department of Public Health (CDPH), Florida Department of Health, Louisiana Department of Health and Hospitals, Michigan Department of Community Health, New Mexico Department of Health (through an agreement with the University of New Mexico), New York State Department of Health, Oregon Department of Human Services, Texas Department of State Health Services, and the Washington State Department of Health. The time frame for data availability varied according to state agency. The years of data availability are provided in Table I. Each of these agencies maintains its own passivepopulation-based surveillance system for acute pesticiderelated illness or injury with occasional outreach to potential reporters to stimulate reporting (e.g., contacting poison control centers to encourage them to report or reviewing physician reports submitted to workers’ compensation insurance carriers to identify eligible cases) [Calvert et al., 2001, 2004]. Each agency obtains case reports from manydifferent sources. All require physician reporting of pesticide-related illness cases. Other sources of case reports vary by state and include poison control centers, state agencies with jurisdiction over pesticide use (e.g., departments of agriculture), and workers’ compensation claims. Because each state removes any personal identifiers from the data prior to submission to the Centers for Disease Control and Prevention this study was exempt from consideration by the federal Human Subjects Review Board. Once a case report is received, the state agency determines whether the subject was symptomatic and whether the involved chemical is a pesticide. If so, attempts are made to interview the poisoned subject or their proxy to obtain details on the poisoning event, and any medical records are requested. Besides identifying, classifying, and tabulating pesticide poisoning cases, the states periodically perform in-depthinvestigations of pesticide-related events, and develop interventions aimed at particular industries or pesticide hazards. Cases obtained from CDPR were cross-referenced with cases from the CDPH based on age, gender, date of exposure, and pesticide name. Matching cases were assumed to be the same individual and were counted only once.



### Information Available on Each Case

Data collected for each case by the SENSOR-Pesticides and CDPR surveillance systems include case demographics, signs and symptoms of illness or injury, illness severity, EPA toxicity category, identity of implicated pesticides and the target (e.g., crop) of their application (if any), information on factors that may have contributed to the pesticide exposure that precipitated illness, and the source of the case report. EPA evaluates the toxicity of and assigns a toxicity category to each pesticide product. The categories range from I to IV, with I representing the most toxic and IV theleast toxic substances [US EPA, 1975]. The toxicity category for each case was obtained by the relevant state agency conducting pesticide poisoning surveillance. When toxicity category data was not given, the category was determined by NIOSH based on standardized criteria from a dataset provided by EPA. Cases exposed to more than one pesticide product were assigned the toxicity category representing the pesticide product with the greatest toxicity.



### Case Definition

A standardized case definition is used by all participatingSENSOR-pesticides states. Cases of acute pesticide poisoning are included in the analyses if they were classified as definite, probable, possible or suspicious. A classification category is assigned to a case based on three factors: (1) the strength of evidence that a pesticide exposure occurred; (2) whether adverse health effects were observed by a healthcare professional versus being self-reported; and (3) the presence of sufficient evidence that the known toxicology of the agent was consistent with the observed health effects. Cases exposed to pesticides for which there is limited toxicological data were classified as suspicious [CDC, 2001a]. CDPR uses a comparable case definition [CDPR, 2006]. In this article, acute pesticide poisoning and acute pesticide-related illness and injury are used interchangeably.Illness severity was assigned to all cases using standardized criteria which were based on signs and symptoms, medical care received, and lost time from work [CDC, 2001b]. Low severity illness/ injury consist of illnesses and injuries that generally resolve without treatment and where minimal time ( < 3 days) is lost from work. Such cases typically manifest as eye, skin and/or upper respiratory irritation. Moderate severity illness/injury consists of nonlife-threatening health effects that are generally systemic and require medical treatment. No residual disability is detected, and time lost from work is less than 6 days. High severity illness/injury consists of life threatening health effects that usually require hospitalization, involve substantial time lost from work ( > 5 days), and may result in permanent impairment or disability. Death pertains to fatalities resulting from exposure to one or more pesticides.


### Data Analysis

SAS v. 9.1 was used for data management and analysis [SAS Institute Inc, 2003]. Chi square statistical analyses were performed on categorical data. Incidence rates (IR) for acute occupational pesticide poisoning were calculated for those employed in agriculture. Rates were calculated for occupational categories within agriculture, for each year studied, by age group, and for three geographic regions in the US. The numerator represents the number of relevant cases Pesticide Poisoning Among Agricultural Workers 885TABLE I. Data on Demographics, PesticideToxicity, Pesticide Handler, Pesticide Functional Class, and ApplicationTarget for 3,271Acute Pesticide Poison ing Cases in the Agricultural Industry by Severity Category,1998^2005

Fatal, N High Severity, N Medium Severity, N Low Severity, N Total, N (%) a

Total 1 20 402 2,848 3,271 Age

15^17 0 0 5 19 24 (1) 18^24 0 1 82 521 604 (18) 25^34 0 2 109 786 897 (27) 35^44 0 7 103 630 740 (23) 45^54 0 3 59 358 420 (13) 55^64 1 5 28 138 172 (5) Unknown 0 2 16 396 414 (13) State where illness identified (years of data availability)

Arizona (1998^1999) 0 0 4 17 21 (1) California (1998^2005) 1 10 274 2,235 2,520 (77) Florida (1998^2005) 0 0 23 109 132 (4) Louisiana (2001^2005) 0 4 14 27 45 (1) Michigan (2001^2005) 0 1 7 14 22 (1) NewMexico (2005 only) 0 0 2 10 12 (1) NewYork (1998^2005) 0 0 6 7 13 (1) Oregon (1998^2005) 0 0 6 37 43 (1) Texas (1998^2005) 0 3 40 146 189 (6) Washington (2001^2005) 0 2 26 246 274 (8)
Gender

Female 0 6 114 934 1,054 (32) Male 1 14 288 1,886 2,189 (67) Unknown 0 0 0 28 28 (1) Year exposed

1998 0 2 64 358 424 (13) 1999 1 1 85 337 424 (13) 2000 0 4 64 315 383 (12) 2001 0 0 30 236 266 (8) 2002 0 0 26 576 602 (18) 2003 0 0 43 279 322 (10) 2004 0 11 35 396 442 (14) 2005 0 2 55 351 408 (12) Toxicity categoryb

I 1 11 232 1,418 1,662 (51) II 0 1 68 599 668 (20) III and IV 0 6 82 792 880 (27) Unknown 0 2 20 39 61 (2)
Pesticide handler

Yesc 1 10 190 867 1,068 (33) No 0 10 200 1,925 2,135 (65) Unknown 0 0 12 56 68 (2)
Pesticide functional class d

InsecticidesEall 1 10 210 1,540 1,761 (54)

Insecticides only 0 7 115 747 869 (27) Insecticides combined 1 3 95 793 892 (27) FungicidesEall 1 4 90 734 829 (25)

Fungicides only 0 2 28 147 177 (5) Fungicides combined 1 2 62 587 652 (20) 886 Calvert et al.captured by CDPR and SENSOR-Pesticides from 1998 to 2005. Denominator data, including employment counts and the hours worked estimate, were obtained from the CPS[BLS, 2007]. The hours worked data were used to derive fulltime equivalent (FTEs) estimates, with one FTE equivalent to 2,000 hr worked. Denominator data correspond to the states and time periods of data availability (Table I). Although rates were calculated with the two denominator estimates (employment counts and FTE estimates), the rates calculated with FTEs as the denominator are given prominence as they have previously been shown to be conceptually preferable over the use of raw employment counts [Ruser, 1998]. The comparison group consisted of all workers not employed in agriculture. IR for workers employed in non-agricultural industries were similarly calculated, with the numerator anddenominator data obtained from the same agencies (SENSOR/CDPR and CPS, respectively) that provided the data on agricultural workers. Finally, incidence rate ratios (IRR) were calculated to determine the risk of acute pesticide poisoning while working in agriculture. This ratio was calculated by dividing the IR among agricultural workers with that among non-agricultural workers. A ratio greaterthan one suggests an increased risk in farmers or farmworkers, while a ratio less than one suggests a decreased risk. Confidence intervals (95% CIs) were calculated for each rate ratio as described by Rothman [1986].



### RESULTS

From 1998 to 2005, 3,271 case reports met inclusion criteria (Table I). Of these, 1,078 (33%) were identified by the SENSOR-Pesticides program and 2,193 (67%) originated from CDPR (527 cases were identified by both SENSOR and CDPR and were included in the CDPR total only). There were 1,942 separate pesticide exposure events, 1,762 of which (91%) involved only one ill agricultural worker. Of the DisinfectantsEall 0 2 56 389 447 (14)

Disinfectants only 0 2 48 238 288 (9) Disinfectants combined 0 0 8 151 159 (5) HerbicidesEall 0 1 56 400 457 (14)

Herbicides only 0 1 42 318 361 (11) Herbicides combined 0 0 14 82 96 (3) FumigantsEall 0 4 44 416 464 (14)

Fumigants only 0 4 44 416 464 (14) Fumigants combined 0 0 0 0 0 (0) Other 0 1 18 130 149 (5) Application target

Fruit crops 0 3 112 1,047 1,162 (36) Vegetable crops 0 2 45 411 458 (14) Soil 0 2 20 316 338 (10) Grains, grasses and fiber crops 0 1 58 201 260 (8) Landscape/ornamental 0 1 18 159 178 (5) Undesired plant 0 0 6 74 80 (2) Beverage crops 0 0 7 35 42 (1) Crops that cross categories 0 0 6 32 38 (1) Building structure/surface/space 0 1 8 35 44 (1) Oil crops 0 0 5 15 20 (1) Miscellaneousfield crops 0 0 8 11 19 (1) Veterinary (livestock or domestic) 0 0 4 13 17 (1) Other 1 2 18 182 203 (6) Not applicable 0 4 55 161 220 (7) Unknown 0 4 32 156 192 (6)

aPercentages may not sum to100 due to rounding.
bAcute pesticide toxicity category as defined by the U.S. EPA.

cA pesticide handler was defined as an individual who mixed, loaded, transported and/or applied pesticides, or an individual who repaired or maintained pesticide application equipment at the time of pesticide exposure.
dCases may be exposed to more than one functional class. The rows labeled with ‘‘combined’’ pertain to cases exposed to more than one pesticide active ingredient, some of which belong to the pesticide functional class specified in the row label and others belonging to other pesticide functional classes. TABLE I. ( Continued )

Fatal, N High Severity, N Medium Severity, N Low Severity, N Total, N (%) a Pesticide Poisoning Among Agricultural Workers 887180 (9%) multi-victim events, the median number of ill agricultural workers was 3 (range 2–123). The number of pesticide exposure events decreased over the time period studied but the average number of cases per event increased (in 1998 there were 308 events with an average of 1.4 cases per event whereas in 2005 there were 209 events with an average of 2.0 cases per event).


### Description of the Three Largest Events

More than three quarters of the cases (N 1⁄4 2,520, 77%) occurred in California. Among these cases, we found a small number of events that exposed large numbers of agricultural workers. In two separate 2002 incidents, irritant vapors drifted from soil treatments with metam-sodium and caused low severity illness in 123 vineyard workers and in 72 workers at a carrot processing facility, respectively [see O’Malley et al., 2005 for detailed information on the event involving 72 workers]. The second largest incident occurred in 2004, when 121 peach harvesters became ill after exposure to drift from an application of methamidophos and mancozeb to a nearby potato field. Most of these workers experienced low severity illness (N 1⁄4 111, 92%), and the other 10 workers (8%) experienced moderate severity illness.



### Incidence Rates

Tables II and III and Figure 1 summarize IRs for agricultural workers and non-agricultural workers from 1998 to 2005. Overall, the average annual IR among agricultural workers was 53.6/100,000 FTEs and 1.38/100,000 FTEs among all non-agricultural workers combined (IRR 1⁄4 38.9 95% CI 37.2, 40.6). Agricultural workers’ annual rates fluctuated between 33.8/100,000 FTEs (2001) and 79.9/

TABLE II. Incidence Rates by Industry,Year of Exposure, Age Group and US Region for 3,271Acute Pesticide Poisoning Cases,1998^2005

Agricultural workers Non-agricultural workers

Incidence rate
ratio d Count FTE
estimate a Incidence
rate b Count FTE
estimate a Incidence
rate c

Year of exposure

1998 424 790,837 53.6 762 40,792,468 1.9 28.7 1999 424 781,985 54.2 656 42,040,152 1.6 34.7 2000 383 781,654 49.0 577 41,041,774 1.4 34.9 2001 266 787,481 33.8 552 49,456,474 1.1 30.3 2002 602 753,595 79.9 598 49,110,280 1.2 65.6 2003 322 756,610 42.6 694 50,151,930 1.4 30.8 2004 442 735,270 60.1 716 50,989,934 1.4 42.8 2005 408 710,851 57.4 638 53,000,554 1.2 47.7 Age group (years)

15^17 24 99,364 24.2 69 3,140,858 2.2 11.0 18^24 604 792,852 76.2 851 43,536,103 2.0 39.0 25^34 897 1,392,263 64.4 1,246 92,090,687 1.4 47.6 35^44 740 1,601,894 46.2 1,303 106,763,138 1.2 37.9 45^54 420 1,276,042 32.9 968 89,437,936 1.1 30.4 55^64 172 935,868 18.4 356 41,614,845 0.9 21.5
Unknow n 414 E E 400 E E E USregion

Weste 2,858 3,168,485 90.2 3,556 149,655,538 2.4 38.0
Southf 366 2,258,774 16.2 1,225 141,962,800 0.9 18.8
Eastg 45 671,024 7.0 412 84,965,229 0.5 13.8 Total 3,271 6,098,283 53.6 5,193 376,583,567 1.4 38.9

aFTE, full-time equivalent.
b Incidence rate per100,000 FTEs. Includes agricultural workers in Arizona, California, Florida, Louisiana, Michigan, New Mexico, New York, Oregon,Texas, and Washington.

c Incidence rate per100,000 FTEs. Includes non-agricultural workers in Arizona, California, Florida, Louisiana, Michigan, New Mexico, New York, Oregon,Texas, and Washington.
dCompares the rate of acute pesticide poisoning among agricultural workers for a given year with non-agricultural workers. Cases are identified by participating SENSORPesticides states and CDPR. All IRRs were significantly elevated ( P < 0.0001).

eArizona, California, NewMexico, Oregon, and Washington.

f Florida, Louisiana, and Texas.

g Michigan, NewYork. 888 Calvert et al.100,000 FTEs (2002), driven primarily by the occurrence of large California events (Fig. 1). Limiting the analysis to the five states (California, Florida, New York, Oregon, Texas) that provided data for all 8 years had little effect on the plot in the Figure 1. By US geographic region, the IR for agricultural workers was highest in the West. The rates in the West were largely driven by California and Washington State, where the rates were 100.8 and 113.0/100,000 FTEs, respectively. Information on age was available for 87% of the cases (N 1⁄4 2,857; Table I). The median age was 33 years (range TABLE III. Incidence Rates by Occupation for 3,271 Acute Pesticide Poisoning Cases in the Agricultural Industry, 1998^2005

Occupation Number Percent FTE estimatea Incidence rate b

FarmworkerEall 2,334 71 3,119,402 74.8

FarmworkerEmale 1,620 69 2,625,146 61.7 FarmworkerEfemale 701 30 494,256 141.8 Farmer 89 3 1,852,030 4.8

FarmerEmale 80 90 1,510,632 5.3 FarmerEfemale 9 10 341,398 2.6 Processing/packing plant worker 394 12 108,646 362.6

Processing/packing plant workerEmale 108 27 21,094 512.0 Processing/packing plant workerEfemale 279 71 87,552 318.7 All other agricultural occupations 454 14 1,018,205 44.6

All other agricultural occupationsEmale 381 84 674,521 56.5 All other agricultural occupationsEfemale 65 14 343,684 18.9
Total c 3,271 100 6,098,283 53.6

TotalEmale 2,189 67 4,831,393 45.3 TotalEfemale 1,054 32 1,266,890 83.2

aFTE, full-time equivalent.
b Incidence rates per100,000 FTEs. Includes agricultural workers in Arizona, California, Florida, Louisiana, Michigan, New Mexico, New York, Oregon,Texas, and Washington.

cSex was unknown for 28 cases (farmworkers 1⁄4 13, processing/packing plant worker 1⁄4 7, all other agricultural occupations 1⁄4 8).

FIGURE 1. Incidence rates for acute pesticide poisoning cases among agricultural and non-agricultural workers by year, age15^64 years,1998 ^2005. Pesticide Poisoning Among Agricultural Workers 88915–64), and over half of the cases were between the ages of 25 and 44 years (N 1⁄4 1,637, 57%). The IR was highest among agricultural workers age 18–24 years (76.2/100,000 FTEs; Table II). Because agricultural workers employed in the states and time periods covered in this study worked 2,173 hr per year on average, using FTEs in the denominator produced rates that were approximately 7% lower compared to when employment counts were used in the denominator. In contrast, because non-agricultural workers worked 1,935 hr per year on average, using FTEs in the denominator produced rates that were approximately 4% higher compared to when employment counts were used in the denominator. The overall average annual IR among agricultural workers using employment counts in the denominator was 57.6/100,000workers, and was 1.33/100,000 FTEs among all nonagricultural workers combined (IRR 1⁄4 43.2, 95% CI 41.4, 45.1).


### Occupations of the Affected Agricultural Workers

Most of the 3,271 affected agricultural workers were employed as farmworkers (N 1⁄4 2,334, 71%; Table III). The 394 affected processing/packing plant workers (12%) represented a disproportionately large share of people so employed, while farmers (N 1⁄4 89, 3%) seemed less at risk than hired agricultural workers. Most of the ‘‘other miscellaneous agricultural workers’’ were employed as pest control operators (N 1⁄4 255, 56%). Because CPS data for pest control operators were too sparse (e.g., in 1999 and 2001 no CPS data were available for this occupation), IRs were not calculated for this occupation. Gender was reported for all but 28 (1%) of the cases. Males predominated in each occupational category except processing/packing plant workers. Paradoxically, IRs were higher among female than male farmers and farmworkers, but higher among male than female processing/packing plant workers. Females were less likely than males to be pesticide handlers (females 1⁄4 8%, males 1⁄4 45%, P < 0.001). Information on race and ethnicity was available for 727 cases (22%).A total of 502 (69%) were Hispanic, 187 (26%) were nonHispanic white, 12 (2%) were black, and the remaining 26 (4%) recorded various other races.


### Severityand Description of Fatal Case

A vast majority of the illnesses were of low severity (2,848 cases, 87%), while 402 (12%) were of medium severity and 20 (0.6%) were high severity (Table I). One case was fatal. The fatal case occurred in 1999 and involved a 59- year-old Hispanic male who was employed as an irrigator and farmworker supervisor. He was found dead in an orange grove in California, with packages of hotdogs and packets of methomyl near his body. This led investigators to suspect he had violated regulations by opening water-soluble methomyl packets and using the potent carbamate insecticide to contaminate hot dogs for use as bait to kill coyotes. His autopsy found a small amount of methomyl in his gastric contents but none in his blood. His blood and bile also contained a relatively large concentration of benzothiazole, an industrial chemical and a metabolite of cyprodinil (a toxicity category III fungicide). The large concentration of benzothiazole was suggestive of chronic exposure, or heavy acute exposure at least 24 hr earlier. The medical examiner concluded that the cause of death was likely due to an interaction between the methomyl and cyprodinil. The source of the exposure to benzothiazole or cyprodinil was not known. Whether the exposures were accidental or intentional (i.e., suicidal) could not be distinguished.



### Signs and Symptoms

Table IV lists the signs and symptoms most often reported in this cohort. It also provides information on the health effects among those exposed to the four pesticide chemical classes most commonly involved in illness.



### Pesticides Responsible for Illness

Information on the pesticides responsible for illness is provided in Tables I, IV and V. Insecticides (alone or in combination with other pesticides) were implicated in more than half of the illnesses (N 1⁄4 1,761, 54%). Cholinesterase inhibitors (organophosphates and N -methyl carbamates) were prominent among the insecticides (N 1⁄4 892, 51%), particularly chlorpyrifos (N 1⁄4 190), methamidophos (N 1⁄4 130), dimethoate (N 1⁄4 84), malathion (N 1⁄4 78), and diazinon (N 1⁄4 70). Over half of the cases (N 1⁄4 1,662, 51%) were exposed to toxicity category I pesticides, the most toxic category as defined by EPA (Table I). We found little variation in illness severity by pesticide category.



### Activityat Time of Exposure

Information on activity at time of pesticide exposure was available for 3,203 (98%) of the affected workers. Of these, 33% (N 1⁄4 1,068) were pesticide handlers and 67% (N 1⁄4 2,135) were doing routine work not involved with a pesticide application. Most of the handlers (71%) were exposed while making applications. Among the 2,135 doing routine work, half were exposed to off-target drift of pesticide from a nearby application (N 1⁄4 1,068), and 35% (N 1⁄4 744) had contact with pesticide residues present on a treated surface (e.g., plant material or treated animal). Table I lists the targets to which pesticides were applied in incidents that resulted in human illness. Among the 890 Calvert et al.fruit crops, the most common application targets were small fruits (e.g., grapes; N 1⁄4 529, 46%), tree nuts (N 1⁄4 181, 16%), citrus fruits (N 1⁄4 175, 15%), and pome fruits (e.g., apples; N 1⁄4 151, 13%). Among the most common vegetable crop targets were root and tuber vegetables (e.g., onions and potatoes; N 1⁄4 185, 40%), leafy vegetables (N 1⁄4 180, 39%) and fruiting vegetables (e.g., eggplant, tomatoes, and peppers; N 1⁄4 48, 10%). Among grain, grass and fiber crops, the most common pesticide application targets were cotton (N 1⁄4 140, 54%), and cereal grains (N 1⁄4 61, 23%). 

### Factors That Contributed to Pesticide Exposure

We identified factors that contributed to pesticide exposure in 1,926 (59%) of the cases (Table VI). The most common factors identified were off-target drift (N 1⁄4 1,216, 63%), early reentry into a recently treated area (N 1⁄4 336, 17%), and use in conflict with the label (N 1⁄4 319, 17%). In 992 (30%) cases, no obvious contributory factors could be identified (e.g., restricted entry interval was observed but worker still became ill; wore all required PPE but still TABLE IV. Illness Characteristics by Pesticide Chemical Class for 3,271Acute Pesticide Poisoning Cases in the Agricultural Industry,1998^2005

Signs and symptoms Pesticide chemical classa,b

All a
, N 1⁄4 3,271 (%) Cholinesterase inhibitors, N 1⁄4 892 (%) Pyrethroids,
N 1⁄4 182 (%) Inorganics,
N 1⁄4  567 (%) Dithiocarbamates,
N 1⁄4 512 (%)
Nervous/sensory 1,743 (53) 672 (75) 120 (66) 241 (43) 237 (46)

Headache 1,268 (39) 499 (56) 94 (52) 164 (29) 185 (36) Dizziness 708 (22) 297 (33) 39 (21) 88 (16) 85 (17) Muscle weakness 243 (7) 126 (14) 10 (5) 29 (5) 23 (4) Blurred vision 204 (6) 86 (10) 8 (4) 34(6) 29(6) Paresthesias 198 (6) 76 (9) 15 (8) 31 (5) 25 (5) Muscle pain 98 (3) 44 (5) 7 (4) 7 (1) 15 (3) Diaphoresis 94 (3) 59 (7) 6 (3) 8(1) 7(1) Salivation 63 (2) 48 (5) 3 (2) 2 ( < 1) 19 (4) Fasciculation 47 (1) 32 (4) 3 (2) 3 (1) 3 (1) Confusion 46 (1) 19 (2) 1 (1) 3 (1) 2 ( < 1) Gastrointestinal 1,300 (40) 510 (57) 91 (50) 174 (31) 188 (37)

Nausea 1,063 (33) 438 (49) 74 (41) 131 (23) 152 (30) Vomiting 582 (18) 261 (29) 39 (21) 73 (13) 91 (18) Abdominal pain/cramping 371 (11) 161 (18) 15 (8) 34 (6) 75 (15) Diarrhea 148 (5) 80 (9) 8 (4) 8 (1) 17 (3) Ocular 1,300 (40) 272 (30) 54 (30) 243 (43) 297 (58)

Irritation/pain/inflammation 1,112 (34) 208 (23) 48 (26) 222 (39) 262 (51) Lacrimation 443 (14) 92 (10) 14 (8) 51 (9) 166 (32) Conjunctivitis 80 (2) 8 (1) 5 (3) 23 (4) 1 ( < 1) Dermatologic 1,077 (33) 235 (26) 57 (31) 191 (34) 96 (19)

Pruritis 580 (18) 106 (12) 26 (14) 125 (22) 50 (10) Rash 571 (17) 98 (11) 17 (9) 126 (22) 64 (13) Erythema 349 (11) 52 (6) 14 (8) 76 (13) 27 (5) Irritation/pain 321 (10) 81 (9) 34 (19) 48 (8) 23 (4) Respiratory 1,074 (33) 329 (37) 56 (31) 232 (41) 152 (30)

Upperrespiratory pain/irritation 645 (20) 183 (21) 35 (19) 142 (25) 103 (20) Dyspnea 408 (12) 115 (13) 19 (10) 91 (16) 60 (12) Cough 278 (9) 67 (8) 5 (3) 75 (13) 32 (6) Cardiovascular 211 (6) 77 (9) 7 (4) 43 (8) 31 (6)

Chest pain 131 (4) 45 (5) 4 (2) 32 (6) 18 (4) Tachycardia 33 (1) 17 (2) 1 (1) 2 ( < 1) 3 (1)

aMore than one sign/symptom may be reported by a case, and therefore the sum of the specific clinical effects may not equal the total number of system effects.
bCases may be exposed to more than one chemical class.Columns include cases exposed to the labeled chemical class only as well as those exposed to mixtures containing that and other chemical classes. Pesticide Poisoning Among Agricultural Workers 891TABLE V. Fifteen Most Common Active Ingredientsfor 3,271Acute Pesticide Poisoning Cases in the Agricultural Industry by Severity Category,1998^2005

Active ingredient Functional class (chemical class) High severity/ fatal Moderate severity Low severity N (%) a

Sulfur Insecticide and fungicide (inorganic) 2 45 421 468 (14) Metam-sodium Fumigant (dithiocarbamate) 1 5 279 285 (9) Glyphosate Herbicide (phosphonate) 3 25 223 251 (8) Mancozeb Fungicide (dithiocarbamate) 1 17 184 202 (6) Chlorpyrifos Insecticide (organophosphate/cholinesterase inhibitor) 0 33 157 190 (6) Sodium hypochlorite Disinfectant (halogen) 2 35 149 186 (6) Methamidophos Insecticide (organophosphate/cholinesterase inhibitor) 1 10 119 130 (4) Abamectin Insecticide (microbial) 0 18 108 126 (4) Imidacloprid Insecticide (neonicotinoid) 4 5 104 113 (3) Methomyl Insecticide ( N -methyl carbamate/cholinesterase inhibitor) 1 7 101 109 (3) Myclobutanil Fungicide (triazole) 1 11 97 109 (3) Propargite Insecticide (sulfite ester, inhibits oxidative phosphorylation) 0 21 77 98 (3) Spinosad Insecticide (derived from Saccharopolyspora spinosa ) 1 10 85 96 (3) Methyl bromide Fumigant (halocarbon) 2 29 60 91 (3) Dimethoate Insecticide (organophosphate/cholinesterase inhibitor) 4 6 74 84 (3)

aPercentages do not sum to100, as not all cases are included in this table.

TABLE VI. FactorsThat Contributed to Pesticide Exposure and/or Illness for 3,271Acute Pesticide Poisoning Cases in the Agricultural Industry by Severity Category,1998^2005

Exposure/illness factora Medium or higher severity, N (%) Low severity, N Total, N (%)
All factors combined 219 (11) 1,707 1,926 (59) Drift 118 (10) 1,098 1,216 (37) Early reentry 41 (12) 295 336 (10) Use in conflict with label 40 (13) 279 319 (10) Failure to userequired equipment 19 (12) 139 158 (5) Oral notification of pesticide application not provided 9 (6) 143 152 (5) PPE not worn 19 (16) 98 117 (4) Training not provided or inadequate (excludes applicators) 30 (29) c 75 105 (3) Hazard communication or other OSHAviolation 9 (9) 86 95 (3) Transport for care not provided 5 (6) 84 89 (3) Application site not posted/notification posters incorrect 3(4) 81 84 (3) Decontamination facilities inadequate 16 (26) c 46 62 (2) Unsafe equipment/failure 8 (14) 49 57 (2) Inadequaterecord keeping 7 (20) 28 35 (1) Worker not told of health effects caused by pesticides 0 (0) 32 32 (1) Person in treated area during application 2 (10) 19 21 (1) Unspecified worker protection standard violation 3 (15) 17 20 (1) PPE in poorrepair 3 (23) 10 13 ( < 1) FIFRA-other and unspecified b 6 (27)c 16 22 (1) None identified 126 (13) 866 992 (30) Unknown 78 (22) 275 353 (11)

aOne factor was identified for1,279 cases.Two or more factors were identified for 647 cases.
b Includes situations when a licensed applicator was not on site(N 1⁄4 1) and when an applicator was not properly trained or supervised (N 1⁄4 9).

c The proportion with medium or higher severity among cases with the factor of interest was significantly greater than the proportion with medium or hig her severity in all other cases ( P < 0.05).Those with insufficient information to identify factors (i.e., unknown category) were excluded from this analysis. 892 Calvert et al.became ill; all pesticide label requirements appeared to have been followed). Compared to cases where no obvious contributory factors could be identified, identification of acontributory factor was not found to be significantly associated with severity of illness (P 1⁄4 0.33). For 353 (11%) cases, insufficient information was available to identify factors that may have contributed to the pesticide exposure. Among the 2,367 cases with personal protection equipment (PPE) usage information, 1,157 (49%) wore PPE (Table VII). Women were far less likely to wear PPE (females 1⁄4 27%, males 1⁄4 40%, P < 0.01). Pesticide handlers were more likely to use PPE (65% overall, 66% among men and 51% among women) compared to non-handlers (21% overall, 18% among men and 26% among women). Those exposed to toxicity category II pesticides were more likely to wear PPE (61%) then those exposed to toxicity category I or III /IV pesticides (53% and 54%, respectively). Table VII also provides information on the health effects experienced by those who used each type of protective equipment. Compared to those who used no protective equipment or had unknown information on its use, those who used protective equipment were less likely to have health effects involving the nervous, gastrointestinal and respiratory systems, but were more likely to have ocular and dermatologic health effects.



### Report Source

Case reports were received from many different sources. The three leading sources of case reports were workers’ compensation (N 1⁄4 1,109, 34%), other government agencies (e.g., county health departments and the state department of agriculture; N 1⁄4 901, 28%), and poison control centers (N 1⁄4 407, 12%). A variety of sources accounted for the remaining cases including health care professionals, employers, worker representatives (union, legal services), and selfreport. The specific number of cases reported by these other sources is unavailable. Females were more likely to have been reported by one of these other sources (females 1⁄4 41%, males 1⁄4 23%, P < 0.01), and less likely to be identified by workers’ compensation (females 1⁄4 25%, males 1⁄4 39%,
P < 0.01) or poison control centers (females 1⁄4 8%, males 1⁄4 15%, P < 0.01). Females and males were equally likely to have been reported by other government agencies (28%).



### DISCUSSION

It is important to conduct surveillance of acute occupational pesticide poisoning to determine whether policies,practices and regulations are effective in preventing hazardous pesticide exposures. National estimates of hospitalized pesticide poisonings in the 1970s and early 1980s, including agricultural workers, are available [Keefe et al., 1985, 1990];but to the best of our knowledge this is the first detailed multistate assessment of both hospitalized and non-hospitalized acute pesticide poisoning among agricultural workers. Our findings indicate that despite strengthening of the WPS in 1995, agricultural workers continue to have an elevated risk for acute pesticide poisoning. The pesticide poisoning incidence among US agricultural workers was found to be 39 times higher than the IR found in all other industries combined.


### Improvement Compared to the 1980s

Although there was not a clear trend in the rates of poisoning during the time period that we studied, there is evidence to suggest that the counts of pesticide poisoning

TABLE VII. Illness Characteristics byType of Protective Equipment Used1998^2005

Type of protective equipment Number that used protective equipment Of workers who used protective equipment,the number (%) who had signs/symptoms involving these organs/systems

Nervous/sensory Gastro-intestinal Ocular Respiratory Dermatologic
Any PPE 1,157 557 (48) 404 (35) 472 (41) 301 (28) 437 (38) Air-purifyingrespirator 261 121 (46) 91 (35) 92 (35) 49 (19) 94 (36) Dustmask 40 16 (40) 12 (30) 19 (48) 18 (45) 15 (38) Chemical resistant gloves 700 306 (44) 208 (30) 293 (42) 150 (21) 254 (36) Chemical resistant clothing 542 230 (42) 177 (33) 214 (39) 105 (19) 213 (39) Chemical resistant boots 367 170 (46) 110 (30) 152 (41) 63 (17) 127 (35) Cloth/leather gloves 298 192 (64) 138 (46) 92 (31) 114 (38) 140 (47) Goggles/eye protection 488 193 (40) 126 (26) 198 (41) 80 (16) 196 (40) Engineering controlsa 100 48 (48) 34 (34) 23 (23) 20 (20) 41 (41)
No or unknown PPE use b 0 1,186 (56) 896 (42) 828 (39) 773 (37) 640 (30)

aEngineering controls included such things as enclosed tractor cabs or closed mixing/loading systems.
bA total of 2,114 individuals used no protective equipment or had unknown information on use of protective equipment. Pesticide Poisoning Among Agricultural Workers 893cases among agricultural workers have decreased since the 1980s. Mehler et al. [1992] reported an annual average of 723 cases of pesticide illness or injury in California arising from agricultural establishments from 1982 to 1990. In contrast, the California surveillance programs reported an average of 315 cases per year from 1998 to 2005. The numbers are not entirely comparable. Mehler characterized poisoning cases as being agricultural if the poisoned subject was a worker and the exposure arose from an agricultural establishment. Her definition included non-agricultural workers (e.g., truck drivers, construction workers, school employees), while we included only workers employed in agriculture.



### True Incidence Remains Uncertain: Comparison With Data From the Bureau of Labor Statistics, the National Agricultural Workers Survey, and the Agricultural Health Study

In order to put our findings in perspective, acute pesticide poisoning annually accounts for a small percentage of the total occupational illnesses experienced by agricultural workers. The 2005 Bureau of Labor Statistics (BLS) survey of illnesses and injuries (SOII), which excludes agricultural production establishments with 10 employees or fewer, reports an annual injury rate of 5.7% and an annual illness rate of 0.4% (3% of which involve poisonings) among workers in farming, forestry and fishing [Myers, 2007]. Mostof these illnesses consisted of dermatitis, respiratory conditions, and other conditions not specified (e.g., musculoskeletal conditions arising from cumulative trauma). We report a rate of pesticide poisoning five times higher than the SOII rate for all poisonings. This may indicate that pesticide poisonings are concentrated among the small establishments excluded from SOII, that under-reporting to SOII is more extreme thanSENSOR-pesticide under-ascertainment, or that SENSORpesticide classification standards accept a large number of cases that BLS does not count. Data from the National Agricultural Workers Survey (NAWS), by contrast, suggest an incidence of acute pesticide poisoning among agricultural workers [US Department of Labor, 2004] an order of magnitude greater than that found in this study. NAWS is a nationally representative annual survey of US crop workers conducted by the US Department of Labor. In 1999, NAWS included questions to determine if crop workers were poisoned by pesticides. This information was collected in two parts. First NAWS asked the crop worker if they were exposed to pesticides by ‘‘having them sprayed or blown on you,’’ ‘‘spilled on you,’’ or ‘‘when cleaning or repairing containers or equipment used for applying or storing pesticides.’’ NAWS then asked if the crop worker became ‘‘sick or [had] any reaction because of this incident.’’ Our analysis of these data found that 3.2% of crop workers acknowledged exposure during the previous 12 months, of whom 43.4% reported getting sick or having a reaction. That is, 1.4% of US crop workers attributed health effects such as skin problems (59%), eye problems (24%), nausea/vomiting (30%), headache (26%), and numbness/tingling (12%) to pesticide exposure during the preceding 12 months. In a separate NAWS question, 0.6% of all US crop workers reported that in the last 12 months they had ‘‘received medical attention by a doctor or nurse due to pesticide exposure.’’ To our knowledge, neither these nor similar questions to assess the incidence of pesticide poisoning were included in NAWS surveys before or after 1999. In comparison, we found an average annual acute occupational pesticide poisoning IR of 0.05% among all agricultural workers, and 0.07% among farmworkers. Acute pesticide poisoning IR were also assessed among farmers participating in the Agricultural Health Study (AHS), a prospective cohort study sponsored by the National Institutes of Health (i.e., the National Cancer Institute and the National Institute of Environmental Health Sciences) and EPA [AHS, 2007]. The AHS cohort consists of 52,395 farmers, 32,347 spouses of these farmers, and 4,916 commercial pesticide applicators residing in Iowa or North Carolina. In a nested case–control analysis involving 16,416 farmers/pesticide applicators who were interviewed by telephone in 1999–2000, 54 (0.33%) reported ‘‘an incident with fertilizers, weed killers, or other pesticides that caused an unusually high personal exposure’’ in the previous 12 months that resulted in physical symptoms [Bell et al., 2006]. Among these 54 individuals, only 7 (13%, or .04% of the entire subcohort) sought medical care. In contrast, we found an average annual acute occupational pesticide poisoning IR of 0.005% among farmers. However, as was observed in our study, the findings from AHS and NAWS suggest that the risk of pesticide poisoning is lower among farmers compared to farmworkers. The true incidence of pesticide poisoning among agricultural workers remains uncertain. Our findings (51/ 100,000) fall between the low SOII estimate (less than 10/ 100,000) and the high rates elicited by NAWS interviews (1,400/100,000 symptomatic, 600/100,000 sought medical care).



### Limitations

One of this study’s major limitations is that underreporting compromises, to varying degrees, all the surveillance systems that provided the data for this analysis. Factors that contribute to under-reporting include: affected people not seeking care, or consulting care providers outside the jurisdiction of surveillance programs; misdiagnosis of this uncommon condition; and health care provider neglect of legal requirements to report. The rates provided should be considered low estimates of the magnitude of acute pesticide poisoning among agricultural workers. 894 Calvert et al.Disproportionate numbers of agricultural workers probably are deterred from seeking health care by lack of health insurance [US Department of Labor, 2005], unfamiliarity with workers’ compensation benefits or inability to qualify for them, and fear of job loss if they miss time from work to seek health care [Das et al., 2001; Arcury and Quandt, 2007], as well as concerns related to immigration status. Similarly, a variety of interrelated problems may lead health care professionals to misdiagnose acute pesticide poisoning.Health professionals rarely receive much training in environmental toxicology generally or on pesticide poisoning specifically [Schenk et al., 1996]. Consequently, they may not collect a pesticide exposure history, which is necessary to make a diagnosis of acute pesticide poisoning [Balbus et al., 2006]. Pesticide poisoning is relatively rare in developed countries, and its signs and symptoms often resemble those ofmore common conditions, which may be diagnosed preferentially. The difficulty and delays of receiving reimbursement through workers’ compensation may also bias health careproviders against diagnosing and reporting pesticide poisoning. Even among those cases correctly diagnosed, some cases may escape report to public health authorities through ignorance of the requirement (despite the fact that 30 states have a mandatory reporting system of occupationally related pesticide poisoning [Calvert et al., 2001]) or because the health care professionals fear that their patients may be subject to retaliation. Other cases may go unreported because many farmworkers immigrate from Mexico [US Department of Labor, 2005], and some poisoned Mexican farmworkers may prefer to visit physicians in Mexico where cultural and linguistic barriers are removed and fees are lower [US EPA,1992; Arcury and Quandt, 2007]. Our state-based surveillance partners received only nine reports of pesticide poisoning cases managed outside the US. Another limitation in our study was that information was incomplete for some reported cases. Most cases lacked information on race and ethnicity. Missing information could lead to misclassification of severity, if not all signs and symptoms were reported, or to inappropriate exclusion of the case. More detailed information on the affected worker’s activities, pesticide exposures and health effects might have increased our case totals. Some cases in this report may befalse-positives, with compatible symptoms that are coincidental with but not caused by pesticide exposure. Finally, information on factors that contributed to illness was identified in only 1,926 (59%) cases. In many casesa timely and definitive investigation into the factors responsible for exposure and illness was not possible due to insufficient investigatory resources and/or because of tardy notification of the exposure to state authorities. Rates of pesticide poisoning may also be distorted by inaccuracy in estimates of population at risk. The size of the agricultural worker population, including farmworkers and processing/packing plant workers, is difficult to estimate for several reasons, including the transient employment of many seasonal and migrant farmworkers, migration into and out of the United States in a manner that is not entirely predictable, and the tendency of many farmworkers to avoid government contact [Rust, 1990]. Our agricultural worker population estimates were derived from the CPS, which is conducted by the BLS and the United States Census Bureau. The CPS goes to great lengths to capture reliable workforce data [Bureau of Labor Statistics, 2002]. Nevertheless, a population seeking to escape detection could well be under-counted, leading to inflated apparent rates of illness/injury. Finally, illness rates for those known to have occupational pesticide exposure are not available because the numbers or workers exposed to pesticides are unknown.


### Reasons for Higher Poisoning Rates in Western States

Rates of both agricultural and non-agricultural acute pesticide poisoning are higher in the western states as compared to the south and eastern regions of the United States. It is credible that labor-intensive Western agriculture may impose excess risk for acute pesticide poisoning illness, but it is also important to note that California (especially the CDPR program) and Washington have well established,longstanding and experienced state-based surveillance programs with higher staffing levels compared to other states participating in the SENSOR-Pesticides program [Calvert et al., 2004]. In addition, these states were much more likely to be notified about cases through the state workers’ compensation system (in Washington State 76% of the cases were so identified; in California 34% of reports wereprovided by physicians to a workers’ compensation insurance carrier). In contrast, only two other states identified cases through their state workers’ compensation system: Oregon and Texas (7% and 4%, respectively, of cases in these states were so identified).


### Higher Poisoning Rates Among Female Agricultural Workers

Female agricultural workers experienced nearly twice the risk of pesticide poisoning of male agricultural workers (Table III), a finding that was quite unexpected. Before indulging in speculation about possible differences in susceptibility, risk of exposure, or rate of ascertainment, we plan to perform more detailed analyses by geographic region, activity at time of exposure, pesticide, protective equipment, and severity.


### Higher Poisoning Rates Among Processing/Packing Plant Workers

Processing/packing plant workers were found to have the highest acute pesticide poisoning IR compared to all other Pesticide Poisoning Among Agricultural Workers 895agricultural occupations. Many farms are increasing the amount of food processing that is performed on site [National Research Council and Institute of Medicine, 2008]. This is due to a variety of factors, including the advent of new technology, quest for improved quality control and freshness, and a desire to increase profit. The types of food processing activities performed on farms include cleaning, sorting, packing, and cooling/freezing. Among the 394 poisoned processing/packing plant workers, the pesticides most commonly responsible for illness were fumigants (N 1⁄4 151, 38%), disinfectants (N 1⁄4 151, 38%), and insecticides (N 1⁄4 73, 19%). The fumigant exposures were commonly related to drift from a nearby field (N 1⁄4 111), the disinfectant exposures where commonly related to malfunction of disinfecting equipment (N 1⁄4 74) and cleaning produce in disinfectant solutions (N 1⁄4 31) and the insecticide exposures were commonly related to pesticide residue present on the produce (N 1⁄4 37). Because the WPS only covers workers involved in the production of agricultural plants, processing/ packing plant workers may not covered by WPS.



### Chronic Health Effects Associated With Acute Pesticide Poisoning

In addition to acute morbidity with it attendant costs in health care resources, and time lost from work and normal daily activities, acute pesticide poisoning is also associatedwith chronic adverse health sequelae. For example organophosphate poisoning has been found to be associated with deficits in neurobehavioral and neurosensory function [Steenland et al., 1994]. In addition, the Agricultural Health Study found that those who sought medical care for pesticide poisoning or who experienced an incident involving ‘‘unusually high’’ pesticide exposure had an increased risk for chronic neurologic symptoms (Kamel et al. 2005). These ‘‘unusually high’’ pesticide exposures, which are labeled by the authors as high pesticide exposure events (HPEE), result in acute symptomatic illness about 50% of the time [Bell et al., 2006]. Those who ever experienced an HPEE also had an increased risk for farmers lung (Hoppin et al. 2006). A non-significant elevated risk for prostate cancer was observed among those who had ever experienced an HPEE (odds ratio 1⁄4 1.11, 95% CI 1⁄4 0.8, 1.6) [Alavanja et al., 2003]. To our knowledge, the AHS has not published findings on any other associations between HPEE and cancer.



### Recommendations

The most common factors that contributed to pesticide exposure included off-target drift, early reentry into a treated area, and use in conflict with the pesticide label. These findings and the observations of other investigators [Arcury et al., 2001] suggest that improved compliance with and enforcement of existing pesticide regulations could achieve important improvements in safety. Measures to minimize drift (including equipment specifications, establishment of buffer zones, and limitations on maximum wind speed conditions during an application) seem likely to provide the greatest benefit. Our finding that 992 (30%) cases had no obvious factors contributing to exposure suggests that pesticide regulations and label requirements may also need to be enhanced. Additionally, reduced-risk pest control measures such as integrated pest management should be adopted, which can achieve reductions in pesticide exposure and misuse [National Research Council, 2000]. The high poisoning rates observed among processing/packing plant workers and the increased amount of food processing performed on farms suggests that processing/packing plant workers should be covered under the WPS.Given the limitations in this analysis, improved statebased surveillance programs for pesticide-related illness are also needed. A comprehensive system needs to address the limitations described above including: agricultural workersand health care providers need to recognize the pesticiderelatedness of the illness; disincentives to receiving health care, including lack of health insurance, must be overcome; the costs of evaluation and treatment of acute occupationalpesticide poisoning should be paid for by workers’ compensation; health care providers need to make timely reports to pesticide poisoning surveillance systems; and, surveillance systems need to optimize access to and use of workers’ compensation data, poison control center data and data from other state agencies with jurisdiction over pesticides.



### CONCLUSION

Agricultural workers are at increased risk of acutepesticide poisoning in comparison to non-agricultural workers, particularly through drift, early reentry into a treated area, and use in conflict with the label. The IR was almost twofold higher in female agricultural workers compared to males. In addition to acute intoxication, pesticide poisoning may also lead to chronic adverse health sequelae. Improved compliance with and stringent enforcement of laws and regulations regarding pesticide applications are needed. Alternative pest control measures such as integrated pest management reduce the use of pesticides and therefore the potential for adverse health effects.



### ACKNOWLEDGMENTS

Funding to support this study was provided by NIOSH, EPA, and the state agencies that contributed data.



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