Journal of Exposure Science and Environmental Epidemiology (2012) 22, 584 -- 592 & 2012 Nature America, Inc. All rights reserved 1559-0631/12 www.nature.com/jes ORIGINAL ARTICLE Lifetime organophosphorous insecticide use among private pesticide applicators in the Agricultural Health Study Jane A. Hoppin1, Stuart Long2, David M. Umbach3, Jay H. Lubin4, Sarah E. Starks5, Fred Gerr5, Kent Thomas6, Cynthia J. Hines7, Scott Weichenthal8, Freya Kamel1, Stella Koutros9, Michael Alavanja9, Laura E. Beane Freeman9 and Dale P. Sandler1 Organophosphorous insecticides (OPs) are the most commonly used insecticides in US agriculture, but little information is available regarding specific OP use by individual farmers. We describe OP use for licensed private pesticide applicators from Iowa and North Carolina in the Agricultural Health Study (AHS) using lifetime pesticide use data from 701 randomly selected male participants collected at three time periods. Of 27 OPs studied, 20 were used by 41%. Overall, 95% had ever applied at least one OP. The median number of different OPs used was 4 (maximum ¼ 13). Malathion was the most commonly used OP (74%) followed by chlorpyrifos (54%). OP use declined over time. At the first interview (1993--1997), 68% of participants had applied OPs in the past year; by the last interview (2005--2007), only 42% had. Similarly, median annual application days of OPs declined from 13.5 to 6 days. Although OP use was common, the specific OPs used varied by state, time period, and individual. Much of the variability in OP use was associated with the choice of OP, rather than the frequency or duration of application. Information on farmers’ OP use enhances our ability to characterize and understand the potential health effects of multiple OP exposures. Journal of Exposure Science and Environmental Epidemiology (2012) 22, 584--592; doi:10.1038/jes.2012.79; published online 1 August 2012 Keywords: pesticide use; farming; organophosphorous insecticide INTRODUCTION OPs represent a large class of insecticides. They are often In 2007, 93 million pounds of insecticides were used in the United evaluated together based on their ability to inhibit acetylcholi- 5 States with 70% used in agriculture.1 Over a third of these were nesterase (AChE). This mechanism may not be related to all 6--8 organophosphorous insecticides (OPs), a class of insecticides health outcomes, nor do all OPs have the same capacity to 9 introduced in the 1950s. Although their use has declined over inhibit AChE. The biomarkers most frequently used to assess time, OPs are still among the most commonly used insecticides exposure to OPs (e.g., dialkylphosphates or AChE inhibition) are in the United States.1 Although national and regional data non-specific and thus have limited ability to assign exposure to a 10 are available on pesticide application and sales,1--3 only limited specific chemical. As OPs differ in their toxicities and potential to information is available regarding use of specific pesticides by affect human health, it is critical to understand how use of specific individuals, particularly how many pesticides of a given class an OPs differs among individuals. To characterize OP usage by US individual uses in a year or lifetime. Information on pesticide use farmers, we used data from a random sample of private pesticide patterns in the United States is limited to national surveys of applicators in the Agricultural Health Study (AHS), a prospective pesticide applicators, state-specific data about use on specific cohort study of licensed pesticide applicators in Iowa (IA) and 11 commodity crops, and sales figures.1--3 These surveys provide North Carolina (NC). Using data collected at three time points information about the relative ranking of specific pesticides used during 1993--2007, we describe among a well-characterized group in the United States, either by pounds of active ingredients applied of farmers: (1) the frequency of use of specific OPs, (2) the number or dollars spent on specific pesticides.1 For commodity crops, of different OPs used, (3) the number of days spent applying OPs, information is also available regarding the pesticides used on each and (4) temporal changes in use by this group. crop by state and calendar year.2,3 Since 1990, CA has collected information on agricultural use of pesticides, including the amount of active ingredient and the location where the pesticide was METHODS applied.4 All these sources are helpful in identifying the key Population pesticides used, but none provides information regarding the Pesticide applicators enrolled between 1993--1997 (Phase 1) when they frequency of use for an individual applying these pesticides. Of were receiving or renewing their pesticide licenses.11 A total of 82% of eligible particular interest for health research is understanding how private applicators (mainly farmers) enrolled. In Phase 1, all pesticide pesticides in a given class are used by individuals. applicators completed the AHS enrollment questionnaire and B44% also 1Epidemiology Branch, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA; 2Westat, Durham, North Carolina, USA; 3Biostatistics Branch, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA; 4Biostatistics Branch, NCI, NIH, DHHS, Rockville, Maryland, USA; 5College of Public Health, University of IA, Iowa City, Iowa, USA; 6EPA, Human Exposure and Atmosphere Science Division, Research Triangle Park, North Carolina, USA; 7Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA; 8Health Canada, Ottawa, Ontario, Canada and 9OEEB, DCEG, NCI, Rockville, Maryland, USA. Correspondence: Dr. Jane A. Hoppin, Epidemiology Branch, NIEHS, NIH, DHHS, MD A3-05, PO Box 12233, Research Triangle Park, NC 27709-2233, USA. Tel.: þ 1919 541 7622. Fax: þ 1919 541 2511. E-mail: [email protected] Received 17 February 2012; accepted 16 May 2012; published online 1 August 2012 Organophosphorous use among farmers Hoppin et al 585 completed the take-home questionnaire.11 Approximately 5 and 10 years included the top 34%. In NC, we selected a larger fraction because the after enrollment (Phase 2: 1999--2003; Phase 3: 2005--2010), all AHS number of NC participants is smaller and they are more geographically participants were asked to complete telephone interviews to update their dispersed. We randomly sampled equal numbers from all eligible pesticide use history. This analysis focuses on a subset of applicators who individuals in each of the four state-by-exposure strata and identified completed their Phase 3 interview by 2007. empirical sampling weights (i.e., number of subjects participating/number of We assessed lifetime use of OPs among 701 AHS private pesticide subjects eligible) to estimate pesticide use histories for the AHS participants applicators recruited for participation in a neurological testing study.12 The (N ¼ 3863) who met the eligibility requirements for the neurological study. OP exposure histories of these individuals were enhanced to include data The overall response rate was B39%. not currently available in the main AHS data set, specifically frequency and duration of use for pesticides on the take-home checklist and resolution of unknown insecticides from the follow-up interviews Pesticide Use History (see below for more information on exposure assessment). Private Information on pesticide use was collected in the AHS during three time pesticide applicators who completed all questionnaires at all three phases periods: Phase 1 (1993--1997), Phase 2 (1999--2003), and Phase 3 (2005-- were eligible. Participants were selected based on their lifetime days of use 2007 for this subset). Individuals were asked about their personal appli- of 10 OPs at Phase 1.12 This selection variable was the sum of the lifetime cation of pesticides for crop, animal, and non-crop uses. Phase 1 consisted days of use of each of the 10 OPs for which detailed information was of two self-administered questionnaires, the enrollment and the take- collected at enrollment. As the neurological study required traveling to a home questionnaire. Both Phase 1 questionnaires collected information fixed site for testing, only applicators living within 150 miles of Iowa City, regarding frequency and duration of use of selected pesticides in a closed IA; Dubuque, IA; Greenville, NC; or Wilmington, NC, were eligible.12 Women format, such that all individuals provided responses on pre-determined were excluded from the sample because of their low representation (o3%) OPs. At Phase 1, participants provided detailed information on 10 specific among the AHS applicators. We created two strata within each state --- a OPs (Table 1) including ever use, days used per year, years used, and use in high exposure group and the remainder of the population --- based on the past year. The take-home questionnaire also included a checklist that lifetime OP days of use, and we oversampled those in the high-exposure collected ever-use information on 12 additional OPs. The pesticide-related stratum in each state. In IA, the high-exposure stratum included the top questions on the Phases 2 and 3 telephone interviews had an open-ended 20% of the distribution of lifetime days; in NC, the high-exposure stratum format and obtained information on recent use of pesticides including Table 1. OP information collected in the Agricultural Health Study (1993--2007) and OP subgroup classification. Data collection periods Chemical name Year introduced