Research Farmworkers Pneumoconiosis from Agricultural Dust Exposure among Young California Marc B. Schenker,1 Kent E. Pinkerton,2 Diane Mitchell,1 Val Vallyathan,3 Brenda Elvine-Kreis,1 and Francis H.Y. Green 4 1Department of Public Health Sciences, and 2Center for Health and the Environment University of California at Davis, Davis, California, USA; 3Pathology and Physiology Research Branch, National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA; 4Department of Pathology and Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada Background inorganic (mineral) dusts. : Agricultural workers are exposed to airborne pollutants, including organic and o Bjectivs : Lung autopsy specimens from consecutive coroner’s cases of Hispanic males in Fresno County, California, (n = 112) were obtained to determine whether mineral dust exposure in agricul- tural work leads to pneumoconiosis. Methods : The left lung was fixed by inflation. We evaluated airway and parenchymal pathology using standardized diagnostic criteria and semiquantitative grading schemata, including the grading of small airways for fibrosis and birefringent mineral dust particles. We analyzed lung dust burden on a subset of 37 lungs following bleach digestion, using scanning electron microscopy (SEM), X-ray spectrometry (XRS) and image analysis, and by X-ray diffraction for crystalline silica (CSi). Farmworkers comprised 51.5% and nonfarmworkers 48.5% of the samples. words r esult : Proximal airways demonstrated little mineral dust accumulation, but membranous and respiratory bronchioles had wall thickening, remodeling, and inflammation associated with carbo- naceous and mineral dust deposition. These changes were independently associated with agricultural work, cigarette smoking, and increased age. Mineral dust small airways disease, pneumoconiosis (macules and nodules), and pathologic changes consistent with chronic bronchitis, emphysema, and interstitial fibrosis predominated in farmworkers compared with nonfarmworkers. CSi, determined gravimetrically, and aluminum silicate particles, determined by SEM/XRS, were increased in the lungs of farmworkers compared with nonfarmworkers and were significantly (p < 0.05) associated with small airway disease and pneumoconiosis. c onclusi : Mineral dust exposure is associated with increased small airway disease and pneu- moconiosis among California farmworkers; however, the clinical significance and natural history of these changes remains to be determined. k ey : agriculture, dust, farmworker, interstitial fibrosis, pneumoconiosis, respiratory, small airways disease. Environ Health Perspect 117:988–994 (2009). doi:10.1289/ehp.0800144 available via http://dx.doi.org/ [Online 25 February 2009] Approximately 5 million workers in the United States work in the agricultural industry with potential exposure to a wide variety of respiratory toxicants. Among the various respiratory hazards not well studied is obstructive and restrictive lung disease caused by inorganic minerals (American Thoracic Society 1998). California agricultural work- ers have increased respiratory symptoms, decreased respiratory function, and increased mortality rates from chronic pulmonary disease compared with the general popula- tion (Schenker et al. 2005; Singleton and Beaumont 1989; Stubbs et al. 1984). The agricultural environment of the Central Valley of California places individuals at increased risk of exposure to inorganic par- ticles. This region encompasses a rich farming area as well as extensive urban development. The predominantly dry farming techniques of the Central Valley result in high levels of air- borne dust from operations such as field prep- aration and harvesting of row crops and tree fruits (Nieuwenhuijsen and Schenker 1998; Nieuwenhuijsen et al. 1998). Although soil consists of a mixture of organic and inorganic 988 materials, potential health effects from the ever-present mineral dusts have been largely overlooked. In theory, soil should contain representative portions of all major mineral classes in the earth’s crust; in reality, most agricultural soils are composed largely of sili- cate materials (e.g., feldspars, mica, clay min- erals) and crystalline silica (CSi) (quartz) with varying amounts of other mineral classes, depending on the local geologic history. The evidence that mineral dust exposure poses a significant hazard to agricultural workers for interstitial lung disease is based on a handful of case reports, inferences from exposures to mineral dusts in other industries, studies of wild and farm animals exposed to environ- mental dusts, and toxicologic studies (Gylseth et al. 1984; Schenker 2000; Schoning 1996; Vallyathan et al. 2007). The deposition and clearance of particles within the respiratory system occurs in an inhomogeneous manner. The fate of parti- cles is not well established, and there is little information on the distribution and reten- tion of particles under conditions of ambi- ent exposure. One purpose of this study was to design and implement an approach that would allow the assessment of particle reten- tion as well as histologic analysis of response in different lung compartments. Our findings in this regard have been previously published and show that the deposition of particles is primarily in the centriacinar portion of the lung lobule (Pinkerton et al. 2000). Unfortunately, no reported epidemiologic studies have directly assessed environmental exposure to mineral dusts and interstitial lung and airway disease in farmers or farmworkers, although respiratory symptoms have been associated with exposure to agricultural dusts with high mineral content (Schenker et al. 2005). A few studies, however, have suggested that pneumoconiosis (Gylseth et al. 1984; Sherwin et al. 1979) and restrictive lung disease (Sasagawa et al. 1989) are increased in some agricultural populations exposed to mineral dusts. A fundamental question remains whether occupational exposure to agricultural dusts can cause pulmonary fibro- sis, persistent inflammation, and cell/tissue remodeling in specific regions of the lungs where these mineral dusts are present. The objective of this study was to docu- ment and quantify pathologic lesions in lung tissues from consecutive Hispanic males autopsied by the coroner’s office in Fresno, California, and to determine their relation- ship to agricultural work and to mineral dust retained in the lungs. We focused on pneu- moconiosis and lesions of the small airways. The latter are the primary target of mineral dusts (Churg et al. 1999; Craighead et al. 1982) and are most likely to reflect early dis- ease in a young population (Pinkerton et al. Address correspondence to M. Schenker, Department of Public Health Sciences, University of California, One Shields Ave., Davis, California 95616 USA. Telephone: (530) 752-5676. Fax: (530) 752-3239. E-mail: mbschenker@ucdavis.edu Supplemental Material is available online at http:// www.ehponline.org/members/2009/0800144/suppl.pdf We thank S. Smiley-Jewell for assisting with manu- script preparation. This research has been funded in part by National Institute for Occupational Safety and Health U07/ CCU906162, U.S. Environmental Protection Agency grants R826246 and RD832414, and the Alberta Lung Association. The authors declare they have no competing Received 2 September 2008; accepted 25 February financial interests. 2009. ovlume 117 | number 6 | June 2009 • Environmental Health Perspectives