Pneumoconiosis from agricultural dust exposure among young California farmworkers.
BACKGROUND
Agricultural workers are exposed to airborne pollutants, including organic and inorganic (mineral) dusts.


OBJECTIVE
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 agricultural 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.


RESULTS
Proximal airways demonstrated little mineral dust accumulation, but membranous and respiratory bronchioles had wall thickening, remodeling, and inflammation associated with carbonaceous 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.


CONCLUSIONS
Mineral dust exposure is associated with increased small airway disease and pneumoconiosis among California farmworkers; however, the clinical significance and natural history of these changes remains to be determined.
Schenker
Marc B
MB
Department of Public Health Sciences, University of California at Davis, Davis, California 95616, USA. mbschenker@ucdavis.edu
Pinkerton
Kent E
KE
Mitchell
Diane
D
Vallyathan
Val
V
Elvine-Kreis
Brenda
B
Green
Francis H Y
FH
D000293:Adolescent; D000328:Adult; D000368:Aged; D000382:Agricultural Workers' Diseases / Q000139:chemically induced / Q000473:pathology; D000383:Agriculture; D000395:Air Pollutants, Occupational / Q000633:toxicity*; D002140:California; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D016273:Occupational Exposure; D052638:Particulate Matter / Q000633:toxicity*; D011009:Pneumoconiosis / Q000209:etiology* / Q000473:pathology; D012137:Respiratory System / Q000187:drug effects*; D014481:United States; D014961:X-Ray Diffraction; D055815:Young Adult
D000395:Air Pollutants, Occupational; D052638:Particulate Matter