Low-to-Moderate Arsenic Exposure and Respiratory Health in American Indian Communities

Abstract

RATIONALE: Exposure to inorganic arsenic, through drinking naturally-contaminated water, is an established cause of lung cancer. Evidence on the impact of arsenic exposure on lung function, however, is less conclusive. The evidence available, mostly from populations exposed to water arsenic levels >100 μg/L, suggests that arsenic exposure is associated with lower lung function. Prospective studies and studies examining low-to-moderate levels of water arsenic exposure (<50 μg/L) the level relevant for U.S. populations, are very limited. OBJECTIVES: We evaluated the association between chronic low-to-moderate arsenic exposure with lung function and disease in an American Indian population. METHODS: The Strong Heart Study is a multicenter prospective study of cardiovascular disease and its risk factors among American Indian adults. The present analysis, in 2,166 adults, used urinary arsenic measurements at baseline (1989-1991) and lung symptoms and function assessment by standardized spirometry at the second examination (1993-1995). We evaluated associations between arsenic exposure and airflow obstruction, defined as ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) of less than 0.70, and restrictive pattern, defined as FEV1/FVC ratio greater than 0.70 and FVC less than 80% predicted; respiratory symptoms; and self-reported physician diagnosis of nonmalignant respiratory disease. RESULTS: The prevalence of airflow obstruction between 1993 and 1995 was 21.4% (463/2,166); restrictive pattern was 14.5% (314/2,166). Median urinary arsenic concentrations were higher in participants with airflow obstruction (11.0 μg/g creatinine) compared to those without obstruction (9.8 μg/g creatinine), and higher in those with restrictive pattern (12.0 μg/g) compared to those without restrictive pattern (9.4 μg/g). The odds ratio (95% confidence interval) for obstructive and restrictive patterns comparing the 75th to 25th percentile of arsenic was 1.13 (0.96-1.32) and 1.27 (1.01-1.60), respectively, after adjustment for age, sex, education, study site, smoking status, smoking pack-year, estimated glomerular filtration rate, tuberculosis, and body mass index. Emphysema, cough 4-6 times a day, phlegm, and stopping for breath were also positively associated with arsenic. CONCLUSIONS: In this American Indian population, exposure to low-to-moderate levels of inorganic arsenic, as measured in urine, was positively associated with restrictive pattern as measured by spirometry, self-reported emphysema diagnosis, self-reported shortness of breath, and more frequent cough and phlegm among those with cough, independent of smoking status. These findings suggest that low-to-moderate arsenic exposure can contribute to nonmalignant lung disease, and may be associated with restrictive lung disease.