Inorganic arsenic, an established toxicant, has been associated with numerous health outcomes, including cancer of the lung. Evidence on the impact of arsenic exposure on nonmalignant respiratory outcomes, however, is less conclusive as studies examining low-moderate levels (<50 µg/L) of water arsenic exposure are limited. In the US, elevated arsenic disproportionately affects populations relying on private well water, including many American Indian communities. Additionally, these American Indian communities have historically been at an increased risk of tuberculosis. This dissertation aimed to better understand the relationships between arsenic exposure and nonmalignant respiratory health outcomes in a population exposed to low-moderate arsenic from drinking water. We used data from the Strong Heart Study (SHS), a prospective cohort of American Indian adults, and the Strong Heart Water Study (SHWS), a randomized controlled trial aiming to reduce arsenic exposure in American Indian communities.
First, we conducted an analysis in 2,132 SHS participants to evaluate associations of arsenic exposure with lung health using urinary arsenic measurements at baseline (1989-1991) and spirometric measurements at Visit 2 (1993-1995). Arsenic exposure was positively associated with restrictive pattern, airflow obstruction, lower lung function, self-reported emphysema and having to stop for breath, independent of smoking and other lung disease risk factors.
Second, we evaluated the relationship between a history of active tuberculosis and subsequent lung function in 2,463 SHS participants. We observed that a history of active tuberculosis was associated with airflow obstruction, restrictive pattern, and respiratory symptoms. We found a reduced odds of tuberculosis with increasing arsenic exposure, contrary to our hypothesis, but suggestive evidence of a possible synergistic interaction between arsenic and tuberculosis on worse lung function.
Third, we conducted a pilot study, in preparation for the SHWS, of 371 households to identify households with arsenic ≥10 µg/L. Arsenic ≥10 µg/L was found in 26.1% of households and median water arsenic concentration was 6.3 µg/L, ranging from <1 to 198 µg/L. The study also tested and confirmed the effectiveness of a water filtration device to reduce water arsenic in these communities. The long-term efficacy of a community-based arsenic mitigation program in reducing arsenic exposure and preventing arsenic related disease is being tested as part of the SHWS.
In conclusion, low-moderate arsenic exposure may contribute to nonmalignant respiratory outcomes, including reduced lung function, respiratory symptoms, and a restrictive lung disease pattern. Our findings support existing knowledge that tuberculosis is a risk factor for long-term respiratory impairment. There is a relatively high burden of arsenic exposure in communities where the SHWS is being conducted, pointing to the continued need for effective interventions at the household level. More research is needed to investigate the association between arsenic exposure and non-malignant respiratory health, as many populations at risk of developing tuberculosis and other respiratory infections are also exposed to arsenic-contaminated water
