Residential proximity to animal feeding operations and mortality among postmenopausal women in the Iowa Women’s Health Study

Abstract

BACKGROUND AND AIM: Industrialized animal feeding operations (AFOs) are sources of numerous pollutants (e.g., particulates, pathogens, nitrate). Evidence links residential proximity to AFOs to respiratory diseases and cancer incidence, but directions of associations are inconsistent, and no studies have investigated associations with mortality. We examined these relationships in a population-based cohort of postmenopausal women. METHODS: We linked enrollment (1986) addresses of 25,285 Iowa Women’s Health Study participants with street-level geocodes to a statewide database of permitted AFOs that included animal counts standardized by animal size and manure production (animal units; AUs). Underlying causes of death (n=15,330) were identified through 2014, including 3,468 cancer, 4,038 cardiovascular, and 1,638 respiratory (n=911 chronic obstructive pulmonary disease (COPD)) deaths. Cox models estimated hazard ratios (HR) and 95% confidence intervals (CIs) for quartiles or tertiles (based on the number of cases for each outcome) of total inverse distance-weighted AUs within 5km, after adjusting for demographics, residence type/size, smoking pack-years, and occupation. RESULTS:Sixty-three percent of women had ≥1 AFO within 5km of their residence. Participants in the highest exposure quartile had non-significantly elevated risks for death from any cancer (HR Q4.vs.none=1.07, 95%CI 0.96-1.19, p-trend=0.13). Risk of death from non-Hodgkin lymphoma was non-significantly elevated (HR T3 vs.none=1.35, 95%CI 0.93-1.94, p-trend=0.15). Participants in the highest quartile had decreased risk of mortality from respiratory disease (HR Q4.vs.none=0.84, 95%CI 0.71-0.99, p-trend=0.03); this persisted in the subset of COPD deaths (HR T3.vs.none=0.83, 95%CI 0.70-0.99, p-trend=0.05). The highest AU tertile was non-significantly associated with elevated risks of cardiovascular mortality (HR T3.vs.none=1.06, 95%CI 0.98-1.15, p-trend=0.13). No associations were observed for other cancers or other non-cancer causes of death. CONCLUSIONS:Our novel analysis suggests that higher exposure to animals from AFOs may increase risk of mortality from cancer and cardiovascular diseases. Consistent with limited agricultural/occupational studies, higher AFO exposures were associated with decreased mortality from respiratory diseases, including COPD. KEYWORDS: Mortality, Environmental epidemiology, Female, Respiratory outcomes