Residential proximity to animal feeding operations and risk of lymphohematopoietic cancers in the Iowa Women’s Health Study

Abstract

BACKGROUND AND AIM: Animal feeding operations (AFOs) are important sources of hazardous emissions into the surrounding environment. Residential proximity to farm animals has been linked to the risk of lymphohematopoietic malignancies in farming populations; we evaluated this relationship for the first time in the general population residing in agricultural areas. METHODS: We linked enrollment (1986) addresses of 28,196 participants in the Iowa Women’s Health Study, a population-based cohort of postmenopausal women, to a statewide database of permitted AFOs that included animal counts standardized by animal size and manure production (animal units [AUs]). We computed inverse distance-weighted total and animal type-specific AUs within 5km of residences, weighted by the time over a 10-year period (1986-1996) the participant resided downwind from each AFO. We estimated the risk of incident lympho- and hematopoietic malignancies and non-Hodgkin lymphoma (NHL) subtypes (hazard ratio [HR]; 95% confidence interval [CI]) for AU quartiles compared to those with no AUs within 5km, adjusting for demographic and lifestyle factors. RESULTS:Through 2014, there were 663 and 262 cases of NHL and leukemia, respectively. We observed increased risk of NHL and some subtypes; however, associations were inconsistently positive and lacked monotonic trend. NHL risk was increased for the second quartile of total AUs within 5km (HRQ2.vs0=1.25; CI:1.00-1.56) but not for the other quartiles (HRQ1.vs0=1.06; HRQ3.vs0=1.00; HRQ4.vs0=1.02; ptrend=0.71). This association appeared to be driven by cattle AUs (HRQ2.vs0=1.29; CI:1.01-1.65, ptrend=0.71). We also found positive and significant associations with specific quartiles of cattle exposures for follicular lymphoma (HRQ2.vs.0=1.95; CI:1.04-3.66; ptrend=0.59) and diffuse large B-cell lymphoma (HRQ1.vs.0=1.66; CI:1.04-2.66; ptrend=0.76). There were no associations for other animal types, other NHL subtypes, or leukemia. CONCLUSIONS:In this first investigation in a population-based cohort, our findings of modest increases in NHL risk associated with animal agriculture near the home are consistent with limited prior studies in farming populations. KEYWORDS: Cancer and cancer precursors, Environmental Epidemiology, Female