Thyroid cancer incidence in women and proximity to industrial air pollution sources: A spatial analysis in a middle size city in Colombia

Özet

Manizales, a mid-size city in Colombia, hosts industries like metallurgy, electrical, chemical, and rubber andplastic industrial facilities that have released into atmosphere some pollutants postulated as thyroid cancer (TC)promoters, such as dioxins and furans, dichloromethane, lead and copper. In this article we aim to detect clustersof TC and analyze their spatial association with industrial pollution. TC cases (2003–2010) were obtained fromManizales' Population-based Cancer Registry (PCR-Mz). Atmospheric emissions from industries were obtainedfrom official reports of environmental authority. Data was spatially aggregated into census tracts and analyzedwith Bayesian Besag-York and Mollié (BYM) models. Three exposure approaches were used: i) presence or absenceof industries into census tracts, ii) sum of air discharges, and iii) an exposure index (EI) that considered thedistance and orientation of the census tract regard to industries, average wind direction and speed, and populationmobility. Models were fitted by exposure definition and sex, and included traffic and socioeconomicvariables for adjustment. Using the Kulldorff's spatial exploration statistic we also performed point-data analysesin order to detect and localize clusters with individual data.Ecological regression models showed that, for women, smoothed standardized incidence ratio (sSIR) increasein 15% [95% credibility interval: 3–27%] and 63% [95%CI: 18–125%] per one standard deviation increase in EIfor dichloromethane and PCDDs/Fs, respectively. Point-data analysis confirmed a cluster of female cases close toan industry emitting chlorinated solvents. These results suggest that dichloromethane and PCDDs/Fs emittedfrom industrial sources might be suspected as thyroid cancer risk factors.