Cancer mortality and oil production in the Amazon Region of Ecuador, 1990–2005

Abstract

To compare cancer mortality rates in Amazon cantons (counties) with and without long-term oil exploration and extraction activities. Mortality (1990 through 2005) and population census (1990 and 2001) data for cantons in the provinces of the northern Amazon Region (Napo, Orellana, Sucumbios, and Pastaza), as well as the province with the capital city of Quito (Pichincha province) were obtained from the National Statistical Office of Ecuador, Instituto Nacional del Estadistica y Censos (INEC). Age- and sex-adjusted mortality rate ratios (RR) and 95% confidence intervals (CI) were estimated to evaluate total and cause-specific mortality in the study regions. Among Amazon cantons with long-term oil extraction, activities there was no evidence of increased rates of death from all causes (RR = 0.98; 95% CI = 0.95-1.01) or from overall cancer (RR = 0.82; 95% CI = 0.73-0.92), and relative risk estimates were also lower for most individual site-specific cancer deaths. Mortality rates in the Amazon provinces overall were significantly lower than those observed in Pichincha for all causes (RR = 0.82; 95% CI = 0.81-0.83), overall cancer (RR = 0.46; 95% CI = 0.43-0.49), and for all site-specific cancers. In regions with incomplete cancer registration, mortality data are one of the few sources of information for epidemiologic assessments. However, epidemiologic assessments in this region of Ecuador are limited by underreporting, exposure and disease misclassification, and study design limitations. Recognizing these limitations, our analyses of national mortality data of the Amazon Region in Ecuador does not provide evidence for an excess cancer risk in regions of the Amazon with long-term oil production. These findings were not consistent or supportive of earlier studies in this region that suggested increased cancer risks.