LAUSR

OBJECTIVES to compare the cohort and case-control approaches to evaluate the health effects of an incinerator. DESIGN dispersion maps have been used to identify subjects exposed to the pollutants from the considered incinerator. Both cohort and case-control approaches have been applied to the study population to evaluate the following outcome: hospitalization for cardiovascular and respiratory causes between 2012 and 2014. The same two approaches have been applied to simulated populations, to which the risk and the base prevalence of the outcome have been varied. SETTING AND PARTICIPANTS a total of 218,445 subjects living in 7 municipalities impacted from the fallout of the incinerator of Busto Arsizio (Lombardy Region, Northern Italy) have been included in this study. For the simulated analysis the samples of 100,000 subjects have been used, with age and sex standardization on Italian population of year 2000. MAIN OUTCOME MEASURES the cohort approach estimated the risk ratio to have been hospitalized for the subjects exposed to the pollutants compared to the non-exposed subjects, while the case-control approach estimated the odds ratio for the cases to be exposed compared to controls. RESULTS both the cohort and the case-control approaches show an excess in risk of being hospitalized for cardiovascular causes, for subjects exposed to the emissions of SO2 and NOx. The results of the simulations show how much the odds ratio overestimates the risk ratio, increasing risk and prevalence. CONCLUSION the cohort and case-control approaches are comparable in the real proposed example. Considering that necessary resources for a case-control approach are lower than the ones in a cohort approach, and under the limits of applicability to prevent an excessive overestimation of risk, the case-control approach is considered to be taken into account to evaluate health impact of environmental exposures, as from incinerators.