Enrolment of the cohort and follow-up procedures
The General Registry Office of Forlì was the data source for the enrolment of the cohort. Subjects who resided in the study area on 1/1/1990, or who subsequently became residents until 31/12/2003, were enrolled in a retrospective longitudinal study. For those subjects who entered in the area after 1/1/1990, a minimum of five years of residence was required before starting the follow- up. The follow-up was carried out through record linkage with the regional mortality database (from 1990 to 2003) which includes all deaths of the resident population from anywhere in the country. The Cancer Registry database (from 1990 to 2003) and the Hospital Admissions database (from 1999 to 2003), provided by the Romagna Cancer Registry and the Regional Health Information System, were also used. Hospital admissions for specific causes were considered relevant for the study to evaluate cardiovascular and respiratory morbidity; the first admission for each subject and each cause was included in the analysis. Subjects were considered at risk for the various outcomes (mortality, cancer incidence, or hospitalization) until they died, moved outside the region, or until the last day of the follow-up (31/12/2003). The General Registry Office traced the geographical coordinates of all residences after 1990 but residential histories before 1990 were not available. The relevant residence of each subject was his or her home in 1990 or the first residence for later arrivals.