Parallel Descriptive Assessments of Indoor Radon (2023) and Regional Hospital Cancer Registry Records (2003–2023) in Midwestern Santa Catarina, Brazil

Radon is an established environmental cause of lung cancer, but residential surveillance is limited in Brazil. This study comprised two complementary, analytically independent components: indoor radon monitoring in Caçador, and Hospital Cancer Registry records of tracheal, bronchial and lung cancers in a 27-municipality regional analytical area, with comparisons to Santa Catarina and Brazil. Radosys RSKS CR-39 detectors were deployed for three months at 32 locations (26 residential, 6 commercial; 57 measurements); structured interviews assessed building and occupancy features. Registry records (2003–2023) were analysed descriptively. Median location-level radon concentration was 20.3 Bq/m3 (range 7–112 Bq/m3). One bedroom measurement and one commercial location exceeded the World Health Organization residential benchmark of 100 Bq/m3, while all remained below the Brazilian 300 Bq/m3 reference level for dwellings and other high-occupancy areas. Masonry with external coating (68.8%), ground-contact foundations (90.6%), and at least one active smoker in 34.4% of locations were reported. The regional analytical area comprised 356 records; across all territorial levels, men, adults aged 60–69 years, and adenocarcinoma predominated, with substantial missing data on smoking history, family history, and staging. Findings provide a regional baseline for targeted radon monitoring and improved cancer registry data quality.