Colorectal Cancer and Disinfection By-Products in Italy and Spain

Background/Aims: Experimental data suggests that disinfection by-products (DBPs) are colorectal carcinogens but epidemiological evidence is contradictory. To evaluate colorectal cancer risk associated with long-term DBP exposure. Methods: A case-control study was conducted in Italy and Spain. Cases were newly diagnosed and histollogically confirmed, 20-85 years old and living in the study areas. Controls were matched to cases by age, gender and area of residence. Study area comprised Barcelona (Spain) and Milan, Pordenone and Udine (Italy). Study subjectswere interviewed on potential risk factors of colorectal cancer, residential history and water uses including ingestion, showering, bathing, dishwashing and swimming in pools. Blood samples were collected to obtain DNA sample. Retrospective data ontrihalomethane levels in the study areas has been collected through water companies and water samples have been collected to measure a range of DBPs.Results: Based on 500 cases and 436 controls in Spain and 400 cases and 363 controls in Italy, the longest residence lasted 35 years on average in Spain and 37 years in Italy. Drinking water at the longest residence was from public water supply among 56% subjects in Spain and 46% in Italy. The rest consumed bottled water or from othersources. Those drinking water from public supplies compared to bottled water had an odds ratio (OR) and 95% confidence interval of 1.17 (0.87-1.58) in Spain and 1.18 (0.79-1.77) in Italy, adjusting for potential confounders. Taking long compared to short showers(above vs. below median) yield an OR of 1.04 (0.80-1.40) in Spain and 1.16 (0.83-1.63) in Italy. Mean trihalomethane levels in Italy wereConclusion: These initial results suggest a weak association between colorectal cancer and DBP exposure