Impact of particulate matter exposure on melanoma risk: A multicentre case–control study

Background: The relationship between particulate matter (PM) exposure and melanoma risk remains largely unexplored. This study aims to investigate the association between PM10 and PM2.5 long-term exposure and melanoma risk. Methods: Case–control study involving 2575 participants, comprising 1473 melanoma patients and 1102 healthy controls attending Departments of Dermatology of University Hospital in North and Central Italy. Demographic data, smoking status, history of sunburns and skin type were collected. PM10 and PM2.5 exposure levels were estimated for each participant's residential address using a Bayesian hierarchical model, providing daily concentrations at a 1km2 spatial resolution from 2013 to 2021. Logistic regression analyses were performed to evaluate the association between PM exposure and melanoma risk, adjusting for potential confounders. Results: Melanoma patients and controls were 52% males and had a mean age of 63.89 and 61.66 years, respectively. The majority of melanoma patients had Fitzpatrick phototypes 2 (59%) and 3 (36%). There were no significant differences in the geographical distribution of cases and controls based on ZIP codes (p=0.894). The average melanoma Breslow thickness was 1.01mm, with 68.15% of cases diagnosed at stage 0 and IA. The multivariate logistic regression revealed a protective effect for higher PM10 (OR=0.89, 95%CI: 0.86–0.92, p<0.001) and PM2.5 levels (OR=0.72, 95%CI: 0.68–0.76, p<0.001). Darker skin phototypes (Fitzpatrick 4) and cigarette smoking were also associated with a reduced risk of melanoma. Conclusions: Higher levels of PM10 and PM2.5 may have a protective effect against melanoma, potentially due to the reduction in ultraviolet radiation exposure. Further research to understand the complex interactions between environmental factors and melanoma risk are needed.