Context. In France, there are significant geographical inequalities in the incidence of lung cancer, and the factors underlying these disparities remain poorly understood. Although the influence of socio-economic status and air pollution on individual risk is well established, their respective contributions to spatial disparities in lung cancer incidence in France have not yet been quantified. This study aimed to quantify the contribution of social inequalities and chronic exposure to air pollution to geographical disparities in lung cancer incidence in France.

Methods. We used a multivariate spatio-temporal model applied to lung cancer incidence data from 2006 to 2020, at the departmental level of the FRANCIM network. The contributions of the social environment measured by the European Deprivation Index (EDI) and exposure to PM10 (Particulate Matter <10μm) to spatial variations were estimated by geographical areas defined by departmental contiguity. The evolution of geographical variability was compared before and after including the two determinants.

Results. Marked contrasts in incidence were observed across all areas studied. Adding the social environment (EDI) and PM10 to the model reduced geographical variability, making the disparities less pronounced. In men, the contribution of the social environment, varying between 23% and 67%, was systematically higher than that of exposure to PM10 in all regions. In women, the contribution of the social environment was lower than in men, varying between 4% and 35%, but remained higher overall than that of PM10, with the exception of two areas, where exposure to air pollution (PM10) had a better impact.

Conclusion. Our results showed that social inequalities were the main determinant of geographical disparities in lung cancer incidence in France, ahead of air pollution. However, the relative importance of these factors varied according to gender and region, highlighting the need for targeted regional approaches. This study provided an initial estimate of the respective contributions of the socio-economic environment and exposure to PM10 to spatial inequalities in incidence, and highlighted the value of prevention strategies tailored to local contexts.