Summary
Background and aim. Asthma and chronic obstructive pulmonary disease (COPD) are leading causes of morbidity and mortality worldwide. Globally, 545 million people suffer from chronic respiratory diseases with a wide geographical variability. Risk factors for asthma are both genetic and related to several environmental factors (internal and external pollutants); these also have an important role in the occurrence of COPD. The aim of this study was to describe the prevalence of asthma, COPD, and asthma/COPD overlap (ACO) in an adult population living in two municipalities located in the Po Valley. Methods. A standardized questionnaire on respiratory symptoms and sociodemographic characteristics was self-administered to a random sample of the adult population aged 20–64 years, living near a refinery in Northern Italy during the period between 2016 and 2019. Logistic and multinomial regression were implemented to explore factors associated with asthma, COPD, and ACO. Results. In total, 1108 subjects filled out the questionnaire, the mean age was 48.02 ± 12.34 years (range 21–68), and 53% of the respondents/participants were female. Half of the responders were non-smokers, but the frequency of current and former smokers was significantly greater in men than in women (p < 0.001). The likelihood of being a probable case of asthma decreased with increasing age and increased for smokers. Tobacco smoke was associated with the presence of COPD and ACO. Conclusion. Respiratory diseases such as asthma and COPD are common in the general population, with differences among countries worldwide. Our findings show, on the basis of the main confirmed risk factor, namely smoking, that it is useful to plan target programs and actions in order to reduce smoking, thus improving the quality of life in public health.

Relevance
The present study aimed to estimate the prevalence of asthma, COPD, and ACO within an adult population (20–64 years) living near an oil refinery located in the north of Italy (Lombardy Region, Province of Pavia). Our findings may be useful for local healthcare professionals, decision-makers, and stakeholders to improve, analyze, and evaluate the burden of these respiratory diseases, in order to implement and optimize clinical programs and public health strategies.