Background: The objective of this study is to evaluate the effects of traffic on human health comparing biomonitoring data measured during the COVID-19 lockdown, when restrictions led to a 40% reduction in airborne benzene in Rome and a 36% reduction in road traffic, to the same parameters measured in 2021. Methods: Biomonitoring was performed on 49 volunteers, determining the urinary metabolites of the most abundant traffic pollutants, such as benzene and PAHs, and oxidative stress biomarkers by HPLC/MS-MS, 28 elements by ICP/MS and metabolic phenotypes by NMR. Results: Means of s-phenylmercaputric acid (SPMA), metabolites of naphthalene and nitropyrene in 2020 are 20% lower than in 2021, while 1-OH-pyrene was 30% lower. A reduction of 40% for 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxodGuo) and 60% for 8-oxo-7,8-dihydroguanine (8-oxoGua) were found in 2020 compared to 2021. The concentrations of B, Co, Cu and Sb in 2021 are significantly higher than in the 2020. NMR untargeted metabolomic analysis identified 35 urinary metabolites. Results show in 2021 a decrease in succinic acid, a product of the Krebs cycle promoting inflammation. Conclusions: Urban pollution due to traffic is partly responsible for oxidative stress of nucleic acids, but other factors also have a role, enhancing the importance of communication about a healthy lifestyle in the prevention of cancer diseases.

The 2020 lockdown represented a natural experiment to measure the effects of traffic pollution on human health, due to the restrictions during the Covid-19 pandemic. In Rome a reduction of 36% of road traffic and of 40% of airborne benzene were observed. A biological monitoring campaign was carried out on Rome residents, aimed at identifying the biomarkers of exposure for the main urban pollutants, such as benzene and polycyclic aromatic hydrocarbons and biomarkers of oxidative stress to nucleic acids. A targeted analysis by liquid HPLC-MS/MS and an untargeted metabolomic analysis, with nuclear magnetic resonance (NMR) were carried out on urine samples of 47 volunteers collected in 2020 and in 2021. The results show that urinary concentrations of the benzene metabolite (SPMA) and some PAHs are lower on average in 2020 than in 2021. Three oxidative stress analysed, 8- Hydroxyguanine, 8-oxo-7,8-dihydro-guanosine and 8-oxo-7,8-dihydro-2’-deoxyguanosine are affected by the traffic reduction more than the dose biomarkers of the pollutants considered, suggesting an influence of the different lifestyle. The untargeted metabolomic analysis confirms the results of the targeted analysis, also highlighting an increase in succinic acid excretion in 2020 compared to 2021. The increase in urinary succinic acid concentration in 2020 is probably attributable to a different diet and a greater sedentary lifestyle during the lockdown period.