An Exercise-Pollution Exposure Index for Assessing Inhaled Heavy Metal Exposure Along Urban Walking Routes

Urban walking routes are promoted as health-supportive environments, yet they may also act as microenvironments of pollutant exposure during physical activity. This study evaluated heavy metal exposure along urban walking routes by integrating road dust metal concentrations, conventional health risk assessment, deposited inhalation dose, and the Exercise-Pollution Exposure Index (EPEI). Road dust samples were collected from 17 sites in Samsun, Türkiye, representing industrial, high-traffic, residential, and recreational walking-route categories. Twelve elements, namely V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba, As, and Pb, were determined using USEPA 3050B digestion followed by ICP-MS analysis. Conventional noncarcinogenic and carcinogenic risk indices remained within acceptable limits under the average adult exposure scenario. However, high-traffic and industrial walking routes generally showed higher exposure profiles than residential and recreational walking routes. Cr made the highest contribution to inhalation-related carcinogenic risk, whereas Mn and Zn dominated the deposited inhalation dose. EPEI is a dimensionless, background-normalized screening indicator, with 100 representing the recreational walking-route reference condition. It provides a complementary route-level perspective by incorporating walking-related inhalation and respiratory deposition. This study highlights urban walking routes as distinct exposure microenvironments and presents EPEI as a useful screening tool for comparing relative inhalation exposure potential during outdoor physical activity.