Long-Term Traffic-Related Air Pollution Exposure Linked to Impaired Sense of Smell

The findings are based on data from the KORA FIT study, a population-based cohort in Augsburg, Germany. The study assessed 3,059 participants, aged between 54 and 74 years, using the standardized Sniffin’ Sticks 12-Item Test to measure olfactory function. 

The results show that higher concentrations of several traffic-related air pollutants – such as nitrogen dioxide (NO₂), fine particulate matter (PM₂.₅), and ultrafine particle number concentration (PNC) – were consistently associated with increased odds of hyposmia or anosmia (reduced or lost sense of smell). Notably, these associations were observed in Augsburg, a region characterized by comparatively low air pollution levels. 

“We observed that people with higher long-term exposure to traffic-related pollutants were more likely to exhibit impaired odor identification,” says Dr. Nikolaos Nikolaou, first author of the study. “This is particularly noteworthy given that changes in olfactory function may precede clinical symptoms in several neurodegenerative diseases.” 

The analysis adjusted for various potential confounding factors, including age, sex, lifestyle behaviors, socioeconomic status, and pre-existing health conditions. Interestingly, the study found that women and physically active individuals might be more susceptible to the observed associations. 

“This research underscores the subtle yet measurable effect of sustained air pollution on cognitive function, even in environments where pollutant levels are relatively low,” says Dr. Alexandra Schneider, senior author and Deputy Director of the Institute of Epidemiology (EPI) at Helmholtz Munich. “Our findings highlight that ambient air pollution can affect neurological pathways, thereby supporting the evidence for particle translocation from the nose to the brain. This emphasizes the need for public health policies aimed at reducing traffic emissions.”