IARC 60th Anniversary - 19-21 May 2026
Session : 20/05/26 - Posters
Access to residential greenness and exposure to traffic noise at the time of delivery and risk of early-onset breast cancer
EDLUND J. 1, MATTISSON K. 2, WU W. 1, OUDIN A. 2,3, HARLID S. 1
1 Department of Diagnostics and Intervention, Oncology, Umeå University, Umea, Sweden; 2 Division of Occupational and Environmental Medicine, Department of Laboratory Medicine, Lund University, Lund, Sweden; 3 Department of Public Health and Clinical Medicine, Division for Sustainable Health, Umeå University, Umeå, Sweden
Background: Access to residential greenness has been suggested to reduce breast cancer risk by e.g. increasing the incentive for physical activity. Road and railway noise, on the other hand, may possibly increase the risk, by interfering with sleep and inducing stress.
Objectives: The aim of this study was to investigate associations between greenness access, and traffic noise exposure and risk of early-onset breast cancer. Exposures were assessed at time of delivery, to capture effects during the last pregnancy trimester and during early lactation which represent important and susceptible times in breast development.
Methods: From the Swedish Medical Birth Register, we identified women living in Stockholm, Gothenburg, and Malmö who gave birth to their first child between 1991 and 2015. Urban greenness within a 300m buffer and road/railway traffic noise (average nighttime levels) were assessed at the residential coordinates for each participant. Exposure levels were assessed at first delivery, last delivery, two years after the last delivery, and at 35 years of age. Associations between greenness, traffic noise and breast cancer were evaluated using Cox proportional hazards regression to estimate adjusted hazard ratios (HRs), using age as the time scale.
Results: At first delivery, the cohort included 252 465 individuals, of whom 3210 (1.3%) were diagnosed with early-onset breast cancer. At first and last delivery, an interquartile range increase in urban greenness was consistently inversely associated with breast cancer risk, although the associations were not statistically significant. However, among individuals whose first delivery occurred during the summer, higher urban greenness was associated with a decreased risk of breast cancer, HR = 0.90 (95% CI = 0.83-0.98). We found no association between road or railway traffic noise and breast cancer.
Conclusions: These results suggest that access to residential greenness, around the time of delivery, may have a protective effect on breast cancer, especially when accounting for seasonal variations.