Date of review by ARPANSA
November 2024
Article publication date
October 2024
Summary
This systematic review and meta-analysis assessed the association between artificial light-at-night (ALAN) exposure and cancer incidence in human populations. A total of 28 studies (15 cohort, 13 case-control) were included in the review and meta-analysis. The strength of the association was reported in risk ratio (RR) with a 95% confidence interval (CI). RR of cancer (breast, prostrate, and others - colorectal, pancreatic, non-Hodgkin lymphoma and thyroid cancer) were assessed. The studies had indoor ALAN exposure data assessed through self-reported questionnaires, whereas outdoor ALAN exposure data were collected from satellite data. Risk of bias and quality of the included studies were evaluated using the tool recommended by the Joanna Briggs Institute (Munn et al. 2015). The meta-analyses showed no statistically significant association for indoor ALAN exposure and breast cancer, and outdoor ALAN exposure and prostate cancer. Higher levels of outdoor ALAN exposure were associated with increased breast cancer risk (RR =1.12, 95 % CI 1.03–1.23). The qualitative synthesis of evidence indicated positive associations between ALAN exposure and risk of non-Hodgkin lymphoma, colorectal, pancreatic and thyroid cancer. Overall, the included studies had high quality scores.
Published in
Science of the Total Environment
Link to study
ARPANSA's commentary
The review indicates an association between outdoor ALAN exposure and increased breast cancer. Importantly, this review contributes to the body of knowledge on the potential risk of cancer incidence associated with ALAN exposures. The risk estimates provided by this meta-analysis are comparable to those provided by other reviews (Urbano et al., 2021; Luo et al., 2023). Strengths of this review are that it included prostate cancer in the meta-analysis and other cancers in the qualitative review, and it critically appraised exposure assessment. Accordingly, it highlighted some methodological limitations of the included studies, such as self-reported assessment of indoor ALAN exposure that results in recall bias, exposure measurement error and exposure misclassification potentially biasing the risk estimates. Similarly, the satellite data used in estimating outdoor ALAN exposure in the included studies had poor spatial resolution and had no colour (e.g., blue light) data. Therefore, as highlighted in the review, future epidemiological research using robust GIS-based ALAN exposure data and methods, controlling for potential confounders (such as noise, pollution, green space) are needed to improve the risk estimates of cancer incidence.
The International Commission on Non-ionizing Radiation Protection (ICNIRP) has published a statement on short wavelength light (SWL) exposure from indoor artificial source and human health. The ICNIRP acknowledges that there is no scientific consensus on whether ALAN exposure from SWL light causes health effects. It is important to note that the studies informing an association between ALAN exposure and cancer risk have limitations. Therefore, well-designed epidemiological studies with improved exposure assessment tools are required to better inform on whether long-term ALAN exposure is a human health risk. There are also other publications which provide some recommendations for visible light exposure and potential health effects (e.g. SSLC, 2024; Brown et al., 2022).
