Low-level pollution - health impacts: evidence review

5 Conclusion

The Scottish Government commissioned a comprehensive review to examine the existing evidence on the health effects associated with low-level pollution in countries that have levels of ambient air pollution similar to Scotland. We conducted a robust, rapid evidence review focusing on the most recent publications since 1 January 2022 to complement the findings from supplementary searches which identified key literature, including the Dominski review and the three HEI reports.

The evidence identified in this review primarily focused on mental health and well-being, cognition, and dementia. However, it should be noted that this emphasis is likely an artefact of the review's temporal scope (2020 onwards), as the literature has extensively documented other health effects including CVD, respiratory and cancers for many years. Furthermore, this review considered the inconclusive evidence from Scotland regarding the association of air pollution with cardiovascular disease, as well as the potential contributing factors to this variation.

In conclusion, the evidence from global studies and reviews consistently supports the association between air pollution and various health outcomes, including CVD, respiratory health, mortality, cancer, neonatal health, type-2 diabetes, ocular outcomes, primary care healthcare service use, cognition, and neurological health. The studies also highlight the association between air pollution and mental health, including self-harm, psychopathology, major depressive disorder, and cognitive impairments. Furthermore, air pollution contributes to the development and exacerbation of dementias and is associated with neurological diseases such as Parkinson's disease, stroke, multiple sclerosis, and nervous system disorders.

While the global evidence is robust, the specific evidence regarding air pollution and health outcomes in Scotland is limited and inconclusive. When specifically considering CVD, some studies in Scottish cohorts support the global consensus, showing associations between air pollution and CVD, while others did not find significant associations, possibly due to methodological limitations and challenges in adjusting for confounding factors. Further research in the Scottish context, considering multiple pollutants and addressing data limitations, is necessary to provide more conclusive insights into the relationship between air pollution and health outcomes in Scotland.

Overall, the Dominski review, three HEI reports and recent evidence identified and discussed in this review emphasis the broad range of impacts from air pollution and the necessity to mitigate the harmful health effects of air pollution, promoting public health and well-being. As these harmful effects have been extensively evidenced at concentrations below national and international air quality standards, effective policies and interventions are necessary to reduce air pollution levels. In addition, further research is needed to better understand the underlying mechanisms behind these impacts and explore potential associations in specific health outcomes, allowing the development of prevention and targeted interventions in populations, particularly those most vulnerable.