Is Air Pollution Triggering Autoimmune Diseases?
Featured image caption: Air pollution from a power plant in New Mexico, USA, in 2005. (Image source: “Air pollution by industrial chimneys,” National Park Service, Public domain, via Wikimedia Commons).
Source article: Zhang, M., Wang, Y., Hu, S., & Wu, Y. (2025). Causal relationships between air pollution and common autoimmune diseases: a two-sample Mendelian randomization study. Scientific Reports, 15(1), 135. https://doi.org/10.1038/s41598-024-83880-9
The environment and autoimmune disease
The immune system protects the body by attacking invaders, like bacteria and viruses, that make you sick. But in autoimmune diseases, the immune system mistakenly attacks the body’s own tissues. This leads to tissue damage, inflammation, and other problems. Autoimmune diseases are on the rise worldwide,1 prompting scientists to ask why.
Environmental changes, such as pollution, climate change, and diet, may be key drivers of the increasing incidence of autoimmune diseases.2 While several studies suggest that environmental factors, such as air pollution, are associated with autoimmune disease,3-5 establishing a causal link between pollution and disease remains challenging.
Testing whether a factor of interest causes disease
Randomized controlled trials, in which participants are assigned to an intervention or control group, are the standard method for establishing causality. However, these trials require substantial time and financial resources and are subject to ethical constraints.
An alternative approach for establishing causality is called Mendelian randomization. Essentially, this method randomizes participants by genetic markers, allowing scientists to control for potential confounding variables and identify risk factors that influence disease. This method uses natural variation to test questions, meaning scientists don’t need to assign study participants to potentially risky interventions.
Exposure to air pollutants increases the risk of developing autoimmune diseases
In a study recently published in Scientific Reports, Zhang et al. used Mendelian randomization to test for a causal relationship between air pollutants and autoimmune disease. The researchers leveraged large preexisting datasets containing genetic and health data on thousands of Europeans. The researchers focused on common air pollutants: nitrogen oxides and particulate matter (PM). Nitrogen oxides are gases produced by burning fuel.6 PM are particles emitted from vehicle exhaust and wildfires, as well as dust from agriculture and construction.7 The researchers divided PM into three categories based on particle size: PM2.5 included particles less than 2.5 microns, PM2.5-10 included particles between 2.5 and 10 microns, and PM10 included particles less than 10 microns.7 Nine autoimmune diseases were included in the study: rheumatoid arthritis, systemic lupus erythematosus, Crohn’s disease, multiple sclerosis, Sjogren’s syndrome, type 1 diabetes, ulcerative colitis, psoriasis, and ankylosing spondylitis. In their analysis, the researchers also considered common risk factors for autoimmune diseases unrelated to air pollution, such as BMI and alcohol use.
The study found evidence supporting a causal link between common air pollutants and autoimmune disease. Exposure to nitrogen oxides was associated with an increased risk for three of the nine autoimmune diseases: rheumatoid arthritis, systemic lupus erythematosus, and Sjogren’s syndrome. Exposure to PM2.5 and PM10 was linked to a higher risk of ulcerative colitis and psoriasis.
The researchers noted some limitations of their study. For example, the study included only participants of European ancestry, which may limit the generalizability of its findings. Moreover, the study did not explore the biological mechanisms through which air pollution may cause autoimmune disease. Further research is needed to establish how exposure to pollutants such as PM and nitrogen oxides drives autoimmune diseases.
In summary, Mendelian randomization is a powerful tool that allows scientists to establish causal links between risk factors and disease. Evidence from these studies can inform policymakers and healthcare providers, enabling them to advocate for changes that reduce our exposure to harmful risk factors.
Secondary sources:
1. Miller, F. W. (2023). The increasing prevalence of autoimmunity and autoimmune diseases: an urgent call to action for improved understanding, diagnosis, treatment, and prevention. Current opinion in immunology, 80, 102266. https://doi.org/10.1016/j.coi.2022.102266
2. The Environment and Autoimmune Disease. Autoimmune Association. Published May 15, 2025. https://autoimmune.org/resource-center/education/environment/
3. Tang, C., Li, Q. R., Mao, Y. M., Xia, Y. R., Guo, H. S., et al. (2021). Association between ambient air pollution and multiple sclerosis: a systemic review and meta-analysis. Environmental Science and Pollution Research, 28(41), 58142-58153. https://doi.org/10.1007/s11356-021-14577-z
4. Adami, G., Pontalti, M., Cattani, G., Rossini, M., Viapiana, O., et al. (2022). Association between long-term exposure to air pollution and immune-mediated diseases: a population-based cohort study. RMD open, 8(1), e002055. https://doi.org/10.1136/rmdopen-2021-002055
5. Ma, K. S. K., Wang, L. T., Chong, W., Lin, C. L., Li, H., Chen, A., & Wei, J. C. C. (2023). Exposure to environmental air pollutants as a risk factor for primary Sjögren’s syndrome. Frontiers in Immunology, 13, 1044462. https://doi.org/10.3389/fimmu.2022.1044462
6. Environmental Protection Agency. Basic Information about NO2. EPA. Published July 10, 2025. https://www.epa.gov/no2-pollution/basic-information-about-no2
7. California Air Resources Board. Inhalable Particulate Matter and Health (PM2.5 and PM10). Ca.gov. Published 2015. https://ww2.arb.ca.gov/resources/inhalable-particulate-matter-and-health
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