Fine particulate matter linked to higher eczema risk

Study links higher air pollution exposure to increased risk of eczema, with PM2.5 concentrations nearly doubling the odds of the condition.

Study: Association between fine particulate matter and eczema: A cross-sectional study of the All of Us Research Program and the Center for Air, Climate, and Energy Solutions. Image Credit: Shutterstock AI / Shutterstock.com

Eczema is an inflammatory skin condition that affects 5.5-10% of adult Americans, as well as 10.7% of children. The global incidence of eczema has risen since the Industrial Era, thus suggesting that environmental exposures including ambient air pollution (AAP) likely contribute to the development of this skin condition.

In a recent study published in PLoS One, researchers explore the association between exposure to fine particulate matter and the risk of eczema.

AAP and human health

In 2019, AAP exposure contributed to at least 4.2 million deaths globally. Fine particulate matter (FPM), defined as particles less than 2.5 μm (PM2.5) in size, comprises a significant proportion of AAP and can penetrate deep into the respiratory system. In fact, FPM can cross alveolar epithelial cells to enter the bloodstream or lymphatic channels, thereby allowing for their dissemination to other organs, including the skin.

PM_2.5 contains many different components, including polycyclic aromatic hydrocarbons (PAHs), which can easily penetrate the stratum corneum and disrupt the skin barrier. This can lead to oxidative damage and inflammatory dysfunction mediated by altered signaling in the aryl hydrocarbon receptor (AhR) pathway. These phenomena are exacerbated in the presence of cutaneous lesions, which are often present in eczema.

Available research indicates a positive association between eczema severity and PM_2.5 levels among children during the winter months despite an inverse association with eczema prevalence. Despite these observations, few studies have examined how eczema is affected by PM_2.5 in the United States.

About the study

The current cross-sectional study utilized data obtained from the All of Us Research Program, which includes participants from groups that are traditionally marginalized in biomedical studies. Data from 12,695 people with eczema and 274,127 people without eczema were included in the analysis.

These data were linked to the mean annual PM_2.5 levels from 788 locations obtained from the Center for Air, Climate, and Energy Solutions (CACES). The most recent CACES data available was from 2015, which was selected as the year of focus for this study.

All observed associations were adjusted for demographic and lifestyle factors, including smoking, as well as atopic conditions like food allergy, allergic rhinitis, asthma, and eosinophilic esophagitis.

Eczema linked to PM2.5 concentrations

In all three models, eczema cases were concentrated in areas with significantly higher PM_2.5 levels as compared to non-eczema cases at 0.83 x 10 μg/m³ and 0.81 x 10 μg/m³, respectively. In the unadjusted model, the risk was doubled with higher PM_2.5 concentrations.

After compensating for demographic and smoking status, the risk of eczema was more than twice as high among those who lived in areas with high PM_2.5 levels at 2.58. In the fully adjusted model that accounted for atopic conditions, the risk of eczema was 166% higher in areas with higher PM_2.5 concentrations.

Compatibility with earlier research

The study findings align with other global studies conducted in Germany, Taiwan, and Australia, which similarly reported a two-fold increased risk of eczema in areas with every increase in PM_2.5 concentrations by 10 μg/m³.

The study cohort may not have been representative of American demographics or regions; therefore, these findings may not reflect known differences in the prevalence of eczema between rural and urban areas. Nevertheless, the study findings accurately indicate that certain risk factors like atopic disease or smoking increase the risk of eczema.

Putative mechanisms

PM_{2.5 contains PAHs that can activate the AhR pathway, which is associated with an eczema-like reaction in mice. Increased levels of chemicals that trigger this pathway, like artemin or reactive oxygen species, mediate this reaction}.

Conclusions

The study findings demonstrate that ambient air pollution is related to inflammatory skin disease, thus emphasizing the need for targeted interventions that could reduce the incidence of eczema.

The United States Environmental Protection Agency (EPA) Air Quality Index (AQI) is calculated from PM_2.5 concentrations expressed in orders of magnitude. With worsening air quality, which is defined as moderate or worse AQI, individuals with eczema residing in these areas may be at a greater risk of experiencing flare-ups.

Strategies to prevent these health effects could include public health advice to stay indoors, use air filters, or protect skin from exposure to polluted outdoor air. Pharmacological AhR agonists capable of mitigating the activation of the AhR pathway through canonical signaling are also being investigated.