Fine Particulate Matter and Eczema

The primary objective of this study was to investigate the potential associations between fine particulate matter (specifically PM2.5) exposure and eczema. Researchers on this study set out to explore whether the odds of having eczema would increase with greater PM_2.5 exposure, and to identify whether ambient air pollution is a contributor to the pathogenesis of inflammatory skin conditions such as eczema.¹ 

Background and Study Results

Eczema (atopic dermatitis [AD]) is a chronic inflammatory skin condition that causes intense pruritus and eczematous lesions and is the leading cause of nonfatal chronic skin conditions. Eczema causes a significant psychosocial and mental health burden on patients and their caregivers, in addition to increasing the risk of comorbid atopic conditions such as asthma, food allergies, and other immune-mediated conditions.² As the prevalence of AD rises worldwide, research has begun to identify certain environmental conditions as major contributors to its pathogenesis, in addition to immune and genetic factors. Specifically, exposure to outdoor pollutants has been shown to exacerbate or even initiate eczema through oxidative damage or immune disruption.³

Study researchers used a diverse set of health data from American adults via the All of Us Research Program to link the participants’ zip code locations to the average annual concentrations of PM_2.5 in their respective areas. The PM_2.5 data were obtained from Air, Climate, and Energy Solutions (CACES), which utilizes satellite, US Environmental Protection Agency (EPA) monitoring, and land use, while urbanity was identified using the US Census Bureau’s block-level urban-rural classifications for the 2020 Census. Using electronic health records, 12,695 participants were identified as having eczema, while 274,127 participants were identified as not having eczema. After adjusting for demographic factors, smoking status, and atopic comorbidities, those with eczema are shown to live in areas with significantly higher PM_2.5 concentrations (8.3 μg/m³ vs. 8.1 μg/m³, P < .001). Univariable analysis showed that the odds ratio (OR) for having eczema with increased PM_2.5 exposure is 1.97 (95% CI: 1.77–2.19). Multivariable analysis, which adjusted for demographic factors, smoking status, and BMI, showed an even stronger OR of 2.58 (95% CI: 2.26-2.95). Additionally, adding comorbid atopic conditions to the model increased the OR even further to 2.66 (95% CI: 2.32-3.05). 

Comments/Clinical Implications

The results of this study strongly suggest that air pollution, specifically PM_2.5, is a risk factor for the development and exacerbation of eczema. The results show that increased PM_2.5 exposure raises the odds of having eczema, with individuals who have preexisting atopic conditions, such as asthma, rhinitis, or eosinophilic esophagitis, being particularly vulnerable. These findings suggest that efforts to reduce exposure to PM_2.5 may be actionable and effective in reducing eczema morbidity. The limitations include the fact that it is cross-sectional, therefore causation cannot be established. Additionally, further research may be recommended to better understand the mechanisms by which the aryl hydrocarbon receptor (AhR) pathway affects eczema, as well as the mechanisms behind the increased vulnerability of individuals with existing atopic conditions to the effects of PM_2.5. 

The EPA Air Quality Index (AQI), which is based on PM_2.5 concentrations, may be utilized as a tool to counsel eczema patients to modify their time spent outdoors when the AQI reaches “moderate” (12.1–35.4 μg/m³) levels, as risk of worsening disease increases for them at this level and beyond. Regarding the proposed role of the AhR pathway in PM_2.5-related eczema, further research is needed. Studies have suggested that AhR activating drugs work as both modulators of environmental toxins and immune modulators that can reduce systemic inflammation in autoimmune diseases.⁴ Additional research into the use of these drugs for pollution-related eczema may be promising. 

1. Chen GF, Hwang E, Leonard CE, Cohen JM. 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. PLoS One. 2024;19(11):e0310498. doi.org/10.1371/journal.pone.0310498

2. Weidinger S, Novak N. Atopic dermatitis. Lancet. 2016;387(10023):1109-1122. doi.org/10.1016/S0140-6736(15)00149-X

3. Kantor R, Silverberg JI. Environmental risk factors and their role in the management of atopic dermatitis. Expert Rev Clin Immunol. 2017;13(1):15-26. doi.org/10.1080/1744666X.2016.1212660

4. Cannon AS, Nagarkatti PS, Nagarkatti M. Targeting AhR as a novel therapeutic modality against inflammatory diseases. Int J Mol Sci. 2021;23(1):288. doi.org/10.3390/ijms23010288