Individuals exposed to ambient sulfur dioxide (SO₂) and particulate matter (PM₁₀) were most associated with greater risk of allergic diseases, according to findings from a newly-developed model designed to estimate daily averages of such types of pollution.¹

These findings and the new model resulted from a study conducted in China to improve upon prior research evaluating ambient air pollutants’ impacts on allergic disease and that had been based upon population-average exposure data.² This prior research had averaged the amounts of pollutants in the atmosphere at air-monitoring stations.

The new model and the research around it was led by Qing-Ling Fu, from the Otorhinolaryngology Hospital and Department of Allergy at Sun Yat-sen University’s First Affiliated Hospital in Guangzhou, China.

“Biased effect estimates may occur in (the previous) studies, since spatial gradients and individual variations in exposure were not considered,” Fu and colleagues wrote. “Herein, we aimed to assess the effects of ambient air pollution on outpatient visits for allergic diseases using individual exposure data.”

Background and Findings

The investigators had created their model in a previous study to accurately estimate daily average levels of fine particulate matter (PM_2.5) and O₃ across Mainland China using a resolution of 1 km x 1 km.² They gathered the individual information of outpatients who had paid visits to the Department of Allergy at the Second Affiliated Hospital of Guangzhou Medical University in the time frame between 2014 - 2019.

The research team linked patients' addresses to the grid-based pollution levels to assess the impact of PM_2.5 and O₃ pollution exposure on these individuals, and they linked their addresses using longitude and latitude. In order to look at the effects of pollutant exposures on these subjects, the team utilized conditional logistic regression and a time-stratified case-crossover design.

This method made it so that the investigators could account for traditional confounding variables like participants’ gender and smoking habits. Additionally, the team assessed the effects of population-average exposure to several different types of pollutants, including PM_2.5, O₃, PM₁₀, sulfur dioxide (SO₂),nitrogen dioxide (NO₂), and carbon monoxide (CO), using daily average data from 10 monitoring stations found in Guangzhou.

The research team ended up looking at a group of 16,647 total outpatients who were found to have had allergic conditions. They reported the most common allergy to be urticaria at 35.5%, followed then by allergic rhinitis at 22.4%, atopic dermatitis at 9.2%, and asthma at 2.8%.

A majority of the cases examined by the investigators were noted as being female, at 57.46%, with 61.90% being under the age of 35 years. The team found that subjects’ exposure to PM_2.5 and exposure to O₃ led to immediate adverse effects, adding that the effects hit their peaks the following day.

Specifically, the investigators noted an increase of 10 μg/m3 in PM_2.5 and O₃ led to a 2.13% and 0.92% increased risk of diseases related to allergies on the same day and the day following, respectively. They also found that the overall exposure of subjects to PM_2.5, PM₁₀, O₃, and SO₂ were linked to a greater risk of allergic diseases, noting that there were excess risks of 1.43%, 1.12%, 1.10%, and 9.98%, respectively.

Interestingly, the research team did not observe this effect for NO₂ and CO. Overall, the team’s research stands out as the first of its kind to look at the effects of daily PM_2.5 and O₃ exposure on outpatient visits that had been made for allergies through satellite-derived data on pollution at a 1-km resolution.

Though the monitoring of pollution information confirmed the investigators’ findings, it presented a somewhat different set of effect estimates. They note the importance of highlighting that only a single prior study had assessed the effects of PM_2.5 at a 10 km × 10-km resolution with relation to allergic diseases in preschool children across 6 cities in China from the Global Burden of Disease project.

This particular new research by the investigators authentically showed subjects’ levels of pollution exposure using grid-level data, majorly diminishing exposure measurement issues and biases in estimates of air pollution impact.

“In conclusion, this study highlights the adverse effects of PM_2.5 and O₃ on allergic diseases,” they wrote. “Additionally, exposure to ambient SO₂ and PM₁₀ are associated with an increased risk of allergic diseases. These findings support efforts to mitigate ambient air pollution and protect people susceptible to allergens by recommending safety limitations.”

References

1. ^{He, B.-X., Ma, J.-J., Lai, H., Li, C.-G., Huang, L.-X., Huang, H.-N., Liu, X.-Q., Zhou, Z.-R., Xie, Y.-C., Kuang, P.-P., Ou, C.-Q. and Fu, Q.-L. (2023), Association between daily 1-km resolution levels of ambient air pollution and hospital visits for allergic diseases. Allergy. https://doi.org/10.1111/all.15904.}
2. ^{Chen ZY, Jin JQ, Zhang R, et al. Comparison of different missing-imputation methods for MAIAC (multiangle implementation of atmospheric correction) AOD in estimating daily PM2.5 levels. Remote Sensing. 2020; 12(18): 3008.}