Positive effect of exposure to ambient air volatile organic compounds on clinic visits for atopic dermatitis.

Background: Exposure to air pollutants have been associated with exacerbations of atopic dermatitis (AD) symptoms, however, the role of each volatile organic compound (VOC) was rarely investigated.

Objective: This population-based study investigated associations between daily visits for AD at hospitals and exposure to each ambient air VOC in central-southern Taiwan.

Methods: The dependent variable with diagnostic code (ICD-9-CM code 691.8 and ICD-10-CM code L20) retrieved from National Health Insurance Research Database (NHIRD) from 2008/01/01 to 2018/12/31. Independent variables included one-day 75th-percentile value of each VOC and four meteorologic conditions retrieved from Taiwan Air Quality Monitoring Network Databases and four allergic diseases from NHIRD. This multivariable model was analyzed using both case-crossover study (adjusted odds ratio (AOR)) and Poisson model (adjusted relative risk (ARR)).

Results: Two study designs in total and each subgroup showed consistently significantly positive effects of each 12 ambient air VOC, especially highest in 1,3,5-trimethylbenzene and methylcyclohexane. The concentration of each 12 VOC was highly affected the total daily visits (AOR: 1.05-3.58, ARR: 1.03-3.74, P < 0.001), particularly highest for 1,3,5-trimethylbenzene (AOR = 3.58, ARR = 3.74, P < 0.001) and methylcyclohexane (AOR = 3.55, ARR = 2.13, P < 0.001). The results of each VOC were similarly positive in men and women. Children were the most vulnerable on the exposure to methylcyclohexane (AOR = 6.18, ARR = 2.35, P < 0.001), and 1,3,5-trimethylbenzene (AOR = 6.08, ARR = 4.62, P < 0.001). The results for older adults, adolescents, and younger adults were also significantly higher. In the analysis of five areas, mostly VOCs showed significantly higher effects using two methods. (Kappa = 0.44 vs 0.26).

Conclusion: 12 air VOCs can be considered as risk factors of daily visits for AD.