Short-term exposure to air pollution as a result of wildfire was associated with increased health care use among patients with atopic dermatitis and itch, according to the results of a cross-sectional study published in JAMA Dermatology.

Researchers noted that epidemiologic studies on skin diseases have focused on chronic exposure to air pollution, but as environmental conditions change, it has become increasingly important to assess the association between acute exposure and common cutaneous diseases, such as atopic dermatitis. Therefore, the researchers conducted a cross-sectional time-series study to assess the associations of air pollution from the California Camp Fire in November 2018 and dermatology clinic visits at an academic tertiary care hospital system in San Francisco, 175 miles from the wildfire source.

Data collected included daily 24-hour mean particulate matter less than 2.5 µm in diameter (PM2.5), daily mean temperatures, and relative humidity. Researchers characterized wildfire-associated air pollution using 3 metrics: fire status, concentration of PM2.5, and satellite-based smoke plume density scores. Participants had atopic dermatitis or itch from before, during, after the time of the fire (October 2018 through February 2019). A total of 3448 adult patients and 699 pediatric patients were included in the study.


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For atopic dermatitis, the rates of weekly clinic visits during the Camp Fire were 1.49 (95% CI, 1.07-2.07) times the rate for weeks without wildfires at lag 0 for pediatric patients and 1.15 (95% CI, 1.02-1.30) times the rate for weeks without wildfires at lag 0 for adults, adjusted for temperature, relative humidity, patient age, and total patient volume, at the clinics for pediatric patients. A 10-µg/m3 increase in weekly average PM2.5 concentration was associated with a 5.1% (95% CI, 0.8%-9.7%) increase in average weekly pediatric atopic dermatitis clinic visits.

For pediatric itch, the adjusted rate ratios for weekly visits were 1.82 (95% CI, 1.20-2.77) for fire status and 1.55 (95% CI, 1.15-2.09) for average weekly smoke plume density score. A 10-µg/m3 increase in weekly mean PM2.5 concentration was associated with a 7.7% (95% CI, 1.9%-13.7%) increase in weekly visits for pediatric itch. The rate ratios for pediatric itch visits were typically largest for lag 0 and decreased from lag 0 to lag 4 for all 3 exposure metrics.

Results also demonstrated a statistically significant association between air pollution exposure and number of systemic medications among adults, including prednisone, for the early lags in all 3 exposure metrics. At lag 0, the adjusted rate ratio for prescribed systemic medications during the Camp Fire was 1.45 (95% CI, 1.03-2.05). For topical medications, the adjusted rate ratios were greater than 1 but did not reach statistical significance, expect for lag 0 for the smoke plume density metric (1.14; 95% CI, 1.01-1.28).

The authors noted several study limitations, including the patient population being restricted to San Francisco and visiting one health care system, both of which may limit the generalizability of the results. Additionally, air pollution from wildfires is “chemically heterogeneous,” which means that the PM2.5 composition of the Camp Fire may not match that of other wildfires. Lastly, the researchers focused on patients who were seen at dermatology clinics and did not include patients who visited primary care clinics.

“These results may provide a better understanding of the association between poor air quality and skin health and guide health care professionals’ counseling of patients with skin disease and public health practice,” concluded the study authors.

Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Fadadu RP, Grimes B, Jewell NP, et al. Association of wildfire air pollution and health care use for atopic dermatitis and itch. JAMA Dermatol. Published online April 21, 2021. doi:10.1001/jamadermatol.2021.0179