Wildfire Air Pollution Linked to Jump in Atopic Dermatitis and Itch Dermatology Visits

By Linda Carroll

April 22, 2021

(Reuters Health) - Clinic visits for eczema as well as itch in adults and children rose during a major Northern California wildfire, a new study finds.

An analysis of data from more than 4,000 patients seen at San Francisco-area dermatology clinics revealed that visits for these skin issues increased by a factor of 1.49 in children and 1.15 in adults during the 2018 Camp Fire, researchers report in JAMA Dermatology.

"We found that wildfires could explain some flares of existing skin disease," said study coauthor Dr. Maria Wei, a professor of dermatology at the University of California, San Francisco. "They were also likely to irritate healthy skin even with a short period of exposure. We were quite surprised by the magnitude of the finding."

"Skin is the largest organ and it's in constant contact with the surrounding environment, so it makes sense that it could be irritated and inflamed during period of poor air quality," Dr. Wei said. "We were focusing on patients with underlying skin disease, atopic dermatitis, who were experiencing increased symptoms. They were coming in for systemic medications. In addition to these patients, many without a diagnosis, were coming in for itch during the fire."

To take a closer look at the potential impact of wildfires on skin health, Dr. Wei and her colleagues collected environmental data for San Francisco and clinical data for patients seen at the UCSF's dermatology clinics in the 18 weeks encompassing the time before, during and after the Camp Fire (October 2018-February2019), as well as the corresponding dates from previous years when there were no large wildfires close to San Francisco (October 2015-February 2016, and October 2016-February 2017).

The researchers collected daily 24-hour mean PM2.5 concentrations from the Bay Area Air Quality Management District's air quality monitoring station in San Francisco. They acquired mean daily smoke plume density scores (ranging from none, to light, medium, or heavy) for all San Francisco zip codes from the National Oceanic and Atmospheric Administration Hazard Mapping System for Fire and Smoke.

The California Camp Fire started on November 8, 2018, and was contained 17 days later, on November 25. It caused a nine-fold increase in average weekly PM2.5 concentration during a two-week period, which peaked during the second week of the fire.

Across all three time periods included in the analysis, there were a total of 6,439 visits for atopic dermatitis and 1,610 for itch. During the Camp Fire, 89% of the adults who presented with itch were not previously diagnosed with atopic dermatitis, compared with 59% of patients during the same two weeks in 2015 and 51% in 2016.

The rate of visits for atopic dermatitis during the Camp Fire for pediatric patients was 1.49 times that of non-fire weeks, and for adult patients, 1.15 times the rate for non-fire weeks, adjusted for temperature, relative humidity, patient age, and total patient volume at the clinics for pediatric patients. The adjusted rate ratios for itch clinic visits during the wildfire weeks were 1.82 for the pediatric patients and 1.29 for adult patients.

A 10-microgram/m3 increase in weekly mean PM2.5 concentration was associated with a 7.7% increase in weekly pediatric itch clinic visits.

The adjusted rate ratio for prescribed systemic medications in adults during the Camp Fire was 1.45 compared to previous years.

"It is interesting to see a novel health outcome linked to wildfire smoke exposure," said Joan Casey, assistant professor Environmental Health Sciences at Columbia University Mailman School of Public Health in New York City. "The relationship seems plausible since we know wildfire smoke contains a host of toxic particles that might increase inflammation in the human body."

Still, "the authors compare visits during the Camp Fire to those in prior years, which does not take into account any temporal trends in AD or itch visits, meaning AD or itch visits may have increased over time making it appear that they increased during the wildfire when they actually did not," Casey said in an email, adding that this is less likely because of the way the researchers analyzed the data.

"Future studies may wish to account for indoor air filtration status on this effect," Casey said. "I also wonder if any of this occurs through a stress pathway."

SOURCE: https://bit.ly/3ekTFLQ and https://bit.ly/3atySod JAMA Dermatology, online April 21, 2021.

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