Climate Change: Dermatologists Address Impact on Health, and Mobilize to Increase Awareness

Christine Kilgore

March 19, 2021

Climate change will increasingly affect the distribution and frequency of insect-borne diseases, cutaneous leishmaniasis, skin cancer, fungal diseases, and a host of other illnesses that have cutaneous manifestations or involve the skin — and dermatologists are being urged to be ready to diagnose clinical findings, counsel patients about risk mitigation, and decrease the carbon footprint of their practices and medical organizations.

"Climate change is not a far-off threat but an urgent health issue," Misha Rosenbach, MD, associate professor of dermatology at the University of Pennsylvania, Philadelphia, wrote in an editorial with coauthor Mary Sun, a student at Icahn School of Medicine at Mount Sinai, New York. It was first published online in the British Journal of Dermatology last year, titled, "The climate emergency: Why should dermatologists care and how can they act?"

Rosenbach is a founder and leader of the American Academy of Dermatology Expert Resource Group (ERG) for Climate Change and Environmental Issues, established 2 years ago. Some of the 150-plus members of the ERG have been writing about the dermatologic impacts of climate change — including content that filled the January issue of the International Journal of Women's Dermatology — and speaking about the issues.

A session at the AAD's virtual annual meeting in April will address climate change and dermatology – the second such session at an annual meeting — and the first two of three planned virtual symposia led by Rosenbach and his colleagues, have been hosted by the Association of Professors of Dermatology. The ERG encouraged the AAD's adoption of a position statement in 2018 about climate change and dermatology and its membership in the Medical Society Consortium on Climate and Health.

"There's been a lot of conversation in the medical community about the health effects of climate change, but most people leave out the skin," said Mary L. Williams, MD, clinical professor of dermatology at the University of California, San Francisco, who is a cofounder and coleader with Rosenbach of the climate change ERG.

"That's interesting because the skin is the most environmental of all our organs. Of course it will be impacted by all that's going on," she said. "We want to bring the dermatologic community and the wider medical community along with us [in appreciating and acting on this knowledge]."

Changing Disease Patterns

Rosenbach did not think much about how climate change could affect his patients and his clinical practice until he saw a severe case of hand, foot, and mouth disease in a hospitalized adult in Philadelphia about 10 years ago.

A presentation of the case at an infectious disease conference spurred discussion of how the preceding winters had been warmer and of correlations reported by researchers in China between the incidence of hand, foot, and mouth disease – historically a mild infection in children — and average temperature and other meteorological factors. "I knew about climate change, but I never knew we'd see different diseases in our clinical practice, or old diseases affecting new hosts," Rosenbach said in an interview.

He pored over the literature to deepen his understanding of climate change science and the impact of climate change on medicine, and found an "emerging focus" on climate change in some medical journals, but "very little in dermatology." In collaboration with Benjamin Kaffenberger, MD, a dermatologist at The Ohio State University, and colleagues, including an entomologist, Rosenbach wrote a review of publications relating to climate change and skin disease in North America.

Published in 2017 in the Journal of the American Academy of Dermatology, the review details how bacteria, viruses, fungi, and parasites are responding to changing weather patterns in North America, and why dermatologists should be able to recognize changing patterns of disease. Globalization plays a role in changing disease and vector patterns, but "climate change allows expansion of the natural range of pathogens, hosts, reservoirs, and vectors that allow diseases to appear in immunologically naive populations," they wrote.

Patterns of infectious diseases with cutaneous manifestations are already changing. The geographic range of coccidioidomycosis, or valley fever, for instance, "has basically doubled in the Southwest U.S., extending up the entire West Coast," Rosenbach said, as the result of longer dry seasons and more frequent wind storms that aerosolize the mycosis-causing, soil-dwelling fungal spores.

Lyme disease and associated tick-borne infections continue to expand northward as Ixodes tick vectors move and breed "exactly in sync with a warming world," Rosenbach said. "We're seeing Lyme in Philadelphia in February, whereas in the past we may not have seen it until May...There are derms in Maine [whose patients have Lyme disease] who may never have seen a case before, and derms in Canada who are making diagnoses of Lyme [for the first time]."

And locally acquired cases of dengue are being reported in Hawaii, Texas, and Florida — and even North Carolina, according to a review of infectious diseases with cutaneous manifestations in the issue of the International Journal of Women's Dermatology dedicated to climate change. As with Ixodes ticks, which transmit Lyme disease, rising temperatures lead to longer breeding seasons for Aedes mosquitoes, which transmit dengue. Increased endemicity of dengue is concerning because severe illness is significantly more likely in individuals previously infected with a different serotype.

"Dermatologists should be ready to identify and diagnose these mosquito-borne diseases that we think of as occurring in Central America or tropical regions," Rosenbach said. "In my children's lifetime there will be tropical diseases in New York, Philadelphia, Boston and other such places."

In his articles and talks, Rosenbach lays out the science of climate change — for instance, the change in average global temperatures above preindustrial levels (an approximate 1° C rise) , the threshold beyond which the Earth will become less hospitable (1.5° C of warming according to United Nation's Intergovernmental Panel on Climate Change), the current projections for future warming (an increase of about 3° Celsius by 2100), and the "gold-standard" level of scientific certainty that climate change is human-caused.

Mathematical climate modeling, he emphasized in the interview, can accurately project changes in infection rates. Researchers predicted 10 years ago in a published paper, for instance, that based on global warming patterns, the sand fly vector responsible for cutaneous leishmaniasis would live in the Southern United States and cause endemic infections within 10 years.

And in 2018, Rosenbach said, a paper in JAMA Dermatology described how more than half — 59% — of the cases of cutaneous leishmaniasis diagnosed in Texas were endemic, all occurring in people with no prior travel outside the United States.

Williams' devotion to climate change and dermatology and to the climate change ERG was inspired in large part by Rosenbach's 2017 paper in JAAD. She had long been concerned about climate change, she said, but "the review article was really the impetus for me to think, this is really within my specialty."

Extreme weather events, and the climate-driven migration expected to increasingly occur, have clear relevance to dermatology, Williams said. "Often, the most vexing problems that people have when they're forced out of their homes...are dermatologic," she said, like infections from contaminated waters after flooding and the spread of scabies and other communicable diseases due to crowding and unsanitary conditions.

But there are other less obvious ramifications of a changing climate that affect dermatology. Williams has delved into the literature on heat-related illness, for instance, and found that most research has been in the realm of sports medicine and military health. "Most of us don't treat serious heat-related illnesses, but our skin is responsible for keeping us cool and there's an important role for dermatologists to play in knowing how the skin does that and who is at risk for heat illness because the skin is unable to do the full job," she said.

Research is needed to identify which medications can interfere with the skin's thermoregulatory responses and put patients at risk, she noted. "And a lot of the work on sweat gland physiology is probably 30 years old now. We should bring to bear contemporary research techniques."

Dermatology is also "in the early stages of understanding the role that air pollution plays in skin disease," Williams said. "Most of the medical literature focuses on the effects of pollution on the lungs and in cardiovascular disease."

There is evidence linking small particulate matter found in wood smoke and other air pollutants to exacerbations of atopic dermatitis and other inflammatory skin conditions, she noted, but mechanisms need to be explored and health disparities examined. "While we know that there are health disparities in terms of [exposure to] pollution and respiratory illness, we have no idea if this is the case with our skin diseases like atopic dermatitis," said Williams.

In general, according to the AAD position statement, low-income and minority communities, in addition to the very young and the very old, "are and will continue to be disproportionately affected by climate change."

Education and the Carbon Footprint

Viewing climate change as a social determinant of health (SDH ) – and integrating it into medical training as such – is a topic of active discussion. At UCSF, Sarah J. Coates, MD, a fellow in pediatric dermatology, is working with colleagues to integrate climate change into formal resident education. "We know that climate change affects housing, food security, migration ... and certain populations are and will be especially vulnerable," she said in an interview. "The effects of climate change fit squarely into the social determinant of health curriculum that we're building here."

Coates began to appreciate the link between climate and infectious diseases — a topic she now writes and speaks about — when she saw several patients with coccidioidomycosis as a dermatology resident at UCSF and learned that the cases represented an epidemic in the Central Valley "resulting from several years of drought."

Her medical school and residency training were otherwise devoid of any discussion of climate change. At UCSF and nearby Stanford (Calif.) University, this is no longer the case, she and Williams said. "The medical students here have been quite active and are requesting education," noted Williams. "The desire to know more is coming from the bottom."

Mary E. Maloney, MD, professor of medicine and director of dermatologic surgery at the University of Massachusetts, Worcester, sees the same interest from physicians-in-training in the Boston area. They want education about climate science, the impact of climate changes on health and risk mitigation, and ways to reduce medicine's carbon footprint. "We need to teach them and charge them to lead in their communities," she said in an interview.

Maloney joined the AAD's climate change resource group soon after its inception, having realized the urgency of climate change and feeling that she needed "to get passionate and not just do small things." As a Mohs surgeon, she expects an "explosion" of skin cancer as temperatures and sun exposure continue to increase.

She urges dermatologists to work to decrease the carbon footprint of their practices and to advocate for local hospitals and other clinical institutions to do so. On the AAD website, members now have free access to tools provided by the nonprofit organization My Green Doctor for outpatient offices to lighten their carbon footprints in a cost-effective — or even cost-saving — manner.

Maloney's institution has moved to automated lighting systems and the use of LED lights, she said, and has encouraged ride sharing (prior to the pandemic) and computer switch-offs at night. And in her practice, she and a colleague have been working to reduce the purchasing and use of disposable plastics.

Educating patients about the effects of climate change on the health of their skin is another of the missions listed in the AAD's position statement, and it's something that Coates is currently researching. "It seems similar to talking about other social determinants of health," she said. "Saying to a patient, for instance, 'we've had some really terrible wildfires lately. They're getting worse as the seasons go on and we know that's because of climate change. How do you think your current rash relates to the current air quality? How you think the air quality affects your skin?' "

Rosenbach emphasizes that physicians are a broadly trusted group. "I'd tell a patient, 'you're the fourth patient I've seen with Lyme — we think that's because it's been a warmer year due to climate change,' " he said. "I don't think that bringing up climate change has ever been a source of friction."

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