521ISSN 1746-9872© 2011 Expert Reviews Ltdwww.expert-reviews.com

Editorial

10.1586/EDM.11.47

Global warming and its dermatologic impact

“While the myriad consequences of global warming are predicted to affect virtually all walks of life, several aspects pose

particular challenges for dermatology.”

Global surface temperatures rose 0.74 ± 0.18°C during the last century [1]. The last 50 years witnessed almost double the rate of warming of the last 100 years. Over the next century, temperatures are projected to rise several degrees further, depending on the model of climate change followed. While the myriad consequences of global warming are predicted to affect virtually all walks of life, several aspects pose particu-lar challenges for dermatology. Progress on meeting them continues to build.

Climate changes Evidence points to a causal role for anthro-pogenic carbon emissions in the context of global warming. Carbon dioxide and other greenhouse gases such as methane trap solar infrared radiation. The increase in atmospheric concentration of carbon diox-ide has been attributed to human activities such as burning fossil fuels and deforesta-tion. This rising concentration is thought to be the culprit behind the changes in global surface temperatures.

Some of the consequences of this change in global climates may include increased exposure to ultraviolet radiation, a greater severity of extreme weather events and new patterns of disease vectors.

UV effectsEfforts have been made over the years to raise public awareness of the effects of UV radiation. Concerns have focused

on depletion of the ozone layer, as well as social trends such as sunbathing and tanning parlors, but climate change may also affect levels of UV exposure. In addi-tion, rising temperatures may increase the carcino genic effectiveness of UV radiation. As early as the mid-20th Century, studies on mice showed that elevated tempera-tures enhanced UV-induced carcinogen-esis. Studies of humans suggest similar effects, with each °C rise corresponding to an estimated equivalent impact of +2% in effective UV dose [2].

Such effects will be intertwined with those of changing social patterns, from growth in outdoor leisure activities to countervailing trends to remain indoors. Humans have always had a large say in the matter of their own health. But even human behavior, especially in an age of anthropogenic climate change, may prove the greatest determinant of outcomes. Behavior associated with climate change, as Diffey proposed for the UK popula-tion [3,4], may have a larger impact on UV exposure and consequent skin cancer than ozone depletion. In other regions, cli-mate change may compel people to limit their outdoor activities, as predicted by

Expert Rev. Dermatol. 6(5), 521–523 (2011)

Young HuiAuthor for correspondence: University of California, San Franciso, Box 0989, 90 Medical Center Way 110, San Francisco, CA 94143, USA yohui@ucsd.edu

Haw-Yueh ThongUniversity of California, San Diego, CA, USA

Howard I MaibachUniversity of California, San Franciso, CA, USA

Keywords: climate change • dermatology • disease vectors • global warming • UV radiation

GeNerAL CoNTeNT

“The spread of natural disasters has changed the literature on

skin infections.”

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Expert Rev. Dermatol. 6(5), (2011)522

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Maloney and Forbes [5] in Australia, increasing the number of days unsuitable for labor or strenuous exercise.

Extreme weather events Recent years have witnessed many natural disasters, from the Indian Ocean tsunami, to Hurricane Katrina, to the floods in Pakistan and the Mississippi River basin, as well as others too numerous to list. While individually their links to climate change are difficult to parse, collectively they illustrate the impending challenges society and health professionals face from changing weather patterns.

The spread of natural disasters has changed the literature on skin infections. After Hurricane Katrina in 2005, the CDC reported on wound infections with methicillin-resistant Staphylococcus aureus (MRSA), Vibrio vulnificus and Vibrio parahaemolyticus among local residents, and tineacorporis, folliculitis, miliaria and arthropod bites among rescue personnel [6]. Rhoads also reported on cases of V. vulnificus causing problems, including septic shock, for victims [7].

The Indian Ocean tsunami of December 2004 provided the literature with new cases of dermatologic conditions associated with massive flooding. Multidrug-resistant diseases, polymicro-bial infections and other unusual pathogens, such as Burkholderia pseudomallei, Cladophialophora bantiana and Mycobacterium abscessus, were found following exposure to freshwater contami-nated by flooding [8–10]. In another report, Hiransuthikul et al. found that 515 (66.3%) tsunami survivors with traumatic wounds were diagnosed with skin and soft-tissue infections, with the most common isolated being Aeromonas species [11]. Such challenges may become more familiar to dermatologists if these weather trends continue.

Habitats & disease vectors Environmental changes wrought by global warming may alter the patterns of diseases and outbreaks. There will be many factors influencing these changes in disease dynamics, such as globaliza-tion and demographic shifts; climate change may prove one of the largest.

As climates warm, diseases previously confined to lowlands and the tropics may move into higher elevations and more north-ern latitudes [12]. An example among animals is the fate of the Monteverde harlequin frog (Atelopus spp.), which fell extinct after an outbreak of the pathogenic chytrid fungus Batrachochytrium, which had expanded its range into the highlands after tempera-tures warmed [13]. Humans may be susceptible to similar outbreaks as Staphylococcus, Streptococcus and enteric bacteria, for example,

fare better in warmer climes [14,15]. McBride et al. found that high temperatures and humidity increased the overall frequency of isolation of Gram-negative bacteria, though with individual differences [16]. Treating outbreaks of such diseases, potentially resistant to antimicrobials, will be a test for dermatologists.

Various authors have explored the potential effects of climate change upon vector-borne diseases such as malaria, dengue, leish-maniasis and tick-borne diseases [17–20]. As an example of the relationships between vector-borne diseases and climate variation, Cárdenas et al. [21] report on the impact of the El Nino Southern Oscillation on the incidences of leishmaniasis in Columbia from 1985 to 2002, which show an increase during El Nino and decrease during La Nina phases [16]. However, the existing literature may not present sufficient evidence to support a casual relationship between global warming and increased incidence for all vector-borne dis-eases; in the case of tick-borne diseases, Randolph argued that climate change had not been proven to be the cause of the increases in such cases, despite the susceptibility of such systems to climate changes [22]. As is often the case, more research is necessary; what distinguishes climate change is the impact knowlede may have.

Challenges & skin bacteriologyAdapting to the demands of climate change appears an increas-ingly imposing task. It seems likely that our existing arsenal of tools will require bolstering. Dermatology will need to advance to meet the challenge of treating the largest human organ, in knowledge and practice.

For example, the skin, like the GI tract, is heavily colonized. Recently, dermatologists have learned to appreciate the complex-ity of this biota and improve their investigations [23]. Such new molecular identification tools, still in their infancy, should pro-vide fertile insights into the role of microbes in health and dis-ease. The implications as they relate to climate control mandate detailed investigation.

Contemplating the future Considering the breadth of these tasks, their solutions demand collective action (Table 1). With millions of species potentially facing extinction, the challenges facing scientists and mod-ern medicine over the next century are a serious matter [24]. Acknowledgement of the challenges posed has been growing among health professionals [25–28].

Dermatologists will need every tool at their disposal to face the task of caring for patients and preparing society for the coming demands.

Table 1. Potential dermatologic consequences of climate change.

Changes Effects Ref.

Physical Rise of several degrees Celsius,greater UV exposure

Higher incidence of skin cancer [1,2]

Weather Higher frequency and severity of tropical storms, more flooding

More cases of skin infection [6–11]

Environment Shifting biomes Expanded range of tropical diseases,altered patterns of disease vectors

[12,13,16,18–22,24,25]

Hui, Thong & Maibach

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19 Bormane A, Lucenko I, Duks A et al. Vectors of tick-borne diseases and epidemiological situation in Latvia in 1993–2002. Int. J. Med. Microbiol. 293(Suppl. 37), 36–47 (2004).

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21 Cárdenas R, Sandoval CM, Rodriguez-Morales AJ, Franco-Paredes C. Impact of climate variability in the occurrence of leishmaniasis in northeastern Colombia. Am. J. Trop. Med. Hygiene 75(2), 273–277 (2006).

22 Randolph SE. Evidence that climate change has caused ‘emergence’ of tick-borne diseases in Europe? Int. J. Med. Microbiol. 293(Suppl. 37), 5–15 (2004).

23 Scharschmidt TC, List K, Grice EA et al. Matriptase-deficient mice exhibit ichthyotic skin with a selective shift in skin Microbiota. J. Invest. Dermatol. 129(10), 2435–2442 (2009).

24 Thomas CD, Cameron A, Green RE et al. Extinction risk from climate change. Nature 427(6970), 145–148 (2004).

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26 Grover S, Rajeshwari. Global warming and its impact on skin disorders. Indian J. Dermatol. Venereol. Leprology 75(4), 337–339 (2009).

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28 Andersen LK. Global climate change and its dermatological diseases. Int. J. Dermatol. 50(5), 601–603 (2011).

Financial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes

employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Global warming & its dermatologic impact

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