Wednesday, February 15, 2017

Skin Disease and Climate Change...Thinking Beyond the Ozone Layer

A few months ago, I had a patient ask me how global warming had affected the number of skin cancers I saw.  I hadn't considered the question before, but I did mention that a warmer temperature by itself did not mean that more UV rays reach the earth. I did mention that thinning of the ozone layer, particularly in Australia, had played a role in increasing skin cancer rates. 

With this patient's question in mind, I read with interest an article by Kaffenberger et al. from the January 2017 edition of the Journal of the American Academy of Dermatology about how global warming could affect skin disease in North America. Since I can't remember which of my patients asked the question, I'm posting a quick review of the article here and hoping said patient is tuned in to my blog. 

If hurricanes, tornadoes, and floods were not enough to scare you, the expanded footprint of bacteria, viruses, and fungi that might occur with a warmer climate will.  Lyme disease may expand further into Canada.  It has already increased from an estimated 10,000 cases per year in 1995 to 30,000 cases per year in 2012 based on the larger range of habitat for the tick that carries it and the range of the tick's preferred hosts.  The fungal disease coccidioidomycosis usually occurs in arid areas like Arizona but has recently occurred as far north as Washington state.  The parasitic disease leishmaniasis usually occurs in Mexico, but the disease's rodent reservoir and its vector the sandfly are expected to bring the disease further north as the temperature rises.  Finally hand, foot, and mouth disease, a common virus well known to parents of young children, will likely see an increase in incidence with more temperate climates. 

Diseases that are rare in the United States and more common to tropical climates will start to move into the southern states.  Dengue, chikungunya, and Zika virus are all transmitted by a mosquito that was originally native to Africa and Asia and is now present throughout North America.  Dengue fever has already been reported in Texas and Florida.  Increased rainfall and flooding will provide even more breeding ground for the mosquitos that carry these important tropical diseases and could make these diseases harder to control. 

Skin cancer will continue to be a problem as ozone is depleted. The second question is whether the weather will affect human behavior with regard to sun exposure.  A two degree increase in temperature may increase skin cancer by 10% according to some authors, mainly because higher temperatures tend to lead people to spend more time outdoors. 

I write this post as a doctor to make my patients more aware of what health concerns we face together.  We must be aware as a population that sunscreen and sun protective behavior are not optional as we spend more time in the sun with less ozone to protect us.  We should have a healthy respect for the tropical diseases that creep our way and commit to being aware of the spread of these diseases as they occur.  It seems that mosquito and tick bite prevention will become more important for our everyday lives. 

I also write this article as a citizen with concern for our policy making with regards to the environment.  I hope that we can raise awareness of global warming as one of the critical issues facing our nation and our planet. 

For more details, please reference:
The effect of climate change on skin disease in North America. 
Kaffenberger BH, Shetlar D, Norton SA, Rosenbach M.
J Am Acad Dermatol. 2017 Jan;76(1):140-147

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