Author: Dr Kirsten Due, General Practitioner, South Australia, Australia. Reviewed by Greg Miles, former Kakadu Chief Ranger and Park Naturalist, Northern Territory, Australia. DermNet New Zealand Editor in Chief: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. December 2017.
Climate change is a lasting alteration in patterns of weather caused by factors such as oceanic circulation, variations in solar radiation, plate tectonics, volcanic eruptions, and human factors. These may impact global or local temperature, humidity, rainfall, and weather extremes.
Colloquial use of the term “climate change” specifically refers to environmental changes caused by human factors, including global warming due to the production of gases that may trap heat in the atmosphere — carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluorinated gases.
Climate change has been called a “risk-multiplier” rather than a risk-generator or risk factor, due to it worsening pre-existing climate-related health concerns.
Climate influences a wide range of systemic diseases and conditions. Heat exposure, a combination of air temperature, humidity, air movement and heat radiation, can present an environmental hazard. The most common measures used to describe heat stress are the wet bulb globe temperature (WBGT), and universal thermal climate index (UTCI). A WBGT of 29 degrees has been shown to reduce work performance and to cause a wide variety of respiratory, cardiac and gastrointestinal diseases.
As skin is exposed to the environment, it is especially vulnerable to increased heat and humidity. In this article, we describe the effects of a warmer environment on cutaneous infections and inflammatory diseases of the skin.
Warmer conditions lead to a greater prevalence of cutaneous infections, including:
One study showed that for every 1°C rise in average temperature, the rate of hand foot and mouth disease increased by 10% and for every 1% increase in relative humidity (under 65%) the rate increased by 6.6%.
Mosquitoes, ticks, and fleas are vectors that carry pathogenic viruses, bacteria, and protozoa, which can be transferred from one host (for example a mosquito) to another (for example a person or animal). Temperature plays an important role in the spread of vectors and vector borne disease. Warmer conditions lead to faster replication of certain viruses and vectors and increased rates of transmission.
Heavy rainfall and flooding often leads to outbreaks of waterborne disease, which are predicted to increase with climate change. Water sources may undergo increased contamination from flooding or become stagnant from drought. Flooding causes disease to spread as people move en masse to seek dry ground.
Climate factors have been identified as important in outbreaks of the following waterborne diseases:
Flooding and droughts may lead to lack of fresh water for washing and cooking, especially in resource-poor nations. Warmer waters can cause outbreaks of shellfish-borne disease, such as Vibrio parahaemolyticus.
Increases in temperature and humidity cause food to decay and thus increased consumption of mycotoxins, which are metabolites of moulds. Mycotoxins may also cause disease by penetrating through the skin.
Phycotoxins are potent natural toxins produced by some marine algae and cyanobacteria species. Outbreaks or algal blooms are often colloquially known as as “red tides” or “green tides”. Seafood intended for human consumption can be contaminated in massive quantities.
Warmer climate and hot surfaces, bushfires and building fires may lead to thermal burns.
Measured levels of ultraviolet radiation are mainly independent of heat and humidity. However, higher outdoor temperatures in previously temperate climates might result in people wearing less clothing and spending longer periods outdoors, and thus increase exposure of the skin to ultraviolet (UV) radiation.
UV damage includes:
Better early warning systems and prediction tools would enable prevention and management of disease epidemics — including those affecting the skin.
Barriers to making long term epidemiological assessments and projections include:
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