Geoscience Reference
In-Depth Information
sunlight-induced vitamin D. Further, sunlight-induced skin cancers are the common-
est form of cancer among light-skinned populations: for example, they account for
an estimated 70% of all skin cancers in the USA. Exposure to sunlight is the major
environmental cause of these cancers. The least frequent, but most serious, of the
three skin cancer types is malignant melanoma. If not detected and treated early, this
cancer will spread via the bloodstream to internal organs and this is often fatal, with
mortality of around 25% (McMichael, 1993). In the UK the Department of Health
assessment is that by 2050 there will be a possible 5000 extra cases of skin cancer a
year due to climate change (Department of Health, 2002).
UV light also damages the eyes in a variety of ways, which include encouraging
cataract formation. The Department of Health estimate an increase of some 2000
cataract cases a year by 2050 (Department of Health, 2002). In its second Health
Effects of Climate Change assessment (an update of the 2002 report but jointly
published with the Health Protection Agency; Department of Health and the Health
Protection Agency, 2008) the warnings about UV radiation were strengthened but it
also noted that quantitative estimates remain elusive.
As with the extreme cold events discussed above, the health effect of increased
surface UV light on a population is strongly affected by behaviour. Avoiding sun-
bathing (and especially by avoiding sunburn) greatly reduces risks, although not
sunbathing does not eliminate risk because skin exposure to UV radiation takes place
outdoors on nearly all uncovered parts of the body. Wearing glasses with glass lenses
(as opposed to plastic-lensed glasses transparent to UV radiation) helps reduce the
risk of cataract formation. However, small-lensed, dark sunglasses allow sunlight in
around the rim while the dark lens allows the iris to dilate, so allowing in extra UV
light, even if it is not focused on the fovea of the retina, the most sensitive part of the
visual field. Large-lensed and only slightly tinted sunglasses give the best protection.
(Glass wearers take note when next visiting your optician.)
Extreme hot-weather events can also affect microbial populations and this is dis-
cussed in section 7.3.2. Finally, extreme weather events can also result in flooding
due to rain bursts and the synergies between sea-level rise and storm surges that are
associated with global warming. These too have health impacts and are covered in
section 7.3.3.
7.3.2 Climatechangeanddisease
Pathogens are disease-causing living organisms that are predominantly protoctistans
(single-celled eukaryotes, meaning with internal membranes), prokaryotes (such as
bacteria, which have no internal membranes) and viruses (genetic material - DNA
or RNA - with a protein and/or glycoprotein coat; although there is debate as to
whether viruses should be considered as living). There are also metazoan (multicelled
animal) parasites. The ability of all these to flourish is affected by their environmental
conditions, and hence climate change. Even those pathogens that rely on a vector
(an organism capable of transmitting a disease from host to host) are affected by
climate change, in that the vector itself will flourish best under certain environmental
conditions. In short, just as a species' range and/or population will vary with a
combination of climate change and other environmental factors (Chapter 5 and 6),
 
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