Image of a mosquitoWhat are the health implications?


Climate change currently contributes to the global burden of disease and premature deaths. [see reference 35] It has been estimated that the modest climate change that occurred between the mid-1970s and 2000 caused the loss of over 150,000 lives and 5.5 million disability adjusted life years (DALYs) per year. [see reference 36] With the estimated current and projected future impacts of climate change on human health, this global burden of death and DALY is predicted to increase in the future, most noticeably in developing countries. [see reference 36] The main ways that climate change can affect the health of a population are outlined in Figure 4.

Figure 4: Schematic summary of main pathways by which climate change affects population health
Figure 4: Schematic summary of main pathways by which climate change affects population health































Source: McMichael AJ, Woodruff RE & Hales S (2006) Climate change and human health: present and future risks. The Lancet 367: 859-869, with permission from Elsevier.

There are a range of health consequences for the UK as a result of climate change and these are outlined below. Existing health inequalities are also likely to be exacerbated as a result of health impacts related to climate change. In general, health and life expectancy are strongly linked to social circumstances and childhood poverty. [see reference 37] Those at the lower end of the economic or social scale tend to be less healthy and to have poorer access to healthcare.

In addressing the health implications of climate change in the UK, it is important to note that in many cases these impacts are based on projections of how the climate will change in the future.

Increased temperatures
Increased temperatures and heat waves can have acute consequences for health. The greatest impact may be witnessed among the elderly, babies and children, and people with ill-health including those with mental health problems. Heatwaves and an increase in temperature can result in dehydration, heat exhaustion or heat stroke. This in turn can lead to irreversible damage to various organs and even death. The increased frequency and severity of heatwaves that is predicted in the future for the UK, could result in a rise in heat-related deaths. [see reference 5] If temperatures continue to rise, they may, however, be a reduction in cold-related mortality in the long term.

A recent example of the consequences of increased temperatures is the 2003 heat wave that affected much of Western Europe, including the UK. The heatwave was estimated to have caused around 2,000 extra deaths in England and Wales. [see reference 38] The impact was greatest in the southern half of England and among the elderly. While it is predicted that the population of the UK will become more tolerant to hotter temperatures in the future, [see reference 5] the increased frequency and severity of heatwaves will be of major concern, as the effect of several hot days in a row is much greater than the effect of the same number of separate hot days. [see reference 5]

Flooding
The health impacts of flooding are complex and far-reaching. Potential health outcomes from flooding include: direct mortality and morbidity, chemical hazards and contamination, infectious diseases, effect of flooding on health service delivery and effects on mental health. [see references 5, 39, 40 and 41]

There are relatively few deaths associated with flooding in the UK when compared to other European countries. [see reference 5] Injuries may be more common and can result from an individuals’ attempt to avoid the flood and/or remove possessions or other people away from the flood waters. Flooding can also disrupt essentials including communications and power supplies, potentially leading to impacts on health and health service delivery. In July 2007, for example, rising floodwaters from the river Severn severely threatened power supplies in southern England as flood waters enclosed Gloucestershire's main electricity sub-station, at Walham near Gloucester. A particular concern is the fact that many hospitals in the UK have their generators situated in the basement. Water treatment plants can also be directly affected by flooding, leading to a loss of availability of clean water.

Contamination of flood waters with substances including chemical waste, oil, pesticides and fertilisers and raw or inadequately treated human or animal sewage/effluent can have impacts on health. [see reference 5] Flooding may also lead to the mobilisation of dangerous chemicals from storage or the remobilisation of chemicals already in the environment. [see references 5 and 42] Hazards may be greater when the affected industrial or agricultural land is next to residential land. This is potentially significant for the UK as there are high population densities close to industrial areas. [see reference 5]

Infectious diseases
Higher temperatures, heavier rainfall and changes in climate variability may increase the spread of infections and present a considerable health challenge due to rising morbidity and mortality. Modes of infection transmission include:
  • Vector-borne infection
    Vector-borne infections are spread by insects, usually on a vertebrate host. The main factors that would affect the distribution and transmission of vector-borne infections are changes in temperature, humidity and precipitation, and increased instances of flooding. [see references 35, 42 and 43] At present, vector-borne diseases, with the exception of Lyme disease, are of minimal concern to health in the UK. [see reference 43]
    Occurrences of vector-borne infections have the potential to increase in the UK as changes in climate provide an environment more amenable to the vertebrate host and the vector itself. Malaria was previously endemic in the UK. A study by Kuhn et al (2003) looking at temporal trends in malaria in Britain between 1840 and 1910 showed that past decreases in Malaria were due to decreasing marsh wetlands and increasing cattle densities. [see reference 44] It is possible that there may be future malaria outbreaks in the UK resulting from changes to factors such as temperature, humidity, precipitation or levels of flooding. It is predicted however, that changes will most likely be rare and occur on a small scale. [see reference 5]
  • Water-borne infection
    Climate change can impact on the epidemiology of water-borne infections in three main ways: through heavy precipitation events, flooding events and increased temperatures. [see reference 43] A rise in the occurrence of heavy precipitation events could lead to increased surface water turbidity and greater levels of indicator bacteria and pathogens in surface water. [see reference 5] As a result of increased temperatures, there could potentially be a rise in the number of cyanobacterial blooms (excessive growth and congregation of cyanobacteria that accumulate on the surface of slow-moving waters) due to increased water temperature and nutrient concentration. [see references 5 and 43]
    It is unlikely that climate change will have a significant effect on the risk of water-borne infections in the UK. The UK’s water treatment and distribution is of a very high standard. There could potentially be an impact on private water supplies (which are often poorly treated), surface water supplies without filtration and groundwater supplies. [see references 5 and 43]
  • Food-borne infection
    Instances of food-borne infection have been shown to rise with warmer temperatures [see reference 45] and the occurrence of salmonellosis is affected by temperature. [see references 46 and 47] While it is estimated that climate change will potentially influence increases in food-borne infection, the consequences that an increase of temperature will have on food-borne infection will depend on factors such as future food hygiene behaviour and contributions of different pathogens. [see reference 5]
Ultraviolet radiation
Climate change can affect human exposure to ultraviolet radiation (UVR) in different ways; however, this is difficult to predict and is dependent on location and current exposure to UVR. Ways that climate change can affect UVR include through altering cloud distribution, which then affects UVR surface levels, and an increase in temperatures influencing human behaviour such as time spent in the sun and clothing choices. [see reference 35] The main health impact of UV radiation would be to increase the risk of skin cancers. [see reference 5 and 35] Other possible health effects would be an increased potential for sunburn and sunstroke, and a rise in the occurrence of cataracts, which is one of the main causes of treatable blindness. [see reference 8]

Air pollution
Air pollution has significant effects on human health, including contributing to respiratory infection. Concentrations of air pollutants and fine particulate matter may change as a result of climate change, as their formation partly relies on temperature and humidity. [see reference 35] Ground level ozone for example, although naturally occurring, is a principal element of urban smog and the chemical reactions that produce ground level ozone are temperature dependent. [see reference 35] Exposure to elevated levels of ground level ozone could lead to an increase cardio-respiratory morbidity and mortality. [see reference 35] The impact of ground level ozone increases could also result in a 15-53 per cent increase in deaths and hospital admissions in the UK from respiratory infections related to air pollution each year. [see reference 5]

Mental health
Traumatic weather events, such as flooding, can have serious implications for mental health, including increased anxiety and depression, especially in the elderly. In Lewes, East Sussex, for example, a flood in 2000 affected a number of homes and businesses. It was found that people whose homes were affected, experienced a four-fold increase in psychological distress when compared to those whose homes were not affected. [see reference 48] Concerns over insurance and the recurrence of traumatic weather events can also impact on mental well-being.

Health inter-linkages
There are a number of links between climate change and other health problems. Climate change policies that target the reduction of GHG emissions could contribute to reducing the risks of cancer, heart disease, obesity, diabetes, air pollution, road traffic injuries and osteoporosis. [see reference 49]

Obesity for example, is exacerbated through car dependence and the lack of walking and cycling. Reducing car use will equate to a reduction in CO2 emissions, result in increased levels of physical activity and could also lead to a reduction in accidents through safer roads and public spaces. Food production is another example, as livestock rearing for meat and dairy is a significant contributor to emissions, through CH4 from enteric fermentation and CO2 from land clearance for farming. [see reference 50] Through a reduction in consumption of these animal products; not only can emissions be reduced but also the amount of saturated fat and meat in the diet, resulting in predicted health benefits. [see reference 50]

(See section ‘Recommendations: what can health professionals do?’ for information on ways that health professionals can take direct action on climate change and encourage healthy lifestyles).

Further sources of information:

© British Medical Association 2008

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