Climate change may have an impact on health in several ways, both directly (through temperature e.g.) and indirectly. Health impacts are: cold and heat stress, skin cancer, food poisoning, toxic algae blooms, tick-borne and (other) vector-borne diseases.water-borne diseases, air quality, and leaching of pollutants.
According to health-impact assessments of climate change in Europe, carried out by several countries, projected trends in climate-change-related exposures of importance to human health are likely to (30):
- increase heat-wave-related health impacts;
- continue cold-related health effects in particular in populations with lack of access to continuous energy;
- increase flood-related health impacts;
- increase malnutrition in areas already affected;
- change food-borne disease patterns;
- change the distribution of infectious diseases and potentially contribute to the establishment of tropical and subtropical species;
- increase the burden of water-borne diseases, in populations where water, sanitation and personal hygiene standards are already low; and
- increase the frequency of respiratory diseases due to higher concentrations of ground-level ozone concentrations in urban areas and changes in pollen distribution related to climate change
Cold stress
Of the roughly 70,000 deaths in London every year, about 6,000 more occur during the winter than would be expected from the rate during the rest of year (27). Another publication reports that in London 3,000 pensioners died of cold-related illnesses in the winter of 2004/05 (38). There is some evidence to link this to cold homes and age. Countries with much colder winter climates, but higher standards of heating and insulation (e.g. Sweden) have much lower excess winter death rates (27). Excess winter deaths (EWDs) are causally attributed to seasonal variations in temperature, with low temperatures thought to cause death directly (for example, through hypothermia or falls in icy conditions) and by altering vulnerability to communicable or non-communicable diseases, such as influenza and myocardial infarction, which are more common in winter (62).
Decrease of winter mortality due to climate change?
The Department of Health suggests that up to 20,000 fewer deaths might occur in the UK as a whole as a consequence of medium-high climate change by the 2050s (2). In the United Kingdom, annual cold-related deaths are expected to decrease from about 80,300 in the 1990s to about 60,000 in the 2050s and 51,200 in the 2080s in this scenario (27).
Warmer winters would decrease the death toll from cold temperatures in poorly insulated homes. This benefit is expected to outweigh the increase in deaths from heat stress up to the 2050s (3). Anthropogenic climate change is projected to increase heat-related mortality and decrease cold- related mortality, with an overall net increase in total mortality rates (67).
Most European countries have between 5 and 30 % higher death rates in winter than in summer. Winter‑related mortality in many European populations has declined since the 1950s (25). Cold days, cold nights and frost days have become rarer, but explain only a small part of this reduction: improved home heating, better general health and improved prevention and treatment of winter infections have played a more significant role (26).
Increase of winter mortality due to climate change?
A recent analysis of data over the past 60 years for England and Wales has shown that the link between winter temperatures and excess winter deaths (EWDs) may no longer be as strong as before and that how harsh a winter is no longer predicts how many EWDs there will be (63). It was concluded that the association of year-to-year variation in EWDs with the number of cold days in winter (<5°C), evident until the mid 1970s, has disappeared, leaving only the incidence of influenza-like illnesses to explain any of the year-to-year variation in EWDs in the past decade. This was related to better housing, improved health care, higher incomes and greater awareness of the risks of cold over the past few decades.
The researchers who carried out this analysis state that many of the papers that concluded that climate change would lead to fewer EWDs are not recent and rely on relatively old data. According to them the correlation between the number of cold winter days per year and EWDs, which was strong until the mid 1970s, no longer exists. In addition, they conclude that no evidence exists that EWDs in England and Wales will fall if winters warm with climate change. Instead, the absolute number of EWDs may increase in the coming decades due to an increase in future winter temperature volatility and because of a growing and ageing population (63).
Heat stress
Heat waves combined with urban heat islands (43) can result in large death tolls with the elderly, the unwell, the socially isolated, and outdoor workers (44) being especially vulnerable. Heat waves thus pose a future challenge for major cities (45).
86,000 extra deaths per year in EU countries have been estimated with a global mean temperature increase of 3 degrees C in 2071–2100 relative to 1961–1990 (31). Increasing numbers of older adults in the population will increase the proportion of the population at risk.
For the recent past the localities with higher heat hazards, higher levels of socio-economic vulnerability and therefore higher heat risk are in London, eastern England, particularly East Anglia and around The Wash, and coastal regions along the southern coasts of England from Kent to the Isle of Wight. Regions in the southeast of the UK will continue to be most exposed in the future, under mean annual global warming levels of +1.5°C, +2.0°C and +3.0°C above pre-industrial levels. However, other regions, particularly in the west and southwest, show slightly greater projected increases in heat hazard metrics (73).
In the United Kingdom, annual heat-related deaths are expected to increase from about 800 in the 1990s to about 2800 in the 2050s and about 3500 in the 2080s in the medium‑high scenario (27). The Department of Health’s recent review of the impacts of climate change suggests that approximately 2000 extra deaths might result from higher summer temperatures in the UK as a whole (2). The effects of warm temperature on mortality from cardiorespiratory causes may not be the same from one part of the country to another, however. This was concluded from a study where these heat stress effects were quantified for all 376 local authority districts in England and Wales for the period 2001-2010 (64). It was shown that in the most vulnerable districts, those in London and south/southeast England, odds of dying from cardiorespiratory causes increased by more than 10% for 1°C warmer temperature, compared with virtually no effect in the most resilient districts in the far north.
Populations do, however, adapt to continued higher temperatures through behavioural change and through autonomous physiological change. For this reason, populations are most often vulnerable to unusually hot or cold weather, relative to what they are acclimatised to, rather than hot or cold per se. Studies have shown, for instance, that the people of Athens suffer more from a cold weather spell than people in Stockholm do to an equivalent cold spell. On the other hand, the residents of Stockholm are more affected by a heat wave than those in Athens (4).
It has been estimated that the heat waves in 1976 and 1995 were associated with a 15% increase in mortality in greater London (5), and the daily death rate was seen to increase 8-9 % in England and Wales (6). The summer heat wave experienced in 2003 is likely to become a normal event by the 2040s and considered cool by the 2060s (7).
Higher temperatures could lead to deterioration in the working conditions for employees. We may have to modify our workplaces and homes to be more comfortable during hot periods. However, wider spread use of air conditioning could lead to higher energy use with increases in associated emissions (3).
During prolonged periods of hot, dry weather, the intensity of the urban heat island can build up night after night. During the heatwave of 2003, the centre of London was up to 10°C warmer than the surrounding greenbelt (38), and there were over 2,100 excess deaths in England and Wales, with those worst affected being over the age of 75. The impact was greatest in the London region (40). For Glasgow in 2011 a surface urban heat island effect was measured of around 3°C in spring and summer (61). A 2°C warmer summer may result in 1,552 (95% credible interval 1,307–1,762) additional deaths in England and Wales (64).
The hot summer of 2003
As a result of the extreme hot summer of 2003, 44,000 people died in Western Europe. How rare was this extreme event, and what is the human influence on this through anthropogenic climate change?
These questions were answered by carrying out two model experiments: (1) simulations of the year 2003 whereby all known climate forcings are included in the model, (2) simulations of 2003 whereby only natural internal and external forcings are included (i.e. no anthropogenic climate change). To determine whether any human influences contributed to the mortality associated with the 2003 heat wave, mortality for both scenarios (with and without anthropogenic climate change) were compared. This was done for two major European cities: Paris, which recorded unprecedented levels of mortality during the 2003 heat wave, and London, which experienced increased mortality but to a lesser extent than that of Paris (66).
Over the 3-month period June–August 2003, the seasonal heat-related mortality rate was around 34 per 100,000 for Paris and 4.5 per 100,000 for London. It was estimated that human influence was responsible for ∼24 heat related deaths in Paris, and ∼1 in London (per 100,000 population). Anthropogenic climate change increased the risk of heat-related mortality in Central Paris by ∼70% and by ∼20% in London. Out of the estimated ∼315 and ∼735 summer deaths attributed to the heat wave event in Greater London and Central Paris, respectively, 64 (±3) deaths were attributable to anthropogenic climate change in London, and 506 (±51) in Paris.
Without anthropogenic climate change the 2003-like mortality would have been a 1-in-300-year event (±200) for Paris and a 1-in-7-year event (±0.5) for London. Due to climate change this return level has increased to a 1-in-70-year event (±30) for Paris and a 1-in-2.5-year event (±0.2) for London.
The hot summer of 2019
In 2019, a heatwave broke the UK’s highest ever-recorded temperature of 38.7 °C set in 2003. Over 2 heatwaves 892 excess deaths were recorded (69).
Skin cancer
A further impact of hotter weather is the greater risk of skin cancer, especially for children who not only spend more time outside but are also the most vulnerable. The Department of Health (DoH) suggests that 30,000 additional cases of skin cancer per year could occur across the UK if ozone-depleting chemicals are emitted at current levels (5).
For Scotland, on the basis of the climate scenarios, incidence of skin cancer is likely to be affected more by lifestyle changes than as a result of future Scottish climate (8).
Food poisoning
Food poisoning is estimated to increase by 10% increase, or 10,000 more cases per year, for the UK as a whole as increased temperatures facilitate bacterial growth (2,3), though much depends on behavioural change. Studies indicate thatby the 2050s there will be a 5-20% increase in food-borne illness as a result of temperature rise (9). It has been stated that there is considerable under-reporting of its occurrence (10).
Toxic algae blooms
The number of blooms of toxin-producing algae in summer bathing water will increase (5).
Tick-borne diseases
The risks of tick-borne diseases (Lyme Disease and encephalitis) are unlikely to increase according to the DoH review (2). It has been stated, however, that there has been an increase in the incidence of Lyme disease from ticks as a result of milder winters (3). Tick populations are believed to be limited by a very dry period, but can be encouraged by milder winters, so in future there may be an increase in incidence.
Lyme disease is the only important vector-borne disease in the UK and is already prevalent in the South West region. Whilst partly a result of people spending more recreation time outdoors, a positive correlation has also been found between the number of cases of lyme disease and summer temperatures in central England (11). Other researchers state the opposite: a study of reported cases of Lyme disease in the UK showed no correlation with mean summer temperatures (12).
Lyme borreliosis is the most important vector-borne disease in temperate zones of the northern hemisphere in terms of number of cases. In Europe, at least 85,000 cases are reported every year and prevalence is greater eastwards (41,42). The disease is prevalent in Bosnia and Herzegovina, Serbia, and Montenegro. Countries with annual incidences of over 20 per 100,000 include Lithuania, Estonia, Slovenia, Bulgaria, and the Czech Republic (41).
It does seem likely that a warmer climate would encourage changes in human behaviour (more outdoor leisure activities in tick-infested areas, lighter-weight clothing) that could increase risk (13).
Mosquito-borne diseases
Malaria was endemic to the UK until the early part of the last century (14). In the scientific literature different views on the possible spread of malaria in the future are presented. Some state that there is a possibility of malaria outbreaks in the UK by 2050 (3). It has been found that efficient vectors of malaria could carry a strain from Eastern Europe or the Mediterranean – areas which under the WHO’s analysis are very likely to see an increase in the spread of malaria. Recent modelling work shows that the UK would become a suitable home for malarial mosquitoes in the climate anticipated by the 2050s (15). Others, however, state that although increased temperature could lead to climatic conditions favourable to increases in certain vector-borne diseases such as malaria, the infrastructure in the UK would prevent the indigenous spread of malaria (16,28,30,39).
Detecting impacts of climate change on human vector-borne diseases remains difficult, in part, because active mitigations, such as vector-control, antimicrobials, and improved infrastructure can complicate detection of a climate signal (59).
Sand-fly-borne diseases
Leishmaniasis is a protozoan parasitic infection caused by Leishmania infantum that is transmitted to human beings through the bite of an infected female sandfly. Sandfly distribution in Europe is south of latitude 45⁰N and less than 800 m above sea level, although it has recently expanded as high as 49⁰N. Currently, sandfly vectors have a substantially wider range than that of L infantum, and imported cases of infected dogs are common in central and northern Europe. Once conditions make transmission suitable in northern latitudes, these imported cases could act as plentiful source of infections, permitting the development of new endemic foci. Conversely, if climatic conditions become too hot and dry for vector survival, the disease may disappear in southern latitudes. Thus, complex climatic and environmental changes (such as land use) will continue to shift the dispersal of leishmaniasis in Europe (28).
Water-borne diseases
In the UK there has been some 65 recorded outbreaks of infection linked to water affecting 4112 people during the years 1991–2000. Of these outbreaks, 25 were associated with public water supplies, 16 with private water supplies, 23 with swimming pools and one with recreational contact with surface waters (17). By far the commonest reported pathogen was Cryptosporidium, although Campylobacter was the commonest cause of outbreaks associated with private water supplies.
It seems unlikely that global warming will have a major impact on the risk of disease associated with mains water supplies in the UK. The standards of water treatment and distribution within the UK is of a very high standard compared with many nations even elsewhere in Europe. Although outbreaks of waterborne disease do still occur, they are nearly all due to Cryptosporidium and are associated with supplies that are still inadequately treated. Most of these high-risk supplies have been closed (16).
Provided that the UK does not suffer serious economic collapse it is difficult to see how global warming could have a major impact on risk of waterborne disease associated with mains drinking water. On the other hand, there are still many private supplies in use in the UK and these are frequently poorly treated. If heavy rainfall events are to become more common, then the safety of private supplies (already poor) will deteriorate even further (16).
On the other hand, previous episodes of flooding have been associated with an increased risk to human health arising from the spreading of infectious agents from sewage or even food waste onto land (18). Heavy rainfall events may lead to marked decline in microbiological quality of inland and marine recreational waters as a result of heavy runoff. However, the epidemiological evidence of infectious disease associated with recreational water contact is that it is generally very mild and not likely to cause significant disease burden in the population (16).
Air quality
Future climate change may increase ozone pollution in Europe due to higher temperatures and weaker atmospheric circulation. Changes in wind patterns and increased desertification increase the long-range transport of air pollutants, including aerosols, ozone, desert dust, mould spores and pesticides. Changes in the mean and variability of temperature and precipitation are projected to increase the frequency and severity of fires (32).
The air pollutants of greatest concern to health are ozone and particulate matter (PM). Ozone causes 20,000 premature deaths and 200 million person-days of acute respiratory symptoms per year in the EU while high levels of man-made PM shorten each EU citizen’s life expectancy by over 8 months on average. In the European Region, 13,000 premature deaths in children aged 0–4 years have been observed from PM (33, 34). Ozone concentrations in the United Kingdom are estimated to be likely to increase with a changing climate. This will increase attributable deaths and hospital admissions: up to about 1500 extra deaths (35). The EuroHEAT project found that respiratory and cardiovascular deaths are higher during heat-waves when ozone and PM pollution are high (36).
Climate change has caused an earlier onset of the spring pollen season in the northern hemisphere: by around 15 days over the last three decades. It is reasonable to conclude that allergenic diseases caused by pollen also appear earlier in the year (32). More research is needed to understand the effects of climate change on respiratory diseases.
Poorer air quality that may result from climate change could pose serious problems for asthmatics as well as causing damage to plants and buildings (5). Besides, wetter weather is likely to increase incidence of damp in dwellings leading to further respiratory and associated diseases(8). Health risks from climate change. It is thought that the problems of urban air pollution will be exacerbated by climate change by enhancing the production of photochemical pollutants, and possibly enhancing the biological impacts of certain pollutants (19). Mould growth is likely to become more widespread. Moulds are well recognized triggers for allergy sufferers and asthmatics (13).
It has been stated that in Scotland the secondary effects of climate change, such as increases in haze and photochemical smog caused by a combination of pollutants and stratified air, are of greater concern that the primary effects of higher temperatures (8). This may result in more cases of asthma, allergenic disorders, and cardio-respiratory diseases.
Leaching of pollutants
There are health issues arising from the leaching of wastes from older landfill sites due to a rising water table and from intense rainfall. Also, there are potentially critical issues arising from more flooding of old mine workings generating flows of contaminated water into waterways (3).
Floods
Floods are the most common natural disaster in Europe. The adverse human health consequences of flooding are complex and far-reaching: these include drowning, injuries, and an increased incidence of common mental disorders. Anxiety and depression may last for months and possibly even years after the flood event and so the true health burden is rarely appreciated (29). The summer 2007 floods had a significant impact on people’s health and wellbeing. Many people suffered from illnesses, ranging from coughs and colds to bronchitis and heart attacks. Psychological impacts included increased levels of anxiety during periods of rainfall, and as a result of temporary living arrangements, dealing with insurers/builders and financial difficulties (60).
Effects of floods on communicable diseases appear relatively infrequent in Europe. The vulnerability of a person or group is defined in terms of their capacity to anticipate, cope with, resist and recover from the impact of a natural hazard. Determining vulnerability is a major challenge. Vulnerable groups within communities to the health impacts of flooding are the elderly, disabled, children, women, ethnic minorities, and those on low incomes (29).
West and Gawith (1) present an overview of expected climate change impacts on several activities for the United Kingdom as a whole for the 2020s, the 2050s and the 2080s, based on the studies of UKCIP carried out so far (UKCIP = UK Climate Impacts Programme). The results for health are listed below. These results assume no adaptation to climate change.
Expected positive impact on health Expected negative impact on health Uncertain impact on health General Effects of air pollutants may be reduced (humidity related) warmer summers may increase outdoor activity and increase the risk of exposure to UV radiation. Onzone effects in summer may increase deaths and hospital admissions. Health impacts (direct and indirect) from flooding could increase. Vectorborne diseases may present a limited increase locally Increase in deaths and injuries from storm, gales and storm surges. Increase in disastrous coastal flooding as a result of sea level rise and increased storm surges 2050s (under UKCIP98 Medium-High scenario) Cold related deaths may decline by up to 20,000 fewer cases/year Heat related deaths increase from 800 to 2800/year. Food poisoning cases increase up to 10,000/year due to warm weather.Skin cancer likely to increase by 5000 cases/year, cataracts by 2000 cases/year
West and Gawith (1) present an overview of expected climate change impacts on several activities for different regions of the United Kingdom, based on several regional scoping studies. The results for health and healthcare mainly refer to negative impacts and are listed below.
Several features of modern cities interact with the changing climate to exacerbate the risks and increase vulnerability to climate change. These include (20):
The degree to which population vulnerability to outdoor temperature is reduced by improvements in infrastructure, technology, and general health has an important bearing on what realistically can be expected with future changes in climate.
Preventive measures can be divided into pre-flood activities, health protection during floods, and long-term health protection (37).
In the long term, the most important measure to take is improving urban planning and architecture, energy and transport policies. Such improvements should begin now, as the lead time for policy development is very long (36)).
From an analyses of causal factors of excess winter deaths (EWDs) over the past 60 years it was concluded that, contrary to previous studies, the absolute number of EWDs may increase in the coming decades due to an increase in future winter temperature volatility and because of a growing and ageing population (62). In line with this conclusion it was stated that influenza vaccination for people over 65 would be very beneficial.
Adjustments to existing surveillance practices in the EU will enhance preparedness and facilitate the public health response to emerging infectious diseases and thereby help contain human and economic costs. For instance, enhanced collaboration between the veterinary surveillance and public health sector will advance preparedness and response if pathogens and vectors become prevalent in the region and pose a threat to humans (56).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for the United Kingdom.