Original article by Ian Langford and Graham Bentham of the University of East Anglia's Centre for Social and Economic Research on the Global Environment. Are we set for an increase in summer deaths due to illnesses caused by heatwaves and food poisoning?

Introduction

It is tempting to be complacent about climate change when some of the health impacts in the UK could be interpreted as beneficial. Information issued by the Department of Health in 2001 celebrated the likely fall in winter deaths, particularly among elderly people. Against this though, are concerns about some of the negative impacts of hotter summers. The following feature draws our attention to a rise in cases of food poisoning associated with higher temperatures. It may be helpful to health professionals and anyone involved in food production from cooks to farmers. It is based on research already published in the following articles in the International Journal of Biometeorology: "The potential effects of climate change on winter mortality in England and Wales" (1995) 38:141-147, "Climate Change and the incidence of food poisoning in England and Wales" (1995) 39:81-86 and "Environmental Temperatures and the incidence of Food Poisoning in England and Wales" (2001) 45:22-26.

Intensive farming and warmer temperatures may increase the risk of food poisoning. (Courtesy: Compassion in World Farming)

Sections in this article

Winter illness

Food Poisoning

Where next?

Winter illness

Most analysis of the influence of climate change on human health concentrates on the adverse consequences but for elderly British people it could reduce some of the dread of winter. Only a small part of our high winter death rate in Britain is due to hypothermia. Far more deaths are associated with illnesses that affect our circulation and breathing. Trying to establish the connection between winter conditions and death rates is controversial, but a big enough body of research shows a direct link between cold weather and more deaths from diseases like pneumonia, for us to predict an improvement as our climate gets warmer. Research carried out in the 1980s suggested that a week after a period of cold dry weather deaths from pneumonia in the older age groups went up. It has been suggested that this is because immunity is weakened by cold which also plays a part in keeping the germ alive. Flu epidemics have also been shown to follow unusually low temperatures.

A patient receives treatment for Pneumonia.

Deaths from diseases affecting circulation are also more prevalent during colder weather. This could be because they make victims more susceptible to winter viruses. For instance, some research shows that many stroke patients subsequently die from pneumonia, bronchitis and hypothermia during the winter following diagnosis.

However, it is also worth noting that in very hot weather deaths from heart disease and stroke increase. As more summers like the one in 1976 become more likely, we could see some of the thousands of elderly people who avoid a winter death succumbing in the summer instead.

Food Poisoning

Another important health problem associated with summer and high temperatures is food poisoning. This is a problem that has been increasing rapidly since 1990 and can lead to death in vulnerable individuals such as the elderly, infants and those already sick. The costs of treatment and loss of working time also have an economic impact. Studies of food-borne illness in the US have estimated an annual cost of several thousand million dollars in medical expenses and loss of human productivity.

Weekly incidence of food poisoning in England & Wales 1974 - 1996

Once again there is controversy about the cause of this rising trend. It could be related to changes in methods of food production such as the shift towards intensive rearing of poultry and other animals. It might be as a result of changing patterns of retailing (the shift to convenience food), or consumer behaviour. However, superimposed on this rising trend is a pattern of seasonal changes with a high incidence in the summer and fewer cases during the winter.

So it is likely that the summer excess of food poisoning is also the result of higher temperatures. These cause more animals to become infected and the disease causing microorganisms multiply in the meat. Our research also showed a time lag between the rise in temperature and the outbreak of food poisoning. We found that there was approximately 3-4 times as big an effect of temperature a few weeks before food poisoning increased as compared to the temperature at the time. This strongly suggests that exposure of animals to high temperatures before slaughtering and in the food production process is a problem - it is not just the consumers' fault.

A meat inspector at work

Hot summers may produce particularly large increases in food poisoning. For example, the Chief Medical Officer (1990) suggested that the exceptionally large number of cases of food poisoning in England and Wales in 1989 might have arisen from the unusually long, hot summer of that year. This suggests that a trend towards higher temperatures in the future would be likely to increase the incidence of food poisoning. It is a public health problem that needs to prompt a change in behaviour by consumers and, as importantly, food producers and distributors.

Where next?

On ClimateX.org

Have a look at ‘Death on the Marshes' by Steve Lindsay and Rob Hutchinson from the University of Durham for a discussion of the prospects for a return of malaria to the UK. Also an article by Sari Kovats of the London School of Hygiene and Tropical Medicine: ‘Climate Change and Health in Europe'.