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Logo of bmjThis ArticleThe BMJ
BMJ. 2007 September 29; 335(7621): 636.
PMCID: PMC1995474

Doctors should speak out on climate change, expert says

Doctors and health workers have a duty to draw attention to climate change and try to change people's behaviour to avert disaster, an expert on the issue told a conference in Chicago last week.

Anthony McMichael, director of the National Centre of Epidemiology and Population Health at the Australian National University, Canberra, said that doctors had a particular responsibility because they had influence and because the health sector would have to deal with some of the worst effects of climate change.

Addressing the annual interscience conference on antimicrobial agents and chemotherapy in Chicago, Dr McMichael acknowledged that 5-10 years ago the topic would not have been on the agenda, “but the evidence is accruing rather more rapidly than we would have anticipated.”

Speaking to the BMJ he said that the medical profession was still held in high regard and had influence. He pointed to its leadership on the nuclear disarmament debate decades ago as an example of what could be done with that influence. “Planet [climate] change and its consequences to human health now loom probably orders of magnitude larger than the nuclear debate.”

The health sector needs to understand that it will have to bear many of the repercussions of global climate change. “We've got work to do to try to head off aggressive risks before adverse health occurs,” he said.

He added, “We've got to get more imaginative about working with other sectors, other arms of government, making the argument that every ministry is a health ministry.

“The health sector has been much too separatist in the past. It has been thinking that all it has got to do is run a healthcare system and traditional public health. Climate change is telling us that no, that's not good enough. We're going to have to be more imaginative, more collaborative, and be prepared to look to a more distant future as well as deal with the problems that press on us in the here and now.”

Giving the keynote speech to the conference, he reviewed projected patterns of how temperature and rainfall are likely to change throughout the world and how such change might directly affect the prevalence of human infectious diseases. There are likely to be indirect effects as well, he said, with shifting patterns of diseases that affect plants and livestock.

One example he cited was the fluctuation of what is called the El Niño or La Niña effect of warmer or cooler ocean currents, which in turn affects rainfall in Pacific rim countries. Rainfall has a major effect on the mosquito population and the incidence of dengue fever. Another example of the effect of climate on the incidence of diseases was apparent in China. “Over the last few decades the critical freezing zone that sets the limit on snails that are the intermediate host of schistosomiasis has been drifting northwards, and there has been a report of increased incidence of disease.” The change could put an additional 21 million people at risk of the disease, Dr McMichael said.

In some areas certain diseases would decline. Modelling indicated that malaria would become less prevalent in east Africa as the region became more arid and less hospitable to mosquitoes. But although it was good that malaria would decline, the aridity would mean it was also less hospitable to humans.

Most examples of the effects of climate change on health came from the developing world. Dr McMichael said that this was due to two factors: “Firstly, in general the density of parasitism and infectious agents is greater at low latitudes in tropical regions, in part because of the warmth and moisture. Secondly, the lower income countries have not yet managed to eradicate or constrain some of the historical infectious diseases that the rich countries have.”

He used the example of malaria, which existed throughout the United States and much of Britain until the middle of the last century. Malaria was eliminated from these countries mainly through widespread use of the pesticide DDT and the rapid detection and treatment of cases to break the chain of transmission.

He confessed to having divided feelings about the possibilities of change. “I'm an optimist in the sense that unlike any other species we have the capacity to foresee the future—we've got this extraordinary legacy from evolution, we have a big brain capable of abstract thought and future planning.

“But I'm a pessimist in the sense that our societies and governments are showing no good capacity to understand how urgent the issue is and to find less selfish ways of responding. Those are easy words for any of us to say, but of course we are all programmed to be selfish and to look after number one. And that is reflected in how society is responding.”

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