Scientists on Climate Change
Climate Change and Global Public Health: A Direct Connection   
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Sir Andrew (m): I think many of the projections do suggest that we may be nearing the point of not being able to keep the increase in temperature down to two degrees which many scientists believe is the kind of level which we need to keep the climate warming down to. So the kind of trajectory we're on at the moment suggests that we may well breach that unless we take radical action. So that's, I think, the reason for the urgency.

HOST: Perceptive viewers, welcome to Planet Earth: Our Loving Home. In 2009 a series of papers published in the esteemed British medical journal, The Lancet, examined how curbing greenhouse gas emissions in four sectors could enhance public health.

Sir Andrew (m): This is really the result of a very intense period of collaborative activities; it's brought together 55 scientists from nine different countries to work together, to look at the potential public-health benefits of strategies to reduce greenhouse gas emissions in four main sectors. So what was the scope of the work?

Much of the work up to now on climate change and health has focused quite naturally on the impacts of climate change on human health. And this program of work looks at it from a different perspective. It looks at the potential effects on public health, of strategies to reduce greenhouse gas emissions in these four important sectors: household energy, urban land transport, food and agriculture and electricity generation.

And we chose those sectors because they're all important contributors to greenhouse gas emissions, and they all have, of course, important impacts on human health. In addition to that, we also looked at the health effects of short-lived greenhouse pollutant emissions. And up to now, a lot of focus, quite understandably has been on carbon dioxide, which is a long-lived greenhouse gas.

HOST: This week we feature the insights of two experts involved in this laudable study examining the effects of climate change on health. The first is Dr. Alan Dangour, senior lecturer at the renowned London School of Hygiene and Tropical Medicine and a registered public health nutritionist with a background in biochemistry and biological anthropology.

The second is Sir Andrew Haines of the same institution, a professor of public health and primary care with joint appointments in the Departments of Social and Environmental Health Research and Nutrition and Public Health Intervention Research.

Household Energy

In the first paper, 『Public health benefits of strategies to reduce greenhouse gas emissions: Household energy』 the researchers modeled the effects of improving the energy efficiency of UK dwellings through insulation, ventilation, fuel switching and behavioral changes and of replacing inefficient cookstoves in India with 150-million cleaner-burning versions.

Sir Andrew (m): In the household environment we've looked at the impact of replacing highly polluting cookstoves in a country like India with low-emission stoves and we've shown that you could reduce exposure to indoor air pollution, which is a very major cause of death, perhaps save two-million lives over a period of 10 years from a program of introducing 150 million of these improved cookstoves into a country like India.

But in the UK it's a very different issue. In the UK we've looked at the impact of improving house insulation and ventilation to reduce energy consumption.

Sir Andrew (m): And we've looked at the impacts on health of those strategies and we've shown that you'd get obviously a much smaller impact on health because the health problems are not the same in the UK as in India, but still worthwhile benefits to human health by implementing these changes.

So they've obviously got different implications for the two countries. In the case of India, an improved energy-efficient cookstove might only cost perhaps US$50.

So there would be maybe some need to subsidize the very poorest but those stoves might last for a few years. From the UK, the cost would be higher, certainly thousands, perhaps £10,000 or more pounds to re-fit old houses with these kinds of approaches.

HOST: Assuming the household retrofits were made, aside from enhanced public health, the scientists found that the UK would have a savings of 0.6 megatons of carbon dioxide per million citizens in one year.

By introducing the efficient cookstoves in India, they concluded that a substantially lower incidence of acute lower respiratory infection in children, chronic obstructive pulmonary disease and ischemic heart disease would occur.

Urban Land Transport

The second paper examined the impact on carbon-emission levels and public health in London, UK and Dehli, India if these cities implemented programs to make cars greener and promoted eco-friendly modes of transportation.

Sir Andrew (m): For urban land transport, we're really talking about improving the activity that people undertake to move around, so for short distances, replacing private car journeys with increased walking and cycling, and also those cars that we do have, reducing the emissions, both greenhouse gas emissions and air pollution.

HOST: The scientists determined that such programs could result in lower rates of heart disease in the populations of both cities and decreases in greenhouse gas emissions if residents used greener modes of transportation.

Electricity Generation

In the third paper the researchers studied the effects on public health of less-polluting methods of electricity generation in the European Union, India and China. It was found that the greatest public-health benefits would be seen in India, where air pollution levels are currently very high.

Food and Agriculture

In the fourth paper, 『Public health benefits of strategies to reduce greenhouse gas emissions: Food and agriculture』 the researchers examined how Britain could meet the carbon-emission- reduction goals set by the UK Committee on Climate Change, which call for an 80% lessening of 1990 CO2 concentrations by 2050, with a minimum 50% reduction by 2030. The experts concluded that the only way this goal could be reached was through a 30% reduction in UK livestock production, with a corresponding 30% decline in the British public's consumption of animal products.

It was also determined that this reduction in consumption would enhance public health because decreased intake of the saturated fats found in animal products would lead to lower heart-disease rates.

Dr Alan Dangour (m): We modeled the available evidence and we found that as well as the mitigation strategies that are currently available, such as improved technologies in the agriculture sector, we would need to reduce the production of livestock by about 30%.

And we focused on livestock because livestock is the major producer of greenhouse gases in the sector. We then assumed that there would be an identical reduction in the amount of livestock products consumed and especially in saturated fat consumption, and saturated fat is a known risk factor for ischemic heart disease, the major cause of mortality in high-income countries.

And we found that if you use the methodology which is recommended by the World Health Organization, a 30% reduction in saturated-fat intake would result in 18,000 premature deaths being averted in the UK in one year. So there would be a significant health benefit of a policy which is ostensibly aimed at reducing emissions.

Sir Andrew (m): Well, first of all, why do we focus on animal product consumption? The reason we did that is livestock contribute quite a substantial proportion of greenhouse gas emissions from the food and agricultural sector. You can't ignore the food and agricultural sector if you're serious about reducing greenhouse gas emissions quite dramatically, which is what we know has to be done. So we look first of all at the potential for technological change.

Could it all be done just by improving the technology of better manure management, more efficient use of feedstocks and so on? And we concluded from the evidence presented to us that (it) would be necessary to do that, but not sufficient. And the gap seemed to us between the amount of GHG, greenhouse gas reductions that could be achieved through these technological changes and those that were needed was perhaps suggested to us at about a 30% reduction in animal- product consumption would be required.

So we then modeled the impact of a 30% reduction in a country like the UK. So it's a high-consuming country. And what we did was to look at the impact on that, on saturated fat consumption, which as we know is quite an important causal factor of heart disease and other medical problems. And so we modeled the impact of reducing the saturated-fat consumption from animal products by 30% and then showed that that would result in about a 15 or 16% reduction in ischemic heart disease.

Shorter-lived Greenhouse Pollutants

HOST: In the fifth paper the investigators analyzed how black carbon, ozone and sulfates affect public health. These substances are called 『shorter-lived』 pollutants because when compared to carbon dioxide, which can take a thousand years to dissipate from the atmosphere, they take a relatively short time to disappear.

Black carbon's atmospheric lifespan ranges from one to four weeks and its Global Warming Potential (GWP) over a 20-year timeframe, has been calculated to be between a staggering 1,600 to 4,700 times the warming-power of carbon dioxide.

Sir Andrew: Black carbon is damaging to health; that was one of the conclusions. It certainly seems to be true. It's not clear whether that's more so than the kind of undifferentiated particles that are normally used in air pollution studies, but certainly they are damaging to health. And the study also adds to the evidence that ozone causes excess mortality independently from other pollutants. So the control of both black carbon, which arises partly from household energy, but also from other sectors, and ozone, would both reduce climate change and benefit population health. And because they're short-lived, some of them only last for days, reductions in the emissions could immediately benefit the climate.

HOST: Today we've seen from a public health perspective why humanity needs to immediately reduce the enormous amounts of human-induced greenhouse gases released into the atmosphere that are driving climate change.

As the cycle of producing and consuming animal products is the source of most of these gases, the most important and simplest step each of us can take to save our planet is to avoid animal products and adopt a plant-based diet. Not only would the world's embrace of the vegan lifestyle halt global warming, but numerous chronic diseases caused primarily by animal foods, such as diabetes, obesity and heart disease would virtually disappear. In closing, we'd like to thank Dr. Alan Dangour and Professor Sir Andrew Haines for discussing the findings published in The Lancet and their many implications for global public health.

For more details on today's guests, please visit the London School of Hygiene and Tropical Medicine's website at To read the papers discussed today online, please visit

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