By Lizzie Buchen

Many strategies for reining in greenhouse gases come with substantial health benefits, according to a new study. But the actions with the most dramatic impact on greenhouse gases aren't necessarily the biggest winners for health.

Twelve days before the United Nations climate summit kicks off in Copenhagen, an international task force has published five research papers exploring the impact that strategies for tackling greenhouse gas emissions would have on public health.

Public health leaders from around the world weighed in on today's announcement, including United Nations secretary general Ban Ki-moon, World Health Organization director-general Margaret Chan, US secretary for the Department of Health and Human Services Kathleen Sebelius and UK secretary of state for health Andy Burnham.

"Policies for mitigating the impact of climate change must align with policies for protecting public health," says Chan. The findings released today "can guide the assessment of alternatives for mitigation and motivate wise choices".

The reports were published in The Lancet.

Killing two birds

The team, led by epidemiologist Andrew Haines at the London School of Hygiene and Tropical Medicine, modelled a number of scenarios for reducing greenhouse gases. For each case study, the authors calculated the reductions of disability-adjusted life-years (DALYs), a measure of potential years of life lost to disease or premature death, and the megatonnes of carbon dioxide saved.

In the household energy and food and agriculture sectors, the proposal with the biggest impact on both climate change and public health was a 10-year programme in India to replace 150 million indoor biomass-burning stoves with low-emissions cooking stoves, according to lead author Paul Wilkinson, also at the London School of Hygiene and Tropical Medicine. In one year the programme would save 12,500 DALYs and 0.1-0.2 megatonnes of carbon dioxide equivalent for every million people.

By comparison, Wilkinson found that improving household energy efficiency in the United Kingdom would save more energy -- 0.6 megatonnes of carbon dioxide per million people over a year -- but would only save 850 DALYs, due in part to reduced cardiovascular and respiratory disease.

Another analysis, led by Sharon Friel at the Australian National University in Canberra, looked at the effects of reducing livestock production by 30%. Such a change in the UK would save 2,850 DALYs from heart disease; in São Paulo, Brazil, it would save 2,180.

The authors acknowledge, however, that these strategies would not be a unilateral win for health: less livestock could lead to poor nutrition in low-income countries, and better housing insulation could lead to health risks from factors such as more indoor air pollution.

Adjusting priorities

The team also assessed scenarios in the transportation and electricity generation sectors, including increased cycling and walking in London and Delhi, India. The greatest health gains would result from fewer cars and increased walking in Delhi, reducing DALYs by 13,000 when modelling the population in 2030 compared with the same population under business-as-usual conditions.

Though some scenarios have far greater health impacts than others, even the smaller benefits are worthwhile, says Haines.

Haines notes that although the world "does not have the luxury of choosing one intervention over another", societies "have the choice of which to pursue most vigorously at first".

Global leaders hope public health issues are taken into consideration at Copenhagen. Chan says she hopes the findings will "add to the urgency of negotiations", and that policymakers will use the findings to "seize an important social opportunity and ensure a broader return on their investment".

Although the effects of cutting greenhouse gases are long term and global, she says, "the health benefits are immediate" and more localized, which should sweeten the deal for politicians.