Greenhouse gas reductions will benefit human health

Reducing greenhouse gas emissions will have major direct health benefits, especially in low-income countries.

Tackling climate change by reducing carbon dioxide and other greenhouse emissions will have major direct health benefits in addition to reducing the risk of climate change, especially in low-income countries, according to a series of papers on “Health and Climate Change” published recently in the British medical journal The Lancet.

According to the authors, many measures to reduce greenhouse gas emissions will themselves have additional and independent positive impacts for health. These co-benefits will offset at least some of the costs of climate change mitigation, and should be taken into account in international negotiations.

The Lancet studies were undertaken by an international team of scientists. Each study focuses on one sector in which greenhouse-gas emissions need to be reduced, including household energy use, transport, electricity generation, and food and agriculture. A fifth study reviews the effect on health of short-lived greenhouse pollutants, which are produced in several sectors.

In rich countries, energy use in buildings for heating, lighting, and other needs is responsible for a large part of energy demand. In the poorest parts of the world, energy for cooking and heating relies on solid-fuel household stoves. Either way, household energy use is responsible for a significant amount of greenhouse gases.

The simple stoves used by the poorest half of the world’s households operate at low combustion efficiency and produce airborne particles, including black carbon, in addition to various greenhouse gases and other health-damaging pollutants.

National programmes offering low-emission stove technology for burning local biomass fuels in poor countries could, over time, avert millions of premature deaths, and constitute one of the strongest and most cost-effective climate–health linkages.

Transport accounts for almost a quarter of all fossil fuel greenhouse-gas emissions. Reduction of motor vehicle use through more walking and cycling will not only diminish transport emissions but should also reduce obesity, lower the rate of chronic diseases caused by physical inactivity, lessen the health-damaging effects of air pollution, and make the roads safer for pedestrians and cyclists.

Electricity pro-duction is a major contributor to greenhouse-gas emissions. The review concentrates on only one of the health effects of power generation – the emission of airborne particles causing damage to the respiratory and cardiovascular systems.

Changing methods of electricity generation to reduce CO2 emissions would reduce particulate air pollution and deaths. The biggest gains would be in cardiopulmonary disease, followed by lung cancer. The effect would be greatest in India and China and lowest in the EU. (The more modest improvement to be expected in Europe arises from the relatively clean methods of burning fossil fuels already in use.) The cost of these changes would be significantly offset by reduced costs of death from pollution, especially in China and India.

Agriculture and food production account for 10–12 per cent of greenhouse-gas emissions, and livestock farming is responsible for four-fifths of these emissions, which include methane emitted by ruminant animals. Land-use changes, including deforestation for livestock production, add substantial further emissions.

Changes in farming practices to reduce emissions include greater efficiency in livestock farming, more carbon capture through changes in land use, better manure management, and less dependence on fossil fuels. These four changes are necessary but unlikely to be sufficient to meet the target for greenhouse-gas emission reductions, and the study assesses the consequences for health of a fifth approach – a 30-per-cent reduction in livestock production.

A fall in the adult consumption of saturated fat from animal sources would reduce heart disease, and provide additional health benefits from less obesity and diet-related cancers.

Short-lived greenhouse pollutants account, directly or indirectly, for a substantial proportion of global warming, and are also responsible for the bulk of the direct damage to human health from global energy use. The pollutants include sulphate, organic and black carbon, carbon monoxide, non-methane volatile organic compounds, and other gases that are responsible for ozone creation, such as methane and nitrogen oxides.

Whether they are warming or cooling, all short-lived greenhouse pollutants – or, in the case of methane, its atmospheric by-product, ozone – affect human health. Atmospheric ozone and sulphate, for example, are both associated with cardiopulmonary toxicity. Breathing air laden with fine particles is associated with increased morbidity and mortality. WHO has estimated that in 2000 this caused well over two million premature deaths.

Reductions in atmospheric concentrations of sulphate, black carbon and ozone will benefit health. According to the study, there is little evidence that sulphate particles, which are climate cooling, are less harmful to health than are undifferentiated particles, and some evidence that they are more harmful. Because of their short lifetimes in the atmosphere, a reduction in the emissions of black carbon and ozone precursors will offer almost immediate benefits.

Christer Ågren

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