Asian brown cloud affects food safety for billions

Man-made brown clouds are jeopardizing human health and food production for three billion people in Asia.

Cities from Beijing to New Delhi are getting darker, glaciers in mountain ranges such as the Himalayas are melting faster and weather systems becoming more extreme, in part, due to the combined effects of man-made Atmospheric Brown Clouds (ABCs) and greenhouse gases in the atmosphere.

The brown clouds, the result of burning of fossil fuels and biomass, are in some cases and regions aggravating the impacts of greenhouse gas-induced climate change, says a new report from UNEP. Emissions of some fine particles (such as black carbon and soot) absorb sunlight and heat the air. Similarly, the formation of gases such as ground-level ozone also enhances the greenhouse effect.

The clouds are also having an impact on air quality and agriculture in Asia, increasing risks to human health and food production for three billion people. It is estimated that the elevated levels of ground-level ozone could result in crop losses of up to 40 per cent in Asia.
Brown clouds contain a variety of toxic aerosols, carcinogens and particles, including fine particulate matter (PM2.5). These have been linked with a variety of health effects, including respiratory disease and cardiovascular problems.

As regards outdoor exposure, increases in concentrations of PM2.5 of 20 micrograms per cubic metre could lead to about 340,000 additional deaths per year in China and India. The economic losses due to outdoor exposure to ABC-related PM2.5 have been crudely estimated at 3.6 per cent of the gross domestic product (GDP) in China and 2.2 per cent of that in India.

The World Health Organization estimates that over 780,000 deaths in the two countries can be linked to indoor exposure to air pollutants resulting from solid fuel use in the home.
“One of the most serious problems highlighted in the report is the documented retreat of the Hind Kush-Himalayan-Tibetan glaciers, which provide the headwaters for most Asian rivers, and thus have serious implications for the water and food security of Asia,” said professor V. Ramanathan, head of the scientific panel carrying out the research.

The report “Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia” can be found at

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