IPCC: Pollen, smoke and ozone levels likely to increase in warming world, affecting health of residents in major cities
By Gerard Wynn
Rising temperatures will worsen air quality through a combination of more ozone in cities, bigger wild fires and worse pollen outbreaks, according to a major UN climate report published next week.
The report follows the World Health Organisation (WHO) finding this week that air pollution is the world’s biggest environmental health risk, killing 7 million people in 2012, or one in eight deaths.
The UN’s Intergovernmental Panel on Climate Change (IPCC) will report on climate impacts ranging from damaged crops to rising seas.
The report, leaked online, is the second in a three-part publication which the IPCC produces every five to six years on the threats posed by global warming.
Pollen, smoke and ozone are all are expected to increase.
Each is a major health risk and all exacerbate asthma, which already affects some 235 million people worldwide, according to the WHO.
Deteriorating air quality will most affect the elderly, children, people with chronic ill-health, and expectant mothers.
The health risks from air pollution point to an extra benefit from tackling climate change, because many greenhouse gases are also pollutants.
The IPCC estimated that manmade air pollutants which are also greenhouse gases collectively reduced global life expectancy by 190 million years annually, also called disability-adjusted life years, resulting in lost economic value of $1.9 trillion, or 2.7 percent of the global economy.
That represents the health benefit of entirely eliminating greenhouse gases which are also air pollutants, before accounting at all for the benefit of avoided climate change.
Ozone is produced by the reaction of sunlight with nitrogen oxides (NOX) and volatile organic carbon emitted from vehicles burning fossil fuels.
Breathing ozone can contribute to chronic obstructive pulmonary disease, which is responsible for about a tenth of all deaths from outdoor air pollution.
A systematic analysis for the Global Burden of Disease Study, published in the Lancet in 2012, found that ozone pollution was already responsible for about 200,000 premature deaths annually.
Higher temperatures both speed up the chemical reactions which produce ozone, and lead to more emissions of volatile organic compounds from natural sources.
Where people depend on air conditioning, heat waves can also lead to more electricity generation and production of NOX from fossil fuel-fired power plants.
Higher temperatures can also accelerate the destruction of ozone. But at the local level in polluted cities, higher temperatures are expected to increase ozone production and so exacerbate health risks.
“Observational and modelling evidence indicates that, all else being equal, locally higher surface temperatures in polluted regions will trigger regional feedbacks in chemistry and local emissions that will increase peak levels of ozone,” the IPCC will say next week.
A study in a report published in 2007 in the journal Climatic Change – and quoted by the IPCC – estimated that all but one of 50 U.S. cities would see increases in ozone concentrations, as a result of climate change.
Climate change will likely lead to more frequent wild fires, as a result of higher temperatures and more frequent extreme heat waves and drought.
The most dangerous type of smoke is particulate matter with an aerodynamic diameter smaller than 10 micrometers (PM10 and PM2.5).
Health impacts from wild fires include heart and lung diseases.
A study published in the journal Environmental Health Perspectives in 2012 calculated that exposure to smoke from wild fires was already responsible for 339,000 premature deaths annually, with a range of 260,000 to 600,000.
Studies have recorded exceptional levels of smoke in cities near wild fires.
Moscow experienced an exceptional heat wave in 2010, the probability of which had tripled as a result of climate change, according to research published in the journal Geophysical Research Letters.
Southerly winds carried smoke and haze from fire-afflicted southern provinces directly into Russia’s capital city from August 1-10, reported a satellite study published in the journal Atmospheric Chemistry and Physics.
“The highest 24 hour pollution levels recorded in Moscow during these conditions were between 430 and 900 μg/m3 PM10 most days, but occasionally reached 1500 μg/m3.,” said the latest IPCC report, compared with the 20 μg per cubic metre WHO guideline.
South East Asia has suffered exceptional forest fires, associated with extreme droughts, and notably in 1997.
“It is estimated that more than two million hectares of forests burned in the Indonesian islands of Kalimantan and Sumatra,” reported the World Meteorological Organisation in 2012, in its climate and health atlas, as quoted in next week’s IPCC report.
“In Indonesia, among the 12,360,000 people exposed to the haze, it was estimated that there were over 1,800,000 cases of bronchial asthma, bronchitis and acute respiratory infection.
Health surveillance in Singapore from August to November 1997 showed a 30% increase in hospital outpatient attendance for haze-related conditions.
Pollen is released by flowering grasses, trees and weeds (in particular ragweed), and is significantly associated with allergic rhinitis, or hay fever.
Allergic rhinitis alone was responsible for direct medical costs of $6.2 billion annually in the United States, according to the U.S. Environmental Protection Agency, reporting in 2008, affecting approximately 40 million people, including 16 million children.
Climate change will likely increase pollen production both through higher levels of carbon dioxide, which stimulates pollen production by flowering plants, and warming, which will lengthen flowering seasons, the EPA said, as quoted by the IPCC.
“Experimental results have consistently demonstrated that doubling carbon dioxide levels from current to projected future levels (700 ppm) would result in a 60 to 90% increase in ragweed pollen production,” the EPA report said.
Smoke and ozone can worsen the allergic impact of pollen, according to the EPA.
“The literature demonstrates that the inflammatory effects of ozone, particulate matter, and sulfur dioxide allow for easier penetration of pollen allergens into the airways; that air pollutants can increase the release of antigens in pollen grains that lead to allergic responses; and that pollutants can also absorb pollen grains and, thus, prolong their retention in the body.”