From smog hanging over cities to smoke inside the home, air pollution poses a major threat to health and climate.
A recent study from the Lancet Commission on Pollution and Health has established that the annual death toll from environmental pollution is approximately 9 million persons, or 16% of worldwide deaths each year. This number goes beyond the amount of deaths arising from wars on one side, and AIDS, tuberculosis and malaria combined on the other. Strikingly, more than half of those casualties are caused by air pollution, which has been dubbed by the World Bank as “the deadliest form of pollution” and “the fourth leading risk factor for premature deaths worldwide”.
In a collaborative research, the WHO and the Energy Policy Institute of the University of Chicago developed the Air Quality-Life Index (AQLI) aimed at measuring the impact of air pollution on life expectancy. The findings were quite chilling: in heavily polluted regions such as Eastern China or Northern India, a person’s lifespan can be shortened by an average of three-four years; in cities like Beijing, Tianjin or New Delhi life expectancy reduction easily approaches the decade.
The major outdoor pollution sources include vehicles, power generation, building heating systems, agriculture/waste incineration and industry. In addition, more than 3 billion people worldwide rely on polluting technologies and fuels (including biomass, coal and kerosene) for household cooking, heating and lighting, releasing smoke into the home and leaching pollutants outdoors.
Main Pollutants and their impacts on health
Particulate Matter (PM)
PM is the pollutant that affects more people. PM is composed by sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water. It consists of a mixture of solid and liquid particles of organic and inorganic substances suspended in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.
The most health-damaging particles are those with a diameter of 10 microns or less, (≤ PM10), which can penetrate and lodge deep inside the lungs. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.
Ozone at ground level is one of the major constituents of photochemical smog. The ozone molecule (O3) is harmful to air quality, outside of the ozone layer. Tropospheric, or ground level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC).
Excessive ozone in the air can have a marked effect on human health. It can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases. Several European studies have reported that the daily mortality rises by 0.3% and that for heart diseases by 0.4%, per 10 µg/m3 increase in ozone exposure.
Relatively low amounts of ozone can cause chest pain, coughing, shortness of breath and throat irritation," according to the EPA. "It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections."
Nitrogen dioxide (NO2)
The major sources of anthropogenic emissions of NO2 are combustion processes (heating, power generation, and engines in vehicles and ships).
Nitrogen dioxide is an important air pollutant because it contributes to the formation of photochemical smog, which can have significant impacts on human health.
The main effect of breathing high levels of nitrogen dioxide is the increased likelihood of respiratory problems. Nitrogen dioxide inflames the lining of the lungs, and it can reduce immunity to lung infections. This can cause problems such as wheezing, coughing, colds, flu and bronchitis.
Increased levels of nitrogen dioxide can have significant impacts on people with asthma because it can cause more frequent and more intense attacks. Children with asthma and older people with heart disease are most at risk.
Sulfur dioxide (SO2)
The largest source of SO2 in the atmosphere is the burning of fossil fuels by power plants and other industrial facilities. Smaller sources of SO2 emissions include: industrial processes such as extracting metal from ore; natural sources such as volcanoes; and locomotives, ships and other vehicles and heavy equipment that burn fuel with a high sulfur content. Another important source of SO2 is the burning of sulfur-containing fossil fuels for domestic heating.
Sulfur dioxide affects human health when it is breathed in. It irritates the nose, throat, and airways to cause coughing, wheezing, shortness of breath, or a tight feeling around the chest. The effects of sulfur dioxide are felt very quickly and most people would feel the worst symptoms in 10 or 15 minutes after breathing it in. Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels. When SO2 combines with water, it forms sulfuric acid; this is the main component of acid rain which is a cause of deforestation.
Carbon monoxide (CO)
CO is released when something is burned. Natural sources of carbon monoxide include volcanoes and bushfires. The main sources of additional carbon monoxide are motor vehicle exhaust and some industrial activities, such as making steel. Tobacco smoke is one of the main indoor sources of carbon monoxide.
Increased levels of carbon monoxide reduce the amount of oxygen carried by haemoglobin in blood. The result is that vital organs, such as the brain, nervous tissues and the heart, do not receive enough oxygen to work properly.
For healthy people, a small increase in the level of carbon monoxide can cause trouble concentrating. Some people might become a bit clumsy as their coordination is affected, and they could get tired more easily.
Volatile Organic Compounds (VOCs)
Volatile Organic Compounds (VOCs) are chemicals that evaporate easily at room temperature from certain solids or liquids. VOC levels are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide range of products numbering in the thousands. Paints, wood preservatives, aerosol sprays, cleansers, air fresheners, gasoline can all be sources of VOCs. Other examples include pesticides, building materials, copiers, printers, permanent markers, glues and adhesives.
Examples of volatile organic compounds are gasoline, benzene, formaldehyde, solvents such as toluene and xylene, styrene, and perchloroethylene (or tetrachloroethylene), the main solvent used in dry cleaning.
Benzene and formaldehyde are listed as human carcinogens in the Fourteenth Report on Carcinogens published by the U.S. National Toxicology Program; diesel exhaust particulates, perchloroethylene, and styrene are listed as "reasonably anticipated to be human carcinogens." People at the highest risk of long-term exposure to these three volatile organic compounds are industrial workers who have prolonged exposure to the compounds in the workplace; cigarette smokers; and people who have prolonged exposure to emissions from heavy motor vehicle traffic.