Local Air Pollution
Although some air pollution can be carried far from the source, human health is most directly affected by local pollution. These pollutants can be short-lived or persistent, organic or inorganic, toxic, caustic, irritant, or manifest other types of environmental problems, such as acidity or change properties due to photochemical reactions.
Air pollution is major cause of premature death, debilitation, and loss of life quality, as well as causing local, regional and global problems for all living systems. Air pollution also has serious negative effects for economies, not least of which are hundreds of millions of lost workdays per year.
The main sources of anthropogenic air pollution are industry, construction, transport, and agriculture. Each of these can create a range of differing pollutants, with very variant consequences for the human population and ecosystems.
Even if some air pollutants are non-toxic, they can still cause serious problems. For example, carbon dioxide from vehicle and industrial emissions does not directly harm the local human population, but is a major cause of the changes to the global atmosphere, leading to the enhanced greenhouse effect and global warming.
A pollutant is any substance, natural or man-made, which causes damage to the natural environment or harms human health when introduced into the free environment. Substances or mixtures which are harmful to organisms, or even entire ecosystems, are divided into different categories, depending on their chemical compositions, and also their toxicity potential.
Important parameters are bioaccumulation potential, biomagnification potential, permanence in the ecosystem, symbiotic relationships, secondary products, and toxicity. Pollutants can be caused by natural or anthropogenic activities, and can be solid, liquid, or gaseous in state.
The European Union regulates vehicle air pollution through the Emissions Standard, which sets limits on emissions of pollutants and greenhouse gases. Since January 2005, cars must satisfy the Euro-4 standard. Industrial pollutants are regulated in many countries via Pollutant Release and Transfer Registers (PRTR). These are systems to collect and disseminate information on environmental releases and transfers of toxic chemicals from industrial and other facilities.
Volatile Organic Compounds
Volatile Organic Compounds are carbon-based compounds with a low boiling point and high vapour pressure at room temperature.
Satellite image of pollution over China: the forecast is not good
Industry and commerce give rise to a broad range of VOCs, such as from paint solvents. VOCs are also produced by incomplete burning in combustion engines and furnaces.
Local and regional
Though not highly toxic, VOCs can be caustic and lead to health issues, such as respiratory, eye and skin problems. Some VOCs are implicated in the chemical reactions leading to photochemical smog. VOCs may result from or cause water contamination, and be transported by watercourses.
Air and water regulations restrict the production, storage, transport and use of a specified number of anthropogenic VOCs. The substitution of aqueous solvents for aliphatic hydrocarbons, ethyl acetate, glycol ethers, and acetone in paints and surface treatments, can eliminate these VOC hazards.
Estimates put a global emission level at more than 140 teragrams (140 million tonnes) of airborne VOCs. One group of VOCs, CFCs, responsible for the breakdown of the ozone layer in the stratosphere, are largely banned, and the ozone 'hole' may have been stabilised.
Particulate Matter PM
Respirable suspended particles ( < 10 µm in diameter (PM10)), fine particles (< 2.5 µm (PM2.5)), aerosols, and other microscopic and macroscopic particles suspended in the air.
Anthropogenic and natural.
Local, regional, and global.
PM can be breathed into the lungs, where, if fine enough, it can enter the bronchioles and alveoli, causing lung cancer and other respiratory diseases. Toxins may also enter the blood stream. Regional smog, such as the South-East Asia cloud, can cause changes to precipitation patterns, and cause pollution of land and water. Aerosols and PM are also inculpated in atmospheric changes, in particular as radiative forcing elements in climate change (so-called 'global dimming').
Fuel efficiency, filtering and catalytic converters. In industry, indoor and local pollution has been reduced by legislation imposing the use of technologies, such as cyclonic separators, filters, wet flue scrubbers, and electrostatic precipitators. Particulate matter is a serious pollution problem for China, with a very large economic cost, as well as public health burden.
Ever stricter regulations, improved public awareness and technologies, have led to an improvement in smog levels in many countries. Vehicle emissions, particularly diesel, still load many PMs into the atmosphere. As developing countries increase their vehicle traffic and power consumption per capita levels, PMs will take an increasing toll on the health of the populations and ecosystems, unless cleaner technology is adopted.
Pollutant Release and Transfer Registers PRTR
Industrial pollutants are regulated in many countries via Pollutant Release and Transfer Registers (PRTR). These are systems to collect and disseminate information on environmental releases and transfers of toxic chemicals from industrial and other facilities.
The pollutant emission register contains data from industries that emit pollution from point sources mainly. Diffuse sources, such as from agriculture and transport, could also be considered.
The data includes entries/emissions to soil and the earth's surface, water, air, as well as waste quantities.
The data are subsequently integrated into environmental information systems, and are therefore an important part of the environmental management systems of a city, region or country.
Ozone (O3) is an allotrope of oxygen, with three atoms instead of the normal two. It is an important, if minor, constituent of the stratosphere, where it forms a protective layer, blocking the Sun's dangerous UV radiation from reaching the surface. It is a pollutant near ground level, created by photochemical reactions from vehicle and industrial emissions.
Ozone is a trace gas in the atmosphere, contributing only 0.6 ppm (parts per million, or 0.0006%).
In the troposphere, near the ground, it forms from photochemical reactions. The interaction of solar radiation with pollutants, primarily nitrogen dioxide (NO2), produces ozone during daylight, which reverts to other compounds when the sun is not present. It is therefore a secondary pollutant.
Although not toxic in small concentrations, it is an irritant, and can lead to respiratory illnesses after prolonged exposure.
Human sources, primarily traffic and heating emissions, mainly NOx. VOC (volatile organic compounds) from solvents, and biogenic nitrogen oxides (from excess fertilser) are ozone-forming substances.
Local, urban areas and near busy roadways.
Tropospheric ozone causes respiratory problems, especially with physical exertion outdoors in the afternoon. Due to its high reactivity, ozone is considered a suspected carcinogen. According to the MAK Commission (MAK = maximum allowable concentration) of the Deutsche Forschungsgemeinschaft (DFG) ozone "is suspected of triggering cancer in humans."
Limits: 180 µg/m3 (1-h average) is the level at which the general public will be advised through the general media behavior. In Germany, there is an obligation to inform threshold of 180 µg/m3 (1-h average), and an alert threshold of 240 µg/m3 (1-h average). The maximum daily 8-hour value of 120 µg/m3 must not be exceeded more than 25 days per calendar year, averaged over 3 years.
Although the ozone layer is protected from CFCs by the Montreal Protocol (1986, CFC), and the hole is slowing its growth, the crisis is not over.
Ozone in urban areas is related to NOx emissions. Improved fuel quality, higher efficiency of use, and catalysators help to reduce emissions.
Solvents are better regulated, and in most cases may not be released into the open air.
Ozone is a strong oxidising agent, and causes respiratory illness in humans and animals. Ozone in the stratosphere forms the ozone layer, which protects life on the surface from the UV light of the sun.
It is a health hazard and can cause lung cancer and other diseases. It therefore bears the EU classifications for oxidising agent, very toxic, corrosive, and irritant. In Germany, since it is carcinogenic, it has no MAK value. In Switzerland, the MAK value is 0.1 ml⋅m-3 (0.2 mg⋅m-3.
Ozone forms through photosensitive reactions from nitrogen oxides NOx:
Under UV-radiation: NO2 → NO + O
O + O2 → O3
NO + O3 → NO2 + O2
CFCs (chlorofluorocarbons) are a group of organic compounds containing carbon (C), chorine (Cl) and fluorine (F), which are banned and may not be released into the atmosphere, as they cause a depletion of the ozone layer.
A sub-group of the halocarbons, CFCs are a broad range of organic compounds with low-molecular weight. They are used as coolants, propellants, and solvents. They are hydrocarbons whose hydrogen atoms have been replaced by the halogens chlorine and fluorine. Saturated CFCs have only single bonds.
The release of CFCs into the atmosphere is responsible for the thinning of the ozone layer, which is located in the stratosphere, a phenomenon often referred to imprecisely as the 'ozone hole'. This exposes people and all living things to dangerous levels of UV light. The use of CFCs is largely banned by the Montreal Protocol of 1987, which oversees the phase out and replacement of CFCs by alternatives (HFCs, hydrocarbons, CO2).