Introduction
Other particulates include dust from roads, industrial emissions and natural substances such as windblown sea salt. PM 1 represents a quantity of particulate matter that is 1 micron or less in diameter. PM 2.5 signifies particulate matter of 2.5 microns or less in diameter (more than 100 times thinner than a human hair) and PM 10 signifies that the diameter of the particulate matter is 10 microns or less. In Ireland the main source – especially of the smaller and more dangerous PM 1 and PM 2.5 particles – is solid fuel burning for home heating. 1.4.3 Sulphur Dioxide (SO 2 ) Sulphur Dioxide (SO 2 ) is released when fuel (mainly coal and oil) containing sulphur is burned at power generating plants, released as a by-product of industrial processes or released from exhaust flues from home heating systems. High concentrations of SO 2 can result in temporary breathing impairment for asthmatics that are active outdoors. Other effects that have been associated with longer-term exposures to high concentrations of SO 2 , in conjunction with high levels of particulate matter, include aggravation of existing cardiovascular disease, respiratory illness and alterations in the lungs’ defences. Together, SO 2 and NO X are the major precursors to acidic deposition (acid rain), which is associated with the acidification of soils, lakes and streams and the accelerated corrosion of buildings and monuments. 1.4.4 Ozone (O 3 ) Ozone is a natural component of the atmosphere. Most ozone is found high up in the stratosphere, the layer of the atmosphere between 12km and 50km above sea level. Ozone is also found in the troposphere, the layer of the atmosphere next to the earth. Tropospheric, or ground level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NO X ) and volatile organic compounds (VOCs). This occurs when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight. Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments, but it can still reach high levels during colder months. Ozone can also be transported long distances by wind, so even rural areas can experience high ozone levels. Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and airway inflammation. Long term exposure to moderate concentrations causes a reduction in lung capacity and can worsen heart disease, bronchitis, emphysema and asthma. Trophospheric ozone contributes to the greenhouse effect and subsequent global climate change. 1.4.5 Benzo[a]pyrene (BaP) Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH). The main source of atmospheric BaP is residential wood burning. It is also found in coal tar, in vehicle exhaust fumes (especially from diesel engines), in all smoke resulting from the combustion of organic material (including cigarette smoke) and in charbroiled food. It is part of the group of Polycyclic Aromatic Hydrocarbons (PAHs) and is recognized as one of the most carcinogenic of the group. Health Impacts of Air Pollution Long-term exposure to high levels of pollution can severely weaken immune systems. Air pollution can exacerbate pre-existing respiratory conditions such as asthma and negatively affect lung and heart function. 1.5 Short-term exposure mainly affects people who are already classed as ‘vulnerable’; i.e. individuals with pre-existing conditions that are aggravated by air pollutants. Children and the elderly can also be vulnerable in the short-term if they are exposed to high levels of air pollution. Air pollutants can cause a range of physiological effects, namely (see Figure 1.2); » Ultrafine particles can pass from the lungs into the blood stream and may cause many adverse outcomes including systemic inflammation.
4
Powered by FlippingBook