Contaminacion del aire

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Chapter 8

Indoor air quality

Not only do most people in the most polluted regions of the world live in urban areas, but they also spend nearly 90% of their time inside buildings, a further few per cent in vehicles and only around 6% outdoors. Therefore, in this chapter we shall look briefly at special features of indoor air quality. Despite its importance and complexity, the indoorenvironment has been much less thoroughly studied than that outdoors. The general perception is that one is ‘safe’ from air pollutants indoors, and many who are today beware of high NO2 concentrations near roads will not worry about cooking with a gas hob that potentially gives them an even higher NO2 exposure. The sources of air pollution that have been discussed so far have been characterised by theirrelease into the atmosphere at large. In general, the concentrations of these pollutants inside buildings will be lower than the concentration outside, because the pollutants will be deposited to internal surfaces during the residence time of air in the building. However, there are many additional sources inside buildings, and the same reduced air turnover that protects from external pollutants maycause the concentrations from internal sources to rise to unacceptable levels. Furthermore, the species involved include not only the same gases and particles that penetrate in from the outside, but a whole range of new pollutants that only increase to significant concentrations in the confines of the indoor environment. Table 8.1 provides a list of major health-damaging pollutants generated fromindoor sources. Additional sources include people and domestic animals, micro-organisms, moulds and fungi. The concentration of any particular pollutant at any time will be the resultant of the external and internal source strengths, deposition velocities to different surfaces, air turbulence and building ventilation rate. Correct measurement of personal exposure is a science in itself. Often thepollutant will be very non-uniformly distributed both in space and time. Many of the instruments that are used for outdoor ambient pollutant monitoring will therefore be unsuitable. The main uptake routes for airborne pollutants are through the nose and mouth, so this is where the concentrations need to be measured. Most real-time analysers are bench-based, mains-powered items which cannot becarried around. Although devices such as diffusion tubes are highly portable and take no power, they offer only time-integrated measurements which give no information about short-term peaks. There is a major need for real-time, highly portable gas and particle instrumentation which can be used to assess personal exposure. As an added complication, it has also been found that personal exposure to manypollutants can exceed that predicted from the ambient concentration – this has been called the personal cloud effect. Recently in the US, the RIOPA (Relationships of Indoor, Outdoor and Personal Air) project, with major funding from the Health Effects Institute, investigated seasonal concentrations of 16 VOCs, 10 carbonyls and PM2.5 in homes in Los Angeles (California), Houston (Texas) andElizabeth (New Jersey). As an invaluable output, never done before, this study has generated a database on concentrations of air toxics and PM2.5 in the personal breathing zone of 100 adults in each


Indoor air quality

Table 8.1 Major health-damaging pollutants generated from indoor sources Pollutant Fine particles Carbon monoxide PAH Nitrogen oxides Sulphur oxides Arsenic and fluorine VOCsand semi-VOCs Aldehydes Pesticides Asbestos Lead Biological pollutants Radon Free radicals and other short-lived, highly reactive compounds Major indoor source Fuel/tobacco combustion, cleaning, cooking Fuel/tobacco combustion Fuel/tobacco combustion, cooking Fuel combustion Coal combustion Coal combustion Fuel/tobacco combustion, consumer products, furnishings, construction materials, cooking...
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