|CHAPTER 16: NOISE AND RADIATION - INTRODUCTION|
Pressures on the environment may occur through chemical, physical and biological agents. The subject of this chapter is physical agents, where physical fields are examined. The term physical fields is used here to encompass acoustic fields (noise and vibrations) and radiation and electromagnetic fields (ionising and non-ionising). These are considered below under three headings: noise, non-ionising radiation and ionising radiation.
Physical fields are part of the natural environment. Depending upon their properties and the surrounding conditions, physical fields are transmitted through the spaces in which we live, potentially affecting human health and nature. Human activity can add to, modify, and enhance and reduce the intensity of these fields. Furthermore, changes in physical fields can be linked to global environmental problems such as stratospheric ozone depletion (causing a potential increase in ultraviolet-B radiation) and climate change.
The ability to hear sounds is a sensory function vital for human survival and communication. However, not all sounds are wanted. 'Unwanted sounds', for which the term 'noise' is normally used, often have their origin in human activities (mainly transport, industry and households).
This chapter addresses environmental noise also referred to in the scientific literature as community, or residential, noise. Environmental noise is the noise experienced by people generated outside households. Noise experienced by people in the workplace or occupational environment is not considered in this chapter.
The results of an acoustic quality survey in European cities is presented in Chapter 10. The current section first concentrates on the concepts involved with the measurement of noise and vibration. This is followed by an assessment of the effects of noise on human health and nature, and then by a review of noise sources in Europe.
The availability and comparability of data on noise pollution in Europe are generally poor (Box 16A). Available data published by the OECD show that exposure to noise, which was fairly stable at the beginning of the 1980s, had increased by the end of the decade in some Western European countries (eg, France, Germany, The Netherlands, Switzerland) (OECD, 1991a). For sound levels Leq greater than 65 dB(A) (see Box 16B for a definition of Leq), exposure appears to have stabilised in some cases and increased in others. However, within the range 55 to 65 dB(A), exposure has significantly increased, apparently as a result of the fast-growing volume of road traffic . In the highly industrialised European countries such as Belgium, France, Germany, Italy, The Netherlands and the UK, but also Austria, the Slovak Republic, Spain and Switzerland, more than 50 per cent of the population is exposed to noise levels from road transport which are above Leq 55 dB(A), which is the level at which people become seriously annoyed during the daytime (WHO, 1993a).
Physical fields arising from non-ionising and ionising radiation are additional agents exerting pressure on organisms in the environment. Box 16D explains the concepts and terminology associated with such fields. Their effects on human health are examined briefly in Chapter 11. Some parts of the electromagnetic spectrum, such as gamma rays and X-rays from nuclear sources and electron beams, which have wavelengths less than 10-8 metres, are said to be ionising (ie, radiations and fields that have enough energy to produce ionisation of matter such as gases and biological matter). These are discussed below in the next section. Radiations with a wavelength longer than 10-8 metres are said to be non-ionising. These include electromagnetic fields and non-ionising ultraviolet (UV) radiation, which are discussed in this section. The effects of low-frequency electric and magnetic fields are included (especially below power transmission lines) as well as exposure to UV-B radiation. Microwaves are not covered in this overview.
Human-induced sources of electromagnetic fields are generally small when compared with natural sources. However, suspicion has been directed towards certain human-made frequencies and wavelengths which happen to be far greater than those occurring naturally, although evidence of health effects from EMF is insubstantial.
With respect to ultraviolet light, the evidence of biological damage from exposure is clear. Some epidemiological evidence suggests that certain frequencies and/or wavelengths may be associated with human health effects. However, much of this exposure for humans appears to be related more to choice of lifestyle (such as sunbathing) than to environmental factors. This may yet be exacerbated by the depletion of the stratospheric ozone layer, whose equilibrium has been disrupted by emissions of CFCs and halons (see Chapter 28).
There are a few other types of non-ionising radiation which have demonstrated human health effects, including high-frequency fields, ultrasound and laser light. Medical applications of all three of these have demonstrated clear diagnostic or therapeutic benefits. In human terms, exposure is presently significant only in the occupational context, which is beyond the general scope of this overview.
The energy level of some types of radiation is high enough so that when they interact with matter they cause the formation of electrically charged particles or ion-pairs and break molecular bonds. These so-called ionising radiations are by their nature potentially harmful to life; at high doses they can be lethal and at lower doses can cause genetic damage. Ionising radiation occurs naturally, and life on Earth has always been exposed to it. Human activities can, however, enhance exposure, and new sources have been created. The toxicity of radionuclides derives almost exclusively from the effects of the radiation which emanates from them, although some radionuclides, such as the isotopes of plutonium, are also highly chemically toxic.