LEAD IN AIR
LEAD IN AIR
Natural and anthropogenic sources of lead in the atmosphere and their dispersion have been discussed in Chapter 6. Direct inhalation of lead-bearing particles in air is one route of exposure for both humans and other animals. For most people, this is a minor exposure route, the majority of lead being taken in by ingestion (described later). However, leaded air particles fall to earth and contribute to lead levels in dusts, which can contaminate foods, hands, etc and thus be ingested. People exposed to lead fume at work can absorb significant amounts by inhalation if protective equipment is not worn and good working practices not followed.
The World Health Organisation set an air quality guideline for lead of between 0.5 and 1.0μg/m3 as an annual average (WHO, 1987), though a WHO working group recently recommended revising this guideline to 0.5μg/m3 (WHO, in press, cited in DETR, 1998). The EU lead in air standard is currently 0.5μg/m3. Ambient lead levels in air peaked in the early to mid 1980s in Britain. Annual average concentrations of airborne lead at the kerbside of a busy London road were around 1.4μg/m3, and in 1985 were still higher in Manchester (2.0μg/m3); general urban levels of lead were in the range of 0.2-1.0μg/m3. Since then, lead levels in urban areas have significantly declined, as the use of leaded petrol has been phased out. In the UK in 1995-6, the urban and kerbside lead levels measured were not above 0.2μg/m3, well within the WHO recommended levels. It is not expected that urban areas will now have lead levels above the lower WHO limit of 0.5μg/m3, though two industrial sites still exceeded this level. The upper WHO limit of 1.0μg/m3 was not exceeded at any of the 24 lead monitoring sites (chosen to represent urban, urban kerbside, rural and industrial locations) (UK DETR, 1998).
The relationship between lead levels in the air, and levels of lead absorbed by the body (blood lead levels) is complex, but evidence suggests that a standard for the general population should not be above 1μg/m3 (UK DETR, 1998). To allow for some individuals being more vulnerable, the UK Expert Panel on Air Quality Standards recommended a safety factor of 50% and a further safety factor of 50% to allow for uncertainties, resulting in a recommended value of 0.25μg/m3. It is believed at this level any effects on health, even to vulnerable individuals, will be too small to be detectable. This recommendation has, however, been criticised by industry as not being based on sound science.
The World Health Organisation set an air quality guideline for lead of between 0.5 and 1.0μg/m3 as an annual average (WHO, 1987), though a WHO working group recently recommended revising this guideline to 0.5μg/m3 (WHO, in press, cited in DETR, 1998). The EU lead in air standard is currently 0.5μg/m3. Ambient lead levels in air peaked in the early to mid 1980s in Britain. Annual average concentrations of airborne lead at the kerbside of a busy London road were around 1.4μg/m3, and in 1985 were still higher in Manchester (2.0μg/m3); general urban levels of lead were in the range of 0.2-1.0μg/m3. Since then, lead levels in urban areas have significantly declined, as the use of leaded petrol has been phased out. In the UK in 1995-6, the urban and kerbside lead levels measured were not above 0.2μg/m3, well within the WHO recommended levels. It is not expected that urban areas will now have lead levels above the lower WHO limit of 0.5μg/m3, though two industrial sites still exceeded this level. The upper WHO limit of 1.0μg/m3 was not exceeded at any of the 24 lead monitoring sites (chosen to represent urban, urban kerbside, rural and industrial locations) (UK DETR, 1998).
The relationship between lead levels in the air, and levels of lead absorbed by the body (blood lead levels) is complex, but evidence suggests that a standard for the general population should not be above 1μg/m3 (UK DETR, 1998). To allow for some individuals being more vulnerable, the UK Expert Panel on Air Quality Standards recommended a safety factor of 50% and a further safety factor of 50% to allow for uncertainties, resulting in a recommended value of 0.25μg/m3. It is believed at this level any effects on health, even to vulnerable individuals, will be too small to be detectable. This recommendation has, however, been criticised by industry as not being based on sound science.
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