Lead Exposure

Lead Exposure

Lead can reach the biosphere, including humans, by a number of routes. The main exposure routes to humans are:
Food – This is a major source of lead intake for the adult population. Produce can be ontaminated from airborne deposition and lead-rich soil, though this can be reduced with careful washing. Previously, leaded solders in cans and wine bottle capsules contributed to lead intake in the general population, but these have been phased out. In the home, the use of lead crystal or ceramic tableware glazed with leaded glazes can cause a small contribution, but such articles manufactured in the Western World are tested to ensure that leaching is acceptably low.
Water – Old lead pipes, which are still in place in many dwellings, can slowly dissolve in some soft and acidic waters. Improved water treatment to reduce plumbosolvency, reduces the lead content of water to acceptable levels in the majority of dwellings. However, the problem is not eliminated without replacement of lead pipes within the home, which incurs expense to the homeowner. A WHO guideline of 10μg/l for drinking water is complied with in most cases.
Air – Direct absorption by inhalation is a minor exposure route for most people, though it can be significant to individuals occupationally exposed. Airborne lead-containing particles fall to earth, most within a short distance of source, and add to lead contents of dusts, soils and food. A weak link between levels of lead in air and exposed populations has been established. The WHO recommended an air quality standard in 1987 of 0.5-1.0μg/m3. The EU lead in air standard is currently 0.5μg/m3 and the UK has set an air quality target of 0.25μg/m3. Air lead levels are falling in Western Europe, as leaded petrol is being phased out. Elevated levels can be found in some industrial areas.
Soil and dust – Ingestion of soil and house dust is a major pathway for the exposure of young children to lead, due to “hand-to-mouth” activity. The major source of lead in house dust in older properties is leaded paint (now phased out, but still in situ in many dwellings). This is the major source of lead exposure to children living in older dwellings in the USA. Other contributions to dust are from airborne emissions, particularly in countries where leaded petrol is still used. Lead contents in house dusts in urban areas of the UK are declining. Lead contents of soils cannot be expected to decline for many years, as lead has a low mobility in soil.
Lead exposure levels in the general population have markedly declined over the past 30 or so years and by the 1990s average national levels for blood lead in the EU were mostly well below 10μg/dl.
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