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Lead is harmful, particularly to young children, even at low levels in the blood.
Children, women of childbearing age and pregnant women should take special care to avoid breathing in or swallowing lead.
We have been using lead for thousands of years, and the reliance on lead has increased substantially since the industrial revolution. However, the dangers of lead to the human body are now well known, so lead is used less than it was in the past.
Lead poisoning affects virtually every system in the body — the central and peripheral nervous systems, kidneys and blood. Lead accumulates in a person's body throughout his or her lifetime; stored mostly in the bones.
The amount of lead in a person's blood gives an indication of how much lead has recently been breathed in or swallowed. These measurements are called blood lead levels. The results of a blood lead level test will usually be put in terms of how many micrograms of lead there are in each decilitre of blood (i.e. micrograms per decilitre).
There is growing evidence of intellectual impairment in young children with blood lead levels previously thought to be safe. Studies in Australia and overseas show a decrease in IQ in children aged 0-4 years with sustained blood lead levels greater than 10 micrograms per decilitre.
Pregnant women are also at risk as lead can be passed onto the unborn child through the placenta. Exposure of a foetus to lead levels is associated with developmental effects during the first two years of life. These can include effects on memory, learning and problem solving.
Children are likely to be playing either on the ground or outside in areas where they more readily come into contact with dust and soil. Young children absorb the lead by touching contaminated dust or soil and then putting their fingers or toys in their mouths.
Children's nervous systems are undergoing rapid change and are particularly susceptible to permanent damage. A child breathes and consumes more food and air in relation to their size than an adult does. Because of this, the amount of lead that a child breathes in or swallows is proportionally greater than for an adult.
In addition to that, 50% of lead swallowed by children moves directly into circulating blood and thus from organ to organ. Adults retain only around 10%. Lead also stays in red blood cells much longer in children than adults.
The majority of children with elevated blood lead levels have either mild symptoms or no symptoms at all. Exposure to lead may cause very general symptoms such as headaches or stomach aches.
Epidemiological studies have shown that blood lead levels of between 10 and 25 micrograms per decilitre can adversely affect children in a variety of ways, usually with no overt signs or symptoms of lead poisoning including:
Children with moderate exposures, i.e. blood lead levels of between 30 and 50 micrograms per decilitre, are at an even greater risk of requiring special education, dropping out of school, and having reading disabilities as a young adult. Higher concentrations of lead on the nervous system can result in irreversible mental retardation and seizures, intermittent abdominal pain or constipation, coma and even death.
Anaemia may occur with moderate exposure (up to 90 micrograms per decilitre), but it is rarely severe. Sub clinical effects on haemoglobin synthesis may occur in children experiencing mild to moderate exposure.
Adults who are exposed to lead can have all the same problems as children.
In addition to that, adults with high levels of lead (e.g. from occupational exposure) are at increased risk of peripheral neuropathy (diminished nerve conduction velocity) and reproductive sequelae (reduced fertility in women and affected sperm morphology and function in men).
The Government's principal health advisory body, the National Health and Medical Research Council (NHMRC), in June 1993 emphasised its concern about human exposure to lead. It called for urgent action, which has happened, to reduce lead exposure, particularly from leaded petrol emissions and from the disturbance of lead-based paint.
The NHMRC established a set of action guidelines for managing the health risks of environmental lead, with a goal for all Australians to have a blood lead level below 10 micrograms per decilitre.
Phone the Department of the Environment and Heritage's Community Information Unit on 1800 803 772.
Factsheets on lead in the environment, ceramic ware, pottery, and marine, house and automobile paints are available also from this number.
See also our website at http://www.deh.gov.au/settlements/chemicals/index.html.