Lead can be harmful to people of all ages, but the risk is highest for unborn babies, infants and young children (under five years of age).
- Pregnant women pass lead to their unborn babies through their blood. In pregnant women, high levels of exposure may cause decreased birth weight or miscarriage.
- Small children are more likely than adults and older children to swallow small amounts of lead, as they put things in their mouths, touch and crawl on dusty surfaces indoors and outdoors, and touch their mouths more often.
- Children also absorb a higher proportion of lead than adults as their bodies and brains are growing and changing constantly.
- If adults and children swallow the same amount of lead, about five times more is absorbed into the body by children.
Once in the lungs or stomach, lead is absorbed into the bloodstream and is distributed to the liver, kidneys, lungs, brain, spleen, muscles, and heart, and can be stored in bones and teeth. Lead that has been stored in bones and teeth can be released many years after exposure.
Health effects as a result of lead exposure differ greatly between individuals. Things such as a person’s age, the amount of lead the person is exposed to, whether the exposure is over a short-term or a longer period, and the presence of other health conditions, will influence the individual symptoms or health effects. For example, an adult exposed to lead in the workplace over several years may show different symptoms and health effects than a child exposed over a short period, even if both have the same blood lead level detected on a blood test.
The National Health & Medical Research Council (NHMRC) has reviewed the findings of a comprehensive independent evaluation of the evidence on the health effects of lead.
The evidence found an association between blood lead levels less than 10 micrograms per decilitre and health effects, including reduced Intelligence Quotient (IQ) and academic achievement in children, behavioural problems in children, increased blood pressure in adults and a delay in sexual maturation in adolescent boys and girls. However, there is insufficient evidence to conclude that lead at this level caused any of the health effects observed.
The NHMRC advises that a blood lead level greater than 5 micrograms per decilitre suggests that a person has been, or continues to be, exposed to lead at a level that is above what is considered the average ‘background’ exposure in Australia. If a person has a blood lead level greater than 5 micrograms per decilitre, it is recommended that action should be taken to investigate the source of exposure and reduce it, particularly if the person is a child or pregnant woman.
Blood lead level indicator
On 19 May 2015, the NHMRC Statement: Evidence on the Effects of Lead on Human Health was released to provide advice to the community and to policy makers on this issue.
Health effects associated with blood lead levels of 10 micrograms per decilitre and higher
It is well established that blood lead levels greater than 10 micrograms per decilitre can have harmful effects on many organs and bodily functions. Effects such as increased blood pressure, abnormally low haemoglobin (the protein that carries oxygen around the body), abnormal kidney function, long-term kidney damage and abnormal brain function have been observed at blood lead levels between 10 micrograms and 60 micrograms per decilitre in adults and children.
Health effects associated with blood lead levels less than 10 micrograms per decilitre
The evidence for health effects occurring as a result of blood lead levels less than 10 micrograms per decilitre is less clear. NHMRC’s comprehensive review of the health effects of lead found an association between reductions in Intelligence Quotient (IQ) and academic achievement in children at blood lead levels less than 10 micrograms per decilitre. There is weaker evidence that blood lead levels less than 5 micrograms per decilitre are associated with reductions in IQ or academic achievement.
For blood lead levels between 5 micrograms and 10 micrograms per decilitre, an association was observed between higher occurrence of behavioural problems (poor attention, impulsivity and hyperactivity) in children, increased blood pressure in adults (including pregnant women) and a delay in sexual maturation or puberty onset in adolescent girls and boys.
The contribution of lead to the above health effects is difficult to determine. The effects of blood lead levels less than 10 micrograms per decilitre on IQ, academic achievement and behavioural problems is likely to be small, with stronger influences by other factors such as socioeconomic status, education, parenting style, diet, or exposure to other substances.