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Child lead levels down but risks remain

Woman working in a laboratory.
Credit: iStock.com/Jovanmandic

A study into lead levels in Australia’s children has shown they are dropping, however results indicate children risked higher blood lead levels if they lived in a home older than fifty years or were of lower socioeconomic status.

When it comes to lead levels in Australians, whether they are young or old, the guidelines issued by the National Health and Medical Research Council (NHMRC) are clear. It recommends that people with blood lead levels exceeding 5 micrograms of lead per decilitre of blood (μg/dL) should be investigated and reduced. However, there two problems with this figure: first, it’s new, and second, we don’t actually know what the lead levels are in the majority of the Australian population.

“During the time this study was underway, the national guidelines from the NHMRC dropped from 10 micrograms of lead per decilitre of blood (μg/dL) being the figure triggering action, to the current 5 μg/dL figure,” says Dr Christos Symeonides, a paediatrician, post-graduate research scholar and lead researcher in a study conducted by the Murdoch Children’s Research Institute (MCRI).

“We were interested in if we could work out which children were at risk of high lead levels,” he says.

In the study, the result of which were recently published in Medical Journal of Australia, researchers measured the blood leadlevels in 523 of 708 preschoolers averaging four years old. All were from the Barwon region in and around Geelong, Victoria, a location chosen in part because it was representative of the general population in Australia.

“It’s exciting because up until now the monitoring we have had in children was of children in high risk areas, like Mount Isa in Queensland, or Port Pirie in South Australia, which have direct links to the lead industry,” Dr Symeonides says.

In those communities, researchers knew that lead levels are above the new cut off for “significant proportions of children”. 

This study helped determined what lead levels might be for children in the broader population.

“The primary thing we were interested in was, ‘Have blood levels come down?’ The secondary thing we were interested in was: ‘Can we work out which kids are at risk of higher levels? Are the old risk factors still relevant, and are there any new risk factors we need to think about?’ he says.

What researchers learned and where the risks lay

The study delivered researchers a number of clear findings. First: blood levels in children in the general population have come down since the last time they were checked (2005, when accepted lead levels were much higher than today’s modern standards). Second: there’s potential for levels to come down even further, so now is not the time to relax. And third? These lower lead levels are an excellent comparison point for those in the high-risk communities.

After analysing the data, researchers also found that children in the general population risked higher blood lead levels if they lived in a home older than fifty years or were of lower socioeconomic status.

“The relationship between socio-economic disadvantage and higher blood lead levels, although perhaps unsurprising, is nevertheless worrying from both the health and social justice perspectives,” says Dr Symeonides.

For the children in the study, their risk of higher blood lead levels also increased with their proximity to living near a historical industrial source of airborne lead

“Although that’s nothing like the kind of airborne lead that comes out of direct-lead associated industry, it nevertheless is an important source in Geelong’s history,” says Dr Symeonides.

The dangers of lead in older and renovated homes

The discovery that increased lead was seen in children living in older houses drives home the fact that Australians still need to be vigilant about the presence of lead in older homes.

“Particularly, we should be thinking about paint: old household paint used to contain sizable quantities of lead,” says Dr Symeonides.

The date to be aware of is 1965. That was when laws were changed to require paint to contain no more than one percent of lead. The study clearly showed the difference in lead levels in preschoolers living in older homes.

“Kids picking things up off the ground (and putting them in their mouths) had higher lead levels if their house was more than fifty years old,” he says. 

The same pattern emerged if the children had a sandpit and lived in an older house: their lead levels were higher than those with a sandpit living in a newer house.

Researchers also confirmed that renovating older houses increases the lead levels of its youngest occupants.

“We didn’t see that in renovations of new houses,” he says.

Luckily, it seems there’s another easy way to keep the lead levels down for children living in older houses: those who bathed more regularly had a lower lead count.

“That reinforces that the lead is probably coming from the dust, soil, sand or paint that remains contaminated by historical household sources, and they are washing it off,” Dr Symeonides.

How high levels of lead impact children’s health

Although everyone has a little bit of lead in their system, higher lead levels clearly correlate to increased behavioural problems, lower IQ levels and improved academic achievement.

These detrimental impacts seem to be linked to a sliding scale that has no “safe” or optimal lower limit: children with lead levels of ten will do better than those with lead levels of 20, while those with lead levels of five will do better still than children with lead levels of ten.

“Looking at the research, we consistently see better outcomes for children with lower lead levels, and – as lead levels decrease and studies can look lower and lower – so far those benefits continue as low as we are able to assess,” Dr Symeonides says.

For Dr Symeonides and his colleagues, the conclusion of their research is clear: minimising children’s exposure to lead remains essential, and while there’s no official optimal lower limit, he suggests the following target.

“The lower the better,” he says.