The risks of lead poisoning and lead exposure
International Lead Poisoning Prevention Week takes place from 21 to 27 October 2018. Although there is wide recognition of lead poisoning, and many countries have taken action against it, exposure to lead, particularly in childhood, remains of key concern to healthcare providers and public health officials worldwide.
We spoke to Associate Professor Peter Stewart, chemical pathologist at Royal Prince Alfred Hospital, to discuss lead exposure and toxicity.
“Lead poisoning occurs when we accumulate the element lead in the body. It acts in the body through inhibiting enzymes which are essential for metabolic processes throughout the body. Of particular concern is the brain, but also bone, intestine, and blood - in particular the red blood cells,” said A/Prof Stewart.
Lead is a naturally occurring metal. It is still used in industry and historically was added to petrol and household paint. Lead is hazardous when taken into the body, either through swallowing or breathing. Young children, including unborn babies, are at the greatest risk of the health effects of lead exposure.
“It is important to distinguish between clinical lead poisoning and lead exposure. Lead toxicicity or lead poisoning is not common today. This is firstly because we have removed lead from petrol, so people living by highways or busy roads are no longer inhaling those fumes. Secondly, we don’t put lead in residential paint anymore so that has limited exposure. Also industrial laws have made workers in lead industries much safer. However, lead stays around forever, so old houses that were painted with lead paint can still be a source of exposure, especially when people are renovating houses. Although there is no longer lead in petrol, lead still remains in the soil next to roads etc.
“The circumstances where you would now see lead poisoning is in children who may have eaten lead paint. Interestingly, lead paint is actually sweet to taste so animals and children will often lick it. In locations close to lead factories, or where lead is being mined, you find that the people living there will have blood lead levels that are higher than average and children in those areas often have blood lead levels well above the safe cut-off.
“A common cause of lead poisoning in our community is medicine brought back from overseas. Quite often, there are high levels of lead in these medicines. Also, pottery may be lined with lead paint and people may use that to heat up food or to put candles in so they will get exposure through what they consume from the container or from the fumes. Sometimes you have to do a bit of detective work to see how lead poisoning has happened.
“It is lead exposure which people really focus on these days and in most states in Australia. If blood lead levels are found to be higher than average then that is a reportable disorder. So, if someone measures the blood lead in a child and the blood lead is above 5 micrograms per decilitre, which is actually quite low, then that gets reported to the public health unit. We do this because there is evidence to show that children with even low levels of blood lead have statistically lower IQs than that of their peers who have not been exposed to lead,” said A/Prof Stewart.
Symptoms of lead exposure can often be difficult to recognise. In cases where lead exposure is expected then a GP or medical specialist should be consulted.
“In terms of testing for lead exposure, the investigation of children is often targeted. For example if children live near where lead is mined, those children may be subject to periodic screening. Testing is not something which is generally done in the community, unless there is a particular reason why you might be concerned. For example, if their cat or dog has become ill and the vet suspects it could be lead. Often, we find that animals are the first ones to get sick and, therefore, this is one of the first signs that there is exposure to lead.”
The absorption of very high levels of lead into the body is considered a clinical emergency. Symptoms can include convulsions, stomach pain, vomiting and loss of consciousness.
“The primary method for diagnosing, monitoring and reporting abnormalities is to measure blood lead. If the blood lead levels are only mildly elevated, then we would look at locating and removing the source of the lead. If the blood lead level is high and the person is symptomatic, for instance, with headaches, nausea or convulsions, then these people are treated as a medical emergency. Lead is removed from the body through a process called chelation. We infuse chemicals or give them chemicals orally that bind to the lead and extract it from the body and excreted in the urine.
“The body could also have a large burden of lead which is not able to be mobilised as it is stuck away in bone, therefore chelation would not be able to remove it. Interestingly, there are clinical stories of people with significant lead exposure who would have lead locked away in their bones; if something then happened to them, for example they fractured their leg or arm then they would get acute lead poisoning because the lead would be released out of their bones into their brains and red cells,” said A/Prof Stewart.
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This article appeared in the October 2018 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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