AUSTRALIA, along with much of the developed world, has come a long way in reducing people’s exposure to lead.
In the 1980s, we were advised that our blood lead level should not exceed 25 mcg/dL. Today, Australia’s average blood lead level is estimated to be below 5 mcg/dL. This decline in population exposure to lead has been attributed to public health initiatives, such as restrictions on the addition of lead to petrol and in domestic paint.
In light of these achievements, does this mean that environmental exposure to lead is no longer an issue? A recent statement and information paper
by the NHMRC summarises the evidence on this important public health issue.
It states that the evidence is clear that a blood lead level above 10 mcg/dL can be harmful to health. Emerging evidence
indicates that blood lead levels below 10 mcg/dL are associated with reduced Intelligence Quotient and academic achievement, and behavioural problems in children, delayed sexual maturation in adolescent boys and girls, and increased blood pressure in adults.
Based on the latest evidence, the NHMRC statement recommends that sources of lead exposure be investigated and reduced where a person’s blood lead level is greater than 5 mcg/dL, particularly for children and pregnant women.
What should prompt a medical practitioner to do blood lead level testing, given that the symptoms for lead exposure are non-specific and common to many other clinical conditions?
Medical practitioners should request a blood lead test if there is a particular reason to suspect an individual has been exposed to lead, based on an environmental and occupational family history. In Australia, most non-occupational exposures to lead result from contact with lead-contaminated dust or lead paint when renovating older homes, furniture, cars or boats, or from contact with contaminated soil, particularly in areas with a history of high traffic flow.
Consideration should also be given to children’s developmental stages and behavioural patterns, particularly hand to mouth activities and pica-like behaviour, which increase the potential risk of lead exposure through ingestion. Lead exposure also needs to be considered when people participate in hobbies such as recycling batteries, casting lead sinkers or motor racing.
Symptoms of high lead exposure, ie, greater than 10 mcg/dL, may include constipation, abdominal pain, anaemia, headache, fatigue, myalgia and arthralgia, anorexia, sleep disturbance and difficulty concentrating. It is worthwhile considering a blood lead test where reduced IQ, academic achievement or behavioural problems are present in a family member, especially if there are younger siblings or where the mother wishes to have another child, as a preventive strategy.
Most state or local health agencies usually have experts who can help investigate the source of lead, reducing the risk of exposure to others in the family.
If a patient’s test results show a blood lead level above 5 mcg/dL, it is critical to provide advice to the patient on identifying and removing sources of lead. A follow-up blood test after 3 months is recommended, along with testing other members of the household.
Testing of urine, skin, hair or fingernails is generally not accurate or clinically useful.
State and territory health agencies can assist in providing information to patients, and some jurisdictions require follow up of cases above a specified level. This is an opportunity for GPs to work in partnership with authorities to assist community members to reduce their exposure.
NHMRC’s advice is a great reminder to us of the influence of the built environment on our health. The potential to encounter patients who have been exposed to lead exists for inner city medical practitioners, just as it does for those GPs in lead mining and smelting communities who are at the front line in supporting lead management programs and identifying community members at increased risk.
While much has been achieved through public health initiatives, vigilance needs to be maintained.
Associate Professor Sophie Dwyer is the chair of NHMRC’s Lead Working Committee. Ewan McKague is an NHMRC staff member.