Dr Tse Man-li says people should avoid unwashed vegetables, century eggs and shellfish such as clams, oysters and conches to minimize lead intake. Photo: HKEJ
Hong Kong citizens have been living in constant fear of lead poisoning since the discovery of excessive amount of the chemical in drinking water.
Nonetheless, the risk of acute lead poisoning remains low, based on the level of lead found in water samples.
People who have blood lead levels above the standard can have the long-term effects of lead on their health minimized with appropriate medical care and treatment.
Lead, which is present in the earth’s crust, was widely used in the past century to produce petrol, electrical batteries for vehicles, paints, etc.
Although Hong Kong has banned leaded petrol, there is still some chance of lead exposure in daily life.
For instance, consumption of contaminated food or lead-tainted food would not pose any real threat as small amounts of lead could be discharged through urination.
Lead is an unnecessary toxic substance. Overexposure to it will adversely affect the brain, kidneys, nervous system and cardiovascular system.
As the brain is the most vulnerable organ, fetuses and young children aged below six would suffer the most.
According to the US Centers for Disease Control and Prevention and the American Academy of Pediatrics, the acceptable level of lead in children under six, pregnant women and breastfeeding mothers should be less than five micrograms per 100 milliliters of blood.
For adults, there should be less than 10 micrograms per 100 ml. of blood.
Many countries have conducted research on the impact of lead on brain development and intelligence of children.
Groups with higher blood lead levels have poorer concentration and relatively lower intelligence quotient, according to researchers.
Those with five micrograms of lead per 100 ml. of blood have IQ five points higher than those with 10 micrograms per 100 ml. of blood.
Children under six, pregnant women and breastfeeding mothers are at risk, so priority is given to them for blood tests and follow-up treatment.
Blood testing is the only reliable method to measure lead intake in the human body.
Urine and hair samples are more easily compromised, so these tests are not recommended.
The most important thing is to identify the source of lead contamination and stop lead intake.
In blood tests, patients are repeatedly checked if their blood lead levels have dropped to acceptable levels.
If they remain higher than the standard, doctors may investigate other sources of lead contamination and further tests are taken.
Meanwhile, pregnant women should be admitted to hospital to prevent possible exposure at home.
Chelation therapy has been suggested for treating lead poisoning.
This is applicable only in acute cases where patients have blood lead levels 60 micrograms or above.
Therapy can increase the absorption of lead if people have not stopped lead intake.
They can take precautionary measures.
For example, they should avoid unwashed vegetables, century eggs and shellfish such as clams, oysters and conches.
They should not use colored crystal wine glasses as acidic drinks will dissolve the lead in pigments and will be hard to see.
Mothers, however, should not stop breastfeeding.
Breast milk, which at most contains 3 percent of the mother’s blood lead content, outweighs the risks in ensuring the health of newborns.
If mothers use instant formula, it should be prepared with boiled distilled water.
Never use mineral water as it increases the workload on infant kidneys.
This article appeared in the Hong Kong Economic Journal on Sept. 2.
Translation by Darlie Yiu
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