ELIZABETH CHEUNG
PUBLISHED : Tuesday, 28 July, 2015, 7:01am
UPDATED : Tuesday, 28 July, 2015, 11:13am
Kei Ching Estate residents collect water from temporary distribution points amid the lead scare. Photo: May Tse
A scandal involving unusually high levels of lead in three public housing estates has got the whole of Hong Kong talking. The Society of Hospital Pharmacists of Hong Kong has listed 10 frequently asked questions in light of the tainted water scare.
Q: Can lead be absorbed and accumulated in the body after one drinks water containing lead?
A: Part of the lead would be absorbed by the body after taking food or water containing lead. Adults absorb 10 per cent, while children absorb between 30 and 50 per cent. Lead that has not been absorbed would be excreted.
It takes around 30 days for lead levels in one’s blood to be reduced by half. Lead is carried by one’s blood to different tissues and organs, and around 90 per cent of lead (70 per cent for children) stays in one’s bones and teeth. It takes a long time for lead levels in one’s bones to be reduced, and the lead would gradually be released into one’s blood. Hence it is still possible for lead to appear in one’s blood even after ceasing consumption of water with lead. That said, the harm is small if lead stays in one’s blood.
Q: How does lead exist in water? What dietary recommendations, if any, are there to flush lead out of the body?
A: Lead can take on soluble or insoluble form in water. At present no international organisations have determined that drinking more water can hasten the flushing of lead out of the body.
Q: How do I know if the level of lead in my body is excessive?
A: The most common, convenient and reliable screening method is a blood test. Although the level of lead in one’s blood cannot reveal the full amount of lead in the body, international authorities such as the Centres for Disease Control and Prevention in the US use lead levels in blood as an indicator to assess the risks that lead poses to one’s health.
Q: What causes excessive levels of lead in blood?
A: People might come into contact with lead at work. They could include those in the construction industry who weld or cut materials containing lead; those in the recycling industry who reuse lead from batteries; or those who produce ammunition.
For others who typically do not encounter lead through work, they might come into contact with dirt polluted with lead; eat or drink lead-polluted food and water; or use paints, ceramics and drugs containing an elevated level of lead.
Smoking also increases lead levels in blood. Past research has shown that lead levels in the blood of smokers were 30 per cent higher than that of non-smokers. Inhaling second-hand smoke also causes higher lead levels. If children are affected by second-hand smoke, their risk of excessive lead levels is four times higher than those not affected.
Q: What are the symptoms of lead poisoning?
A: The symptoms of early-stage lead poisoning are not obvious. Primarily, effects are felt in the nervous system (fatigue, difficulty concentrating), digestive system (stomachache, nausea) and bones. Serious lead poisoning can lead to confusion, epilepsy and coma.
Q: What long-term impact can lead have on the body if it is absorbed over a sustained period? When blood lead levels have dropped or resume a normal level, does such impact persist?
A: For children, those aged six or younger are particularly vulnerable to lead exposure. Prolonged absorption or intake of lead might affect brain development, leading to diminished intelligence, poor concentration, behavioural problems or even hyperactivity disorder. Even if lead in one’s blood returns to normal levels, the impact on one’s nerves and behaviour might not be reversible. Other effects include anaemia and hearing damage.
For adults, prolonged intake of lead can prompt an increase in their blood level and a higher risk of cardiovascular diseases. Such exposure might also affect kidney function and the reproductive system. Serious cases might affect the nervous system and accelerate a degeneration of cognitive ability.
For pregnant women, excessive lead levels could induce hypertension in pregnancy, premature birth, miscarriage, or lower birth weight for the baby.
Q: If breastfeeding mothers have consumed water with excessive lead levels, should they continue to breastfeed or switch to baby milk formula?
A: The US Centres for Disease Control and Prevention stated that lead should comprise no more than three per cent of the mother’s bloodstream as she produces breast milk. If a mother’s lead level has not exceeded 40 micrograms per 100 millilitres of blood, she should be deemed able to continue to breastfeed her children. If mothers are relying on baby milk formula, they should prepare it with distilled water or filtered tap water.
Q: Is there any medication that can cure lead poisoning?
A: If there is no more than 50 mcg of lead in 100 ml of blood, it is typically advised to simply observe one’s condition and stay away from lead. If there is more than 50 mcg of lead per 100 ml and obvious lead poisoning symptoms appear, chelation therapy can be considered. Chelating agents combine with heavy metals in the body to result in soluble chemical compounds and are excreted through urine.
Q: What filtering appliances can reduce lead in water?
A: Find out whether an appliance has received any internationally-recognised certifications. If an appliance has passed the NSF53 standard set by the National Sanitation Foundation in the US, it can reduce lead to between 0.01 and 0.015 milligrams per litre of water.
Q: How long should I let water run before consuming it?
A: Various factors, such as PH value as well as the velocity of water and how long it has been kept in pipes, affect lead levels in water. Hence different suggestions apply to buildings depending on their respective pipe structures, storey heights and patterns of water usage.
http://m.scmp.com/news/hong-kong/health-environment/article/1844179/worried-about-lead-your-drinking-water-ten
