Hong Kong's tainted water scare

Lead contamination should spur Hong Kong to review its water safety protocols

William Tse says while officials must act quickly to clean up the lead contamination in our tap water, society as a whole must review protocols to ensure better standards

PUBLISHED : Wednesday, 15 July, 2015, 1:31pm
UPDATED : Wednesday, 15 July, 2015, 1:31pm

The discovery of excessive lead in tap water at several public housing estates - plus the legionella bacteria at one estate - has raised public alarm over water safety in Hong Kong. In fact, the Water Supplies Department has strict guidelines on drinking-water quality, based on World Health Organisation standards. Basically, microbe content, radioactive substances, chemicals such as DDT, and heavy metals, including lead, are all tested for.

Based on the report from April 2014 to March 2015 of samples collected from different sites, including water treatment works, distribution networks and consumer taps, the lead content in drinking water is less than 0.001 milligram per litre, which is much lower than the WHO guideline. However, the contamination scandals at Kai Ching Estate in Kowloon City and two other housing estates show that the data might not be fully representative.

The major concern is the health risk. Lead is toxic, and lead poisoning can cause organ failure and affect brain development.

Some claim that a small amount of lead is nothing to worry about, as it is commonly found in the environment and in some plant products, such as herbal medicine and tea. However, the case at Kai Ching Estate is different and unusual. Although the level of lead in the water was not so high as to produce acute effects, there is no information about how long residents have been exposed to the contamination. Prolonged exposure of a small amount of lead may be harmful.

Lead contamination in water is almost always due to corrosion of pipes or solder containing lead, the use of which has been banned for decades. It is very unusual for such new estates to encounter these problems.

After the contamination was discovered at Kai Ching, water at the other estates served by the same licensed plumber, Lam Tak-sum, was also tested. So far, water from Kwai Luen Estate in Kwai Chung and Shui Chuen O Estate in Sha Tin was also found to contain excessive lead. One possible source of such widespread contamination might be the pipe materials; if lead was mixed in during the manufacturing process, more contaminated water samples may be found.

The coincidence of finding legionella contamination is a further stress for residents at the Kai Ching Estate. Legionella causes respiratory problems, which can be lethal. But the bacteria can easily be killed by boiling the water.

Either contamination, however, indicates possible misconduct with regard to the estates' maintenance and management. A task force has been set up to monitor the issue, and Chief Executive Leung Chun-ying has expressed concern. The government and the Housing Authority must find the source of the contamination and act fast to reduce public worries.

To tackle the legionella contamination, the authorities may disinfect the water storage tanks. In the case of lead, the contamination is much more difficult to handle as the source of the lead leakage is still not known. More importantly, the affected area is large and, given the lack of knowledge about the duration of residents' exposure, the scale of the problem remains a worry.

More blood tests should be arranged - particularly for the young - for those at the affected sites. So far, more than 400 blood tests have been scheduled. The results will clearly indicate how serious the issue is.

Further, if pipes are confirmed to contain lead, they must be removed and new pipes installed. This will takes time. In the meantime, residents could install a water filter on their tap to remove the lead.

The scandal is likely to make us question the water quality in our own estates. So now may be a good time to review the current policy to ensure better water safety. Should the government monitor the water more frequently? Or should the residents themselves find commercial laboratories to test water samples? What guidelines should we follow if contamination is found? All these things are now open for discussion.

Dr William Tse Ka Fai is a research assistant professor in the Department of Biology, Hong Kong Baptist University