Bottled water has been making inroads in Hong Kong and on the mainland. It is convenient for people who do not trust their water sources and drink only boiled water.
Hong Kong and the mainland lead the global pack in drinking bottled water. For several years, percentage growth of bottled water drinkers on the mainland has registered double digits, and it has continued to increase in Hong Kong, too.
The issue of bottled water is controversial, however. Some believe it is not well regulated and has pollutants or bacteria. Others warn that the plastic bottle may emit toxic substances.
Yet others worry about the lack of minerals in distilled water, the carbon footprint of the product and the potential for pollution by the bottles.
According to a study published last November in US magazine Environmental Health Perspectives, endocrine disruptors - chemicals that act like hormones and harm other hormones in the body - may infiltrate the content of bottles made of polyethylene terephthalate (PET).
Another study, at the Goethe University in Frankfurt, Germany, arrived at the same conclusion. The topic needs further research.
In June last year, Hong Kong's Consumer Council tested 40 samples of distilled, mineralised and natural mineral water. It looked for heavy metals, chemicals, pesticides and other pollutants.
Eight samples of natural mineral water were found to contain micro-organisms, including bacteria and fungi.
Although no guidelines have been set by the World Health Organisation or Hong Kong's Centre for Food Safety, doctors advise children, pregnant women, the elderly and people with weaker immunity to boil natural mineral water before drinking.
In one of the mineral water samples, the council also found more nitrate than what is set in the Codex Standard for Natural Mineral Waters. Two of the natural mineral water samples contained the heavy metal antimony, but not in dangerous amounts.
Again, neither the nitrate nor the antimony content is regulated locally.
Separately, the Food and Environmental Hygiene Department tested 130 samples between 2007 and last year and found all satisfactory.
While no scientific proof exists to show drinking natural mineral water regularly improves health, distilled water may contribute to tooth decay because it lacks fluoride.
As for mineralised water Bonaqua, Hong Kong-based producer Swire Coca-Cola says it adds 'quality minerals' after the purification process.
Swire declined to explain how it decides on the type and amount of minerals it adds to the water.
For those who, amid all these uncertainties, would rather boil their own water, K. K. Suen, senior engineer at the Water Supplies Department, assures them that Hong Kong's water could be drunk straight from the tap. 'People in Hong Kong enjoy the safest drinking water supplies in the world,' Suen said.
'All raw water, regardless of its source - rain water collected in local reservoirs or Dongjiang river water imported from Guangdong - undergoes a series of rigorous treatment processes, including coagulation, sedimentation, filtration and disinfection.'
Drinking tap water would also greatly relieve our landfill problem. Every day in 2008, the landfills received 75 tonnes of PET bottles from domestic sources and 34 tonnes from commercial and industrial sources, the Environmental Protection Department says.
But if you're really not ready to give up your bottled water habit, at least make the effort to recycle.
Read the other three parts of our bottled water series