Contamination unlikely, but the agency is playing it safe
Grace Chua Straits Times 31 Oct 10;
Estrogen contamination in the water sources here may be unlikely, but Singapore's national water agency is not taking any chances.
Earlier this month, the PUB called a tender to test for estrogen compounds in water samples taken from reservoirs, canals, sewage and other inland water bodies. It previously monitored the chemical here every month - one of about 200 other organic chemicals it tests for - when the reclaimed Newater was introduced in 2003.
A few years ago, after finding no estrogen in drinking water, Newater or desalinated water, it dropped the monitoring frequency to twice yearly.
Organic chemicals, such as estrogen, are passed out in human and animal waste from natural and artificial sources.
Keeping these chemicals out of the water supply is vital as high levels of exposure can interfere with the body's natural hormones, and have been linked to reproductive defects in animals.
In Singapore, the use of estrogen medications is low because people here do not generally take to hormone-containing drugs, explained obstetrician- gynaecologist Christopher Ng of the GynaeMD Women's and Rejuvenation Clinic.
A mere 3 per cent to 5 per cent of women of child-bearing age use hormonal contraceptives, such as the Pill, while probably even fewer menopausal women use hormone replacement therapy, he reckoned.
But use of such medications is expected to rise in a generation or two, as people become more aware of and educated about them, he said.
But academics and PUB experts say leaks into the water sources here are not a big risk. While wastewater sometimes contains low levels of estrogens, it is not discharged into reservoirs.
Instead, wastewater flows through Singapore's deep tunnel sewage system to treatment plants, where it is treated and discharged into the sea.
Professor Ng Wun Jern, executive director of Nanyang Technological University's Nanyang Environment and Water Research Institute, explained that hormone concentrations in wastewater treatment effluent are typically low - from a few nanograms per litre to micrograms per litre. He added that drinking-water treatment processes, such as the reverse-osmosis membranes used in Newater and desalination, are able to filter them out.
But National University of Singapore environmental toxicologist Barry Kelly noted that endocrine-disrupting chemicals can leach into water from old sewage pipes and landfill sites. Some, such as flame retardants, are found in everyday household items and may also be present in air and dust.
'Some of these compounds may end up in reservoirs via atmospheric deposition and through run-off following rain,' he said.
Besides estrogen compounds, the PUB tests for certain persistent organic pollutants which do not break down easily and stay in the environment for a long time.
Dr Kelly explained that there is probably not much cause for alarm.
'Ultimately, it is the dose that makes the poison. Thus, while residues of these chemicals are undoubtedly present at low levels in our homes and in the environment, the question remains whether these levels are high enough to cause effects in people.'
