Chlorinated Tap Water and the Unborn Child
- All public water supplies have to be disinfected to protect public health.
- Chlorine is the most commonly used disinfectant and very occasionally a group of
chemicals called trihalomethanes (THMs) may be formed as a by product of the disinfection
process.
- There is a standard for THMs in drinking water. This is based on current World Health
Organisation guideline values and applies at the consumers’ tap. As with all health
related standards there is a large safety margin built into it.
- Water companies in England and Wales are required to meet the standard. They are also
encouraged to minimise the risk of THM formation BUT without compromising disinfection.
- There have been a number of studies carried out over the last 15 years, in Europe and
North America, looking at possible association between adverse pregnancy outcomes and the
levels of THMs in drinking water.
- A further UK study on chlorinated tap water and pregnancy outcomes was published on 21
October 2004. The study was carried out by the government- funded Small Area Health
Statistics Unit and looked at rates of stillbirth, low birth weight and very low birth
weight in relation to chlorination by-products in drinking water in three regions in
England. The three water companies involved in the study were United Utilities (covering
North West England), Northumbrian Water (Covering North East England) and Severn Trent
Water (covering the Midlands). The findings
of the report were discussed by the independent expert advisory Committee on Toxicity of
Chemicals in Food, Consumer Products and the Environment (COT).
- The Committee published a statement in November 2004, concluding that there is
insufficient evidence that the presence of chlorination by-products in tapwater increases
the risk to the unborn child. The Studies showed that, if there is any increased risk at
all, it must be small but more research was needed.
- The Committee again endorsed precautionary measures by water companies to minimise
consumers' exposure to chlorination byproducts in tapwater, providing that they do not
compromise the efficiency of disinfection of drinking-water.
- The report of the study is available at http://ehp.niehs.nih.gov/members/2004/7111/7111.pdf
.
Additional background information
Until the end of last year, the standard for THMs was 100 µg/l based on a three
monthly rolling mean. This has been tightened under the new Regulations to an absolute
standard of 100 µg/l in any sample.
In 2002, more than 11,700 regulatory samples were taken and 93 failed the standard.
When failures occur water companies are required to take action to optimise the treatment
process and prevent further failures.
NOTE – THMs are not likely to occur in all waters. The necessary organic
precursors have to be present and these are usually only found in appreciable quantities
in upland surface waters (ie coloured peaty waters) |
