No evidence of harm to babies from tap water
Publication Date:05/06/2008
You may have seen recent reports claiming that if pregnant women are exposed to the chlorine in tap water it could increase the risk of babies being born with birth defects. This sounds alarming, but we've taken a closer look at the research, which shows that there's very little to be worried about.
What do we know already?
Clean tap water is something we often take for granted, but proper sanitation was recently voted the most important medical breakthrough in recent history. Adding chlorine to water is one of the things water companies do to kill harmful bacteria.
One problem with chlorine is that it can react with dirt in the water and form chemicals called trihalomethanes (THMs). It's possible that these chemicals could be harmful, so the UK places limits on the amounts permitted in tap water. Water companies have to test for THMs and keep them below a certain level.
There's already been research on whether THMs could be linked to birth defects. Earlier this year, researchers from Imperial College London published a study that looked at more than 2.5 million babies born in England and Wales. It found "little evidence" of any link between THMs and birth defects. It also said that there was "no plausible biological mechanism" by which the chemicals could harm babies.
In a new study, researchers have now looked at nearly 400,000 babies in Taiwan, to see if exposure to THMs could be linked to birth defects.
What does the new study say?
In their write-up of the study, the researchers say there might be a link between THMs and some birth defects. But a closer look at the numbers from the study shows absolutely no proof of this.
When scientists analyse their results, they do a test of something called "significance". If a result is significant, it doesn't necessarily mean it's important. What it does mean is that there's a good chance of it being a "real" finding, rather than one produced by chance. A look at the results of the study shows that almost none of them are significant.
In other words, there's nothing in the study to indicate any risk to babies at all.
Where does the study come from?
The researchers were based at several universities in Taiwan, and at Birmingham University in the UK. It appeared in a free online journal called Environmental Health, published by a company called BioMed Central.
How reliable are the findings?
The study was done reasonably well. The main difficulty is that the results just don't mean what the researchers say they do.
There were some other problems too. For example, the researchers didn't look at whether the women in the study smoked when they were pregnant, drank alcohol, took medicines or had a high genetic risk of having a baby with birth defects.
What does this mean for me?
It's worrying to hear that everyday things could be potentially harmful. But in this case, there's no reason to worry. Several studies have looked at whether THMs in tap water could be linked to birth defects. Looking at all the studies together, there's no conclusive evidence of any risk.
What should I do now?
There's no need to do anything. The new study doesn't show any danger for pregnant women who drink tap water.
Water quality in the UK is monitored by an organisation called the Drinking Water Inspectorate. You can find out more about water quality in your area by contacting them on 020 7270 3370, or through their website (http://www.dwi.gov.uk).
From: Hwang B, Jaakkola JJ, Guo H. Water disinfection by-products and the risk of specific birth defects: a population-based cross-sectional study in Taiwan. Environmental Health. 2008; 7: 23. Available at http://www.ehjournal.net/content/7/1/23.
News Archive
© BMJ Publishing Group Limited ("BMJ Group") 2007. All rights reserved
This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
