AN unpleasant smell in drinking water caused by chemical contamination has almost been cleared, Thames Water says.

Minute traces of chemicals 2-EDD (2-ethyl-5,5 dimethyl-1,3 dioxolane ) and 2-EMD (2-ethyl-4-methyl-1,3 dioxalane) present in the company's Walthamstow water works have caused 800 customers to complain about a foul smell and taste since February.

But Thames Water said that following further adjusting to its treatment processes to remove the substances from customers’ water, the traces have been reduced from 30 nano grams per litre of water, to 10 – which means the smell should have almost disappeared.

Simon Evans, a spokesman for Thames Water, said: “Our most recent tests indicate that the levels of these substances in water going to customers in north-east London have significantly reduced and are now almost undetectable.

“Although 800 of the 2 million customers served by our Walthamstow works have reported an unusual smell in their water since the start of February, this has never been a health concern.

“We’re really sorry to all those who’ve been affected. We are confident the problem is now almost completely resolved.”

The water company continues to investigate the source of the contamination, which is believed to have leaked into the River Lea.

The 2-EDD and 2-EMD chemicals are by-products of manufacturing processes, but the Health Protection Agency said they are not harmful in the concentrations found in the drinking water.

Principal lecturer in toxicology at the University of East London (UEL), Dr Winston Morgan, said: “Although there is limited information about these compounds, at the concentrations reported, about 10 to 30 nano grams per litre, there is no evidence that they are harmful following the short exposure reported in north east London.

“But there has been a study done on this and if people knew there was some chemicals in the drinking water, they started reporting a variety of symptoms.”

He continued: “As humans we evolved to avoid food and drink with unusual tastes and smells for our protection. If someone said, should I drink water that is unpalatable, I would probably say no.

"We expect our water to be pure, odourless and tasteless. There isn't necessarily anything wrong with it, but it doesn't feel right.”

Similar incidences of these compounds in the water supply have been reported before in the late 1980’s and early 1990’s in North and South America and in Worcester in the UK.

Click here to follow the Waltham Forest Guardian on Twitter