Tracing the traces: Nanogram concentrations of a toxic compound detected in chlorinated tap water

( -- Drinking water can transmit a number of diseases, including typhoid, dysentery, cholera, and diarrhea, which can then spread explosively throughout an entire service area. To avoid this problem, drinking water must be disinfected. After treatment and disinfection, the water is usually safe.

To manage the disease risk until it reaches the tap, most waterworks throughout the world use chlorine or chlorine-containing chemicals for disinfection. Beneficial though the chlorination of may be, it does have one potential drawback: studies have suggested that there may be a connection between the ingestion of chlorinated and an increased risk of bladder cancer. Scientists at the University of Alberta in Canada have now revealed a chlorination by-product of great interest: As the team led by Xing-Fang Li reports in the journal Angewandte Chemie, they were able to detect traces of the dichloroquinone.

Chlorination has been use to disinfect water for decades. Through reactions with natural in the water, it can lead to formation of trace amounts of toxic by-products, such as chloroform and halogenated acetic acid derivatives. The maximum allowed concentrations of these substances were legally regulated some years ago. Newer studies have suggested that these substances are not likely to pose a cancer risk. Instead, other possible by-products, such as halogenated quinones, which may be present in treated water at previously undetectable concentrations, are now under suspicion.

Quinones are six-membered carbon rings with two bound by double bonds to opposite ends of the molecule, and they occur in some microorganisms. Quinones that also contain halogen atoms such as chlorine or bromine may react with DNA and proteins at very low concentrations, causing damage to organisms.

The Canadian team has now been the first to successfully identify a representative of this class of compounds, 2,6-dichloro-1,4-benzoquinone, in chlorinated drinking water. To accomplish this, the researchers had to develop a special analytical procedure based on liquid chromatography (LC), electrospray ionization (ESI), and tandem mass spectrometry (tandem-MS). In actual water samples, they used this technique to detect this compound in quantities of a few nanograms per liter of water. The toxicology of some chloroquinones indicates that they could pose a risk of .

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More information: Xing-Fang Li, A Toxic Disinfection By-product, 2,6-Dichloro-1,4-benzoquinone, Identified in Drinking Water, Angewandte Chemie International Edition 2010, 49, No. 4, Permalink:
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Citation: Tracing the traces: Nanogram concentrations of a toxic compound detected in chlorinated tap water (2009, December 23) retrieved 21 September 2019 from
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Dec 23, 2009
while true that dosage makes the poison .. humans consume a lot of tap water every day which if not immediately flushed out will leave deposits.

And like always it depends on the person by person.

Dec 23, 2009
"(Toxic chemicals which) may be previously undetectable concentrations." Now that we have more sophisticated measuring devices, must we be alarmed at every trace element we find? Do we need to worry about stuff that can't kill a lab rat because the rat couldn't possibly ingest a lethal dose during its lifetime? Where should the line be drawn?

Dec 23, 2009
Still, even at nano-concentrations, this equates to several molecules of toxin per fluid ounce. Adds up over a day/week/month.
Also to be considered is the fact that most processed beverages and foods also contain(essentially speaking) unaltered tapwater. We're consuming quite a bit more of these compounds than we think, on a daily basis.

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