Swimming pool imperfections: Disinfection by-products from skin and urine

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  • Published: Jul 16, 2012
  • Author: Steve Down
  • Channels: Base Peak
thumbnail image: Swimming pool imperfections: Disinfection by-products from skin and urine

Surplus to requirements

New disinfection by-products identified in swimming pools are mainly halophenols and halonitrophenols that originate from the chlorination of human urine and skin, so swimmers should avoid urinating in the water, say Chinese researchers

People visit swimming pools for exercise and fun and don’t expect to get back home less healthy than when they left. But it can happen over the long term, due to the formation of unwanted chemicals in the water which are neurotoxic and cytotoxic and have the ability to cause asthma and cancer. What’s more, these compounds are produced during the disinfection process which is meant to protect swimmers.

Chlorine is added to swimming pools to kill off microorganisms that might cause infections if they are ingested. However, it also produces a series of compounds called disinfection by-products (DBPs) which are harmful, including nitrosamines, haloacetic acids and trihalomethanes, as reported previously in spectroscopyNOW.com and separationsNOW.com.

Now, a team of scientists from Hong Kong has discovered a new set of DBPs in disinfected swimming pool samples which also have the potential to be harmful to humans. Xiangru Zhang and coresearchers from the Hong Kong University of Science and Technology and the University of Hong Kong also found that they might originate from human body fluids like urine and sweat, as well as human skin.

Probing pool water

In the first set of experiments, Zhang looked for new halogenated compounds in water collected from indoor and outdoor swimming pools using an LC/MS/MS method. Bromide ions are commonly found in water around the world, at levels ranging from 100-2000 µg/L, but were only present in these pool waters at 6 µg/L, so the samples were spiked with bromide to amplify the detection of possible brominated DBPs.

The separated compounds eluting from the HPLC column were subjected to electrospray ionisation and precursor ion scans of m/z 79 and 81 to identify bromine-containing ions, backed up by selected ion scans and multiple reaction monitoring to confirm retention times of the molecular ions and provide structural information. The presence of suspected compounds was confirmed by comparison of the spectra and retention times with standard compounds.

The origins of the new compounds were checked by chlorinating water containing various human body substances, including urine, sweat, saliva and hair, using electrospray mass spectrometry to check the product structures. Similarly, samples of fresh human skin donated by the Department of Anatomy at the University of Hong Kong were also chlorinated and the products were analysed by GC with electron capture detection.

Use the toilets

Many brominated compounds were found that are new to the swimming pool scenario. Not all of them were fully identified but those that were included 2-bromophenol and 2,4-dibromophenol. Other identified halophenols included 2,4-dichlorophenol and some nitro derivatives like 2,6-dibromo-4-nitrophenol, 2,6-dichloro-4-nitrophenol and 2-bromo-6-chloro-4-nitrophenol.

The nitro compounds rang alarm bells with Zhang because they are reported to be more toxic than their non-nitro analogues. They were not discovered in tap water that had total organic carbon levels similar to the pool water, implying that they might originate from the swimmers. The subsequent analysis of the chlorinated human body substances confirmed that urine and sweat are probable sources. Both fluids contain phenols which could undergo chlorination and/or bromination in the pool.

A further source is the skin. Chlorination in the lab produced haloacetic acids, trihalomethanes and many brominated DBPs which tended to be of higher molecular weight than those produced from urine.

In order to see what effect these newly identified DBPs might have on the swimmers, the researchers carried out permeation tests on fresh human skin. The average permeation rates for 2,4-dibromophenol, 2,4-dichlorophenol and 2-bromophenol were 0.031, 0.021 and 0.023 cm/h, respectively. This equates approximately to permeated amounts of 74, 45 and 62 ng/20 cm2 skin of each compound for a typical swim of 2 hours.

Based on their results the team proposed a few recommendations for swimmers. They should avoid prolonged swimming and take frequent showers to prevent permeation of the DBPs through the skin. While contact of hair and sweat with the water is difficult to avoid, swimmers could attempt to stop urinating in pools, to reduce one primary source of DBPs.

Related Links

Environmental Science and Technology 2012, 46, 7112-7119: "New halogenated disinfection byproducts in swimming pool water and their permeability across skin"

Article by Steve Down

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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