Compound interestINTRODUCTION: Dr Rakesh Kanda looks at what our ...

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Compound interestINTRODUCTION: Dr Rakesh Kanda looks at what ourincreasing ability to detect very low levels of contaminants meansfor the environment and the water industry

Released : Monday, August 11, 2008 6:37 AM
Over the past decade there have been growing fears about thepresence of biologically active contaminants in the aquaticenvironment, such as endocrine disrupters, pharmaceuticals andpersonal care products. Emerging contaminants not only includethose substances in active or past production, but also theirmetabolites, other transformation products and chemical by-productsgenerated during production. The concern with these compounds isthe uncertainty about their ecological effects.
Recently, significant advancements in analytical technology haveenabled chemists to identify an increasing range of emergingcontaminants in the environment and to recognise them at lowerlevels than previously possible. As a result, environmentalscientists have started to monitor for environmental contaminantsin land, water and air. Predictably, studies carried out around theworld are identifying more of these compounds in the environment.
Some of these compounds have become subject to regulation,particularly those where there is significant data to suggest theycan cause adverse effects on wildlife or where these is asignificant risk to human health.
Some have been listed as "priority hazardous substances" and arecontrolled under the European Water Framework Directive. Theseinclude: pentabromobiphenylether (a derivative of the brominatedflame-retardant group and commonly used in household productsincluding fabric and furniture) C10-C13 chloroalkanes andsubstances used in paint, glue plastic and as a coolant, amongother things. There are also many other known emerging contaminantsthat need further research to understand their potentialenvironmental impact (see table).
The ecological effects of even very low concentrations of theseemerging contaminants remain unknown and further research isneeded. Nanomolecules are receiving attention at present due totheir size, which potentially enables them to integrate orinterfere with living cells. So the development of analyticalmethods to detect such materials is invaluable in determining theirrisk.
The effects of endocrine disrupting compounds (EDCs) continue to bethe subject of intensive studies worldwide. During the 1990s,research showed that the occurrence of intersex in male roach(Rutilus rutilus) was widespread in UK rivers and that intersex wasparticularly associated with discharges of treated sewage effluent.
Further work revealed that various natural steroid oestestrogensand the synthetic oestrogen used in the female contraceptive pillare responsible for most of the oestrogenic activity in domesticsewage effluent. It has also been found that the effects of thesesteroids can occur at very low levels, down to billionths of agramme per litre.
As a result of these developments, further work is needed to detectand measure the presence of these and other emerging compounds inwastewater, sewage sludge, surface and groundwaters at very lowlevels, to determine their fate and to establish backgroundconcentrations.
Continuing research into these compounds is expected to demonstratethat wastewater treatment using conventional techniques, such asactivated sludge plants, may not be effective at removing many ofthese contaminants. Advanced treatment may be needed to ensurethese compounds pose minimal deleterious effects to wildlife.Treatments that have been previously used to remove micro-?organiccontaminants from wastewater include: advanced oxidation (such asozonation), membrane filtration (for example, reverse osmosis),granulated activated carbon filters and membrane bioreactors.
Although advanced treatment technologies may prove to be effectiveat removing emerging contaminants, introducing them is expected tohave major cost implications to wastewater treatment plantoperations.
Pharmaceutically active compounds have recently been detected atvery low levels in drinking water. This has occurred where thesource water for drinking water treatment has been derived fromrivers and other surface water sources that have received adischarge from municipal wastewater treatment plants. A recentstudy of drinking water funded by the Associated Press and carriedout by the US geological survey and local water authorities foundpharmaceuticals or their by-products in treated drinking water,including medicines for pain, infection, high cholesterol, asthma,epilepsy, mental illness and heart problems.
Although the effects of the presence of these compounds on humanhealth are unknown, their presence in drinking water, even atconcentrations that are orders of magnitude below the normalprescribed dose, is worrying. So it is important that emergingcontaminants detected in the environment are frequently monitoredin drinking water.
Emerging contaminants have been discovered in the environmentworldwide. Unlike traditional priority pollutants, they may not betoxic, persistent or bioaccumulative but may produce subtleecological consequences, such as their reproductive effects onfish.
As analytical techniques progress, laboratories will play a keyrole in identifying which compounds are being released into theenvironment. They will help establish base line levels and willparticipate in studies concentrating on the removal of compounds bynew wastewater treatment technologies.
Further development in analytical protocols and the application ofanalytical technology will allow researchers to identify compoundsproducing biological effects and help evaluate the environmentalimpact of these emerging contaminants on wildlife and human health.In Europe, the WFD requires priority substances to be reviewedregularly and this research will enable the most appropriatecompounds to be included in the list of regulated substances. n
Dr Rakesh Kanda is principal research scientist at Severn TrentLaboratories. Email: rakesh.kanda@stl-ltd.com
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