drugs in the water (rsc)

8/8/2019 Drugs in the Water (RSC)

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Water quality

In short

Researchers firstdetected drugs ingroundwater and surfacewater in the 1990sMore recently, verylow concentrations ofcommonly-used drugshave been found indrinking water supplies

Traditional watertreatment plantsare not equipped toremove small, solublepharmaceuticalsAlthough advancedwater treatmentcould remove thesecontaminants fromwater, such technologyis very expensive and itremains unclear whetherthese low concentrationshave any effect on people

48 |Chemistry World |September 2008

Something

in the waterDrugs have been finding their way into our watersupplies for as long as they have been in use, soshould we worry? Maria Burke reports


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conurbations are likely to get thebiggest and most varied doses,and many studies across heavilypopulated areas of Europe haveidentified APIs in drinking water attrace levels. A number of reservoirsused for drinking water along the

Lergue River in Southern Francewere found to contain drugs includingparacetamol, the anti-inflammatorydiclofenac, and the epilepsy drugcarbamazepine.3 Clofibric acid anactive metabolite of many drugsused to lower cholesterol anddiazepam, which is often prescribedfor anxiety, were detected in treateddrinking water in Milan, Italy;4 andclofibric acid, propylphenazone, anddiclofenac were found in the drinkingwater of Berlin, Germany.5

In the US, a team from theSouthern Nevada Water Authority

Traditionalwastewatertreatmentplants are notdesigned toremove drugs

We take a huge number of drugs.So its not surprising that the drugsthat most people take most liberally painkillers, antibiotics, antiseptics,contraceptive pills and beta-blockers find their way into water supplies.It was back in the early 1990s thatresearchers first identified traceamounts of therapeutic drugs insurface waters and groundwater.This sounded alarm bells and, sincethen, surveys in Europe and the UShave found traces of around 100 ofthese compounds in surface waters,groundwater, sewage, effluent fromwastewater treatment plants, and,more worryingly, tap water.

Pharmaceuticals are usually non-volatile, water-soluble, and oftencharged molecules, and many ofthem pass through treatment plantsdesigned to get rid of traditionalpollutants. They have been lurkingin the environment for as long as

they have been in use, but its only inthe past decade or so that analyticalmethods have advanced enough todetect them at the low levels lessthan 1g/litre typically found in theenvironment.

Although these levels arebecoming easier to quantify, exactlyhow much of a risk they pose isa more complex issue. Activepharmaceutical ingredients (APIs)appear to affect aquatic species.This phenomenon hit the headlinesin the 1990s when research led byJohn Sumpter, an ecotoxicologist

at Brunel University in London,UK, linked the feminisation of malefish downstream of wastewatertreatment plants with the presenceof oestrogenic compounds, such asthe synthetic birth control compound17-ethinylestradiol.

In our drinking water, these drugsare found at extremely low levels aminiscule fraction of the amount ina medical dose. Yet there is emergingconcern about the potential humanhealth effects arising from complexdrug mixtures.

Last month, the US Environmental

Protection Agency (EPA) askedthe National Academy of Sciences(NAS) to provide scientific advice onthe potential risk to human healthcaused by the low levels of thesepharmaceutical residues in drinkingwater. The NAS will convene aworkshop of experts to advise theEPA at the end of the year.

Whats in your tap?

When people take a drug, only afraction is absorbed. The rest isoften excreted in unmetabolisedform, where it enters raw sewage.

The flushing of unused or expiredmedication down the toilet, and drug-containing waste from manufacturingfacilities are other routes by whichpharmaceuticals find their way intowastewater. The methods of disposalof unused drugs, from hospitals andother care facilities, is an area that theEPA recently stated its intention toinvestigate.

Many studies have confirmedthat some APIs pass throughwaste treatment plants and enterthe environment. A wide varietyof organic compounds, includingpharmaceuticals, have been found inwaterways across the US that receiveagricultural, domestic or industrialwastewater effluent.

In 2002, in the first nationwidestudy in the US, Dana Kolpin ahydrologist from the US GeologicalSurvey (USGS) in Iowa, foundcontaminants in 80 per cent of

sampled streams.

1

Among the mostfrequently detected compoundswere the steroids coprostanol andcholesterol, the insect repellantN,N-diethyltoluamide (DEET), caffeineand triclosan, an antimicrobialdisinfectant. The average numberof compounds in a given sample wasseven, but the researchers found asmany as 38 (out of the 95 targeted)compounds in one sample.

And as research delves deeper, newor emerging contaminants comeonto the radar of environmentalscientists. In one recent study Ed

Furlongs team from the USGSselected 54 target compounds,using drugs sales data as aconservative estimate of their likelyconcentrations, and by estimatingthe potential of these predictedconcentrations to cause biologicaleffects. They detected 38 of theingredients in at least one sample ofwastewater effluents and surfacewater.2

The problem is that wastewatertreatment plants in the US are notspecifically designed to remove manyclasses of trace level contaminants,

such as pharmaceuticals, explainsFurlong. And this is the case for themajority of wastewater treatmentplants throughout the world. Sopharmaceuticals are discharged intolakes and rivers and aquatic wildlifeis continuously exposed (see box

p50). From here APIs can leach intogroundwater aquifers, which area major source of drinking water.In some areas, treated municipalwastewater often laced with yetmore pharmaceuticals is also usedto top up raw water supplies.

This means that major urban

Cl

OOH

O

N

O

H

HH

HOH

H

OH

O

O

ClOH

ClCl

Mixtures of some of themost commonly-useddrugs have been found indrinking water

Chemistry World |September 2008 |49

Clofibric acid

DEET

Coprostanol

Ibuprofen

Triclosan


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Water quality

(SNWA) published a report last

November that analysed raw andtreated drinking water from 20full-scale drinking-water utilitiesand six water-reuse plants.6 Severalpharmaceuticals, including thetranquiliser meprobamate, theanti-epileptic phenytoin, the anti-inflammatory ibuprofen, and thex-ray contrast medium iopromide,occurred in more than 65 per cent ofthe treated water samples, althoughrarely at concentrations greater than10ng/l. The insect repellent DEETappeared in 90 per cent of treatedwater samples.

Slipping through the pipes

Conventional treatments fordrinking water are simply notdesigned to remove APIs. The reportby the SNWA also evaluated theeffectiveness of current drinkingwater treatment technologies andfound that no single process was ableto remove every chemical.

Conventional plants werecapable of removing about half ofthe compounds we evaluated, whileadvanced processes could eliminatenearly all of our target compounds,says Shane Snyder, an environmentaltoxicologist at the SNWA and the

reports lead author. The vast

majority of US utilities do not useadvanced treatment processes. Thebottom line is that while some of theseprocesses are extremely effective,they are also energy-intensive andexpensive to install. It would beunwise to move towards energy-intensive processes if there is notan actual [problem] to be solved.Whether there is a problem, or a realrisk, remains debatable.

The conventional process fordrinking water treatment plantsconsists of: coagulation (addingcoagulant salts and polymers to

Antidepressants as environmental contaminants

Ed Furlongs team at the US GeologicalSurvey in Iowa is particularly interested inantidepressants. There is huge potentialfor ever-increasing amounts of these drugsto find their way into water supplies as theyare so widely prescribed. The team looked atwastewater effluent and samples collectedfrom a stream containing wastewater.10 Typicalconcentrations of individual antidepressantswere in the ng/litre range except for

venlafaxine (Effexor), which was found ing/lconcentrations.

A major concern is that many antidepressantswork in similar ways, explains Furlong. Ifmultiple pharmaceuticals with the samemodes of action are present in an ecosystem,the additive environmental effect could besubstantial.

And research has already shown howantidepressants can affect fish. In one study,

fish living in a stream containing municipaleffluent were found to contain concentrationsof four antidepressants in their muscle, liver,and brain tissues. These levels are high enoughto possibly affect physiological systems, saysFurlong. Another study reported that certainantidepressants induced spawning in somecrustaceans and bivalves. More recently, threeantidepressants were found to be toxic to algaein laboratory experiments.

APIs have been found

in drinking water attrace levels in manyheavily populated areasof Europe includingBerlin, Germany (above)


STEFANBAUM/STOCKPHOTOS


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destabilise colloidal particles);flocculation (agitating coagulated

water to promote the aggregationof suspended materials); andsedimentation (where flocculatedwater is stilled to promote settling ofsuspended solids and floccules). Thewater is then usually chlorinated.

The SNWA team found thatconventional coagulation,flocculation, and filtration removedfew of the target compounds whenused at full scale. Other standardtreatments such as disinfection withultraviolet light, at typical drinking-water dosages, and ion exchange arealso largely ineffective.

Chlorine disinfection, on the otherhand, removed around half of thecompounds. Advanced treatmentssuch as ozonation oxidation usingozone proved extremely effective,removing most of the compoundseven at relatively low ozone doses.And UV combined with hydrogenperoxide was as effective as ozone.Similarly, activated carbon (AC) where pure carbon is heated topromote active sites which canadsorb pollutants worked well aslong as it was replaced or regeneratedregularly.

But even these tried, tested (andexpensive) advanced methods might

not be all they seem. As Snyder pointsout, whether a chemical is detected ina wastewater effluent depends on thedetection capability of the analyticalmethods used. In the US, there areno standard methods for analysingpharmaceuticals in water. So, we cantbe certain that our compounds arereally eliminated, or simply reducedto a concentration that is less than thecurrent detection limits, he says. Ifour detection limits had been partsper billion rather than per trillion,we would not have detected anypharmaceuticals in drinking water.

So as long as analytical proceduresand bioassay techniques becomemore sensitive and more readilyavailable, new contaminants willbe discovered. This poses a uniquechallenge for drinking watertreatment plants intent on removingorganic contaminants. Completeremoval is merely a reflection ofreporting limits, Snyder adds.

Stubborn drugs

Another factor in removal efficiencyis the API itself. How effective thesetreatments are seems to vary widely

depending on the type of compound,says Furlong. For example, somehydrophobic compounds arestrongly oxidised by free chlorine,and some hydrophilic compoundsare partly removed throughadsorption processes.

In the US, only a handful ofdrinking water utilities use advancedoxidation or membrane treatmentprocesses. Advanced treatmentssuch as AC and ozonation are morecommon in Europe, particularlyin Germany and Switzerland,although they dont tend to be usedin countries where drinking wateris extracted from groundwater,according to Marc Bhler of theSwiss Federal Institute of AquaticScience and Technology (Eawag).

In England and Wales, ozone andcarbon treatment processes are nowinstalled at many waterworks. TheDrinking Water Inspectorate (DWI)

of England and Wales publisheda study in June 2008 that foundthat most of the pharmaceuticalsstudied were removed by drinkingwater treatment systems whenthese included ozonation andactivated carbon. This combination,together with the more conventionalprocesses, can result in removal ratesof more than 90 per cent for a widevariety of pharmaceuticals, says SuePennison, principal investigator atthe DWI.

Technologies applied to treatwater sources contaminated with

agricultural runoff containingpesticides are often equipped withAC, ozone or tight membranefiltration (nanofiltration or reverseosmosis), says Adriano Joss, anengineering sciences researcherfrom Eawag. Plants equipped forremoving pesticides will inevitablyalso remove APIs to a big extent.

The use of advanced treatmentfor wastewater is still underdiscussion in Europe for those plantsdischarging either into ecologicallysensitive aquatic ecosystems orwhere there is significant water

reuse, says Joss. His team hascalculated that the additional costsof installing end-of-pipe treatmentin wastewater plants would costbetween 5 and 30 per personper year. In addition, advancedtreatment requires 1025 per centmore energy than conventionalwastewater treatment. But accordingto an ongoing full-scale study atEawag, the energy requirement forozonation per person equivalentcorresponds to less than three wattsof power. And, as Joss points out,many electronic devices on standby,

Many pharmaceuticalscan be removed with

advanced watertreatments such asozonation

The little weknow aboutthe impactsof humanexposuregives cause forconcern

Chemistry World |September 2008 |51

UNITEDWATER


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Water quality

such as video recorders or coffeemachines, consume more thanthat. It is a matter for public debatewhether society wants to spend themoney necessary to put in advancedtreatments. The amounts are feasibleif the public persuade politicians thatthey want it, he believes.

At what cost?

Is there a case to be made for

this investment? APIs havebeen associated with worryingdevelopmental effects in aquaticwildlife, not just in the relativelyAPI-rich environment downstreamof treatment plants, but atconcentrations usually consideredto be harmless, according to SushilKhetan and Terrence Collins,chemists from Carnegie MellonUniversity in Pittsburgh, US. Weknow almost nothing about theimpacts of human exposure to low-dose mixtures of pharmaceuticals,or of low-dose pharmaceuticals

mixed with other low-dose syntheticpollutants, but the little we do knowgives reason for serious concern,they wrote in a 2007 review article.7

But while there is no clear evidenceof any threat to human health fromsuch low levels of pharmaceuticals,the complex mixtures presentin water are new challenges fortoxicologists. Italian researcherswere among the first to examinethe effects of a drug mixture atenvironmental levels on humancells. They reported in 2006 thata combination of pharmaceutical

compounds inhibits the growth ofembryonic kidney cells in laboratorytests. Francesco Pomatis team atthe University of Insubria in Varese,Italy, designed a cocktail of 13 drugs including several antibiotics,ibuprofen, and a cancer medicine to mimic the mixtures found inseveral Northern Italian riversand in wastewater.8 Although theresults did not prove conclusively

that synergistic or additive effectsexist between drugs in the mixture,they fuelled speculation that suchinteractions are present.

Another concern is how longthese compounds could lastin the environment and watersupplies. Some drugs, such asantiepileptics, are persistent; othersare pseudopersistent, meaning that,while they degrade at reasonablerates, they are continuously beingreplaced. And around 30 per centhave high fat solubility, according toKhetan and Collins, which means

they can bioaccumulate enteringcells and moving up food chains,becoming more concentrated in theprocess.

Snyders team recently showedthat even advanced removal methodslike ozonation may not completelyremove some highly resilientchemicals.9 However, he believes thatthere is no appreciable human healthrisk at the concentrations foundin US drinking waters. For Snyder,the important point is that there arealways unknowns in addressing thethreshold for risk of any contaminant

in water. This is why we addsafety factors to any regulatorydetermination, he says. If thereare significant concerns regardingsynergy, the most logical decisionis to add another safety factor. TheWorld Health Organization recentlyaddressed this exact topic and statedthat the safety factors already inplace are largely adequate to addresspotential synergies.

However, Khetan and Collinsarent alone in their view thatpresence of APIs in water is anurgent issue for short- and long-termaction. And while these tiny tracespresent far more of a risk to aquaticwildlife than to humans, there is stillcause for concern. As yet, the trickytoxicology required to answer all ofthe questions about these very dilutebut complex drug mixtures has yetto begin.

Maria Burke is a freelance writerbased in St Albans, UK

Further reading

1 D W Kolpin et al, Environ. Sci. Technol., 2002,36, 1202

2 A L Batt et al, Anal. Chem., 2008, 80, 5021(DOI: 10.1021/ac800066n)

3 M Rabiet et al, Environ. Sci. Technol., 2006,40, 5282

4 E Zuccato et al, Lancet, 2000, 355, 17895 T Heberer, J. Hydrol., 2002, 266, 1756 SWNA report: http://www.awwa.org/Bookstore/

productDetail.cfm?ItemNumber=30697 S K Khetan and T J Collins, Chem. Rev., 2007,

107, 2319 (DOI: 10.1021/cr020441w)8 F Pomati et al, Environ. Sci. Technol., 2006,

40, 24429 M M Schultz and E T Furlong, Anal. Chem.,

2008, 80, 175610 S A Snyder, Ozone Sci.Eng., 2008, 30, 65

(DOI: 10.1080/0191951 0701799278)

Some drugs have beenassociated with worryingdevelopmental effects inaquatic wildlife

The complexmixtures ofdrugs present inwater are a newchallenge fortoxicologists


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