Pharmaceuticals, per!uorosurfactants, and other organic wastewatercompounds in public drinking water wells in a shallow sand and gravelaquifer!

Laurel A. Schaider !, Ruthann A. Rudel, Janet M. Ackerman, Sarah C. Dunagan, Julia Green BrodySilent Spring Institute, 29 Crafts Street, Newton, MA 02458, USA

H I G H L I G H T S

• We tested 20 public wells in a sand andgravel aquifer for 92 OWCs.

• Pharmaceuticals andper!uorosurfactantswere frequently detected.

• Septic systems are the primary sourcesof OWCs into the aquifer.

• Maximum concentrations of two pharma-ceuticals are as high as other U.S. sourcewaters.

• Nitrate, boron, and extent of unsewereddevelopment correlate with OWCpresence.

G R A P H I C A L A B S T R A C T

a b s t r a c ta r t i c l e i n f o

Article history:Received 1 July 2013Received in revised form 20 August 2013Accepted 20 August 2013Available online xxxx

Editor: Damia Barcelo

Keywords:GroundwaterNon-point source pollutionOrganic wastewater compoundsPharmaceuticalsPer!uorinated chemicalsSeptic systems

Approximately 40% of U.S. residents rely on groundwater as a source of drinking water. Groundwater, especiallyuncon"ned sand and gravel aquifers, is vulnerable to contamination from septic systems and in"ltration ofwastewater treatment plant ef!uent. In this study, we characterized concentrations of pharmaceuticals,per!uorosurfactants, and other organicwastewater compounds (OWCs) in the uncon"ned sand and gravel aqui-fer of Cape Cod, Massachusetts, USA, where septic systems are prevalent. Raw water samples from 20 publicdrinking water supply wells on Cape Cod were tested for 92 OWCs, as well as surrogates of wastewater impact.Fifteen of 20 wells contained at least one OWC; the two most frequently-detected chemicals were sulfamethox-azole (antibiotic) and per!uorooctane sulfonate (per!uorosurfactant). Maximum concentrations of sulfameth-oxazole (113 ng/L) and the anticonvulsant phenytoin (66 ng/L) matched or exceeded maximum reportedconcentrations in other U.S. public drinking water sources. The sum of pharmaceutical concentrations and thenumber of detected chemicals were both signi"cantly correlated with nitrate, boron, and extent of unsewered resi-dential and commercial development within 500 m, indicating that wastewater surrogates can be useful for identify-ing wells most likely to contain OWCs. Septic systems appear to be the primary source of OWCs in Cape Codgroundwater, although wastewater treatment plants and other sources were potential contributors to several wells.These results show that drinking water supplies in uncon"ned aquifers where septic systems are prevalent may beamong themost vulnerable to OWCs. The presence of mixtures of OWCs in drinking water raises human health con-cerns; a full evaluation of potential risks is limited by a lack of health-based guidelines and toxicity assessments.

© 2013 The Authors. Published by Elsevier B.V. All rights reserved.

1. Introduction

Pharmaceuticals, personal care product ingredients, hormones, andother organic wastewater compounds (OWCs) are commonly foundin aquatic systems (Barnes et al., 2008; Benotti et al., 2009; Kolpinet al., 2002). Some OWCs, including hormones, alkylphenols, and

Science of the Total Environment 468–469 (2014) 384–393

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E-mail address: schaider@silentspring.org (L.A. Schaider).

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other endocrine disrupting compounds (EDCs), have been linked toreproductive effects in "sh and other freshwater organisms (Brianet al., 2007). In addition, there are concerns about human health effectsfrom OWCs in drinking water. While some assessments conclude thathuman health effects are unlikely at current exposure levels (Bruceet al., 2010; WHO, 2011), there are signi"cant uncertainties in theseassessments (Kumar et al., 2010) and growing evidence of EDC activityat low levels of exposure that are not apparent at higher levels(Vandenberg et al., 2012; WHO/UNEP, 2013).

Although 40% of U.S. residents rely on groundwater for drinkingwater (US Census Bureau, 2011; US EPA, 2009a), the presence ofOWCs has been much more thoroughly characterized in surface watersthan in groundwater. Shallow unconsolidated sand and gravel aquifers,which are prevalent through many parts of the U.S. (Miller, 1999), areespecially vulnerable to OWCs because their high hydraulic conductivi-ty and lack of con"ning layers permit in"ltration frompollution sources.This vulnerability is compounded in regions with onsite wastewatertreatment systems (e.g., septic systems and cesspools), which serve20% of U.S. households (US Census Bureau, 2011) and discharge OWCsinto the subsurface (Carrara et al., 2008; Godfrey et al., 2007). OWC re-moval by septic systems is highly variable and depends on treatmentconditions and OWC characteristics (Stanford and Weinberg, 2010;Wilcox et al., 2009).

In order to investigate the in!uence of OWCs from septic systems ondrinking water in a vulnerable aquifer, we have studied sources andtransport of OWCs in groundwater on Cape Cod, Massachusetts, USA.Cape Cod's sand and gravel aquifer is impacted by contamination fromseptic systems, which serve about 85% of residences (MassachusettsEOEA, 2004), and fromgroundwater discharge ofwastewater treatmentplant (WWTP) ef!uent via rapid in"ltration beds. Studies of the CapeCod aquifer have shown a high degree of persistence and long-rangetransport for some OWCs. Cape Cod's aquifer contains glacial depositsof "ne- to coarse-grained sand and gravel with low organic carbon(OC) content (0.001–1%) (Barber, 1994). We previously found hor-mones, alkylphenol ethoxylates (detergent metabolites), and otherOWCs up to 6 m downgradient of a septic system, especially underanoxic conditions (Swartz et al., 2006). We found four hormones andsix pharmaceuticals in Cape Cod kettle ponds, which are primarily fedby groundwater, with greater detection frequencies and maximumconcentrations in ponds downgradient of more densely populatedresidential areas (Standley et al., 2008). U.S. Geological Survey studiesof a 6-km long plume of WWTP ef!uent in the western part of CapeCod (reviewed by Barber, 2008) have shown persistence and minimalretardation of some organic pollutants such as tetrachloroethylene,1,4-dichlorobenzene, and sulfamethoxazole,while sorption and biodeg-radation limit the mobility of some non-polar organic compounds andsurfactants such as 4-nonylphenol (Barber et al., 1988, 2009).

The persistence of OWCs in the Cape Cod sole source aquifer has im-plications for drinking water quality and public health, but there hasbeen limited study of OWCs in the region's drinking water. We previ-ously detected bisphenol A and two alkylphenol ethoxylatemetabolitesin a study of alkylphenols and other phenolic compounds in Cape Codprivate wells (Rudel et al., 1998). Thirteen OWCs, including three phar-maceuticals and six organophosphate !ame retardants/plasticizers,were detected in a study of eight wastewater-impacted drinking waterwells (public and private) (Zimmerman, 2005). The presence of EDCsand other OWCs in drinking water is of particular concern on CapeCod, where breast cancer incidence is elevated relative to other partsof Massachusetts and the U.S. (Silent Spring Institute, 1997; StateCancer Pro"les, 2013). While estimated historical concentrations of ni-trate in drinking water, an indicator of wastewater in"ltration, werenot associated with increased breast cancer risk in a Cape Cod-wide ep-idemiological study (Brody et al., 2006), a more recent study with im-proved exposure modeling suggested wastewater-impacted drinkingwater was a risk factor for breast cancer in one region of Cape Cod(Gallagher et al., 2010). A limitation of these studies is that they relied

on proxy exposure measures or models; direct measurements of EDCsand other OWCs are necessary to more thoroughly evaluate potentialexposures to OWCs through drinking water and to better understandthe processes in!uencing OWC transport in sand and gravel aquifers,such as on Cape Cod.

With cooperation from nine Cape Cod public water supply districts,we tested rawwater samples from 20 public wells for 92 OWCs, includ-ing pharmaceuticals, hormones, and consumer product chemicals. Ourobjectives were: (1) to evaluate the presence of OWCs in Cape Cod pub-lic drinking water supply wells and compare their concentrations toother U.S. public drinking water sources; and (2) to evaluate whethersurrogates of wastewater impact (nitrate, boron, and unsewered devel-opment) can be used to inexpensively identify wells most impacted byOWCs. Characterizing the presence of OWCs in Cape Cod drinkingwaterwells can improve our understanding of the processes controlling OWCfate and transport in groundwater systems.

2. Experimental

2.1. Site selection

Nine of 17 public water supply districts in Barnstable County,Massachusetts, USA, participated in this study. In 2009, these nine dis-tricts operated a total of 80 wells, with 4 to 21 wells per district. Foreach of these wells, nitrate (NO3

!) data (2005–2009) were obtainedfromMassachusetts Department of Environmental Protection (MassDEP)as a surrogate of wastewater impact. Nitrate concentrations were avail-able at least once per year for each well. Wells were classi"ed as “low ni-trate” if all reported NO3

! concentrations from 2005 to 2009 were"0.5 mg/L and “high nitrate” if they exceeded 0.5 mg/L at least once dur-ing those "ve years. Background [NO3

!] in unimpacted Cape Cod ground-water is "0.2 mg/L (Silent Spring Institute, 1997); concentrations of"0.5 mg/L are considered minimally-impacted, and concentrations ofN2.5 mg/L are considered highly-impacted (Massachusetts EOEA, 2004).In this paper, [NO3

!] is expressed as mg/L NO3–N.The extent of residential development in well recharge areas was

also considered as a surrogate of wastewater impact, since 85% ofCape Cod residences rely on septic systems. GIS-based 2005 landcover/land use data, which included 33 land use types and had a0.5 m resolution, were obtained from MassGIS (Massachusetts IT Divi-sion, 2012). ArcMap (ESRI, Redlands, CA) was used to analyze land usewithin zones of contribution (ZOCs) established by MassDEP to repre-sent the maximum extent of recharge areas under extreme conditions(six months drought, maximum pumping rate). Wells with "20% resi-dential development were designated as having less-developed ZOCsand wells with N20% residential development were designated as hav-ing more-developed ZOCs.

Among the 74 wells for which we had [NO3!] and land use data, we

selected 20 wells with the goal of achieving a distribution of [NO3!] and

residential land use that mirrored the available wells within the nineparticipating districts, while selecting an equal number of wells (2 or3) per district (Fig. 1). The classi"cation of the 20 selected wells (andof the 74 available wells in parentheses) was: 10% (8%) low NO3

!/lessdeveloped; 15% (11%) low NO3

!/more developed; 30% (32%) highNO3

!/less developed; and 45% (49%) high NO3!/more developed. 2008

annual pumping rates for the 20 selected wells ranged from 30.7 to174 million gal perwell, with the exception of onewell thatwas of!ine.Table S1 provides additional information about the selected wells.

2.2. Sample collection

Raw (untreated) water samples were collected from spigots at eachwellhead, prior to any treatment, from20public supplywells in October2009. Samples were also collected from two distribution systems. Rawwater from Cape Cod public wells undergoes pH adjustment and, insome cases, "ltration and chlorination. Prior to sample collection, each

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well was run for at least 1 h and each spigot was !ushed for at least10 min. For OWC analyses, water samples were collected in 500-mL or1-L silanized, amber glass bottles that contained Na2SO3 for dechlorina-tion (although just one sample from a distribution system was chlori-nated) and were subsequently acidi"ed with HCl. No additives wereused for alkylphenol analyses. Samples for nitrate and boron analyseswere collected in 125-mL HDPE bottles without preservatives. Twentypercent of samples were QA/QC samples (two "eld blanks, two dupli-cates, one matrix spike). Samples were immediately placed on ice incoolers and shipped overnight to the laboratory.

2.3. OWC analyses

Target OWCs were selected based on previous detections in aquaticsystems, especially groundwater and drinking water, evidence of endo-crine disruption, and/or availability of an analytical method. Methodreporting limits (MRLs) for OWC analyses varied by four orders of mag-nitude, ranging from 0.1 to 1500 ng/L. Concentrations between limits ofdetection (LODs) andMRLswere reported only for alkylphenols. A com-plete list of target analytes and MRLs is provided in Table S2.

Details of analytical methods are provided in Appendix A Supple-mentary data. All analyses were conducted by Underwriters Labora-tories (South Bend, IN, USA), except alkylphenol analyses, whichwere conducted by AXYS Analytical Services (Sidney, BC, Canada).In short, samples collected for OWC analyses were extracted with asolid phase extraction (SPE) cartridge prior to analysis with eitherliquid chromatography or gas chromatography followed by massspectrometry. Isotopically-labeled surrogate compounds were usedto assess compound recovery and accuracy. Nitrate was measured

using ion chromatography and boron wasmeasured using inductive-ly coupled plasma mass spectrometry.

2.4. Surrogates of wastewater impact

We evaluated correlations between OWCs and several surrogates ofwastewater impact: NO3

!, boron (B), well depth, and land use metrics.Boron, which is present in soaps and detergents, has been used as awastewater tracer (Schreiber and Mitch, 2006) and exhibits con-servative transport in the Cape Cod aquifer (Barber et al., 1988). Previ-ous studies suggest background [B] in Cape Cod groundwater isbelow ~10 !g/L; LeBlanc (1984) reported 7 !g/L in an uncontaminatedgroundwater well, while Swartz et al. (2006) reported a minimum of16 !g/L in septic system-impacted groundwater with detectable levelsof detergent compounds.Well depthmay be an indicator of wastewaterimpact, since deeper wells tend to be better protected from contamina-tion sources (Verstraeten et al., 2005). Well depth data were obtainedfrom MassDEP.

The extent of residential and commercial development was charac-terized within well ZOCs and within a 500-m radius circular zonearound each well. Although actual recharge areas are larger and elon-gated in an upgradient direction (Barlow, 1994), 500-m radius circleshave been used successfully to correlate agricultural land use with[NO3

!] (Kolpin, 1997) and urban land use with volatile organic com-pounds in supply wells (Johnson and Belitz, 2009). For each ZOC and500-m radius zone, we used ArcMap to calculate the extent of residen-tial (%RES) and commercial (%COM) development. We calculated resi-dential development in two ways: as the sum of all residential landuse regardless of density and as a weighted average that incorporated

Fig. 1.Map of Cape Cod, Massachusetts, USA, showing the location of 20 public wells sampled in October 2009.

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average parcel sizes across multiple development densities (very low,low, medium and high densities and multi-family), expressed as anestimated number of septic tanks per acre. Total residential develop-ment was highly correlated with the weighted average (Spearmancorrelation coef"cients N0.95) and bothmetrics yielded similar correla-tionswith other parameters, so for simplicity, only results based on totalresidential development are presented. We used an online GIS-basedplanning tool,WatershedMVP (Cape Cod Commission, 2013b), to calcu-late the fraction of residential and commercial parcels connected bysewer to aWWTP, and adjusted %RES and %COM to include only parcelsserved by onsite wastewater treatment. For correlation analyses, weevaluated %RES and %DEV (%RES + %COM) in both ZOCs and 500-m ra-dius zones.

2.5. Statistical analyses and chemical databases

Correlations between parameters were tested using the non-parametric Spearman's rank sum correlation test. Correlations wereconsidered signi"cant for p b 0.05. To compare likelihood of sorption,octanol–water partitioning coef"cients (log Kow) were calculated for

each OWC using the KOWWIN program within U.S. EPA's EPI Suitepackage Version 4.0 (Meylan and Howard, 1995; US EPA, 2000).

3. Results and discussion

3.1. Nitrate and boron concentrations

Among the 20wells tested, our 2009 NO3!measurements suggested

that six wells had background or minimal impact (b0.5 mg/L NO3!), ten

showed moderate impact (0.5–2.5 mg/L NO3!), and four were highly

impacted (N2.5 mg/L NO3!). [NO3

!] varied from b0.1 to 5.3 mg/L and[B] ranged from b5 to 37 !g/L (Table S1). In all wells with background[NO3

!], [B] was also consistent with background (b10 !g/L). Median[NO3

!] was 1.0 mg/L, which is higher than the 0.69 mg/L medianamong all the wells in participating districts (2008 and 2009 data).

3.2. OWC occurrence

Eighteen OWCs were detected in at least one well (Table 1). Anti-biotics, per!uorosurfactants, organophosphate !ame retardants, andnon-antibiotic prescription drugs were the most frequently detected

Table 1Organic wastewater compounds detected in 20 public supply wells on Cape Cod, Massachusetts.

Chemical name CAS number Method reportinglimit (ng/L)

Number of timesdetected (% of wells)

Maximumconcentration (ng/L)

Health-based guidelinevalues (ng/L)

Maximum in other U.S. publicsource waters (raw water) (ng/L)!

Prescription drugsNon-antibiotics

Antipyrine 60-80-0 1 1 (5%) 1 NA b1e

Atenolol 29122-68-7 0.1 1 (5%) 0.8 70,000b 36a

Carbamazepine 298-46-4 1 5 (25%) 72 12,000b, 40,000j b11r, 2n, 9e, 51a, 156d, 190c

Gem"brozil 25812-30-0 0.5 1 (5%) 1.2 14,000b b13r, b15c, 4n, 17e, 24a

Meprobamate 57-53-4 0.1 4 (20%) 5.4 260,000b 73a

Phenytoin 57-41-0 2 4 (20%) 66 2000b 29a

AntibioticsSulfamethizole 144-82-1 1 1 (5%) 1 NA b50a

Sulfamethoxazole 723-46-6 0.1 12 (60%) 113 18,000,000b 2n, 12e, 41c, 58r, 110a

Trimethoprim 738-70-5 0.1 1 (5%) 0.7 6,700,000b b13r, 1n, 4e, 11a, 20c

Other OWCsDEET 134-62-3 5 1 (5%) 6 200,000i b500r, 16e, 110a, 410c

Organophosphate !ame retardantsTBEP 78-51-3 50 1 (5%) 50 NA 300r, 400f, 960c

TCEP 115-96-8 20 3 (15%) 20 3300p b500c, b500r, 260f, 530a

TCPP 13674-84-5 10 4 (20%) 40 150,000p 720a

TDCPP 13674-87-8 10 1 (5%) 10 NA b500r, 170f, 260c

TEP 78-40-0 10 5 (25%) 20 NA NA

Per!uorosurfactantsPFOA 335-67-1 10 2 (10%) 22 40k, 300g, 400q 31m

PFOS 1763-23-1 1 8 (40%) 97 200q, 300h 16n, 41m

Alkylphenols4-Nonylphenol Isomer mix 250 1 of 7 (14%) 20 J NA b5000r, 130a, 4100c

Abbreviations: NA = not available; J = estimated value, below method reporting limit; TBEP = tris(2-butoxyethyl) phosphate; TCEP = tris(2-chloroethyl) phosphate; TCPP =tris(chloropropyl) phosphate; TDCPP = tris(1,3-dichloro-2-propyl) phosphate; TEP = triethyl phosphate; PFOA = per!uorooctanoic acid; PFOS = per!uorooctane sulfonate.References:

a Benotti et al. (2009).b Bruce et al. (2010).c Focazio et al. (2008).d Guo and Krasner (2009).e Illinois EPA (2008).f Kingsbury et al. (2008).g Minnesota DOH (2008a).h Minnesota DOH (2008b).i Minnesota DOH (2012).j Minnesota DOH (2011).k Post et al. (2009).m Quiñones and Snyder (2009).n Tabe (2010).p US EPA Region 3 (2012).q US EPA (2009b).r Zimmerman (2005).! Source waters suspected to be contaminated by sources other than WWTPs or domestic wastewater sources, such as chemical production facilities, were not included.

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types of chemicals (Fig. 2). The most frequently detected chemicalswere sulfamethoxazole (antibiotic, detected in 60% of wells; MRL0.1 ng/L), per!uorooctane sulfonate (PFOS; per!uorosurfactant, 40%;MRL 1 ng/L), carbamazepine (anticonvulsant, 25%; MRL 1 ng/L), andtriethyl phosphate (!ame retardant/plasticizer, 25%; MRL 10 ng/L). Ofthe 20 wells tested, 15 contained detectable concentrations of at leastoneOWC, as did both distribution system samples. Ninewells containedmultiple OWCs, with up to 12 OWCs per well.

3.2.1. PharmaceuticalsSixty percent of wells contained detectable concentrations of at least

one pharmaceutical (most MRLs " 5 ng/L), with maximum concentra-tions ranging from 0.7 ng/L (trimethoprim) to 113 ng/L (sulfamethoxa-zole) (Table 1). Nine of the 54 target pharmaceuticals were detected,comprising three antibiotics and six other prescription medications.The average total concentration of detected pharmaceuticals in each sam-ple ("[pharma]) was 24 ng/L (median, 0.6 ng/L; maximum, 131 ng/L).These "[pharma] values likely underestimate actual pharmaceutical con-centrations because they do not include chemicals thatwere not includedin the laboratory analysis or those present below theMRL. To our knowl-edge, this is the"rst time that antipyrine (analgesic for ear infections) andsulfamethizole (antibiotic) have beendetected in a drinkingwater source,whereas the other detected pharmaceuticals have previously been re-ported in other U.S. public drinking water sources. Notably, concentra-tions of two pharmaceuticals exceeded any previously reportedconcentration in U.S. public drinking water sources. The maximum sul-famethoxazole concentration exceeded maximum concentrations in"ve other studies (Benotti et al., 2009; Focazio et al., 2008; IllinoisEPA, 2008; Tabe, 2010; Zimmerman, 2005), and two wells had higherphenytoin (anticonvulsant) concentrations than those found in theonly other study that tested for phenytoin (Benotti et al., 2009).

Pharmaceutical concentrations in groundwater were highly variableacross wells. The well with the highest sulfamethoxazole concentrationdid not have detectable concentrations of any other pharmaceutical,whereas the well with the highest carbamazepine concentration con-tained detectable concentrations of seven other pharmaceuticals. Theseresults may indicate a high degree of heterogeneity in loading fromlocal sources and/or spatial differences in hydraulic conductivity and bio-geochemical conditions, such as OC levels and redox status, that affectOWC transport.

Septic system ef!uent from residential and commercial develop-ment is likely the primary source of pharmaceuticals in groundwater,although other sources are possible. Cape Cod has "ve centralizedWWTPs, all of which discharge into groundwater; four of the wells wetested may receive ef!uent from one of these WWTPs. Other potentialsources of pharmaceuticals include onsite wastewater treatment formedical facilities and nursing homes. None of the 10 Cape Cod medicalfacilities and nursing homes with groundwater discharge permits(23,660–165,610 L/d design !ow; Cape Cod Commission, 2013a) arelocated within the ZOCs for any of our wells, although there may besmaller facilities that discharge within the ZOCs for some tested wells.

3.2.2. Per!uorosurfactantsSamples from four wells contained N10 ng/L PFOS (MRL 1 ng/L);

two of these also contained N10 ng/L per!uorooctanoic acid (PFOA;MRL 10 ng/L). Per!uorosurfactants are highly persistent in the environ-ment and are used in a range of consumer products, including foodpackaging, non-stick cookware, stain resistant textiles, paints and lubri-cants, andhave numerous commercial and industrial applications. PFOAand PFOS were detected in 66% and 48% of samples, respectively, in asurvey of European groundwater (Loos et al., 2010). In the U.S., elevatedconcentrations of per!uorosurfactants in groundwater have typicallybeen associated with production facilities (NJDEP, 2007; Shin et al.,2011), althoughWWTPs are also sources (Quiñones and Snyder, 2009).

The sample from one well had relatively high PFOS (97 ng/L) andPFOA (22 ng/L) levels despite moderate [NO3

!] and [B] (0.9 mg/L and16 !g/L, respectively), and a second well had moderately elevatedPFOS (16 ng/L) and PFOA (14 ng/L) despite nearly background levelsof [NO3

!] and [B] (0.3 mg/L and 11 !g/L, respectively), suggesting asource other than domestic wastewater. Possible sources include amunicipal airport and "re training academy that lie within the ZOCs ofthese two wells. PFOS, PFOA and other per!uorosurfactants are usedin some aqueous "lm-forming foams for extinguishing hydrocarbon"res and have been detected in groundwater and surface waters down-gradient of "re-training areas (Moody et al., 2003) and airports (Saitoet al., 2004).

3.2.3. Organophosphate !ame retardantsSamples from35% of testedwells contained at least one organophos-

phate !ame retardant (OPFR; MRLs 10–100 ng/L), with maximumconcentrations among the "ve detected OPFRs ranging from 10 to50 ng/L. OPFRs are used in many household products (e.g., plastics,textiles, furniture, electronics, and construction materials) and havebeen found in the low !g/L range in WWTP ef!uent (Reemtsma et al.,2008). Some OPFRs are persistent in the environment; for example,tris(2-chloroethyl) phosphate (TCEP) and tris(1,3-dichloro-2-propyl)phosphate (TDCPP) have been frequently detected in drinking watersources (Focazio et al., 2008; Kingsbury et al., 2008). Domestic waste-water is likely the primary source of OPFRs into the aquifer, althoughthere may be additional sources, such as runoff from construction sites(Andresen et al., 2004).

3.2.4. Compounds not detectedAlthough hormones, alkylphenols, musk fragrances, and caffeine

are all typically found in wastewater, we did not detect any chemicalsbelonging to these classes (LODs for alkylphenols: 0.7–9 ng/L; MRLsfor hormones, musk fragrances, and caffeine: 0.1–10 ng/L), aside froma single detection of 4-nonylphenol (4-NP; estimated concentration20 ng/L). We also did not "nd 45 of 54 pharmaceuticals or 11 of 16OPFRs thatwe tested for, even thoughmany of these have been detectedin other aquatic systems.

Hormones and alkylphenols have beenpreviously detected in ground-water and surface water on Cape Cod (Standley et al., 2008; Swartzet al., 2006) and other regions (Benotti et al., 2009; Loos et al., 2010)but were generally absent from the wells in this study. While Standleyet al. (2008) reported androstenedione, estrone, and progesterone in

Fig. 2. Detection frequencies and maximum concentrations of individual OWCs in 10chemical categories. The number in parentheses after each category name indicates thenumber of target analytes in that category. The numbers above each bar represent the per-cent of samples that contained each chemical type. ND= not detected.

388 L.A. Schaider et al. / Science of the Total Environment 468–469 (2014) 384–393

groundwater-fed ponds on Cape Cod at maximum concentrationsof 3.0–6.5 ng/L, we did not detect any of the eight hormones thatwe included in our analysis (including estrone and progesterone)above their respective MRLs (0.1–0.5 ng/L). Similarly, although 4-NP,octylphenol, and two NP ethoxylates (NP1EO, NP2EO) were found inCape Cod groundwater near a septic system leach pit (concentrationsup to 84 !g/L; Swartz et al., 2006) and in other groundwater studies(concentrations up to 11 !g/L; Loos et al., 2010), we detected 4-NPjust once, at a relatively low concentration, and we did not detect anyother alkylphenols. We did not test for NP ethoxycarboxylates (e.g.,NP1EC), which are themost common environmental degradation prod-ucts of long-chain NP ethoxylates (Ahel et al., 1987). Loos et al. (2010)found higher maximum concentrations of NP1EC than of NP inEuropean groundwater, and Swartz et al. (2006) observed formationof NP1EC, NP2EC, and NP in groundwater near a septic system.

Although caffeine has been among the most frequently detectedOWCs in other groundwater studies (Barnes et al., 2008; Focazio et al.,2008; Loos et al., 2010; Verstraeten et al., 2005) and has been suggestedas a marker of wastewater impacts in shallow drinking water wells(Seiler et al., 1999), we did not detect caffeine (MRL 10 ng/L) or itsmetabolite paraxanthine (MRL 5 ng/L). While surveys of groundwaterin the U.S. and Europe have reported caffeine concentrations up to130 ng/L, caffeine has typically not been detected above ~15 ng/L ingroundwater (Barnes et al., 2008; Focazio et al., 2008; Zimmerman,2005). In previous studies of Cape Cod groundwater, oxic groundwatersamples within 6 m of a septic system leach pit contained b5 ng/Lcaffeine, whereas groundwater with dissolved oxygen of b3 mg/Lcontained caffeine concentrations up to 1710 ng/L (Swartz et al.,2006). Seiler et al. (1999) did not detect caffeine (MRL 40 ng/L) inwastewater-impacted wells deeper than 10 m, even those with [NO3

!]above 10 mg/L. By contrast, caffeine has been detected much morefrequently and at higher concentrations (up to 6000 ng/L) in riversand streams (Kingsbury et al., 2008; Kolpin et al., 2002), suggestinggreater attenuation under oxic subsurface conditions than in oxic sur-face waters.

3.3. Factors in!uencing likelihood of OWC detection in groundwater

Evaluating the characteristics of the chemicals detected in the publicwells may provide insight into the factors that control OWC persistencein the Cape Cod aquifer. The absence of certain OWCs indicates one ormore of the following factors: (1) relatively high MRLs; (2) relativelylow concentrations in domestic wastewater; (3) effective removal dur-ing onsite treatment, (4) degradation in aquifer sediments; or (5) sorp-tion to solid phases during subsurface transport. MRLs varied over fourorders of magnitude (Table S2), and chemicals with relatively highMRLs are less likely to be detected. Other factors are discussed below.

Some chemicals may not have been detected because of relativelylow loading into domestic wastewater ef!uent. In some cases, thismay re!ect lowhousehold usage. For instance, nonylphenol ethoxylateshave been phased out of many laundry detergents (McCoy, 2007). Forsome OWCs excreted in human waste, primarily hormones and phar-maceuticals, the dominant forms in domestic wastewater may be hy-drophilic metabolites rather than the parent compounds analyzed inthis study (Reddy et al., 2005; Celiz et al., 2009). For instance, concentra-tions of the antilipidemic simvastatinwere lower than concentrations ofits hydroxy acid metabolite inWWTP in!uent (Vanderford and Snyder,2006). Similarly, endogenous estrogens are primarily excreted as morehydrophilic glucuronides and sulfates, which undergo varying degreesof deconjugation or degradation during wastewater treatment (Reddyet al., 2005). These transformations may partially explain why we didnot detect any of the eight hormones, nor 45 of 54 pharmaceuticals,that we tested in this study.

Treatment of septic tank ef!uent through soil absorption sys-tems and aerobic sand "lters may promote degradation of caffeine,paraxanthine, alkylphenols, hormones, and other OWCs before ef!uent

reaches groundwater. Soil absorption systems were shown to removeN99.9% of caffeine and paraxanthine (Godfrey et al., 2007) and N97%of total nonylphenols (Huntsman et al., 2006), and aerobic sand "lterswere shown to remove N90% of three steroid estrogens (Stanford andWeinberg, 2010). Many Cape Cod septic systems include sand-basedsoil absorption systems that may effectively reduce loading of caffeine,alkylphenols, and hormones into the aquifer.

While the relatively low OC content of the Cape Cod aquifer maylimit microbial activity, some OWCs in this study likely undergo sub-stantial biodegradation. In simulated groundwater recharge experi-ments, microbial communities became more ef"cient at degradationof pharmaceuticals after several months of exposure, even with lowlevels of biodegradable dissolved OC (Hoppe-Jones et al., 2012). Lossesof caffeine, hormones, and alkylphenols were observed in a septic sys-tem plume on Cape Cod, with estimated transformation rates for caf-feine of 0.07–0.14 d!1 (Swartz et al., 2006). Mass loss of 17#-estradioland branched-chain 4-NP was apparent in a WWTP ef!uent plume onCape Cod, whereas sulfamethoxazole showed only minor mass loss(Barber et al., 2009). Measured mineralization rates in related micro-cosm experiments designed to estimate maximum biodegradation po-tential were 0.011 d!1 for 17#-estradiol and 0.039 d!1 for straight-chain 4-n-NP (Barber et al., 2009). Assuming "rst-order kinetics and agroundwater !ow velocity of 0.42 m d!1 (Barber et al., 2009), thesedegradation rates correspond to N95% removal of 17#-estradiol andN99.9% removal of 4-NP and caffeine during groundwater transportacross 120 m, the minimum protective radius around public wells inMassachusetts with approved yields over 380 m3 d!1.

Sorption to OC in aquifer sediments may retard movement of somehydrophobic OWCs, reduce dissolved concentrations, and enhancebiodegradation. Barber et al. (1988) observed that partitioning of non-polar organic compounds into the solid phase could be predicted bylog Kow and %OC. Hormones (log Kow mostly N3) and alkylphenols(log Kow of N4 for NP, OP, NP1EO and NP2EO) are more hydrophobic,and therefore more likely to partition into the solid phase, than mostof the pharmaceuticals and personal care products we detected (logKowmostly b3). Two relatively hydrophobicmusk fragrances, galaxolide(log Kow 5.9) and tonalide (log Kow 5.7), were not detected in this studyabove the MRL of 10 ng/L; a study of U.S. source waters detected thesetwo compounds more frequently in surface waters than in groundwater(Focazio et al., 2008). Based on typical values in the Cape Cod aquifer forgrain density ($ = 2.6 g/cm3), OC content in b125 !m sediments(fOC = 0.001), fraction b125 !m sediments (f = 0.05) and porosity(% = 0.3) (Barber et al., 1988), we estimated retardation factors (Rf)above 2 (i.e., groundwater velocity is at least twice contaminant veloci-ty) for OWCswith log Kow values above 4.2. Nevertheless, some relative-ly hydrophobic OWCs were found in this study, including PFOA (log Kow

4.81) and gem"brozil (log Kow 4.77). Their persistencemay be related toionization state, since both PFOA (maximum pKa 3.8) and gem"brozil(maximum pKa 4.42) are expected to be primarily present as anions inCape Cod groundwater (pH 5–7; Barber et al., 1988) and ionized speciestend to have lower log Kow values (US EPA, 2000). While retardationmay enhance degradation of biologically labile compounds, chemicalsthat do not readily undergo biodegradation may still persist in ground-water, even when substantial retardation is expected.

Overall, our results suggest that regulations requiring buffer areasaround public supply wells and use of septic systems with soil absorp-tion systems have the potential to prevent hormones, alkylphenols, fra-grances, and some other classes of relatively hydrophobic and readily-degradable OWCs from reaching public wells at levels detectable inthis study.

3.4. Surrogates of OWC presence

The expense of OWC analyses often precludes routine monitoring bypublic water suppliers, especially those serving small communities. Iden-tifying inexpensively-measured surrogates of OWC presence would help

389L.A. Schaider et al. / Science of the Total Environment 468–469 (2014) 384–393

water suppliers prioritize wells for OWC sampling and source water pro-tection.We evaluated correlations between predictors of wastewater im-pact ([NO3

!], [B], well depth, and two metrics of residential andcommercial land use) and OWC presence in public wells, aswell as corre-lations among these surrogates.

3.4.1. Correlations among surrogatesStrong correlations were found among [NO3

!], [B], and land use.Concentrations of NO3

! and B were strongly correlated (Spearman cor-relation coef"cient $ = 0.80; p b 0.001), suggesting a common source.Domestic wastewater from septic systems is the major source of NO3

!

to Cape Cod groundwater (Cole et al., 2006), although fertilizers asso-ciated with landscaping and agriculture may also be sources. Boronis commonly used as a marker of wastewater (Schreiber and Mitch,2006). [NO3

!] was also signi"cantly correlated with %DEVZOC ($ =0.54; p b 0.05) and %DEV500 m ($ = 0.65; p b 0.01); [B] was also corre-lated with %DEV500 m ($ = 0.50, p b 0.05), while not signi"cantlycorrelated with %DEVZOC ($ = 0.33, p = 0.16). Using %RES instead of%DEV yielded similar $ values with [NO3

!] and slightly lower $ valueswith [B]. Both [NO3

!] and [B] were more strongly correlated with%DEV500 m than with %DEVZOC, re!ecting the relative importance ofland use sources in closest proximity to the wells.

3.4.2. Correlations between surrogates and OWCsWe used two aggregate measures of the presence of OWCs:

"[pharma] and the number of OWCs detected (ndetects). "[Pharma]provides a measure of impact speci"cally from wastewater, since non-wastewater sources of pharmaceuticals are not expected on Cape Cod,while ndetects may include OWCs from other sources.

Both ndetects and "[pharma] increased with higher levels of waste-water impact and development (Fig. 3, Table S3). For instance, average"[pharma]was over 100 times higher inwells with [B] N 10 !g/L, indic-ative of wastewater impact, compared to wells with"10 !g/L B. [NO3

!],

[B], and %DEV500 m were all strongly correlated with "[pharma] andndetects. "[Pharma] was most strongly correlated with [NO3

!] andndetects was most strongly correlated with [B]. As with NO3

! and B,"[pharma] and ndetects were both more strongly correlated with%DEV500 m than with %DEVZOC. It is not surprising that "[pharma] andndetects weremost strongly correlatedwith chemicalwastewater indica-tors (NO3

!, B) since %DEV does not re!ect the relative proximity be-tween sources and wells, nor the temporal variability in loading,which may be especially pronounced in this region where the popula-tion more than doubles in the summer.

Well depth was negatively, although not signi"cantly, correlatedwith measures of OWC presence. The strongest correlations wereobserved between well depth and "[pharma] ($ = !0.33) and withndetects ($ = !0.26). The relatively narrow range of well depths(12–39 m) may have limited our ability to "nd a signi"cant relation-ship. Deeperwells pullwaterwith longer!owpaths, allowing for greaterchemical retardation and degradation. Well depth was negatively corre-lated with ndetects in a study of 47 wells (depths 8–223 m; Barnes et al.,2008) and negatively associated with ammonia concentrations in astudy of 26 shallow wells impacted by septic systems (depths 5–30 m;Verstraeten et al., 2005).

3.5. Implications

Our results provide new insight into the transport of OWCs fromseptic systems into groundwater and ultimately into public drinkingwater wells. Overall strengths of our study include the fact that we test-ed for a wide of range of OWCs across a region where groundwater isprimarily impacted by septic systems. Analyzing multiple surrogatesof wastewater impact allowed us to evaluate the ability of each to pre-dict the presence of OWCs. Exploring many chemicals with a range ofsources and characteristics (biodegradability, hydrophobicity) providesinsight into key processes controlling fate and transport.

Fig. 3. Sumof detected pharmaceutical concentrations ("[pharma]) and number of OWCs detected (ndetects) as functions of nitrate, boron, and %DEV500 m. Each graph shows the Spearmancorrelation coef"cient ($) and corresponding p value. %DEV500 m is the sum of unsewered residential and commercial development within a 500-m radius zone around each well.

390 L.A. Schaider et al. / Science of the Total Environment 468–469 (2014) 384–393

Additional sampling of the Cape Cod aquifer would provide greaterinsight into drivers of spatial and temporal variability. Our results,based on one-time sampling, do not reveal seasonal or interannualtrends driven by variations in the number of residents and biogeochem-ical conditions. Repeated sampling would provide amore representativeassessment of drinking water quality and more integrated measure ofexposure for Cape Cod residents over time. While the presence or ab-sence of speci"c OWCs provides some insight into the dominant factorscontrolling transport, this study was not designed to distinguish amongmultiple mechanisms controlling OWC fate and transport. Additionalsampling and groundwater modeling that incorporates heterogeneityin the composition of aquifer sediments and groundwater velocities, aswell as chemical properties of individual OWCs,would allowbetter char-acterization of OWC transport and prediction of other OWCs that mayalso be present.

[NO3!] and [B] were correlated with the presence of OWCs in the

Cape Cod aquifer and may be useful OWC surrogates in other regionswhere sand and gravel aquifers are impacted by domestic wastewater.However, results cannot be generalized to areas where contributionsfrom natural and non-residential anthropogenic sources of B and NO3

!

approach or exceed contributions from residential sources. In some re-gions, [B] in groundwater is elevated due to saltwater intrusion, geolog-ical sources, ormetal-working operations (Waggott, 1969; Barrett et al.,1999). Background [NO3

!] can vary regionally and non-residential an-thropogenic sources include fertilizers and N-rich wastes from feedlotoperations. Furthermore, NO3

! may display non-conservative behaviordue to denitri"cation and other biogeochemical transformations, espe-cially in groundwater systems with higher levels of OC. Stable isotopesof N and B have been used to distinguish multiple pollution sources(Vengosh et al., 1994), but isotopic analyses are less frequently con-ducted by commercial laboratories and data interpretation requirescharacterization of end member isotopic composition. Other chemicalsthat have been suggested as wastewater indicators in groundwater in-clude individual OWCs such as arti"cial sweeteners (Buerge et al.,2009), although these are not routinely analyzed by commercial labora-tories. Many surveys of OWCs in the environment do not report infor-mation about inorganic wastewater markers or land use patterns.Including such ancillary data would help evaluate the usefulness ofthese surrogates more broadly.

Several aspects of our results raise human health concerns. First,concentrations of per!uorinated chemicals and some pharmaceuticalsin this study approached published health-based guidelines. Concentra-tions of PFOA (22 ng/L) and PFOS (110 ng/L) in one distribution systemsample were within a factor of two of the lowest drinkingwater adviso-ry level for these compounds (Table 1; Post et al., 2009; US EPA, 2009b).Furthermore, a recent epidemiological study suggested that currentdrinking water limits for PFOS and PFOA are not suf"ciently protectivefor immunotoxicity endpoints in children (Grandjean and Budtz-Jørgensen, 2013). In addition, our highest phenytoin concentration(66 ng/L) was only 30 times lower than the health-based drinkingwater equivalent level developed by Bruce et al. (2010).

We were not able to evaluate potential health implications for theother OWCs detected in this study because for many OWCs, health-based guidelines are not available at all or are inadequate because of alack of toxicity information (Stephenson, 2009) and limited toxicitytesting requirements. In addition, older studies that are available forsome chemicals, such as OPFRs, did not investigate effects during sensi-tive periods of development (Dishaw et al., 2011). Furthermore, whilethis study included a diverse list of nearly 100 OWCs, there are about80,000 chemicals currently in use, suggesting that other OWCs, as wellas their metabolites, were also present in our samples.

Interpretation of low concentrations of OWCs in drinking water hasbeen controversial. Some risk assessments have suggested that few orno health risks are associated with commonly-reported drinking waterexposures from pharmaceuticals, since such exposures are generally farbelow therapeutic levels or levels where adverse health effects have

been reported in animal or human studies (Bruce et al., 2010; WHO,2011). Similarly, for chemicals present in consumer products, exposuresassociated directly with product use or other exposure pathways (e.g.,food consumption) are expected to bemuchhigher than via consumptionof drinking water, except in cases of highly contaminated drinking water(Egeghy and Lorber, 2011; Lorber, 2008; Trudel et al., 2008; Vestergrenand Cousins, 2009). However, this interpretation does not address ourlimited understanding of potential effects from low-dose exposures or in-teractions among multiple chemicals.

Relatively high doses of pharmaceuticals are given to individualswith expectation of a signi"cant health bene"t, but safety evaluationis not conducted for the purpose of evaluating health risks of wide-spread population exposure to low doses. Some published approachesto setting health-based limits for pharmaceuticals divide the minimumtherapeutic dose by a standard safety factor (NRMMC, 2008; WHO,2011), but pharmaceuticals often have target and non-target effectswell below the therapeutic dose and sensitivity can vary widelyamong individuals, as in the case of antibiotic allergies (Bruce et al.,2010). For example, a recent study showed that acetaminophen inhibitstestosterone production at concentrations approximately 100 timeslower than the therapeutic plasma concentration (Kristensen et al.,2011). Hormones in particular can be active over a very wide range ofconcentrations, so dividing a therapeutic dose by 1000 or even 10,000may still result in a biologically active dose, and effects of EDCs can bemore apparent at lower doses than higher doses (Vandenberg et al.,2012).

While some guidelines for pharmaceuticals are based only on thera-peutic dose, other guidelines have been developed based on results oftoxicity studies (e.g., Bruce et al., 2010). However, few of these studiesare available and their usefulness may be limited by endpoints consid-ered, since assessment for drugs may not include toxicity data or rigor-ous assessment of developmental toxicity, neuro- or immunotoxicity,endocrine toxicity, and carcinogenicity (ICH, 2013). Environmental riskassessments of pharmaceuticals often focus on the most frequently-detected chemicals in environmental waters; however, a prioritizationmethod based on number of prescriptions, toxicity information, metab-olism information, and predicted WWTP removal showed that some ofthe pharmaceuticals with the greatest potential human health riskhave not been studied in the environment (Dong et al., 2013). Trimeth-oprim and atenolol, whichwere both detected in our study, were amongthe 20 (of the 200 most frequently prescribed) pharmaceuticals thatreceived the highest priority scores. Risks from mixtures of pharma-ceuticals also need to be addressed. For example, the common antibioticsulfamethoxazole inhibits metabolism of the commonly-detecteddrug phenytoin (US FDA, 2008); these drugs commonly co-occur inwastewater-impacted drinking water, so the presence of sulfamethoxa-zole could increase the effects of phenytoin.

The presence of antibiotics in groundwater also raises concerns aboutpotential effects on microbial communities, including the developmentof antibiotic resistance. Shifts inmicrobial community structure and bio-geochemical transformations of nitrogen have been observed followingexposure to sulfamethoxazole, with the lowest concentration tested,5 nM(1266 ng/L), resulting in a 47%decrease in nitrate reduction poten-tial (Underwood et al., 2011). Microbial communities exposed to 240–520 !g/L sulfamethoxazole showed changes in composition and sulfa-methoxazole sensitivity, especially in the absence of prior exposure(Haack et al., 2012). While these effects were observed at much higherconcentrations than observed in publicwells on Cape Cod, these "ndingsdemonstrate the potential for sulfamethoxazole and other antibiotics en-tering sand and gravel aquifers to affect in situ microbial communities,especially in close proximity to ef!uent discharges.

4. Conclusions

This study found organicwastewater compounds, including pharma-ceuticals, per!uorosurfactants, and organophosphate !ame retardants,

391L.A. Schaider et al. / Science of the Total Environment 468–469 (2014) 384–393

in public drinking water wells in a sand and gravel sole source aquiferwhere septic systems are prevalent. Maximum concentrations oftwo pharmaceuticals matched or exceeded maximum concentrationsfound in other U.S. drinking water sources. The presence of OWCs indrinking water raises human health concerns, but a full evaluation ofpotential risks is limited by a lack of health-based guidelines and toxic-ity assessments. While many OWCs were not present at detectablelevels in these public wells, other OWCs persisted through onsite andcentralized wastewater treatment and during subsurface transport.Concentrations of nitrate and boron and extent of unsewered develop-mentmay be used to identifywellsmost likely to be impacted byOWCs.Our results demonstrate the vulnerability of drinking water supplies insand and gravel aquifers where groundwater discharges of wastewaterare prevalent. Future studies are needed to identify themajor sources ofsome OWCs, such as per!uorosurfactants, into domestic wastewaterand to determine primary fate and transport processes in impactedaquifers.

Nutrients are a major cause of impairment in surface waters acrossthe U.S. In watersheds where a substantial portion of nutrient pollutioncomes from domestic wastewater, loading of pharmaceuticals, hor-mones, and other OWCs is also expected to occur. Management effortsaimed at reducing nutrient loading can alter the extent and locationsof OWC loading into surfacewaters and groundwater.While groundwa-ter is often considered to be better protected frompollution than surfacewater, public and private wells may still be vulnerable. Even deep wellsare not entirely protected from pollution; pathogens leaching fromleaking sewers were recently detected in wells up to 300 m deep(Bradbury et al., 2013). While most OWCs are not currently regulatedin drinking water, integrated wastewater planning should anticipatethe impacts of wastewater on drinking water supplies.

Acknowledgments

This project was funded by the Massachusetts Environmental Trustand the U.S. Centers for Disease Control and Prevention (Grant number1H75EH000732-01). We thank the participating public water supplydistricts for their cooperation and logistical support; Yongtao Li, JessieVarab, Nathan Trowbridge and Daniel Klaybor at Underwriters Labora-tories; Teresa Rawsthorne and Cynthia Tomey at AXYS Analytical;Laura Perovich, Farley Lewis and Ali Criscitello for assistance withsample collection; and Damon Guterman atMassachusetts Departmentof Environmental Protection for nitrate, pumping rate, and well depthdata.

Appendix A. Supplementary data

Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.scitotenv.2013.08.067.

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