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1 잠재적 POPs 로서의과불소화화합물의환경내분포및거동 : 물성, 환경내농도수준, 상분배및장거리이동을중심으로 김승규 J. ENVIRON. TOXIOL. Vol. 23, No. 3, 143~164 (2008) ( 주 ) 네오엔비즈환경안전연구소 Environmental Distribution and Fate of Perfluorinated ompounds (PFs) as Emerging POPs: Physico-hemical Properties, Emission, ontamination Level, Inter-phase Distribution and Long-Range Transport Seung-Kyu Kim Institute of Environmental Protection and Safety, NeoEnBiz o. ABSTRAT oncern about perfluorinated compounds (PFs) is growing nationally as well as globally. PFs could be considered emerging POPs due to their environmentally persistent, bioaccumulative, and potentially harmful properties. Moreover, perfluoroalkylates (PFAs) such as PFOS and PFOA are reported to experience long-range transport (LRT) to the Arctic in spite of their low volatility and strong solubility. The possible pathways contributing to LRT have been proposed but are still in debate in combination with unclear source definition and uncertain physico-chemical properties. The environmental fate of PFs is more complicated because of the presence of precursors that are degraded to PFAs and are extremely different from their daughters, PFAs, in physico-chemical properties. To what extent and through what pathways are human and wildlife exposed is determined by the environmental fate and distribution of PFs. To define uncertainties in fate and distribution thus is critical to prevent erroneous policy and/or determination related with exposure and risk reduction. This article aimed to review controversy and/or uncertain issues for the environmental fate and distribution of PFs and to prospect research topics necessary to dissolve uncertainties. Key words : PFs, precursor, environmental fate, long-range transport, emission 서 론 To whom correspondence should be addressed. Tel: , Fax: skkim89@gmail.com PFOA (perfluorooctanoic acid) 나 PFOS (perfluorooctane sulfonate) 와같은과불소화화합물 (perand poly-fluorinated compounds: PFs) 에대한국내외적관심이꾸준히증가하고있다 (OED, 2006; 환경부, 2006). 이들물질은 PBs, Dioxins/Furans, 유기염소계농약등과같은기존의염소화혹은브롬화된지속성유기오염물질 (persistent organic pol- 143

2 144 J. ENVIRON. TOXIOL. Vol. 23, No. 3 lutants: POPs) 들이보여주는것과유사한 PBT (persistent, bioaccumulative, toxic) 특성을갖는것으로알려져있다. 예컨대, PFOA/PFOS 는발암성이나발달독성 (Upham et al., 1998; Biegel et al., 2001; Lau et al., 2004) 을가지며거의모든환경매체에서그리고오염원이없는극지방을포함한원거리지역에서까지다양하게검출되고 (Giesy and Kannan, 2001; Yamashita et al., 2005; Scott et al., 2006; Smithwick et al., 2006; Janke et al., 2007a; Stock et al., 2007; Young et al., 2007), 혐기및호기조건하에서잘분해되지않으며 (Kissa, 2001), PFOS 및사슬이긴고분자알킬산 (long-chain alkylated acids: long-chain PFAs) 등은수서생태계의먹이사슬에서농축및증폭현상을보이는것 (Martin et al., 2004; Kannan et al., 2005) 으로조사되었다. 또, 기존의 POPs 와는달리 1970 년대이후 2000 년대초반까지환경중농도는지속적인증가경향을보였다 (Holmström et al., 2005; Smithwick et al., 2006; Verreault et al., 2007). PBT 특성및관측된장거리이동가능성 (longrange transport potential: LRTP) 때문에 OED 는 PFAs 을잠재적 POPs 로간주하였다 (OED, 2006) 년에 Electrochemical fluorination (EF) 제조방법을통해 Sulfonyl- 계 PFs 를생산하던세계최대제조업체인 3M 이자발적으로생산을중단하고 Telomer- 계 PFs 를생산하던업체들은관련상품들로부터해당물질을제거하려는협약을 USEPA 와체결하였다 (USEPA, 2005). 이러한배출감소노력의결과에도불구하고, 다양한매체에서여전히광범위하게검출되고있는 PF 의환경내주요이동및노출경로, 유효한배출원, 환경중분포에영향을미치는 PFs 의물리화학적특성등에서의큰불확실성때문에배출감소에따른효과 ( 즉, 환경중농도나노출의감소 ) 가즉각적이고실재적일수있는가에대한이견이존재한다 (Armitage et al., 2006; Butt et al., 2007; Wania et al., 2007; Schenker et al., 2008). 물성 (physico-chemical property), 배출원및배출량 (emission inventory), 환경중이동경로 (pathways) 등에대한불확실성은 PFs 의환경거동과관련하여뜨겁게논쟁중인이슈이기도하다. 몇가지쟁점들을소개하면다음과같다. 첫째, PFs 는물성이전혀다른전구물질 (precursors) 과다양한 경로의분해과정을통해전구물질로부터생성되는 perfluoroakylated compounds (PFAs) 로구성되며, PFAs 는환경중에서 free acid 와음이온형태 ( 예컨대, PFOA 와 PFO - ) 로존재한다 (OED, 2006). 전구물질이나 PFAs 자체의물성에대한신뢰할만한측정자료가거의존재하지않기도하지만 (Arp et al., 2006; EMN, 2006, 2007, 2008), 다양한분해과정과그과정중발생하는중간산물 (intermediates) 에대한정보도제한적으로존재한다. 특히, PFOA 에대해폭넓은산해리상수 (pka) 값으로제안되고있는데해당값들의범위는정반대의상분배 (interphase distribution) 결과를야기해강우에의한대기침적효과 (rain-scavenging effect) 와대기잔류시간 (residence time or life-time) 등에대한해석오차를증가시킬수있다 (Goss et al., 2008; Kim and Kannan, 2008). 둘째, PFAs 는그자체로도생산되며 AFFF (aqueous film forming foam) 과같은소화제액등의주요구성물질로사용되기도하고 Fluoropolymer 등의생산시중합체나중간체로사용되기도한다 (3M, 1999; Prevedouros et al., 2006). 그렇기때문에환경으로의배출은 전구물질형태로의배출및분해 / 생성 이라는간접적배출 (indirect emission) 과생산과정중혹은상품으로부터 PFAs 의직접배출 (direct emission) 로발생한다. 생산및사용정보로부터추정된배출량 (Prevedouros et al., 2006; Armitage et al., 2006) 과측정된환경중농도로부터추정된배출량 (Ellis et al., 2003) 에는 10~ 100 배정도의차이가존재하며 직접배출 과 간접배출 의상대적기여도에대한시각차도뚜렷하다. 셋째, 직접배출과간접배출은각각 PFAs 와전구물질을대변하는데두물질그룹은물성에서뚜렷한차이를보이기때문에그로인한환경거동에대한해석또한크게달라질수밖에없다. 낮은휘발성 (volatility) 과큰수용해도 (water solubility) 를갖는 PFAs 의극지방환경에서의검출을설명하기위해제기된 간접배출 전구물질 대기이동 가설 (Ellis et al., 2003; Stock et al., 2004; Wallington et al., 2006; Young et al., 2007) 과 직접배출 PFAs 해류이동 가설 (Prevedouros et al., 2006; Armitage et al., 2006; Wania et al., 2007; Schenker et al., 2008) 이최근까지가장큰논쟁대상이었다. 최근에 직접배출 PFAs 대기이동 가능성이제기되었다 (Kim and Kannan, 2007; McMurdo et al., 2008).

3 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 145 환경에서의거동은해당지역각각의매체에서의농도분포및수준을결정하여결과적으로해당환경내야생생물및인간의노출경로및노출량을결정한다. 따라서, PFAs 환경거동에서의불확실성의제거는 PFAs 에대한생태계및인간노출의불확실성의제거로직결된다. 본논문은국내외연구결과를종합검토하여 PFAs 의환경거동과관련된쟁점들을구체적으로소개하고불확실성을해소하기위한향후전망을제시하고자한다. 본 론 1. PFs 물질군과물적특성 (physicochemical properties) PFs 는휘발성이강하고용해도가낮은중성화합물 (neutral compounds) 인전구물질들 (precursors) 과반대로휘발성이매우낮고수용해도가큰이 온성 PFAs 로구성된다 (Fig. 1 관련된주요화합물에대한구조식및약어정보는부록에첨부됨 ). PFOA 와그것의전구물질로알려진 8:2-FTOH 를비교해보면두물질그룹의확연히다른물리화학적특성을확인할수있다 : 증기압 (Vapor pressure (Pa); vs. 227) (USEPA, 2002; Lei et al., 2004), 헨리상수 (Log H(Pa.m 3 /mol); 1.02 vs. 4.99) (Arp et al., 2006), 유기탄소 - 물분배계수 (Log K oc (L/Kg); 4.3 vs. 6.14) (Arp et al., 2006), 수용해도 (solubility (g/l); 9.5 vs ) (Liu and Lee, 2005; Prevedouros et al., 2006). 특히, PFAs 는환경중에서 free acid 와음이온형태로모두존재가능하지만환경에서의일반적인산성도 (ph) 범위에서는음이온형태 ( 즉, PFO - ) 가대부분을차지한다. 앞에서제시한헨리상수가 free acid 형태의 PFOA 에대한것임을감안할때, 대기 - 수체간분포에서 PFOA 는 8:2-FTOH 보다수체에잔류할가능성이훨씬더커진다. F F F F F F F O PFOA F F F F F F F F OH F F F F F F F F F 8 : 2-FTOH F F F F F F F F H 2H 2OH PFOS F 3 F 2 F 2 F 2 F 2 F 2 F2 F 2 O S O O Sulfonamides F 3 F 2 F 2 F 2 F 2 F2 F2 F 2 O S O N R Fig. 1. hemical structure of representative PFs (PFOA, PFOS, 8 : 2-FTOH, Sulfonamides). R

4 146 J. ENVIRON. TOXIOL. Vol. 23, No. 3 소수성 (hydrophobic) 과친유성 (lipophilic) 을갖는기존의 POPs 와는소수성과소유성 (lipophobic) 을갖는 PFs 는물, 기름, 먼지등에대한저항성이커서방수 (water-resistant) 및방유 (oil-resistant) 목적의가죽, 카펫, 종이, 피복, polymer 등의표면처리제, 계면활성제, 혹은 AFFF 등소화제액에사용되어왔다 (OED, 2006). 독특한특성때문에물과탄화수소에섞으면두용액으로녹아들지않고제 3 상을형성한다. 이런특성때문에소수성의척도인옥탄올 - 물분배계수 (K ow) 를실측하기힘들다. 소유성때문에 PFs 는친유성을갖는다른기존의 POPs 와달리유기탄소나지방질에축적되기어려운반면, 단백질등에결합하여축적될가능성이큰것으로알려져있다 (Giesy and Kannan, 2002; Jones et al., 2003). 한편, PFAs 의 carboxyl- 기나 PFAS 의 sulfonyl- 기는수소원자를잃고극성을띄게되어물에서음이온상태로쉽게용해된다. PFAs 는기존 POPs 와달리수용해도가큰반면, K ow 나옥탄올 - 대기간분배계수 (K oa) 는상대적으로작아기체상이나고체상보다는수체용존상에더많이잔류할수있다 (Fig. 2). 2. 배출량과배출특이성 알려진 PFs 오염원들과생산량등을고려하여지금까지전지구적으로발생했을 PFAs 의총배출량이각배출원별로추정되었다 (Prevedouros et al., 2006). 이배출량조사 (emission inventory) 의추정된누적배출총량은 3,200~7,300 톤이고주요배출은 Fluoropolymer 제조과정에발생하는것으로조사되었다. 또, 제조나사용중 PFAs 형태로직접배출되는것이총배출의 90% 이상을차지하는반면, 비의도적불순물혹은반응부산물형태나전구물질의분해로부터배출되는간접배출은 10% 미만인것으로추정되었다. 1950~2005 년까지 직접배출 경로를통해배출된 PFOA 의전지구적총누적배출량은 2,700~5,000 톤인것으로추정되었는데이양은 1974~2005 년까지의 PFOA 의대표적전구물질인 FTOHs 의총누적배출량인 1,500 여톤보다 3 배정도많은양이다 (Wania, 2007). 또, 배출량조사로부터 FTOHs 의연간배출량은 1990 년 30 톤 / 년 ~2005 년 200 톤 / 년인것으로추정되었다 (Wania, 2007). 이런배출량조사추정치와달리간접적인 Log Koa (dimensionless) PDDs/DFs PBs PFAs Precursors PAHs OPs PBDEs PFs Log K aw (dimensionless) Log K ow (dimensionless) Log Koa (dimensionless) PDDs/DFs PBs PAHs OPs PBDEs PFs Vapor pressure (Pa) Solubility (mol L -1 ) PDDs/DFs PBs OPs PBDEs PAHs PFs PFAs Precursors PDDs/DFs PBs OPs PBDEs PAHs PFs 8 : 2 FTOH PFOA Fig. 2. Matrix panels of physico-chemical properties for comparison between PFs and existing POPs.

5 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 147 방법으로북미대기중에서실측된 FTOHs 농도범위값을근거로해당농도수준을유지하기위해필요한연간배출량 (100~1,000 톤 / 년 ) 이추정되었는데 (Ellis et al., 2003), 배출량조사추정치보다 10 배정도낮은값이었다. 이들서로다른배출량추정치는이후에검토되는것처럼, PFs 의장거리이동및분포에대한가설제시및환경에서검출되는농도를해석하는데있어서서로다른적용근거가된다. PFs 는주로전기화학적불소화방법 (Electrochemical fluorination, EF) 과불소화합물들의화학적결합을이용하는방법 (Telomrization) 에의해생산되는데각각의생산방법에따른특이성이존재한다 (Table 1). 예컨대, 3M 의 EF 방법에의해생산된 PFs 는홀수개탄소수를갖는화합물 (odd-chain PFs) 과짝수개탄소수를갖는화합물 (even-chain PFs) 모두가존재하며, 선형 (straight- or lineartype) 과가지형 (branched type) 이성체가 7:3 의비율로존재한다. 반면에 Telomerization 방법에의해생산되는 PFs 는선형의, even-chain 화합물만존재한다 (Simons, 1949; Kissa, 2001). 또한, 4~15 개의탄소수 (4~15) 를갖는존재가능한 PFAs 중 8 (PFOA 혹은 PFOS) 이나 9 (PFNA) 가가장많이생산되었고, 직접배출을통해배출된 PFAs 중에서는 odd-chain 이 even-chain 보다더많이 ( 즉, 9 10, 10 11, 12 13) 생산된것으로알려져있다 (Prevedouros et al., 2006). 이런정보에기초해환경시료에서검출되는화합물간의탄소수에따른구성비율혹은이성체간의비율등이오염원을추적하고이동경로를규명하는주요단서로활용되기도한다. 예컨대, 북극지방눈시료에서측정된 1 에가까운 PFDA-PFUnDA 혹은 PFOA-PFNA 사이의평균비율을이용해쌍을이룬두화합물은각각 10 : 2- FTOH 와 8:2-FTOH 라는동일한기원을갖는것으로여겨졌다 (Young et al., 2007). De Silva 와 Mabury 는북극곰의혈액에서관측된 8~11 PFAs 의이성체들중선형이성체가 98% 이상차지하고 even-chain 이 odd-chain 보다많이검출된결과로부터 Telomerization 을통해생산된것을주요오염원으로제기하였다 (De Silva and Mabury, 2004). 반면에, 북극지방생물체에서측정된자료들 (Martin et al., 2004; De Silva and Mabury, 2004) 에서관측 된이웃한 PFA 쌍들중 odd-chain even-chain 인검출농도관계로부터직접배출원의기여도가더클수있음이제기되었다 (Prevedourous et al., 2006). 또, Simcik 과 Dorweiler 는도시지역에서배경지역으로갈수록호숫물에서의 PFHpA-PFOA 비율이증가하는경향으로부터 오염원영향지역 과 대기침적의영향을배타적으로받는지역 을구분하는척도로제시하였다 (Simcik and Dorweiler, 2005). 대기중수산기 (OH - ) 와의산화반응을통해 8:2-FTOH 로부터비슷한양의 PFOA 와 PFNA 가생성되는것으로알려져있다 (Ellis et al., 2004). 록키산맥정상부근의호숫물에서비슷한농도수준으로검출된 PFOA-PFNA 로부터해당지역은 FTOH 의대기산화와침적이라는배타적이동경로에의해영향받음이조사되었다 (Loewen et al., 2008). 또, 폐수종말처리장, 강, 호수등에서측정된 PFOS- PFOA 의비율을이용해조사대상호수로의폐수유입유무가평가되기도하였다 (Kim and Kannan, 2007). 그러나, 환경매체에서의구성비및이성체비율은상간분배 (phase-partitioning or distribution) 나생물체로의섭식 (uptake) 혹은제거 (clearance) 과정등복잡한경로를통해변화된다. Kim 과 Kannan 은한유역계내의다양한환경매체에서 PFAs 각화합물간의구성비가매체간에그리고시공간적으로바뀔수있고그것은물리화학적특성 ( 특히 K ow) 에의해좌우될수있음을제시하였다 (Kim and Kannan, 2008). 또, 극지방에서선형이성체가높은비율로검출되는것은표면활성도 (surface activity), 헨리상수, pka 등과같은선형과가지형이성체사이의물성차이로인해발생할수도있음이제기되었다. 즉, 대기 - 수체간미세층 (micro-layer) 에어로졸 기체상으로의재분배 등의과정을거치며선형이성체의비율이증폭되고결과적으로배경지역으로갈수록선형이성체의비율이증가한다는것이다 (McMurdo et al., 2008). 또생물체내로부터 PFOA 의상대적으로빠른제거율 (clearance) 을고려했을때, 이웃한 even-chain/odd-chain 화합물간의비율 ( 예컨대, PFNA PFOA) 이항상간접배출의근거 (Martin et al., 2004) 가될수는없다. 따라서, 배출원에서갖는여러구성비에대한정보가 PFs 의환경거동과분포를설명하기위해획일적으로적용될수없고주의가필요하다.

6 148 J. ENVIRON. TOXIOL. Vol. 23, No 환경중농도수준 대기에서관측된 PFAs ( 특히 PFOA) 농도는해양대기에서 0.3~1.5 pg/m 3 (Jahnke et al., 2007b), 대도시대기에서 수 ~ 수백 pg/m 3 (Barber et al., 2007) 등이검출되었는데, 특히교통량이많은도로변대기 (72~919 pg/m 3 ) 가중소도시일반대기 (1.6~2.6 pg/m 3 ) 보다수백배까지높을수있음이보고되었다 (Harada et al., 2005a). 또, PFs 제조시설인근대기에서는 120~900 pg/m 3 의농도가관측되었다 (Barton et al., 2006). 대기중전구물질 (FTOHs) 의농도는인구밀도와밀접한상관성을갖는데, 비도심지역 (rural area) 에서는 ~30 pg/m 3 이그리고대 도시지역에서는 100~200 pg/m 3 이일반적수준으로고려된다 (Stock et al., 2004; Barber et al., 2007; Jahnke et al., 2007b). 특히, 실내공기는실외대기보다수십 ~ 수백배높은농도값 (Soeib et al., 2005; Barber et al., 2007) 을보인반면, 극지방대기나해양대기는수 ~ 수십 pg/m 3 (Shoeib et al., 2006; Jahnke et al., 2007a) 의농도범위를보인다. 수체에서의 PFOA 는 PFs 제조시설인근 (Hansen et al., 2002) 이나하 / 폐수처리수 (Sinclair and Kannan, 2006) 혹은폐수유입하천수 (Saito et al., 2003) 에서평균적으로수백 ng/l 가검출되고, 일반하천수에서는수십 ng/l 그리고대양수 (ocean water) 에서는 1 ng/l 가검출된다 (Fig. 3). PFOS 도유사한 PFOA in water (ng/l) PFOS in water (ng/l) 1.0E E E E E E E E E E E E E E E E E E E E-03 Source area Wasterwater Wastewater disposal site PF manufacturing sites Stream (Shihwa-Banwol) Lake Shihwa Gyeonggi Bay South coast West coast Source area Korea Korea Ai River Tokyo Bay Offshore HongKong coast hina coast NYS ambient water Sulu Sea South hina Sea Western Pacific Ocean entral-eastern Pacific Ocean North Atlantic Ocean Mid Atlantic Ocean AFFF spill site USA superfund site PF manufacturing sites Wastewater Stream (Shihwa-Banwol) Lake Shihwa Gyeonggi Bay South coast West coast National wide Ai River Tokyo Bay Offshore NYS ambient water HongKong coast hina coast Sulu Sea South hina Sea Western Pacific Ocean entral-eastern Pacific Ocean Noth Atlantic Ocean Mid Atlantic Ocean Fig. 3. oncentration ranges of PFOA and PFOS in worldwide waters (See the references in text and Kim et al., 2007). Japan Japan hina hina Ocean Ocean

7 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 149 Table 1. Differences in manufacture of PFs (modified from Simcik, 2005) Manufacture process Electrochemical fluorination (EF) Telomerization Major products Sulfonamides, PFOS, PFOA FTOHs Primary manufacturer 3M DuPont hain length Even and Odd Even only hain conformity Linear (straight) and branched chain (70~85% versus 15~30%) Linear (straight) chain only Uses AFFF(for PFOS), stain protectant, surfactants, polymers Surfactants, polymers Emission status Production ban since 2002 On-going production 분포및농도값을보이는데, AFFF 누출사고가발생한지역 (Moody et al., 2002) 에서는수천 ng/l 가검출되기도하였다 (Fig. 3). 우리나라의일부공장지대근처하천수에서 수백 ng/l 과광양만의일부하천에서평균적으로 99 ng/l ( 최대 1,412 ng/l) 등의비교적높은 PFOS 가검출되었으나일반하천이나연안해수에서는평균적으로수십 pg/l 수준인것으로알려졌다 ( 환경부, 2006). 그러나, 저개발국가와선진국의중간정도의오염도를보이는기존 POPs 와달리 PFOA 나 PFOS 의전체적인국내검출농도의범위는타선진국들에서측정된값들보다낮다고할수없다 (Kim et al., 2007). 사람혈중 PFOA, PFOS 농도는 수 ~ 수십 ng/ml 인것으로알려졌는데 (Kannan et al., 2004), PFOS 와 PFOA 가대표적으로높게검출되며대체적으로 PFOS 가 PFOA 보다높다. 한국인의혈중농도는 PFOA 가수백 ng/ml ( 평균 88) 이검출 (Kannan et al., 2004) 되기도하였으나최근의조사자료들은두화합물모두 10 ng/ml 을보이고있다 ( 미발표자료 ; 환경부, 2006). 4. 분포와거동에영향을주는인자들 1) 유기탄소 - 물 (K oc), 옥탄올 - 물 (K ow) 분배계수기존의 POPs 와다른, PFs 가갖는소수성과소유성이라는특성때문에 PFs 는생물체의지방질이나토양, 퇴적물, 대기입자등의유기탄소가주된축적대상이아닌것으로여겨져왔다 (Giesy and Kannan, 2002; Prevedouros et al., 2006). 따라서, PFAs 는유의할만한수준으로토양입자에잔류하지못하고토양표층으로부터지하수층을거쳐최종적으로수체로유입되어 (Davis et al., 2007), 결과적으로육상에배출된 PFAs 는표층수나지하수 로빠르게이동할수있다 (Skutlarek et al., 2006). 이런거동특성에근거하여 McLachlan 등은한유역계에서배출된 PFs 의총배출량은해당유역계의강을통해해양으로배출된누적배출량 (riverine discharge) 과유사할것이라가정하고, 유럽주요강하구에서측정된 PFs 농도로부터추정된배출량을배출량조사자료로부터추정된유럽의총배출량과비교하였다 (McLachlan et al., 2007). 그러나한편으로다매체거동모형의민감도분석결과에따르면, 제한적이긴하지만 10 배 K oc 의증가는북극에도달되는 PFOA 의 15% 감소를유발할수있음이보고되었다 (Wania, 2007). 또다른연구들은퇴적물이나슬러지에서 PFOS 의강한흡착을보고하거나 (3M, 2000) PFs 농도수준이나 PF 구성비등에서저서생물들과유영생물들간의확연한차이가보고되고퇴적물기원오염의중요도가토의되기도하였다 (de Vijver et al., 2003a, b). 고체상매체 ( 즉, geosolids) 에대한흡착용량 (Sorption capacity) 은매체별잔류정도와잔류시간을결정하기때문에있다면그것에대한척도에대한정보는매우중요하다. 그럼에도불구하고토양이나퇴적물등에서의연구는상대적으로매우미미하다. 최근에측정된고체상 - 용존상분배계수 (K d) 는매체내뿐만아니라매체간에도큰변이가존재한다 (Table 2). PFs 흡착현상에서유기탄소의중요성을언급한것은비교적으로최근이다. 유기탄소함량은흡착과정에영향을주는가장중요한인자이며토양 - 물 ( 혹은퇴적물 - 물 ) 사이의분배계수 (K d) 와선형상관관계를갖는것으로조사되었다 (Liu and Lee, 2005; Higgins and Luthy, 2006; Johnson et al., 2007). 큰변이값의분배계수 (K d) 에도불구하고, 비교적좁은범위의 1.90~2.17 와 2.4~3.1 값이각각 PFOA 와 PFOS 의 Log K oc 값으로보고되었

8 150 J. ENVIRON. TOXIOL. Vol. 23, No. 3 Table 2. Reported solid-water distribution coefficient (K d) of PFOS and PFOA Media Kd (L/Kg) PFOS PFOA References lay Footitt et al., 2004 Soil lay loam Footitt et al., 2004 Sandy loam Footitt et al., 2004 Average Footitt et al., Footitt et al., , Johnson et al., 2007 Sediment Nakata et al., Nakata et al., ~1979 (597) 4.5~25 (16) Kim and Kannan (2008) SS - 353, 444 Schultz et al., (1028) - Footitt et al., , , 609 Schultz et al., , , 4167 Sinclair et al., 2006 Sludge Log K oc (L/Kg) 2.4~3.1 - Johnson et al., ~3.1 3M, ~2.17 DuPont, ± Higgins and Luthy, 2006 다 (Table 2). Log K oc 값은분자량이증가할수록커져, F 2 - 사슬이한개증가할때마다 PFAs 계열은 0.50~0.60, PFAS 계열은 0.23 씩의증가가보고되었다 (Higgins and Luthy, 2006). 흡착분배계수는 [a 2 + ] 농도가증가할수록그리고 ph 가감소할수록증가하여유기탄소이외에도정전기적인력 (electrostatic attraction) 이또다른변수로작용할수있다 (Higgins and Luthy, 2006, 2007). 또, 유기탄소함량과관련하여비가역적흡착 (irreversible sorption) 도관측되었다 (Liu and Lee, 2007). Log K ow 값이 5 이상인화합물들이스톡홀름협약 POPs 기준에포함되는데, 최근추정된 K ow (Arp et al., 2006) 에따르면이 POPs 기준을만족하는 PFs 는 8:2- FTOH, 10:2-FTOH, NEtFOSE, NMeFOSEA, NEtFOSA 등의전구물질과 PFDA 이상의고분자 PFAs, PFOS 이상의고분자 PFAS 등이다. PFOS 는 PFOA 보다 10 배정도큰 K ow 값이추정되었다. Kim 과 Kannan 은한유역계내다매체연구결과로부터 대기, 수체 에서와정반대의 PFOA-PFOS 상대점유율이 토양과퇴적물 에서관측됨을보고하고해당점유율의매체간변화는 PFOA, PFOS 간의 K ow 차이에의해설명될수있음을보였다 (Kim and Kannan, 2008). 유입하수에서 PFOA 농도가상대적으로높았음에도불구하고슬러지에서는오히려그반대로 PFOS, long chain-pfda, PFUn- DA 의농도가 PFOA 보다높아지는경향이관측되었다 (Schultz et al., 2006; Sinclair and Kannan, 2006). 2) pka 와 ph PFAs 는약산으로써 free acid 형태 ( 예컨대, PFOA) 와해리된음이온형태 ( 예컨대, PFO - ) 로존재한다. 각형태별존재양은해당화합물의해리도 (pka) 와해당환경의 ph 에따라결정된다. 예컨대 (Eq. 1) 에따라 3.43 의 pka 값을갖는 PFOA 는 ph 가 5 인빗물에서는 2.6% ( 즉, 1,000 개 molecules 중 26 개 ) 만이 free acid 형태로존재하고나머지 97.4% 는음이온형태로존재한다 (Fig. 4). 1 Fraction of [PFOA]= mmmmmmmmmmmmm 1+10 (ph-pka) (Eq.1) 해리되어존재하는 PFO - 는극단적으로낮은헨리상수값 (Log K aw -6.5) 을갖는반면, PFOA 는수체에서대기로의분배가활발히발생할정도로높은값 (Log K aw =-2.37~-2.9) 을갖는다. 따라서, 수체내존재하는두형태의상대적존재량은곧

9 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 151 매체 ( 예컨대, 대기 - 수체 ) 간분배에도결정적인영향을준다. 비교적넓은 pka 값 (-0.5~4) 들이 PFOA 에대하여보고되었다 (Brace, 1962; Kissa, 2001; EMN, 2007, 2008; Goss, 2008). 넓은 pka 값의존재는선택에따라대기중의기체상과용존상 ( 빗물 ) 에존재하는 PFO(A) 의상대적인양에대하여정반대의결과값이도출될수있음을의미한다. 예컨대, -0.5 의 pka 값은 ph=5 의빗물속 free acid 형태의존재비율을 % 로감소시킨다 (ph= 3.43 일때는 2.6%). 따라서, 빗물속에존재하는 PFO(A) 의대부분은빗물속에해리되어존재하고대기기체상으로분배가거의이루어지지않는다. 존재가능한두형태를모두고려한 PFO (A) 의 대기 - 물간의분배계수 (D aw) (Eq. 2), 대기중수증기의상대부피 (volume fraction, 10-6 ) (Seinfeld, 1996), 강우중의 ph (=5), 대기입자농도 (TSP=50 μg/m 3 ) 를이용하여대기중 가스 - 입자 - 수증기 사이에존재하는 PFO(A) 의상대적양을계산할수있다 (Fig. 4). K AW D AW =mmmmmmmmmmmmmm (Eq. 2) 1+10 (ph-pka) 작은 pka ( 에컨대, -0.5) 을적용하면대기로의휘발이거의발생하지않고대부분 (99.6%) 의 PFO (A) 가빗물에존재하는반면, 큰 pka ( 예컨대, 3.43) 를적용하면대부분 (96.9%) 이기체상으로존재하게된다. 결과적으로어떤 pka 값을선택하느냐에따라대기로부터강우에의한세정효율 (rain-scavenging efficiency) 에대해상반된결론을내릴수있다 (Goss, 2008; McMurdo et al., 2008). 대기중잔류시간 (atmospheric life-time), 그리고그것과연관된장거리이동성 (long-range transport potential, LRTP) 은강우에의한세정효율과직결되기때문에불확실한 pka 값은환경거동및분포에대한해석불확실성을증가시킨다. 최근에 Kim 과 Kannan 은 대기기체상, 빗물, 수체 에서측정된농도로부터 PFOA 의 pka 을 2~4 로추정하였다 (Kim and Kannan, 2008). 이값은기존에보고된 2~3 의값 Fraction of free acid (PFOA) pka= Fraction of free acid (PFOA) pka= ph ph % fraction pka=-0.5 ph in rain-droplet %PFOA_gas %PFOA_ap %PFOA+PFO - 1_rain %PFOA_rain %PFO - _rain pka= % fraction ph in rain-droplet %PFOA_gas %PFOA_ap %PFOA+PFO - 1_rain %PFOA_rain %PFO - _rain Fig. 4. Fraction of free acid form (PFOA) in rain-droplet (upper panels) and fractions of PFOA and/or PFO - distributed among atmospheric phases (downward panels). ph=5 was assigned for rain-droplet: The graphs were made using equations shown in Schwarzenbach et al., 2002 and Goss 2008.

10 152 J. ENVIRON. TOXIOL. Vol. 23, No. 3 과유사하다 (Kissa, 2001; USEPA, 2005). 3) 전구물질의분해 (Degradation from precursors) 대기에서의광분해및산화반응 (Ellis et al., 2003; Hurley et al., 2004; Ellis et al., 2004; D Won et al., 2006; Martin et al., 2006), 수체에서의광분해및가수분해 (Hori et al., 2004; Gauthier et al., 2005), 토양, 슬러지등에서의미생물분해 (Dinglasan et al., 2004; Wang et al., 2005a, b; Russell et al., 2008) 를통해 PFs 전구물질 (FTOHs, sulfonamides) 은다양한중간산물 ( 예컨대, FTA, FTUA, FOSA, FOS- AA) 들과최종적으로더이상분해되지않는안정적인 PFAs 을생성함이밝혀졌다. 전구물질 (FTOH 혹은 sulfonamide) 은 NO x 의부재속에서대기중산화반응을통해약 1~10% 의 PFAs 를생성하며인접한탄소사슬을갖는두화합물 ( 예컨대, PFOA 와 PFNA) 은비슷한양으로생성되는것으로알려졌다 (Ellis et al., 2004; D Eon et al., 2006; Martin et al., 2006). 반면에대기 nf 2n+1 (O)O 2 라디칼과 NO x 의반응은 unzipping cycle 을통해 OF 2 를생성하므로대기중 NO x 의존재는 PFAs 의생성을감소시킨다 (Sulbaek-Andersen et al., 2003). 예를들면, Wallington et al. 은 10 ppt 의 NO x 농도를갖는대기에서는약 30% 의 PFOA 생성량이 100 ppt 의농도에서는 2% 로감소할것이라고추정했다 (Wallington et al., 2006). 따라서, 대기에서 PFAs 의생성량은도심에서비도심으로갈수록증가할것으로기대된다. 한편, 슬러지노출실험결과 8:2-FTOH 의생분해로부터 20~80 일간노출후약 2~3% 의 PFOA 가생성되는것으로조사되었다 (Dinglasan et al., 2004; Wang et al., 2005b). 따라서, 생분해에의한 PFOA 생성률은약 day -1 로추정된다. 대기 (Barber et al., 2007; Jahnke et al., 2007a, b; Stock et al., 2007), 빗물 (Loewen et al., 2005; Scott et al., 2006; Taniyasu et al., 2008), 강이나호숫물 (Boulanger et al., 2004; Stock et al., 2007), 폐수처리장 (wastewater treatment plant: WWTP) 유출수혹은슬러지 (Boulanger et al., 2005; Higgins et al., 2005; Schultz et al., 2006; Sinclair and Kannan, 2006), 해양포유류 (Houde et al., 2005), 사람혈액 (Weihe et al., 2008) 등다양한환경매체에서전구물질의중간산물들이검출되었다. 특히, PFOA (3.8 ng/l) 보다 더높은 8:2-FTUA 의최대농도 (8.6 ng/l) 가도시빗물에서검출되거나 (Scott et al., 2006), PFAs 가검출되지않은빗물에서 0.12~1 ng/l 의 FTOH 중간산물이검출되기도하였다 (Loewen et al., 2005). 또, 10 ng/l 이상의 FTA 나 FTUA 가극지방호숫물 (Stock et al., 2007) 이나 WWTP 유출수 (Sinclair and Kannan, 2006) 에서검출되었다. 전구물질의생분해결과로유입수에비해 WWTP 유출수에서 9-PFAs 와 PFOS 의총량이증가하였고 (Sinclair and Kannan, 2006), 슬러지에서의 PFOS 보다더높은농도의 PFOS 전구물질과대사중간산물들이검출되기도하였다 (Higgins et al., 2005). 이런결과들은 PFAs 의환경내분포와거동에있어서전구물질자체의분포와거동이또한중요한인자가될수있음을의미한다. 4) 생물농축 (bioaccumulation) PFs 는지방보다는단백질에결합하여축적되는경향이있어생체내에서 혈액, 담즙, 신장, 간, 알 (egg) 등에서높게검출된다 (Martin et al., 2003; Holmström and Burger, 2008). 따라서, 대부분의생물체 PFs 축적자료는혈액이나지방조직에서측정된농도에기초한다. 생물체모니터링자료들에대한최근의리뷰자료 (Houde et al., 2006; onder et al., 2008) 에따르면, PFs 의생물축적과관련된관측결과는다음의몇가지로요약될수있다. 첫째, PFAs 의생물축적 (bioaccumulation) 은불소로치환된탄소수가많은화합물일수록증가한다. 시화호에서식하는조류의알 (egg yolk) 에서측정된 PFAs 의농도는 PFOS PFUnDA PFDA PFNA PFDoDA PFOA 의검출분포를보였다 (Yoo et al., 2008). 특히, 11-PFA 인 PFUnDA 는 8-PFA 인 PFOA 보다 50~100 배높은값을보였다. 바이칼호물개등수생포유류에서도고분자 ( 9) PFAs 의두드러진생물축적이관측되었다 (Ishibashi et al., 2008). 둘째, 같은불소치환탄소수를갖는 PFSA 는 PFA 보다더높은생물축적경향을보인다. 자연계내생물들에서 PFOS 는 PFOA 보다우점적으로검출되며 (Houde et al., 2006), 어류및포유류등수서생태계먹이사슬에서 PFOA 는종종검출한계미만에서검출되는반면 PFOS 는물에서보다약 1,000 배정도축적된다 (de Vijver et al., 2003a; Mar-

11 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 153 tin et al., 2004; Kannan et al., 2005; Ishibashi et al., 2008). 셋째, PFOA 를포함하는 9-PFAs 와 7-PF- AS 는생물축적경향이보이지않는다. 조사된생물축적계수 (bioaccumulation factor, BAF) 와생물농축계수 (bioconcentration factor, BF) 는 PFOA 를포함한저분자 PFAs 와 PFOS 미만의저분자 PFAS 에서는 1,000 미만의값이관측되어이들물질그룹은생물증폭 (biomagnification) 도유의미하지않을것이라여겨지고있다 (onder et al., 2008). 반면, PFOS 는미시간호어류 - 밍크간에 11~23 (Kannan et al., 2002), Great Lake 먹이사슬내 어류 - 밍크 - 조류 간에 10~20 (Kannan et al., 2005) 의생물증폭계수 (biomagnification factor: BMF) 가, Lake Ontario 어류먹이사슬에서고분자 PFAs ( 8) 은 2~4.7 의 BMF 가관측되었다 (Martin et al., 2004). 넷째, 생물체에축적된 PFAs 의농도는생물체가노출된매체 ( 물, 대기, 퇴적물등 ) 에잔류하는전구물질의축적에의해영향받을수있다. 영양단계가더높은유영포식성어류 (pelagic predatory fishes) 보다저서생물들에서 2~3 배이상높은 PFOS 농도가관측되었다 (de Vijver et al., 2003b; Martin et al., 2004). 저서생물들에서의높은 PFOS 농도는퇴적물에서의높은 PFOS 농도뿐만아니라 PFOS 보다높은농도로잔류할수있는 PFOS 전구물질들이축적된결과일수도있다 (Higgins et al., 2005). 돌고래혈액에서 FTUAs 가관측되기도하였다 (Houde et al., 2005). 그러므로측정된생물체내 PFA 농도는노출된 PFAs 와전구물질 ( 생체축적후대사를통해 PFAs 로전환 ) 의합이라추정된다. 따라서, 측정된생물체와수체농도로부터 PFOS 와 PFAs 의 BF 나 BAF 를단순추정하기어렵다. 다섯째, PFAs 에대한인간의노출경로혹은축적경향은생태계내다른생물들과다를것이라추정된다. PFOS 및고분자 PFAs 가상대적으로우점적인분포를갖는야생생물에비해인간혈액에서는 PFOA, PFOS 가우점적이며상대적으로 PFOA 가더높은농도로검출된다 (Kannan et al., 2004). 가능한설명으로, 신장 (kidney) 에서의 PFOA 배출억제기능 (Harada et al., 2005b) 과 4.4 년이라는 PFOA 의긴인체내잔류시간 (Burris et al., 2002) 등이제시되었다. 반면, 다양한노출경로가가능한원인으로고려될수있다. AFFF 와같은 PFOS 의특별한오염원이없는일반환경수체 (ambient water) 중의농도는 PFOA 가 PFOS 보다높은농도로존재하는데 (Sinclair et al., 2006; Kim and Kannan 2007), 음용수 (drinking water) 에서도 PFOS 보다수배 - 수백배높은 PFOA 가 30~640 ng/l 수준으로검출되어음용수섭취가주요오염원으로간주될수도있다 (Skutlarek et al., 2006; Hölzer et al., 2008). 한편, Sinclair et al. (2007) 은요리조건으로가열된코팅된후라이팬과팝콘봉지에서 FTOHs 와 PFOA 를검출하여조리과정중의호흡노출가능성을제기하였고, 음식물용기를통한전이노출가능성이주요한경로일것이라의심되기도한다 (ES & T Online News, 2007). 5. 장거리이동 (LRT) 에대한가설들 PBT 외에 POPs 의중요한특징중하나가월경성장거리이동성 (trans-boundary LRTP) 이다. 비휘발성이고수용성인 PFAs 의극지방환경에서의검출을해석하기위하여여러가설들이제기되었다. 그러나, 해당가설들은배출원 (source), 배출량 (emission), 배출모드 (emission entry mode), 주요이동경로 (pathway) 등에서서로다른근거를제시하거나관측된값에대하여상반된해석을하기도하는등최근까지가장큰논쟁적이슈가되어왔다 (Table 3). 1) PAART (Precursors Alcohol Atmospheric Reaction and Transport) pathway Stock 등은북미의다양한지역에서측정된 11~ 165 pg/m 3 (FTOHs), 22~403 pg/m 3 (sulfonamides) 의대기중전구물질의농도가인구밀도와밀접한상관성을갖는다는것을보고하였다 (Stock et al., 2004). 이후의연구들 (Soeib et al., 2006; Jahnke et al. 2007a, b; Barber et al., 2007) 에서도도심 비도심 배경지역이라는뚜렷한농도구배를보였다. 특히, 실외대기보다수십 ~ 수백배높은농도가실내에서검출되어오염원으로써실내대기가의심되었다 (Shoieb et al., 2005; Barber et al., 2007). 이러한실내외대기중전구물질의농도구배는상업 / 산업용 polymer 나계면활성제물품에 0.04~3.8% 정도로높게함유된비결합잔류 FTOHs (Dinglas-

12 154 J. ENVIRON. TOXIOL. Vol. 23, No. 3 Table 3. omparison of hypotheses proposed for LRTP and environmental distribution of PFs (compiled from references in table) PAART (precursor alcohol atmospheric transport) Water-driven transport Direct/atmospheric transport Dominant source Precursor (indirect) PFAs (direct) PFAs (direct) PFAs - 2,700~5,000t (historically) Emission 1,500t (historically) 100~1,000 t/a for FTOHs amount precursors 30~200 t/a for FTOHs - Estimation from Estimation from atmospheric concentration emission inventory air (30%): soil (14%): Entry mode 100% air water (55%) for PFAs & air 100% air for precursors Transport pathway atmospheric Water-current atmospheric/water-splash Proposed evidences Estimation Power (to the Arctic) Disproof References deposition flux Predicted air conc. presence of volatile precursors and its intermediates in air atmospheric precursors source-dependent distribution PFAs production from precursor oxidation long lifetime (20~50 days) of precursors dominant presence of linearchain PFAs in arctic environment fast response to PFAS emission reduction long-chain PFAs detection in the Arctic ice-snow 0.4 t/yr (air/ftohs only) 1) 0.1~0.59 t/yr (snow) 2) similar with HB 38~385 pg/m 3 source dependent distribution of PFAs (urban rural) greater precursors conc. than predicted no decrease of atmospheric sulfonamides PFOA PFNA in rain Ellis et al., 2003, 2004 Martin et al., 2004 D Won et al. Young et al. Wallington et al., 2006 dominance of PFAs direct emission when estimated emission inventory similarity of ocean water conc. with measured similarity of PFO doubling time (7~10 yrs) in the Arctic biota with measured 8~23t/yr (urrent/pfo) 3) 2~12t/yr (urrent/pf O) 4) 9~20t/yr (urrent/pfo) +0.11~0.26 t/yr (air/ftoh) 5) 20~230t/yr (urrent/pfo) +0.19~0.23 t/yr (air/ FTOHs+sulfonamides) 6) 20~90 pg/l (Armitage et al.) 50~70 pg/l (Wania) 2~30 pg/m 3 (Wania) all precursor-related observations very fast biological response to PFAS emission reduction FTOHs-originated PFAs ratio in mountain lake water Prevedouros et al., 2006 Armitage et al. Wania, 2007 Schenker et al., 2008 greater PFAs conc/deposition in urban area (source-dependent distribtution) splashing of aerosol containing greater PFO PFOA PFNA in rain fast partitioning from water to air (K aw~ ; t 1/2~7s) possibility of low rain scavenging all precursor-related observations & waterdriven transport based fate and distribution Harada et al., 2005 Kim and Kannan, 2007 Ju et al., 2008 McMurdo et al., ) Wallington et al., 2006; 2) Young et al., 2008; 3) Armitage et al., 2006; 4) Prevedouros et al., 2006; 5) Wania, 2007; 6) Schenker et al., 2008

13 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 155 Panlilio et al. 2006) 가쉽게휘발되어대기로이동하는것이원인이될수있음이제기되었다 (Ellis et al., 2004). 대기에서의광화학및산화반응을통해다양한중간산물 (intermediates) 을거쳐최종적으로 FTOHs 로부터 1~10% (Ellis et al., 2004), sulfonamides 로부터 1~45% (Martin et al., 2006) 의안정적인 PFAs- 특히, 동량의이웃한탄소수를갖는화합물의생성 - 가생성되며, 장거리이동하기에충분한 20 일 (FTOHs)(Ellis et al., 2003) 과 20~50 일 (sulfonamides)(martin et al., 2006) 의대기잔류시간 (life-time) 을갖는것으로알려졌다. 결과적으로, 극지방이나배경지역 (remote area) 의대기나빗물에서전구물질과중간산물등이검출되었다. 이런관측결과로부터 전구물질의배출 / 분해 / 대기를통한이동 이라는 PAART 가설이제기되었다. 특히, Ellis 등은대기잔류시간과측정된대기농도로부터 100~1,000 톤 / 년의 FTOHs 배출량을추정하였고 (Ellis et al., 2004), 이배출량 (1,000 톤 / 년, 8 : 2- FTOH) 를이용하여대기로부터북극환경에침적되는속도를 0.4 톤 / 년으로추정하였다 (Wallington et al., 2006). 이가설을증명하는몇가지관측근거들로써, 1) PFAS 계열의생산금지이후북극수서포유류 (Butt et al., 2007) 와눈 (Young et al., 2007) 에서관측된 PFOS 농도의즉각적인감소경향, 2) 북극환경에서관측되는환경에서관측되는선형이성체의압도적출현 (linear branched isomers) (De Silva and Mabury, 2004; Young et al., 2007), 3) 극지방눈에서의 PFDA, PFUnDA 와같은고분자 PFAs 의검출 (Young et al., 2007), 4) 북극생물체내에서측정된 PFOA/PFNA 비율 (PFOA PFNA) 등이제시되었다 (Martin et al., 2004). 반면에, PAART 이론만으로설명할수없는측정결과와다매체거동모형의예측결과가제시되었다. 예컨대, 배출량조사자료 (emission inventory) 에의한추정치 (30~200 톤 / 년 )(Prevedouros et al., 2006; Armitage et al., 2006; Wania, 2007) 보다 5 배이상많은양이 PAART 가설에의해추정되었는데, 해당배출량 (100~1,000 톤 / 년 ) 을사용할경우예측된북극대기농도는관측된농도 (Shoieb et al., 2006) 보다 10 배정도높다 (Wallington et al., 2006). 또, 대기중전구물질의대기분해과정을고려했을때, NO x 농도가높은도심지역보다비도심지역 ( 혹은배경 지역 ) 에서더높은 PFAs 농도가예측 (Wallington et al., 2006) 되었음에도불구하고오히려도심지역에서비도심지역으로갈수록감소하는농도구배가관측되었다 (Scott et al., 2006; Kim and Kannan, 2007). 생산중단에따른극지방환경시료에서의즉각적인 PFOS 농도의감소경향에도불구하고중 - 고위도지역대기에서측정된 sulfonamide 의농도는감소하지않았다 (Barber et al., 2007; Jahnke et al., 2007a, b). 2) Direct emission and water-driven transport pathway 친수성인 PFAs의물리화학적특성, 상대적으로높은수체중농도 (Hansen et al., 2002; Saito et al., 2004; Rostkowski et al., 2006; So et al. 2007), 그리고간접배출보다많게추정된직접배출 (Prevedouros et al., 2006) 등이 직접배출 (PFAs) 과연이은해류를통한장거리이동 가설의기초가되었다. 유럽주요강하구에서측정된 PFOA농도로부터추정된 14톤 / 년은배출량조사로부터추정된유럽내배출량과유사하였다 (McLachlan et al., 2007). 또, Prevdouros 등에의해추정된직접배출량 (Prevedouros et al., 2006) 과해류이동만을고려한다매체모형은극지방에서 PFOA농도가 2배에도달되는시간 (doubling time) 을관측치 (Smithwick et al., 2006) 와유사한 7.5~10년으로예측하였다 (Armitage et al., 2006). 간접배출 (FTOHs)/ 대기이동 과 직접배출 (PFOA)/ 해류이동 을모두포함한모형들은북극에도달되는총량 ( 혹은유입량 ) 에대한기여도에서후자가전자보다 10~100배큰것으로평가하였다 (Wania, 2007; Schenker et al., 2008) (Table 3). 또, 배출량조사자료 (Prevedorous et al., 2006; therein) 에기초하고 해류를통한이동 이포함되었을때극지방에서관측된해수농도 (PFOA; 52~338 pg/l) (Yamashita et al., 2008) 와대기농도 (tftohs: 7~55 pg/m 3 )(Shoeib et al., 2006) 를더잘예측하였다. 그러나, 북극에서관측된배출감소에따른 PFOS 농도의즉각적감소 (Butt et al., 2007), 고도에따른대기중전구물질농도의증가와산정상호수에서관측되는 PFOA-PFNA의유사한비율 (Loewen et al., 2008), 도심대기에서관측되는 PFOA의높은농도 (Harada et al., 2005a; Barber et al., 2007) 등

14 156 J. ENVIRON. TOXIOL. Vol. 23, No. 3 은 PAART 가설의기여와또다른이동경로 ( 즉, 직접배출 - 대기이동 ) 의기여가능성을남겨두고있다. 3) Direct emission and atmospheric transport pathway 고려될또다른이동경로는 직접배출 (PFAs)/ 대기이동 경로이다. 대기와접한해수미세표면층 (microlayer) 에서의 PFOA와 PFOS농도는표층수 (subsurface water) 에서의농도보다수 ~ 수백배높은값이관측되었다 (Ju et al., 2008). 최근의에어로졸생성실험에따르면 (McMurdo et al., 2008), 수표면으로부터발생한에어로졸상의농도는표층수보다 80배정도의높은값을가지며, 에어로졸에녹아있는 PFO - 는매우빠르게 (t 1/2 =7.2s) 대기기체상으로분배하는것이관측되었다. 이결과로부터첫째, 알려진강우에의한세정효율 (rain-scavenging half-life; 6~17 day) (Flanklin, 2002; Wallington et al., 2006) 이과대평가되었을수있다는것, 둘째수체가반드시영구적인소멸처 (sinker) 로써만작용하는것이아니라대기에대한오염원 (source) 으로작용할수있다는것, 셋째수체에서기인한기체상 PFOA의장거리이동의결과로기존의 LRT (PAART, direct/water-transport) 에덧붙여 직접배출 / 대기이동 도중요한장거리이동경로일수있다는것이제기되었다. PAART 가설에의해예측되는것보다 100배낮은대기중 FTOH-PFOA 비율 (Kim and Kannan, 2007) 과함께도심대기에서의관측된높은 PFOA 농도 (Harada et al., 2005a; Barber et al., 2007) 는대기로의직접배출및대기이동경로의중요성을제시하였다. 미국의지역별상세배출량조사자료에근거해 FTOHs와 PFOA의대기로의배출을모두포함하였을때, 관측된것과유사한 도심 비도심 이라는농도구배가잘예측되었다. 배출량조사에서는대기로의배출이전체의 30% 에달하는것으로예측되었다 (Prevedouros et al., 2006). 4) 기타 ( 전구물질형태로수체로유입 / 분해 / 수체이동 ) 높은함량으로산업용 polymer나계면활성제물품등에비결합잔류물질로함유되어있는전구물질들 (Dinglasan-Panlilio et al., 2006) 은세척및청소과정중에대기뿐만아니라수체로직접배출될수있다. 앞서기술하였듯이, 수체로유입된전구물 질들은가수분해및생분해등을통해중간체를거쳐 PFAs 로전환된다. 그결과로폐수처리장의폐수와슬러지에서고농도의중간산물들이검출되는데이분해과정이수체중 PFAs 의농도를증가시킬것으로추정되고있다 (Higgins et al., 2005; Schultz et al., 2006). 이전구물질들의생분해로폐수처리장의유출수에서의고분자 PFAs 와 PFOS 의총량이유입수에서보다증가했다는직접적증거가제시되었다 (Sinclair and Kannan, 2007). 그러나, 전구물질들의분해로발생하는중간체들의물리화학적특성, 거동에대해서는아직잘알려져있지않다. 결론및전망 환경에서검출되는 PFs 분포와거동은다양한직 / 간접배출원에의해영향받을수있다. 생산금지이후에도여전히감소하지않는대기농도가관측되었다. 특히, 하천수 PFAs 에대한표면유출수 (surface runoff water) 의상대적기여도가하수처리장배출수보다높아특정되지않은비점배출원의중요성이강조되기도한다 (Kim and Kannan, 2007; Zushi et al., 2008). 또, fluoropolymer 자체가분해되어배출원으로작용할것이라는명백한증거가없음에도불구하고여전히 polymer 의열분해등은 PFAs 에대한잠재적배출원으로간주되기도한다 (Ellis et al., 2001). 교통량이많은도로변의대기에서검출된높은 PFOA 농도로부터차량에사용되는 PFs 관련물질들이잠재적배출원으로토의되기도하였다 (Harada et al., 2005a). 따라서, 소각이나매립혹은이동오염원과같은알려지지않은잠재적오염원이더조사될필요가있다. 결론적으로 LRT 및거동에영향을주는경로 (pathways) 는다음과같이간접배출, 직접배출, 해류이동, 대기이동의조합에의해설명될수있다 (Fig. 5). 해류를통한이동은 1) 표층수로 PFAs 의배출 (discharge) 과해류를통한이동 (transport), 2) 대기로배출된 PFAs 의표층수로이동과해류를통한이동, 3) 전구물질의표층수로배출, PFAs 로전환 (transformation) 그리고이동으로규정되고, 대기를통한이동은 1) 대기로 PFAs 의배출 (discharge) 그리고이동, 2) 전구물질의대기로배출, PFAs 로

15 September 2008 Kim : 과불소화화합물 (PFs) 의환경거동과분포 157 전환, 그리고이동, 3) PFAs 의표면 - 대기간이동그리고연속적인대기를통한이동등으로구성된다. 특정경로를통해서만설명되지않으며, 해당지역의 PFAs 오염의주요경로는지역적특성 ( 대기중 NO x 농도, 오염원지역으로부터의거리, 오염원유무 ) 에의해결정된다. 특히, 잠재적인오염원으로써전구물질의중간체에대한거동및특성이더조사될필요가있다. 최근에야대사체의종류와물리화학적특성을반영하는모형들이개발되고있다. 전체거동에있어서퇴적물이나토양에잔류하는양이무시될수는없음에도불구하고고체상매체 (geosolids) 에대한관측은매우미미하다. 또, 지구적규모의환경모형들에서토양내체류에의한장거리이동억제효과는 대기 - 토양 간접촉면보다훨씬큰 대기 - 대양 간접촉면때문에실제보다과소평가되었을가능성이있다 년초부터시작되는 PFAs 농도의감소경향은환경시료뿐만아니라인체시료 (Spliethoff et al., 2008) 에서도관측되고있다. 그러나, 생산감소에대한환경매체중농도나노출의즉각적감소가가능할것인가에대해서는여전히논란이되고있다. 예컨대, Wania 는직접배출되어수체로이동하거나간접배출되어대기로이동하는경로에관계없이북극환경에서의농도는배출감소이후수년에서수십년동안감소하지않고지연된다고예측하였다 (Wania, 2007). 북극환경과달리, 인간노출의감소는배출감소에따른훨씬더즉각적인반응의결과일수있다. 그러나, 그반응속도는노출경로에따라달라진다. 인간의 PFA 에대한노출경로로써상대적기여도가큰것으로 음식물섭취 (Tittlemier et al., 2007) 나 음용수섭취 (Harada et al., 2003; Hölzer et al., 2008) 가제안되었다. 수은이나기존의 POPs 와달리가식부에미량으로축적됨에도불구하고여전히어류다소비군에서는어류의섭취가주요노출경로로발표되기도하였다 (Falandysz et al., 2006). 반면, 전구물질의높은실내농도나도로변에서관측된높은 PFAs 농도로부터호흡에의한노출경로가중요하게평가되기도하며 (Harada et al., 2006), 포장재로부터식품으로의전이과정 (D Eon and Mabury, 2007; Sinclair et al., 2007) 이중요한노출경로로제기되기도하였다. 요컨대 PFs 배출원, 환경거동및노출경로에 Polymers FTOH Textiles Sulfonamides FP manufacture Others PFAs PFAS leaning FTOHs/FOSEs PFAs/PFAS WWTP Degradation & Volatilization AFFF degradation Emission Aerosol splashing PFOS Discharge Gas FTOHs/FOSEs Oxidation PFAs/PFAS Air Water FTOHs/FOSEs PFAs/PFAS Particle Soil Rain Degradation Food? Bird/Humans FTOHs/FOSEs Degradation? PFAs/PFAS Fishes FTOHs/FOSEs Degradation? PFAs/PFAS onsumer products Fig. 5. Pathways contributing to environmental distribution and long range transport of PFs. Question mark (?) means the process that have a little of evidences but are suspected to happen (AFFF indicates aqueous fire-fighting film foam and WWTP is wastewater treatment plant. see the Appendix for chemical abbreviation).

16 158 J. ENVIRON. TOXIOL. Vol. 23, No. 3 대한불확실성이여전히존재하며그불확실성을해소하려는노력은이들물질에대한생태계및인간의노출정도를정확히평가하기위해서필수불가결하다. 그러나, 국내연구는환경매체내오염수준과인체에대한 PFs 의노출수준을조사하는초보적단계에있다. 국내에서요구되는향후연과과제들을정리하면다음과같은것들이고려될수있다. 첫째, 배출원과배출량특성에대한연구가선행될필요가있다. 전술하였다시피, 해당지역의 PFAs 오염수준이나오염경로는지역적특성 ( 오염원유무와특성, 오염원지역으로부터의거리, 대기중 NO x 농도 ) 에의해크게좌우된다. 특히, PFs 의물질그룹별생산방식과환경거동특성이다르기때문에배출원별특성이조사될필요가있다. 3M 의 PFs 물질생산금지선언이후, 2000 년초에 Sulfonate- 계열의 PFs ( 즉, PFAS) 는수입이되지않았지만 Telomer- 계열 PFs ( 즉, FTOHs 와그로부터기인한 PFAs) 는 DuPont, Asahi Glass, Daikin 등으로부터지속적으로수입된것으로알려져있다 (Kim et al., 2007). 둘째, 전구물질과그분해산물 (PFAs 나 PFSA) 은거동특성이다르므로해당물질들이함께고려되어조사될필요가있다. 그러기위해서는전구물질들에대한시료채취및분석기술의확보가선행되어야한다. 현재국내연구는 PFOA 와 PFOS 로만국한되는경향이있다. 셋째, 주요노출경로별기여도가평가되어야한다. 현재국민혈중 PFOA, PFOS 오염수준이조사되고있으나어떤경로를통해얼마나유입되는지는조사되고있지않다. 일차적으로 음용수, 실내공기, 음식물 등을통한노출이평가될필요가있다. 넷째, PFOA, PFOS 의공산품함유규제에대한대응으로이들물질의사용규제및관리방안등이마련될필요가있다. 이들물질은유럽연합 (EU) 의전기전자제품내특정유해물질의사용에대한제한 (Restriction of the use of certain hazardous substances in electrical and electronic equipment: RoHS) 에포함될전망이다. 감사의글 This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF ). 참고문헌 환경부. 보도자료 -PFOS 의국내오염수준, 선진국에비해낮은수준, M. Material Safety Data Sheet for F-203F Light Water Brand Aqueous Film Forming Foam, 3M o., London, ON, anada, M. Soil Adsorption/Desorption Study of Potassium Perfluorooctane Sulfonate (PFOS); 3M: St. Paul, MN, U.S. Environmental Protection Agency Docket AR a 030, Armitage J, ousins IT, Buck R, Prevedouros K, Russell MH, MacLeod M and Korzeniowski SH. Modeling global-scale fate and transport of perfluorooctanoate emitted from direct sources, Environ Sci Technol 2006; 40: Arp HPH, Niederer and Goss K-U. Predicting the partitioning behavior of various highly fluorinated compounds, Environ Sci Technol 2006; 40: Barber JL, Berger U, aemfa, Huber S, Jahnke A, Temme and Jones K. Analysis of per- and polyfluorinated alkyl substances in air samples from Northwest Europe, J Environ Monit 2007; 9: Barton A, Butler LE, Zarzecki J, Flaherty J and Kaiser M. haracterizing perfluorooctanoate in ambient air near the fence line of a manufacturing facility: omparing modeled and monitored values, Air & Waste Manage Assoc 2006; 56: Biegel LB, Hurtt ME, Frame SR, O onnor J and ook J. Mechanisms of extrahepatic tumor induction by peroxisome proliferators in male D rats, Toxicol Sci 2001; 60: Boulanger B, Peck AM, Schnoor JL and Hornbuckle K. Mass budget of perfluorooctane surfactants in Lake Ontario, Environ Sci Technol 2005; 39: Boulanger B, Vargo J, Schnoor JL and Hornbuckle K. Detection of perfluorooctane surfactants in Great Lakes water, Environ Sci Technol 2004; 38(15): Brace NO. Long chain alkanoic and alkenoic acids with perfluoroalkyl terminal segments, J Org hem 1962; 27: Burris JM, Lundberg JK, Olsen G, Simpson and Mandel J. Interim Report No. 2, Determination of Serum Half- Lives of Several Fluorochemicals; U.S.EPA Public Docket; 3M: St. Paul, MN, 2002.

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