Perfluorinated compounds (PFCs) are a group of emerging pollutants that have received
considerable attention recently. Besides the two well-known PFCs, perfluorooctane
sulfonate (PFOS) and perfluorooctanoate (PFOA), other perfluorinated acids, including
short-chain (< eight carbons) or long-chain (≥ eight carbons) sulfonates or carboxylates,
have been found in aqueous environment over the world. PFOS and PFOA have been
detected not only in raw waters, but also in treated drinking water from Germany, Italy,
Spain, Poland, Japan, Malaysia, Thailand, Vietnam and Canada. Because of the low
removal efficiency of PFCs by conventional drinking water purification processes like
coagulation, sedimentation and chlorination, other PFCs may also be present in purified
water, resulting in human exposure. Even though these PFCs usually occur at ppt levels,
contamination of PFCs in drinking water has nevertheless prompted concern in both
developed and developing countries, as water consumption occurs daily over the course
of a lifetime and PFCs are bioaccumulative and have half-lives up to several years,
resulting in chronic exposure to these compounds.
Recent development of a sensitive and accurate analytical method for trace analysis of 20
PFCs, including several short- and long-chain compounds and their precursors, enabled
their quantification in tap water samples collected from 2006−2008 in China, Japan, India,
USA and Canada. The target analytes of the present study included eight perfluoroalkyl
sulfonates (PFASs) and twelve perfluoroalkyl carboxylates (PFCAs), which were
separated, identified and quantified by employing solid phase extraction (SPE) together with high-performance liquid chromatography coupled with tandem mass spectrometry
(HPLC-MS/MS).
Of the measured PFCs, sixteen were present at detectable concentrations in tap water
samples: PFOS, perfluorohexane sulfonate (PFHxS), perfluorobutane sulfonate (PFBS),
perfluoropropane sulfonate (PFPrS), perfluoroethane sulfonate (PFEtS), perfluorooctane
sulfonamide (PFOSA), N-ethyl perfluorooctane sulfonamidoacetate (N-EtFOSAA),
perfluorododecanoic acid (PFDoDA), perfluoroundecanoic acid (PFUnDA),
perfluorodecanoic acid (PFDA), perfluorononanoate (PFNA), PFOA, perfluoroheptanoic
acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and
perfluorobutanoic acid (PFBA). Tap water from Japan contained the highest number of
detectable PFCs (sixteen PFCs), whereas only seven PFCs samples were detected in
samples collected from India. PFOS and PFOA were the two most frequently detected
PFCs, and were quantified in more than 80% of the tap water samples from China, Japan,
USA and Canada. However, these two compounds occurred in less than 40% of the
Indian tap water samples.
Tap water from Shanghai (China) contained the highest concentration of total PFCs
(mean = 130 ng/L), whereas samples from Toyama (Japan) contained only 0.612 ng/L of
total PFCs. Although waters from India usually contained relatively low concentrations
of PFCs, high level of PFHxS was measured in tap water from Chennai (n = 1),
indicating the presence of specific source(s) of PFCs influencing the quality of Indian tap
water. Distinct PFC composition profiles in the tap water samples from the various
countries were observed, likely because of variation in the production and usage of PFCs in these countries. Other than PFOS and PFOA, short chain PFCs like PFHxS, PFBS,
PFPeA and PFBA were prevalent in tap water samples, reflecting the importance of
identifying short-chain PFCs in tap water.
Comparison of PFC concentrations with provisional health advisory, health-based values
(HBVs) and advisory guidelines derived for PFOS, PFOA, PFBA, PFHxS, PFBS,
PFHxA and PFPeA by the U.S. EPA and Minnesota Department of Health (USA)
showed that the corresponding maximum measured concentrations of these compounds in
tap water from China, Japan, India, USA and Canada were all below these guideline
values. Risk quotients (RQs) of PFOS, PFOA, PFBA, PFHxS, PFBS, PFHxA and PFPeA
due to consumption of these tap water samples were less than unity, showing that there
may be no immediate risk posed to consumers by PFCs.
Based on a simplified one-compartment toxicokinetic model in which it was assumed that
PFCs were totally absorbed from the intestine, the estimated serum PFOS and PFOA
levels in were calculated for consumption of Chinese tap water and compared with
measured serum concentrations of PFCs in Chinese human blood samples reported by
previous studies. The results indicated that drinking PFC-contaminated tap water
contributed less than 1% of the serum PFOS concentrations in human blood from several
Chinese cities, with the exception of those from Nanjing, where 8.2% of serum PFOS
concentrations was found to be due to drinking water. However, tap water may be a
relatively significant exposure pathway of Chinese citizens to PFOA, as at least 13% of
PFOA in serum could be attributed to drinking tap water.
Boiling tap water before consumption is a common practice in China which may alter
PFC concentrations and composition profiles in tap water. Boiling water with a mixture
of 17 native PFC standards and 4 mass-labeled PFC standards for 15 minutes was shown
to cause a significant reduction in the concentrations of volatile PFCs such as PFOSA and
N-EtFOSAA, but the levels of perfluorinated acids were not significantly different after
boiling. Drinking boiled water, in turn, leaded to a change in PFC as this treatment may
help to minimize the exposure to volatile PFCs, although the exposure of the non-volatile
perfluorinated acid still occurred via the water consumption.
To conclude, PFCs have been identified and quantified in tap water from China, Japan,
India, USA and Canada, reflecting that PFC contamination in tap water is a global issue.
Risks associated to PFOS, PFOA, PFBA, PFHxS, PFBS, PFHxA and PFPeA in tap water
from these countries were low, but further studies should be carried out so as to
characterize the risks posed by PFC mixtures. Drinking PFC-contaminated tap water may
be a relatively important PFOA exposure pathway to Chinese and researches related to
the toxicokinetic of other PFCs should be performed in order to provide more
information for the estimation of contribution of drinking water to human PFC exposure.
| Date of Award | 2 Oct 2009 |
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| Original language | English |
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| Awarding Institution | - City University of Hong Kong
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| Supervisor | Kwan Sing Paul LAM (Supervisor) |
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