Analytical and Toxicological Analysis of Perfluorinated Compounds Present in the Environment
Date
2011-10-17
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Doctoral
Abstract
Perfluorinated compounds (PFCs) have been produced in relatively large quantities since
the 1950s for a wide range of applications such as carpet coatings, food packaging, shampoos,
paper, and fire-fighting foams. PFCs are globally ubiquitous in both remote and urban
environments. PFCs are present in various matrices including; human blood (whole, plasma and
serum), sediments, water, and wildlife. The primary objective of the research described herein is
to address data-gaps which have hindered attempts to effectively characterize the risks of PFCs
to both humans and wildlife. The hypotheses of this thesis are that (1) current analytical
methods for the detection of PFCs are flawed and are in need of improvement, (2) concentrations
of PFCs in South Korea are elevated and there is associated risk to both humans and wildlife, and
(3) model PFCs such as perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) are
poor predictors of effects caused by exposure to other PFCs.
Accurate and precise measurement is essential for effective decision making regarding
the production and usage of PFCs. Many issues such as impure standards (either homologs of
the standards or unrelated compounds), interactions between isotopically labeled and non-labeled
analytes, and the presence of multiple isomers complicate the accurate and precise quantification
of PFCs. It has been reported that the relative response factors of isotopically labeled standards
and unlabeled standards of the same PFC could be different. Individual (100 ng mL-1) solutions
of PFOA and PFOS were analyzed using HPLC-MS/MS under negative-ion-electrospray to
detect any impurities present down to 0.5 to 0.1% relative to the major component. Purity of the
standards ranged from approximately 86% to ≥ 97%. Standard solutions of unlabeled and
isotopically labeled materials were analyzed to compare response factors of isotopically labeled
analytes versus their non-labeled counterparts in three different matrices at equivalent
concentrations: organic solvent (methanol), serum extract, and water present individually and
iii
concurrently. Not all labeled analytes have the same response factor as their non-labeled
complement, and in at least one case the matrix in which the standard is present may cause
significant suppression of response. Standard solutions of electrochemical fluorination produced
PFOA and PFOS were quantified under multiple reaction monitoring (MRM) mode, using
calibration curves prepared from standards consisting primarily of linear standards only, and our
results have shown that in general, the use of linear only standards may cause under prediction of
concentrations, and that the working range of these standards may be limited.
Previous studies have reported concentrations of PFCs in Asia to be relatively great and
in particular Korea has shown to have some of the highest environmental levels ever detected.
Despite this fact, relatively little was known about sources, distribution and fate among matrixes.
In 2008 and 2009 soil, sediment, water, and biota were collected from the western coast of Korea
and were analyzed to determine occurrence and sources of PFCs. PFCs were significantly
concentrated in some water and biological samples, while concentrations of PFCs in soils and
sediments were relatively low. The most widely detected compound was found to be PFOS,
with maximum in water of 450 ng/L and in fish of 612 ng/g, dw. PFOS in water and biota were
both less than those thought to cause toxicity, however; in both cases concentrations were within
a factor of 10 to a possible toxicity threshold concentration. Although in general the
concentrations of PFCs in all three media were reduced from 2008 levels, the calculated
bioconcentration factor for PFOS in fish was among the highest ever reported. Overall, the
detection of PFCs at relatively great concentrations in various environmental matrices from this
region of Korea suggests that further study and characterization of these chemicals and their
potential risk to both humans and wildlife is needed.
iv
While PFOS has been extensively studied, other PFCs including replacement chemicals
such as perfluorobutanesulfonate (PFBS) and perfluorobutyrate (PFBA), have not been well
characterized. Despite the relative lack of data available describing these other PFCs it has been
assumed that they will cause similar or lesser effects than PFOS. To test the null hypothesis that
all PFCs, including shorter chain-length replacements, act via similar modes of action, rat H4IIE
cells were exposed to 10 PFCs, all of which are routinely found in the environment, and the
mRNA abundance of 7 target genes was quantified using real-time PCR. Significant changes in
mRNA abundance were observed. Effects caused by the shorter chain replacement chemicals
differed significantly from those caused by PFOS or PFOA. Furthermore, not all of the PFCs
caused the same effects, and changes could not simply be attributed to chain-length or functional
group. These differences support that these replacement chemicals do not act through the same
mechanisms as the more studied PFOS and PFOA.
Description
Keywords
Toxicology, PFCs
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Graduate Studies and Research
Program
Toxicology