6 research outputs found
Characterization of Two Passive Air Samplers for Per- and Polyfluoroalkyl Substances
Two passive air sampler (PAS) media
were characterized under field
conditions for the measurement of per- and polyfluoroalkyl substances
(PFASs) in the atmosphere. The PASs, consisting of polyurethane foam
(PUF) and sorbent-impregnated PUF (SIP) disks, were deployed for over
one year in parallel with high volume active air samplers (HV-AAS)
and low volume active air samplers (LV-AAS). Samples were analyzed
for perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane sulfonic
acids (PFSAs), fluorotelomer alcohols (FTOHs), fluorotelomer methacrylates
(FTMACs), fluorotelomer acrylates (FTACs), perfluorooctane sulfonamides
(FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs). Sampling
rates and the passive sampler medium (PSM)-air partition coefficient
(<i>K</i><sub>PSMāA</sub>) were calculated for individual
PFASs. Sampling rates were similar for PFASs present in the gas phase
and particle phase, and the linear sampling rate of 4 m<sup>ā3</sup> d<sup>ā1</sup> is recommended for calculating effective air
sample volumes in the SIP-PAS and PUF-PAS for PFASs except for the
FOSAs and FOSEs in the PUF-PAS. SIP disks showed very good performance
for all tested PFASs while PUF disks were suitable only for the PFSAs
and their precursors. Experiments evaluating the suitability of different
isotopically labeled fluorinated depuration compounds (DCs) revealed
that <sup>13</sup>C<sub>8</sub>-perfluorooctanoic acid (PFOA) was
suitable for the calculation of site-specific sampling rates. Ambient
temperature was the dominant factor influencing the seasonal trend
of PFASs
Heterogeneous OH Initiated Oxidation: A Possible Explanation for the Persistence of Organophosphate Flame Retardants in Air
Heterogeneous reactions between OH
radicals and emerging flame
retardant compounds coated on inert particles have been investigated.
Organophosphate esters (OPEs) including triphenyl phosphate (TPhP),
tris-2-ethylhexyl phosphate (TEHP), and tris-1,3-dichloro-2-propyl
phosphate (TDCPP) were coated on (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> particles and exposed to OH radicals in a photochemical flow
tube at 298 K and (38.0 Ā± 2.0) % RH. The degradation of these
particle-bound OPEs was observed as a result of OH exposure, as measured
using a Time-of-Flight Aerosol Mass Spectrometer. The derived second-order
rate constants for the heterogeneous loss of TPhP, TEHP, and TDCPP
were (2.1 Ā± 0.19) Ć 10<sup>ā12</sup>, (2.7 Ā±
0.63) Ć 10<sup>ā12</sup>, and (9.2 Ā± 0.92) Ć
10<sup>ā13</sup> cm<sup>3</sup> molecule<sup>ā1</sup> s<sup>ā1</sup>, respectively, from which approximate atmospheric
lifetimes are estimated to be 5.6 (5.2ā6.0), 4.3 (3.5ā5.6),
and 13 (11ā14) days. Additional coating of the OPE coated particles
with an OH radical active species further increased the lifetimes
of these OPEs. These results represent the first reported estimates
of heterogeneous reaction rate constants for these species. The results
demonstrate that particle bound OPEs are highly persistent in the
atmosphere with regard to OH radical oxidation, consistent with the
assumption that OPEs can undergo medium or long-range transport, as
previously proposed on the basis of field measurements. Finally, these
results indicate that future risk assessment and transport modeling
of emerging priority chemicals with semi- to low-volatility must consider
particle phase heterogeneous loss processes when evaluating environmental
persistence
Improved Characterization of GasāParticle Partitioning for Per- and Polyfluoroalkyl Substances in the Atmosphere Using Annular Diffusion Denuder Samplers
Gas-phase perfluoroalkyl carboxylic acids (PFCAs) sorb
strongly
on filter material (i.e., GFF, QFF) used in conventional high volume
air samplers, which results in an overestimation of the particle-phase
concentration. In this study, we investigated an improved technique
for measuring the gasāparticle partitioning of per- and polyfluoroalkyl
substances (PFASs) using an annular diffusion denuder sampler. Samples
were analyzed for 7 PFAS classes [i.e., PFCAs, perfluoroalkane sulfonic
acids (PFSAs), fluorotelomer alcohols (FTOHs), fluorotelomer methacrylates
(FTMACs), fluorotelomer acrylates (FTACs), perfluorooctane sulfonamides
(FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs)]. The measured
particulate associated fraction (<i>Ī¦</i>ā²)
using the diffusion denuder sampler generally followed the trend FTACs
(0%) < FTOHs (ā¼8%) < FOSAs (ā¼21%) < PFSAs (ā¼29%)
< FOSEs (ā¼66%), whereas the <i>Ī¦</i>ā²
of the C<sub>8</sub>āC<sub>18</sub> PFCAs increased with carbon
chain length, and ranged from 6% to 100%. The ionizability of some
PFASs, when associated with particles, is an important consideration
when calculating the gasāparticle partitioning coefficient
as both ionic and neutral forms can be present in the particles. Here
we differentiate between a gasāparticle partitioning coefficient
for neutral species, <i>K</i><sub>p</sub>, and one that
accounts for both ionic and neutral species of a compound, <i>K</i><sub>p</sub>ā². The measured <i>K</i><sub>p</sub>ā² for PFSAs and PFCAs was 4ā5 log units higher
compared to the interpolated <i>K</i><sub>p</sub> for the
neutral form only. The measured <i>K</i><sub>p</sub>ā²
can be corrected (to apply to the neutral form only) with knowledge
of the p<i>K</i><sub>a</sub> of the chemical and the pH
of the condensed medium (āwetā particle or aqueous aerosol).
The denuder-based sampling of PFASs has yielded a robust data set
that demonstrates the importance of atmospheric pH and chemical p<i>K</i><sub>a</sub> values in determining gas-particle partitioning
of PFASs
Phosphorus-Containing Fluorinated Organics: Polyfluoroalkyl Phosphoric Acid Diesters (diPAPs), Perfluorophosphonates (PFPAs), and Perfluorophosphinates (PFPIAs) in Residential Indoor Dust
Indoor dust is thought to be a source of human exposure
to perfluorocarboxylates
(PFCAs) and perfluorosulfonates (PFSAs), but exposures to emerging
organofluorine compounds, including precursors to PFCAs and PFSAs
via indoor dust, remain unknown. We report an analytical method for
measuring several groups of emerging phosphorus-containing fluorinated
compounds, including polyfluoroalkyl phosphoric acid diesters (diPAP),
perfluorophosphonates (PFPA), and perfluorophosphinates (PFPIA), as
well as perfluoroethylcyclohexane sulfonate (PFECHS) in indoor dust.
This method was used to analyze diPAP, PFPA, and PFPIA levels in 102
residential dust samples collected in 2007ā2008 from Vancouver,
Canada. The results indicated a predominant and ubiquitous presence
of diPAPs (frequency of detection 100%, mean and median Ī£diPAPs
7637 and 2215 ng/g). Previously measured median concentrations of
perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and fluorotelomer
alcohols (FTOHs) in the same samples were 14ā74 times lower
than Ī£diPAP levels, i.e. 71 ng/g PFOS, 30 ng/g PFOA, and 152
ng/g Ī£FTOHs. PFPAs and PFPIAs were detected in 62% and 85% of
samples, respectively, at concentrations nearly 3 orders of magnitude
lower than diPAPs (median 2.3 ng/g Ī£PFPAs and 2.3 ng/g Ī£PFPIAs).
PFECHS was detected in only 8% of dust samples. To the best of our
knowledge, this is the first report of these compounds in indoor dust.
In this study, diPAP concentrations represented 98% Ā± 7% of the
total measured analytes in the dust samples. Detection of diPAPs at
such high concentrations in indoor dust may represent an important
and as-yet unrecognized indirect source of PFCA exposure in humans,
given the identified biotransformation pathways. Identifying the sources
of diPAPs to the indoor environment is a priority for future research
to improve air quality in households
Airborne Precursors Predict Maternal Serum Perfluoroalkyl Acid Concentrations
Human exposure to persistent perfluoroalkyl
acids (PFAAs), including
perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and
perfluorooctanesulfonate (PFOS), can occur directly from contaminated
food, water, air, and dust. However, precursors to PFAAs (PreFAAs),
such as dipolyfluoroalkyl phosphates (diPAPs), fluorotelomer alcohols
(FTOHs), perfluorooctyl sulfonamides (FOSAs), and sulfonamidoethanols
(FOSEs), which can be biotransformed to PFAAs, may also be a source
of exposure. PFAAs were analyzed in 50 maternal sera samples collected
in 2007ā2008 from participants in Vancouver, Canada, while
PFAAs and PreFAAs were measured in matching samples of residential
bedroom air collected by passive sampler and in sieved vacuum dust
(<150 Ī¼m). Concentrations of PreFAAs were higher than for
PFAAs in air and dust. Positive associations were discovered between
airborne 10:2 FTOH and serum PFOA and PFNA and between airborne MeFOSE
and serum PFOS. On average, serum PFOS concentrations were 2.3 ng/mL
(95%CI: 0.40, 4.3) higher in participants with airborne MeFOSE concentrations
in the highest tertile relative to the lowest tertile. Among all PFAAs,
only PFNA in air and vacuum dust predicted serum PFNA. Results suggest
that airborne PFAA precursors were a source of PFOA, PFNA, and PFOS
exposure in this population
Polyfluorinated Compounds in Serum Linked to Indoor Air in Office Environments
We aimed to investigate the role of indoor office air
on exposure
to polyfluorinated compounds (PFCs) among office workers. Week-long,
active air sampling was conducted during the winter of 2009 in 31
offices in Boston, MA. Air samples were analyzed for fluorotelomer
alcohols (FTOHs), sulfonamides (FOSAs), and sulfonamidoethanols (FOSEs).
Serum was collected from each participant (<i>n</i> = 31)
and analyzed for 12 PFCs including PFOA and PFOS. In air, FTOHs were
present in the highest concentrations, particularly 8:2-FTOH (GM =
9920 pg/m<sup>3</sup>). FTOHs varied significantly by building with
the highest levels observed in a newly constructed building. PFOA
in serum was significantly correlated with air levels of 6:2-FTOH
(<i>r</i> = 0.43), 8:2-FTOH (<i>r</i> = 0.60),
and 10:2-FTOH (<i>r</i> = 0.62). Collectively, FTOHs in
air significantly predicted PFOA in serum (<i>p</i> <
0.001) and explained approximately 36% of the variation in serum PFOA
concentrations. PFOS in serum was not associated with air levels of
FOSAs/FOSEs. In conclusion, FTOH concentrations in office air significantly
predict serum PFOA concentrations in office workers. Variation in
PFC air concentrations by building is likely due to differences in
the number, type, and age of potential sources such as carpeting,
furniture, and/or paint