30 research outputs found
Model for Screening-Level Assessment of Near-Field Human Exposure to Neutral Organic Chemicals Released Indoors
Screening organic
chemicals for hazard and risk to human health
requires near-field human exposure models that can be readily parametrized
with available data. The integration of a model of human exposure,
uptake, and bioaccumulation into an indoor mass balance model provides
a quantitative framework linking emissions in indoor environments
with human intake rates (<i>iR</i>s), intake fractions (<i>iF</i>s) and steady-state concentrations in humans (<i>C</i>) through consideration of dermal permeation, inhalation,
and nondietary ingestion exposure pathways. Parameterized based on
representative indoor and adult human characteristics, the model is
applied here to 40 chemicals of relevance in the context of human
exposure assessment. Intake fractions and human concentrations (<i>C</i><sub>U</sub>) calculated with the model based on a unit
emission rate to air for these 40 chemicals span 2 and 5 orders of
magnitude, respectively. Differences in priority ranking based on
either <i>iF</i> or <i>C</i><sub>U</sub> can be
attributed to the absorption, biotransformation and elimination processes
within the human body. The model is further applied to a large data
set of hypothetical chemicals representative of many in-use chemicals
to show how the dominant exposure pathways, <i>iF</i> and <i>C</i><sub>U</sub> change as a function of chemical properties
and to illustrate the capacity of the model for high-throughput screening.
These simulations provide hypotheses for the combination of chemical
properties that may result in high exposure and internal dose. The
model is further exploited to highlight the role human contaminant
uptake plays in the overall fate of certain chemicals indoors and
consequently human exposure
Persistent Organohalogens in Paired Fish Fillet and Eggs: Implications for Fish Consumption Advisories
Fish consumption is associated with
both health benefits from high-quality
proteins, minerals, vitamins, and fatty acids and risks from contaminants
in fish. Fish consumption advisories are issued by many government
agencies to keep exposure to contaminants at a safe level. Such advisories
are typically based on fillets and neglect consumption of other fish
parts such as eggs by certain subpopulations. To evaluate potential
for dietary exposure to toxic organic chemicals via fish eggs, we
analyzed polybrominated diphenyl ethers (PBDEs), polychlorinated naphthalenes
(PCNs), dioxin-like polychlorinated biphenyls (dlPCBs), and polychlorinated
dibenzodioxins/furans (PCDD/Fs) in paired fillet and eggs of fish
from a tributary to Lake Ontario, one of the North American Great
Lakes. All wet weight based concentrations in fish eggs were statistically
higher than in the paired fillet samples. In fish eggs, concentrations
of Σ<sub>14</sub>PBDEs, Σ<sub>14</sub>PCNs, and Σ<sub>12</sub>dlPCBs were 41–118, 0.3–1.7, and 30–128
ng/g wet weight (ww), respectively; Σ<sub>3</sub>PCDD/Fs and
total (dlPCB+ PCDD/Fs) toxic equivalents (TEQs) were 4–22 and
9–54 pg/g ww, respectively. In fillet samples, Σ<sub>14</sub>PBDEs, Σ<sub>14</sub>PCNs, and Σ<sub>12</sub>dlPCBs were 4–116, 0.05–0.66, and 6–85 ng/g,
respectively; Σ<sub>3</sub>PCDD/Fs and TEQs were 2–10
and 3.4–31 pg/g ww, respectively. In contrast, the fillets
had higher lipid normalized concentrations than the paired egg samples,
suggesting that these chemicals did not reach equilibrium between
the fillets and eggs. Accordingly, measured concentrations in eggs
or empirical relationship with fillet rather than prediction from
equilibrium partitioning model should be used to evaluate contaminant
exposure via consumption of fish eggs. For fatty fish from the lower
Great Lakes area, we suggest one fillet meal be reduced from the advised
fish consumption frequency for consumptions of 207 ± 37, 39 ±
2, 105 ± 51, and 119 ± 9 g fish eggs of brown trout, Chinook
salmon, Coho salmon, and rainbow trout, respectively
Semivolatile Organic Contaminants in the Hawaiian Atmosphere
An
air sampling campaign on the Island of Hawaii aimed to assess
background concentrations of semivolatile organic compounds (SVOCs)
over the Central Northern Pacific and to explore their distribution
along an altitudinal transect. XAD-resin-based passive air samplers
were deployed from May to September 2011 at six sites along a transect
from the northeastern coast to the Mauna Loa Observatory and at three
other island sites. By crossing the trade wind inversion, the transect
comprised the marine boundary layer and free troposphere. At the two
ends of the transect, flow-through samplers simultaneously sampled
air at monthly resolution. Elevated levels of dieldrin, chlordane-
and DDT-related pesticides, polycyclic aromatic hydrocarbons (PAHs),
and polybrominated diphenyl ethers (PBDEs) at two urban sites indicated
contributions from local sources. The composition of chlordane and
DDT-related residues indicated recent emissions. PAHs concentrations
that decline more rapidly with increasing elevation than those for
PBDEs are consistent with faster atmospheric degradation of PAHs.
SVOC levels on Mauna Loa were generally at the lower end of concentration
ranges reported for remote sites, including the Arctic. However, in
contrast to the Arctic, long-range atmospheric transport is deemed
less important than human-induced material flow as the source of SVOCs
to the island’s atmosphere
Carboxypeptidase M augments kinin B1 receptor signaling by conformational crosstalk and enhances endothelial nitric oxide output
The G protein-coupled receptors (GPCRs) are the largest class of membrane proteins that play key roles in transducing extracellular signals to intracellular proteins to generate cellular responses. The kinin GPCRs, named B1 (B1R) and B2 (B2R), are responsible for mediating the biological responses to kinin peptides released from the precursor kininogens. Bradykinin (BK) or kallidin (KD) are agonists for B2Rs, whereas their carboxypeptidase (CP)-generated metabolites, des-Arg(9)-BK or des-Arg(10)-KD, are specific agonists for B1Rs. Here, we review the evidence for a critical role of membrane-bound CPM in facilitating B1R signaling by its ability to directly activate the receptor via conformational crosstalk as well as generate its specific agonist. In endothelial cells, the CPM/B1R interaction facilitates B1R-dependent high-output nitric oxide under inflammatory conditions
Calibration and Application of a Passive Air Sampler (XAD-PAS) for Volatile Methyl Siloxanes
Because
the atmosphere is key to understanding the environmental
behavior of volatile methyl siloxanes (VMS), a variety of reliable
air sampling methods are needed. The purpose of this study was to
calibrate and evaluate an existing, polystyrene–divinylbenzene
copolymeric resin-based passive air sampler (XAD-PAS) for VMS. Sixteen
XAD-PAS were deployed for 7–98 days at a suburban site in Toronto,
Canada, while the VMS concentration in air was monitored by an active
sampling method. This calibration and a subsequent field test further
allowed for investigation of the temporal and spatial variability
of VMS in the region. Uptake in the XAD-PAS of octamethylcyclotetrasiloxane
(D4), decamethylcyclopentasiloxane (D5), and three linear VMS was
linear throughout the whole deployment period. Sampling rates were
between 0.4 and 0.5 m<sup>3</sup>/day. The XAD-PAS measured ∑VMS
concentrations ranged from nondetects in rural areas (<i>n</i> = 3), to 169 ± 49 ng/m<sup>3</sup> in the urban region (<i>n</i> = 21), to levels above 600 ng/m<sup>3</sup> at sewage
treatment plants (<i>n</i> = 2). Levels and composition
of VMS within the urban area were remarkably uniform in space. Levels,
but not composition, were highly variable in time and weakly correlated
with temperature, wind speed, and wind direction
Representative respiratory tracings.
<p>Representative respiratory tracings of airway pressure(Paw), esophageal pressure (Pes), intragastric pressure (Pgas),transpumonary pressure (PL),Airflow、abdominal muscles surface electromyography (EMGab)and diaphragmatic esophageal surface electromyography (EMGdi) in BIPAP<sub>SB</sub>,BIPAP<sub>AP</sub> group in representative animals. BIPAP<sub>SB</sub> = biphasic positive airway pressure with SB; BIPAP<sub>AP</sub> = biphasic positive airway pressure with abdominal muscles paralysis.</p
Chitosan/Phytic Acid Polyelectrolyte Complex: A Green and Renewable Intumescent Flame Retardant System for Ethylene–Vinyl Acetate Copolymer
We describe the preparation and characterization
of a green and
renewable polyelectrolyte complex (PEC) containing phosphorus, nitrogen
and carbon elements, based on the ionic complexation between chitosan
and phytic acid. Introduction of this PEC to ethylene–vinyl
acetate copolymer (EVA) leads to an improvement of the flame retardancy.
As for the EVA/PEC composites with 20.0 wt % of PEC (EVA/20PEC), the
char residue at 600 °C is 12 wt % higher than that of the pristine
EVA under nitrogen atmosphere. Compared to the pristine EVA, the peak
heat release rate and total heat release of EVA/20PEC show 249 W g<sup>–1</sup> and 5.6 kJ g<sup>–1</sup> decreases, respectively.
The char residue of EVA/20PEC is full and compact, demonstrating excellent
intumescent effect. Introduction of this PEC also contributes to a
slight increase of the Young’s modulus while maintains the
excellent ductility. This work provides a new approach for the development
of environmentally friendly intumescent flame retardant system
Histopathological examination.
<p>Representative appearances and photomicrographs of hematoxylineosin–stained lung sections (magnification ×200) from control group (A, n = 6), BIPAP<sub>SB</sub> = biphasic positive airway pressure with SB (B, n = 6), and BIPAP<sub>AP</sub> = biphasic positive airway pressure with abdominal muscles paralysis (C, n = 6).The control group had minimal alveolar congestion, and inflammatory cell infiltration. The BIPAP<sub>AP</sub> group showed mild thickening of the alveolar walls, alveolar congestion, and hemorrhage. In the BIPAP<sub>SB</sub> group, inflammatory cell infiltration, thickening of the alveolar walls, alveolar congestion, and more prominent hemorrhagic areas were observed.</p
Time course of the EELV.
<p>Time course of the end- expiratory lung volume (EELV) in experimental groups (n = 6 per group). BIPAP<sub>SB</sub> = biphasic positive airway pressure with SB; BIPAP<sub>AP</sub> = biphasic positive airway pressure with abdominal muscles paralysis; SB = spontaneous breathing; *P < 0.05, vs. other groups.</p
Acid-Catalyzed Synthesis of Trioxane in Aprotic Media
The effects of solvent, acid specificity,
acid concentration, added
salt, and reaction temperature on the yields of trioxane and formic
acid (byproduct) in paraformaldehyde + acid (or acid + salt) + aprotic
solvent were investigated. The mechanism that underlies the yield
of paraformaldehyde and the selectivity of trioxane was determined.
A highly practical and efficient synthesis of trioxane by a salt-mediated
and acid-catalyzed yield of paraformaldehyde in sulfolane media was
developed. The method increased the yield of paraformaldehyde by more
than 5 times and decreased the formic acid concentration by 10 times
compared to the commercial synthesis of trioxane in an aqueous reaction
system (formaldehyde + H<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>O)