4 research outputs found
In Vivo Biotransformation Rates of Organic Chemicals in Fish: Relationship with Bioconcentration and Biomagnification Factors
In
vivo dietary bioaccumulation experiments for 85 hydrophobic
organic substances were conducted to derive the in vivo gastrointestinal
biotransformation rates, somatic biotransformation rates, bioconcentration
factors (BCF), and biomagnification factors (BMF) for improving methods
for bioaccumulation assessment and to develop an in vivo biotransformation
rate database for QSAR development and in vitro to in vivo biotransformation
rate extrapolation. The capacity of chemicals to be biotransformed
in fish was found to be highly dependent on the route of exposure.
Somatic biotransformation was the dominant pathway for most chemicals
absorbed via the respiratory route. Intestinal biotransformation was
the dominant metabolic pathway for most chemicals absorbed via the
diet. For substances not biotransformed or transformed exclusively
in the body of the fish, the BCF and BMF appeared to be closely correlated.
For substances subject to intestinal biotransformation, the same correlation
did not apply. We conclude that intestinal biotransformation and bioavailability
in water can modulate the relationship between the BCF and BMF. This
study also supports a fairly simple rule of thumb that may be useful
in the interpretation of dietary bioaccumulation tests; i.e., chemicals
with a BMF<sub>L</sub> of <1 tend to exhibit BCFs based on either
the freely dissolved (BCF<sub>WW,fd</sub>) or the total concentration
(BCF<sub>WW,t</sub>) of the chemical in the water that is less than
5000
Observation of a Novel PFOS-Precursor, the Perfluorooctane Sulfonamido Ethanol-Based Phosphate (SAmPAP) Diester, in Marine Sediments
The environmental occurrence of perfluorooctane sulfonate
(PFOS)
can arise from its direct use as well as from transformation of precursors
((<i>N</i>-alkyl substituted) perfluorooctane sulfonamides;
FOSAMs). Perfluorooctane sulfonamidoethanol-based phosphate (SAmPAP)
esters are among numerous potential PFOS-precursors which have not
been previously detected in the environment and for which little is
known about their stability. Based on their high production volume
during the 1970sā2002 and widespread use in food contact paper
and packaging, SAmPAP esters may be potentially significant sources
of PFOS. Here we report for the first time on the environmental occurrence
of SAmPAP diester in marine sediments from an urbanized marine harbor
in Vancouver, Canada. SAmPAP diester concentrations in sediment (40ā200
pg/g dry weight) were similar to those of PFOS (71ā180 pg/g).
A significant (<i>p</i> < 0.05) correlation was observed
between SAmPAP diester and <i>N</i>-ethyl perfluorooctane
sulfonamido acetate (an anticipated degradation product of SAmPAP
diester). āPFOS-precursor (FOSAM) concentrations in sediment
(120ā1100 pg/g) were 1.6ā24 times greater than those
of PFOS in sediment. Although SAmPAP diester was not detected in water,
PFOS was observed at concentrations up to 710 pg/L. Among the per-
and polyfluoroalkyl substances monitored in the present work, mean
log-transformed sediment/water distribution coefficients ranged from
2.3 to 4.3 and increased with number of CF<sub>2</sub> units and N-alkyl
substitution (in the case of FOSAMs). Overall, these results highlight
the importance of FOSAMs as potentially significant sources of PFOS,
in particular for urban marine environments
Biodegradation of <i>N</i>āEthyl Perfluorooctane Sulfonamido Ethanol (EtFOSE) and EtFOSE-Based Phosphate Diester (SAmPAP Diester) in Marine Sediments
Investigations into the biodegradation potential of perfluorooctane
sulfonate (PFOS)-precursor candidates have focused on low molecular
weight substances (e.g., <i>N</i>-ethyl perfluorooctane
sulfonamido ethanol (EtFOSE)) in wastewater treatment plant sludge.
Few data are available on PFOS-precursor biodegradation in other environmental
compartments, and nothing is known about the stability of high-molecular-weight
perfluorooctane sulfonamide-based substances such as the EtFOSE-based
phosphate diester (SAmPAP diester) in any environmental compartment.
In the present work, the biodegradation potential of SAmPAP diester
and EtFOSE by bacteria in marine sediments was evaluated over 120
days at 4 and 25 Ā°C. At both temperatures, EtFOSE was transformed
to a suite of products, including <i>N</i>-ethyl perfluorooctane
sulfonamidoacetate, perfluorooctane sulfonamidoacetate, <i>N</i>-ethyl perfluorooctane sulfonamide, perfluorooctane sulfonamide,
and perfluorooctane sulfonate. Transformation was significantly more
rapid at 25 Ā°C (<i>t</i><sub>1/2</sub> = 44 Ā±
3.4 days; error represents standard error of the mean (SEM)) compared
to 4 Ā°C (<i>t</i><sub>1/2</sub> = 160 Ā± 17 days),
but much longer than previous biodegradation studies involving EtFOSE
in sludge (<i>t</i><sub>1/2</sub> ā¼0.7ā4.2
days). In contrast, SAmPAP diester was highly recalcitrant to microbial
degradation, with negligible loss and/or associated product formation
observed after 120 days at both temperatures, and an estimated half-life
of >380 days at 25 Ā°C (estimated using the lower bounds 95%
confidence
interval of the slope). We hypothesize that the hydrophobicity of
SAmPAP diester reduces its bioavailability, thus limiting biotransformation
by bacteria in sediments. The lengthy biodegradation half-life of
EtFOSE and recalcitrant nature of SAmPAP diester in part explains
the elevated concentrations of PFOS-precursors observed in urban marine
sediments from Canada, Japan, and the U.S, over a decade after phase-out
of their production and commercial application in these countries
Habitat-Based PCB Environmental Quality Criteria for the Protection of Endangered Killer Whales (<i>Orcinus orca</i>)
The development of an area-based polychlorinated biphenyl
(PCB)
food-web bioaccumulation model enabled a critical evaluation of the
efficacy of sediment quality criteria and prey tissue residue guidelines
in protecting fish-eating resident killer whales of British Columbia
and adjacent waters. Model-predicted and observed PCB concentrations
in resident killer whales and Chinook salmon were in good agreement,
supporting the modelās application for risk assessment and
criteria development. Model application shows that PCB concentrations
in the sediments from the resident killer whaleās Critical
Habitats and entire foraging range leads to PCB concentrations in
most killer whales that exceed PCB toxicity threshold concentrations
reported for marine mammals. Results further indicate that current
PCB sediment quality and prey tissue residue criteria for fish-eating
wildlife are not protective of killer whales and are not appropriate
for assessing risks of PCB-contaminated sediments to high trophic
level biota. We present a novel methodology for deriving sediment
quality criteria and tissue residue guidelines that protect biota
of high trophic levels under various PCB management scenarios. PCB
concentrations in sediments and in prey that are deemed protective
of resident killer whale health are much lower than current criteria
values, underscoring the extreme vulnerability of high trophic level
marine mammals to persistent and bioaccumulative contaminants