Subscriber access provided by University of Sussex Library
Article
Assessing Aromatic Hydrocarbon Toxicity to Fish Early Life Stages Using Passive Dosing Methods and Target Lipid / Chemical Activity Models Josh David Butler, Thomas F. Parkerton, Aaron Redman, Daniel J. Letinski, and Keith R. Cooper Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b01758 • Publication Date (Web): 11 Jul 2016 Downloaded from http://pubs.acs.org on July 12, 2016
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Subscriber access provided by University of Sussex Library
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 32
Environmental Science & Technology
ACS Paragon Plus Environment
Environmental Science & Technology
1
Assessing Aromatic Hydrocarbon Toxicity to Fish Early Life Stages
2
Using Passive Dosing Methods and Target Lipid / Chemical Activity Models
3
Josh D. Butlera*, Thomas F. Parkertonb, Aaron D. Redmana, Daniel J. Letinskia, Keith R. CooperC
4
a
5
1545 US Highway 22 East, Annandale, NJ, USA 08801-3059
6
b
7
800 Bell Street, Houston, Texas, USA 77002
8
C
9
14 College Farm Rd. New Brunswick, NJ, 08901
10
*To whom correspondence may be addressed:
11
ExxonMobil Biomedical Sciences, Inc.; 1545 US Highway 22 East; Annandale, NJ 08801;
12
[email protected]; 980-730-1003
Toxicology & Environmental Sciences Division, ExxonMobil Biomedical Sciences, Inc.
Toxicology & Environmental Sciences Division, ExxonMobil Biomedical Sciences, Inc.,
Environmental Sciences Department, Rutgers University
13 14
ABSTRACT
15 16
Aromatic hydrocarbons (AH) are known to impair fish early life stages (ELS). However, poorly defined
17
exposures often confound ELS test interpretation. Passive dosing (PD) overcomes these challenges by
18
delivering consistent, controlled exposures. The objectives of this study were to: apply PD to obtain 5 d
19
acute embryo lethality and developmental and 30 d chronic embryo-larval survival and growth effects
20
data using zebrafish with different AHs; analyze study and literature toxicity data using target lipid (TLM)
21
and chemical activity (CA) models; extend PD to a mixture and test the assumption of AH additivity. PD
22
maintained targeted exposures over a six order of magnitude range in concentrations. AH toxicity 1 ACS Paragon Plus Environment
Page 2 of 32
Page 3 of 32
Environmental Science & Technology
23
increased with Log Kow up to pyrene (5.2). Pericardial edema was the most sensitive sub-lethal effect
24
that often preceded embryo mortality although some AHs did not produce developmental effects at
25
concentrations causing mortality. Cumulative embryo-larval mortality was more sensitive than larval
26
growth with acute to chronic ratios < 10. More hydrophobic AHs did not exhibit toxicity at aqueous
27
saturation. The relationship and utility of the TLM/CA models for characterizing fish ELS toxicity is
28
discussed. Application of these models indicated concentration addition provided a conservative basis
29
for predicting ELS effects for the mixture investigated.
30 31
INTRODUCTION
32
A key concern with aquatic exposures to aromatic hydrocarbons (AHs) is adverse effects on fish early life
33
stages (ELS). In addition to reductions in embryo survival, AHs as well as crude oils or refined petroleum
34
substances can produce developmental abnormalities including yolk sac and pericardial edemas and
35
cardiovascular, spinal and craniofacial deformities via different mechanisms.1,2,3,4,5 6,7,8,9,10
36 37
A limitation of past ELS studies is the lack of exposure measurements, i.e. tests based on nominal
38
concentrations.1,3,5,7,11,12,13,14 Further, even in toxicity studies where analytical confirmation was
39
performed, rapid declines in AH exposures due to loss processes,15,16 use of co-solvents17 or test
40
concentrations in excess of aqueous solubility18 complicate interpretation and increase uncertainty in
41
hazard assessment. Passive dosing (PD) techniques overcome these challenges by delivering well-
42
controlled, solvent-free exposures in toxicity tests. 19,20,21,22,23,24,25,26 PD methods involve introducing AHs
43
to an inert polymer, e.g. silicone, which is then added to the aqueous media. The loaded polymer then
44
serves as a reservoir to buffer AH losses based on partitioning from the polymer to the test media.
45
Since it is not possible to conduct toxicity studies on all possible AH structures, toxicity data on individual
46
AHs have been used to develop predictive models.27 Once calibrated using reliable empirical data, such
2 ACS Paragon Plus Environment
Environmental Science & Technology
47
models can then be used for effects characterization of untested AHs or AH mixtures while reducing
48
vertebrate testing.28 The target lipid model (TLM) has been used to derive environmental quality
49
objectives in water, soils and sediments for AH substances29,30,31 and has also been applied to assess AH
50
mixture toxicity at historically contaminated sites and oil spills using an additive toxic unit (TU) model.32
51
,33,34
52
risk assessments for petroleum substances.35,36 A second framework for AH effects assessment relies on
53
the use of the chemical activity (CA) concept.37,38 Using CA as an alternative exposure metric, AH toxicity
54
data are expressed in units that have shown to span a narrow range between 0.01 to 0.1.39 A further
55
advantage of this approach is that the toxicity of AH mixtures can also be evaluated by simply summing
56
CA of the components.40,41,42,43
This framework has also been used to predict oil toxicity in lab tests and to perform environmental
57 58
The objectives of this study were to: apply PD to obtain acute and chronic effect data for zebrafish ELS
59
with selected AHs; compare toxicity data on single AHs from this study and literature to TLM and CA
60
frameworks; extend PD to a simple, defined mixture and test the assumption of AH additivity. Zebrafish
61
were selected due to small size, low cost, high fecundity, transparent embryo, which facilitates visual
62
identification of developmental abnormalities, and growing use in standardized testing and
63
research.44,45,46
64
MATERIALS AND METHODS
65
Test Materials
66
Silicone, i.e. polydimethylsiloxane (PDMS), O-rings (0.39g and 1.0g) were obtained from O-rings West
67
(Seattle, WA). Naphthalene, 1-methylnaphthalene, biphenyl, phenanthrene, 1-methylphenanthrene,
68
1,2,3,4,5,6,7,8,-octahydrophenanthrene, bicyclohexyl, pyrene, perhydropyrene, benzo(a)pyrene, pyrene
69
were purchased from suppliers. Perhydrophenanthrene was synthesized internally by catalytic
70
hydrogenation of phenanthrene. Stock AH solutions were prepared in methanol (HPLC grade) obtained
3 ACS Paragon Plus Environment
Page 4 of 32
Page 5 of 32
Environmental Science & Technology
71
from J.T. Baker (Phillipsburg, NJ). An overview of substances used in this study including suppliers,
72
purities and relevant physicochemical properties estimated using SPARC47 are provided in Table S1.
73 74
Test Organisms
75
An outbred strain of zebrafish genotyped by Charles River Laboratories International, Inc. (Wilmington,
76
MA) and obtained from Aquatic Research Organisms (Hampton, NH) was used in this study
77
(documentation available upon request). Embryos were obtained from a breeding culture previously
78
described.21 Spawning and fertilization occurred within 30 minutes after the onset of light. Eggs were
79
collected and immediately rinsed with water, transferred to a crystallization dish and examined for
80
viability before use in toxicity testing.
81 82
Determination of Partition Coefficients
83
Passive dosing was used to generate and maintain test substance aqueous concentrations. In order to
84
accurately calculate predicted final water concentrations experimentally derived partition coefficients
85
for ten compounds (Table S1 and S2) were determined by loading three separate 20 mL glass vials, each
86
with four 0.39 g O-rings, with 10 mL of a known AH concentration in methanol. After a 72 h equilibration
87
on a vial roller at 28℃, the methanol solution was poured off and an aliquot was diluted 1:20 with
88
acetone and analyzed. Two O-rings from each vial were extracted four times each with 10 mL of acetone
89
on a wrist-action shaker for one hour. An aliquot of each extract was then analyzed. The remaining two
90
O-rings were rinsed with glass distilled water and wiped dry with lint-free tissue paper and then added
91
to a 20 mL glass vial containing reconstituted water (see below) on an orbital shaker at 400 rpm for 24
92
hours at 28℃. Partition coefficients between methanol and PDMS (KMeOH:PDMS) and between PDMS and
93
water (KPDMS:Water) were calculated based on analysis of test substance concentrations in each phase.
94
Toxicity Test Dosing
4 ACS Paragon Plus Environment
Environmental Science & Technology
95
O-rings served as the PD source for embryo/larval exposures. Methods detailed by Butler et al., 21 were
96
employed to load test substances from the methanol/AH solution into O-rings and subsequently dose
97
the aqueous phase. Methanol alone was equilibrated with O-rings used in the control replicates.
98
Nominal concentrations of each compound were predicted by dividing methanol concentrations by the
99
AH specific methanol-water partition coefficient ( see results section). Predicted concentrations were
100
then compared to measured concentrations to assess accuracy and maintenance of targeted exposures.
101
Test systems were designed to ensure that the mass of chemical absorbed into the O-rings was
102
sufficient to prevent significant depletion following subsequent dosing of aqueous test media
103
(Supplemental Information, Appendix A).
104 105
Acute toxicity tests
106
Embryos were exposed individually to naphthalene, 1-methylnaphthalene, biphenyl, phenanthrene,
107
pyrene, 1,2,3,4,5,6,7,8-octahydrophenanthrene, benzo(a)pyrene, and chrysene. Each test consisted of 5
108
concentrations and a control, except for benzo(a)pyrene and chrysene which were investigated only at
109
the respective solubility limits. Embryos were exposed in 20 mL headspace vials with a 0.39 g O-ring
110
resting on the bottom. Vials were then capped with Teflon coated screw caps and placed into an
111
environmental chamber at 28±1°C. Twenty replicates with one embryo per vial comprised each
112
treatment. In vial microscopic observations were performed at 24-h intervals. Lethal (coagulation, lack
113
of heartbeat) and sub-lethal (pericardial and yolk sac edemas and tail curvature) endpoints included
114
those defined in the OECD (2006) FET draft guideline up to 5 days post fertilization (dpf).48 The
115
photoperiod was set to a 12:12 light/dark cycle with a light intensity of 250 lux. Test media for the acute
116
tests was prepared using Instant Ocean® sea salt, 60 µg/mL stock salts. 49 Water quality parameters
117
(dissolved oxygen, temperature, conductivity, pH) were monitored and maintained within test
118
guidelines requirements. For all acute toxicity tests the dissolved oxygen was ≥80%, pH ranged from 7.2-
5 ACS Paragon Plus Environment
Page 6 of 32
Page 7 of 32
Environmental Science & Technology
119
7.6, Conductivity was 130-150 µS/cm and temperature ranged from 25.8-26.4℃. Duplicate samples for
120
analytical confirmation of AH exposures were taken for each treatment at test start and termination.
121 122
Chronic Individual Compound and Mixture Toxicity Tests
123
Embryo/larvae were exposed for 30 d to five AHs individually (1-methylnaphthalene, phenanthrene, 1,
124
2, 3, 4, 5, 6, 7, 8-octahydrophenanthrene, chrysene, benzo(a)pyrene). Tests with the first three
125
substances consisted of 3 concentrations and a control while the remaining two substances were
126
performed as limit tests at test media saturation. A separate test was performed using a mixture of 7
127
AHs and 3 hydrogenated analogs (Table S1) with three treatment concentrations and a control. Half of
128
the compounds included in the mixture test were included in single compound experiments while the
129
remainder of the test compounds were not tested individually. These exposures, therefore, represent a
130
test of the predictive toxicity model derived from single compound tests for estimating the contribution
131
of untested components to the resulting mixture toxicity (see Data Analysis section). Moderately hard
132
reconstituted water was used as the test media from day 5 through 30 of each chronic test.50 Water
133
quality parameters (dissolved oxygen, temperature, conductivity, pH) were monitored and maintained
134
within test guidelines requirements. For all chronic toxicity tests the dissolved oxygen was ≥80%, pH
135
ranged from 7.4-7.8, Conductivity was 320-375 µS/cm and temperature ranged from 25.1-26.1℃.
136 137
Embryos were initially exposed in vials for 5 d as described for acute experiments. Upon 5 days post
138
fertilization (dpf), embryos that hatched into larval fish as well as any unhatched embryos exposed in
139
vials were transferred into four replicate 300 mL flow-through chambers, described previously by Butler
140
et al.21 and depicted in Figure S1 each with up to 5 fish per chamber (i.e. fewer larvae were used in
141
treatments with earlier embryo mortality). Four-liter mixing vessels containing 30 loaded O-rings (1.3
142
each), were prepared for passively dosing each treatment. Each individual flow-through chamber was
6 ACS Paragon Plus Environment
Environmental Science & Technology
143
also supplemented with three, 1.3g loaded O-rings to buffer potential losses in this recirculating system.
144
The test media flow (5 mL/min) through each chamber was supplied by a peristaltic pump. Mixing
145
vessels were supersaturated with oxygen to > 20 mg/L for ensuring adequate oxygen concentrations
146
during exposures and exchanged every 5-7 d with a new set of loaded O-rings to avoid biofouling and O-
147
ring depletion. Upon transfer to flow through chambers, fish were fed Paramecium
148
multimicronucleatumn.51 Starting at 12 dpf the diet was supplemented with Artemia nauplii. Larvae
149
were fed ad libitum, twice daily throughout the test. The photoperiod was set to a 12:12 light/dark cycle
150
with a light intensity of 250 lux.
151 152
For each chronic test, aqueous samples were collected for AH analysis from each treatment and control
153
at test start and on day 5 prior to the addition of larval fish to the flow through chamber. While larval
154
fish were held in flow-through chambers, subsequent water samples were taken for AH analysis from
155
each new and corresponding old mixing vessel at least once every 5-7 d. Chronic test endpoints for the
156
first 5 days included those described for the acute test. Beginning on day 6, hatched larvae were
157
observed daily for immobility, lack of respiratory movement and reaction to mechanical stimulus per the
158
OECD guideline.52 To evaluate potential larval growth effects, total lengths of surviving larvae were
159
measured at test termination.
160 161
Test Substance Analysis for Exposure Confirmation
162
Two, 40 mL glass vials were collected at each sampling point for quantifying AH exposures. Analysis for
163
naphthalene, biphenyl, phenanthrene and 1-methylnaphthalene in water was performed using static
164
headspace gas chromatography with flame ionization detection (HS-GC-FID) using a Perkin Elmer
165
Autosystem XL gas chromatograph. Analysis of octahydrophenanthrene was performed by HS-GC-FID
166
modified with a trap accessory to provide additional sensitivity. Pyrene, benzo(a)pyrene, chrysene and
7 ACS Paragon Plus Environment
Page 8 of 32
Page 9 of 32
Environmental Science & Technology
167
all mixture components were analyzed by automated direct immersion (DI) solid phase microextraction
168
(SPME) coupled with gas chromatography with mass selective detection (GC-MSD).
169
Water samples were collected in duplicate in glass volatile organic analysis (VOA) vials at each sampling
170
point to quantify AH exposure concentrations. Aliquots were transferred to ca 20 mL glass, septum
171
sealed vials for either headspace or direct immersion SPME along with the internal standard.
172 173
The HS-GC-FID was equipped with a 30 mm x 0.53 mm id, 1.5 µm film DB-5 analytical column (J&W
174
Scientific) which was connected directly to the transfer line of a Perkin-Elmer TurboMatrix 40 Trap
175
Headspace Sampler. For octahydrophenanthrene analysis, a sorbent trap containing fused silica beads
176
and Carbopack C was placed in-line of the headspace sampler. All water samples for headspace analysis
177
and standards spiked into water were equilibrated for 45 m at 90°C. The needle and transfer line
178
temperatures were both 175°C, the pressurization time was 3 m. The injector temperature was 50°C and
179
column pressure was 28 psi. The FID was 275°C and the oven temperature was held at 40°C for 1 m and
180
then ramped up to 275°C at 20°C/minute. Data were acquired and processed using Perkin Elmer
181
TotalChrom Workstation software.
182 183
A DI-SPME autosampler was coupled with an Agilent 6890N gas chromatograph and Agilent 5975 mass
184
selective detector operated in the selective ion monitoring mode (SIM). The analytical column was a 25
185
m x 0.2 mm id, 0.33 µm DB-5MS (J&W Scientific) capillary column. The GC-MSD system was equipped
186
with a Gerstel CIS 4 inlet and interfaced with a Gerstel MPS 2 autosampler operated in the DI-SPME
187
mode using a 7-µm PDMS fiber (Supelco) with a 90-minute extraction time at 30oC. The SPME fiber was
188
automatically desorbed for 5 minutes at 300oC. The GC oven temperature was programmed from 50oC
189
for 5 mto 340oC at 12oC/minute. After an initial 25 psi pressure pulse for one minute, the helium carrier
190
gas pressure was set at 13.8 psi corresponding to a constant flow of approximately 0.8 mL/m for the
8 ACS Paragon Plus Environment
Environmental Science & Technology
Page 10 of 32
191
duration of the run. Standards analysis for both methods resulted in a linear response over
192
concentration ranges bracketing the respective water concentrations.
193 194
TLM and CA Model Frameworks
195
The TLM describes the LC50 of a nonionic chemical using the relationship:
LC50 =
196
(1)
197
where:
198
LC50= lethal (or effective) concentration in water causing 50% response (mmol/ Lwater)
199
CTLBB = critical target lipid body burden corresponding to the acute effect (mmol/kglipid)
200
KTLW = target lipid water partition coefficient (kg lipid/ Lwater)
201
A linear free energy relationship is used to estimate the target lipid water partition coefficient from the
202
octanol-water partition coefficient. Following rearrangement of equation (1) and substitution of the
203
correlation between KTLW and Kow,, LC50 is expressed as:
204
Log LC50 = log (CTLBB) - 0.94 Log Kow + Δc
(2)
205
The TLM indicates that toxicity depends on both the sensitivity of the species, as defined by the CTLBB,
206
and the partitioning properties of the test substance. The Δc term is a correction that accounts for
207
partitioning differences not accounted for by Kow and has been empirically derived for various functional
208
groups by fitting equation (2) to toxicity data for a large array of chemicals. In the case of mono and
209
poly AHs, Δc = -0.109 and -0.352, respectively. 29
9 ACS Paragon Plus Environment
Page 11 of 32
Environmental Science & Technology
210
In the chemical activity (CA) framework, toxicity is defined as a fractional solubility of the test substance
211
relative to the reference liquid state:37
LA50 =
212
(3)
213
where:
214
LA50= lethal (or effective) activity in water causing 50% response (unitless)
215
SL = aqueous solubility of the sub-cooled liquid (mmol/Lwater)
216
For hydrocarbons, SL can also be estimated from Kow.53
217
Log SL =3.54 - 1.10 Log Kow
(4)
218
Substituting this relationship into (3) and solving for LA50 yields:
219
Log LC50 = Log (LA50) + 3.54 - 1.10 Log Kow
(5)
220
Equating (2) and (5) shows the predicted relationship between the TLM and CA frameworks:
221
Log LA50 = Log (CTLBB) + 0.16 Log Kow - 3.54 + Δc
(6)
222
Thus, LA50 depends on the species and endpoint-specific CTLBB and is predicted to be positively
223
correlated to substance Log Kow as modulated by chemical class-specific correction factors that account
224
for substance partitioning to target lipid.
225 226
Data Analysis
227
Acute (5-d LC50) and chronic (30 d EC10) effect concentrations were calculated by probit analysis using
228
SAS
229
determine significant differences from the control. The logistic equation was used was used to fit dose-
54 55
. The T-test with Bonferroni adjustment56or Fisher’s Exact Test 57 58using TOXSTAT 59software to
10 ACS Paragon Plus Environment
Environmental Science & Technology
230
response zebrafish mortality data using a least squares regression method included in the GraphPad
231
Prism 5.0 software.60
232 233
Empirical LC50 data were adjusted based on the TLM prescribed class corrections (e.g., logLC50 - Δc, by
234
re-arranging Eqn. 2) and then fit by linear regression using equation (2) to derive the CTLBB that
235
characterizes the acute sensitivity of zebrafish embryos29. This relationship was further extended to
236
predict chronic toxicity by subtracting the empirically derived mean log of the Acute to Chronic Ration
237
(ACR). For the mixture test, exposure concentrations for each substance were converted into Toxic
238
Units (TUs) by dividing the targeted exposure concentration of each component by the TLM-derived
239
acute or chronic effect concentration. Summed TUs (∑TUs) were then compared with observed effects
240
to assess concordance with concentration addition. Test concentrations were selected so that each
241
compound contributed about equally to TUs and three treatment levels plus a control were selected to
242
provide ∑TUs bracketing unity which corresponds to treatment levels above and below the appropriate
243
effect level (LC50 for acute and LC10 for chronic). The ∑CA was used as an alternate exposure metric for
244
evaluating mixture toxicity by dividing exposures for individual mixture components by the
245
corresponding sub-cooled liquid aqueous solubility (Table S1) and then summing the CA of all mixture
246
components.
247 248
RESULTS & DISCUSSION
249
Partition Coefficients
250
Measured AH partition coefficients are summarized in Table S2. Log KMeOH:PDMS ranged between -0.070 to
251
1.41 while Log KPDMS:water varied from 2.98 to 5.16. Experimental KMeOH:Water values were found to
252
correlate to the octanol-water partition coefficient:
253
11 ACS Paragon Plus Environment
Page 12 of 32
Page 13 of 32
254
Environmental Science & Technology
K : = 0.825 × K + 0.390 r2 = 0.96, n=10
(7)
255 256
This relationship is consistent with KMeOH:Water values reported by Smith et al. 61 (Figure S2). Equation (7)
257
was used to estimate KMeOH:Water for the remaining AHs for which measured partition coefficients were
258
not determined.
259 260
Analytical confirmation of test concentrations
261
To evaluate the ability of PD to deliver and maintain exposure concentrations, predicted nominal
262
concentrations were compared to analytically determined concentrations in test media. Results
263
indicated excellent agreement between targeted and measured concentrations across test compounds
264
that span a wide range of physicochemical properties and exposure treatments spanning over six orders
265
of magnitude (0.1 to 19,436 µg/L) (Figure S3; Table S3). These results indicate that the equilibration
266
periods selected for dosing o-rings and water were sufficient to achieve equilibrium. The mean ratio of
267
predicted to observed concentrations across all tests was 1.29±0.66; n=70 (Table S3). PD maintained
268
exposures with a mean percent difference in measured concentrations of 9±6% between the start and
269
end of 5 d embryo tests (Table S4). Figure 1 further illustrates the fidelity of exposures over 30 d chronic
270
tests (Figure 1, A-D).
271 272
Acute Exposures
273
No control mortality was observed in any test. Most test substances showed statistically significant sub-
274
lethal developmental effects on embryos. Pericardial edema was the most sensitive developmental
275
effect noted and often preceded mortality, but this was not always the case as several AHs did not
276
exhibit developmental effects at exposure concentrations causing mortality (Table S5). 5-d LC50s are
277
reported in Table 1 and concentration-responses for embryo mortality are shown in Figure S4. Where 12 ACS Paragon Plus Environment
Environmental Science & Technology
278
sufficient concentration-responses were observed, EC50s for sub-lethal effects were also calculated
279
(Table S6). However, reliable estimates were in some cases not possible due to reduced sample sizes
280
from embryo mortalities during test exposures. With the exception of biphenyl and naphthalene, where
281
the most sensitive 2 d developmental effect EC50 values were two or three fold lower than the 5 d LC50,
282
respectively. EC50s were similar to LC50 estimates (phenanthrene and pyrene) or higher for the
283
remaining compounds (Table 1).
284 285
The 5 d LC50 for zebrafish recently reported using PD for phenanthrene by Vergauwen24 of 310 µg/L is in
286
close agreement with the value of 334 µg/L obtained in this study. These authors also report that after
287
5 d exposure to phenanthrene at 362 µg/L 100 and 70% of surviving embryos exhibited tail curvature or
288
pericardial or yolk sac edemas, respectively, which seems consistent with the 2 d EC50 of 415 µg/L for
289
these endpoints reported in Table 1. A range of other sublethal effects were also investigated in this
290
study and swim bladder inflation was reported to be the most sensitive endpoint with a 5 d EC50 of 59
291
µg/L. These authors noted this is a common sub-lethal effect observed for many substances in different
292
classes and varying modes of action. This endpoint, which may reflect either a delay or lack of swim
293
bladder inflation, was not evaluated in the present study. Direct comparison of developmental fish
294
embryo abnormalities observed in this work to other literature is difficult given the uncertainty in
295
exposure concentrations, varying exposure durations, alternative fish species and different sub-lethal
296
endpoints investigated in earlier studies.
297
In contrast, these authors report sub-lethal effects on swim bladder and other morphological effects on
298
developing embryos at six-fold lower exposure concentrations than we observed. These results suggest
299
the potential differences in inter-lab reproducibility of lethal versus sub-lethal embryo endpoints even
300
when PD methods are used.
301
13 ACS Paragon Plus Environment
Page 14 of 32
Page 15 of 32
Environmental Science & Technology
302
No acute or sub-lethal effects were noted at the highest, single limit concentration tested for chrysene
303
and benzo(a)pyrene (Table 1, Table S5). The lack of acute effects reported for these two substances is
304
consistent with the findings of Seiler et al. (2014)22 who also showed zebrafish embryo mortality during
305
2 d tests was not significantly different from controls at the highest concentration attainable using a PD
306
test design. Further, pyrene was the most hydrophobic AH compound tested by Seiler that caused
307
embryo mortality consistent with the findings of this study (Table 1).
308 309
The 2 - 5 d LC50s (Table S7, Table 1) were fit to the TLM using equation (2) in order to derive CTLBB
310
estimates. The CTLBBs for zebrafish were estimated to be 158 ± 6 and 81 ± 10 µmol/g octanol,
311
respectively. These values fall within the range of 24 to 500 µmol/g octanol reported previously for
312
different test species and acute endpoints.29 Additional acute zebrafish toxicity data for AHs and other
313
nonpolar organic chemicals including aliphatic hydrocarbons and alcohols, halogenated solvents, and
314
oxygen and sulfur containing AHs were compiled from the literature (Table S7). Data for 2-5 d test
315
exposures are plotted separately in Figure 2A and B along with the TLM model derived from our study
316
data. Literature data based on conventional dosing techniques (i.e. semi-static, static, flow through test
317
substance renewals, etc.) include both nominal (unfilled) and measured (filled symbols) exposures.
318
Tests showing no acute effects at the highest exposure concentration investigated are shown as a plus
319
symbol. The relationship between sub-cooled solubility and Log Kow described earlier, are used to
320
generate the dashed lines corresponding to CAs of 0.01, 0.1 and 1.0 on these figures.
321 322
Figure 2 indicates acute LC50s, adjusted using the relevant TLM class correction factor to express results
323
in terms of baseline toxicity, for water soluble substances with Log Kow < 3 fall within approximately a
324
factor of three above or below the TLM prediction with LA50s generally within the 0.01 to 1.0 range.
325
However, as the Log Kow increases, available literature data shows more scatter that likely reflects the 14 ACS Paragon Plus Environment
Environmental Science & Technology
326
greater uncertainty in the actual exposure concentrations associated with conventional dosing methods
327
of sparingly soluble and sometimes volatile test substances. In fact, some tests indicate LA50s that are
328
above the theoretical limit of unity thus questioning test reliability. In a recent study that investigated
329
algal toxicity to fifty organic chemicals ranging in Log Kow from 1 to 5 and expected to act via baseline
330
toxicity, LA50s fell within a similar range of 0.1 to 1.0 and increased with Log Kow consistent with the
331
zebrafish data in this study (Figure 2) and predictions from equation (6).62
332 333
Further comparison of acute zebrafish toxicity data included in Table S7 for nitrogen containing AHs to
334
the TLM frameworks indicates toxicity is systematically underestimated by an order of magnitude
335
(Figure S5). Previous work on benthic invertebrates has shown that nitrogen containing heterocyclic AHs
336
can exhibit greater toxicity than the corresponding homocyclic AHs.63 However, if the correction term in
337
equation 1 is adjusted to account for differential partitioning of this compound class to target lipid,
338
revised TLM predictions are in good agreement with empirical data (Figure S5). This provides an
339
example of how interrogating toxicity data sets using the TLM framework can lead to improved models
340
for toxicity prediction.
341 342
Chronic Exposures and ACRs
343
Less than 10 percent control mortality was observed in all chronic exposures. Cumulative embryo larval
344
mortality over 30 days was used to estimate LC10 values (Table 1). Mortality showed a similar temporal
345
trend across substances. Once fish matured past the elutheroembryo developmental stage (days 5-7)
346
most fish survived (Figure S6). Further, based on measured lengths of surviving larvae at test
347
termination, no effects on larval growth were observed for 1-methylnaphthalene and
348
octahydrophenanthrene. For phenanthrene, while a statistically significant 12 % reduction in growth
349
was observed at 105 µg/L, cumulative embryo larval survival was a more sensitive endpoint than larval
15 ACS Paragon Plus Environment
Page 16 of 32
Page 17 of 32
Environmental Science & Technology
350
growth. The acute sub-lethal embryo developmental endpoints evaluated in this study appeared less
351
sensitive than the chronic test endpoints (Table 1). Consistent with acute toxicity results, chronic values
352
decreased with increasing logKOW (Table 1). The ACRs calculated from these tests (5.8 to 7.6) fall within
353
the range of values (1 to 13) reported previously for AHs with other test species29 as well as data
354
compiled for a broader class of nonpolar organic chemicals (median ACR=4.4; range 1-30, n= 19).64 No
355
chronic effects were observed for chrysene and benzo(a)pyrene at mean measured exposure
356
concentrations of 1.4 and 1.7 μg/L, which appears to be the limit of saturation in this test system. These
357
exposures are close to the reported aqueous solubilities of 1.6 and 1.5 μg/L, respectively.65
358 359
To gain further insights on the chronic effects of AHs to fish ELS, three data sets generated from testing
360
multiple AH compounds were compiled from the literature (Table S8). Literature chronic values are
361
plotted for comparison with our study data (red symbols) in Figure 3. Unfilled symbols denote test data
362
where chronic effects were not observed at the maximum exposure concentration tested. The chronic
363
TLM line was derived from the relationship from our acute data after dividing by the mean acute to
364
chronic ratio of 6.9 (Table 1). This is equivalent to assuming a CTLBB for chronic effects by application of
365
the median ACR determined in the present study of 81/6.9 = 12 µmol/g octanol. To facilitate comparison
366
of effects data in terms of CA, dashed lines ranging 0.001 to 0.1 are also shown.
367 368
The first data set was obtained from a recent review summarizing unpublished chronic zebrafish ELS
369
tests performed using static renewals with conventional dosing methods. 66 Like our chronic tests, both
370
survival and growth endpoints were investigated. While results were expressed in terms of mean
371
measured exposure concentrations, significant declines in exposure were noted thereby introducing
372
uncertainty in the chronic values reported. Results from this study are shown as gray symbols in Figure
373
3 and decrease with increasing Log Kow consistent with TLM predictions until 5.5, above which, three of
16 ACS Paragon Plus Environment
Environmental Science & Technology
374
the four AHs exhibit no chronic effects based on either endpoint. Both chrysene and benzo(a)pyrene
375
that were evaluated in this study was not chronically toxic in 42 d tests at mean concentrations of 0.9
376
and 4 μg/L, respectively, in support of our study findings. In contrast, benzo(k)fluoranthene was
377
reported to cause chronic effects on growth and survival at mean concentrations of 0.62 and 0.17 μg/L,
378
respectively (Table S8). Further, for all AHs that exhibited chronic effects, larval growth appeared more
379
sensitive in these studies than survival in contrast to our findings (cf. squares and diamonds in Figure 3).
Page 18 of 32
380 381
Two recent studies have also investigated ELS toxicity to a different fish species (Japanese medaka) using
382
PD for a range of parent and alkylated AHs.20,27 Previous work has shown that the acute CTLBB for this
383
species is 127 ± 57 µmol/g octanol suggesting similar sensitivity to zebrafish.29 Given the limited use of
384
PD to characterize ELS toxicity with AHs, we have compared results from these studies to zebrafish data
385
derived in this study. In both studies, toxicity was expressed in terms of a 17 d EC50 that incorporated
386
several embryo pathology endpoints that were scored to provide an effect index. In the first study
387
phenanthrene and corresponding methyl, ethyl and dimethyl homologs were tested. All test
388
compounds were found to produce EC50s at concentrations below aqueous solubility limits. In the
389
second study, chrysene and benz(a)anthracene and six alkylated homologs were investigated. All
390
compounds, except chrysene, were found to produce sub-lethal effects on embryos at the solubility
391
limit including benzo(a)pyrene (Table S8, Figure 3) but only retene (i.e. 1-methyl-7-
392
isopropylphenanthrene ), which served as the positive control, benzo(a)anthracene and 7-methyl
393
benzoanthracene yielded sufficient concentration responses below the solubility limit to allow EC50s to
394
be calculated. Further, none of these compounds, except the positive control, reduced embryo-larval
395
survival after 17 d to exposures corresponding to the solubility limit. Other studies have reported similar
396
findings. For example, no significant differences in either survival or hatching success from the control
17 ACS Paragon Plus Environment
Page 19 of 32
Environmental Science & Technology
397
were reported for rainbow trout eggs exposed 36 d post-fertilization to measured concentrations of
398
benzo(a)pyrene up to 3 μg/L although developmental effects were noted.67
399 400
EC50s for medaka embryo pathology also decrease with increasing log Kow. The zebrafish chronic TLM
401
prediction is shown to be protective (i.e. data points fall above model line) for this endpoint (Figure 3).
402
Further, chronic effects generally corresponded to CA > 0.01. In a number of tests, chronic effects were
403
not observed at CA > 0.1. This suggests that lack of chronic effects cannot only be attributed to an
404
insufficient chemical activity resulting from solubility constraints. One alternative explanation is that
405
toxicokinetics may limit internal residues and preclude potential toxicity of AHs.9 While this may help
406
explain a lack of effects observed in short term exposures, this hypothesis seems less plausible for
407
chronic exposures where equilibrium with tissues would be achieved. A second explanation to account
408
for no chronic effects at elevated CA is biotransformation processes may limit exposure of higher log Kow
409
AHs or related metabolites in embryo-larvae tissues to concentrations that do not invoke chronic
410
effects. Biotransformation rates in fish have been shown to increase with AH hydrophobicity.68,69
411
Further, biotransformation processes may also help explain why certain hydrophobic AHs exhibit chronic
412
toxicity at much lower CAs. For certain AHs, specific metabolites may be produced that enhance chronic
413
effects. Recent bioconcentration studies of benzo(a)anthracene with zebrafish embryos have
414
documented formation of a polar metabolite that might help explain the high chronic toxicity reported
415
(Table S8)70 However, uncertainties in exposure concentrations in available ELS toxicity studies with
416
benzo(a)anthracene warrant further research to determine if previously reported chronic values can in
417
fact be replicated using controlled exposures with PD methods.
418 419
Further investigation is also needed to assess the chronic effects of 4+ ring AHs on reproductive
420
endpoints. In one study, 71 no effects on zebrafish survival was reported after a 56 d exposure to
18 ACS Paragon Plus Environment
Environmental Science & Technology
421
benzo(a)pyrene at two treatment levels with mean reported concentrations of 1.63±0.32 and 3.35±0.91
422
µg/L consistent with other studies (Table S8) . However, a statistically significant 50% reduction in egg
423
production was observed after 49 d in both treatments. Altered transcription of genes important in
424
regulating reproduction was also demonstrated and hypothesized as an underlying mechanism of
425
benzo(a)pyrene reproductive toxicity.
426 427
Mixture Exposures
428 429
The effects on zebrafish ELS are summarized in Table 2. Cumulative embryo-larval mortality exhibited
430
same trend over time as individual compound tests (Figure S6). Measured exposure concentrations
431
(Table S9A) were translated into both ∑ TUs (Table S9B) and ∑ CA (Table S9C) as alternative exposure
432
metrics. Sub-lethal embryo effects were observed after 5 days in the lowest treatment group
433
corresponding to 0.1 acute ∑TUs. However, statistically significant effects on survival after 5 d were only
434
observed at the highest treatment in which a 30% embryo mortality corresponded to an acute ∑TU = 1.2
435
(Table 2). This observed mortality is less than predicted based on concentration addition of mixture
436
components (i.e. 50% response predicted at ∑TU = 1) but within typical variability noted previously
437
based on application of the additive model (~2-fold).29
438 439
This treatment corresponds to an estimated 5 d EA30 of 0.319. However, if the CA contribution of the
440
two non-aromatic hydrocarbons (perhydrophenanthrene and perhydropyrene) which have estimated
441
log Kow’s of 6.76 and 7.54 are ignored, the 5 d EA30 is reduced to 0.033. This estimate is similar to the PD
442
test results of Seiler22 who derived a 2 d LA50s of 0.059 to 0.087 by comparing observed zebrafish
443
mortality at the maximum chemical activity achievable for different AHs.22 These results suggest that
444
these compounds do not contribute to acute ELS effects at CA of 0.09 and 0.18, respectively (Table S9C).
19 ACS Paragon Plus Environment
Page 20 of 32
Page 21 of 32
Environmental Science & Technology
445 446
Cumulative mortality was the most sensitive endpoint when exposures were extended 30 d to include
447
the larval stage. Although fish length was quantified at test termination no effects on growth were
448
observed (Table 2). If the mixture components are additive, a chronic ∑ TU = 1 should correspond to 10%
449
mortality since the LC10 served as the chronic effect endpoint. Adjusting for control performance, 0 and
450
25% mortality was observed at chronic ∑ TU of 0.54 and 3.76, respecƟvely which brackets the expected
451
value of unity (Table 2). Assuming, the mixture components contribute additively to toxicity, the TLM
452
appears to provide a reasonable basis for estimating the chronic effects of the mixture investigated.
453
If the mixture test is expressed in terms of ∑ CA, the LA10 would fall within the range of 0.016 to 0.171
454
(Table 2) which corresponds to CAs associated with chronic effects for individual AHs (c.f. Figure 3).
455
Unlike acute tests, these results suggest that the two more hydrophobic non-aromatic test substances
456
contributed to observed chronic effects. The relative contribution of these two components to chronic
457
∑ TUs and ∑ CA at the low and mid dose treatments ranged from 56-79% and 86-95%, respectively Table
458
S9).
459 460
This analysis highlights the comparative use ∑ TU and ∑ CA as exposure metrics for interpreting mixture
461
toxicity studies. The use of ∑ TU provides the advantage of allowing differences in species and endpoint
462
sensitivity to be explicitly taken into account. Further, since expression of toxicity results in terms of CA
463
even for a given test organism and endpoint is not chemical independent, the use of ∑ TU is
464
hypothesized to provide a more precise exposure parameter for predicting toxicity across mixtures with
465
different compositions.
466 467
This study also demonstrates the utility of PD in maintaining constant exposures that allow reliable
468
chronic fish ELS effects data to be developed for individual AHs and related mixtures. While we
20 ACS Paragon Plus Environment
Environmental Science & Technology
469
investigated several sub-lethal embryo developmental effects that were included in a draft test
470
protocol, these endpoints are not included in the final OCED test guideline.72 Future research is
471
therefore needed to better understand the inter-laboratory precision of various sub-lethal embryo
472
endpoints including impairment of swim bladder inflation and the relationship of these effects to
473
chronic effects on survival, growth and reproduction which serve as the key endpoints used in chemicals
474
management73. This work also describes the linkage between TLM and CA models and illustrates how
475
both frameworks can be practically applied to characterize the acute and chronic toxicity of individual
476
substances and mixtures. Additional effort is needed to objectively compare the relative performance
477
of ∑ TU and ∑ CA as exposure metrics for predicƟng AH mixture toxicity.
21 ACS Paragon Plus Environment
Page 22 of 32
Page 23 of 32
478
Environmental Science & Technology
Table 1. Summary of zebrafish embryo-larval acute, sub-lethal and chronic toxicity endpoints.
Test Substance
2 to 4 d EC50 embryo development
(µg/L)1
488 489 490
Slope 2 Parameter
30-d LC10 embryo-larval survival
30-d EC10 larval growth
(µg/L)
(µg/L)
(µg/L)
Acute to Chronic 3 Ratio
6309 2.73 NT NT CNC (5888-6760) 1013 141 (1361-methylnaphthalene >1716 1.88 >277 7.2 (1182-1703) 144) 973 1548 biphenyl 2.04 NT NT CNC (971-976) (1148-2290) 415 334 phenanthrene 1.57 44 (22-65) 88 7.6 (CNC) (184-1493) 1,2,3,4,5,6,7,8 52 >682 0.76 9 (CNC-13) >88 5.8 octahydrophenanthrene (39-80) 91 96 pyrene 3.16 NT NT CNC (34-147) (87-102) chrysene >1.4 >1.4 N/A >1.4 >1.4 N/A benzo(a)pyrene >1.7 >1.7 N/A >1.7 >1.7 N/A Values in parenthesis indicate confidence intervals NT= not tested; N/A = not applicable as no effects observed at maximum concentration tested; CNC =could not calculate since chronic testing not performed 1 slope parameter of logistic equation that define lines plotted in Figure S4 2 acute to chronic ratio calculated as 5 d LC50 / lowest 30 d chronic value naphthalene
479 480 481 482 483 484 485 486 487
5-d LC50 embryo mortality
2343 (2372-2358)
Table 2. Acute and chronic effects observed during 30-days exposure to a defined mixture of aromatic and saturated cyclic hydrocarbons. Acute Exposure 5 d Embryo Acute Effects Chronic Exposure 30 d ELS Chronic Effects Toxic Chemical PE TC Mortality Toxic Chemical Mortality Length ± SD (cm) Units Activity (%) (%) (%) Units Activity (%) 0 0 0 0 0 0 0 5 1.57 ± 0.22 0.10 0.015 0 26* 0 0.47 0.016 5 1.59 ± 0.12 0.46 0.151 26* 35* 5 3.76 0.171 30* 1.46 ± 0.10 1.21 0.309 35* 7 30* 10.52 0.374 90* 1.75 ± 0.35 *Statistically significant (p=0.05) PE=pericardial edema; TC= tail curvature; for embryo developmental endpoints the percentage refers to the proportion of the test population affected that were alive
22 ACS Paragon Plus Environment
Environmental Science & Technology
A
Page 24 of 32
B
1-Methylnaphthalene
Phenanthrene 1000
Cmeasured (ug/L)
1000
100
100
60 ug/L
277 ug/L
105 ug/L
32 ug/L
1227 ug/L
423 ug/L
10 0
10
20
30
0
10
20
C
D
1,2,3,4,5,6,7,8-Octahydrophenanthrene
Chrysene & Benzo(a)Pyrene
30
10
Cmeasured (ug/L)
100
1 10
25 ug/L
5 ug/L
1.4 ug/L Chrysene
88 ug/L
1
1.7 ug/L BaP
0.1 0
10
20
30
0
Time (days)
10
20
30
Time (days)
491 492 493 494 495 496
Figure 1. Measured aqueous concentrations in chronic tests. Each symbol represents the mean of two replicates plus the standard deviation (often not visible due to low variability). Solid lines denote predicted nominal concentrations. Concentrations reported for each compound at the bottom of plot is the 30 day mean value. Analysis of the high treatment level in 1-methylnaphthalene and phenanthrene tests (Figure 1, A and B) was terminated before 30 d due to complete mortality.
497
23 ACS Paragon Plus Environment
Page 25 of 32
Environmental Science & Technology
498
(b)
499 500 501 502 503 504 505 506 507 508
Figure 2. Zebrafish LC50s as a function of substance Log Kow. Empirical data are adjusted using reported class-specific correction factors (e.g., logLC50 - Δc, by re-arranging Eqn 2) to allow direct comparison to the target lipid model shown as the solid line; dashed lines indicate approximate chemical activities corresponding to 0.01, 0.1 and 1.0 from bottom to top respectively; Literature data based on conventional dosing techniques (i.e. semi-static, static, flow through test substance renewals, etc.) include both nominal (unfilled) and measured (filled symbols) exposures. Data from this study are represented as filled red squares. Data points denoted as “+” indicate no acute toxicity was observed at the maximum concentration indicated; (a) 2 d LC50s (b) 4 and 5 d LC50s; Data in this plot are provided in Table S7.
509
24 ACS Paragon Plus Environment
Environmental Science & Technology
510 511 512 513 514 515 516
Figure 3. Chronic effect values for aromatic hydrocarbons a function of substance Log Kow. Empirical data are adjusted using reported class-specific correction factors (e.g., logLC50 - Δc, by re-arranging Eqn 2) to allow direct comparison to the target lipid model shown as the solid line; dashed lines indicate approximate chemical activities corresponding to 0.001, 0.01 and 0.1 from bottom to top respectively; Data in this plot are provided in Table S8.
25 ACS Paragon Plus Environment
Page 26 of 32
Page 27 of 32
517
Environmental Science & Technology
REFERENCE
1
Incardona J. P.; Collier, T. K.; Scholz, N. L. Defects in cardiac function precede morphological abnormalities in fish embryos exposed to polycyclic aromatic hydrocarbons. Toxicol. Appl. Pharm. 2004, 196 (2), 191-205. 2
Barron, M. G.; Carls, M. G.; Heintz, R. Evaluation of fish early life-stage toxicity models of chronic embryonic exposures to complex polycyclic aromatic hydrocarbon mixtures. Toxicol. Sci. 2004, 78 (1), 60-67. 3
HongBo, G.; XueDong, W.; ChengLian, B.; XiangJiang, C.; Tanguay, R. L.; QiaoXiang, D.; ChangJiang, H. Phenanthrene and fluorene-mediated early developmental toxicity in zebrafish. Fresen. Environ. Bull. 2010, 19 (1), 57-62. 4
Pauka, L. M.; Maceno, M.; Rossi, S. C.; Assis, H. C. S. Embryotoxicity and Biotransformation Responses in Zebrafish Exposed to Water-Soluble Fraction of Crude Oil. Bull. Environ. Contam. Toxicol. 2011, 86 (4), 389-393. 5
Mu, J. L.; Wang, X. H.; Jin, F.; Wang, J. Y.; Hong, H. S. The role of cytochrome P4501A activity inhibition in three- to five-ringed polycyclic aromatic hydrocarbons embryotoxicity of marine medaka (Oryzias melastigma). Mar. Pollut. Bull. 2012, 64 (7), 1445-1451.
6
Incardona, J. P.; Swarts, T. L.; Edmunds, R. C.; Linbo, T. L.; Aquilina-Beck, A.; Sloan, C. A.; Scholz, N. L. Exxon Valdez to Deepwater Horizon: Comparable toxicity of both crude oils to fish early life stages. Aquat. Toxicol. 2013, 142, 303-316. 7
Goodale, B. C.; Tilton, S. C.; Corvi, M. M.; Wilson, G. R.; Janszen, D. B.; Anderson, K. A.; Tanguay, R. L. Structurally distinct polycyclic aromatic hydrocarbons induce differential transcriptional responses in developing zebrafish. Toxicol. Appl. Pharm. 2013, 272 (3), 656-670. 8
Martin, J. D.; Adams, J.; Hollebone, B.; King, T.; Brown, R. S.; Hodson, P. V. Chronic toxicity of heavy fuel oils to fish embryos using multiple exposure scenarios. Environ. Toxicol. Chem. 2014, 33 (3), 677687. 9
Jung J-H; Kim, M., Yim, U.H.; Ha, S. Y.; Shim, W. J.; Chae, Y. S.; Kwon, J. H. Differential Toxicokinetics Determines the Sensitivity of Two Marine Embryonic Fish Species to Iranian Heavy Crude Oil. Envion. Sci. Technol. 2015, 49 (22), 13639-13648. 10
Esbaugh, A.J., Mager, E.W., Stieglitz, J.D.; Hoenig, R.; Brown, T. L.; French, B. L.; Incardona, J. P. The effects of weathering and chemical dispersion of Deepwater Horizon crude oil toxicity to mahi-mahi (Coryphaena hippurus). Sci. Tot. Environ. 2016, 543, 644-651. 11
Jee J-H, Kim S-G, Kang J-C. 2004. Effects of phenanthrene on growth and basic physiological functions of the olive flounder, Paralichthys olivaceus. J Exp. Mar. Biol. Eco. 2004, 304 (1), 123-136.
26 ACS Paragon Plus Environment
Environmental Science & Technology
12
Rhodes, S.; Farwell, A.; Hewitt, L. M.; MacKinnon, M.; Dixon, D. G. The effects of dimethylated and alkylated polycyclic aromatic hydrocarbons on the embryonic development of the Japanese medaka. Ecotoxicol. Environ. Saf. 2005, 60 (3), 247-258.
13
Li, R.; Zuo, Z.; Chen, D.; He, C.; Chen R.; Chen, Y.; Wang, C. Inhibition by polycyclic aromatic hydrocarbons of ATPase activities in Sebastiscus marmoratus larvae: Relationship with the development of early life stages. Mar. Environ. Res. 2011, 71 (1), 86-90.
14
Huang, L.; Gao, D.; Zhanga, Y.; Wang, C.; Zuo, Z. Exposure to low dose benzo[a]pyrene during early life stages causes symptoms similar to cardiac hypertrophy in adult zebrafish. J. Hazardous Materials 2014, 276, 377-382. 15
Kiparissis, Y.; Akhtar, P.; Hodson, P.; Brown, R. Partition-controlled delivery of toxicants: a novel in vivo approach for embryo toxicity testing. Environ. Sci. Technol. 2003, 37 (10), 2262-2266.
16
Peddinghaus, S.; Brinkmann, M.; Bluhm, K.; Sagner, A.; Hinger, G.; Braunbeck, T.; Keiter, S. H. Quantitative assessment of the embryotoxic potential of NSO-heterocyclic compounds using zebrafish (Danio rerio). Reprod. Toxicol. 2012, 33 (2), 224-232. 17
Maes, J.; Verlooy, L.; Buenafe, O. E.; de Witte, P. A. M.; Esguerra, C. V.; Crawford, A. D. Evaluation of 14 Organic Solvents and Carriers for Screening Applications in Zebrafish Embryos and Larvae. PLoS ONE 2013, 7(10): e43850. doi:10.3971/journal.pone.0043850. 18
Claeys, L.; Iaccino, F.; Janssen, C.R.; Van Sprang, P.; Verdonck, F. Development and validation of a quantitative structure-activity relationship for chronic narcosis to fish. Environ. Toxicol. Chem. 2013, 32 (10), 2217-2225.
19
Smith, K. E. C.; Dom, N.; Blust, R.; Mayer, P. Controlling and maintaining exposure of hydrophobic organic compounds in aquatic toxicity tests by passive dosing. Aquat. Toxicol. 2010, 98 (1), 15-24.
20
Turcotte, D.; Akhtar, P.; Bowerman, M.; Kiparissis, Y.; Brown, R.; Hodson, P. V. Measuring the toxicity of alkyl-phenanthrenes to early life stages of medaka (Oryzias latipes) using partition-controlled delivery. Environ. Toxicol. Chem. 2011, 30 (2), 487-495.
21
Butler, J. D.; Parkerton, T. F.; Letinski, D. J.; Bragin, G. E.; Lampi, M. A.; Cooper, K. R. A novel passive dosing system for determining the toxicity of phenanthrene to early life stages of zebrafish. Sci. Tot. Environ. 2013, 463, 952-958.
22
Seiler, T. B.; Best, N.; Fernqvist, M. M.; Hercht, H.; Smith, K. E. C.; Braunbeck, T.; Hollert, H. PAH toxicity at aqueous solubility in the fish embryo test with Danio rerio using passive dosing. Chemosphere 2014, 112, 77-84.
27 ACS Paragon Plus Environment
Page 28 of 32
Page 29 of 32
Environmental Science & Technology
23
Zhang, X.; Xia, X.; Li, H.; Zhu, B.; Dong, J. Bioavailability of Pyrene Associated with Suspended Sediment of Different Grain Sizes to Daphnia magna as Investigated by Passive Dosing Devices. Environ. Sci. Technol. 2015, 49 (16), 10127-10135.
24
Vergauwen, L., Schmidt, S.N., Stinckens, E.; Maho, W.; Blust, R.; Mayer, P.; Knapen, D. A high throughtput passive dosing format for the fish embryo acute toxicity test. Chemosphere 2015, 139, 9-17.
25
Smith, K. E.C.; Jeong, Y.; Kim, J. Passive dosing versus solvent spiking for controlling and maintaining hydrophobic organic compound exposure in the Microtox assay. Chemosphere 2015, 139, 174-180.
26
van der Heijden,S.A. Hermens, J.H.L, Sinnige, T.L., Mayer, P. Gilbert, D., Jonker, M. T. O. Determining High-Quality Critical Body Residues for Multiple Species and Chemicals by Applying Improved Experimental Design and Data Interpretation Concepts. Environ. Sci. Technol. 2015, 49 (3), 1879-1887. 27
Lin, H.; Morandi, G. D.; Brown, R. S.; Snieckus, V.; Rantanen, T.; Jørgensen, K. B., Hodson, P. V. Quantitative structure–activity relationships for chronic toxicity of alkylchrysenes and alkylbenz[a]anthracenes to Japanese medaka embryos (Oryzias latipes). Aquat. Toxicol. 2015, 159, 109118. 28
Halder, M.; Kienzler, A.; Whelan, M.; Worth, A. EURL ECVAM Strategy to replace, reduce and refine the use of fish in aquatic toxicity and bioaccumulation testing. European Commission Joint Research Centre, Institute for Health and Consumer Protection, Luxemborg, Publications Office of the European Union 2014, 26 pp. doi:10.2788/084219.
29
McGrath, J. A.; Di Toro, D. M. Validation of the target lipid model for toxicity assessment of residual petroleum constituents: Monocyclic and polycyclic aromatic hydrocarbons. Environ. Toxicol. Chem. 2009, 28 (6), 1130-1148. 30
Burgess, R. M.; Berry, W. J.; Mount, D. R.; Di Toro, D. M. Mechanistic sediment quality guidelines based on contaminant bioavailability: equilibrium partitioning sediment benchmarks. Environ. Toxicol. Chem. 2013, 32 (1), 102-114. 31
Redman, A.D.; Parkerton, T. F.; Paumen, M. L.; McGrath, J. A.; Di Toro, D. M. Extension and validation of the target lipid model for deriving predicted no effect concentrations for soils and sediments. Environ. Toxicol. Chem. 2014, 33 (12), 2679-2687. 32
U.S. Environmental Protection Agency. Evaluating Ecological Risks to Invertebrate Receptors from PAHs in Sediments at Hazardous Waste Sites, EPA/600/R-06/162F, Office of Research and Development, Naragansett, RI, 2009, 19pp. http://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=492591. 33
U.S. Environmental Protection Agency 2010a. EPA Response to BP Spill in the Gulf of Mexico: Sediment Benchmarks for Aquatic Life http://www.epa.gov/bpspill/water/explanation-of-pahbenchmark-calculations-20100622.pdf.
28 ACS Paragon Plus Environment
Environmental Science & Technology
34
U.S. Environmental Protection Agency 2010b. EPA Response to BP Spill in the Gulf of Mexico: Water Quality Benchmarks for Aquatic Life http://www.epa.gov/bpspill/sediment-benchmarks.html#dblstar. 35
Redman, A. D.; Parkerton, T. F.; McGrath, J. A.; Di Toro, D. M. An aquatic toxicity model for complex petroleum substances. Environ. Toxicol. Chem. 2012, 31 (11), 2498-2506. 36
Redman, A. D.; Parkerton, T. F.; Comber, M. H. I.; Paumen, M. L.; Eadsforth, C. V.; Dmytrasz, B.; King, D.; Warren, C. S.; den Haan, K. H.; Djemel, N. PETRORISK: a risk assessment framework for petroleum substances. Integr. Environ. Assess. Manag. 2014, 10 (3), 437-448.
37
Mayer, P.; Reichenberg, F. Can highly hydrophobic organic substances cause aquatic baseline toxicity and can they contribute to mixture toxicity? Environ. Toxicol. Chem. 2006, 25 (10), 2639-2644. 38
Mackay, D.; Arnot, J. A.; Wania, F.; Bailey, R. E. Chemical Activity as an Integrating Concept in Environmental Assessment and Management of Contaminants. Integr. Environ. Assess. Manag. 2011, 7 (2), 248-255. 39
Mayer, P.; Holmstrup, M. Passive dosing of soil invertebrates with polycyclic aromatic hydrocarbons: limited chemical activity explains toxicity cutoff. Environ. Sci. Technol. 2008, 42 (19), 7516-7521. 40
Engraff, M.; Solere, C.; Smith, K. E.; Mayer, P.; Dahllöf, I. Aquatic toxicity of PAHs and PAH mixtures at saturation to benthic amphipods: Linking toxic effects to chemical activity. Aquat. Toxicol. 2011, 102 (3), 142-149. 41
Rojo-Nieto, E.; Smith, K. E. C.; Perales, J. A.; Mayer, P. Recreating the seawater mixture composition of HOCs in toxicity tests with Artemia franciscana by passive dosing. Aquat. Toxicol. 2012, 120, 27-34.
42
Lee, S. Y.; Kang, H. J.; Kwon, J. H. Toxicity cutoff of aromatic hydrocarbons for luminescence inhibition of Vibrio fischeri. Ecotox. Environ. Safety 2013, 94, 116-122.
43
Schmidt, S. N.; Holmstrup, M.; Smith, K. E. C.; Mayer, P. Passive Dosing of Polycyclic Aromatic Hydrocarbon (PAH) Mixtures to Terrestrial Springtails: Linking Mixture Toxicity to Chemical Activities, Equilibrium Lipid Concentrations, and Toxic Units. Environ. Sci. Technol. 2013, 47 (13), 7020-7027.
44
Dai, Y. J.; Jia, Y. F.; Chen, N.; Bian, W. P.; Li, Q. K.; Ma, Y. B.; Chen, Y. L.; Pei, D. S. Zebrafish as a model system to study toxicology. Environ. Toxicol. Chem. 2014, 33 (1), 11-17.
45
Busquet, F.; Strecker, R.; Rawlings, J. M. et al. OECD validation study to assess intra- and interlaboratory reproducibility of the zebrafish embryo toxicity test for acute aquatic toxicity testing. Regul. Toxicol. Pharm. 2014, 69 (3), 496-511. 46
Padilla, S.; Corum, D.; Padnos, B. et al. Zebrafish developmental screening of the ToxCast (TM) Phase I chemical library. Reprod. Toxicol. 2012, 33 (2), 174-187.
29 ACS Paragon Plus Environment
Page 30 of 32
Page 31 of 32
Environmental Science & Technology
47
Karickhoff, S. W.; McDaniel, V. K.; Melton, C.; Vellino, A. N.; Nute, D. E.; Carreira, L. A. Predicting chemical reactivity by computer. Environ. Toxicol. Chem. 1991, 10 (11), 1405–1416. 48
OECD, 2006. Draft Proposal for a New Guideline, Fish Embryo Toxicity (FET) Test. Test No. 203.
49
Westerfield, M., 2001. The Zebrafish Book: A Guide for the Laboratory Use of Zebrafish (Danio rerio). University of Oregon Press.
50
Standard Methods for the Examination of Water and Wastewater 21st Edition method 8010E (2005).
51
Belanger, S. E.; Balon, E. K.; Rawlings, J. M. Saltatory ontogeny of fishes and sensitive early life stages for ecotoxicology tests. Aquat. Toxicol. 2010, 97 (2), 88–95.
52
OECD, 1992.OECD Guidelines for the Testing of Chemicals. Fish Early Life Stage Toxicity Test No. 210: Fish, Juvenile Growth Test. Organization for Economic Cooperation and Development, Paris, France. 53
Di Toro, D. M.; McGrath, J. A.; Stubblefield, W. A. Predicting the toxicity of neat and weathered crude oil: toxic potential and the toxicity of saturated mixtures. 2007, Environ. Toxicol. Chem. 26 (1), 24–36. 54
SAS Version 9.3. Copyright© 2002-2010 by SAS Institute Inc., Cary, NC, USA.
55
Finney, D.J. Probit Analysis, 3rd Edition, London, 1971: Cambridge University Press.
56
Bland, M.J.; Altman, D. G. Multiple significance tests: the Bonferroni method. British Medical Journal 1995, 310 (6973), 170. 57
Finney, D.J. The Fisher-Yates Test of Significance in 2X2 Contingency Tables. 1948, Biometrika, 35 (1/2), 145-156. 58
Pearson, E. S.; Hartley, H. O. Biometrika Tables for Statisticians. Vol. 1. Cambridge University Press, London, England. 1962, 65-70. 59
WEST Inc. and Gulley, D. D. TOXSTAT, V.3.4. Western EcoSystems Technology, Inc. Cheyenne, WY, 1994.
60
GraphPad Prism version 5.00 for Windows, GraphPad Software, San Diego California USA, www.graphpad.com
61
Smith, K. E. C.; Dom, N.; Blust, R.; Mayer, P. Corrigendum to “Controlling and maintaining exposure of hydrophobic organic compounds in aquatic toxicity tests by passive dosing.” Aquat. Toxicol. 2010, 98 (1), 15-24. 62
Schmidt, S. N.; Mayer, P. Linking algal growth to chemical activity: baseline toxicity required at 1% of saturation. Chemosphere 2015, 120, 305-308.
30 ACS Paragon Plus Environment
Environmental Science & Technology
63
Paumen, M. L.; de Voogt, P.; van Gestel, C. A. M.; Kraak, M. H. S. Comparative chronic toxicity of homo- and heterocyclic aromatic compounds to benthic and terrestrial invertebrates: Generalizations and exceptions. Sci. Total Environ. 2009, 407 (16), 4605-4609.
64
Roex, E. W. M.; de Vries, E.; van Gestel, C. A. M. Sensitivity of the zebrafish (Danio rerio) early life stage test for compounds with different modes of action. Environ. Pollut. 2002, 120 (2), 355-362. 65
Mackay, D.; Shiu, W. Y.; Ma, K. C. Illustrated Handbook of Physical-Chemical Properties and Environmental Fate of Organic Chemicals; Lewis Publishers: Boca Raton, FL, 1992.
66
Verbruggen, E. M. J. Environmental risk limits for polycyclic aromatic hydrocarbons (PAHs) For direct aquatic, benthic, and terrestrial Toxicity, RIVM report 607711007, National Institute for Public Health and the Environment, Bilthoven, The Netherlands 2012; pp 337.
67
Hannah, J. B.; Hose, J. E.; Landolt, M. L.; Miller, B. S.; Felton, S. P.; Iwaoka, W. T. Benzo[a]pyreneinduced morphologic and developmental abnormalities in rainbow trout. Arch. Environ. Contam. Toxicol. 1982, 11 (6), 727-734.
68
Matthew, R.; McGrath, J. A.; DiToro, D. M. Modeling polycyclic aromatic hydrocarbon bioaccumulation and metabolism in time-variable early life stages exposures. Environ. Toxicol. Chem. 2008, 27 (7), 15151525.
69
Nichols, J. W.; Hoffman, A. D.; ter Laak, T. L.; Fitzsimmons, P. N. Hepatic clearance of 6 Polycyclic Aromatic Hydrocarbons by Isolated Perfused Trout Livers: Prediction From In Vitro Clearance by Liver S9 Fractions. Toxicol. Sci. 2013, 136 (2), 359-372. 70
Kuhnert, A.; Vogs, C.; Altenburger, A.; Kusterv, E. The internal concentration of organic substances in fish embryos - a toxciokinetic approach. Environ. Toxicol. Chem. 2013, 32 (8), 1819-1827. 71
Hoffmann, J. L.; Oris, J. T. Altered gene expression: A mechanism for reproductive toxicity in zebrafish exposed to benzo[a]pyrene. Aquat. Toxicol. 2006, 78 (4), 332-340.
72
OECD. (2013), Test No. 236: Fish Embryo Acute Toxicity (FET) Test, OECD Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris. DOI: http://dx.doi.org/10.1787/9789264203709-en 73
Villeneuve, D.; Volz, D. C.; Embry, M. R. et al. Investigating alternatives to the fish early-life stage test: a strategy for discovering and annotating adverse outcome pathways for early fish development. Environ. Toxicol. Chem. 2014, 33 (1), 158-169.
31 ACS Paragon Plus Environment
Page 32 of 32