question archive ECOTOXICOLOGY A ubiquitous tire rubber–derived chemical induces acute mortality in coho salmon Zhenyu Tian1,2, Haoqi Zhao3, Katherine T
ECOTOXICOLOGY A ubiquitous tire rubber–derived chemical induces acute mortality in coho salmon Zhenyu Tian1,2, Haoqi Zhao3, Katherine T
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ECOTOXICOLOGY
A ubiquitous tire rubber–derived chemical induces acute mortality in coho salmon Zhenyu Tian1,2, Haoqi Zhao3, Katherine T. Peter1,2, Melissa Gonzalez1,2, Jill Wetzel4, Christopher Wu1,2, Ximin Hu3, Jasmine Prat4, Emma Mudrock4, Rachel Hettinger1,2, Allan E. Cortina1,2, Rajshree Ghosh Biswas5, Flávio Vinicius Crizóstomo Kock5, Ronald Soong5, Amy Jenne5, Bowen Du6, Fan Hou3, Huan He3, Rachel Lundeen1,2, Alicia Gilbreath7, Rebecca Sutton7, Nathaniel L. Scholz8, Jay W. Davis9, Michael C. Dodd3, Andre Simpson5, Jenifer K. McIntyre4, Edward P. Kolodziej1,2,3*
In U.S. Pacific Northwest coho salmon (Oncorhynchus kisutch), stormwater exposure annually causes unexplained acute mortality when adult salmon migrate to urban creeks to reproduce. By investigating this phenomenon, we identified a highly toxic quinone transformation product of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), a globally ubiquitous tire rubber antioxidant. Retrospective analysis of representative roadway runoff and stormwater-affected creeks of the U.S. West Coast indicated widespread occurrence of 6PPD-quinone (<0.3 to 19 micrograms per liter) at toxic concentrations (median lethal concentration of 0.8 ± 0.16 micrograms per liter). These results reveal unanticipated risks of 6PPD antioxidants to an aquatic species and imply toxicological relevance for dissipated tire rubber residues.
H umans discharge tens of thousands of chemicals and related transformation products to water (1), most of which re- main unidentified and lack rigorous toxicity information (2). Efforts to iden-
tify and mitigate high-risk chemical toxicants are typically reactionary, occur long after their use becomes habitual (3), and are frequently stymied by mixture complexity. Societal man- agement of inadvertent, yet widespread, chem- ical pollution is therefore costly, challenging, and often ineffective. The pervasive biological degradation of con-
taminated waters near urban areas (“urban stream syndrome”) (4) is exemplified by an acute mortality phenomenon that has affected Pacific Northwest coho salmon (Oncorhynchus kisutch) for decades (5–9). “Urban runoff mor- tality syndrome” (URMS) occurs annually among adult coho salmon returning to spawn in freshwaters where concurrent stormwater exposure causes rapid mortality. In the most urbanized watersheds with extensive imper- vious surfaces, 40 to 90% of returning salmon may die before spawning (9). This mortality
threatens salmonid species conservation across ~40% of the Puget Sound land area despite costly societal investments in physical habitat restoration that may have inadvertently created ecological traps through episodic toxic water pollution (9). Although URMS has been linked to degraded water quality, urbanization, and high traffic intensity (9), one or more causal toxicants have remained unidentified. Spurred by these compelling observations and mindful of the many other insidious sublethal storm- water impacts, we have worked to characterize URMS water quality (10, 11). Previously, we reported that URMS-associated
waters had similar chemical compositions rel- ative to roadway runoff and tire tread wear particle (TWP) leachates, providing an open- ing clue in our toxicant search (10). In this work, we applied hybrid toxicity identifica- tion evaluation and effect-directed analysis to screen TWP leachate for its potential to induce mortality (a phenotypic anchor) in juvenile coho salmon as an experimental proxy for adult coho (6). Using structural identifica- tion by means of ultrahigh-performance liquid chromatography–high-resolution tandem mass spectrometry (UPLC-HRMS/MS) and nuclear magnetic resonance (NMR), we discovered that an antioxidant-derived chemical was the primary causal toxicant. Retrospective anal- ysis of runoff and receiving waters indicated that detected environmental concentrations of this toxicant often exceeded acute mortality thresholds for coho during URMS events in the field and across the U.S. West Coast. Aqueous TWP leachate stock (1000 mg/liter)
was generated from an equal-weight mix of tread particles (0.2 ± 0.3 mm2 average surface area) (fig. S1) from nine used and new tires (table S1). TWP leachate (250 mg/liter posi- tive controls) was acutely and rapidly (~2 to
6 hours) lethal to juvenile coho (24 hours ex- posures, 98.5% mortality, n = 135 fish from 27 exposures) (data file S1), even after heating (80°C, 72 hours; 100% mortality, n = 10 fish from two exposures), indicating stability dur- ing handling. Behavioral symptomology (circl- ing, surface gaping, and equilibrium loss) (fig. S2 and movie S1) of TWP leachate exposures mirrored laboratory and field observations of symptomatic coho (5, 6). No mortality occurred in negative controls, including solvent- and process-matched method blanks subjected to identical separations (0 of 80 fish, 16 expo- sures) or exposure water blanks (0 of 45 fish, nine exposures). Mixture complexity [measured here as num-
ber of UPLC-HRMS electrospray ionization (ESI+) chemical features] was a substantial barrier to causal toxicant identification be- cause 250 mg/liter TWP leachate typically contained more than 2000 ESI+ detections. Our fractionation studies, optimized over 2-plus years through iterative exploration of toxicant chemical properties, focused on re- ducing these detection numbers to attain a simple, yet toxic, fraction amenable to indi- vidual compound identifications. Throughout this fractionation procedure, observed toxicity remained confined to one narrow fraction, which is consistent with a single compound or a small, structurally related family of causal toxicants. In initial studies, TWP leachate toxi- city was unaffected by silica sand filtration, cation and anion exchange, and ethylenedia- minetetraacetic acid (EDTA) (114 mM) addi- tion (12), indicating that toxicant(s) were not particle-associated, strongly ionic, or metals, respectively, and validating prior studies that eliminated candidate pollutants (13, 14) as pri- mary causal toxicants. Mixture complexity was reduced by using
cation exchange, two polarity-based separa- tions (XAD-2 resin and silica gel), and reverse- phase high-performance liquid chromatography (HPLC) on a semipreparative C18 column (250 by 4.2 mm ID, 5 mm particle size). After C18-HPLC generated 10 fractions, only C18-F6 (10 to 11 min) was toxic; it contained ~225 ESI+ and ~70 ESI– features (Fig. 1). Having removed ~90% of features, we began to prioritize and identify candidate toxicants by abundance (peak area), followed by fish exposures with commercial standards at fivefold higher con- centrations (mixtures at 1 to 25 mg/liter) than those estimated in C18-F6. We identified 11 plas- ticizers, antioxidants, emulsifiers, and various transformation products, including some well- known environmental contaminants [such as tris(2-butoxyethyl) phosphate] and some that are rarely reported [such as di(propylene gly- col) dibenzoate and 2-(1-phenylethyl)phenol] (table S2). We also detected several bioac- tive, structurally related phenolic antioxidants and their transformation products (2,6-di-t-
RESEARCH
Tian et al., Science 371, 185–189 (2021) 8 January 2021 1 of 5
1Center for Urban Waters, Tacoma, WA 98421, USA. 2Interdisciplinary Arts and Sciences, University of Washington Tacoma, Tacoma, WA 98421, USA. 3Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195, USA. 4School of the Environment, Washington State University, Puyallup, WA 98371, USA. 5Department of Chemistry, University of Toronto, Scarborough Campus, 1265 Military Trail, Toronto, ON M1C 1A4, Canada. 6Southern California Coastal Water Research Project, Costa Mesa, CA 92626, USA. 7San Francisco Estuary Institute, 4911 Central Avenue, Richmond, CA 94804, USA. 8Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98112, USA. 9U.S. Fish and Wildlife Service, Washington Fish and Wildlife Office, Lacey, WA 98503, USA. *Corresponding author. Email: koloj@uw.edu
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butyl-4-hydroxy-4-methyl-2,5-cyclohexadie- none, 3,5-di-t-butyl-4-hydroxybenzaldehyde, and 7,9-di-tert-butyl-1-oxaspiro[4,5]deca-6,9- diene-2,8-dione) (15). However, over many rounds of identification and subsequent ex- posure to juvenile coho, none of these identi- fied chemical exposures reproduced URMS symptoms or induced mortality. Because these identifications used exhaustive environmental scientific literature searches (10, 16, 17), we suspected a previously unreported toxicant. To sharpen our search, we used multidi-
mensional semipreparative HPLC using two additional structurally distinct column phases [pentafluorophenyl (PFP) and phenyl]. Paral- lel fractionations (same column dimensions, mobile phase, and gradient as for C18-HPLC) (18) of the toxic silica gel fraction generated toxic fractions of PFP-F6 (10 to 11 min; ~204 ESI+, 60 ESI– features) and phenyl-F4 (8 to 9 min; ~237 ESI+, 75 ESI– features); all other fractions were nontoxic. Across these sepa- rations (C18, PFP, phenyl), only four ESI+ and three ESI– HRMS features co-occurred in all three toxic fractions (fig. S3). Of these, one unknown compound [mass/charge ratio (m/z) 299.1752, C18H22N2O2, RT 11.0 min on ana- lytical UPLC-HRMS] dominated the detected peak area (10-fold higher intensity in both ESI+ and ESI–). To further resolve candidate toxicants for synthetic efforts, we converted the three-dimensional chromatography work- flow from parallel to serial through sequen- tial C18, PFP, and phenyl columns (C18-F6 to PFP-F6 to phenyl-F4; with solvent removal by means of centrifugal evaporation and tox- icity confirmation between separations). The purified final fraction was chemically simple (four ESI+, three ESI– detections), highly lethal (100% mortality in 4 hours; n = 15 coho, three exposures), and was again dominated by C18H22N2O2. Drying this fraction yielded a pink-magenta precipitate (Fig. 1). Published characterizations of crumb rub-
ber (16) and receiving waters (10, 17) did not mention C18H22N2O2. UPLC-HRMS/MS spectra indicated C4H10 and C6H12 alkyl losses (M-58 and M-84 fragments) (Fig. 2B), but MS3 and MS4 fragmentation yielded no additional structural insights (fig. S4). Additionally, in silico fragmentation (MetFrag, CSI:FingerID) of C18H22N2O2 compounds in PubChem and ChemSpider (15,624 and 17,105 structures, re- spectively) failed to match observed fragments. Thus, to the best of our knowledge, C18H22N2O2 was not described in environmental literature or databases and posed a “true unknown” iden- tification problem (19). We then assumed a transformation product; industrial manu- facturing (such as high heat or pressure, or catalysis) and diverse reactions in environ- mental systems generate many undocumented transformation products, most of which lack commercial standards.
Tian et al., Science 371, 185–189 (2021) 8 January 2021 2 of 5
Fig. 1. Tire rubber leachate fractionation scheme. As a metric of mixture complexity and separation efficiency, the numbers above gray bars represent distinct chemical features detected in solid-phase extracted fish exposure water (1 liter) and subsequent fractions by means of UPLC-HRMS. Blue indicates nonlethal fractions; red indicates lethal fractions. All fractionation steps and exposures were replicated at least twice; positive and negative controls were included throughout fractionations. (Inset) Purified product (~700 mg from 30 liter of TWP leachate) in the final lethal fraction. TWP, tire tread wear particles; CEX, cation exchange; EA, ethyl acetate; EtOH, ethanol; H2O, water; Hex, hexane; DCM, dichloromethane; RT, retention time.
Fig. 2. 6PPD-quinone identification and a proposed formation pathway. (A) Extracted ion chromato- grams of 6PPD-quinone from UPLC-HRMS (ESI+); red data indicate the final fraction from TWP leachate, and black data indicate the purified 6PPD ozonation mixture. (B) Observed MS/MS fragmentation (integrated from 10, 20, and 40 eV) of 6PPD-quinone in the final toxic fraction from TWP leachate (red spectra) and 6PPD ozonation (black spectra). (C) One proposed reaction pathway from 6PPD to 6PPD-quinone (alternate proposed formation pathways are provided in fig. S13). Red highlights indicate key changes in the diphenylamine structure during ozonation.
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Our breakthrough came by assuming that abiotic environ- mental transformations com- monly modify active functional groups by preferentially altering the numbers of hydrogen and oxygen atoms relative to carbon and nitrogen. By searching a recent U.S. Environmental Pro- tection Agency (EPA) crumb rubber report (16) for related formulas (C18H0-xN2-4O0-y), sev- eral characteristics of the C18H24N2 anti-ozonant “6PPD” [N-(1,3- dimethylbutyl)-N′-phenyl-p- phenylenediamine] matched necessary attributes. First, 6PPD is globally ubiquitous (0.4 to 2% by mass) in passenger and com- mercial vehicle tire formulations (20), indicating sufficient pro- duction to explain mortality observations within large and geographically distinct receiv- ing water volumes. 6PPD was present in TWP leachate but was completely removed during frac- tionation through cation ex- change. 6PPD crystals are purple, similar to the pink-magenta pre- cipitate obtained after fractiona- tion. Most compellingly, neutral losses in 6PPD gas chromatog- raphy (GC)–MS spectra matched the C18H22N2O2 GC-HRMS spec- tra (fig. S5), and the predicted logKow of 6PPD (5.6) (Kow, n- octanol-water partition coeffi- cient) was close to that for C18H22N2O2 (5 to 5.5) (11). Last, literature detailing the indus- trial chemistry of 6PPD reactions with ozone [7 days, 500 parts per billion vol- ume (ppbv)] described a C18H22N2O2 product (21), leading us to hypothesize that 6PPD was the likely protoxicant (Fig. 2C). We tested this hypothesis with gas-phase
ozonation (500 ppbv O3) of industrial grade 6PPD (96% purity) (21). A C18H22N2O2 prod- uct formed; UPLC-HRMS analysis demon- strated exact matches of retention time (11.0 min) and MS/MS spectra between this synthetic C18H22N2O2 and the TWP leachate fractionation- derived C18H22N2O2 (Fig. 2, A and B). When purified, the ozone-synthesized C18H22N2O2 formed a reddish-purple precipitate. One- dimensional 1H NMR structural analysis con- firmed identical TWP leachate–derived and ozone-synthesized C18H22N2O2 structures (figs. S6 to S7). Two-dimensional NMR spectra and related simulations revealed isolated tertiary carbons and carbonyl groups (figs. S8 to S12), clearly indicating a quinone structure for C18H22N2O2 rather than the dinitrone struc-
ture reported in the past 40 years of literature describing 6PPD ozonation products (21). Therefore, the C18H22N2O2 candidate toxicant was unequivocally “6PPD-quinone” {2-anilino- 5-[(4-methylpentan-2-yl)amino]cyclohexa-2,5- diene-1,4-dione}. Consistent with environmental 6PPD ozonation, reported 6PPD ozonation products C18H22N2O (formula-matched) and 4-nitrosodiphenylamine (C12H10N2O, standard- confirmed) (21) also were detected in ozo- nation mixtures and nontoxic TWP leachate fractions. Exposures to ozone-synthesized and tire
leachate–derived 6PPD-quinone (~20 mg/liter nominal concentrations) both induced rapid (<5 hours, with initial symptoms evident within 90 min) mortality (n = 15 fish, three exposures) (fig. S2 and movie S2), which matched the 2 to 6 hours mortality observed for positive controls. Behavioral symptomol- ogy in response to synthetic 6PPD-quinone exposures matched that from field observa-
tions, roadway runoff, bulk TWP leachate, and final toxic TWP frac- tion exposures, confirming the phenotypic anchor (5–9). Using synthetic 6PPD-quinone (purity ~98%), we performed controlled dosing experiments (10 concen- trations, n = 160 fish in two inde- pendent exposures). 6PPD-quinone was highly toxic [median lethal concentration (LC50) 0.79 ± 0.16 mg/ liter] to juvenile coho salmon (Fig. 3B). Estimates of LC50 through con- trolled exposures closely matched estimates derived from bulk road- way runoff and TWP leachate expo- sures (LC50 0.82 ± 0.27 mg/liter), indicating the primary contribution of 6PPD-quinone to observed mix- ture toxicity (Fig. 3A). Direct com- parisons with 6PPD were performed (LC50 250 ± 60 mg/liter through no- minal concentrations) (fig. S14), but confident assessment of 6PPD toxi- city was precluded by its poor solu- bility, high instability, and formation of products during exposure. To assess environmental rele-
vance, we used UPLC-HRMS to ret- rospectively quantify 6PPD-quinone in archived extracts from roadway runoff and receiving water sam- pling (fig. S15 and table S4) (10). In Seattle-region roadway runoff (n = 16 of 16 samples), 0.8 to 19 mg/liter 6PPD-quinone was detected (Fig. 4A). During seven storm events in three Seattle-region watersheds highly affected by URMS, 6PPD- quinone occurred at <0.3 to 3.2 mg/ liter (n = 6 of 7 discrete storm events; n = 6 of 21 samples when
including samples collected across the full hydrograph). These samples included three storms with documented URMS mortality in adult coho salmon; 6PPD-quinone was not detected in pre- and poststorm samples, but concentrations were near or above LC50 values during storms. We also detected 6PPD-quinone in Los Angeles region roadway runoff (n = 2 of 2 samples, 4.1 to 6.1 mg/liter) and San Francisco region creeks affected by urban runoff (n = 4 of 10 samples, 1.0 to 3.5 mg/liter). These data implicate 6PPD-quinone as the
primary causal toxicant for decades of storm- water-linked coho salmon acute mortality ob- servations. Although minor contributions from other constituents in these complex mixtures are possible, 6PPD-quinone was both necessary (consistently present in and absent from toxic and nontoxic fractions, respectively) and, when purified or synthesized as a pure chemical ex- posure, sufficient to produce URMS at envi- ronmental concentrations. Over the product
Tian et al., Science 371, 185–189 (2021) 8 January 2021 3 of 5
Fig. 3. Dose-response curves. (A) Dose-response curve for 24-hour juvenile coho exposures to roadway runoff and TWP leachate (n = 365 fish). Error bars represent three replicates of eight fish (except TWP leachate 2, n = 5 fish; Seattle site 1, duplicate of n = 10 fish). 6PPD-quinone concentrations were from retrospective quantification. (B) Dose-response curves for 24-hour juvenile coho exposures to ozone-synthesized 6PPD-quinone (10 concentrations, two replicates, n = 160 fish). Curves were fitted to a four-parameter logistic model. CI, confidence interval.
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life cycle, antioxidants [such as PPDs, TMQs (2,2,4-trimethyl-1,2-dihydroquinoline), and phenolics] are designed to diffuse to tire rub- ber surfaces, rapidly scavenge ground-level atmospheric ozone and other reactive oxidant species, and form protective films to prevent ozone-mediated oxidation of structurally im- portant rubber elastomers (21, 22). Accord- ingly, all 6PPD added to tire rubbers is designed to react, intentionally forming 6PPD-quinone and related transformation products that are subsequently transported through the environ- ment. This anti-ozonant application of 6PPD inadvertently, yet drastically, increases road- way runoff toxicity and environmental risk by forming the more toxic and mobile 6PPD- quinone transformation product. On the basis of the ubiquitous use and substantial mass fraction (0.4 to 2%) of 6PPD in tire rubbers and the representative detections across the U.S. West Coast (table S4), which include many detections near or above LC50 values, we believe that 6PPD-quinone may be present broadly in peri-urban stormwater and roadway run-off at toxicologically relevant concentrations for sen- sitive species, such as coho salmon. Globally, ~3.1 billion tires are produced an-
nually for our more than 1.4 billion vehicles, resulting in an average 0.81 kg per capita an- nual emission of tire rubber particles (23). TWPs are one of the most substantial micro-
plastics sources to freshwaters (24); 2 to 45% of total tire particle loads enter receiving waters (25, 26), and freshwater sediment contains up to 5800 mg/kg TWP (23, 24, 27). Supporting recent concerns about microplastics (24, 28), 6PPD-quinone provides a compelling mecha- nistic link between environmental microplas- tic pollution and associated chemical toxicity risk. Although numerous uncertainties exist regarding the occurrence, fate, and transport of 6PPD-quinone, these data indicate that aqueous and sediment environmental TWP residues can be toxicologically relevant and that existing TWP loading, leaching, and tox- icity assessments in environmental systems are clearly incomplete (25). Tire rubber dis- posal also represents a major global materials problem and potential potent source of 6PPD- quinone and other tire-derived transformation products. In particular, scrap tires repurposed as crumb rubber in artificial turf fields (17) suggest both human and ecological expo- sures to these chemicals. Accordingly, the human health effects of such exposures merit evaluation. Environmental discharge of 6PPD-quinone
is particularly relevant for the many receiving waters proximate to busy roadways (Fig. 4B). It is unlikely that coho salmon are uniquely sensitive, and the toxicology of 6PPD transfor- mation products in other aquatic species should
be assessed. For example, used tires were more toxic to rainbow trout (75% lower 96 hours LC50) relative to new tires (29), an observation that is consistent with adverse outcomes me- diated by transformation products. If manage- ment of 6PPD-quinone discharges is needed to protect coho salmon or other aquatic orga- nisms, adaptive regulatory and treatment strat- egies (17, 30, 31) along with source control and “green chemistry” substitutions [identifying demonstrably nontoxic and environmentally benign replacement antioxidants (22, 32)] can be considered. More broadly, we recommend more careful toxicological assessment for trans- formation products of all high-production- volume commercial chemicals subject to pervasive environmental discharge.
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ACKNOWLEDGMENTS
We thank D. Whittington; S. Edgar (University of Washington Medicine Mass Spectrometry); M. Bozlee (City of Tacoma); J. Protasio; A. Rue (Washington State Department of Ecology); M. Goehring (King County); D. E. Latch (Seattle University); J. E. Baker; C. A. James; A. D. Gipe (University of Washington Tacoma); M. Yu (Mount Sinai); S. D. Richardson (University of South Carolina); J. R. Cameron [National Oceanic and Atmospheric Administration (NOAA) NWFSC]; K. King (U.S. Fish and Wildlife Service); Washington State Department of Transportation; and dedicated citizen scientists from the Miller Walker Community Salmon Investigation, Puget Soundkeeper, and Thornton Creek Alliance. We gratefully thank the Puyallup Tribe and NOAA NWFSC for providing juvenile coho and Agilent Technologies (T.A. and D.C.) for technical support. Funding: This work was supported by NSF grants 1608464 and 1803240, EPA grant 01J18101 (E.P.K.), DW-014-92437301 (N.L.S., J.K.M., and J.W.D.), Washington State Governors Funds (J.K.M. and E.P.K.), the Burges Fellowship (H.Z.), the Regional Monitoring Program for Water Quality in San Francisco Bay (A.G. and R.S.), Brazilian foundation agency FAPESP (2018/16040-5 and 2019/14770-9) (F.V.C.K.), NSERC Alliance (ALLRP 549399) and Discovery (RGPIN-2019-04165) Programs, the Canada Foundation for Innovation (CFI), the Ontario Ministry of Research and Innovation, and the Krembil Foundation (A.S.). Disclaimer: Findings and conclusions herein are those of the authors
and do not necessarily represent the views of the sponsoring organizations. Author contributions: Z.T., H.Z., K.T.P., J.K.M., M.C.D., and E.P.K. designed research; Z.T., H.Z., M.G., K.T.P., C.W., R.H., and A.E.C. performed fractionation experiments; Z.T., K.T.P., R.L., and M.G. performed HRMS and data analysis; Z.T., H.Z., M.G., J.W., K.T.P., C.W., R.H., E.P.K., J.K.M., and A.E.C. conducted fish exposures; J.P., C.W., and J.W. generated TWP particles; J.W., J.P., E.M., and J.K.M. maintained the fish facility and enabled exposure studies; R.G.B., F.V.C.K., R.S., A.J., and A.S. elucidated structures by means of NMR; K.T.P., C.W., F.H., Z.T., M.G., B.D., A.G., and R.S. provided water samples; X.H., Z.T., H.Z., H.H., and M.C.D. performed ozonation experiments; N.L.S. and J.W.D. provided perspectives and context; and Z.T., H.Z., K.T.P., and E.P.K. wrote the manuscript. Competing interests: None declared. Data and materials availability: Data file S1 includes the record of the juvenile coho salmon exposure experiments. Number of tanks and coho salmon used, mortality results, and treatment information are included inthe table. All other data needed to evaluate the conclusions in the paper are present in the paper or the supplementary materials.
SUPPLEMENTARY MATERIALS
science.sciencemag.org/content/371/6525/185/suppl/DC1 Materials and Methods Supplementary Text Figs. S1 to S15 Tables S1 to S5 References (33–47) Movies S1 and S2 Data File S1
8 July 2020; accepted 5 November 2020 Published online 3 December 2020 10.1126/science.abd6951
Tian et al., Science 371, 185–189 (2021) 8 January 2021 5 of 5
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http://science.sciencemag.org/
derived chemical induces acute mortality in coho salmon−A ubiquitous tire rubber
Michael C. Dodd, Andre Simpson, Jenifer K. McIntyre and Edward P. Kolodziej Jenne, Bowen Du, Fan Hou, Huan He, Rachel Lundeen, Alicia Gilbreath, Rebecca Sutton, Nathaniel L. Scholz, Jay W. Davis, Mudrock, Rachel Hettinger, Allan E. Cortina, Rajshree Ghosh Biswas, Flávio Vinicius Crizóstomo Kock, Ronald Soong, Amy Zhenyu Tian, Haoqi Zhao, Katherine T. Peter, Melissa Gonzalez, Jill Wetzel, Christopher Wu, Ximin Hu, Jasmine Prat, Emma
originally published online December 3, 2020DOI: 10.1126/science.abd6951 (6525), 185-189.371Science
, this issue p. 185Science show concentrations of 6PPD-quinone high enough to account for the acute toxicity events. intended to prevent damage to tire rubber from ozone. Measurements from road runoff and immediate receiving waters
1 microgram per liter. The compound, called 6PPD-quinone, is an oxidation product of an additive∼concentrations of through chromatography steps, eventually isolating a single molecule that could induce acute toxicity at threshold
followed toxic fractionset al.not been known. Starting from leachate from new and aged tire tread wear particles, Tian hasRegular acute mortality events are tied, in particular, to stormwater runoff, but the identity of the causative toxicant(s)
For coho salmon in the U.S. Pacific Northwest, returning to spawn in urban and suburban streams can be deadly. Tire tread particles turn streams toxic
ARTICLE TOOLS http://science.sciencemag.org/content/371/6525/185
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CONTENT RELATED http://science.sciencemag.org/content/sci/370/6521/1145.full
REFERENCES
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