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Borgert CJ. Hypothesis-driven weight of evidence evaluation indicates styrene lacks endocrine disruption potential. Crit Rev Toxicol 2023:1-16. [PMID: 37216681 DOI: 10.1080/10408444.2022.2112652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 08/01/2022] [Accepted: 08/02/2022] [Indexed: 05/24/2023]
Abstract
Styrene is among the U.S. EPA's List 2 chemicals for Tier 1 endocrine screening subject to the agency's two-tiered Endocrine Disruptor Screening Program (EDSP). Both U.S. EPA and OECD guidelines require a Weight of Evidence (WoE) to evaluate a chemical's potential for disrupting the endocrine system. Styrene was evaluated for its potential to disrupt estrogen, androgen, thyroid, and steroidogenic (EATS) pathways using a rigorous WoE methodology that included problem formulation, systematic literature search and selection, data quality evaluation, relevance weighting of endpoint data, and application of specific interpretive criteria. Sufficient data were available to assess the endocrine disruptive potential of styrene based on endpoints that would respond to EATS modes of action in some Tier 1-type and many Tier 2-type reproductive, developmental, and repeat dose toxicity studies. Responses to styrene were inconsistent with patterns of responses expected for chemicals and hormones known to operate via EATS MoAs, and thus, styrene cannot be deemed an endocrine disruptor, a potential endocrine disruptor, or to exhibit endocrine disruptive properties. Because Tier 1 EDSP screening results would trigger Tier 2 studies, like those evaluated here, subjecting styrene to further endocrine screening would produce no additional useful information and would be unjustified from animal welfare perspectives.
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Affiliation(s)
- Christopher J Borgert
- Applied Pharmacology and Toxicology Inc, Gainesville, FL, USA
- Department of Physiological Sciences, University of Florida College of Veterinary Medicine, Gainesville, FL, USA
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Banton MI, Bus JS, Collins JJ, Delzell E, Gelbke HP, Kester JE, Moore MM, Waites R, Sarang SS. Evaluation of potential health effects associated with occupational and environmental exposure to styrene - an update. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2019; 22:1-130. [PMID: 31284836 DOI: 10.1080/10937404.2019.1633718] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The potential chronic health risks of occupational and environmental exposure to styrene were evaluated to update health hazard and exposure information developed since the Harvard Center for Risk Analysis risk assessment for styrene was performed in 2002. The updated hazard assessment of styrene's health effects indicates human cancers and ototoxicity remain potential concerns. However, mechanistic research on mouse lung tumors demonstrates these tumors are mouse-specific and of low relevance to human cancer risk. The updated toxicity database supports toxicity reference levels of 20 ppm (equates to 400 mg urinary metabolites mandelic acid + phenylglyoxylic acid/g creatinine) for worker inhalation exposure and 3.7 ppm and 2.5 mg/kg bw/day, respectively, for general population inhalation and oral exposure. No cancer risk value estimates are proposed given the established lack of relevance of mouse lung tumors and inconsistent epidemiology evidence. The updated exposure assessment supports inhalation and ingestion routes as important. The updated risk assessment found estimated risks within acceptable ranges for all age groups of the general population and workers with occupational exposures in non-fiber-reinforced polymer composites industries and fiber-reinforced polymer composites (FRP) workers using closed-mold operations or open-mold operations with respiratory protection. Only FRP workers using open-mold operations not using respiratory protection have risk exceedances for styrene and should be considered for risk management measures. In addition, given the reported interaction of styrene exposure with noise, noise reduction to sustain levels below 85 dB(A) needs be in place.
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Affiliation(s)
- M I Banton
- a Gorge View Consulting LLC , Hood River , OR , USA
| | - J S Bus
- b Health Sciences , Exponent , Midland , MI , USA
| | - J J Collins
- c Health Sciences , Saginaw Valley State University , Saginaw , MI , USA
| | - E Delzell
- d Private consultant , Birmingham , AL , USA
| | | | - J E Kester
- f Kester Consulting LLC , Wentzville , MO , USA
| | | | - R Waites
- h Sabic , Innovative Plastics US LLC , Mount Vernon , IN , USA
| | - S S Sarang
- i Shell Health , Shell International , Houston , TX , USA
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Bang DY, Kyung M, Kim MJ, Jung BY, Cho MC, Choi SM, Kim YW, Lim SK, Lim DS, Won AJ, Kwack SJ, Lee Y, Kim HS, Lee BM. Human Risk Assessment of Endocrine-Disrupting Chemicals Derived from Plastic Food Containers. Compr Rev Food Sci Food Saf 2012. [DOI: 10.1111/j.1541-4337.2012.00197.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Luderer U, Collins TFX, Daston GP, Fischer LJ, Gray RH, Mirer FE, Olshan AF, Setzer RW, Treinen KA, Vermeulen R. NTP-CERHR Expert Panel Report on the reproductive and developmental toxicity of styrene. ACTA ACUST UNITED AC 2006; 77:110-93. [PMID: 16345075 DOI: 10.1002/bdrb.20061] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Brown NA, Lamb JC, Brown SM, Neal BH. A review of the developmental and reproductive toxicity of styrene. Regul Toxicol Pharmacol 2000; 32:228-47. [PMID: 11162717 DOI: 10.1006/rtph.2000.1406] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The reproductive and developmental toxicity of styrene has been studied in animals and humans. The animal studies on styrene have diverse study designs and conclusions. Developmental or reproductive toxicity studies have been conducted in rats, mice, rabbits, and hamsters. In most cases, high doses are required to elicit effects, and the effects are not unique to reproduction or development. In a number of the reports, either the experimental designs are limited or the descriptions of the designs and the endpoints measured are insufficient to draw conclusions about the toxicity of styrene. The more complete and better-reported studies show that styrene does not cause developmental toxicity at dose levels that are not maternally toxic. Some neurochemical or neurobehavioral effects have been reported at high exposures. Styrene does not affect fertility or reproductive function. Considerable animal toxicity data on styrene support the conclusion that styrene is neither an endocrine-active substance nor an endocrine disrupter. Human studies often suffer from either inadequate exposure data or exposure to a wide variety of materials, so that attribution of effects to styrene exposure is impossible. Furthermore, investigators often have failed to account for other exposures in the workplace or for other potentially confounding factors in their studies. Menstrual cycle irregularities and congenital abnormalities were initially reported; however, the better and more recent reports do not show that styrene causes developmental or reproductive effects in humans. Human studies also support the conclusion that styrene is not an endocrine disrupter. Although some study authors have concluded that styrene is either a human or an animal reproductive or developmental toxicant, careful review demonstrates that such conclusions are not justified.
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Affiliation(s)
- N A Brown
- MRC Experimental Embryology and Teratology Unit, St. George's Hospital Medical School, University of London, SW17 0RE, United Kingdom
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Katakura Y, Kishi R, Ikeda T, Miyake H. Effects of prenatal exposure to styrene on neurochemical levels in rat brain. Toxicol Lett 1999; 105:239-49. [PMID: 10355545 DOI: 10.1016/s0378-4274(99)00006-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Styrene was evaluated to determine its neurochemical effects in the offspring of rats exposed during the gestation period. Maternal Wistar rats were exposed to 0, 50 or 300 ppm styrene during gestation days 6 to 20 and the neurochemical effects on their offspring were compared with their pair-feeding and ad lib. feeding controls. The cerebrum weights at birth on day 0 were significantly lower than those for an ad lib. feeding control group. Neurotransmitter analyses showed decreases of neuroamines, especially 5-hydroxytryptamine and homovanillic acid in the cerebrum of newborn offspring of dams receiving a 300 ppm styrene exposure compared with the ad lib. fed control group and homovanillic acid was also decreased compared to the pair-feeding control. On postnatal day 21, the styrene-exposure pups showed a significant decrease of 5-hydroxyindoleacetic acid in the frontal neocortex compared with the ad lib. control group. In the hippocampus a significant decrease of 5-hydroxyindoleacetic acid was observed compared with both control groups. Moreover, the ratio of 5-HIAA/5-HT in the hippocampus was significantly decreased among the styrene-exposure groups. The 50 ppm styrene exposed group induced increase of concentrations of 5-hydroxytryptamine in the striatum. These results suggest that prenatal styrene exposure affects the developing fetal brain in terms of a few signs of neurochemical alteration.
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Affiliation(s)
- Y Katakura
- Department of Public Health, Sapporo Medical University, Japan.
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Kishi R, Chen BQ, Katakura Y, Ikeda T, Miyake H. Effect of prenatal exposure to styrene on the neurobehavioral development, activity, motor coordination, and learning behavior of rats. Neurotoxicol Teratol 1995; 17:121-30. [PMID: 7760773 DOI: 10.1016/0892-0362(94)00060-q] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Maternal Wistar rats were exposed via inhalation to 0, 50, or 300 ppm styrene for 6 h/day during gestation days 7 to 21, and offspring were subsequently evaluated in several neurobehavioral tests. Preliminary results with a small number of litters revealed significant dose-dependent effects in tests performed prior to weaning (surface righting, pivoting locomotion, and bar holding), as well as in tests performed after weaning (motor coordination, open-field behavior, and motor activity). Exposure to low concentrations of styrene (50 ppm) caused disturbances in motor coordination in addition to delaying some motor and reflex developments. Large doses (300 ppm) led to changes in open-field behavior and increases in spontaneous activity in addition to the delay in neurobehavioral developments. Exposure of dams to styrene did not clearly affect the learning behavior of the offspring. It was also observed that age played a role in the differences in styrene's effects on neurobehavioral function. Only subtle effects were found in both open-field behavior and motor-coordination function when compared with control rats at 120 days of age. These results suggest that the functional neurobehavioral development of progeny of dams exposed to styrene (or other solvents) should be further investigated.
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Affiliation(s)
- R Kishi
- Department of Public Health, Sapporo Medical College, Japan
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Kishi R, Katakura Y, Ikeda T, Chen BQ, Miyake H. Neurochemical effects in rats following gestational exposure to styrene. Toxicol Lett 1992; 63:141-6. [PMID: 1360716 DOI: 10.1016/0378-4274(92)90005-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Styrene was evaluated for the reproductive effects of pregnant rats and the neurochemical effects in the offspring of rats exposed during gestation. Pregnant Wistar rats were exposed to 0, 50, or 300 ppm styrene for 6 h/day during days 7 to 21 of gestation. No significant differences in the number of offspring delivered were observed between the exposed and control groups. Body weights at 1 day of age of the offspring whose mothers were exposed to styrene were significantly lower than those of the control group. Although, there were neither statistically significant differences of protein contents nor brain weights among styrene-exposed and their control offsprings of rats, analyses of neurotransmitter studies showed dose-dependent decreases of neuroamines, especially 5-HT (serotonin) and its metabolite 5HIAA (5-hydroxyindoleacetic acid) in the newborn offspring of styrene-exposed rats. The results suggest that gestational exposure to styrene at these concentrations does not produce apparent reproductive toxicity but affects the body weight of pups and causes lowering of the neurotransmitter levels in the brain.
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Affiliation(s)
- R Kishi
- Department of Public Health, Sapporo Medical College, Japan
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Windham GC, Shusterman D, Swan SH, Fenster L, Eskenazi B. Exposure to organic solvents and adverse pregnancy outcome. Am J Ind Med 1991; 20:241-59. [PMID: 1951371 DOI: 10.1002/ajim.4700200210] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In a large case-control study (n = 1,926) of spontaneous abortion (SAB), exposure to solvents was ascertained by a telephone interview that asked about occupational use of 18 specific solvents or products, as well as an open-ended "other" solvent category. The adjusted odds ratio for use of any solvent was 1.1 (0.8, 1.5). Solvents for which at least a doubled crude risk of SAB was found included perchlorethylene (OR = 4.7, 95% CI = 1.1, 21.1), trichloroethylene (OR = 3.1, CI = 0.9, 10.4), and paint thinners (OR = 2.3, CI = 1.0, 5.1). Comparing exposure greater than 10 hours per week versus less did not show consistent dose-response effects. By solvent class, an association was seen with aliphatic solvents (adjusted OR = 1.8, 95% CI = 1.1, 3.0), but there was no dose-response effect by hours of use. Household use of solvent-containing products was generally not strongly associated with SAB, nor did it appear to confound the association seen with occupational use. From this and other studies, occupational exposure to at least some solvents appears associated with SAB. The associations of solvent exposure and fetal growth among liveborn offspring of controls was also examined.
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Affiliation(s)
- G C Windham
- Special Epidemiological Studies Program, Department of Health Services, Berkeley, CA 94704
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Affiliation(s)
- N A Brown
- MRC Experimental Embryology and Teratology Unit, St. George's Hospital Medical School, University of London, U.K
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Abstract
Styrene is used in the production of plastics and resins, which include polystyrene resins, acrylonitrile-butadiene-styrene resins, styrene-acrylonitrile resins, styrene-butadiene copolymer resins, styrene-butadiene rubber, and unsaturated polyester resins. In 1985, styrene ranked in the top ten of synthetic organic chemicals produced in the U.S. This review focuses on various aspects of styrene toxicology including acute and chronic toxicity, carcinogenicity, genotoxicity, pharmacokinetics, effects on hepatic and extrahepatic xenobiotic-metabolizing enzymes, pharmacokinetic modeling, and covalent interactions with macromolecules. There appear to be many similarities between the toxicity and metabolism of styrene in rodents and humans. Needed areas of future research on styrene include studies on the molecular dosimetry of styrene in terms of both hemoglobin and DNA adducts. The results of such research should improve our ability to assess the relationship between exposure to styrene and surrogate measures of "effective dose", thereby improving our ability to estimate the effects of low-level human exposures.
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Affiliation(s)
- J A Bond
- Inhalation Toxicology Research Institute, Lovelace Biomedical and Environmental Research Institute, Albuquerque, New Mexico
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Khera KS. Maternal toxicity: a possible etiological factor in embryo-fetal deaths and fetal malformations of rodent-rabbit species. TERATOLOGY 1985; 31:129-53. [PMID: 3983854 DOI: 10.1002/tera.1420310115] [Citation(s) in RCA: 158] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Data from animal teratology studies were surveyed to determine whether embryo-fetal mortality and fetal malformations result from a primary action of the agent on the conceptus or if they are secondary to maternal toxicity--a consequence of administration with high dose levels of test chemicals. A fairly strong association between embryo-fetal mortality and maternal toxicity was revealed by analysis of data from hamsters, mice, rats, and rabbits in 234 studies of chemical and physical agents, of which 83 were conducted at both maternotoxic and nonmaternotoxic doses, 94 only at maternotoxic doses, and 49 at nonmaternotoxic doses. In the above studies, only nine chemicals (four each in hamsters and rabbits and one in rats) were reported to induce embryo-fetal deaths at apparently nonmaternotoxic doses. These findings tend to suggest a contributory role for maternal toxicity in the induction of embryo-fetal deaths. The previously reported hypothesis that certain fetal defects in mice may perhaps be caused by maternal toxicity was also found to be true in a review of data on hamsters, rats, and rabbits. Salient maternal toxicity-associated fetal malformations were exencephaly, encephalocele, micro- or anophalmia, and fused ribs in hamsters and defective (fused, missing, or extra) ribs, vertebrae, and sternebrae, ex-, an-, or microphthalmia, and cleft palate in rats and rabbits. These malformations occurred at low frequencies, generally with no readily apparent dose-response relationship. Presumptive evidence indicates that embryo-fetal deaths, and the above-mentioned fetal malformations in experimental animals, which in published literature are presently attributed to chemical induction for a large number of chemicals, may be a consequence of maternal toxicity per se.
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Romano M, Gazzotti G, Clos V, Assael BM, Facino RM, Salmona M. Perinatal development of styrene monooxygenase and epoxide hydrolase in rat liver microsomes and nuclei. Chem Biol Interact 1983; 47:213-22. [PMID: 6652809 DOI: 10.1016/0009-2797(83)90158-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Nuclear enzymes were found to develop earlier than the corresponding microsomal activities. In fact styrene monooxygenase enzymatic activity at 18 days gestational age reached about half the values of adult animals, whereas fetal microsomal activity was only about 1/20 the adult level at the same age. In microsomes and nuclei the ontogenic development of epoxide hydrolase is slightly slower than styrene monooxygenase. This suggests that fetuses and newborn animals are exposed to higher risk of accumulation of styrene-7,8-oxide, a toxic and possibly teratogenic product of styrene monooxygenase.
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Vainio H, Norppa H, Hemminki K, Sorsa M. Metabolism and genotoxicity of styrene. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1982; 136 Pt A:257-74. [PMID: 6178266 DOI: 10.1007/978-1-4757-0674-1_15] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
An overview on the metabolism and genotoxicity of styrene is given in this article. The mutagenic potency of styrene has been confirmed in a number of test systems providing the metabolic activation of styrene. Styrene is converted to styrene-7,8-oxide as catalyzed by cytochrome P-450 cored enzyme complex. Styrene-7,8-oxide is mutagenic in prokaryotic and eukaryotic test systems without metabolic activation. It reacts with nucleic acid bases, especially with deoxyguanosine producing 7-alkylguanine and deoxycytidine producing N-3 alkylcytosine. Quite recently, styrene-7,8-oxide has been found to be a potent carcinogen in rats. In human whole blood cultures, styrene is metabolized into styrene-7,8-oxide. Styrene is able to induce both SCEs and chromosomal aberrations in cultured lymphocytes. The clastogenic action of styrene can be explained by the metabolism of styrene into styrene-7,8-oxide in cultured human blood cells. Although also an arene oxide, styrene-3,4-oxide, has been suggested in the biotransformation of styrene, the evidence so far supports the view that the vinyl group oxidation and oxirane formation plays a predominant role in the genotoxicity of styrene.
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Abstract
Literature was surveyed concerning the teratological testing of chemicals, to which large numbers of workers are occupationally exposed. They include metals, plastics monomers and additives, solvents, and other organic chemicals. The effective doses used in the studies were compared to the potential exposures in the occupational environment as regulated by hygienic standards. In light of the animal experiments, the TLVs for some organic chemicals, particularly for acrylonitrile, methacrylate esters, styrene, carbon disulfide, chloroform, methylene chloride, toluene and xylene, appeared too high to provide absolute safety for pregnant workers. The mechanisms of teratogenesis and the validity of the animal experiments were also considered.
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