Bisphenol S

From Wikipedia, the free encyclopedia
Bisphenol S
Bisphenol S
Bisphenol S 3D BS
Names
Preferred IUPAC name
4,4′-Sulfonyldiphenol
Other names
BPS, 4,4′-sulfonylbisphenol,
Bis(4-hydroxyphenyl)sulfone
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.001.137 Edit this at Wikidata
EC Number
  • 201-250-5
KEGG
UNII
  • InChI=1S/C12H10O4S/c13-9-1-5-11(6-2-9)17(15,16)12-7-3-10(14)4-8-12/h1-8,13-14H checkY
    Key: VPWNQTHUCYMVMZ-UHFFFAOYSA-N checkY
  • InChI=1/C12H10O4S/c13-9-1-5-11(6-2-9)17(15,16)12-7-3-10(14)4-8-12/h1-8,13-14H
    Key: VPWNQTHUCYMVMZ-UHFFFAOYAO
  • O=S(=O)(c1ccc(O)cc1)c2ccc(O)cc2
  • c1cc(ccc1O)S(=O)(=O)c2ccc(cc2)O
Properties
C12H10O4S
Molar mass 250.27 g·mol−1
Appearance White colorless solid; forms needle shaped crystals in water
Density 1.3663 g/cm3
Melting point 245 to 250 °C (473 to 482 °F; 518 to 523 K)[2]
1100 mg/L[1]
Solubility Soluble in ethanol
Hazards
GHS labelling:
GHS07: Exclamation markGHS08: Health hazard
Warning
H319, H361
P201, P202, P264, P280, P281, P305+P351+P338, P308+P313, P337+P313, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Bisphenol S (BPS) is an organic compound with the formula (HOC6H4)2SO2. It has two phenol functional groups on either side of a sulfonyl group. It is commonly used in curing fast-drying epoxy resin adhesives. It is classified as a bisphenol, and a close molecular analog of bisphenol A (BPA). BPS differentiates from BPA by possessing a sulfone group (SO2) as the central linker of the molecule instead of a dimethylmethylene group (C(CH3)2), which is the case of bisphenol A.

Use[edit]

BPA Free Plastic

BPS is used in curing fast-drying epoxy glues and as a corrosion inhibitor. It is also commonly used as a reactant in polymer reactions.

BPS has become increasingly common as a building block in polyethersulfone and some epoxies, following the public awareness that BPA has estrogen-mimicking properties, and widespread-belief that enough of it remains in the products to be dangerous. However, BPS may have comparable estrogenic effects to BPA.[3] BPS is now used to a variety of common consumer products.[4][5] In some cases, BPS is used where the legal prohibition on BPA allows products (esp. plastic containers) containing BPS to be labelled "BPA free".[6] BPS also has the advantage of being more stable to heat and light than BPA.[7]

To comply with restrictions and regulations on BPA due to its confirmed toxicity, manufacturers are gradually replacing BPA with other related compounds, mainly bisphenol S, as substitutes in industrial applications.[8]

BPS is also used as an anticorrosive agent in epoxy glues. Chemically, BPS is being used as a reagent in polymer reactions. BPS has also been reported to occur in canned foodstuffs, such as tin cans.[9]

In a 2015 study analyzing BPS in a variety of paper products worldwide, BPS was found in 100% of tickets, mailing envelopes, airplane boarding passes, and airplane luggage tags. In this study, very high concentrations of BPS were detected in thermal receipt samples collected from cities in the United States, Japan, Korea, and Vietnam. The BPS concentrations were large but varied greatly, from a few tens of nanograms per gram to several milligrams per gram. Nevertheless, concentrations of BPS used in thermal paper are usually lower compared to those of BPA.[10] Finally, BPS can get into the human body through dermal absorption from handling banknotes.[4]

Health effects[edit]

Cardiac effects[edit]

Although there is no direct link established between BPS and cardiac disease, it is thought that BPS may operate by a similar mechanism to BPA and could cause cardiac toxicity.[11] In animal studies, BPS has been shown to hinder MI recovery, induce cardiac arrhythmias and cause cardiac developmental deformities. Rats exposed to high doses of BPS were reported to have increased risk of atherosclerosis (a significant risk factor in cardiac disease) due to BPS inducing synthesis of cholesterol in peripheral tissues.[11]

Neurobehavioral effects[edit]

BPS has the potential to have an effect on a wide range of neurological functions. A recent study showed that exposure to BPS during pregnancy may disrupt thyroid hormone levels. These are important in foetal neurodevelopment and prenatal exposure to BPS has been linked to impaired psychomotor development in children. In a study using human embryonic stem cells, BPS was shown to cause a reduction in length of neurites in neuron-like cells. This disruption could lead to neurobehavioral problems such as ASD.[12]

The mechanism of the neurological impact of BPS is thought to be related to its oestrogenic effect which can interfere in the levels and action of thyroid hormone, which is essential for normal development of the nervous system; it regulates migration and differentiation of neural cells, synaptogenesis and myelination.[12]

Effects on obesity[edit]

It has been proposed that BPS has the potential to affect body weight, and several studies have found a correlation between exposure to bisphenols and increased body weight.[13] This is thought to be due to an accumulation of lipids in adipocytes i.e. a build-up of fat in fat cells.[13] It has also been suggested that BPS leads to the formation of new adipocytes as exposure to it increases the expression of related markers.[13] A correlation between exposure to BPS before birth and being overweight has been found in mice, although this was only found when they were also fed a high fat diet.[13]

The pathway through which BPS acts on cells to increase body weight is suggested to be different to the pathway through which BPA acts, even though they have very similar chemical structures.[13]

Only one study has demonstrated a decrease in body weight after BPS exposure, and the affected mice quickly regained the weight they had lost.[13]

Other metabolic effects[edit]

BPS levels in the human body can be measured in the urine. In one study of children, there was a significant correlation between urinary levels of BPS and insulin resistance, abnormal kidney function and abnormal vascular function.[13]

It has been suggested that there is a link between gestational diabetes mellitus and urinary BPS.[13] Therefore, exposure to BPS may be a risk factor for developing the condition.[13]

Effects on skeletal development[edit]

The effect of long term exposure to BPS is an enrichment of osteoclast differentiation and enhanced development of the embryonic skeletal system.[14]

Effects on early development[edit]

BPS, like BPA, can cross the placenta in sheep and alter the endocrine functionality of the placenta. It does this by reducing the maternal serum concentration of trophoblastic proteins. BPS shows almost identical effects on the placenta as BPA, with both BPS and BPS altering almost identical sets of genes.[15]

Fetal exposure to BPS through the placenta, during a critical period, can have negative effects on the developmental programming of the fetus. BPS exposure in the zebrafish model affected development of the hypothalamus and resulted in hyperactive behaviour.

Studies in the Mouse model have shown that exposure to BPS significantly reduced the secretion of testosterone within the mouse fetal testes, with exposure to BPS in female mice also causing a significant fall in egg number, whilst also negatively affecting the quality of oocytes.[15]

Zebrafish and humans share 70% of the same genes that are expressed during development therefore, they are a useful model organism to understand the effects of BPS.[16] Studies in the Zebrafish model have shown that parental exposure to BPS causes disrupted thyroid hormone levels in both the parental generation and F1 generation. Fetal exposure to BPS through the placenta, during a critical period, can have negative effects on the developmental programming of the fetus. Additionally, there is evidence to suggest that embryos with high levels of BPS exhibit teratogenic effects of vital organs such as the heart and liver. Additionally, BPS inhibits the expression of genes within the liver used for the metabolism thus leading to increased stress of the liver through the zebrafish life.[17] Adult zebrafish that are exposed to low levels of BPS during development display hyperactivity due to an exponential increase in neural activity within the hypothalamus.[18]

It is not clear the mechanism of BPS's effect on thyroid hormone levels after human exposure.

Effects on reproductive health[edit]

The endocrine disrupting nature of BPS has encouraged investigations into its affinity to estrogenic receptors, showing BPS to be a weak agonist; similar in potency to BPA, which it has come to substitute. Select studies show BPS to be capable of mimicking estradiol, and sometimes being more effective.[19] The estrogenic activity of BPS has been demonstrated through in vivo rodent studies, inducing growth of the womb, with a range of dosages.

These are pathways necessary for cell function, cell cycle regulation, and neuroendocrine induced behaviours which are important for reproduction. BPS has shown to both disrupt signalling and damage DNA. Androgenic and antiandrogenic activity have also been confirmed by BPS disrupting function of the androgen receptors.[20] Studies on zebrafish have shown decreased egg quality, reduced sperm count, an increased frequency of embryo abnormalities, as well as changes in the mass of gonads;[19] suggesting that BPS is a reproductive toxin for both sexes.

The use of Bisphenol-A in manufacturing of household products has been reduced due to its effects as an endocrine disruptor, with research suggesting a disposition to greater deleterious effects to women as compared to men.[21] Research has suggested that BPA and it's cousins (BPS,BPF, etc.) have sex dependent effects on development.[22] Male zebrafish exposed to BPS indicated a significant increase in estrogen levels and a decrease in testosterone levels. The decrease in testosterone when exposed to BPS was found to be 200 times more than the decrease in testosterone by BPA.[23] There are increased levels of mRNA transcription of the aromatase gene and increased levels of mRNA transcription of GnRH genes with decreased levels of follicle stimulating hormone and luteinizing hormone.[24][25]

Bisphenol-S concentrations within populations[edit]

A relationship to higher BPS concentrations is linked to individuals within certain socio-economic classes hence placing those individuals at greater risk of possible deleterious effects. Individuals with an annual income of less than $20,000 were found to have the highest concentrations of bisphenol and individuals with an annual income of $75,000 or more to have the lowest concentrations, suggesting a linear relationship between bodily concentrations of BPS and income.[26] Black women had the highest concentrations of BPS with levels 93% higher than those of white women.[27]

Environmental considerations[edit]

Recent work suggests that, like BPA, BPS also has endocrine disrupting properties.[28][29] What makes BPS, and BPA, endocrine disruptors is the presence of the hydroxy group on the benzene ring. This phenol moiety allows BPA and BPS to mimic estradiol. In a study of human urine, BPS was found in 81% of the samples tested. This percentage is comparable to BPA which was found in 95% of urine samples.[30] Another study done on thermal receipt paper shows that 88% of human exposure to BPS is through receipts.[31]

The recycling of thermal paper can introduce BPS into the cycle of paper production and cause BPS contamination of other types of paper products.[32] A recent study showed presence of BPS in more than 70% of the household waste paper samples, potentially indicating spreading of BPS contamination through paper recycling.[10]

BPS is more resistant to environmental degradation than BPA, and although not persistent cannot be characterised as readily biodegradable.[10][33]

History[edit]

BPS was first made in 1869 as a dye[34] and is currently common in everyday consumer products. BPS is an analog of BPA that has replaced BPA in a variety of ways, being present in thermal receipt paper, plastics, and indoor dust.[28] After health concerns associated with bisphenol A grew in 2012, BPS began to be used as a replacement.[35]

Regulation[edit]

In the US it is difficult for consumers to determine if a product contains BPS due to limited labelling regulations.[36] In January 2023 the European Chemicals Agency added bisphenol S to the candidate list for substance of very high concern designation, while it is investigated for reproductive toxicity and endocrine disruption.[37]

Synthesis[edit]

Bisphenol S is prepared by the reaction of two equivalents of phenol with one equivalent of sulfuric acid or oleum.[38]

2 C6H5OH + H2SO4 → (C6H4OH)2SO2 + 2 H2O
2 C6H5OH + SO3 → (C6H4OH)2SO2 + H2O

This reaction can also produce 2,4'-sulfonyldiphenol, a common isomeric complication in electrophilic aromatic substitution reactions.

Chemical reaction to bisphenol S
Chemical reaction to bisphenol S

See also[edit]

References[edit]

  1. ^ Pivnenko K, Pedersen GA, Eriksson E, Astrup TF (October 2015). "Bisphenol A and its structural analogues in household waste paper" (PDF). Waste Management. 44: 39–47. Bibcode:2015WaMan..44...39P. doi:10.1016/j.wasman.2015.07.017. PMID 26194879. S2CID 217938141.
  2. ^ "4,4′-Sulfonyldiphenol". Retrieved 4 February 2016.
  3. ^ Grignard E, Lapenna S, Bremer S (August 2012). "Weak estrogenic transcriptional activities of Bisphenol A and Bisphenol S". Toxicology in Vitro. 26 (5): 727–31. doi:10.1016/j.tiv.2012.03.013. PMID 22507746.
  4. ^ a b Liao C, Liu F, Kannan K (June 2012). "Bisphenol s, a new bisphenol analogue, in paper products and currency bills and its association with bisphenol a residues". Environmental Science & Technology. 46 (12): 6515–22. Bibcode:2012EnST...46.6515L. doi:10.1021/es300876n. PMID 22591511.
  5. ^ Liao C, Liu F, Guo Y, Moon HB, Nakata H, Wu Q, Kannan K (August 2012). "Occurrence of eight bisphenol analogues in indoor dust from the United States and several Asian countries: implications for human exposure". Environmental Science & Technology. 46 (16): 9138–45. Bibcode:2012EnST...46.9138L. doi:10.1021/es302004w. PMID 22784190.
  6. ^ Jenna Bilbrey (Aug 11, 2014). "BPA-Free Plastic Containers May Be Just as Hazardous". Scientific American.
  7. ^ Kuruto-Niwa R, Nozawa R, Miyakoshi T, Shiozawa T, Terao Y (January 2005). "Estrogenic activity of alkylphenols, bisphenol S, and their chlorinated derivatives using a GFP expression system". Environmental Toxicology and Pharmacology. 19 (1): 121–30. doi:10.1016/j.etap.2004.05.009. PMID 21783468.
  8. ^ Chen MY, Ike M, Fujita M (February 2002). "Acute toxicity, mutagenicity, and estrogenicity of bisphenol-A and other bisphenols". Environmental Toxicology. 17 (1): 80–6. Bibcode:2002EnTox..17...80C. doi:10.1002/tox.10035. PMID 11847978. S2CID 21979200.
  9. ^ Viñas P, Campillo N, Martínez-Castillo N, Hernández-Córdoba M (May 2010). "Comparison of two derivatization-based methods for solid-phase microextraction-gas chromatography-mass spectrometric determination of bisphenol A, bisphenol S and biphenol migrated from food cans". Analytical and Bioanalytical Chemistry. 397 (1): 115–125. doi:10.1007/s00216-010-3464-7. PMID 20127078. S2CID 11696149.
  10. ^ a b c Pivnenko K, Pedersen GA, Eriksson E, Astrup TF (October 2015). "Bisphenol A and its structural analogues in household waste paper" (PDF). Waste Management. 44: 39–47. Bibcode:2015WaMan..44...39P. doi:10.1016/j.wasman.2015.07.017. PMID 26194879. S2CID 217938141.
  11. ^ a b Zhang YF, Shan C, Wang Y, Qian LL, Jia DD, Zhang YF, et al. (June 2020). "Cardiovascular toxicity and mechanism of bisphenol A and emerging risk of bisphenol S". The Science of the Total Environment. 723: 137952. Bibcode:2020ScTEn.723m7952Z. doi:10.1016/j.scitotenv.2020.137952. PMID 32213405. S2CID 214679291.
  12. ^ a b Naderi M, Kwong RW (September 2020). "A comprehensive review of the neurobehavioral effects of bisphenol S and the mechanisms of action: New insights from in vitro and in vivo models". Environment International. 145: 106078. doi:10.1016/j.envint.2020.106078. PMID 32911243.
  13. ^ a b c d e f g h i Thoene M, Dzika E, Gonkowski S, Wojtkiewicz J (February 2020). "Bisphenol S in Food Causes Hormonal and Obesogenic Effects Comparable to or Worse than Bisphenol A: A Literature Review". Nutrients. 12 (2): 532. doi:10.3390/nu12020532. PMC 7071457. PMID 32092919.
  14. ^ Chin KY, Pang KL, Mark-Lee WF (2018). "A Review on the Effects of Bisphenol A and Its Derivatives on Skeletal Health". International Journal of Medical Sciences. 15 (10): 1043–1050. doi:10.7150/ijms.25634. PMC 6036156. PMID 30013446.
  15. ^ a b Basak S, Das MK, Duttaroy AK (June 2020). "Plastics derived endocrine-disrupting compounds and their effects on early development". Birth Defects Research. 112 (17): 1308–1325. doi:10.1002/bdr2.1741. hdl:10852/82658. PMID 32476245.
  16. ^ Catron, Tara R.; Keely, Scott P.; Brinkman, Nichole E.; Zurlinden, Todd J.; Wood, Charles E.; Wright, Justin R.; Phelps, Drake; Wheaton, Emily; Kvasnicka, Allison; Gaballah, Shaza; Lamendella, Regina; Tal, Tamara (2019-02-01). "Host Developmental Toxicity of BPA and BPA Alternatives Is Inversely Related to Microbiota Disruption in Zebrafish". Toxicological Sciences. 167 (2): 468–483. doi:10.1093/toxsci/kfy261. ISSN 1096-0929. PMID 30321396.
  17. ^ Moreman, John; Lee, Okhyun; Trznadel, Maciej; David, Arthur; Kudoh, Tetsuhiro; Tyler, Charles R. (2017-11-07). "Acute Toxicity, Teratogenic, and Estrogenic Effects of Bisphenol A and Its Alternative Replacements Bisphenol S, Bisphenol F, and Bisphenol AF in Zebrafish Embryo-Larvae". Environmental Science & Technology. 51 (21): 12796–12805. Bibcode:2017EnST...5112796M. doi:10.1021/acs.est.7b03283. hdl:10871/38729. ISSN 0013-936X. PMID 29016128.
  18. ^ Kinch, Cassandra D.; Ibhazehiebo, Kingsley; Jeong, Joo-Hyun; Habibi, Hamid R.; Kurrasch, Deborah M. (2015-02-03). "Low-dose exposure to bisphenol A and replacement bisphenol S induces precocious hypothalamic neurogenesis in embryonic zebrafish". Proceedings of the National Academy of Sciences of the United States of America. 112 (5): 1475–1480. Bibcode:2015PNAS..112.1475K. doi:10.1073/pnas.1417731112. ISSN 1091-6490. PMC 4321238. PMID 25583509.
  19. ^ a b Žalmanová, T.; Hošková, K.; Nevoral, J.; Prokešová, Š.; Zámostná, K.; Kott, T.; Petr, J. (31 October 2016). "Article". Czech Journal of Animal Science. 61 (10): 433–449. doi:10.17221/81/2015-cjas.
  20. ^ Siracusa JS, Yin L, Measel E, Liang S, Yu X (August 2018). "Effects of bisphenol A and its analogs on reproductive health: A mini review". Reproductive Toxicology. 79: 96–123. doi:10.1016/j.reprotox.2018.06.005. PMC 6689411. PMID 29925041.
  21. ^ Vogel, Sarah A. (November 2009). "The Politics of Plastics: The Making and Unmaking of Bisphenol A "Safety"". American Journal of Public Health. 99 (S3): S559–S566. doi:10.2105/AJPH.2008.159228. ISSN 0090-0036. PMC 2774166. PMID 19890158.
  22. ^ Lee, Jiyun; Moon, Kyong Whan; Ji, Kyunghee (January 2021). "Systematic Review of Exposure to Bisphenol A Alternatives and Its Effects on Reproduction and Thyroid Endocrine System in Zebrafish". Applied Sciences. 11 (4): 1837. doi:10.3390/app11041837. ISSN 2076-3417.
  23. ^ Schally, A. V.; Arimura, A.; Kastin, A. J.; Matsuo, H.; Baba, Y.; Redding, T. W.; Nair, R. M. G.; Debeljuk, L.; White, W. F. (1971-09-10). "Gonadotropin-Releasing Hormone: One Polypeptide Regulates Secretion of Luteinizing and Follicle-Stimulating Hormones". Science. 173 (4001): 1036–1038. Bibcode:1971Sci...173.1036S. doi:10.1126/science.173.4001.1036. ISSN 0036-8075. PMID 4938639. S2CID 10052615.
  24. ^ Kallivretaki, Evangelia; Eggen, Rik; Neuhauss, Stephan; Alberti, Martin; Kausch, Ulf; Segner, Helmut (2006-01-01). "Aromatase in zebrafish: A potential target for endocrine disrupting chemicals". Marine Environmental Research. Pollutant Responses in Marine Organisms (PRIMO 13). 62: S187–S190. Bibcode:2006MarER..62S.187K. doi:10.1016/j.marenvres.2006.04.003. ISSN 0141-1136. PMID 16698076.
  25. ^ Qiu, Wenhui; Fang, Meijuan; Liu, Jingyu; Fu, Caixia; Zheng, Chunmiao; Chen, Bei; Wang, Ke-Jian (2019-05-15). "In vivo actions of Bisphenol F on the reproductive neuroendocrine system after long-term exposure in zebrafish". Science of the Total Environment. 665: 995–1002. Bibcode:2019ScTEn.665..995Q. doi:10.1016/j.scitotenv.2019.02.154. ISSN 0048-9697. PMID 30893755. S2CID 84844426.
  26. ^ Nelson, Jessica W.; Scammell, Madeleine Kangsen; Hatch, Elizabeth E.; Webster, Thomas F. (2012-03-06). "Social disparities in exposures to bisphenol A and polyfluoroalkyl chemicals: a cross-sectional study within NHANES 2003-2006". Environmental Health. 11 (1): 10. Bibcode:2012EnvHe..11...10N. doi:10.1186/1476-069X-11-10. ISSN 1476-069X. PMC 3312862. PMID 22394520. S2CID 9872387.
  27. ^ Nguyen, Vy Kim; Kahana, Adam; Heidt, Julien; Polemi, Katelyn; Kvasnicka, Jacob; Jolliet, Olivier; Colacino, Justin A. (April 2020). "A comprehensive analysis of racial disparities in chemical biomarker concentrations in United States women, 1999–2014". Environment International. 137: 105496. doi:10.1016/j.envint.2020.105496. PMC 7137529. PMID 32113086.
  28. ^ a b Mathew M, Sreedhanya S, Manoj P, Aravindakumar CT, Aravind UK (April 2014). "Exploring the interaction of bisphenol-S with serum albumins: a better or worse alternative for bisphenol a?". The Journal of Physical Chemistry B. 118 (14): 3832–43. doi:10.1021/jp500404u. PMID 24635450.
  29. ^ Horan TS, Pulcastro H, Lawson C, Gerona R, Martin S, Gieske MC, et al. (September 2018). "Replacement Bisphenols Adversely Affect Mouse Gametogenesis with Consequences for Subsequent Generations". Current Biology. 28 (18): 2948–2954.e3. doi:10.1016/j.cub.2018.06.070. PMC 6156992. PMID 30220498.
  30. ^ Calafat AM, Kuklenyik Z, Reidy JA, Caudill SP, Ekong J, Needham LL (April 2005). "Urinary concentrations of bisphenol A and 4-nonylphenol in a human reference population". Environmental Health Perspectives. 113 (4): 391–5. doi:10.1289/ehp.7534. PMC 1278476. PMID 15811827.
  31. ^ Konkel, Lindsey (2013). "EHP – Thermal Reaction: The Spread of Bisphenol S via Paper Products". Environmental Health Perspectives. 121 (3): A76. doi:10.1289/ehp.121-a76. PMC 3621184. PMID 23454568. Retrieved 4 February 2016.
  32. ^ European Commission-Joint Research Centre. European Union Risk Assessment Report, 4,4′-Isopropylidenediphenol (Bisphenol-A). 2008, available from http://ecb.jrc.ec.europa.eu/documents/ExistingChemicals/RISK_ASSESSMENT/ADDENDUM/bisphenola_add_[permanent dead link] 325.pdf
  33. ^ Ike M, Chen MY, Danzl E, Sei K, Fujita M (2006). "Biodegradation of a variety of bisphenols under aerobic and anaerobic conditions". Water Science and Technology. 53 (6): 153–9. doi:10.2166/wst.2006.189. PMID 16749452.
  34. ^ Glausiusz J (April 2014). "Toxicology: The plastics puzzle". Nature. 508 (7496). Nature Publishing Group: 306–8. Bibcode:2014Natur.508..306G. doi:10.1038/508306a. PMID 24740050.
  35. ^ Liao C, Liu F, Alomirah H, Loi VD, Mohd MA, Moon HB, et al. (June 2012). "Bisphenol S in urine from the United States and seven Asian countries: occurrence and human exposures". Environmental Science & Technology. 46 (12): 6860–6. Bibcode:2012EnST...46.6860L. doi:10.1021/es301334j. PMID 22620267.
  36. ^ Howard B. "Chemical in BPA-Free Products Linked to Irregular Heartbeats". National Geographic. Archived from the original on March 3, 2015. Retrieved 29 March 2015.
  37. ^ "Substance Information -4,4'-sulphonyldiphenol - ECHA". echa.europa.eu. European Chemicals Agency. Retrieved 16 February 2023.
  38. ^ METHOD OF PREPARATION OF 4,4′-DIHYDROXYDIPHENYLSULPHONE (Freepatentsonline).