In which Felicia explains the many sources, the chemistry, and the toxicity of sulfites and sulfates. Sulfites are widespread in food, both processed and natural. They have been strongly linked to inflammatory bowel diseases by gut bacteria that use sulfate as an energy source. Sulfates are found in many personal care and household cleaning products. Felicia offers many suggestions on how to avoid sulfites and sulfates. It’s good for you and for the environment.

Sources

1. Deng, K., Wang, L., Nguyen, S. M., Shrubsole, M. J., Cai, Q., Lipworth, L., Gupta, D. K., Zheng, W., Shu, X.-O., and Yu, D. (2025) A dietary pattern promoting gut sulfur metabolism is associated with increased mortality and altered circulating metabolites in low-income American adults, eBioMedicine 115.10.1016/j.ebiom.2025.105690: 10.1016/j.ebiom.2025.105690
2. Dordevic, D., Capikova, J., Dordevic, S., Tremlová, B., Gajdács, M., and Kushkevych, I. (2023) Sulfur content in foods and beverages and its role in human and animal metabolism: A scoping review of recent studies, Heliyon9.10.1016/j.heliyon.2023.e15452: 10.1016/j.heliyon.2023.e15452
3. Owczarek, D., Rodacki, T., Domagała-Rodacka, R., Cibor, D., and Mach, T. (2016) Diet and nutritional factors in inflammatory bowel diseases, World Journal of Gastroenterology 22, 895-905.10.3748/wjg.v22.i3.895: 10.3748/wjg.v22.i3.895
4. Pfau, A., López-Cayuqueo, K. I., Scherer, N., Wuttke, M., Wernstedt, A., González Fassrainer, D., Smith, D. E. C., van de Kamp, J. M., Ziegeler, K., Eckardt, K.-U., Luft, F. C., Aronson, P. S., Köttgen, A., Jentsch, T. J., and Knauf, F. (2023) SLC26A1 is a major determinant of sulfate homeostasis in humans, The Journal of Clinical Investigation 133.10.1172/JCI161849: 10.1172/JCI161849

In which Felicia interviews Michiel Brouns of Brouns & Co., who got his start in restoring historical buildings. We talk all about the sustainability of all-natural boiled linseed oil paint: how it polymerizes, that it is derived from flax seeds, and how it is biodegradable in the environment, so it makes no toxic microplastics. The paint requires nothing to dilute it, no solvents, so it contains only trace natural volatile organic compounds (VOCs). The pigments are non-toxic minerals, oxides like iron and zinc. Even though the cost is higher per can of paint, you apply it in very thin coats and it soaks into the wood, protecting it for the long term, without trapping moisture that causes wood to rot when painted with modern synthetic polymer paint. Linseed paint has protected buildings for thousands of years, so it is really quite inexpensive in the long run. Host–Felicia Etzkorn, Professor Emerita of Chemistry at Virginia Tech, with music by Wendy Godley of The Kind.

References:

Linseed Paint &Oil – A Practical Guide to the Traditional Production and Application by Michiel Brouns, The Crowood Press © Michiel Brouns 2023

Brouns & Co. linseed oil paint, putty, etc: https://linseedpaint.com/

Le Tonkinois linseed oil marine varnish: https://www.le-tonkinois.com/home-en.html

In which Felicia explains the sustainability of some toothpaste ingredients. This is a partial list of ingredients, based mainly on two tubes of toothpaste in her bathroom, Sensodyne Pronamel Multi-Action and Burt's Bees Complete Multi-Care. The ingredients are classified by the function they serve in toothpaste: 1) active ingredients, 2) sticky stuff, 3) surfactants (detergents), 4) sweeteners, 5) whiteners, 6) minerals, and 7) flavors.

Sources include:

Wikipedia

PubChem

Sampaio, F.C.; Oliveira, A.F.B.d.; Fernandes, N.L.S.; Gentile, A.C.C.; Marinho, G.B.; B.necker, M.J.S.; Paschoal, M.A.B.; D’Alpino, P.H.P.; Vilhena, F.V. Silicon-, Silica-, and Silicate-Toothpastes for Remineralization and Repair of Teeth: A Scoping Review. Oral 2024, 4, 467–486. https://doi.org/10.3390/oral4040038

Kim, D., Seok, J.K., Kim, M. et al. Safety assessment of cocamidopropyl betaine, a cosmetic ingredient. Toxicol Res. 40, 361–375 (2024). https://doi.org/10.1007/s43188-024-00243-2

Rayssa Ferreira Zanatta, Daniele Mara da Silva Ávila, Karen Mayumi Miyamoto, Carlos Rocha Gomes Torres, Alessandra Bühler Borges; Influence of Surfactants and Fluoride against Enamel Erosion. Caries Res 11 January 2019; 53 (1): 1–9. https://doi.org/10.1159/000488207

Lai, C.; Nguyen, A.; Ye, L.; Hao, J.; Koo, H.; Mante, F.; Ozer, F. Antibacterial and Physical Properties of PVM/MA Copolymer- Incorporated Polymethyl Methacrylate as a Novel Antimicrobial Acrylic Resin Material. Molecules 2022, 27, 8848. https://doi.org/10.3390/molecules27248848

Söderling, E., Pienihäkkinen, K. Specific effects of xylitol chewing gum on mutans streptococci levels, plaque accumulation and caries occurrence: a systematic review.BMC Oral Health 25, 1275 (2025). https://doi.org/10.1186/s12903-025-06602-1

Boerner, L.K. What is dental enamel, and how does it protect your teeth? Chem Eng News Oct 19, 2020