Exposure to the synthetic phenolic antioxidant 4,4′-thiobis (6-t-butyl-m-cresol) disrupts early development in the frog Silurana tropicalis

Many chemicals in commonly used household and industrial products are being released into the environment, yet their toxicity is poorly understood. The synthetic phenolic antioxidant, 4,4 '-thiobis(6-t-butyl-m-cresol) (CAS 96-69-5; TBBC) is present in many common products made of rubber and plastic. Yet, this phenolic antioxidant has not been tested for potential toxicity and developmental disruption in amphibians, a sensitive and susceptible class. We investigated whether acute and chronic exposure to TBBC would interfere with thyroid hormonedependent developmental processes in the frog Silurana tropicalis and thus affect its early life-stage development. We exposed S. tropicalis embryos at the Nieuwkoop-Faber (NF) 9-10 stage to TBBC at nominal concentrations (0, 25, 50, 75, 100, 200 and 400 mu g/L) to determine the 96h lethal concentrations and sublethal effects. We conducted a chronic exposure starting at stage NF47-48 to three sublethal TBBC nominal concentrations (0, 0.002, 0.1 and 5 mu g/L) for 48-52 days to evaluate effects on growth and metamorphosis. The 96h lethal and effective (malformations) TBBC concentrations (LC50 and EC50) were 70.5 and 76.5 mu g/L, respectively. Acute exposure to all TBBC concentrations affected S. tropicalis growth and was lethal at 200 and 400 mu g/L. Chronic exposure to sublethal TBBC concentrations reduced body size by 8% at 5 mu g/L and body mass by 17% at 0.002

Automated summary

Many chemicals in commonly used products are being released into the environment, yet their toxicity is poorly understood. This study found that the synthetic phenolic antioxidant TBBC has negative effects on the developmental processes of amphibians.