Hazard assessment of tert-dodecanethiol
Kasey Mohan, Senior Toxicologist at Enhesa Sustainable Chemistry, confirms, with Enhesa’s own research, that a substance suspected of having reproductive and developmental toxicity does indeed have potential negative impacts.
At the SOT 2024 63rd Annual Meeting and ToxExpo in Salt Lake City (10-14 March), I had the opportunity to present my work on a recent chemical hazard assessment at a poster session. The hazard assessment was for tert-dodecanethiol, which is typically used as a chemical intermediate (a substance formed during a middle step of a chemical reaction) and as a chain transfer agent (used in polymerization reaction to initiate the transfer of a growing polymer chain to another molecule).
Tert-dodecanethiol was a good poster candidate due to some unique human health findings that were uncovered during the hazard assessment, specifically, concerns for reproductive and developmental toxicity. Additionally, three new studies had recently been published to address these concerns. (See the list of information reviewed below)
Hazard assessed, validating concerns
To briefly summarize the background for tert-dodecanethiol, a prior ECHA (European Chemicals Agency) dossier evaluation pointed out that two prior studies (inhalation route of exposure) had identified some reproductive and developmental toxicity concerns including increased post-implantation loss, reduced ovarian weight, and reduced fetal body weight. However, these 1983 studies did not adhere to the relevant testing guidelines, and therefore, ECHA requested new studies to be conducted to verify whether or not these effects were truly a concern. Since 2020, three new high-quality studies that were specifically designed to evaluate reproductive and developmental toxicity were released, but ECHA has not issued an updated decision yet in their dossier evaluation. This seemed like a good opportunity for Enhesa Sustainable Chemistry to independently review the results of these new studies and draw our own conclusion for the tert-dodecanethiol hazard assessment.
As it turned out, the prior concerns identified were validated, as the new studies highlighted several reproductive and developmental effects, many of which overlapped with findings from the previous studies. These effects included (but were not limited to) reduced fetal body weight (up to 10%), increased skeletal variations, reduced daily sperm production rate (up to 16%), increased pre-implantation loss, and reduced fertility index. The dose levels at which these findings were reported corresponded to moderate hazard scores for both the reproductive and developmental toxicity endpoints that are included in GHS+ chemical hazard assessments.
Tert-dodecanethiol received an overall hazard rating of Moderate, with the highest hazard scores being determined for Dermal Irritation (High) and Persistence (Very High).
Kasey Mohan, Senior Toxicologist at Enhesa Sustainable ChemistryComplete chemical checks
While tert-dodecanethiol’s reproductive and developmental effects were the main focus of this poster, I also included an overview, using the GHS+ traffic light visual approach, of the hazard scores determined for the remaining human health and environmental toxicity endpoints, as well as the overall hazard rating. Tert-dodecanethiol received an overall hazard rating of Moderate, with the highest hazard scores being determined for Dermal Irritation (High) and Persistence (Very High).
List of information reviewed
For this assessment, we reviewed publicly available information and conducted an independent analysis.
- OECD 443 (Study date 2021)
ECHA (European Chemicals Agency). 2024a. Toxicity to reproduction 001 Key Experimental Study. ECHA Dossier publication CAS RN 25103-58-6 (tert-dodecanethiol). View publication
- OECD 422 (Study date 2020)
ECHA (European Chemicals Agency). 2024b. Toxicity to reproduction 002 Supporting Experimental Study. ECHA Dossier publication CAS RN 25103-58-6 (tert-dodecanethiol). View publication
- OECD 414 Rabbits (Study date 2020)
ECHA (European Chemicals Agency). 2024c. Developmental toxicity/teratogenicity 001 Key Experimental Study. ECHA Dossier publication CAS RN 25103-58-6 (tert-dodecanethiol). View publication
- OECD 414 Mice (Study date 1983)
ECHA (European Chemicals Agency). 2024d. Developmental toxicity/teratogenicity 003 Key Experimental Study. ECHA Dossier publication CAS RN 25103-58-6 (tert-dodecanethiol). View publication
- OECD 414 Inhalation Rats (Study date 1983)
ECHA (European Chemicals Agency). 2024e. Developmental toxicity/teratogenicity 004 Key Experimental Study. ECHA Dossier publication CAS RN 25103-58-6 (tert-dodecanethiol). View publication
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