Vinyltrimethoxysilane (VTMS)

Abstract

Vinyltrimethoxysilane (VTMS) has been used in formulations as a coupling agent for plastic and wire cable pipes, a moisture scavenger in sealants, and a co-monomer in the preparation of latex dispersions. The amount of VTMS used in industrial products is ≤2%; there are no consumer uses of VTMS. In studies in experimental animals, VTMS showed a low acute toxicity via oral, dermal, and inhalation routes of exposure. VTMS is not a dermal or eye irritant. A weight of evidence assessment of four available dermal sensitization studies in guinea pigs supports the conclusion that VTMS is not a dermal sensitizer; however, based on one additional study that gave positive results, ECHA classified VTMS as Category 1B (may cause an allergic skin reaction). VTMS is not considered to be genotoxic based on results of in vitro and in vivo studies. In various experimental animal studies, VTMS has shown neither reproductive nor developmental effects. Short-term, oral administration of VTMS for 28 days in rats produced treatment-related effects in the urinary bladder and kidney. In a 14-week inhalation study in rats, VTMS exposure was associated with histopathological changes in the kidney and urinary bladder. However, an expert panel review of the urinary bladder and kidney observations concluded they were an adaptive response to physical or chemical irritant(s) in the urine. The NOAEC of 100 ppm (605 mg/m³) from the 14-week inhalation study was used as the point of departure for the health-based WEEL derivation. After adjusting to account for duration of exposure and interindividual variability, the 8-h TWA WEEL guideline of 10 ppm (60 mg/m³) is expected to provide a significant margin of safety against any potential adverse health effects in workers following long-term inhalation exposure to VTMS.