Exposure monitoring and risk assessment of biphenyl in the workplace.

This study was performed to assess exposure to and the risk caused by biphenyl in the workplace. Biphenyl is widely used as a heat transfer medium and as an emulsifier and polish in industry. Vapor or high levels of dust inhalation and dermal exposure to biphenyl can cause eye inflammation, irritation of respiratory organs, and permanent lesions in the liver and nervous system. In this study, the workplace environment concentrations were assessed as central tendency exposure and reasonable maximum exposure and were shown to be 0.03 and 0.12 mg/m³, respectively. In addition, the carcinogenic risk of biphenyl as determined by risk assessment was 0.14 × 10⁻4 (central tendency exposure) and 0.56 × 10⁻4 (reasonable maximum exposure), which is below the acceptable risk value of 1.0 × 10⁻4. Furthermore, the central tendency exposure and reasonable maximum exposure hazard quotients were 0.01 and 0.06 for oral toxicity, 0.05 and 0.23 for inhalation toxicity, and 0.08 and 0.39 for reproduction toxicity, respectively, which are all lower than the acceptable hazard quotient of 1.0. Therefore, exposure to biphenyl was found to be safe in current workplace environments. Because occupational exposure limits are based on socioeconomic assessment, they are generally higher than true values seen in toxicity experiments. Based on the results of exposure monitoring of biphenyl, the current occupational exposure limits in Korea could be reviewed.

Comparison of properties of poly(vinyl alcohol) nanocomposites containing two different clays.

Morphologies, thermo-optical properties, and gas barriers of poly(vinyl alcohol) (PVA) hybrid films containing two different clays are compared. Saponite (SPT) and hydrophilic bentonite (BTT) were used as the reinforcing filler in the fabrication of PVA hybrid films, which were synthesized from aqueous solutions and were solvent-cast at room temperature under vacuum, yielding 20-31-µm-thick PVA hybrid films with varying clay contents. The addition of small amounts of clay is sufficient to improve the thermal properties and gas barriers of PVA hybrid films. Even polymers with a low clay content (3-10 wt%) were found to exhibit much higher transition temperature values than pure PVA. The addition of BTT was more effective than the addition of SPT for improving the thermal properties and gas barrier in the PVA matrix. The PVA hybrid films containing 5 wt% SPT were equibiaxially stretched, with stretching ratios ranging from 150% to 250%. Clay dispersion, morphology, optical transparency, and gas permeability were then examined as a function of the equibiaxial stretching ratio. PVA hybrid films with a stretching ratio of ≥ 150% displayed homogeneously dispersed clay within the polymer matrix and exfoliated nanocomposites.