Occupational risk assessment of p-tert-butylphenol: toxicity reference values and worker exposure evaluation.

p-Tert-butylphenol (ptBP) is widely used in polymer resin synthesis and industrial applications, and workers are potentially exposed to it during manufacturing and handling. ptBP induces vitiligo and is associated with skin depigmentation and endocrine-disrupting effects mediated by oxidative stress. These toxicological concerns extend beyond local irritation to systemic health risks and underscore the need to establish scientifically derived reference values and occupational safety standards to protect workers. Key data was selected from animal and human biomonitoring studies. Reference values were derived for the dermal and inhalation routes using internationally accepted methodologies. Worker exposure was estimated by the ECETOC TRA model. Hazard quotients (HQs) were calculated by comparing the predicted exposure levels with derived reference values. Reference values were determined as 0.196 mg/kg bw/day for dermal exposure and 0.5 mg/m3 for inhalation. Predicted chronic dermal exposures ranged from 1.71E-03 to 6.86E-01 mg/kg bw/day, while inhalation exposures were between 1.50E-04 to 4.73E+00 mg/m3. The HQs exceeded one in several processes, particularly dermal exposure, with four processes being problematic even after accounting for workplace conditions. Inhalation risks are generally low because of the closed-system operations. This study provided a comprehensive evaluation of the occupational risks of ptBP and offers scientific evidence to support exposure limits and regulatory strategies.