China Occupational exposure limits for hazardous agents in the workplace-Biological Monitoring Indicator and Biological Limit Value

Chemical hazardous agents（GBZ 2.1‑2019）-Biological Monitoring Indicator and Biological Limit Value assess workers' internal dose exposure levels by measuring the concentrations of toxic substances or their metabolites in human biological materials (such as blood, urine, and exhaled breath). The standard specifies permissible limits (BEL) for each indicator and optimal sample collection timing, providing criteria for early detection of subclinical health impairment in workers.