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China Updates OELs Standard for Hazardous Agents in Workplace

NHC updated OELs and critical adverse health effects for benzene, and introduced trimethyltin chloride subject to biological monitoring.

On November 28, the National Health Commission of the People's Republic of China (NHC) released a notice to amend GBZ 2.1-2019 Occupational Exposure Limits for Hazardous Agents in the Workplace Part 1: Chemical Hazardous Agents. The amendment takes effect the same day it was released.

GBZ 2.1-2019 is a national standard that stipulates hygiene requirements, testing evaluation and control principles of occupational exposure to hazardous agents in the workplace. It set out occupational exposure limits (OELs) for 358 hazardous chemicals (Table 1), 49 kinds of dust (Table 2) and 3 biological agents (Table 3), and biological exposure limits (BELs) for 28 hazardous chemicals (Table 4).

Compared with GBZ 2.1-2019, the amendment revises OELs and critical adverse health effects for Benzene in Table 1 (highlighted in yellow) as:

No.Chemical nameCAS numberOELs (mg/m3)
Critical adverse health effectsRemark

Neurological damage, hematological toxicity

Skin1, G12


1. Chemical substance with the remark of “skin” is likely to be absorbed by humans through skin exposure.

2. International Agency for Research on Cancer (IARC) classifies chemicals that are definitely carcinogenic to humans as Group 1 (G1).

In addition, one chemical substance is added into Table 4:

No.Chemical nameBiological monitoring indicatorsBELsSampling time
Trimethyltin chloride (TMT)

Trimethyltin chloride urine

500 µg/g CrNo strict requirement
Trimethyltin chloride in blood

200 µg/L

No strict requirement
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