Issuance of the national technical regulation on Exposure Limits for 80 Workplace Chemicals

21/10/2026

On 9 October 2026, the Ministry of Health issued Circular No. 38/2026/TT-BYT, which promulgated QCVN 31:2026/BYT, the national technical regulation on permissible exposure limit values for 80 chemical agents in the workplace. The Circular takes effect on 9 April 2027 and directly affects businesses whose workers are exposed to chemicals in the course of their operations.

Key takeways

The regulation applies to state agencies that manage the working environment, organizations that conduct working environment monitoring, and any organization or individual whose activities generate chemical agents in the workplace. Table 1 lists the Vietnamese and English names, formula, molecular weight, CAS number and IARC group of each chemical, together with two types of limit value (in mg/m³):

Time-weighted average (TWA): the average concentration over an 8-hour shift and a 40-hour working week.
Short-term exposure limit (STEL): the average concentration over 15 minutes. Where no STEL is specified, concentrations above 3 times the TWA must not last longer than 30 minutes, and must never exceed 5 times the TWA at any time.

For example, inorganic mercury and its compounds have a TWA of 0.02 mg/m³ and a STEL of 0.1 mg/m³, while ethylene oxide has a TWA of 1.8 mg/m³ and is classified in IARC Group 1. The regulation also provides a ppm to mg/m³ conversion formula, TWA adjustment for exposure beyond 8 hours a day or 40 hours a week, the method for calculating actual shift exposure, measurement methods in Table 2 (NIOSH, OSHA, MDHS, etc.), and techniques for direct-reading electronic instruments in Annex I.

Responsibilities of the parties

Businesses (employers) whose workers are exposed to the chemicals in Table 1 must conduct periodic monitoring (frequency as set by Clause 2, Article 18 of the Law on Occupational Safety and Hygiene) and control harmful factors.

Recommendations for businesses

Review the chemicals used and the agents generated in production (including welding fumes and dust) to identify work positions within the scope of the 80 listed agents, prioritizing IARC Group 1 and 2A substances.
Before 9 April 2027, compare the latest monitoring results with the new TWA/STEL values to spot positions at risk of exceedance early, and update the monitoring plan, contracts with monitoring providers and sampling methods according to Table 2.
Chemical agents outside the list of 80 substances should still be reviewed under the regulations currently in force.