OBJECTIVETo systematically compare occupational exposure limits (OELs) in GBZ 2.1 with the ones in TLV-CS of ACGIH on quantity, level, procedures of management etc.; to propose priority chemicals for establishing OELs and suggestions on the revisions of occupational health standards; to provide basic scientific evidence for the planning and development of occupational health standards.

METHODCompilation of a database on OELs in GBZ 2.1 and in TLV-CS of ACGIH according to types of exposure limits, and comparison of the data in the two systems on the values of exposure limits, quantitative descriptions of specific occupational hazards, legal status, TLV-CS setting up principles, basis, condition and procedures, key adverse effect, application of carcinogenicity/sensitization/skin notations, adjustment of OELs for unusual work schedules, the concept and application of combined effects, the concept and application of Excursion Limits, the identity of particles, and analysis of the comparison result.

RESULTS(1) There are 339 chemical substances included in GBZ 2.1 and 656 in TLV-CS in ACGIH. (2) The number of the chemical substances in GBZ 2.1 with specified OELs but not included in TLV-CS of ACGIH is 52; the chemical substances with OELs in TLV-CS of ACGIH but not in GBZ 2.1 are 371. (3) There are 260 chemical substances which have OELs in both GBZ 2.1 and ACGIH and with a total of 302 OELs, among them, 47 OELs are higher and 96 are lower in the GBZ 2.1 than the ones in TLV-CS of ACGIH, 81 of them are similar, and 77 are the same in the two. (4) Guidelines on notations of carcinogenicity, sensitization and skin in China need to be developed. (5) Guidelines for adjustment of OELs for unusual work schedules need to be adopted in China. (6) There is still a wide gap between OELs in GBZ 2.1 and in TLV-CS of ACGIH in many aspects. The management and approval procedures of China in setting up OELs are more bureaucratic, and the biological plausibility and feasibility aspects should be strengthened.

CONCLUSIONS(1) Evaluation guidelines on risk assessment on notations of carcinogenicity, sensitization and skin need to be formulated in China. (2) A priority list in setting up OELs in China needs to be determined. Priority needs to be given to review and revision of the OELs which are significantly different from the ones in TLV?CS of ACGIH but without support of adequate scientific evidence. Priority should also be given to chemical substances which have no OELs in GBZ 2.1 but have specific OELs in TLV-CS of ACGIH. (3) Periodic and systematic review and revision of the existing OELs should be conduced based on the state-of-the-art scientific data, peer-critical-review and public opinion. (4) Important technical issues in GBZ 2.1 need to be elaborated and examined, including the concept of excursion limits, adjustment of OELs for unusual work schedules, the concept and application of synergetic effect, description of the forms and physical characteristics of chemical substances.