Recommended and introduced by OCI:

The standard GBZ 2.1-2019 “Occupational Exposure Limits for Hazardous Agents in the Workplace – Part 1: Chemical Hazardous Agents”, as the substitute for GBZ 2.1—2007), came into force on April 1, 2020, and the standard GBZ 2.1—2007 was abolished on the same date.

Since 2007, employers and occupational disease prevention professionals have proposed some problems that need to be solved urgently in the practice of occupational disease prevention and control, such as how to define occupational exposure, how to identify the circumstances under which occupational health actions should be taken, how to compare the detection results of occupational hazardous agents in the workplace with the occupational exposure limits, and the problems related to correction of occupational exposure limits for special working hours and timely inclusion of the newly revised occupational exposure limits into the standards, etc. Therefore, the drafting team, based on the considerations on above problems, has made revisions to the standard in several aspects such as concept, text structure, occupational hazard control principle, occupational exposure assessment, adjusted individual exposure limits, and updated the occupational exposure limits after reviewing the toxicology and occupational epidemiology data and the latest research results at home and abroad, thus forming an updated version of the standard.

Compared with GBZ 2.1 -2007, in addition to editorial changes, the main technical changes in this revision include:

1. Six normative reference documents are added;

GBZ/T 192 (all parts) Determination of Dust in the Air of Workplace

GBZ/T 224 Terminology of Occupational Health

GBZ/T 225 Guidelines for Employers on Prevention and Control of Occupational Disease

GBZ/T 229.2 Classification of Occupational Hazardous Operations in Workplaces - Part 2: Chemicals

GBZ/T 295 Biological Monitoring Methods for Occupational Population – General

GBZ/T 300 (all parts) Determination of Toxic Substances in the Air of Workplace

2. Nine concepts or definitions related to occupational exposure limits are added, including occupational exposure, adverse health effects, critical adverse health effects, peak exposure, exposure level, ratio of occupational exposure level to OELs and ratio of mixed exposure, action level, biological monitoring and biological exposure limits; five concepts and terms used in the former version are deleted, including workplace, work site, total dust, respirable dust and aerodynamic diameter; and the concept of peak exposure is introduced to substitute excursion limits;

Nine concepts or definitions related to occupational exposure limits are added, including

(1) Occupational exposure

It refers to the exposure of laborer to the occupational hazardous agents through respiratory tract, skin mucous membrane and other routes in occupational activities.

(2) Adverse health effects

It refers to harmful health effects or toxic effects caused by exposure to occupational hazardous agents, which could only cause health damage when reaching a certain level of exposure, that is, excessive exposure.

(3) Critical adverse health effects

It refers to the adverse health effects used to determine the allowable exposure concentration, i.e. occupational exposure limit, of certain occupational hazardous agent.

(4) Peak exposures (PE)

It refers to the maximum or peak concentration of a specific substance in the air determined in the shortest analyzable time period (no more than 15 min). in the event of exposure to chemical hazardous agents with PC-TWA but without PC-STEL, the peak exposure should be used to control short-term exposure. On the premise of complying with PC-TWA, it is allowed that the peak exposure exceeds PC-TWA level for any short time (15 min) within one working day.

(5) Exposure level

It refers to the concentration or intensity of occupational hazardous agents that laborers are actually exposed to in the workplace in a specific period of time during occupational activities determined by standard detection methods.

(6) Ratio of occupational exposure level to OELs

Ratio of mixed exposure

It refers to the ratio between the actual exposure level of laborers exposed to certain an occupational hazardous agent and the corresponding occupational exposure limits of the agent.

When laborers are exposed to more than two kinds of chemical hazardous agents, the sum of the ratio between the actual measured value for each chemical hazardous agent and its corresponding occupational exposure limits is called the ratio of mixed exposure.

(7) Action level

It refers to the level of laborers' actual exposure to chemical hazardous agents, which requires employers to take control measures or actions such as occupational exposure monitoring, occupational health monitoring, occupational health training, and occupational disease hazard notification, also known as administration level or administration concentration.

The action level of chemical hazardous agents varies according to the workplace environment and the hazardous agents exposed, and is generally half of the allowable exposure of the agents.

(8) Biological monitoring

It refers to the systematic monitoring of the content (concentration) of chemical substances or their metabolites in biological materials such as blood and urine of laborers, or the level of harmless biological effects caused by them, with the aim to evaluate the degree of exposure of laborers to chemical hazardous agents and their possible health effects.

（9）Biological exposure limits (BELs)

It refers to the recommended maximum allowable value of chemical substances or their metabolites, or biological effects caused thereby in laborers' biological materials, which is also taken as the guiding value for evaluating biological monitoring results. If the biological monitoring value is within the recommended range, most of laborers will not be adversely affected in health by exposure for 8 hours per day, 5 days per week. It is also called Biological Exposure Indices (BEIs) or biological limit values (BLVs).

Five concepts and terms used in the former version are deleted, including

(1) Workplace

It refers to all places where laborers engage in professional activities.

(2) Work site

It refers to the working place where laborers often or regularly stay for professional activities or production management.

(3) Total dust

It refers to the dust that could enter the entire respiratory tract (nose, pharynx and larynx, thoracic bronchi, bronchioles and alveoli), called “total dust” for short. Technically, it refers to all the dust measured by the total dust sampler in the respiratory zone according to the standard method.

(4) Respirable dust

It refers to the dust particles that could enter alveoli and are collected according to the standard measurement method of respirable dust, with an aerodynamic diameter of below 7.07 μm, and a sampling efficiency of 50% for dust particles with an aerodynamic diameter of 5 μm, called “respirable dust” for short.

(5) Aerodynamic diameter (d_ae)

If a particle (of any shape and density) and a sphere with a relative density of 1 have the same settling rate in static or laminar air, the diameter of the sphere is regarded as the aerodynamic diameter of the particle.

The concept of peak exposure is introduced to substitute excursion limits;

(1) Excursion limits

For chemical hazardous agents without PC-STEL, the concentration of any short-time (15min) exposure should not exceed the multiple value of PC-TWA under the condition that the 8h weighted average allowable concentration level has been met.

3. Occupational exposure limits of 28 chemical hazardous agents developed and revised in recent years has been summarized and added;

(Not all agents mentioned above included herein)

4. Chinese or English names of 8 chemicals and CAS numbers of 8 chemicals are changed, and CAS numbers of 2 chemicals are added;

5. Sensitization marks of 16 substances, skin effect marks of 4 substances and carcinogenic marks of 14 substances are added, and carcinogenic marks of 7 substances are changed;

6. The exposure limit of nitric oxide is incorporated into the exposure limit of nitrogen dioxide;

7. Adverse health effects based on which the occupational exposure limits are formulated are clearly listed;

8. Biological monitoring indices and occupational exposure biological limits are added. On the basis of summarizing 15 published standards on occupational exposure biological limits, 13 occupational exposure biological limits approved in recent years are added;

9. Relevant requirements of monitoring and testing methods are further improved;

10. The requirements on occupational exposure control principle and occupational exposure grade classification control of chemical hazardous agents in the workplace are added;

11. Instructions for the correct use of this standard are detailed and improved.

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