Limitations of the information used to assess health risks

These sources are important, but they have limits:

• one chemical may have many different SDSs from different suppliers
• an SDS may be missing information
• an SDS may be hard to read and understand. It may need a lot of reading, may be too technical, and may not be available in your own language. Some companies have successfully asked their suppliers to provide SDSs in other languages.

The role and limitations of hazardous substance monitoring

Employers should monitor and record workers' exposure to hazardous chemicals to protect their safety and health. They should make sure workers are not exposed above exposure limits or other criteria for evaluating and controlling the working environment, and they should assess exposure on the basis of the monitoring data.

Airborne concentrations of hazardous chemicals should be measured in every place of work where this is needed to protect workers against inhalation risks. Measurement is necessary if other techniques cannot give a valid estimate of the exposure risk or assess the existing controls. Other techniques for assessing the risk include:

• information on the intrinsic health and physical hazards, from the safety data sheets
• estimating exposure from the method of work and work pattern
• advice from the supplier
• experience of exposure in the workplace or among other users
• simple qualitative tests

Where a systematic measurement programme is decided on, it should evaluate whether workers' exposure to certain hazardous chemicals is acceptable. The aims of the programme should be to:

• make sure workers' health is efficiently protected
• make sure the preventive actions taken are still effective
• make sure measured levels stay the same or fall
• make sure changes to manufacturing processes or work practices will not lead to excessive exposure
• promote more efficient preventive measures

Only skilled personnel with suitable equipment and technical training should monitor airborne concentrations in the working environment. The employer should arrange regular inspection, maintenance and calibration of the measuring equipment.

Several limitations must be considered before monitoring hazardous substances:

• Accuracy of results. Monitoring equipment is often limited in accuracy, and results vary between times of use.
• Variation in personal exposure. Even with careful monitoring, an employee's personal exposure may differ from the monitoring results because of personal habits and one-off events.
• Absence of a WEL. Not every substance has a limit, but monitoring can still identify exposure, compare tasks and evaluate controls using a competent assessment and other suitable benchmarks.
• Other exposure routes. Air monitoring measures airborne contamination, not total uptake through skin or ingestion. Biological monitoring can sometimes add information about uptake; choose the method for the substance and purpose.

Guidance on how best to monitor toxic substances is in the HSE document HSG173.

Summary notes for Element 7 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.