10. Air Monitoring
The measurement of airborne fibre in the workplace is crucial to determining the effectiveness of dust control measures and demonstrating compliance with regulations. Effective fibre monitoring program must have the commitment of management, a comprehensive monitoring strategy and sound measurement methods.
10.1 Monitoring strategy
A systematic air monitoring programme should be established to evaluate whether exposure of workers to chrysotile asbestos dust is being kept under control. Personal monitoring should be included in the programme in order to measure fibre concentrations. Static sampling should be undertaken where relevant. The aims of the air monitoring programme should be:
- to ensure that the health of the workers is efficiently protected;
- to ensure that the preventive actions which have been taken are still effective;
- to ensure that the levels, as measured previously, remain unchanged or fall;
- to ensure that any changes made in manufacturing processes or work practices will not lead to an excessive exposure to asbestos dust; and
- to promote the implementation of more efficient preventive measures.
The monitoring programme should be performed only by skilled personnel with proper equipment and training. Such individuals should be active in national and/or international quality assurance schemes.
10.2 Measurement methods
The most widely adopted technique used for the measurement of concentrations of respirable fibres in air, is the membrane filter method using phase contrast optical microscopy. The most common method used is that of the Asbestos International Association (RTM 1, 1982), which was adopted by the International Labour Office (ILO, 1984). Other methods include the NIOSH 7400 method and the new WHO recommended method for airborne fibres.
10.3 Record keeping
For facilities operating in compliance with national regulations, air monitoring should be done at least once a year. For factories where improvements are being made, air monitoring should be done more regularly to determine the effectiveness of the actions taken and the need for additional preventive and control measures. In all cases, records should be kept by the employer on all aspects of dust exposure. Such records should be clearly marked by date, work area and plant location and maintained for at least a 30-year period following termination of employment.