(Occupational exposure limit values (OELVs) must not be exceeded over a period of time. The revision of EN 689 gives a strategy for testing compliance with OELVs by measurement of exposure by inhalation to chemical agents. The strategy describes a procedure to perform a small number of exposure measurements to demonstrate with a high degree of confidence that workers are not likely to be exposed to concentrations higher than the OELV, taking into account the variability of exposures.
It comprises three main steps concerning groups of workers having similar exposure (Similar Exposure Group-SEG). During the first step- Basic Characterization-BC-the appraiser collects available information to allow reliable estimates of the exposure of the workers and to take the decision whether or not to perform exposure measurements. The second step, or ‘Initial Assessment-IA’, consists of performing at least 3 (screening test) to 6 representative exposure measurements for the workers of each SEG, in order to demonstrate by using a statistical test whether less than 5% of exposures in the SEG exceed the OELV (compliance). In a third step and based on IA results, a program of ‘Periodic Reassessment-PM’ determines time intervals ranging from 1 to 3 years for performing new measurements, depending of the levels of exposure. This is based on the assumption that no major changes (e.g. process, RMM, quantities and nature of chemicals) have occurred during this period.
The new EN-689 also takes into consideration simultaneous exposure to several chemicals, and workshift durations higher than 8 hours. The informative annexes give recommendations to determine for example: sampling duration, statistical distribution of exposure measurements results and treatment of representative results lower than the limit of quantification (LoQ).
The new EN 689 is a helpful tool, especially when expertise/science/evidence does not help in the decisions to protect workers exposed to chemicals.