Design of measurement strategies for workplace exposures

Measurement strategies for hazard control will have to be efficient and effective to protect a worker's health and well being. No measurement strategy for hazard control will ever be cost efficient in the short run when it is compared with the promises of tools such as the Control of Substances Hazardous to Health (COSHH) essentials (box 1): “a simple system of generic risk assessments which leads to the selection of an appropriate control approach”.1 Going straight to benchmark standards without the need of exposure measurements will certainly eliminate the cost of measurements. However, generic risk assessment tools like COSHH essentials and expert systems like the Estimation and Assessment of Substances Exposure (EASE)2 (box 2), as well as expert judgement by an occupational hygienist, are known to be inaccurate and they do not take into account the various components of variability in exposure levels (box 3). In fig 1, results of EASE estimates are compared with actual measured concentrations. From these pictures it can be seen that EASE estimates tend to be (1) higher than the measured concentrations, and (2) inaccurate especially at lower “true” concentrations (< 50 ppm and < 5 mg/m3). Nowadays, the latter exposures are being more relevant for workplaces of the developed world. ### Box 1 Control of Substances Hazardous to Health (COSHH) essentials: easy steps to control chemicals

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