| Monitoring mixed exposure
50. Further information on monitoring airborne contaminants is given in paragraphs 52 and 53. The number of components of a mixed exposure for which routine air monitoring is required, can be reduced if their relative concentrations can be shown to be constant. This involves the selection of a key or marker, which may be one of the constituents, as a measure of the total contamination. Exposure to the marker is controlled at a level selected so that exposures to all components will be controlled in accordance with the criteria in paragraphs 48(a) and (b). However, if one of the components has been assigned an OEL-CL, the level of the exposure to that substance should always be reduced as far as is reasonably practicable. If this approach is to be used, it should take place under the guidance of suitable specialist advice.
Complicating factors
51. Several factors that complicate the assessment and control of exposure to individual substances will also affect cases of mixed exposures and will require similar special consideration. Such factors include-
(a) exposure to a substance for which there is no established limit or for which an OEL-CL has been set;
(b) the relevance of factors such as alcohol, medication, smoking and additional stresses;
(c) exposure of the skin to one or more substances that can be absorbed by this route, as well as by inhalation; and
(d) substances in mixture may mutually affect the extent of their absorption, as well as their health effects, at a given level of exposure.
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