Target Levels for Common Contaminants

The target level procedure was applied to 16 common air contaminants (Table 6.19). These are common contaminants in the industrial environ­ment, and in many cases are the most critical compounds from the view­point of need for control measures. The prevailing concentration data as well as the benchmark levels were taken from Nordic databases, mainly the Finnish sources, and described elsewhere.12>1J! In addition, a general model for assessing target values for other contaminants is presented in the table.

The target levels for 16 common contaminants were grouped into four categories in terms of concentration bands. The numerical values of the target level categories II and III were obtained by using information on current concentrations in standard practice and benchmark plants. As an example, information on inorganic total dust is shown in (Fig. 6.9). The register of the occupational hygiene measurements revealed that the ratio of the current concentration levels to OELs depends greatly on the particular contaminant. Therefore, target levels are not given as the same fraction of the OEL. Excluding ozone and formalde­hyde, the upper limit of “good industrial level” (category II) varies from 1% to 9% of the corresponding OEL in Finland. The upper limit of cat-

Egory “general industrial level" (category III) also varies from sub­stance to substance. Again apart from ozone and formaldehyde, the limit is 10-34% of the corresponding OEL. Ozone is an exceptional

Compound because outdoor concentrations of ozone may be higher than indoor concentrations. Formaldehyde, which is one of the most com­mon compounds in the manufactured environment, is also a critical con­taminant, as the guideline value for residential air is relatively close to the corresponding OEL. It is worth emphasizing, however, that this scheme is still subject to further development.

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