Assessment of chemical exposures

The values to be used for assessing air quality in indoor workplaces such as offices are frequently the subject of some debate. There are no specified occupational exposure limits for indoor workplaces that do not fall within the scope of the ordinance. Instead, such workplaces are subject to the general guidance on ventilation given in Annex 3.6 to the German Workplace Ordinance, according to which there must be sufficient healthy air in work rooms. In accordance with the Technical Rules for Workplaces governing ventilation (ASR A3.6), this requirement is met if the quality of the air is essentially the same as that of the outdoor air.

However, the immission values and other assessment values specified for outdoor air cannot automatically be applied to indoor air since they may have been drawn up with the aim, for example, of protecting vulnerable plant or animal life, not human beings. Furthermore, using the quality of the outdoor air as a standard against which to compare the quality of the indoor air causes problems in practice if the outdoor air is polluted.

As a result, the values currently used in Germany to assess exposure in indoor workplaces vary considerably in terms of their nature and origin. Unlike occupational exposure limits, these values are not presented in one binding rule and, in particular, they do not have consistent legal relevance. Almost all values for indoor rooms are merely recommendations.

The German Committee on Indoor Guide Values has drawn up guide values for indoor rooms in general, including rooms in dwellings, based on toxicological evidence. These values best meet the criteria for a valid assessment of air quality in indoor workplaces. Statistically derived reference values can be used to assess those substances for which there are no guide values yet. In accordance with an international convention, the 95 percentile value of a sufficiently large set of data can be used as a reference value. This assumes (without a toxicological assessment being carried out) that the “normal conditions” that are present in the rooms investigated and do not give rise to illness or health complaints can be deemed generally acceptable. Unlike guide values, reference values cannot be used to assess health risks. As such, if the actual values are lower than the reference values this does not necessarily mean that there is no risk to health. By the same token, if the values are higher it does not automatically mean that there is a risk.