NO₂ limits: What applies in the workplace?
The EU limit value is 40 µg as an annual average, while the so-called workplace limit value is set at 950 µg per m³. Especially with regard to air quality at the workplace, however, there are countless misunderstandings that need to be explained. Fundamental is the so-called MAK value (short for: maximum workplace concentration), which is a scientific recommendation of the German Research Foundation. It also corresponds to the workplace limit value for NO₂ (AGW), which was established according to the Ordinance on Hazardous Substances.
This AGW applies to workplaces in trade and industry where increased NO₂ levels(more on the measured value of nitrogen dioxide) are to be expected due to the specific conditions on site. And: The recommended maximum workplace concentration is based on a healthy adult.
The AGW assumes a permanent, average exposure to nitrogen dioxide of eight hours on each of five days per week. The value describes the concentration at which neither acute nor chronic damage is to be expected. The occupational exposure limit for nitrogen dioxide is 950 µg/m³.
Only four times per shift and for a duration of 15 minutes may the limit be exceeded 8 times. However, these high limits are only tolerated because people are regularly examined for their health, are exposed to this load for a maximum of 40 hours per week and - in particular - are subject to continuous medical monitoring.
Apart from these specially regulated workplaces, no specific limit values for NO₂ have been set. In general, of course, the air in workspaces should be harmless to health and present in sufficient quantity. This usually corresponds to the outdoor air quality. So anyone who works in an office or from home, for example, has so far been subject to those limit values that have also been defined for outdoor air by the Federal Environment Agency. The WHO also recommends 40 µg/m³ as a guide value for indoor air.
However, at the end of 2018, the Committee for Indoor Air Quality Control (AIR) published revised guideline values for nitrogen dioxide concentrations for private and work spaces. According to this, the precautionary value (short-term guideline value I) of 80 µg/m³ applies for a measurement period of one hour in terms of preventive health protection. From a concentration of 250 µg/m³, the danger value (short-term guide value II) is relevant, according to which health is affected with a high probability.
The applicable limit values for outdoor air
Since 1 January 2010, the nitrogen dioxide limits for outdoor air issued by the European Union have been in effect. A distinction is made between three values: the annual mean value, the hourly value and the alarm threshold.
The legal immission value was set at an annual average of 40 µg/m³ in order to protect people's health. This value, determined by the World Health Organisation (WHO), particularly takes into account sensitive groups of people such as children, senior citizens, pregnant women and people with pre-existing conditions such as asthma and allergies, who are exposed to the pollutant nitrogen dioxide around the clock.
In addition, since 2001 there has been a special annual limit value of 30 µg/m³ for the protection of vegetation. For a measurement period of one hour, a maximum concentration for nitrogen dioxide of 200 µg/m³ applies. To protect human health, this may be exceeded a maximum of 18 times in a calendar year.
In addition, an alert threshold of 400 µg/m³ has been set for nitrogen dioxide. If this is measured as the mean value of an hour for three consecutive hours, government measures must be initiated immediately.
(Image: unsplash/ Patryk Gauza)
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