Limit values used for the exposure assessment


Everyone who is engaged in performing occupational exposure assessment to chemicals sometimes faced with the need to search for or to derive limit values. The estimated exposure can be compared with these limit values to establish whether the work situation is sufficiently controlled.

There are different types of limit values. In Europe, there are three types of occupational exposure limits (OELs) for chemical agents: OELs set at the European level, at the national level or by companies themselves. However, regulations for setting OELs may vary and that is why for one substance several different OELs may exist within Europe. National OELs may be different from the community OELs and can vary per country. In addition to OELs, substances can be classified based on their possible carcinogenic properties. Furthermore, there are Derived No-Effect Level (DNELs) for workers' inhalation exposure, introduced under the REACH regulation.

What exactly is a limit value?

An OEL is the maximum allowed concentration of a given substance in the air at the workplace. We distinguish between time-weighted averages measured over an 8-hour period (8-h TWA), short-term exposure limits for a 15 min period (15-min STEL) or Ceiling.

Methods to derive limit values

There are different kinds of methods that are being used worldwide to derive the limit values. There are many differences in their derivation processes, which depend on the legislation under which they are derived, the actors performing the scientific assessment and the chemical substance.

In Europe, the methods for derivation of OELs by SCOEL (EU) and by the EU Member states may vary. SCOEL established a methodology to derive OELs and STELs whereas ECHA established guidance for deriving DNELs. The routes for final regulatory adoption can be summaries as:

• OELs established based only on scientific considerations

• OELs established based on scientific assessments that also take into account socio-economic and technical feasibility factors

How to use limit values in Stoffenmanager®

In Stoffenmanager®, several types of limit values can currently be assigned to components: 8-hour TWA (time-weighted average), 15-minutes or Ceiling. Aside from that, companies with production sites in several countries can also assign multiple national occupational exposure limit values

Would you like to know more?

In the “Stoffenmanager®” training, you will get practical tips how to search for limit values. You will also learn how to derive a limit value if no limit value can be found in any database. The connection with the use of Stoffenmanager® will also be explained. During the training, whether the situation is sufficiently controlled or not will also be discussed after performing a risk assessment.



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