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Press Release No. 37 | 19 July 2011
New Threshold Values for "Fine Dust" at the Workplace

Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area Presents List of MAK and BAT Values 2011 with 82 Modifications and New Entries

The 2011 List of MAK and BAT Values compiled by the Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, a Senate Commission of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), recommends reducing the general threshold value for dust for the respirable fraction in light of recent studies and classifies such dusts as carcinogenic when this threshold is exceeded. In addition, classifications for uranium and its inorganic compounds are now available. As in the past, the current list was sent to the German Federal Ministry of Labour and Social Affairs and forms the basis for legislation on the protection of health at the workplace. It contains new data on a total of 82 substances. Each classification, as with all substances on the list, is based on detailed scientific documentation and a transparent decision-making process.

For the respirable fraction of the general threshold value for dust (Allgemeiner Staubgrenzwert), the Commission not only determined a new MAK value of 0.3 mg/m3 (R-fraction) but also classified these so-called biopersistent granular dusts (GBS), which penetrate deep into the lungs upon inhalation, into Carcinogen Category 4. This identifies substances with carcinogenic potential that do not increase cancer risk in humans, provided the corresponding MAK value is observed. Also amitrol and ethylbenzene, for example, fell into this category in 2011. The Commission classified Portland cement and hydrotreated light petroleum distillates into Category 3B, which includes substances for which there is evidence of carcinogenic effects but for which data are not sufficient for final classification.

MAK values indicate the amount of a substance (as gas, vapour or aerosol in the air at the workplace) that will not cause adverse effects in the long term. In addition, the list indicates whether these substances can cause cancer, damage germ cells or a foetus during pregnancy, sensitize the skin or the respiratory tract or be absorbed through the skin. Apart from the MAK values, the list also indicates the concentration of a substance in the body to which a person can be exposed for the duration of his/her working life without adverse effects on health (BAT values). The “Biologischer Leit-Werte” and the “Biologische Arbeitsstoff-Referenzwerte” (BLW or BAR values) are also described.

Uranium and its inorganic compounds provide a fairly comprehensive example of the work of the Commission. Elemental uranium and its poorly soluble inorganic compounds are not only listed as causing carcinogenic effects in animal studies (Category 2), but also are classified as suspected of causing changes in germ cells. There are still too few data available for the soluble inorganic compounds, so that only suspected carcinogenic activity (Category 3B) can be determined . Nor can a MAK value be established since it is not clear at what concentration—however small—uranium no longer causes adverse effects. However, the Commission does specify which concentration in workplace air corresponds to the threshold value for nuclear radiation specified by the Commission on Radiological Protection. In addition, the substances are designated with “H” because absorption through the skin can contribute to health risk. In this case there is also no “Biologische Arbeitsstoff-Referenzwerte” (BAR value) based on scientific investigation because there were large regional differences. BAR values are not threshold values but they describe the background levels of a substance in the body—as determined, for example, in the blood—and thus enable comparison of exposure at the workplace with that already present.

As was the case last year, the Commission applied a method for the calculation of MAK values from animal experiments with oral intake of substances that is similar to that being used on the European level (REACH). The review of 24 values affected by this method resulted in a reduction for 11 of the substances. The rest remained unchanged.

Scientific comments on the documentation for all new entries and changes in the 2011 List of MAK and BAT Values can be submitted until 31 December 2011, presenting new data where appropriate. Only then will the Senate Commission officially adopt the proposed values and their documentation. Compiling the List of MAK and BAT Values is part of the DFG’s mission to provide policy advice to public authorities on questions relating to science and research, as laid down in its statutes.

Further Information

Further information about the work of the Senate Commission as well as a detailed list with all new additions and modifications can be found at:

There you will also find contact persons at the DFG and the contact data for the Commission’s secretariat.

Further information on health and safety at the workplace, available in German only, can be found on the DFG’s website under DFG Magazine:

Information for editors:

Editors can request a free copy for review from the DFG Head Office.

Contact person at the DFG’s Press and Public Relations Office: