The 2011 MAK and BAT Values List 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 limit value for dust for the alveolar fraction in light of recent studies and classifies such dusts as carcinogenic when these thresholds are 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 a detailed scientific explanatory statement and a transparent decision-making process.

For the alveolar fraction of the general threshold limit value for dust (Allgemeiner Staubgrenzwert), the Commission not only determined a new MAK value of 0.3 mg/m3 (for the "A-fraction") but also classified these so-called granular biologically long-lasting dusts (GBS) which penetrate deep into the lungs upon inhalation into Carcinogenicity Category 4. This identifies cancer-causing materials that do not increase cancer risk in humans, provided the corresponding MAK value is not exceeded. For example, in 2011, amitrol and ethyl benzene also fell into this category. The Commission classified, among others, so-called Portland cement and light distillates of oil that have been treated with hydrogen into the Suspicious Substance Category 3B - materials for which there are suspicions of cancer-causing effects but for which the data is not yet clear enough for final classification.

MAK values indicate the amount of a substance - be it in the form of gas, steam or aerosol in the air at the workplace - that will not cause long-term damage. Additionally, the list indicates whether these substances are carcinogenic, can damage germ cells or a child during pregnancy, can sensitise the skin or the respiratory tract or can 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 his/her health being damaged (BAT values). The biological guideline values (BLW/BAR values) are also described.

Uranium and its inorganic compounds provide a fairly comprehensive example of the work of the Commission. Thus, not only were the uranium element and its slightly soluble inorganic compounds classified as carcinogenic in animal experiments (Category 2), but they were also classified as suspects for changing gametes. Too little data are available to date for the soluble inorganic compounds so that here only a suspicion of cancer-causing effect (Category 3B) can be noted. Nor can a MAK value be determined since it is not clear what uranium concentration - however small - no longer causes harm. However, the Commission does specify the level of atmospheric concentration corresponding to the limit value for nuclear radiation specified by the Radiation Protection Commission. In addition, the substances received the identification "H" because absorption through the skin can contribute to health risk. There is also no biological working substance reference value (BAR value) based on scientific investigation in this case because there were large regional differences. BAR values are not threshold values but they give the "background exposure" of a material in the body - as measured, for example, in the blood - and thus set the exposure at the workplace at a level comparable to that already preexisting.

As was the case last year, the Commission applied a procedure for the calculation of the 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 procedure resulted in a reduction for 11 of the substances. The rest remained unchanged.

Scientific comments on the justifications for all new inclusions and modifications in the 2011 MAK and BAT values list 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 rationale. Compiling this 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.

Cornelia Pretzer
Deutsche Forschungsgemeinschaft

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