Focus on Nitrous Gases and Zinc

The MAK and BAT Values List for 2009 has been issued by the Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area established by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation). This year's list contains 62 changes and new entries.

These include revised assessments of nitrogen monoxide and nitrogen dioxide. These gases are produced during combustion processes and thus occur in automobile emissions. Amongst other things, they cause acid rain. Oxides of nitrogen are used in the industrial production of nitrites. Purest nitrogen monoxide has many uses in medicine, including treating newborn babies with respiratory failure and as a test gas in calibrating measuring devices. The trace element zinc, which we ingest through our food, is a component of important enzymes. If inhaled, however, it can have toxic effects on the lungs, including a condition known as zinc fume fever. The element and its inorganic compounds formed the focus of the Commission's investigations, with new MAK values being defined for these substances. The results of the re-examination showed that the maximum concentration of zinc oxide fumes in the breathing air supply to which workers can be exposed without suffering adverse health effects is considerably lower than was previously stated.

As every year, the list was presented to the Federal Minister for Labour and Social Affairs at the beginning of July. After thorough scientific testing, it will be used to make recommendations on occupational health. In addition to the MAK values, the list also shows the concentration of a substance in the body to which a person can be exposed during his or her working life without suffering any adverse health effects (BAT values). The Biological Guide Values and Biological Substance Reference Values (BLW or BAR values) are also included. Furthermore, the scientists and academics of the DFG Commission also investigated whether or not a particular substance causes cancer, has a mutagenic effect on gametes or poses a risk to unborn children during pregnancy. Analyses of the substances' sensitising and skin resorption effects were also performed.

In the carcinogenic substances category there are, this year, a total of seven revisions or alterations. These include the categorisation of the chromates (except lead and barium chromate) as carcinogenic in humans. According to the new MAK and BAT Values List, chromium (VI) compounds damage gametes and cause skin sensitivity. They received an "H" warning, which means that absorption via the skin can significantly contribute to the substance's toxicity. The Commission also checked 13 substances for pregnancy risks. These include di-n-butyl phthalate from the phthalates group, phenyltin compounds, phosphine, propionic acid, zinc and its inorganic compounds – with which, if the MAK value is adhered to, there is no risk of foetal damage. There were a total of 13 changes and additions to the "BAT Value, BLW, BAR and EKA" section of the list.

In 2009, the Commission also published additional Biological Substance Reference Values (BAR values), which were first published in 2008. These values are not limits; instead, they define the "background exposure level" of a substance in the body. The BAR values permit comparisons between the level of exposure experienced by the general population and the exposure measured in the workplace. BAR values were determined for the following substances: acrylonitrile, soluble barium compounds, beryllium and its inorganic compounds and nickel and its compounds, plus o-toluidine and vinyl chloride.

As every year, once the current list has been submitted to the Federal Minister for Labour and Social Affairs, it is subject to a comments deadline. During this period, detailed written explanatory statements on every substance evaluated are requested from the Commission's Scientific Office by the end of the year and new information and remarks can be added. These are also verified and, if necessary, taken into consideration. Only once this has been done will the Senate Commission conclusively adopt the proposed values and their justifications as the basis for legislation on health and safety in the workplace.

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Source-Eurekalert
RAS