List Of MAK And BAT Values 1998 Published - Ethanol And Sidestream Smoke Classifications Revised As Well

September 29, 1998

The Deutsche Forschungsgemeinschaft's (DFG) Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has published the List of MAK and BAT Values 1998. It contains suggestions for MAK values, that is, the maximum concentration of a chemical substance (as gas, vapor, or particulate matter) in the workplace air which generally does not have known adverse effects on the health of the employee even when the person is exposed during long periods of 8-hour working days. In addition, chemical substances at the work place are classified according to their carcinogenicity, genotoxicity, reproduction toxicity, sensitizing effects or skin absorption. There are 73 changes and new entries: included in these are the revision of the health risks resulting from exposure to ethanol in the form of vapors and aerosols or via skin contact and a revised classification of sidestream smoke (passive smoking) as carcinogenic for humans.


In the case of ethanol, it is known that various physiological processes burden the human body continually with a certain amount of ethanol. The resulting carcinogenic risk is considered to be unavoidable. If the exposure at the workplace does not significantly increase this body burden, there is also no significant increase in the associated carcinogenic risk. The appropriate concentration was determined to be 500 ml/m3, which was established as the new MAK value. At the same time ethanol was classified into the new Category 5 for carcinogenic substances. This category includes substances with carcinogenic and genotoxic effect (that is, interaction with the DNA in the cell), whose potency is considered to be so low that no significant contribution to human cancer risk is expected, provided that a special MAK value is observed.

The mutagenic effects of ethanol on germ cells were also evaluated, and the substance was classified into Category 2 for germ cell mutagens. However, as is pointed out in the documentation for occupational toxicants, the results from animal tests that led to this classification occurred only at very high dosages and, therefore, the risk of a mutagenic effect on germ cells (such as a risk for carcinogenicity) is considered to be insignificant if the MAK value is observed. The detailed documentation for occupational toxicants will be published in October of this year (in German; the English version will be available soon after that). Sidestream smoke (passive smoking)

That bronchial cancer may be caused by cigarette smoking was unequivocally confirmed and quantitatively documented by epidemiologists 30 years ago; a number of other kinds of cancer are also associated with tobacco smoking, although to a markedly lesser extent. While the smoker inhales the so-called mainstream and sidestream smoke, nonsmokers are exposed to the sidestream smoke coming out of the cigarette and the air exhaled by the smokers (passive smoking).

Sidestream smoke contains numerous substances that are proven carcinogens either in humans or in animals and some of these are present in markedly higher concentrations than in mainstream smoke. The sidestream smoke is inhaled and absorbed by nonsmokers in quantities from which an increased incidence of lung tumors is to be expected. Studies on internal exposure show on the basis of various biomarkers that passive smokers are exposed to an increased burden from the carcinogenic substances contained in sidestream smoke in comparison to non-exposed persons. In addition, an intensified effect from passive smoking and known carcinogenic substances should be taken into account.

Other new classifications

Special emphasis should be given this year to the revised classification of carcinogenic substances into five categories. The previous groups IIIA1 (carcinogenic to humans), IIIA2 (carcinogenic in animal studies), and IIIB (substances with suspected carcinogenic potential) were renamed, with slight changes, as the new Categories 1, 2, and 3. Moreover, two new categories, 4 and 5, were established on the basis of the expansion of our knowledge about the reaction mechanisms of carcinogenic substances and methods for risk assessment and risk quantification. MAK or BAT ("Biologischer Arbeitsstoff-Toleranz-Wert": biological tolerance value for occupational exposures) values were established for both categories; provided that the values are observed, no significant contribution to human cancer risk is expected from the substance concerned. Category 4 contains those substances for which genotoxic reaction mechanisms play a minor role, for example, substances with tumor-promoting properties. Category 5 is intended for substances for which genotoxicity decidedly characterizes the reaction mechanism, but from which no significant contribution to human cancer risk is to be expected if the MAK value is observed, for example, because the body burden from the substance is in the same range as that of the amount formed endogenously.

Seven substances were reviewed for toxicity particularly during pregnancy. Despite its lowered MAK value, ethanol remains in Group C, which contains those substances for which there is no reason to fear a risk of damage to the embryo or foetus if the MAK value is observed. Methoxyacetic acid, on the other hand, is classified into Group B, which contains those substances for which such a risk cannot be excluded.

There are 22 evaluations or revisions for carcinogenic substances. 1,3-Butadiene and sidestream smoke have been classified into Category 1, i.e. substances which cause cancer in humans. bChloroprene and toxaphene (chlorinated camphene) were classified into Category 2, i.e. considered to be carcinogenic for humans. Lindane and hexachlorobenzene were classified into the new Category 4. Because a threshold level is assumed for these substances, based on a nonlinear dose-effect relationship, no significant contribution to human cancer risk is to be expected if the MAK or BAT value is observed. Styrene and ethanol are placed into the new Category 5.

This year 25 substances were evaluated for their airway- and skin-sensitizing properties. Newly included were limonene, naphthalic anhydride, the mercury compounds Thiomersal and Merbromin as well as other acrylates, animal hair and woods.

Eleven substances were labelled with the warning indicator "H", i.e. absorption through the skin as well as inhalation can make a significant contribution to the toxicity in the work area; this is valid, for example, for lindane, hexachlorobenzene, toluene and xylene. This warning indicator was evaluated and confirmed for 12 other substances, including phenol and nitrobenzene.

There are eight new entries or changes in the section about biological tolerance values for occupational exposure and exposure equivalents for carcinogenic substances ("BAT-Werte und EKA: Biologische Arbeitsstofftoleranzwerte und Expositionsäquivalente für krebserzeugende Arbeitsstoffe"), such as the lowering of the BAT values for carbon disulfide and mercury.

Detailed scientific documentations have been compiled by the Commission for each of the new entries and changes in the List of MAK and BAT Values 1998. They will be published by WileyVCH, Weinheim. As in every year, the evaluation or new inclusion of MAK values or classifications for numerous substances is announced in the "yellow pages" of the List of MAK and BAT Values.


Deutsche Forschungsgemeinschaft

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