DFG presents the 2004 MAK and BAT value lists

Numerous changes and new entries – cadmium classified as a human carcinogen

The Senate Commission of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) on the Investigation of Health Hazards of Chemical Compounds in the Work Area has presented the 2004 Maximum Allowable Concentration (Maximale Arbeitsplatzkonzentrationen – MAK) and Biological Tolerance Value (Biologische Arbeitsstofftoleranzwerte – BAT) list and submitted it to the German Federal Minister of Economics and Labour. It contains suggestions for MAK values, i.e., the maximum allowable concentration of a working substance in the workplace atmosphere as a gas, steam or aerosol that according to current knowledge does not impair the health of employees exposed during eight-hour working days over the long term. Furthermore, the working substances are classified according to their carcinogenic, germ cell mutagenic, reproduction-endangering, sensitising or skin-absorptive effect. Compared to the previous year, there were 91 changes and new entries.

This year, two metals that were classified as carcinogenic in humans deserve particular notice: based on epidemiological data, cadmium and its inorganic compounds as well as tungsten carbide and cobalt-containing hard metals were classified as carcinogenic in humans and, therefore, placed in carcinogenicity category 1. Another heavy metal compound, indium phosphide, and 1,5-diaminonaphthalene, were proven to be carcinogenic in animal experiments and were assigned to carcinogenicity category 2.

Talcum (asbestos-fibre free) as a suspected carcinogenic working substance was placed in carcinogenicity category 3B, and the previous MAK value of 2 mg/m³ was suspended because the mechanism of action is unclear. Benzoyl chloride, ethyl chloroformate, 2,5-dimethoxy-4-chloroaniline, glyoxal and 1,5-naphthylene diisocyanate were also classified in this category as suspected carcinogens.

There were 15 examinations or new listings for carcinogenic working substances.

In the course of examining suspected carginogenic working substances in category 3 regarding a classification in the new categories 4 and 5, the food additive 3,5-di-tert-butyl-4-hydroxytoluol (BHT) was reclassified in category 4 with a MAK value of 20 mg/m³. The trimethylpentane isomers had to be reclassified into carcinogenicity category 3A because critical data for deriving a MAK value is lacking. Once again, no working substances were found this year for category 5.

Suspicion of a mutagenic effect of lead, cadmium, tungsten carbide and cobalt-containing hard metal, ethyl carbamate and o-aminoazotoluene on gametes has been substantiated.

The MAK value of lead was suspended because of its demonstrated genotoxic effect. Classification in carcinogenicity category 3B will be examined next year using new insights from epidemiology and animal experiments.

The MAK value of hydrogen chloride was reduced from 5 ppm to 2 ppm. For six other substances (BHT, isopropenyl acetate, isophorone diisocyanate, copper and its inorganic compounds, 2-phenylpropene and trimethylamine) MAK values changed or new ones were proposed; the values of hydrogen bromide, chlorine, propane, pentane, octane and diphenyl were confirmed after a thorough examination. For twelve substances, no MAK values could be determined (among them strontium and its inorganic compounds, ethyl acetoacetate, tributylamine and the cooling lubricant ingredient bis(2-ethylhexyl)zinc dithiophosphate) because of a lack of data.

The re-evaluation of earlier MAK values was conducted intensively, also in close cooperation with the European (SCOEL) and the American (TLV) Commissions. It was decided in the course of this examination to suspend the MAK values of three substances (1,5-naphthylenedi-isocyanate, diglycidylether and talcum) because of their suspected carcinogenicity and of another five substances (antimony hydride, bromine, ethylenediamine, diphosphorus pentasulfide and the pesticide dalapon) because of insufficient data for a health evaluation from the current perspective.

Thirteen working substances were also examined with respect to being particularly harmful during pregnancy. BHT, chlorine and hydrogen chloride were assigned to group C which contains those substances for which no teratogenicity is anticipated if the MAK values are adhered to. By contrast, copper, pentane, phenylpropene and trimethylamine were assigned to pregnancy group D which essentially states that classification into group C is not possible due to the available data. A risk of harming the embryo currently appears rather unlikely if the MAK values are complied with but cannot be ruled out with sufficient certainty. Xylene also remains in this group despite a new study. Due to a lack of data, propane, octane, acetate isopropenylester, hydrogen bromide and isophorone di-isocyanate could not be assigned to one of the groups and were listed in section IIc.

This year, a total of 22 working substances were examined for their respiratory tract and skin sensitising properties. New labelling was assigned to sixteen chemicals, including the aromatic compounds oak moss, geraniol and lyral, the enzyme papain, the substances bronopol and 5-ethyl-3,7-dioxa-1-azabicyclo[3.3.0]octane (EDAO), which are used as preservatives and biocides, as well as hard metal dust containing tungsten carbide or cobalt.

A total of 21 substances, among them the carcinogenic compounds cadmium, 1,5-diaminonaphthalene, o-aminoazotoluen, toluidine, toluylenediamine (diaminotoluene) and six N-nitrosamines, were newly labelled with the warning "H", which means that absorption through the skin together with inhalation may significantly contribute to their toxicity at the workplace. This warning label was checked and confirmed for two more working substances, bronopol and p-toluidine.

The section BAT values, biological guideline values and exposure equivalents for carcinogens (BAT-Werte, BLW und EKA) includes a new listing, i.e. the exposure equivalents for easily soluble nickel compounds (EKA).

The Senate Commission produced detailed scientific justifications for each new entry and change in the 2004 MAK and BAT value list. They are published by Wiley-VCH, Weinheim, Germany, and will also be made available online early in 2005. As in every year, the examination and new entry of MAK values and classification of numerous substances is announced in the Yellow Pages of the MAK and BAT value list.

29-jul-2004