MAK-value

The U.S. Occupational Safety and Health Administration (OSHA) has set a ceiling level for iodine of 0.1 ppm in air. The American Conference of Government and Industrial Hygienists (ACGIH) estabUshed 0.1 ppm as the TLV (TWA) for iodine. The maximum allowable concentration in air (MAK value) is also 0.1 ppm (104—106). 

Elemental bromine is a readily evaporating liquid (pBr at 1 °C = 0.23 bar) with high reactivity. Because of the good solubility of Br2 in lipids, its aggressive and toxic properties affect skin and mucous membranes (bronchi). The MAK value of elemental Br2 is defined as 0.1 ppm (0.7 mg m 3), while the sense of smell is affected at a value of 0.01 ppm. The lethal concentration (around 100-200 ppm) is reached for example, by twice the MAK value, 5 min, eight times per working unit [91, 92]. 

Environment and health-related problems DCM is toxic for the central nervous system, for the liver and the kidneys (MAK-value 350 mg/m ), and it is absorbable via skin. Furthermore DCM is a suspected carcinogen (classification care, cat 3). DCM is low volatile and the vapour is heavier than air, thus high concentrations may occur at ground level during application. Activated-carbon-filters are ineffective and normal glove materials are penetrated within a few minutes. The required breathing equipment is, however, hardly used by craftsmen, which results in several deaths every year. 

Greim H (ed) Occupational Toxicants, Vol 13, critical data evaluation for MAK values and classification of carcinogens. Commission for the investigation of health hazards of chemical compounds in the work area, Bisphenol A, p 49. New York, VCH, 1999... 

DEG MAK. This is the standard established by the German Research Society, designated as workplace hazard potentials. The MAK values are revised annually. 

The MAK values are mean concentrations over the complete time of exposure. Allowable concentration peaks are restricted to limited values of concentration highs, period of exposure and frequency of these events per shift. In rating the hazardous potential of chemical exposure, animal experiments arc used and in addition compared with those of known human exposure, thus a high safety standard is guarantied. 

MAK values can be best compared, at an international level, with the definition of the Threshold Limit Values (TLV) of the American Conference of Governmental Industrial Hygienists, which may be expressed as a time-weighted average (TWA), as a short-term exposure (STEL), or as a ceiling value (CL).8... 

In addition to MAK values, which are for healthy persons capable of earning a normal living, the DFG publication20 includes so-called BAT values (biological tolerance limits) for substances which show additional biological effects. These define maximum concentrations of a substance, or its metabolites, normally in the blood or urine of an employee. Only one fluorinated chemical was included in 1997. 2-bromo-2-chloro-l,l,l-trifluoroethane = Halo-thane, CAS-No. 151-67-7, with a BAT value for trifluoroacetic acid (its toxic metabolite) of 25 mg - L 1 in human blood determined after exposure/shift. 

For further detailed information see refs 6, 76-81, 183 and 184. For MAK values of CFCs, etc., see Table 3. Most of the compounds listed above show considerable cardiac cffccts.7,, 0 J2 Carcinogenic and mutagenic potentials are reported in refs 93 and 94. b ODP = ozone depletion potential relative to Rll, calculated over their full lifetime.75 For global w arming potentials, see Table 13. 

The Berufsgenossenschaft der Chemischen Industrie (Germany) has recommended that all iron oxide pigments should be classified as inert fine dusts with an MAK value of 6 mg/m3. This is the highest value proposed for fine dusts. 

Chromium(III) oxide is not included in the MAK list (Germany), the TLV list (USA), or in the list of hazardous occupational materials of the EC [3.72]. In practice, this means that chromium(III) oxide can be regarded as an inert fine dust with a MAK value of 6 mg/m3. 

Classified as a carcinogenic substance in Section III A1 of the list of MAK values. 

In the soon to be published new MAK-list in Germany (maximal allowable workplace concentration) ozone will be categorized as IHb which means a substance being justifiably suspected to be carcinogenic. The actual MAK value of 200 pg m 3 (= 0.1 ppm) will be suspended until it is known if ozone shows carcinogenic effects (n. n 1995). 

Greim. H, Occupational Toxicants Critical Data Evaluation of MAK Values and Classification of Carcinogens. Vol, 14. John Wiley Sons, Inc., New- York, NY, 2000. 

Hence, organic solvents should be handled with care. In the USA, the threshold limit values [TL values) are used as a measure of the inhalation toxicity for chronic interaction with solvent vapours [90]. In the Federal Republic of Germany, the maximum concentration values at the workplace [MAK values) are used [91, 92]. Threshold limit values refer to airborne concentrations of substances and represent conditions under which it is believed that workers may be repeatedly exposed daily without adverse effect. They refer to time-weighted average concentrations for a normal 8-hour workday... 

The TL and MAK values should be used as guides in the control of health hazards. They are not constants that can be used to draw fine fines between safe and dangerous concentrations. Nor is it possible to calculate the TL or MAK values of solvent mixtures from the data in Table A-13, because antagonistic action or potentiation may occur with some combinations. It should be noted that occupational exposure limits such as the TL and MAK values are not intended for use as a comparative measure of one solvent against another. The values set airborne concentration limits on chemical exposure, but do not describe the ease with which that airborne limit is achieved. In addition, the vapour pressure of the solvent must also be considered. The lower the vapour pressure, the lower the airborne concentration. In order to better compare the safety of volatile compounds such as organic solvents, the use of the vapour hazard ratio ( VHR) has been recommended as a feasible measure [175], The vapour hazard ratio is defined as the quotient of the saturation concentration of a solvent (in mg/m at a given temperature and pressure) and its occupational exposure limit (in mg/m e.g. TL or MAK values), according to ... 

The MAK-values of Table A-13 are reproduced with permission of the Senatskommission zur Prtifung gesundheitsschadlicher Arbeitsstoffe of the Deutsche Forschungsgemeinschaft , Boim-Bad Godesberg, Federal Republic of Germany. 

Despite the adoption of appropriate safety measures during manufacture, such as closed units and dust removal plants, ensuring emission values for chromate and lead below their respective MAK values (0.1 mg/m as Cr03 and 0.1 mg/m as Pb), chromate pigments are being increasingly substituted by other pigments. 

There do not exist any special values for permissible concentrations of hardmetal dust on the work place. Therefore, the MAK values for insoluble W and Co are valid (5mgWC/m and 0.5mgCo/m ). The ITIA (see Section 13.6) is encouraging inducing enhanced activity in regard to acute toxicity tests to be conducted on tungsten compounds including hardmetals (ITIA Newsletter, Jime 1997). 

Table I" summarizes the maximum permissable working concentrations of these substances in air. In Switzerland (CH) md Germany (GFR) they are called MAK-values, in the USA they eu e known as Threshold Limit Value-Time Weighted Average (TLV-TWA). CIBA-GEIGY established its own Permissible Internal Exposure Level (PIEL) for substances, such as bis(chloromethyl)ether, for which official levels are not available. 

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