MAK Values Research Articles

P23-15 Pulmonary toxicity is the most sensitive endpoint for deriving MAK values for aluminium compounds

P23-15 Pulmonary toxicity is the most sensitive endpoint for deriving MAK values for aluminium compounds

Particle-size effect of Pt cathode catalysts on durability in fuel cells

Monodisperse Pt nanoparticles with three different sizes (d=2, 3, and 4nm, each with a very narrow standard deviation σd of 10%) supported on carbon black (CB) were prepared by the nanocapsule method. Four kinds of 50wt%-Pt loaded catalysts [Pt2nm/CB, Pt3nm/CB, Pt4nm/CB, and a commercial Pt2nm/CB (σd=20%)] were subjected to an accelerated durability test comprising standard potential step cycles between 0.6V and 1.0V vs. RHE, which simulates load cycles for fuel cell vehicles, in N2-purged 0.1M HClO4 solution at 65°C. The oxygen reduction reaction (ORR) activity and H2O2 yield at these catalysts were evaluated from the hydrodynamic voltammograms in O2-saturated 0.1M HClO4 solution at 65°C by the use a multi-channel flow double electrode technique. At the beginning of testing (BOT), all catalysts exhibited the identical value of kinetically-controlled area-specific activity (jk), and the kinetically-controlled mass activity (MAk) was proportional to the electrochemically active area (ECA). With increasing the number of potential step cycles, the MAk values of all catalysts decreased due to the reduction of the ECA, as a result of particle growth, but the jk values were nearly unchanged irrespective of such particle growth. After 30,000 cycles, at which each MAk (or ECA) had reached a stable value (end of testing, EOT), the smallest Pt catalyst (our Pt2nm/CB) still maintained the highest MAk, which was a factor of approximately two higher than those of Pt4nm/CB and the commercial Pt2nm/CB. Contrary to the common view, Pt nanoparticles as small as 2nm were found to be quite durable, maintaining high performance from the BOT to EOT, as long as they were uniform in size (σd≤10%) and highly dispersed over the whole surface of the carbon support.

News: german research 3/2014

Abstract50 th List of MAK and BAT Values / Transatlantic Careers / Towards More Sustainability

Biological reference values for chemical compounds in the work area (BARs): an approach for evaluating biomonitoring data

Biological monitoring is a routine method that has been applied in occupational medical practice for many years. A requirement for its application is the availability of criteria suitable for evaluating biomonitoring data. Health-based threshold values are particularly useful as a criterion, yet only for substances for which effect thresholds can reliably be determined. For substances for which the concept of health-based threshold values is not applicable, the Working Group Setting of Threshold Limit Values in Biological Materials of the DFG Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has recently established "Biologische Arbeitsstoff-Referenzwerte" (BARs, Biological Reference Values for Chemical Compounds in the Work Area) as an approach for evaluating biomonitoring data. The BAR represents the upper reference concentration of a biomarker in the general adult population without occupational exposure to the agent. It is derived from biomonitoring data of a sample of a defined population group. In general, a BAR corresponds to the 95th percentile of the sample distribution. Ideally, national environmental surveys including human biomonitoring results are used as basis for deriving BARs. The influence of age, sex, social status, residential area and life style factors on background exposure is considered in the evaluation of these values. Because tobacco smoking is the most frequent influencing factor, several BARs have been determined for non-smokers only. To date, BARs for 17 substances or substance groups are listed in the List of MAK and BAT Values 2011. BARs for another five substances have been discussed, but have not been established because of the insufficient scientific database. Establishing the BARs aims to facilitate the evaluation of human exposure to chemical compounds for which no health-based threshold values can be derived but an adequate assessment of exposure is required due to their toxicity. The application of BARs does not permit a toxicological evaluation, but does allow the occurrence and the extent of occupational exposure to hazardous substances to be proved.

Classification of skin sensitizing substances: A comparison between approaches used by the DFG-MAK Commission and the European Union legislation

A systematic classification of substances (or mixtures of substances) with regard to various toxicological endpoints is a prerequisite for the implementation of occupational safety strategies. As its principal task the “Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area” of the “Deutsche Forschungsgemeinschaft” (DFG-MAK Commission) derives and recommends maximum workplace concentrations and biological tolerance values (MAK and BAT values) based exclusively on scientific arguments. Several endpoints are evaluated separately in detail, e.g. carcinogenicity, risks during pregnancy, germ cell mutagenicity or contribution to systemic toxicity after cutaneous absorption. Skin- and airway sensitization is also considered; the present paper focuses on these two endpoints.

Biological tolerance values: change in a paradigm concept from assessment of a single value to use of an average

Since 1981 biological tolerance values for occupational exposure (BAT values) have been published in the List of MAK and BAT Values of the Deutsche Forschungsgemeinschaft (DFG). In 2007 the list includes threshold limit values for more than 90 substances. The BAT value was defined as the maximum permissible quantity of a chemical substance or its metabolites or the maximum permissible deviation from the norm of biological parameters induced by these substances. The biological limit values derived by other commissions (ACGIH, SCOEL) are to be understood as averages, which may well be exceeded individually, in contrast to the BAT values that were defined as ceiling values and thus did not allow an excess of values in the individual employee. The DFG Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has now revised the concept of biological limit values. The BAT value describes the concentration of a chemical substance, of its metabolites or of an effect indicator in appropriate biological material derived by occupational medical and toxicological criteria, at which the health of an employee is usually not affected, even after repeated or long-term exposure. In this case, derivation of the BAT value is based on the average internal exposures. With this redefinition of the German BAT value, it will be possible to better harmonize the values with those provided by other commissions, which are also based on an average concept.

Urinary elimination of nickel and cobalt in relation to airborne nickel and cobalt exposures in a battery plant

To estimate the relationship between Ni concentrations in the ambient air and in the urine, at a battery plant using nickel hydroxide. Workers occupationally exposed to a mixture of nickel hydroxide, metallic cobalt and cobalt oxyhydroxide dust were studied during two consecutive workdays. Air levels of Ni and Co in total dust were determined by personal sampling in the breathing zone. Both metals in air were sampled by Teflon binder filters and analyzed by inductively coupled plasma absorption emission spectrophotometry. Urine was collected from 16 workers immediately before and after the work shift. Urinary Ni and Co concentrations were measured by electrothermal atomic absorption spectrometry. A poor correlation was seen between Co in the air and in post-shift urine (r = 0.491; P < 0.01), and no correlation was found between Ni in the air and in post-shift urine (r = 0.272; P = 0.15), probably due to the use of respiratory protection. The subjects were exposed to higher levels of Ni than Co (Ni (mg/m(3)) = -0.02 + 7.41 Co (mg/m(3)), r = 0.979, P < 0.0001). Thus, exposure to Co at 0.1 mg/m(3) should produce a Ni level of 0.7 mg/m(3). According to section XIII of the German list of MAK and BAT Values, a relationship between exposure to Co and urinary Co excretion, Co (microg/l) = 600 Co (mg/m(3)), has been established and the relationship between soluble or insoluble Ni salts in the air and Ni in urine was as follows: Ni (microg/l) = 10 + 600 Ni (mg/m(3)) or Ni (microg/l) = 7.5 + 75 Ni (mg/m(3)). Assuming nickel hydroxide to be soluble and to be insoluble, the Ni concentrations corresponding to Ni exposure at 0.7 mg/m(3) were calculated as 430 and 60 microg Ni/l, respectively. Similarly, exposure to Co at 0.1 mg/m(3) should result in Co urinary concentrations of 60 microg Co/l. On the other hand, a good correlation was found between Co and Ni in post-shift urine (Ni (microg/l) = 9.9 + 0.343 Co (microg/l), r = 0.833, P < 0.0001). On the basis of this relationship, the corresponding value found in our study was 0.343 x 60 microg Co/l + 9.9 = 30.5 microg Ni/l. This value was close to that calculated by the equation for a group of insoluble compounds, but about 14 times lower than that calculated by the equation for a group of soluble compounds. Our results suggest that exposure to nickel hydroxide yields lower urine nickel concentrations than the very soluble nickel salts, and that the grouping of nickel hydroxide might be reevaluated. Therefore, to evaluate conclusively the relationship between nickel hydroxide dust in the air and Ni in post-shift urine, further studies are necessary.

Assessing Occupational Exposure to Perchloroethylene in Dry Cleaning

Occupational exposure to perchloroethylene (PERC) in dry cleaning is analyzed by calculating airborne concentrations for a large set of possible exposure scenarios. Different generations of dry-cleaning machines ranging from vented machines used until the 1980s to nonvented closed-loop machines used since the 1990s are investigated; the geographical scope of the study is Germany. Concentrations are calculated for diffuse emissions, release of contaminated air during loading and unloading, and residual solvent releases from cleaned garments with a dynamic two-box model for near field and far field. The concentration estimates for near field and far field agree well with measured concentrations. The airborne concentrations are compared with maximum workplace concentrations (MAK values). The full set of scenarios shows for which historical situations the workplace concentrations were near the MAK value and that the transition to newer dry-cleaning machines reduced the occupational exposure by more than one order of magnitude. In addition, numbers of exposed workers are estimated for different years. Whereas more than 25,700 workers in the near field were exposed to PERC in 1975, the number has been below 5900 since 2001, which is due mainly to a reduced amount of garments being dry cleaned and, to a lesser extent, to replacement of PERC by nonchlorinated solvents. The results from the scenario-based analysis are consistent with exposure ranges obtained from a Monte Carlo calculation using frequency distributions of key input parameters, such as emission factors, batch times, and room volumes.

Reduction of occupational exposure to perchloroethylene and trichloroethylene in metal degreasing over the last 30 years: influences of technology innovation and legislation.

Occupational exposure to trichloroethylene (TRIC) and perchloroethylene (PERC) in metal degreasing is analyzed by calculating airborne concentrations for a large set of possible exposure scenarios (Scenario-Based Risk Assessment, SceBRA). Different types of degreasing machines ranging from open-top machines used until the 1980s to closed-loop nonvented machines used since the 1990s are investigated; the scope of the study is Germany. Concentrations are calculated for different kinds of releases (emissions from open baths, leakage, release of contaminated air during loading and unloading) with a dynamic two-box model for the near-field and the far-field. The concentration estimates are in good agreement with measured data. The airborne concentrations are compared to maximum workplace concentrations (MAK values). The full set of scenarios shows for which situations MAK values were exceeded and how the transition to newer degreasing machines reduced the occupational exposure by more than one order of magnitude. In addition, numbers of exposed workers are estimated for different years. While more than 25,000 workers in the near-field were exposed to TRIC and PERC in 1985, the number is below 3000 since 1996, which is mainly due to technology changes, rationalization, automatization, and replacement of TRIC and PERC by nonchlorinated solvents.

When should a substance be designated as sensitizing for the skin ('Sh') or for the airways ('Sa')?

In the List of MAK and BAT Values compounds are designated with 'Sa' ('sensitizing for the airways') or 'Sh' ('sensitizing for the skin') if, according to scientific evidence, they are allergens. Mainly based on suggestions by a WHO working group and based on our own experience, extended criteria have been elaborated by the working group 'skin and allergy' of the Commission of the Deutsche Forschungsgemeinschaft for the Investigation of Health Hazards of Chemical Compounds in the Work Area, which are presented in this article. They serve as guidelines for deciding which substances have to be labelled 'Sa' and 'Sh', respectively, for the prevention of sensitization and subsequent allergic diseases in workers. Although in some special cases their strict application may not be deemed necessary or possible, the proposed new criteria should be used to make the procedure of classification of substances: 1) more rational, 2) more consistent, 3) more comprehensible, and 4) more transparent. This paper informs readers working scientifically or administratively in this field and invites a critical discussion of the issue.

"When should a substance be designated as sensitizing for the skin ("sh") or for the airways ("sa")"?"

In the List of MAK and BAT Values compounds are de- signated withSa' (`sensitizing for the airways') orSh' (`sensitizing for the skin') if, according to scientific evidence, they are allergens. Mainly based on suggestions by a WHO working group and based on our own ex- perience, extended criteria have been elaborated by the working groupskin and allergy' of the Commission of the Deutsche Forschungsgemeinschaft for the Investigation of Health Hazards of Chemical Compounds in the Work Area, which are presented in this article. They serve as guidelines for deciding which substances have to be labelledSa' andSh', respectively, for the prevention of sensitization and subsequent allergic diseases in workers. Although in some special cases their strict application may not be deemed necessary or possible, the proposed new criteria should be used to make the procedure of classification of substances: 1) more rational, 2) more consistent, 3) more comprehensible, and 4) more trans- parent. This paper informs readers working scientifically or administratively in this field and invites a critical discussion of the issue. Human & Experimental Toxicology (2002) 21, 439±444.

Selective polypyrrole electrodes for quartz microbalances: NO 2 and gas flux sensitivities

Quartz microbalances were produced which have polypyrrole as a conductive polymer electrode. The polymer layers were operated as both electrode and sensitive material to detect the concentration of toxic gases. Tests with NO 2 demonstrated detection limits below the MAK values at room temperature. It was also investigated the response to some other noxious compounds and to the total gas flux. The possible mechanisms associated with the sensor properties are pointed out and discussed.

P -ARAMID RFP DO NOT INDUCE CHROMOSOMAL ABERRATIONS IN A STANDARDIZED IN VITRO GENOTOXICITY ASSAY USING HUMAN LYMPHOCYTES

Genotoxicity evaluations have been proposed as regulatory requirements for establishing German MAK values for inhaled fibrous dusts. The objective of this in vitro assay was to assess the potential for para -aramid (p -aramid) respirable-sized, fiber-shaped particulates (RFP) to induce chromosomal aberrations in cultured human peripheral blood lymphocytes without metabolic activation. The highest concentration tested in this assay was limited by the physical characteristics of p -aramid RFP. The test substance was suspended in fully supplemented RPMI culture medium with 1% Pluronic F68. All dosing was achieved using a dosing volume of 90% (900 µl/ml), and the vehicle control cultures were treated with 900 µl/ml of fully supplemented RPMI culture medium with 1% Pluronic F68. In the chromosomal aberrations assay, the treatments were either 3 or 19 h without metabolic activation. Cultures were harvested 22 h from the initiation of treatment. Replicated cultures of human whole blood lymphocytes were incubated with p -aramid RFP concentrations of 6.30, 12.6, 25.2, 50.4, 101, 201, and 401 µg/ml. Cultures treated with concentrations to 50.4 µg/ml for 3 h and 6.30, 12.6, 25.2, and 201 µg/ml for 19 h were analyzed for structural and numerical chromosomal aberrations. No significant increase in cells with chromosomal aberrations, polyploidy, or endoreduplication was observed in the cultures analyzed. The results demonstrated that p -aramid RFP was negative for inducing chromosomal aberrations in cultured human peripheral blood lymphocytes without metabolic activation. In addition, we conclude that the utility of these tests for evaluating the genotoxicity of fibrous or particulate materials is questionable.

Recommendations for the categorization of germ cell mutagens.

Germ cell mutagens are currently classified into three categories in the German List of MAK and BAT Values. These categories have been revised and extended by analogy with the new categories for carcinogenic chemicals. Germ cell mutagens produce heritable gene mutations, and heritable structural and numerical chromosome aberrations in germ cells. The original categories 1 and 2 for germ cell mutagens remain unchanged. Two new categories 3A and 3B are proposed for chemicals suspected to be germ cell mutagens. A new category 5 is proposed for germ cell mutagens with low potency that contribute negligibly to human genetic risk provided the MAK value is observed.

Changes in the classification of carcinogenic chemicals in the work area. (Section III of the German List of MAK and BAT values).

Carcinogenic chemicals in the work area were previously classified into three categories in section III of the German List of MAK and BAT values (the list of values on maximum workplace concentrations and biological tolerance for occupational exposures). This classification was based on qualitative criteria and reflected essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. In the new classification scheme the former sections IIIA1, IIIA2, and IIIB are retained as categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to the risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by non-genotoxic mechanisms, and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose/response relationships and toxicokinetics and for which risk at low doses can be assessed are classified in category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for category 4 (1,4-dioxane) and category 5 (styrene) are presented.

Changes in the classification of carcinogenic chemicals in the work area. Section III of the German List of MAK and BAT Values.

Carcinogenic chemicals in the work area are currently classified into three categories in section III of the German List of MAK and BAT Values (list of values on maximum workplace concentrations and biological tolerance for occupational exposures). This classification is based on qualitative criteria and reflects essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. It is proposed that these categories - IIIA1, IIIA2, IIIB - be retained as Categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by nongenotoxic mechanisms and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in Category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose-response relationships and toxicokinetics, and for which risk at low doses can be assessed are classified in Category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for Category 4 (1,4-dioxane) and Category 5 (styrene) are presented.

Assignment of skin notation for MAK values and its legal consequences in Germany.

Assignment of skin notation for MAK values and its legal consequences in Germany.

List of MAK and BAT Values 1996 Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area Report No. 32. Deutsche Forschungsgemeinschaft. Authorized by H. Green. VCH Verlagsgesellschaft mbH, Weinheim, Germany. 1996. xxii + 180 pp. 17 × 24 cm. ISBN 3-527-27572-X. DM 64.00 (pbk).

ADVERTISEMENT RETURN TO ISSUEPREVBook ReviewNEXTList of MAK and BAT Values 1996 Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area Report No. 32. Deutsche Forschungsgemeinschaft. Authorized by H. Green. VCH Verlagsgesellschaft mbH, Weinheim, Germany. 1996. xxii + 180 pp. 17 × 24 cm. ISBN 3-527-27572-X. DM 64.00 (pbk).Cite this: J. Med. Chem. 1997, 40, 25, 4161–4162Publication Date (Web):December 5, 1997Publication History Published online5 December 1997Published inissue 1 December 1997https://doi.org/10.1021/jm9705667Copyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views42Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlineGet e-AlertsSUBJECTS:Cells,Environmental pollution,Mixtures,Safety,Toxicology Get e-Alerts

Book Reviews : List of MAK and BAT values 1996 Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area. Report No. 32 VCH, Weinheim, Germany, 1996, 180pp., DM64.00

Book Reviews : List of MAK and BAT values 1996 Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area. Report No. 32 VCH, Weinheim, Germany, 1996, 180pp., DM64.00

Book review: H. GREIM (ed.) Occupational Toxicants Critical Data Evaluation for MAK values and Classification of Carcinogens VCH Verlaggesellschaft, Weinheim, Germany and VCH Publications, New York, 1996; Vol. 7 350 pp., DM 168.0

Journal of Applied ToxicologyVolume 17, Issue 2 p. 143-144 Book Review Book review: H. GREIM (ed.) Occupational Toxicants Critical Data Evaluation for MAK values and Classification of Carcinogens VCH Verlaggesellschaft, Weinheim, Germany and VCH Publications, New York, 1996; Vol. 7 350 pp., DM 168.0 L. Magos, Corresponding Author L. Magos BIBRA International, Carshalton, SurreyBIBRA International, Carshalton, SurreySearch for more papers by this author L. Magos, Corresponding Author L. Magos BIBRA International, Carshalton, SurreyBIBRA International, Carshalton, SurreySearch for more papers by this author First published: 04 December 1998 https://doi.org/10.1002/(SICI)1099-1263(199703)17:2<143::AID-JAT414>3.0.CO;2-RAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue2March 1997Pages 143-144 RelatedInformation