The Overlooked Ingredient

Contents

1. 1. The knowledge has been documented for decadesThe formation pathway of calcium and sodium chromate is not new. It has been documented in patent specifications, research work, manufacturer documents and regulations over more than eight decades. The following …
2. 2. The issue has reached EuropeIn addition, there are authorities, regulations and research in Europe: the German statutory accident insurance institution BG ETEM, the German TRGS 561, the German Environment Agency (UBA), the European BAT reference …
3. 3. The chromium(VI) misconception: collective term and individual compoundAsbestos was not simply asbestos either. In everyday language a distinction was made at most by colour, into white, brown and blue asbestos. Behind these lie different minerals: chrysotile, amosite and crocidolite, as …
4. 4. Fields of application and the chromates to be expectedThe following overview assigns typical fields of application to the insulation materials used there and to the chromates to be expected. What is decisive in each case is the combination of chromium-alloyed hot …
5. 5. Why the issue is not recognisedSeveral reasons for the lack of awareness can be identified from the documents evaluated. Each has a plausible explanation in itself; together they mean that the formation pathway is not looked for where it is obvious.
6. 6. Why it becomes an issueSince 4 May 2026, the German TRGS 561 has applied in a new version. Section 3.3.4 describes the subject matter, and section 5.9.3 names alkali/alkaline earth metal oxides from insulation materials or assembly pastes as …
7. 7. The 1938/1939 patent: calcium chromate as a deliberately produced reaction productUdy developed the process for producing low-carbon ferrochromium. The starting point was carbon-containing ferrochromium. This was roasted in finely divided form in air and treated with lime in the process. The patent …
8. 8. Sodium: accelerator, control agent and chromate formerThe patent explicitly names soda, i.e. sodium carbonate (Na₂CO₃), as an influencing factor. Soda accelerates and controls the oxidation to chromate. According to the patent specification, a sufficient addition of soda …
9. 9. The chemical core of the formation pathwayThe roasting process described in the patent specification is based on four factors:
10. 10. Direct experimental evidence: from the model mixture to the metal-insulation interfaceThe historical patent specification describes the reaction pathway. Four primary studies confirm it experimentally at different levels and close the chain of evidence from the model experiment to the realistic interface.
11. 11. From metallurgical roasting to high-temperature insulationThe historical patent specification describes a deliberately intensified metallurgical roasting. Its significance for insulation materials on chromium-alloyed hot components lies in the reaction chemistry: the groups of …
12. 12. Significance for E-glass fabric, calcium silicate, mineral wool and aerogel insulation systemsThe designation of a product class is not a statement about the chemical harmlessness of the individual product. What is decisive are the raw materials, fibres, carriers, binders and fillers actually used.
13. 13. The dilemma of the insulation material manufacturersCalcium oxide and sodium oxide are not additives that can be struck from a formulation like a colour pigment. Since the earliest glassmaking they have been constitutive components of the melt from which fibres are drawn …
14. 14. Gas-phase transport: Tatar/Gannon and van LeeuwenThe formation of a volatile Cr(VI) species at a hot chromium source, its deposition on cooler fibres and the formation of a calcium or sodium chromate are distinct reaction steps. They can occur side by side or in …
15. 15. The asbestos era, asbestos substitution and chrysotileCalcium silicate was not introduced in high-temperature applications only as a subsequent substitute after asbestos was phased out. The material class was already represented in the market for technical thermal and pipe …
16. 16. Manufacturer and operator warnings: documented state of industrial knowledgeThe scientific works do not stand in isolation. Manufacturers of engines, generating sets, insulation materials and mineral wool have taken up the issue in technical information, service bulletins and safety …
17. 17. Analysis: the method decides the findingThe determination of chromium(VI) is not an elemental determination but speciation analysis. What is measured is an oxidation state, and that state can change during sample preparation. What the instrument finally …
18. 18. Rules compared: one benchmark, five variantsFor all Member States, Directive 2004/37/EC in its current version applies as the overarching instrument. Since 17 January 2025 it sets a binding limit value of 0.005 mg/m³ for chromium(VI) compounds; before that 0.010 …
19. 19. Rapid test philosophy and the French field studyThe technical information from Caterpillar, MAN and in particular Rockwool partly follows a staged detection and response logic:
20. 20. Vehicle engines and engine compartmentsIn its 09/2019 data sheet, Morgan expressly promotes Superwool Plus Heat Shield for vehicle heat shields subject to vibration. It is a flexible calcium/magnesium silicate fibre mat, not a rigid calcium silicate board. …
21. 21. Combustion ashes and boiler depositsThe scope of investigation expressly covers the ash residues remaining on the grate, bottom ash, furnace residues and deposits on chromium-alloyed hot components, in addition to fly, filter and boiler ashes. These …
22. 22. State of knowledge in Europe on combustion residuesEuropean environmental literature also expressly names Cr(VI): in the 2019 European BAT reference document for waste incineration (JRC-BREF), it is listed alongside copper, molybdenum and zinc as a problematic substance …
23. 23. Cremations and other chromium-containing combustion materialsIn 2019, owing to legal restrictions, the German Environment Agency (UBA) investigated 25 model ashes from cremations of empty coffins in five cremation furnaces. All contained Cr(VI). In extraction with 0.01 M CaCl₂, …
24. 24. Health and environmental consequences of the chromatesThe reaction products are not only chemically relevant. The calcium and sodium chromates considered here are carcinogenic; skin contact, local effects on the skin and possible uptake must be assessed in addition to …
25. 25. Industrially manufactured or formed in situ: unequal controlIn regulations and in public perception, chromium(VI) compounds are considered almost exclusively in their industrially manufactured form, as the Udy patent describes it as the product of a targeted process. Strict …
26. 26. Supposed remedies: neutralisation, WD-40 and the “harmless” chromium(III)Several of the manufacturers named in this analysis recommend “neutralising” chromium(VI) residues and present this as a sufficient occupational safety and health measure. The term suggests that chromium(VI) can be …
27. 27. Chromium(III): the assumed final stateAll the methods treated in section 26 rest on the same assumption. That with the conversion of chromium(VI) into chromium(III) the dangerous part of the process is at an end. This section examines the assumption against …
28. 28. Our own field findingsThe basis of this expert analysis is not other people's documents alone. Since 2019 we have been carrying out our own investigations in the field, in part ourselves and in part through commissioned third parties, and …
29. 29. What can still be investigated and what is no longer openIn the individual plant case, there may be a need for investigation regarding kinetics, local oxygen and moisture conditions, the influence of temperature cycles, surface chemistry or the quantitative ratio of …
30. 30. Legal consequences of non-complianceThe preceding sections deal with the formation pathway, the state of the evidence and the duties. This section deals with what happens if those duties are not met. The account is confined to the law in force and gives …
31. 31. On the choice of the regulations citedThis analysis frequently cites German regulations, in particular the TRGS 561 and the Hazardous Substances Ordinance. There are two reasons for this. I work from Germany, together with a further chromate expert who is …
32. 32. Order of magnitude: a thought experimentThis section does not calculate how many installations are contaminated. That figure has not been collected anywhere, and any statement about it would be invented. What is calculated is how often the situation arises in …
33. 33. The duties in FranceFrance is a member of the European Union and has transposed Directive 2004/37/EC into the Code du travail. The case treated here is not specifically named there either; the duties are framed without naming a specific …
34. 34. The duties in SwitzerlandSection 31 names the reasons why this analysis cites predominantly German rules. For companies in Switzerland, this names the reference and not the applicable body of rules. Switzerland is not a member of the European …
35. 35. The duties in GermanySection 31 names the reasons why this analysis cites predominantly German rules. This section brings together the German provisions in force in one place and gives the source for every statement. In doing so it repeats …
36. 36. The duties in the European UnionThe national bodies of rules of the Member States transpose Union law. This section brings together what Union law itself requires, and in doing so separates occupational safety and health law from chemicals law and …
37. 37. The duties in the NetherlandsThe Netherlands is a Member State of the European Union and has transposed Directive 2004/37/EC into the Arbeidsomstandighedenbesluit. The case of application dealt with here is not named as such there either. This …
38. 38. The duties in the United KingdomThis section brings together the British body of rules in one place, as the three preceding sections do for Germany, the European Union and the Netherlands. Since 1 January 2021 the United Kingdom has no longer been …
39. 39. Appendix: insulation materials with basic oxides and where they are installedThe following commercially available insulation materials contain the basic oxides described, which can trigger thermochemical in-situ formation of the chromium(VI) compounds described. These are not assumptions, but …
40. 40. ConclusionCalcium chromate and sodium chromate are chromium(VI) compounds that can be deliberately formed under alkaline-oxidising thermal conditions. The historical patent specification and the experimental interface findings …