1. The knowledge has been documented for decades
Save PDFComplete document as PDF, The Overlooked Ingredient_Expert Analysis_V1.10_EN.pdf, 1.6 MB
A. The overlooked issue
The 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 overview lists the milestones evaluated in this expert analysis; the evidence is given in the sections indicated.
| Year | Source | Documented content |
|---|---|---|
| 1939 | US patent US 2,176,687 (Udy) [1] | Deliberate formation of calcium and sodium chromate from a chromium source, lime or soda respectively, and oxygen (Section 7). |
| 2002 | Paoletti, the German research centre Forschungszentrum Karlsruhe [50] | Calcium chromate from chromium oxide and calcium oxide between 500 and 850 °C in waste incineration, depending on the oxygen supply (Section 21). |
| 2004 | Vehlow, Paoletti, Seifert, Sirini [51] | Presentation of the results, including thermogravimetry on Cr₂O₃ and CaO with the product CaCrO₄ (Section 21). |
| 2010/2011 | Toshiba, JP2011232021A [26] | Calcium chromate at the interface between stainless steel and calcium-containing thermal insulation; ceramic separating layer as a prevention approach (Section 11). |
| 2015 | Sayano et al. [11] | CaCrO₄ and Na₂CrO₄ identified experimentally at the interface between chromium-containing metal and thermal insulation material (Section 10). |
| 2019 | Manufacturer correspondence [52] | Calcium from the insulation material reacting with chromium-containing stainless steel named as the cause; occurrence in all engine types (Section 16). |
| 2019 | Energy UK, Hexavalent Chromium Safety Bulletin Summary [92] | Calcium-containing product, temperatures above 300 °C and chromium-containing steel as the three conditions; presence assumed at all power station sites; at the same time a reference to WD-40 for binding and wiping off (Section 26). |
| 2019 | The German Environment Agency (UBA) [44] | Cr(VI) in all 25 model ashes from cremation furnaces examined (Section 23). |
| 2019 | European BAT reference document for waste incineration [34] | Hexavalent chromium as a problematic substance with regard to leaching from bottom ash (Section 22). |
| 2020/2021 | Caterpillar; Caterpillar Energy Solutions / Zeppelin [12, 13] | Cr(VI) findings on exhaust systems and exhaust insulation; French translation of the bulletin and German-language circular (Section 16). |
| 2023 | Rockwool, European ProRox instruction [16, 24] | Cr(VI) deposits after high-temperature use, cancer hazard and protective measures during removal (Section 16). |
| 2023 | , [25] | Chromium-containing steel, calcium for example from insulation material, oxygen and temperatures above 400 °C (Section 16). |
| 2023 | MAN Truck & Bus SE, service bulletin 8339SM [14] | Calcium chromate named; exclusively calcium-free pastes for assembly work (Section 16). |
| 2025 | Frenzelit, TechInfo 28 [15] | Calcium oxide fractions of its own insulation materials; contribution of its own products to Cr(VI) formation under the conditions stated (Section 16). |
| 2025 | , ; , [22, 23] | Cr(VI) formation on hot exhaust components; confirmed contamination in the engine compartment (Section 20). |
| 2025 | Passeron et al., France [5] | Colorimetric rapid tests miss Cr(VI) detected by laboratory analysis (Section 19). |
| 2026 | The German TRGS 561, version of 4 May 2026 [19] | Alkali/alkaline earth metal oxides from insulation materials or assembly pastes as an influencing factor; protective measures where chromium(VI) exposure cannot be ruled out (Section 6). |
| 2026 | The German statutory accident insurance institution BG ETEM [2] | Formation of carcinogenic chromates at steel temperatures of approximately 350 to 800 °C due to insulation materials or assembly pastes containing alkali and alkaline earth metals (Section 11). |
Anyone who today combines, maintains or disposes of chromium-alloyed hot components with alkaline insulation materials is therefore not relying on an open research question, but on a reaction pathway that has been described over decades and confirmed several times.
Sources cited in this section
- 1.Udy, Marvin J.: Chrome Alloy Making, US Patent 2,176,687; filed 22 January 1938, granted 17 October 1939. Relevant passages: description, printed pages 2-3; claims 22-26, printed page 7. Patent copy
- 2.BG ETEM: Mögliche Chrom(VI)-Exposition, last amended 3 August 2026.
- 5.Passeron, J.; Maisant, S.; Patrascu, C. et al.: Évaluation par mesures atmosphériques, surfaciques et biologiques de l’exposition professionnelle au chrome VI via une équipe référente en toxicologie en SPST. Références en Santé au Travail, TF 329, September 2025. Submitted study
- 11.Sayano, A.; Kanno, H.; Inagaki, S.; Takahashi, M.; Yoshida, M.: The formation of Cr(VI) compound at the interface between metal and heat-insulating material and the approach to prevent the formation by sol-gel process. Journal of the Ceramic Society of Japan 2015, 123, 677-684. DOI: 10.2109/jcersj2.123.677. Submitted study
- 12.Caterpillar: Hexavalent Chromium has been detected in certain Caterpillar Engines, Technical Information Bulletin M0116139-01, 1 June 2020; submitted French translation. Submitted bulletinAvailable to the author, not publicly retrievable.
- 13.Caterpillar Energy Solutions GmbH / Zeppelin: Technisches Rundschreiben 2175/00 DE: Sechswertiges Chrom (Cr6, CrVI), 23 August 2021. Submitted circularAvailable to the author, not publicly retrievable.
- 14.MAN Truck & Bus SE: Service-Mitteilung 8339SM: Auftreten von hexavalenten Chrom-Cr(VI)-Verbindungen im Betrieb, 13 December 2023. Submitted service bulletinAvailable to the author, not publicly retrievable.
- 15.Frenzelit GmbH: TechInfo 28: Chromium(VI)-Formation at High Temperature, Status August 2025, V2-ABE-MSK/08.25/de. Submitted English version.Available to the author, not publicly retrievable.
- 16.Rockwool Technical Insulation: Hinweise zur sicheren Verwendung: ProRox WM Drahtnetzmatten mit Edelstahl-Drahtgeflecht (SW) und/oder Edelstahl-Steppfaden (S), Version 1, 1 May 2023. Submitted product informationAvailable to the author, not publicly retrievable.
- 19.TRGS 561: Tätigkeiten mit krebserzeugenden Metallen und ihren Verbindungen, version of 4 May 2026; sections 3.3.4 and 5.9.3 as well as 4.1/4.2. Official publication or authority copy.
- 22.: Service Information: Work on component parts conducting exhaust gas with chrome(VI). , 7 August 2025. Submitted service information, one page.Available to the author, not publicly retrievable.
- 23.: Chromium VI Safety Information. Aftersales Bulletin , 27 August 2025, three pages. Submitted version; internal marking SECRET.Available to the author, not publicly retrievable.
- 24.Rockwool B.V. / Technical Insulation: Safe Use Instruction Sheet: ProRox WM versions with stainless steel mesh and/or stitching wire. Issue 1 January 2025, version 1.1; sections 2.3 and 8; comparison with the submitted 2023 version. Accessed 7 October 2026.
- 25.: Technical Instruction: Cr6-Reduction, , Index 1, released 31 May 2023; in particular chapter 2 and the overview of addressees. Submitted document, seven pages.Available to the author, not publicly retrievable.
- 26.Toshiba Corp.: Thermal apparatus structural member, and method of manufacturing the same. JP2011232021A, priority 8 April 2010, published 17 November 2011; description, prior art and prevention approach. Japanese patent family; English machine translation on Google Patents. Submitted translation additionally checked against the Japanese original, in particular Example 1 and the comparative examples.
- 34.European Commission / JRC: Best Available Techniques (BAT) Reference Document for Waste Incineration, 2019, JRC118637. Evaluated officially indexed passage: leaching of bottom ash, explicit mention of hexavalent chromium. No complete comparison of the document.
- 44.Haas, J. / Schack-Kirchner, H. / Lang, F.: Evaluierung von Ausmaß und Ursachen einer Schadstofffreisetzung aus Urnen in Bestattungswäldern. Umweltbundesamt TEXTE 142/2019. In particular model ashes/extraction and page 72: oxygen contact, inert post-treatment and reference to Brill (2002).
- 50.Paoletti, Francesca: Behavior of oxyanions forming heavy metals in municipal solid waste incineration. Dissertation, University of Stuttgart; Forschungszentrum Karlsruhe, Wissenschaftliche Berichte FZKA 6755, 2002. In particular summary pp. II and V, pp. 39-41, Table 6.3 (p. 78).
- 51.Vehlow, J.; Paoletti, F.; Seifert, H.; Sirini, P.: Behaviour of oxyanions forming heavy metals in waste combustion. WTERT Fall Meeting, Columbia University, New York, 7/8 October 2004.
- 52.: manufacturer correspondence to the author on chromium(VI) deposits on exhaust gas insulation, August 2019. Available to the author.Available to the author, not publicly retrievable.
- 92.Energy UK, London: Hexavalent Chromium Safety Bulletin Summary, September 2019; summary of the safety bulletins issued to the British electricity generation sector for the Generation Health and Safety Forum.Available to the author, not publicly retrievable.