5. Why the issue is not recognised
Several 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.
The collective term “chromium(VI)”
People speak in general terms of “chromium(VI)”. The term is associated with industrially manufactured compounds; the calcium and sodium chromates formed in one's own operations do not feature in this picture (Section 3).
Perception of the industrially manufactured form alone
Industrially manufactured chromates are subject to authorisation, monitoring and labelling. Chromates formed in situ have no manufacturer, no labelling and no safety data sheet describing the condition after use. The safety information for an insulation material describes the as-delivered condition; an unclassified insulation material may be contaminated with newly formed hazardous substances after use (Sections 16 and 25).
Test objective: material resistance
Compatibility tests of insulation materials with chromium assess the resistance of the fibre. An outwardly resistant fibre may, however, carry a small quantity of a highly hazardous reaction product. If Cr(VI) is not determined, the test does not answer the hazardous substance question (Section 12).
The formation pathway as “not traceable”
Individual manufacturer documents declare the formation to be “not fully” understood or “generally not yet traceable” and refer to external sources such as spare parts, maintenance materials or operating environments. The exposure thus appears to be an isolated case, although the formation pathway has been published (Section 16).
Rapid test philosophy
Protective measures are linked to visible yellow deposits and positive rapid tests. If the colour is absent or the test is negative, the finding is regarded as unremarkable. The French field study shows that colorimetric rapid tests miss Cr(VI) detected by laboratory analysis (Section 19).
“Neutralisation” and WD-40
The recommendation to “neutralise” chromium(VI) and the use of WD-40 give the impression that the problem can be solved on site. “Neutralisation” is a reduction to chromium(III), which is almost complete only under favourable conditions; for WD-40, a reducing effect has been experimentally refuted (Section 26).
“Asbestos-free” as a mark of harmlessness
Asbestos substitution eliminated the asbestos fibre, not necessarily the reactive material system of chromium-alloyed hot component and basic insulation. “Asbestos-free” is no statement as to whether an insulation material on chromium-alloyed hot components contributes to chromate formation (Section 15).
Environmental assessment instead of activity assessment for combustion residues
For ashes, the focus is on the environmental assessment via leaching, for example in the European BAT reference document. It does not answer the question of exposure during overhaul, boiler opening, cleaning and ash handling. Field observations at European waste incineration plants show that protection against chromate exposure is implemented at best partially (Section 22).
Whether, in view of this body of sources, the formation pathway ought not to have been seen is the question this expert analysis raises.