31. On the choice of the regulations cited

This 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 active in occupational safety and environmental protection. And the German TRGS 561 expressly describes the application case dealt with here, with thermally stressed chromium-alloyed industrial components, with alkali and alkaline earth metal oxides from insulation materials and assembly pastes, and with a catalogue of measures of its own. [19]

It does not thereby set stricter standards than European law. It spells out the approach of Directive 2004/37/EC for this case. For more than twenty years the Directive has required that, in all activities with the possibility of exposure, the nature, degree and duration of the exposure be determined, taking into account the further routes of exposure including absorption into or through the skin. It applies in all Member States. [18]

In practice the assessment relies predominantly on air measurements, because the binding values are laid down as air concentrations. For the hazard from skin contact, Germany has in the TRGS 401 an assessment procedure of its own, which stands alongside air measurement. [99]

In this respect chromium(VI) compounds are unusual. The MAK and BAT value list 2026 gives them the skin absorption marking H, the sensitisation marking Sh, carcinogenicity category 1 and germ cell mutagenicity category 2. Under table 2 of the German TRGS 401, the combination of skin absorption and classification as carcinogenic category 1 gives a high hazard for every type of contact, with no threshold for duration or area. Calcium and sodium chromate are in addition classified as very toxic to aquatic life with long lasting effects. Four levels of assessment therefore stand side by side, inhalation, dermal, oral and environmental. Asbestos carries neither a skin-related hazard statement nor a hazard to water. [102, 99, 98]

For air measurement a practical limit follows from this. Pockets of chromate-containing dust in insulation, at flanges and in cavities are released only when they are handled. A general measurement of room air does not capture them. The German TRGS 561 therefore starts from the activity in section 5.9.3 paragraph 5 and requires the minimisation of dust generation and dust spread, extending to the covering of grating, together with a type 5 chemical protective suit with hood, nitrile-coated textile gloves, eye protection, respiratory protection of at least FFP2 and, for activities of longer duration, half masks with P3 filters, as well as the disposal of contaminated disposable protective clothing. [19]

The same applies to chromate-containing ashes during overhaul inside incineration furnaces. Scaffolding is erected there, and the stainless steel components of the grate are not only walked on and inspected, but also surface treated, removed and replaced. From my own field work, elevated air contamination from chromium(VI) compounds during such work is known; the associated measured values are not public and are not reproduced here.

A single measurement is in any case not a suitable yardstick there, neither for exoneration nor for incrimination. The content of basic oxides in the material burned fluctuates, and it is not determined by the waste composition alone. Paoletti states the calcium oxide content in household waste as around 3 per cent and on this basis describes the formation of calcium chromate between 500 and 850 °C where the oxygen partial pressure is sufficient. In addition there is the addition of calcium-bearing sorbents in plant operation. With conditioned dry sorption this takes place downstream of the boiler, at flue gas temperatures of about 130 to 150 °C, with spray absorption using milk of lime between 140 and 200 °C, and thus outside the formation window. With direct desulphurisation, by contrast, calcium hydroxide or limestone powder is introduced into the combustion chamber at about 900 °C or into the downstream boiler passes at about 350 °C, in the documented application at dosing rates of 140 to 375 kilograms per hour. For the assessment of an overhaul it therefore has to be established which desulphurisation process the plant runs and at which point the sorbent is introduced. [50, 149, 150]

What the air measurement does not represent: the hand finding of the French field study

The French field study measures not only surfaces but also hands. Before removal the value lay below the limit of quantification of 40 ng, after removal at 45.4 ng, and the authors expressly record the contamination of the hands despite the disposable nitrile gloves worn. Disposable half masks FFP3 and a type 5 working coverall were worn in addition. In the same run the air values remained low, and the urine values of the eleven mechanics examined averaged 0.26 µg per gram of creatinine and thus lay below the biological reference value of 0.54. In this constellation the dermal exposure is represented neither by the air measurement nor by the biomonitoring. [5]

The glove is not the weak point here. The nitrile glove separates the skin from the substance; what remains open is the sleeve end, through which dust enters, and the moment of taking the gloves off, in which the contaminated outer side touches the palm. In practice the transition between glove and suit sleeve is therefore taped, as is the transition between suit and footwear. In protective suits of types 5 and 6, sealed seams and covered fastenings are among the product features, and the two taped transitions close the places that the product itself cannot close. The German DGUV Rule 112-189 states on this in general terms that only closed clothing fulfils the protective function, and for the risk of contamination it lists tightness as a requirement on the protective clothing. The authors of the French study draw the same direction from their finding and expressly recommend improving the protocols for removing personal protective equipment and for hand washing before and after wearing it. [5, 133]

The same investigation found traces of chromium(VI) of 0.01 to 0.2 mg/kg in the insulation materials sampled, and in one sample ceramic refractory fibres, which are classified as carcinogenic category 1B by inhalation. The remaining samples consisted of glass or silicate fibres. [5]

The direction of developments is shown by Australia. From 1 December 2026, Safe Work Australia will no longer set workplace exposure limits for non-threshold genotoxic carcinogens, chromium(VI) compounds included. The exposure limit is replaced by the obligation to eliminate exposure or to minimise it so far as is reasonably practicable. [58]