32. Order of magnitude: a thought experiment

This 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 which it would have to be examined whether a chromium(VI) contamination can be ruled out. The population figures come from public manufacturer data, from fleet statistics and from plant registers. The conversions and interval assumptions are marked in the text.

Population figures from public sources

For the 3500 series, Caterpillar states a field population of 190,000 engines and 3 billion operating hours, with more than 35 years of production, with applications in mining, rail, power generation, oil and gas and shipping. As at September 2016. [134]

For the mtu series 2000 and 4000, Rolls-Royce Power Systems names more than 100,000 engines sold, of which 52,000 of the 4000 series and more than 65,000 of the 2000 series, together more than 320 million operating hours, with applications in generating sets, dump trucks, yachts, ferries and locomotives. As at 2021. [135]

INNIO reports an active installed base of the Jenbacher and Waukesha brands of around 44 GW as at 31 December 2025, after 42 GW in the previous year, with 3.4 GW delivered in 2025. The company does not give unit numbers. At an assumed average unit output of 1.0 to 1.5 MW, that corresponds to 29,000 to 44,000 engines. [136]

For the energy sector, Wärtsilä states 79 GW of power plant capacity delivered in 180 countries, of which 40.8 GW in the Middle East and Asia, 19.7 GW in the Americas, 10.9 GW in Europe and 7.6 GW in Africa. The marine business is not included in this. The company does not give unit numbers. [137]

On its own product page, GE Vernova names more than 7,000 gas turbines with more than 800 GW of installed capacity in over 120 countries and states that it accounts for approximately half of the installed gas turbine base worldwide. This gives a worldwide fleet of the order of 14,000 gas turbines. Individual series for comparison: 7F with more than 950 installed units and around 175 GW, 9F with more than 400 units in more than 40 countries, LM6000 with more than 1,500 units sold. [138]

The Global Coal Plant Tracker reports more than 2,200 GW of coal capacity in operation, with a reporting threshold of 30 MW. At an average unit size of 300 MW, that amounts to around 7,300 units with a steam turbine and with live steam and reheater lines made of creep-resistant chromium-alloyed steels. The Global Oil and Gas Plant Tracker lists 16,559 oil and gas power plant units, including planned and retired ones, with a reporting threshold of 50 MW and, in the European Union and the United Kingdom, of 20 MW. [139, 140]

The world merchant fleet comprises around 109,000 ships of 100 gross register tons and above, each with an insulated exhaust system for main and auxiliary engines. [141]

For the European Union, the ACEA reports 6,162,673 trucks over 3.5 tonnes with a diesel share of 96.3 per cent and 699,238 buses with 88.7 per cent, with an average age of the truck fleet of 14.0 years. For Europe including EFTA and the United Kingdom the figures are 7,072,260 trucks and 852,180 buses, plus 302,281,600 passenger cars. The average age points to the Euro V and Euro VI emission stages, that is, to vehicles with an oxidation catalyst, a particulate filter and an SCR section, all of them insulated hot components made of chromium-alloyed steel. [142]

In waste incineration, Europe lists 498 plants, as at 2022, among them France 116, Germany 91, the United Kingdom 57, Italy 36 and the Netherlands 12. For the United States, 75 plants are reported. At the end of 2023, China operated 975 plants with 2,151 incineration lines and a capacity of 327 million tonnes per year. In the 2024 financial year, Japan listed 991 plants, 415 of them with power generation. In these four regions together that comes to 2,539 plants. Applying the Chinese ratio of 2.2 lines per plant, the number of incineration lines is around 5,600. [144, 145, 146, 147]

Occasions per year

For gas engines, a Jenbacher service company names intermediate maintenance every 10,000 operating hours and overhauls at 30,000 and 60,000 operating hours. At a conservatively assumed 5,000 operating hours per year, that gives one overhaul every six years, and thus 4,800 to 7,300 events per year for the fleet named above. [148]

For coal fired units, an overhaul every two years gives around 3,650 events per year. For incineration lines, one overhaul per line and year gives around 5,600 events. For ships, one measure on the exhaust section every two and a half years gives around 44,000 events. For commercial vehicles in the European Union, one workshop visit per vehicle and year gives around 6.9 million visits, and at 250 working days about 27,000 per working day.

For passenger cars, Deutsche Automobil Treuhand reports 0.35 repairs per vehicle and year; in 2022 the figure was 0.40 and in 2019 still 0.51; maintenance and inspections are not included in this figure. Related to the 255,999,373 passenger cars in the European Union, that amounts to around 90 million repairs per year, or 358,000 per working day. What share of these involves the engine compartment or the exhaust system has not been collected. [143, 142]

The assumptions in this section

The assumptions made are an average unit output for gas engines, an average unit size for coal fired power plants, the number of incineration lines per plant outside China, the annual operating hours, the overhaul interval for power plants, incineration lines and ships, and the workshop frequency for commercial vehicles. The manufacturer figures from Caterpillar and Rolls-Royce are cumulative field and sales figures and not an active fleet. Not every application named carries insulation in the temperature window concerned. The segments are not added together, because they have different counting units and overlap; the marine engines, for example, are already partly included in the manufacturer figures.

What follows from this

The events assumed in the four industrial segments add up to about 58,000 to 61,000 per year, before any deduction for the overlaps. In addition there are around 6.9 million workshop visits for commercial vehicles and around 90 million passenger car repairs in the European Union, whose relevant share is not quantified.

What is up for assessment is therefore not an isolated occurrence. The release takes place daily, in engine compartments, on vehicles, on turbines, in power plants and in incineration plants, in a number that cannot be quantified, and for the most part unnoticed. It is triggered by the substance that gives this analysis its title.

In Germany, each of these occasions would be an activity within the meaning of section 5.9.3 paragraph 5 of the German TRGS 561. In the other legal systems considered, the duty of assessment before work begins follows from the provisions named in section 25. None of these bodies of rules contains a threshold below which the protective regime would not apply. An exclusion of the contamination cannot be demonstrated reliably with the widespread methods, because the colorimetric rapid test can come out false negative and no standardised method exists for the insulation material matrix (Sections 17 and 19). [19]