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1. What is chromium-6?

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What is chromium-6? Explanation, risks, legislation and testing #

Chromium-6, also written as Cr(VI), is an oxidation state of the metal chromium that has been useful in industry and engineering, but is also known as a carcinogenic hazardous substance. Workers can become ill from it if they work with it without sufficient protection. Source: RIVM

On this page you can read in plain language what chromium-6 is, where you encounter it, what risks it poses, what the law requires and how you can have it investigated and managed in a reliable way. We link this to the practical services and products of SEEF and refer to official standards and methods.

1. What is chromium-6? #

Chromium is a metal that can occur in different “forms.” These forms are called oxidation states. Chromium-6 is the oxidation state in which chromium has six positive charges, which is why we call it Cr(VI). Source: Wikipedia

Key points:

  • Chromium-6 almost always occurs as a chromium-6 compound, for example as chromate or dichromate.
  • It is never present as “loose” chromium-6 in a material, but is bound to other substances, such as zinc, lead or calcium.
  • These compounds often provide good corrosion protection or are a good and stable pigment such as lead chromate (yellow), but can also pose significant health risks.

Short simple explanation #

You can think of chromium-6 as an “aggressive mode” of the metal chromium. In this state, it reacts much more easily with other substances. Inside the body it then converts to the more stable form chromium-3 (Cr(III)). It is precisely this reactive property that can cause damage to cells and DNA.

More background on the chemistry of Cr(VI) can be found in our articles:

2. Where do you find chromium-6? #

Chromium-6 is best known from:

  • Old paint systems and coatings on steel, concrete and wood, for example bridges, railway bridges, fences, vehicles, military objects, but also on window frames, windows and doors of residential buildings.

  • Corrosion-resistant primers and paint layers in, among others, aviation and industry; strontium chromate has been widely applied on aluminium surfaces.

  • High temperature applications, such as insulation around gas turbines, CHP installations and other process installations, where Cr(VI) can form through a reaction between chromium in steel and calcium-containing insulation. But also in waste incineration plants, biomass power stations or other combustion installations where alkali and alkaline earth metals may be present.

  • Welding and grinding activities on stainless steel or high-alloy steel, where chromium-6 can occur in welding fumes and grinding dust.

In our knowledge base category all about Cr(VI) compounds you will find more detail on applications, including in:

 

3. Why is chromium-6 dangerous for our health? #

All chromium-6 compounds are classified by the International Agency for Research on Cancer (IARC) as group 1: carcinogenic to humans.

Important health effects mentioned in research:

  • Lung cancer from prolonged inhalation of chromium-6-containing dust or fumes
  • Nasal and paranasal sinus cancer
  • Asthma and other respiratory complaints
  • Skin problems such as skin irritation and allergic contact eczema from skin contact

 

The risks depend among other things on:

  • The concentration of chromium-6 in the air or on the surface

  • The duration and frequency of exposure

  • The route of exposure: inhalation, skin contact or ingestion

  • The protective measures that have or have not been taken

RIVM and other authorities provide extensive information about diseases associated with chromium-6.

 

4. Legislation and limit values for chromium-6 #

In the Netherlands, chromium-6 has been designated as a carcinogenic substance. Employers must comply with strict requirements from, among others, the Working Conditions Decree and regulations on hazardous substances. Because it is a carcinogenic substance, additional rules apply that employers must comply with. The Netherlands Labour Authority also actively enforces these rules.

Key points:

  • The statutory limit value for chromium-6 compounds in the breathing zone of workers is 1 microgram per cubic metre (1 µg/m³) as an 8-hour TWA

  • In the European Union a less strict workplace limit value of 5 µg/m³ applies, but in the Netherlands the lower, stricter limit value is leading. The amendment in the European Union came into force on 17 January 2025, but had been announced years earlier. This can be found in Directive 2017/2398

  • Chromium-6 compounds are classified under the European CLP Regulation as carcinogen category 1A or 1B

  • Under REACH and ECHA, an increasing number of applications of Cr(VI) are being restricted or completely banned, with a further tightening trend towards a total ban for many applications.

 

In addition to complying with limit values, employers must, in accordance with the occupational hygiene strategy (STOP strategy) and the rules on responsible commissioning, assess whether materials contain chromium-6 and what control measures are required. Our own dataset shows that chromium-6 compounds are present in as many as 42% of existing paints and coatings. Everyone working on existing coatings must therefore include in their risk assessment that exposure is possible, which also leads to an obligation to investigate.

In our knowledge base you will find a separate page on:

 

5. How can you be exposed to chromium-6? #

Employees can come into contact with chromium-6 in various ways:

  • Inhalation of dust or fumes

    • Sanding, grinding or blasting (processing) of old paint layers.
    • Welding or cutting stainless steel or chromium-containing steel.
    • Working on hot installations with Cr(VI) formation in insulation.

  • Skin contact

    • Direct contact with dust or paint residues on the skin, although uptake from paint residues is less likely because most Cr(VI) compounds used in paint are poorly soluble in water. Cr(VI) compounds that form under thermal insulation, for example, are soluble in water, and skin absorption is a significant risk there.
    • Clothing or gloves contaminated with chromium-6-containing dust.

     

  • Ingestion

    • Not washing hands before eating, drinking or smoking

    • Contamination of surfaces in break rooms or vehicles

     

SEEF carries out both exposure measurements for Cr(VI) compounds in air and surface measurements, so that you get a realistic picture of the actual risks in practice. Surface measurements can be carried out using wipe samples, ipe samples, which we then analyse in our laboratory. If you want to carry out a chromium-6 clearance, for example, you can also measure a wipe sample directly on site with our SEEF TK01 Chroom-6 Testkit. But also paint samples to determine the possible risks during demolition or processing.

6. How do you know chromium-6 is present? #

Chromium-6 has:

  • No typical odour
  • No fixed colour that you can always recognise
  • No simple visual indication

    You cannot therefore reliably see or smell chromium-6. Measurements are necessary.

 

A good approach consists of several steps:

  1. Document and historical research

    • Drawings, specifications, paint specifications
    • Maintenance history of objects and installations

     

  2. Risk assessment based on application

    • Year of construction, type of application (paint, insulation etc.), sector (for example defence, rail, bridges, power plants). Contact SEEF to discuss this for your situation.

     

  3. Indicative measurements

    • Quick on-site tests to get an initial picture are sometimes used, depending entirely on the application. In paint, you can only reliably detect Cr(VI) through laboratory analysis. It is therefore advisable to agree on a good sampling strategy in advance and to carry this out and document it carefully. For Cr(VI) compounds under thermal insulation, for example, it may be useful to first test with a quick test such as the SEEF ST01, but these are very unreliable for a negative test result. The same applies to other suppliers of such quick tests. A negative test result must therefore always be followed by a reliable laboratory analysis.

     

  4. Laboratory analysis

    • Validated, quantitative analysis for reliable decision-making. But be aware here too, as laboratories use different methods. For example, there is NEN5617:2022,, developed specifically for measuring Cr(VI) compounds in dry paint samples. However, this is semi-quantitative, meaning that a reliable quantity of Cr(VI) cannot be determined. This is due to interfering metals such as zinc and aluminium, and a concession in the digestion process because of those interfering metals. Another widely used method is NEN-EN-ISO 15192:2021, which was developed for waste and soil and is therefore also unsuitable for measuring Cr(VI) compounds in dry paint. This method also has significant matrix interference from metals such as zinc and aluminium, which are common in the paint matrix.

    • SEEF has a patented technique for the digestion phase, which enables us to determine the concentration of Cr(VI) present in various matrices much more accurately.

On the following pages we explain these topics further:

 

7. Test and analysis methods for chromium-6 #

7.1 Quick indicative tests on site #

For certain situations a quick initial indication is useful. For example with insulation around turbines and CHP engines. SEEF offers among others:

  • ST01 chromium-6 swab test for insulation and (turbine) engines

    • Intended as a quick first indication, but very unreliable for a negative test result.

    • Also not permitted by the Netherlands Labour Authority as a reliable method. Read at the bottom of this page: “To determine yourself using an approved method whether the surface contains chromium. There must be representative sampling, suitable preservation and conditioning, suitable analysis and quality assurance. There are some quick tests on the market (‘cotton swab test’), these are insufficiently reliable to use as the only test.”

    • Buy this quick test here.

Important to emphasize again:

  • A positive result means that chromium-6 may be present

  • A negative result certainly does not rule out the presence of chromium-6!

  • In case of doubt, additional analysis with the TK01 test kit or a laboratory analysis is always required.

More explanation can be found on the knowledge base page ST01 chroom-6 swab test.

 

7.2 Reliable laboratory analysis #

For policy, contracts, legal discussions and health assessment, quantitative laboratory analysis is essential. Important official standards include:

  • NEN 5617:2022
    Semi-quantitative determination of chromium-6 in dry paint samples by alkaline digestion, clean-up and UV detection.

  • ASTM D6966-18
    Standard for collecting dust via wipe sampling on surfaces, so that samples are suitable for analysis of metals and Cr(VI).

  • SEEF DP01 – Cr(VI) determination in dry paint samples
    Proprietary method based on NEN5617:2022, in which SEEF’s patented technique is used during the digestion phase to stabilise the Cr(VI) and prevent reduction by metals such as zinc or aluminium.

 

SEEF aligns with these standards by:

    • Use of wipe samples in accordance with ASTM D6966-18 with our WS01 wipe sample set chromium-6.

  • Application of a patented analysis technique for Cr(VI), which greatly reduces interference from metals such as zinc and aluminium.

  • Analyses within an ISO/IEC 17025-compliant quality framework, so that results are reproducible and defensible.

 

7.3 TK01 chromium-6 test kit: reliable detection on site #

The TK01 chromium-6 test kit has been developed to reliably detect chromium-6 on site in, among others, insulation, lubricants, anti-seize pastes and stainless steel components. The kit uses SEEF’s patented detection technique and can analyse up to six samples simultaneously.

Applications:

  • Research around gas turbines, CHPs and other installations.

  • Clearance measurements on site.

Important: for quantitative substantiation (for example for an exposure or risk analysis) we always recommend supplementing with laboratory analysis.

 

8. How SEEF helps at project, management and organisational level #

Chromium-6 is not purely a technical issue. It affects policy, organisation, communication and day-to-day operations.

8.1 Projectlevel #

At project level SEEF assists with:

  • Preliminary research and risk assessment

    • Analysis of drawings, specifications, material and insulation specifications.

  • Inventory and sampling on site

    • Wipe samples in accordance with ASTM D6966-18.

    • Material samples of paint, insulation and dust.

    • Air measurements in the breathing zone of employees or stationary measurements to establish the background concentration.

  • Interpretation of measurement results

    • Linking to limit values and health-based advisory values.

  • Practical advice for the work

    • Choice of working methods and extraction.
    • Personal protective equipment (PPE).
    • Clearance criteria after remediation or maintenance

More on this can be found in Exposure measurements for Cr(VI) compounds and Why Cr(VI) in Insulation Requires a Different Analysis

 

8.2 Management and organisational level #

At organisational level SEEF supports among others with:

  • Drawing up or tightening hazardous substances policy with specific attention to chromium-6

  • Integrating chromium-6 into the risk assessment, including a multi-year control plan

  • Setting up exposure registration and retention periods in accordance with legislation

  • Embedding in contracts and tenders

    • Requirements for inventory and research
    • Requirements for contractors and executing parties

  • Training and awareness for management, HSE, project managers and operators

  • Management reports suitable for board, works council and supervisory authorities

An overview of our services can be found in SEEF products and services and about SEEF: who we are and what we do.

 

9. What to do if you suspect chromium-6 #

If you notice that chromium-6 may be present in a project or installation while you have already started work, here is a practical step-by-step plan:

  1. STOP and assess the situation

    • Avoid unnecessary dust generation
    • Put temporary measures in place such as using suitable PPE and cordon off the work area

  2. Gather information

    • Year of construction, maintenance history, coatings used, insulation data etc.

  3. Call in a specialist

    • Have a risk assessment drawn up and, if necessary, a targeted sampling plan

  4. Have measurements carried out

    • Quick indication with ST01 and/or TK01 where appropriate
    • Laboratory analyses for definitive substantiation; SEEF can also carry this out quickly with a maximum turnaround time of 5 working days in our own laboratory.

  5. Translate the results into policy and work plan

    • Working methods, technical measures, organisational measures, PPE, shielding, cleaning and monitoring.

  6. Record measures and results

    • In the risk assessment, work plans, completion file and exposure register. Ensure this is also embedded at organisational level and that the risk assessment is updated accordingly.

SEEF can support you throughout this entire chain, from the first question to a workable solution and embedding of results into policy.

 

10. Frequently asked questions about chromium-6 #

1. Is chromium-6 always dangerous at any level of exposure? #

The risk depends on the amount and duration of exposure and the way in which you absorb chromium-6. Brief, low exposure will carry a smaller risk than prolonged exposure in a workplace without protective measures. Because chromium-6 is carcinogenic, the principle applies in work situations that exposure must be reduced as far as reasonably practicable, and a strict limit value of 1 µg/m³ as an 8-hour TWA applies.

A vivid metaphor given by Jody Schinkel (TNO) during the CIKC event on chromium-6 under thermal insulation is that of a large tub of balls. Imagine a tub with 1 million yellow balls and 1 black ball. With every exposure you have to reach in once. The more often you are exposed, the more often you have to reach into the tub and the greater the chance of picking up that black ball. In this image the black ball represents developing cancer.

Some people will never pick the black ball, even if they have to reach in very often. Others have less exposure but are unlucky anyway. The message is: you can never fully control the risk, but you can make it as small as possible by reducing exposure as far as possible.

2. Does “safe” chromium exist? #

Chromium-3 (Cr(III)) is the more stable form of chromium and much less harmful to health than chromium-6. In the body, chromium-6 compounds are ultimately converted to chromium-3, but if that happens inside the cell it can actually cause DNA damage.

3. Can you identify chromium-6 from the colour of paint or insulation? #

No. Chromium-6 compounds exist in various colours and some applications are not even clearly recognisable from the outside. Looking at colour or gloss alone is therefore not reliable. You always need a reliable measurement and analysis.

4. When do you choose a quick test and when a laboratory analysis? #

Quick tests (such as the ST01 swab test) are suitable as an initial indication or screening but are insufficiently reliable. For policy decisions, legal discussions, clearance of objects or substantiation for supervisory authorities, you need a validated laboratory analysis that aligns with official standards such as NEN 5617 and ASTM D6966-18.

5. an SEEF help to structurally embed chromium-6 in our safety policy? #

Yes. SEEF supports organisations with:

  • Drawing up hazardous substances policy with attention to chromium-6
  • Embedding in risk assessments, multi-year plans and tenders
  • Measuring, interpreting and reporting exposure
  • Training and awareness within the organisation

6. Can chromium-6 disappear on its own or become less harmful?

No. Chromium-6 does not disappear from material or dust on its own. Under certain conditions it can be chemically converted to chromium-3 (Cr(III)), a less harmful form. This happens for example on contact with certain reducing agents or under strongly moist conditions. But this process cannot be controlled, proceeds slowly and can reverse: chromium-3 can under the right conditions oxidise back to chromium-6. You can therefore never assume that chromium-6 has spontaneously disappeared. Reliable analysis is always necessary, combined with the knowledge required to choose an appropriate strategy.

7. When is it useful to carry out air measurements rather than material research alone? #

Air measurements are particularly valuable when:

  • Work is taking place that generates dust, fumes or mist.

  • There is doubt whether employees are inhaling chromium-6 despite control measures.

  • You need to demonstrate compliance with the statutory limit value of 1 µg/m³.

  • You want to carry out a baseline measurement, progress measurement or clearance measurement.

  • You want to substantiate actual exposure in a risk assessment.

Material research tells you whether chromium-6 is present, but only air measurements show whether employees are actually inhaling it. SEEF supports both types of measurement, including interpretation and advice on control.

8. Why can one paint or insulation contain chromium-6 while another cannot? #

Whether chromium-6 is present depends on:

  • Year of construction or production date: older coatings and primers contain it more often.

  • Application: corrosion resistance, heat resistance, chemical resistance or as a pigment in paint.

  • Temperature load: at high temperatures, chromium in steel can react with calcium in insulation, causing chromium-6 to form.

  • Supplier or batch differences.

Even within the same installation, sections of material with and without chromium-6 can occur. That is why SEEF works with a targeted sampling plan, based on document research, risk analysis and targeted tests.

9. How do I know if my organisation is doing enough to protect workers? #

A good indicator is whether you meet the following elements:

  • The risk assessment explicitly includes chromium-6 as a hazardous substance.

  • An exposure assessment has been carried out based on measurements and validated against NEN689.

  • Policy follows the occupational hygiene strategy (source control, extraction, PPE etc.).

  • Employees have received training on risks and safe working and repeat this annually.

  • An exposure register is maintained for at least 40 years.

  • Contracts with contractors include agreements on research, measurements and measures.

     

  • Results are evaluated annually and tightened where necessary.

SEEF can provide support to embed all components, both technically and organisationally.

10. What is the difference between an indicative test (ST01) and a reliable test (TK01)? #

    • ST01 swab test

      • Quick indication for positive results.
      • Susceptible to false negative results.
      • Not suitable as legal or policy evidence.Not suitable for paint.

       

    • TK01 test kit (SEEF’s patented method)

      • Reliable detection, based on the same chemical principles as laboratory analysis.
      • Greatly reduced chance of interference from metals such as zinc and aluminium.
      • Suitable for insulation, lubricants, anti-seize pastes.
      • Can be used to measure paint, but laboratory analysis is strongly preferred.
      • Can be used as substantiation in reports, work plans and clearances.
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