Chemical of the Month: Chrome

by Toxicologist, Ewa Daniél

What is it?

Chromium is a metal known to be used in many different industries such as graphic, metal, cement and wood protection. It can thus be found in many different product types such as stainless steel, jewellery and as a raw material used in cement, and tanning of leather.

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It is natural occurring from the earth crust and can be found in both air, soil and water when its released to the environment from both natural sources and from the industries.

There are different types of chrome from Chrome2 up to Chrome6, and it is important to differ between them, since both function and effects are very different. We will look further in to the types which are the most used and present in the environment:

  • Trivalent chrome/Chrome III/Cr3
  • Hexavalent chrome/Chrome VI/Cr6

Cr3 it a natural occurring metal. It is found in nature and function as an essential nutrient in humans where it helps the body with insulin, sugar and lipid metabolism.

It’s found naturally in different kinds of food such as vegetables, fruit, meat, cheese, nuts, dark chocolate, shell fish etc. This kind of chrome is essential for us and we cannot live without it. Cr3 can be found both in the soil and also as an impurity in some cosmetics which are made from natural ingredients. This metal is stabile and often added to vitamins.

Cr6 is usually produced in an industrial process and used in production of stainless steel, tanning of leather, dye and pigments some metals and cement.  

So what is the problem?

Some types of Chrome can cause different health issues, when we are exposed to it from air or by skin contact.

Exposure in the air from industries is known to cause irritation in the upper respiratory tract and in worst case cancer. Direct skin contact with the metal can cause allergy. But the effects depend on the type of chrome you are exposed to.

Most cases of health issues from Chrome are occupational and caused by the type of chrome called Cr6. This kind of Chrome is often used in the industry, so workers can be exposed to it in their daily work. Besides effect from air, Cr6 has the ability to penetrate skin and cause skin allergy/contact dermatitis if people are exposed to the metal on their skin.

The most common cause of chromium allergy is from Cr6 used in process of tanning leather footwear. When leather that has been tanned with chrome is in direct contact with skin, the chrome can be released from leather, penetrate the skin and cause the allergy. Cr6 can also occur in cement. Previously, the number of chrome allergy in construction workers, has been high, but in 2015 the use of this was regulated in EU and since that the incidences of allergy from cement has decreased.

Chrome3 is not known to have the same health issues as Cr6, since Cr3 doesn’t have the ability to penetrate the skin and thus rarely causes allergy.  

What does the experts say?

The International Agency for Research on Cancer (IARC) has determined that Cr6 compounds are carcinogenic to humans.

The National Toxicology Program 11th Report on Carcinogens classifies chromium 6 compounds as known to be human carcinogens.

The Danish EPA (Miljøstyrelsen) states that both leather and leather objects with skin contact are not allowed to be sold if it contains CR6 in concentration ≥3ppm.

You should limit skin contact with Cr6 since this metal can causes allergic reaction in people who are already sensitized, and also cause new cases of allergy.

Cr3 is an essential metal for humans as it’s found in food and added vitamins. It can be found in some cosmetics, but it is not known to cause skin allergy since it doesn’t penetrate skin.

Low levels of Cr6 may cause allergic contact dermatitis. Patients with Cr6 allergy may react to a single occluded exposure to 1 ppm – 3 ppm Cr6.  


Cr6 is not allowed in AllergyCertified products since this type of chrome is known to cause allergy. People who have already developed Cr6 allergy may be so sensitive that they may even react to levels of Cr6 below the determination level.

This means that producers of for example clothing and leather are not allowed to use Cr6 in their production if they want their products to be certified.

Cr3 which can be found as an impurity in some cosmetic products such as cosmetics made with organic ingredients and makeup with colourings, this type of chrome is allowed as an impurity since it doesn’t penetrate the skin and is not known to cause allergy from these types of products.


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  • Miljøstyrelsen/The Danish EPA