Article: Studio Safety - The Cadmium Report

There's cadmium and then there's cadmium. The fact that there are very real differences in the kinds of cadmium used in a variety of industrial applications, including as a pigment in the production of art materials, has contributed to confusion and, in some cases, concern within the artists' community.

Depending upon the specific method of application, the solubility of the cadmium within the pigment matrix, and the precautions taken by the user, the hazards associated with the use of cadmium vary. 

What should be considered when using cadmiums? In an attempt to answer the questions, this report will outline the history, chemistry, and the safe use of cadmium pigments.  

The history of Cadmium colours

Before cadmium found its way to the artist's palette, other pigments (often with far more serious hazards than cadmium) were used in the creation of reds, oranges, and yellows. Until the introduction of Cadmium Red in the early 20^th century, the most dynamic, fiery red was Vermilion. Originally produced as crushed pigment from the mineral "cinnabar," the colour is a form of mercuric sulfide (HgS). Cinnabar was used by the Greeks and Romans, and transformed into the purer form of Vermilion, most likely, by the Chinese. The resulting rich, remarkably clear hue was unmatched by any other pigment. Mercuric Sulfide, however, is a potent health hazard, particularly for those involved in making the pigment, and Vermilion is no longer available. Luckily for any artist looking for a bright, clear red, the cadmiums had become available by the time that true Vermilion was being phased out of production.

Cadmium is a metallic element and is highly stable. It shows up in nature in a variety of forms and in combinations with other compounds. Cadmium sulfide (the same compound created for use as a pigment) can even be found naturally as the mineral "greenockite," although there's no record of it being used for pigment production. 

Commercial production of cadmium reds began around 1910, and, with the unique combination of brightness, clarity, and opacity, there are paintings that simply never could have happened without it. There's no question that the rise of cadmium made the farewell to Vermilion much easier.

The solubility of cadmium and what it means to artists

The health hazards associated with cadmium depend, in general, upon two variables: the first is the relative solubility of the cadmium or cadmium compound. The second is how the cadmium finds its way into the human system. Let's take that one first...

Cadmium, or any other pigment for that matter, most commonly makes its way into the human system through two routes: ingestion or inhalation. The health risks occur with cadmium that is inhalable in particle form or with cadmium that is soluble (more on solubility below).

There have been some indicators that inhalation of cadmium dust, primarily as an irritant in the lung, can lead to a risk of cancer. All cadmium-containing colours in the US are labeled with a warning to avoid any spray application, with the express intention of minimizing any risks that may come through inhalation. The good news is that, in small amounts, the risk appears to be negligible.

The California Department of Health Services has determined that there is no significant risk of cancer (as outlined in the Health and Safety code, section 25249.10[c]), with a daily inhalation of 0.05 micrograms of cadmium for life. Even so, it's still wise to avoid spraying cadmium colors.

So what about the ingestion of cadmium? It depends upon the compound or the form in which the cadmium is ingested. Here's the story on solubility...

Cadmium exists and can be produced in a wide variety of compound forms. Any health risk, either directly to individuals or as a broad environmental hazard, depends upon the solubility of the compound and whether the cadmium is able to move about freely and react with any molecular neighbors in the human system.

The impact of cadmium in humans has been studied by tracking the path of any soluble cadmium as it moves through the body. In one study (H.J. Klimisch and C. Gembardt, OSHA Rule Making Hearings, 1990, Exhibit 142) the trails of soluble and insoluble forms of cadmium were tracked through the human system to the kidneys, where the element can be accumulated. 

With a dose of cadmium chloride (a soluble compound salt NOT used in pigment production) 35% of the original amount of cadmium chloride was able to make its way through the biological system and settle in the kidneys. Conversely, the same test with insoluble cadmium sulfide showed that only 1% of the compound made its way through the body to settle in the kidneys. 

Winsor & Newton cadmiums 

The cadmium-based pigments used by Winsor & Newton have been shown to include only 0.0005% soluble cadmium and that amount is the result of residual impurities. The cadmium compounds used as pigment (cadmium zinc sulfide, and cadmium sulfoselenide) are all insoluble by their very nature because of how the cadmium is securely bound into a stable structural lattice.

The bottom line? The less soluble the compound, the less impact upon the human body.

That doesn't mean, however, that cadmium-containing colors (or ANY art colors, for that matter) don't require careful handling. They do. For a complete set of handling guidelines, visit the health & safety section of our website.

The Big Picture: Cadmium in other industries

The long-term residence of cadmium upon the artist's palette will depend upon continuing demand for the pigment in other industries. Only a small percentage of cadmium pigments are used in the production of artists' colors. The overwhelming majority is used as a colorant in the plastics and packaging industry, where the pigment offers great stability when subjected to the high heat required during production.

Due to regulatory pressure and concerns regarding toxicity, the use of cadmium pigments in those industries has declined. If this continues there exists a possibility that the overall market will be insufficient to justify production of the pigment. If that occurs, then there will be even greater need to look for...

...Alternatives to Cadmium

Is there another yellow-to-red pigment of great brightness, clarity and opacity available as a cadmium replacement, in much the same way that cadmium succeeded Vermilion? Yes and no.

Over the last few decades, there has been explosive growth in the availability of reds and oranges made from organic and synthetic sources.  It is unlikely that a single one of those pigments could serve as an all-in-one replacement for cadmium (should one be required). It is more likely that a group of different pigments will fill the gap.

At present, there is still no red pigment that matches cadmium in the purity and "temperature" of hue and opacity, and that matches its mixing characteristics. Depending upon the artist's needs, the closest available alternatives are colors milled with organic pigments such as:

• pyrroles (e.g., Artists' Acrylic Pyrrole Red)
• perylenes (e.g., Artists' Oil Colour Winsor Red Deep and Artists' Acrylic Perylene Red)
• quinacradones (e.g., Artists' Acrylic Quinacradone Red).

In the yellow spectrum, alternative pigments that offer great brightness and clarity are:

• arylamide (e.g., Artists' Oil Colour Winsor Lemon and Artists' Acrylic Colour Azo Yellow Medium)
• benzimadazolone (e.g., Artists' Water Colour Winsor Lemon and Winsor Orange)

The pigments mentioned above are used in a wide array of colors throughout the Winsor & Newton ranges and the list of examples is not exhaustive. When looking for cadmium alternatives, read the product label of all Winsor & Newton colors for complete information about pigment composition. Alternatively, visit the color chart section of our website.

Today cadmiums are a key part of the artists' palette and Winsor & Newton remain committed to creating the best artists' colours and materials both now and in the future, as we have for more than 178 years.

If you have any queries regarding cadmiums, you can contact us here.