Dye safety and bladder cancer

Name: Ann

by Monona Rossol


Country or region: Canada

Message: Hi Paula,

I read your text
about the chemical structure of red dye and was particularly interested that azoic dyes, which you recommend not using, are often referred to as "azo dyes."

I was just diagnosed with a very early stage of bladder cancer, and read that one of the risk factors is "exposure to chemicals....of particular risk are a type of dyes that include 'azo' compounds." (Here's the
link to that statement.)

Do you think that this source means azoic dyes? How can I find out for sure? I'm an avid dyer who uses procion dyes, always wearing a dust mask when mixing the powders (which I don't do very often; I keep the liquid dyes refrigerated for at least a month), and always wearing gloves. I would be totally devastated if I had to give up dyeing, but I obviously don't want to increase my risk of a new tumor growing.

Anything you can do to help me figure this out would be greatly appreciated!

I'm sorry you've been the recipient of such vague and frightening information, on top of having to deal with early-stage bladder cancer itself. There are some dyes that can cause bladder cancer, but that does not mean that all synthetic dyes are dangerous, especially if used correctly, with appropriate safety measures.

The specific dyes that you are using, combined with the safety measures that you are using, are extremely unlikely to increase your risk of any cancer at all. Not only are you not using any of the dyes that have been linked to bladder cancer, but you are using quite small quantities of dyes, compared to employees in the dye industry, and you are taking suitable measures to minimize exposure to even those small amounts that you do work with. I do not believe that your past use of Procion dyes has contributed to your recent diagnosis.

Your information page includes this statement:
"Exposure to chemicals — Being exposed to certain chemicals or industrial compounds in the workplace or the environment can significantly increase the risk of bladder cancer. Of particular risk are a type of dyes that include "azo" compounds. In most cases, it takes many years after the chemical exposure for the person to develop bladder cancer."
This is rather infuriatingly vague. There are many dyes that contain azo linkages, but only some of them are thought to cause cancer. Azo means nothing more than that the dye molecule contains two nitrogens bonded to one another with a double bond, and carbons attached to each nitrogen. There are safe chemicals that contain azo linkages, and there are toxic and unsafe chemicals that contain azo linkages. It is not the azo linkage that makes a dye dangerous.

Some azo dyes are considered to be safe enough even to eat. Azo dyes that are permitted as food additives in Canada (since that's where you live) include tartrazine, sunset yellow, amaranth (not to be confused with the plant of the same name), and allura red. While I am not convinced that regularly consuming large amounts of artificial food dye is a good idea, the safety testing that has been performed with these dyes does prove that not all azo dyes are equally suspect.

The azo dyes that are suspected of causing cancer are based on the chemicals benzidine, o-tolidine, and o-dianisidine. Certain dyes are manufactured from these carcinogenic chemicals; the metabolism of these dyes by the body can produce these chemicals again. None of the fiber reactive dyes whose use I recommend are based on any of these dyes. In fact, no reactive dye at all is listed among the dyes based on these three chemicals. However, there are many direct dyes, including some that used to be contained in all-purpose dyes that were sold for home use, that are based upon them, and a few acid dyes, as well.

All-purpose dyes, such as Rit All-Purpose Dye and Tintex Fabric Dye, contain a blend of direct dyes and acid dyes. At one time, up to and including the 1970s, these household dyes include many dyes based upon benzidine or o-dianisidine. I think that it is probable that Rit dye no longer contains any of these dangerous direct dyes, only safer ones. Unfortunately, it's hard to be be certain, because the Rit dye company, and other companies that produce all-purpose dyes, maintains a high level of secrecy about which specific dyes are used in their products. I know that one dye based on o-dianisidine is currently being marketed by another manufacturer for children to use, in the form of "Tie Dye Cords", which are to be tied around fabric and then dropped into boiling water. Tie Dye Cords are strings that are impregnated with direct dyes. As a rule, Tie Dye Cords are not used by serious hand dyers, because the results are very much inferior to other dyes. (See "o-Dianisidine in dye-impregnated tie-dye cords" .)

The dyes that you, and all of us, are supposed to specifically avoid include those on this list: direct black 1, direct red 28, direct black 38, direct blue 6, direct green 6, direct brown 95, direct brown 2, direct blue 2, and direct black 4, and acid orange 45, acid red 85, acid red 114, acid red 167, acid black 209. (None of these dyes are included among the dyes listed on my WashFast Acid Dyes page, Leveling Acid Dyes page, or the other acid dyes on my lightfastness page.) A more complete list is in the appendix to the 1980 NIOSH alert, "Health Hazard Alert--Benzidine-, o-Tolidine-, and o-Dianisidine- Based Dyes", or in the rather lengthy post "Specific dyes to avoid", which is part of the Dye Forum discussion about tie dye cords that was linked in the preceding paragraph. If you are not using all-purpose dyes or direct dyes, then you are not using any of the dyes from this list. If you do use all-purpose dyes, I recommend that you (and everyone else who is concerned) switch to dyes whose specific identity is revealed by the seller, just so that you can be sure. There are some direct dyes whose sellers, unlike Rit, Tintex, Deka, or Cushing, will tell you exactly which dyes they contain. Although the dyes used in any particular premixed dye color are a trade secret, you can find which acid dyes or direct dyes are being used in the entire dye line when you buy from PRO Chemical & Dye, and which acid dyes are being used in the unmixed dyes from Jacquard Products or the new line of Dharma Acid Dyes. Knowing what dyes you are using, you can look up the MSDS and other safety information and be sure that they are not among the dyes you've been told not to use. You may find it simpler to just stick to fiber reactive dyes, such as the Procion MX dyes.

Naphthol or napthol dyes, which are sometimes also called azoic dyes, are hazardous in a different way. (See "About Naphthol Dyes".) Although some naphthol dyes are based on benzidine, o-tolidine, or o-dianisidine, there are additional hazards of this class of dyes that are not related to these chemicals. The worst thing about naphthol dye components is that some of them can be absorbed directly through intact skin, unlike reactive dyes which tend to react with the first skin cells they encounter and are thus less likely to proceed further into the body. A minor hole in a glove that would probably be no big deal with fiber reactive dyes is a serious matter with naphthol dyes, some of which are carcinogenic or mutagenic or possibly even teratogenic. However, this is not likely to be an issue for you, simply because I doubt you have ever considered using naphthol dyes. I don't know any hand dyers in North America who use naphthol dyes, though there are some in Australia and Indonesia. Some naphthol dyes are used in the textile industry in the US, but they are not sold by any hand dyeing supplier in the US or Canada. As long as you are buying dyes from a hand-dyeing supplier in Canada or the US, such as Maiwa, G&S Dyes, Dharma Trading Company, or PRO Chemical & Dye, you do not have to think about naphthol dyes at all.

Among hand dyers, anyone who is careful is at much lower risk than those who are exposed to high amounts of hazardous chemicals through their jobs. In their discussion of the causes of bladder cancer, the web site eMedicineHealth says, "Strict workplace protections can prevent much of the exposure that is believed to cause cancer." The care that you have taken to follow the rules of good dye usage is similar. Some dyers are careless with their dyes. Some dyers refuse to wear gloves at all, and dip their hands directly into their dyebaths; because they are using Rit Dye, and because Rit Dye is sold in the grocery stores without much in the way of warning labels, they assume that the dye is totally harmless. (See "Why We Should Be Very Careful When Using Chlorine Bleach", for one example.) The level of exposure among these careless dyers is vastly higher than that among people who follow normal precautions, such as wearing gloves to handle dye powders and dye solutions, wearing a dust mask when working with dye powders, and immediately wiping up spilled dyes. It's rather horrifying to think about home dyers in the fifties, sixties, and seventies dipping their hands into benzidine- or dianisidine-based dyes with no gloves or other protection, without any concern for risks. I am also concerned about the risks posed by tattoo inks, which are known to contain carcinogenic chemicals such as aromatic hydrocarbons, which are considered to be a risk for bladder cancer, and yet are injected into the skin, without regulation or disclosure of ingredients.

For further reading about dangerous dyes, see the following publications from the USD Centers for Disease Control :
• "Public Health Statement for Benzidine"
and the book,

Here's an interesting link to a short piece in the July 1982 issue of Mother Jones magazine about the dangers of benzidine-based dyes in Rit dye.

It is, of course, wise to avoid unnecessary exposure to any household chemical; I would not encourage anyone to be careless with the use of any non-food-tested dye, including natural dyes. However, there's no reason to be more concerned about Procion MX dyes than about other household chemicals such as dishwasher detergent or chlorine bleach, both of which are more hazardous. They are safe to use with the normal precautions of gloves, etc. I would be much more concerned about job exposure in a manufacturing industry, such as the manufacture of rubber, or about exposure to cigarette smoke.

In her book, Monona Rossol has little concern about dangers of fiber reactive dyes, aside from their allergenicity to people who breathe too much of the dye powders, but she warns that some anthraquinone -based dyes, which are found in many different classes of dyes, might be found to cause cancer. The anthraquinone-based dyes do not contain an azo linkage, so they are not azo dyes. Among the Procion MX dyes, Procion Blue MX-R, which is Colour Index Reactive Blue 4, is an anthraquinone-based dye; it is duller in color than the triphenodioxazine dye Procion Blue MX-G, which is Colour Index Reactive Blue 163. Interestingly, some natural anthraquinone pigments, such as those found in the rhubarb plant, have cancer-preventative properties, so it's not obvious that all such dyes will be a concern. Reactive blue 4 has not been found to be a carcinogen; we don't know whether it might be if large-scale feeding tests were performed in animals, so it is, as always, best to avoid excessive careless exposure to the dye.

For further safety information on this site, see:
• "Specific dyes to avoid"  and
• "Dye Safety FAQs"

For more information about the specific dyes you use, be sure to request the MSDS for each color you order from your dye supplier, or use my page of "Which Procion MX colors are pure, and which mixtures?" to learn the generic Colour Index names for the unmixed dye colors, so that you can search for MSDS or other safety information elsewhere. You can also see MSDS pages that have been supplied by Dharma Trading Company (look for "Dharma Fiber Reactive Procion Dyes"), or  the MSDS pages supplied by PRO Chemical & Dye  (look for "MX Fiber Reactive Dyes"), or, for Jacquard Products' Procion MX dyes, at Blick Art Materials (the MSDS links appear to the right, next to each color name). For the proper use of any dye, PRO Chemical & Dye's Studio Safety Guidelines are a good resource.

Best wishes for your cancer treatment. I see no reason why you should not continue to enjoy using Procion dyes, while avoiding the use of any chemicals that may increase your chances of developing another cancer.

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Posted: Monday - June 20, 2011 at 03:21 PM          

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