MadSci Network: Chemistry

Re: Are fabric dyes dangerous?

Date: Mon Feb 2 14:18:38 2009
Posted By: Sean Hunt, Secondary School Teacher
Area of science: Chemistry
ID: 1231060952.Ch

Thank you for your question. Before answering your question directly I would like you to consider the following:

Many organic chemicals and some of the substances they react with are hazardous. This means that they are potentially dangerous for anyone using them. Possible hazards include:

X	Toxicity
X	Absorption through the skin (is this your question?)
X	irritation if inhaled
X	corrosive compounds
X	high flammability
X	carcinogenic compounds (cancer inducing)

The risk relates to how a hazardous material is used.

Studies have to be carried out to estimate the risk of a hazardous material. For example; hair dye often contains particularly toxic chemicals that are considered to be of low risk due to low exposure. In other words it is okay to dye your hair once every (say) two weeks but not more frequently. Another example is the use of fluoride in water and toothpaste. Fluoride is toxic and can cause bone deformities etc. but at low concentrations (1ppm) is considered beneficial to our health (helps prevent tooth decay). Note that for children under six a pea-sized amount should be used under adult supervision. Have you never wondered why this is written on the tube? Children swallow toothpaste, toothpaste contains a huge dose of fluoride, which, to be fair, you should spit out.

There are many other examples of toxic exposures that are considered acceptable.
So what about bleeding fabrics?
Whether natural or synthetic, a fabric has to withstand at least 20 (or so) washes without losing too much dye to pass many international standards. The first wash should be included in this standard and as a consequence many companies wash their clothes once before exporting them or choose expensive colourfast materials and dyes. Colourfastness is a measure of how well a dye sticks to the fabric. Some dyes are more colourfast than others, and some fabrics (e.g. cotton) are more colorfast than others (e.g. wool).

In my view, toxicity is a very controversial and difficult area of science. As I am sure you are aware, we are all exposed to a multitude of toxins on a daily basis. Does this mean we are all going to contract cancer? No; it all comes down to hazard and risk.

Shampoo contains toxins that would be considered unacceptable in orange juice, but, low and quick exposure (lather, rinse, repeat) means that we should not worry about cosmetics.

Likewise with clothing, the dyes are definitely toxic and harmful to health in large concentrations, or due to long or repeated exposures. If you work in a textile factory or wear clothes that constantly bleed their dyes, then you may be exposing yourself to what would be above acceptable risk levels.

Perhaps faded jeans and a faded cotton shirt would be safest?

Another thought:

That which is considered low risk today may be considered higher risk tomorrow;
That which is not considered high risk today is irrelevant.

Further studies:

"We expect that future environmental regulations will require that any new dyestuffs and the continued use of existing dyestuffs will rest on a demonstration of their low risk to human health and the environment."
Harold S Freeman -- Professor of dyestuff chemistry at NC State (2008)

Thank you for your excellent question,


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