toxicity and environmental damage associated with logwood and other natural dyes

Name: Deborah

Message: I've just started to experiment with natural dyeing.  I've done some research about the toxicity of mordants and dye stuffs, but I have not heard about the problem of hematein derived from logwood.  Is this also an environmental problem?  Is there a source that you can recommend for more information about toxicity and/or environmental damage caused by natural dyeing?  I have already read Jim Lile's and Jenny Dean's books, as well as the information from

Books and websites about natural dyes tend not to consider toxicity as a topic. Many neglect or groundlessly minimize the dangers of even such serious health hazards such as chrome, copper, and tin mordants. In order to research this topic, it is necessary to search for specific information from other sources about chemicals. If you know the name of the active principle in the dye, in this case hematein as the active ingredient in logwood, you can often find further information. 

Hemetein, the oxidized Hemateinform of hematoxylin (Colour Index Natural Black 1), in addition to its use as a textile dye, is an important stain for use in cytology. Here is a link to an MSDS for hematein, which identifies it as having a health hazard rating of 2 (where 0 is harmless and 4 is the maximum). It says, among other things,
"After contact with skin, wash immediately with plenty of water. Gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. Cover the irritated skin with an emollient. If irritation persists, seek medical attention. Wash contaminated clothing before reusing."
Logwood, the source of hematoxylin and hematein
Unfortunately, the MSDS says little about ecological hazards. Whatever harm may be posed ecologically by this material, it must be vanishingly small in comparison to its use in its heyday, when logwood plus iron was the most reliable black dye commercially available, before the introduction of modern synthetic dyes. Clear-cutting of Brazilian forests for logwood production undoubtedly resulted in much environmental damage. I have no idea whether logwood harvesting is currently practiced in an environmentally harmful way. [Followup: "Logwood from Aurora Silk is supposed to come from an environmentally and socially sustainable project."]

As long as you are steering clear of dangerous mordants such as hexavalent chromium (potassium dichromate, Toxic Dust Respirator a known human carcinogen) or tin, you will probably be safe enough with quite ordinary precautions. Always wear a properly-fitting dust mask or respirator when working with dye powder; never reuse dyepots or other implements for food; wear a lab coat or apron to protect clothing, goggles to protect the eyes if splashing is possible, and always wear reliable gloves while dyeing. (Some advise against the use of a dust mask, recommending only a NIOSH-approved toxic dust respirator.) I do not feel that these precautions are sufficient for working with chrome mordants, which are far too unsafe, in my opinion, for use in the home dye studio. Hematein is not nearly as hazardous as a chrome mordant. Prechromed synthetic dyes are safer than chrome mordant because smaller quantities of chromium are involved, and (more importantly) because they are in the much safer trivalent form of chromium.

Many dyers believe all natural dyes to be completely safe, but in fact this is often not the case. Besides hematein, there are other toxic natural dyes as well. For example, the dyes alizarin and purpurin, derived from madder, are associated with kidney damage in animal experiments. Lily-of-the-valley, sometimes used for a pale green, is certainly toxic, as is bloodroot. The leaves of rhubarb contain toxic oxalic acid. Even relatively non-toxic dyes such as cochineal are associated with allergies, especially among the workers who prepare them. However, I think that all of these are unlikely to be a problem for the careful dyer, who takes appropriate precautions and does not do anything that will result in breathing, eating, or otherwise consuming dyestuffs.

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Posted: Friday - November 23, 2007 at 03:42 PM          

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