Ask the Expert Question-and-Answer Archive

by Ron Joseph

June, 2001

Disposal of Pigments for Silk Dying

Q. Under a World Bank mission to Vietnam, I've visited a household silk weaving and dying enterprise. They use some black pigment (produced in PR China) but I was unable to gather any specific information about its trade name or ingredients. What would be the polluting impact of discharging the used dye into the river system (no treatment whatsoever), a common practice in Vietnam.

A. Thanks for your e-mail.

Since I don't know what pigment is used in China for dying silk, it is impossible to answer your question. Also, I don't deal in dyes as much as in paints. If we were discussing paints, the most common black pigment is carbon black, which comprises, as the name implies, carbon and is nontoxic. Also, since you don't know anything about the other ingredients it would be pure speculation to say somethng about its effects on living organisms, animals, humans, fish, etc.

In my opinion, and this is nothing but speculation, the disposal of dyes into the rivers may or may not be harmful to humans and animals (depending on the chemical makeup of the dyes), but I can imagine that if the concentrations are sufficiently high, the dye will discolor most of the soil and plants along the river. I guess this seems fairly obvious.

Hope this helps.