Are natural fabric dyes best for the environment?
The answer to this question is not as obvious as many people think! Natural dyes carry their own hazards, and are not necessarily kinder to the environment than a dye plant which is run with proper environmental controls. Note that dye plants in some countries such as China are poorly run without proper environmental regulation, but other dye companies such as Dystar have earned eco certification for their factories (the EU label and Oeko-Tex Standard 100 certification). Most natural dyes require the use of a mordant, which is a metal ion used to pretreat the fabric so that the natural dye will stick to it. Unlike synthetic dyes, most natural dyes will not bond to the fiber without a mordant. The popular mordant potassium dichromate produces beautiful colors with natural dyes, but it is a known human carcinogen and a dangerous environmental contaminant. (It’s the chemical that did all that harm in the Erin Brockovitch movie.) The safest mordant, and therefore the most popular for home
