Dyes- Synthetic and "Natural"

I thought we’d take a look at the dyeing process because so many people ask if we use “natural” dyes. The answer is no, we don’t (although we’re not entirely objecting to natural dyes), and I hope the next two blogs will explain our position! Let’s first take a look at what makes the dyes (and how they are applied) an area of concern.

Dyeing cloth is one of our oldest industries; people used natural products found around them to change the color of the fibers used to make their cloth – things like leaves, berries, or roots. The first synthetic dye was created in 1856. Today the use of natural dyes on a commercial scale has almost disappeared (except for a resurgence in the craft market) in favor of the newer synthetic dyes. The production of synthetic chemical dyestuffs has become big business, but unfortunately, the production and use of these synthetic dyes is one of the world’s most polluting industries. Conventional synthetic dyes present health risks to those working with them and to those who wear them, as well as damaging the environment in a number of ways. Why?

Dyes are compounds that can be dissolved in solvents, usually water. The process of dyeing cloth uses a great quantity of water – according to the United States EPA, it takes an average of 5 – 35 gallons of water for every pound of finished fabric. That translates into 125 – 875 gallons of water to dye 25 yards of fabric – enough to cover one sofa![1]

The dyes in solution are absorbed by the fibers. The process of transferring the dye from the water to the fiber is called exhaustion or “fixation rate,” with 100% exhaustion meaning there is no dye left in the dyebath solution. Most conventional dyes have an exhaustion rate of 80%, meaning the dyestuff which is not affixed to the fiber is flushed into our rivers with the spent process water. Each year, the global textile industry discharges 40,000 – 50,000 tons of dye into our rivers, and more than 200,000 tons of salt.[2]

One of the most pressing issues today is the lack of fresh drinking water, and as one of the most polluting industries, textiles – and especially the dyeing of textiles – is responsible for many instances of pollution making fresh water undrinkable. In the worst cases, communities have to use polluted water to drink, wash clothes, bathe and irrigate crops, and the toxins they’re exposed to can have catastrophic effects. Even in those instances where water treatment is in place, toxic sludge is a byproduct of the process. Often sludge is sent to the landfill, but the toxicity of the sludge remains – containing, among others, heavy metals, gypsum, malachite green (identified by the U.S. Food and Drug Administration as a priority chemical for carcinogenicity testing).

The 40,000 to 50,000 tons of synthetic dyestuffs expelled into our rivers are complex chemical formulations containing some things that are very toxic to us, such as heavy metals (like lead, mercury, chromium, zinc, cobalt, and copper), benzene, and formaldehyde. Certifications and regulations restrict the kinds of chemicals allowed in certain products. For example, certifications may restrict amine-releasing AZO dyes and disperse dyes and limit heavy metals like chromium, cobalt, copper, nickel, mercury, lead, antimony, and arsenic. However, restrictions often mean limits rather than outright prohibition.

In addition to the formulation, there are requirements that dyestuffs must meet regarding oral toxicity, aquatic toxicity, biodegradability, eliminability, and bi-accumulation in fatty tissues. Some dyestuff producers advertise that they have a dye group that meets stringent standards. So the formulation of dyes used makes a big difference – look for dyestuffs that have been certified by a reliable third party.

Remember that if the average exhaustion rate is 80% for most dyes (i.e., that 20% of the dyestuff is expelled with the wastewater), then that means that 80% of the dyestuff remains in the fabric! In other words, those toxic chemicals remain in the fabrics you bring into your homes. What do I mean by “toxic” – if you can stand it, I’ll give a short synopsis of the effects some of these chemicals found in many dyestuffs have on us:

• • Mercury: Easily absorbed through the skin or inhalation of dust containing residues; affects the immune system, alters genetic and enzyme systems, and damages the nervous system. Particularly damaging to developing embryos, which are 5 to 10 times more sensitive than adults.
  • Lead: Impacts the nervous system. Even low levels of lead can reduce IQ, stunt growth, and cause behavior problems.
  • Chromium: At toxic levels, it causes squamous cell carcinoma of the lung.
  • Copper: Fatigue, insomnia, osteoporosis, heart disease, cancer, migraine headaches, and seizures. Mental disorders include depression, anxiety, mood swings, phobias, panic attacks, and attention deficit disorders.
  • Cadmium: Extremely toxic; primary target organ is the kidney but also causes lung cancer and male sterility. Chronic exposure is associated with renal disease.
  • Sodium chloride (salt): High concentrations can disrupt ecosystems and bioaccumulate in organisms, leading to a range of health problems.
  • Toluene: Affects the central nervous system; higher concentrations can result in unconsciousness and death. Prolonged contact can cause dermatitis.
  • Benzene: Highly carcinogenic; linked to leukemia and bone marrow damage.

Better Thinking Ltd., a UK-based organization, examined the dyes used in the industry and what they do to us and our environment. They published their findings in a paper called “Dyeing for a Change,” which explains the various synthetic dyes available and how they’re used.

There are several classes of dyes:

1. 1. Direct dyes: Color the fibers “directly” without a mordant but often include carcinogenic particles.
   2. Vat dyes: Require powerful reducing agents and are expensive and complicated to use.
   3. Sulphur dyes: Contain harmful substances like sodium sulphide, which endangers life and damages infrastructure.
   4. Reactive dyes: Bond directly with fibers, using relatively cool water (saving energy). A subset of these, “low-impact reactive dyes,” is considered a better environmental choice.

Of all the classes of synthetic dyes, low-impact reactive dyes seem to be the best environmental choice. These dyes contain no heavy metals or other known toxic substances, do not need mordants, and have a higher exhaustion rate, reducing environmental impact.

Research is ongoing to improve these methods. For instance, pre-treating cotton with phosphate buffer can eliminate the need for salt or alkali, reduce water usage, and minimize environmental damage. British scientists have even developed ways to use algae to color fabric, eliminating dyes entirely![3]

Water treatment remains critical – even if a dyestuff has a benign chemical formulation, the associated salts, defoamers, and fixing agents must be addressed.