The (pseudo)science of chrome

"I don't think I want that jumper. I don't like synthetic fibres. I checked the label and it's viscose."
"Viscose is natural. It's made from wood pulp."
"Really? Wood pulp? I had no idea, I thought it was synthetic."

What do we mean when we say that something is natural? In common use it seems to mean that it has been obtained from plants or animals rather than a laboratory. The problem with this usage is that nothing is made from nothing: in the lab, scientists are extracting compounds from raw materials found in or on the earth, which are clearly natural. Which means that, using this definition, everything is natural: cotton, wool, viscose, polyester, metal, plastic, televisions, cars.

Of course, what people really mean when they use the word 'natural' is gentle, unprocessed. The shampoo bottle assures us that its contents are '100% natural' meaning that they'll do us no harm. This is ludicrous: poison ivy and deadly nightshade are 100% natural but I wouldn't recommend rubbing either into your scalp. This vague, hand-wavy use of the word is part of our society's general misunderstanding of science, and equating the word 'synthetic', or, even worse, 'chemical' with 'damaging' demonstrates how science-phobic we have become.

I've become bothered by this lately and it all started when I decided to do my most recent dye experiment (photos to follow once the yarn's dry) - one dye extraction on several different mordants. My original plan had been to attempt five mordants in total, being alum, copper, tin, iron and chrome. I read up on each on the internet and found that chrome is the source of a great deal of controversy. Briefly, it's supposedly a health risk (breathing problems, skin irritation, carcinogenic etc.) and shouldn't be poured down the drain for environmental reasons.

Possible health risks and environmental risks should give any sensible person pause. It's one thing to expose yourself to a tiny amount of something carcinogenic, but it's quite another thing to pollute the environment, potentially affecting those other than yourself. The human race has historically demonstrated itself to be deeply arrogant about waste disposal, whether it's an individual dumping a fridge by the side of the road or a corporation pumping hazardous compounds into the sea. I'd rather not be guilty of this thoughtlessness, but I have questions about chrome mordant that I'd like answered before I get too angry about people's use of it. I understand that it can kill microorganisms in the water purification plants, but so, presumably, can toilet bleach, and even antibacterial soap, both of which we all chuck down the drain the whole time. Are the effects of chrome mordant worse than this? Is it more carcinogenic than, for example, passive smoking? If I chuck a dozen dye lots' worth of chrome mordant down the sink, am I doing as much damage as the chlorine from the swimming pool down the road, or do I not even compare?

Unfortunately, I've been unable to answer these questions, and partially that's because a vast number of sites I've found discussing the dangers of mordants have been packed with pseudoscience and fundamental misunderstandings of chemistry. When a writer misuses the words 'natural', 'chemical' and 'metal', then it's hard for me to take their advice seriously.

I've found one site which seems fairly authoritative, here:
http://sonic.net/~dbeebee/IMDI_new/mordants.html

My understanding is that, while chromium compounds do occur in nature, the chromium VI oxidation state does not, and this is the one used in chrome mordant. This state is known to be dangerous. Until I know better, I won't be using it in my dyeing experimentation.

The conversation with which I opened this post was something I once overheard at a clothes shop. Viscose is indeed formed from wood pulp, but the pulp goes through a chemical change to form viscose. We can trace the manufacture of viscose back to something natural, as we can with everything else on earth. So the next time the cosmetics counter lady informs you that a product is 'completely natural', it's reasonable to reply, 'Well, yes. What isn't?'