ok just was reading the forum that Bourbonman posted which lead me to look in to the manufacture of bamboo yarn.
"It's not that thread that's about wicks, it the one linked to on page 27 or thereabouts - it's 110 pages long

. I read a few pages and they are on about bamboo for wicks, now, I'm a spinner and dyer, so I come across the undyed fibre and yarn a lot, Bamboo is a rayon ( synthetic made from bamboo cellulose) and is pretty environmentally unfriendly in manufacture, so I'd be fairly wary about it TBH. cotton seems doable, but I'd use organic unbleached"
so I looked up
bamboo yarn on Wikipedia.
which lead me to Viscose Manufacture
"At first wood pulp is dissolved in caustic soda and after steeping it for a specified period of time it is shredded and allowed to age. Ageing contributes to viscosity of viscose. The longer the ageing time the less viscosity it will have. The aged pulp is then treated with
carbon disulfide to form a yellow-colored cellulose xanthate, which is dissolved in caustic soda again, but of a lower concentration. This is the starting stage of viscose formation. During the process an acetate dope is added to alkali cellulose which is necessary for the yarn lustre.
Cellulose is treated with alkali and carbon disulfide to yield viscose.
Pollution
Viscose currently is becoming less common because of the polluting effects of carbon disulfide and other by-products of the process, forcing some factories to close. One way to comply with sulphur emission standards is to install a wet sulfuric acid process unit which recovers sulfur compounds to sulfuric acid or use the Lyocell process which uses N-Methylmorpholine N-oxide as solvent."
I think I will be staying away from bamboo yarn with the chemicals used in production.
Carbon disulfide Health effects At high levels, carbon disulfide may be life-threatening because it affects the nervous system. Significant safety data comes from the viscose rayon industry, where both carbon disulfide as well as small amounts of H2S may be present.
Xanthate Environmental impacts Xanthates may be toxic to aquatic biota at concentrations of less than 1 mg/L.[6] Water downstream of mining operations can be contaminated.[7]