For example, there are lots of things in the media at the moment such as cancer rates increasing in younger women for which we do not yet have an explanation.
Sources?
To swap to natural alternatives that are cheaper, safer for the planet and make little difference in terms of their desired effects on hair etc, therefore seems like a no-brainer to me.
What do you mean by natural alternatives? Many of the ingredients in these 'chemical cocktails' are derived from 'natural' sources. Look at the supplementary information for tea tree oil:
H226 FLAMMABLE LIQUID AND VAPOUR. H302 HARMFUL IF SWALLOWED. H304 MAY BE FATAL IF SWALLOWED AND ENTERS AIRWAYS. H315 CAUSES SKIN IRRITATION. H317 MAY CAUSE AN ALLERGIC SKIN REACTION. H319 CAUSES SERIOUS EYE IRRITATION. H401 TOXIC TO AQUATIC LIFE. H411 TOXIC TO AQUATIC LIFE WITH LONG LASTING EFFECTS. PRECAUTIONARY STATEMENTS P273 AVOID RELEASE TO THE ENVIRONMENT. P280 WEAR PROTECTIVE GLOVES/ PROTECTIVE CLOTHING/ EYE PROTECTION/ FACE PROTECTION. P301+P310 IF SWALLOWED: IMMEDIATELY CALL A POISON CENTER/ DOCTOR. P305+P351+P338 IF IN EYES: RINSE CAUTIOUSLY WITH WATER FOR SEVERAL MINUTES. REMOVE CONTACT LENSES, IF PRESENT AND EASY TO DO. CONTINUE RINSING. P331DO NOT INDUCE VOMITING. P391 COLLECT SPILLAGE. P262 DO NOT GET IN EYES, ON SKIN
https://www.nhrorganicoils.com/uploads/20221202134851e_Tea_Tree_SDS.pdf
Also whether ingredients are "from plants" I think is a bit of a red herring. You can process ingredients and plants in ways that changes their essential chemical composition and makes them potentially dangerous (for example, Rapeseed oil
Your link says 'Industrial rapeseed oil is used in the automotive and chemical industries, it is not safe for human consumption due to its high content of something called 'erucic acid.' This is an acid occurs at high concentrations in oils derived from the cabbage family, such as rapeseed and mustard oil.'
But this proves my point! Industrial rapeseed oil isn't processed this way, it's naturally this way. We have genetically modified it to make it safe to consume, not the other way around.
Which is why they should be researched and considered carefully before incorporating into one's diet or products.
It is, very thoroughly. The EU rules for cosmetics (and food) are extremely strict. The FDA doesn't do half as much research into the safety of products in US markets.