My hosepipe -- presumably reinforced pvc -- has been around for a long
time, and I've just noticed that when I use it to fill a watering-can
the first couple of gallons are very frothy. At first I thought it was
traces of the washing-up liquid I sometimes use a drop of as a wetting
agent, but it's definitely the hose itself.

Question for the scientists: I assume I'm seeing products of the
breakdown of the material, so are they likely to be harmful to plants,
life, the planet, and everything?

Mike.