[matthewh (OP)]

Paul has written into us:

If plastic waste is ground up and mixed with tarsal for roading, might it not be dislodged and then make its way into rivers and on to the oceans? Wouldn't it be better to add plastic into bricks for housing and ensure the bricks are painted or treated somehow to avoid rain leaching?

Leave your answers below if you have them!

[chris]

I agreed that embodying plastic into other more static buildings and structures is probably a better idea; I asked this very question that you have posed to Toby McCartney from the company MacRebur, who are testing a bitumen made with a plastic admixture.

He suggests in the interview that the plastic becomes "part of the bitumen" so there are not microbead wear particles and hence the environmental impact is mitigated:

https://www.thenakedscientists.com/articles/interviews/road-reduced-landfill-paved-plastics

I must say, I'm slightly sceptical; I'd like to see the actual chemical data to back this up, which, regrettably, there was not time to go into on the programme at the time.