The effect of plastic on light, and vice versa:

Does using a clear plastic dome affect the quality and/or quantity of light which reaches the small plants? Do the lights, at close quarters and in a warm environment, cause plastic to leach at all?
Thanks for any wisdom on this.

Ive never heard or seen any evidence that clear plastic significantly absorbs/filters or scatters the spectrums we are interested in.

Twinwall clear plastic is a standard in horticulture, being used to cover many square miles on this planet and prefered by many to glass for various reasons.

The plastic will absorb the uv spectrum and get damaged by it however most grow lights have little to no uv and for small plants you dont want much uv hitting them anyway.

You dont want to keep plants under plastic domes for long fyi.. You run the risk of encouraging pathogens if the RH goes above 85- 90% id only advise them for clones or the first week of seedlings assuming you cant maintain humidity a better way.

I hope that helps a bit

Even clear glass will degrade light to some extent. You will see noticeable growth improvement from an open light vs a air cooled one. That being said, clones don't need much light so the amount of light blocked by dome is a non issue.

Thanks for the excellent replies, folks.