CHAMPROBoys' Triple Crown Open Bottom Youth Baseball Pants, White, Navy Pipe, Large

Why is there a prop 65 warning for this brand baseball pants?

Why is there no size chart posted?

I'm a first time buyer for - my son normally wears a 10/12 for length with the adjustable waist band because he's so skinny. Is this a M or L?

What would be the main size difference between the youth xl and the adult small? it looks like the waist are similar, how about the length and fit?