Hi mate.. some of my earliest childhood memories revolved around picking up any litter I could see. Back then.. the pieces seemed a lot smaller, though. I'm guessing that perhaps they were - with the problem having seemingly become so much worse as the decades rolled by.
In terms of a passion for the environment.. well I have appreciated the wonder of nature for quite some time, but I don't think all my life. As a child (into early adulthood), I was always afraid of bugs in general. I also didn't focus enough on the terrible things which were happening to our planet. I never gave the issues the attention which they so deserved.
It was really following a major emotional breakdown, which I started paying closer attention (rightly so). Take care my friend.