How long after a new roof is catching water safe?

How long  after installing  a new shingle roof  must we wait before catching rainwater to safely use for plants and animals?

I don't think there's an easy answer. There are many variables and many differing opinions.

The new shingles on my cabin and garage were very different from the gooey old asphalt slabs they replaced. My choice was to give the new shingles a year to bake and freeze and wash off. I still collected the water and put it on non-garden shrubs. There was never a hint of a hydrocarbon sheen in the barrels. After that, I chose to use the water in the garden.

Even though its more money, I would go a metal roof and then its immeadiately.