Hi, I have not done alot of research in this area, as I have steel metal roofs that I collect my rain water off ot, but having said that, my grandparents, parents and even I for many years did collect water off roofs that were shingles and used it for water of plants. I will be interested in seeing what others have to say about this..

My opinion.. but not fact... is that the time that the water is in contact with the tar is NOT long enough to dissolve toxins in any amount to be harmful. After all... most downspouts drain onto the land and it is where the growth is greatest. You NEVER see a dead patch where the downspout drains....

I collect rain water from an ashphalt roof, but I don't drink it...more because of the barrel having contained chemicals before. For drinking water,I plan to use my old surface well or lake water and purifying by boiling AND bleach method. Other than that, you can take a sample of your rain water to any place that sells and services well pumps and have it tested. The tests are very complete and will tell you just how good (or bad) the water is. I have my water from the artesian well tested every year for about $50.00. Happy to know it's better than the bottled stuff!!

At one of the sites i looked at on youtube they mentioned a special membrane you can put over ashphalt shingles. I will see if i can find it again.

I hear conflicting things all the time about rainwater and asphalt roofs, so I just go with my gut until I hear concrete proof in any one direction. Like JustABear mentioned, I can't really see how such minimal contact with the roof would soak up any toxins, or at least enough to do any harm. I don't drink my collected rainwater though, and just use it for watering the garden. I store tap water in separate containers for drinking.

Yes I agree with BCPrepGirl and JustABear. I collect rainwater off of two buildings with shingle roofs and use it to water plants and gardens. As did my parents and grandparents. I do have filters on the barrels to trap any crud that comes with the rainwater. If I was serious about needing to drink it I would filter it again and treat with bleach/chlorine, but as with the others posting on this I have several other sources of water and the chances of needing to use it for that purpose are slim to none.

Considering everything else that is going on out there in the world that is adding carcinogenic particles to our atmosphere and water, I doubt the rainwaters fleeting run off time on the roof is what we really need to worry about.

I have collected rain water from an asphalt roof for many years. None of it goes to waste. One side of the roof drains into a wooden barrel that I use for the garden the excess from the barrel feeds the flowerbed. The other three sides of the roof feed separately into the duck ponds. I agree with BCPrepGirl there would not be enough time spent on the singles to begin to dissolve any carcinogens, there is probable more in the air. However everyone must be feeding their barrels with eaves trough and down spouts. The eaves trough WILL contain bacteria from decaying plant material. It would need to be treated it you wanted to drink it. Add chlorine and run it through a Berkey filter and it would be fine.

Well I use my rain water off my ashphalt roof. Have for the last 13 years. only water I use year round. no problems at all. if its to be drunk, then it is boiled and filtered or distiled. otherwise used as is. I have a well but the rain water is better.
I have a theory, have you ever put your hand on a ashphalt roof on a sunny day. I bet the heat kills all germs. I could fry a egg on my roof.