I've been using my rainbarrel water in my vegetable and fruit garden and on my fruit trees (no negative consequences noted). But I just stumbled across the following info today:

"General practice is to avoid watering vegetables and other edible plants, such as herbs you plan to use in cooking, with rain barrel water collected from asphalt-shingle roofs. These kinds of roofs may leach various complex hydrocarbon compounds, so most people avoid using water from asphalt-shingle roofs or flat tar roofs on plants meant for human consumption. To date there is no definitive research on the amounts and types of hydrocarbon compounds which may leach from such roofs, though it is common practice to use water collected from asphalt-shingle roofs for watering ornamental plants and shrubs. Enameled steel and glazed tile roofs generate little or no contamination and rainwater harvested from them is commonly used to water vegetables."

Obviously I don't want to increase my risk of cancer or food contamination. I just wanted to know if the consensus here is that this is a valid concern? I really like the idea of water conservation despite the fact that watering from a hose is easier and faster.

I suppose I could use the rainbarrel water for the lawn and non-edibles but...