it very much depends on the type of asbestos. if it was a roof sheet, itis likely to be asbestos cement, which is white asbestos, which is low risk for the period of time he was exposed.
A lot of times, one exposure to asbestos might not be enough to really hurt him, but he should be cautious, especially because it takes awhile to feel the effect this here was a great resource for me, and I hope it will help you too.
No amount of exposure is "safe", it depends on the situation. Id suggest he get a chest x-ray to ease his mind as signs and symptoms of mesothelioma usually do not occur for another 10+ years.
hi, I could tell from your responses, that you're knowledgable in this area. Do you mind reviewing my profile & let me know what you think?