There is no absolute data. Black mastic is generally more likely than brown to have asbestos. Commercial locations more likely than homes. However, there is no absolute and that is why testing is required. The long term consequences are impossible to predict. If it was asbestos, you may get cancer or you could live to over 100 years old with absolutely no impact.

There is no specific set percentage of asbestos inside old materials and adhesives. If you think you may have incurred a significant amount of exposure your best bet is to inform your doctor and keep a close eye on your health. Might I also suggest looking into an attorney if you were exposed during the course of employment.

If so, what would the likely content be in percentage terms? Also would all black adhesive (black mastic) used for flooring in the mid to late 1970's have contained asbestos? Again if so, what would the likely percentage of asbestos in the product be. Unfortunately, I have been exposed in the past decade or so to sanded mastic and was unaware asbestos could be involved. I was not wearing any form of protection (no mask, no goggles, no protective clothing) so I am trying to figure out how likely it is that I was exposed to asbestos and what the long term consequences to my health will be. I have read all kinds of horrific information online that makes me feel doomed so I am trying to cope.