I have always found that the purchase of a good dictionary to be an incredibly sound investment. I have worn out a few in my time. I suggest a Merriam Webster Collegiate or the Concise Oxford for quality and ease of handling.
1. A rubbing away or wearing down by friction.
2. A gradual diminution in number or strength because of constant stress.
3. A gradual, natural reduction in membership or personnel, as through retirement, resignation, or death.
The choice is all yours - does the asbestos diminish gradually with every fiber that gets inhaled or are they waiting for the day when everyone who cares is gone?