This would be illegal in the UK as any product containing asbestos would be classed as special waste, and should never be dumped with "normal" waste. I assume it's much the same law in the USA and other countries. Tell your father-in-law. He shouldn't do this and is risking his health as well as the people processing the refuse. Also, it needs to be taken up by specialists who know what they are doing. Sounds like he (and his colleagues) should talk to his doctor about health checks.