How much asbestos does it take for you to breathe in to kill you?

This question cannot be answered. Some people have breathed a lot of asbestos and never developed disease. Others breathed relatively small amounts and died form mesothelioma or lung cancer.

In any case, the ill effects from asbestos are not immediate and you will not drop dead while breathing any amount of asbestos. The diseases develop 10 you 40 years after exposure begins.