The dangers of asbestos became apparent after many employees who built Liberty Ships for WWII developed lung cancer and Mesothelioma. Asbestos was used for insulation in the ships, and many workers were exposed clouds of asbestos particles daily. Smoking could increase their chance of these diseases by a factor of 10.
Asbestos comes in several different varieties, and only the small particles with a sharp needle like structure were linked to the diseases. In the lungs, they could directly cause cancer. They could also migrate through the lungs to the outer lung lining, causing Mesothelioma. Larger particles could be stopped from even getting to the lung, and smaller, rounded particles could be intercepted by normal body defenses. Much of this information is ignored by the press and the plaintiff attorneys.
Asbestos is also found out doors in nature.
When the wind is out of the northwest, blowing across Lake Ontario from the cliffs in Canada along the north shore, the level of asbestos in the outdoor air in the Adirondacks exceeds NYS standards for asbestos levels for indoor air.
It's a rock that occurs in nature and can be encountered even in the outdoors.