OSHA claims people can develop mesothelioma from just a few days of asbestos exposure. Most doctors say 20+ years at high levels. Which is correct?

The expert. you can developped a reaction within days of exposure but not mesothelioma. by definition mesothelioma is a chronic condition from chronic exposure.
Both. Different people have different susceptibility. In general it takes 20-30 years after asbestos exposure for mesothelioma to develop. So the exposure may be for a short time and the incubation for the tumor may be very long. Consult this site for more info. http://www.mayoclinic.org/diseases-conditions/mesothelioma/basics/definition/con-20026157.