M. bovis BCG is very susceptible to sunlight. Exposed to direct sunlight, half of the organisms are killed after 5 minutes. After half an hour, 99.9% are killed. Even after exposure to indirect sunlight, half are killed after 15 minutes and 99.9% are dead after two and a half hours.
These experiments were done with liquid BCG. As humidity (and thus liquid even more so) reduce the effect of ultraviolet radiation, the killing of mycobacteria in aerosolized droplet nuclei is probably much faster than in this experiment.
It is likely that the susceptibility of M. tuberculosis to sunlight is similar to that of BCG.
