Another interesting point to add:
"Cannabis is often compared to tobacco, with the damage caused by smoking tobacco given as a reason to prohibit use of cannabis. Yet most of the harms caused by tobacco use are due not to tar, but to the use of radioactive fertilizers. Surprisingly, radiation seems to be the most dangerous and important factor behind tobacco lung damage."
"It's a well established but little known fact that commercially grown tobacco is contaminated with radiation. The major source of this radiation is phosphate fertilizer. The big tobacco companies all use chemical phosphate fertilizer, which is high in radioactive metals, year after year on the same soil. These metals build up in the soil, attach themselves to the resinous tobacco leaf and ride tobacco trichomes in tobacco smoke, gathering in small "hot spots" in the small-air passageways of the lungs. Tobacco is especially effective at absorbing radioactive elements from phosphate fertilizers, and also from naturally occurring radiation in the soil, air, and water."
Source:
Radioactive tobacco