Radon222 as a daughter in the decay chain of uranium is gaseous at room temperature. it is an inert or noble gas that does not interact chemically in the body. however it decays into pb210 which attaches itself to vegetation such as tobacco leaves as a solid and subsequently decays into po210 which emits an energetic alpha particle with 5.3 mev of energy. the inhalation of these two isotopes in the particulate matter of cigarette-smoke delivers to the average smoker a radiation effective-dose or dose-equivalent of 8 rems (radiation equivalent man) per year to the basal cells of the bronchial tissue. the "cancer dose" is the total radiation dose that if spread through a population would cause one additional cancer death and is considered to be approximately 2,000 rems. calculate the ensuing radiological risk in units of cancer deaths per year in a population of one million smokers.

4,000 cancer deaths

Explanation:

One smoker usually receives radiation dose of 8 rems (radiation equivalent man)/year to his branchial tissue cells.   Cancer dose (total radiation dose that if spread through a population would cause one additional cancer death) = 2,000 rems  

1 Smoker                 < 8 rems

1,000000 smokers <  X  rems

X = 8,000000 rems  

If cancer dose implies 2,000 rems, that would cause one additional cancer, we’ll have that 4,000 additional cancer deaths will reach that population of a million people/year. This means the 0.4 % of the smoker population

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

i do not get it   at all