Attributable risk is a measure of how much of the disease burden could be eliminated if the exposure were eliminated.

It can be calculated for individuals or for populations.

Population attributable risk incorporates information on how common the exposure is.

* Some exposures have a powerful effect (large RR), but are so rare that their public health impact is minimal.

* Some exposures have a modest impact but are so widespread that their elimination could have great benefit.

For example, let’s assume RR of lung cancer due to smoking is 15 and that 30% of the population are smokers.

Population attributable risk = (.30)(15 - 1) = .81
                                         1+ (.30)(15 - 1)