Also, body counts are strictly hypothetical. The figures are arrived at using statistics, not by counting bodies. They're not audited to see if they're accurate. In contrast, the 150,000 annual deaths from trauma-induced injuries are countable. Too Many Variables Finally, beware of researchers who try to split a hair with an ax.
Epidemiology is useful only in studying high disease rates or rare diseases, and preferably both.
For example, heavy smokers are reported to have a relatively high rate of the relatively rare disease of lung cancer. Simply put, epidemiology cannot eliminate all the variability among humans. Also, researchers often don't really know how much of a risk factor the individuals in a studied population have been exposed to and are forced to guess at exposure levels. Let's say a study reports that living near a hazardous waste incinerator increases cancer risk to a very high one in 1,000. For practical reasons, the researchers will likely not have measured the extent to which the studied individuals have been exposed to emissions from the incinerator.