As we’ve mentioned previously, secondhand smoke was conjured up by the World Health Organization in the 1970’s as a way to guilt smokers, influence their behavior, and to “justify” laws against them. Studies weren’t actually done on the subject until later. So what methods do such studies rely on?
A truly scientific epidemiology study on passive smoking would be conducted as follows: Non-smokers would be randomly assigned to groups which were then exposed or not exposed to a measurable quantity of SHS for a length of time long enough for the potential development of disease.
But a scientific experiment such as this is impossible, because it would be not only be unpractical, but unethical.
“Epidemiological observations…have serious disadvantages…They can seldom be made according to the strict requirements of experimental science and therefore may be open to a variety of interpretations. A particular factor may be associated with some disease merely because of its association with some other factor that causes the disease, or the association may be an artifact due to some systematic bias in the information system.”–The Causes of Cancer, JNCI 66:1192-1312