>> Let me state the assumptions here:
>>
>> 1. The throat cancer rate in Amsterdam is unusually high (statistic).
>> 2. Excessive use of a certain herb may be a causative agent in the
>> formation of throat cancer (statistical link).
>> 3. Usage of the herb by natives is no higher in Amsterdam than in the
>> rest of Europe (assumed from statistic).
>> 4. Usage of the herb by transients is higer than natives h in
Amsterdam
>> (statistic).
>>
>> And from this the conclusion was reached that the throat cancer rate
is
>> caused by the transients (?)
>>
>
>I would say start looking for another causative agent, unless
the
>cultivation practices in Amsterdam are markedly different
from
>elsewhere. Now, if even a small but measurable percentage
of
>growers that supply the Amsterdam market used things like DDT, etc
in
>cultivating the herb, then there would of course be some sort of
basis
>for the claim, but since the number of people using herb is
consistent
>with other locations, then I would not expect to see a link with
herb
>unless the herb there were different. As for transients, since
throat
>cancer isn't a condition which just pops up overnight, but
requires
>years of adverse behavior to create, then I would hardly expect to
see
>transients going to Amsterdam, smoking up, and coming down
with
>throat tumors in the course of a normal vacation.
Exactly - pretty much what I was getting at.
>Now, if Amsterdam had excellent cancer treatment facilities, and
low
>cost health care, most probably socialized, then I would expect to
see
>people move into the area in order to get quality health care
treatment
>for no cost.
>Having an asset like a skill in a special area tends to attract
customers
>for that service.
Certainly a workable hypothesis for a study, assuming Amsterdam does have superior health care facitities.
Another possibility is the cobined factors of age and smoking - anecdotally, from what I remember when I used to live in Groningen (a small city in the northern part of the Netherlands), almost every person above the age of 40 seemed to smoke. The period of time that one has smoked tobacco and subsequent development of throat cancer are highly correlated. As a result, I would expect older populations with a history of tobacco use to have a higher incidence of throat cancer.