Re: Brain Tumor Statistics: How to Determine if a Cluster Exists

Wow! That's indeed a surprising number of people to have independently developed tumors, especially so close to one another. There are some things you should keep in mind before jumping to conclusions about the water, though.

Environmental factors aren't the only, or even the biggest, cause of tumors. A person's genetic history is often the biggest risk factor, and though the article didn't give enough details to even speculate, I wouldn't be surprised to find some shared alleles/common ancestry among the affected, given how small the population group is. Another important detail which the news couldn't report is the type of tumor. Depending on the identity of the tumor, which might not be the same among those affected, one can rule out various risk factors.

So what I'm saying is that the appearance of the tumors so closely spaced in time and spread across age groups is concerning, I'm glad the CDC is looking into it, and I wouldn't be surprised to find some environmental exposure turns out to be a primary risk factor, but it's not necessarily time to run for the hills. The CDC's epidemiologists are a sharp bunch of people, and they generally waste no time getting to the bottom of things. If I were doing the investigation, certainly one of the first things I'd look at is if the people have anything in common besides where they live, i.e., with other tumor patients in other areas. But if that turns out to be the case, it'll only make a scientific report, not a newspaper headline.