Brain tumor cluster in Melbourne

5 Royal Melbourne Institute of Technology staff report brain tumors since mid-April

A Melbourne university has emptied the top floors of one of its buildings after a spate of brain-tumour cases were reported during the past month. Most affected staff worked on the top floor, raising fears that cell-phone masts on top of the building are responsible. But experts say it is far more likely to be an unfortunate coincidence.

2 additional cases have been reported since 1999; 2 malignant, and 5 benign. 6 of the 7 cases have worked in the building for over a decade, mainly on the top floor, and there are mobile-phone-transmitter towers atop the building.

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So, a few things. First, is this really a "cluster"? If so, is it due to a single exposure--such as radiation (or infectious agents, which they do mention in the article as well)?

They note some reasons to doubt that this is an "epidemic" of brain tumors due to a common cause. For one, they note that the tumors are very different from one another, and that "only three of the seven types have known associations with radiation." Genetic predisposition may also play a role, and other confounders need to be taken into consideration when investigating radiation, especially as a cause. Since these people worked together (most of them for a lengthy time period), they breathed the same air, likely drank the same water, etc. From the news report, it seems they're investigating all of that. They also mention that they measured the radiofrequency levels in the building, and found them to be "extremely low," suggesting that even if these cases are from a common source, it may be something other than the towers. (Of course, whether these levels have been "extremely low" for the past decade is another area they'd want to investigate, if they have measurements taken during that time).

Additionally, I don't have any information on the number of people who worked in this building. My initial question is, is an incidence of 7 cases in the last 7 years far above what would be expected? Is it 7 out of 100 employees, or 1000? (According to the May 13 entry here, it's a 17-story building, so I'd assume it's pretty well-populated). It seems like a lot because the 5 of them popped up just recently, but this could just be a statistical blip. It's in our nature to look for patterns to events, but sometimes things are just a coincidence. They also note that these cases weren't found in a systematic manner (screening all employees for adverse health conditions, for example), but were reported coincidentally. That makes it more difficult to know whether these 5 new cases are really an anomaly, or if these types of tumors have been appearing regularly in university staff.

The story says that the university is expected to release its findings next week--like most preliminary data, it will probably raise as many questions as it answers. It'll be interesting to see what they find.