But the odds of any random cluster of medical anomolies is much higher.
My wife and I are in our 70s and we have both been previously widowed. Both our spouses died in their early 40s of brain tumors. We did NOT meet in any way related to our spouses’ deaths.
If this was a TV show and the manner of death was not so obviously beyond our control, I imagine we would have been under suspicion for some time.
All of that math is nonsense.
Because you forgot to include everyone everywhere in every workplace and occupation. If it was 5 policemen from Tucson with stomach cancer (or piles) that would have been what the article was about. Groups of 5 with any seeming newsworthy commonality at all are the numerator here. Not just that one particular group of 5 nurses at that particular hospital. And 380 million people create all sorts of groups of 5 every day.
Probability is hard.
It is indeed.
Obviously my numbers are made up, but if you go with the general population, then they’re not insane (aside from being made up). But yes, narrowing down the population to “nurses at hospital X” or “policemen from Tucson” absolutely affects things, because they have some commonalities that affect their risk.
if one of those groups has a higher rate of piles or skin cancer or bunions or whatever, that might suggest there’s something about their group that poses a higher risk. Policemen are on their feet a lot = bunions. Nurses are around medications - who knows what tiny incidental exposures do, over a long period of time. And so on.
A more useful population for the purposes of the article would be “all nurses at that hospital who live in the southwestern part of the city”, “all staff at that hospital”, or “all nurses in general”. If you survey every nurse working in a maternity ward anywhere in the US, the 1/10,000 gen pop rate might actually be, say, 1/1000 that have developed some kind of brain tumor.
Using that figure, the odds of 5 in one place having brain tumors would still seem to be pretty low.
In any case, the article really doesn’t do the (possible) problem justice. It’s more sensationalism than good journalism.
I’ve often speculated that one of the leading causes of death in our country is living in the same town as such-and-such character.
Certainly seems to be the case in Cabot Cove, Maine. 
'Zactly.
What lights my fire is the rush to judgement that “Since this group of 5 people had superficially similar events, the events must have a common cause. Which common cause therefore must be an active hazard to everyone else similarly situated.”
Leading to silly things like the call upthread to shut down the entire hospital until the cause is uncovered. Which implies leaving it shut down forever if that cause isn’t found. Because that cause must exist, therefore finding nothing cannot be evidence of no cause; it must be evidence only of inadequate searching.
Probability is very hard for people to grasp. At scale, a one in a million event occurs every few minutes. At serious scale, maybe several times per second.
Yeah, it’s pretty broad. And different kinds of tumors are triggered by different things.
If they all had the same diagnosis, i would think it was a smoking gun. But they don’t. So my money is on random chance.
That redefines, “a run of bad luck”. 
Yeah, coincidence is a much more likely explanation than an actual common cause. Like, I just drew the hand of JH, AS, 2H, QH, 8C. Wow, what a coincidence! The odds of that hand are only 1 in 2,598,960! And yet, for some reason, none of you are amazed at that hand, because it’s not considered a remarkable one.
So the real question isn’t “What are the odds?”, it’s “what do humans consider remarkable enough to even care about the odds?”.
Yes, this. Back when I was working in high volume cell phone design and production, it became pretty clear that a 1 in a million event happens quite often, when viewed from the total number of usages possible.
They should also investigate whether the 5 nurses met together outside of the hospital, in a high-risk location—like attending a medical conference in Chernobyl.
Workmates often meet outside the workplace.
Exact they didn’t all get the “exact same disease”. From further upthread:
Different types of brain tumor have different causes and different prognosis.
As I said before this certainly should be investigated but it is possible this is a coincidence and not something sinister or preventable. It’s impossible to know for sure with the information given.
The other thing is that a lot of people are walking around with benign tumors and oddities while totally unaware of it, and will likely never be bothered by them. When you start screening people, though, you start finding these things. Many of which require no treatment at all but that can be a source of anxiety because now they’re known to exist.
A quick google indicates an overall brain tumor rate in the US of about 25 cases per 100,000 (or about 2.5 per 10,000) of which roughly 6-7 are some form of cancer and 17-18 are benign (in the non-cancer sense, they might be life-threatening for other reasons… or never cause a problem) just in case someone wants to do the math for more real-world numbers.
That was my take on it.
Yes, as I mentioned earlier, apart from inherited susceptibility there is scant evidence of environmental triggers for benign brain tumors, apart from childhood radiation exposure and adult radiation therapy for meningiomas. For other relatively common benign brain tumors (acoustic schwannomas and pituitary adenomas), there don’t seem to be any established environmental causes.
It’s now up to six.
A line in this article caught my attention, “OHS has identified six staff members who have worked for varying durations on the fifth floor and report developing benign (non-cancerous) brain tumors” (emphasis mine). So our sample population is not just the nurses who work on the floor now, but also any that worked there for any period of time in the past.
Much of this thread has been about how this could all be a coincidence, and I do agree. However, just because it could be a coincidence, does not mean it is a coincidence. Dangerous environments and disease clusters exist, are real things, and it is not a waste of resources to investigate.
This isn’t helping the case, though:
Staff members have raised several concerns about this cluster of cases. The hospital has addressed questions about whether brain tumor cases can be related to: wearing masks during the pandemic, the drinking water, use of x-rays, or the pharmacy on the floor below
(emphasis mine, again). Unless those masks are being stored in formaldehyde, I really don’t think masking during the pandemic was causing brain tumors, and masking during surgery somehow doesn’t cause brain tumors?
I don’t think we can tell from the article whether the supposed issue was mask-wearing in general or something about the particular masks that those nurses had to wear.
I had a whole parenthetical I deleted about maybe sub-par, toxic masks used during the initial mask shortage of the pandemic could genuinely be a problem. “We recycled masks by sterilizing them with benzene!”
But that’s not what is going on when people complain about being forced to wear a mask. People don’t like being told what to do, and masks are uncomfortable, so we end up with lots of made up reasons about why mask wearing is dangerous or ineffective.
I, uh, read that bit as sarcasm.
I think there’s a layperson’s error in lumping together things that seem superficially similar. It’s not just here “brain tumor”! OMG! It’s something that annoys me all the time when people talk about finding “the” cause of autism. I am pretty sure that if we ever do find out, what we’ll find out is that autism is like blindness or deafness-- lots of different causes. And like cancer too, for that matter.
So laypeople hear “brain tumor,” and think everyone has the same thing, from the same cause-- and they’d probably still think that even if some were benign, and some were malignant. All they hear is “brain tumor”! 
I did not. But your interpretation is certainly reasonable.
Well @Velocity, which way did you mean?
You’re talking about the guy who is self-treating because he thinks he’s been infiltrated by toxic mold which has penetrated his blood-brain barrier (if I’m remembering correctly)?