Rhinocrisy

A few weeks back I happened across a news story trumpeting a link between cell phones and brain tumors, containing the ominous warning that cell phones are “worse than cigarettes”. By coincidence my roommate had happened to ask me if I knew anything about the subject, and so I spent a portion of the previous day scouring PubMed to answer this very question, and had, of course, also compared against cigarettes as the outstanding example of a public-health disaster caused by personal foibles.

So my immediate reaction to the story (”Balls.”) was based on more than just a gut feeling.

But let’s start off by poisoning the well a little bit: the source for this story was an Australian neurosurgeon named Vini Khurana. Vini’s methodology in answering this question was exactly the same as mine: reading some papers on PubMed. We should be clear that reviews are an important part of scientific literature, and they are a great way to collect information and present a perspective on the field. They’re usually the product of specific solicitations by journal editors to respected members of a field - e.g., asking James Hansen to write a review on the global temperature record, or even asking someone like Carl Woese to write a review on the future directions for the entire field of biology. The idea is that someone with a demonstrated expertise in the field is surely best-positioned to report on its history and state-of-the-art.

But no one solicited Vini’s article. In fact, Vini has no history of publication in the field. In fact, Vini didn’t even publish this paper anywhere. It was published on the web and was completely unreviewed.^*

As I’ve suggested before, I think the manner of propagation of many news stories is purely viral: something happens to make it onto some wire service, and if it is interesting or sensational, it spreads. As its exposure increases, so do opportunities for further dissemination - another outlet picks it up, and the cycle continues. This process doesn’t seem to include anything like quality control or actual journalism (mayhap the journalists here can speak to why this might be the case), with the result that bad, bad science gets broadcast loudly around the globe.

At any rate, the question at hand remains to be answered: do cell phones cause brain tumors? After Vini’s own pathetic review, he recommends an actual review in the Journal of Radiation Biology, whose abstract tells us:

Biophysical considerations indicate that there is little theoretical basis for anticipating that RF energy would have significant biological effects at the power levels used by modern mobile phones and their base station antennas. The epidemiological evidence for a causal association between cancer and RF energy is weak and limited. Animal studies have provided no consistent evidence that exposure to RF energy at non-thermal intensities causes or promotes cancer. Extensive in vitro studies have found no consistent evidence of genotoxic potential, but in vitro studies assessing the epigenetic potential of RF energy are limited. Overall, a weight-of-evidence evaluation shows that the current evidence for a causal association between cancer and exposure to RF energy is weak and unconvincing.

That first sentence, by the way, is an important one: there’s little justification for the notion of non-ionizing radiation being a significant cause of DNA damage.

Meanwhile, a simple comparison of some epidemiological studies on the question is revealing. This study finds odds ratios of 1.22 and 0.70 for gliomas and menigiomas respectively. This one finds an odds ratio of 0.6 for gliomas, with a 95% confidence interval of 0.4-0.9. I.e., the study finds that regular cell phone use is slightly protective against gliomas! And finally, this study examines both long- and short-term users of cell phones and finds no increased odds of acquiring tumors through phone use in either group.

By now you are probably shivering in your boots^†, so let’s take you back down a little, with a sentence from this case-control study:

The odds ratio (OR) for lung cancer in current United States smokers relative to nonsmokers was 40.4.

The short version: As you were, lieutenant.

^* Yes, reviews are normally reviewed. The reviewers of reviews are called re-reviewers, and they are required to do their reviewing work between two facing mirrors to deepen their powers of meta-analysis.

^† You are wearing your boots, right?

One of our most popular posts, google-wise, is hedgehog’s missive about the health effects of bisphenol-A, a common ingredient in many plastics. I happened across a nice letter in PLoS Biology, written by Rebecca Roberts, describing her fears as a new mother on her child’s exposure to BPA. Included is a nice summary and references for some of the research supporting the need for tighter regulation (some say banning) of BPA in plastic products, especially with regards to kids, and a chronicle of the failed legislative efforts at removing it.

While we’re setting fire to myths, I might as well weigh in on this whole autism/vaccination thing, which I’ve been intending to write about for months. Recently Jenny McCarthy (no pictures, sorry) appeared on the Oprah Winfrey (no pictures, sorry) show, along with Holly Robinson Peete (Earthquake, 2004) to discuss autism. Both are mothers of autistic children. Jenny told the following horror story about how she believes her son Evan became autistic:

“Right before his MMR shot, I said to the doctor, “I have a very bad feeling about this shot. This is the autism shot, isn’t it?’ And he said, ‘No, that is ridiculous. It is a mother’s desperate attempt to blame something,’ and he swore at me, and then the nurse gave [Evan] the shot,” she says. “And I remember going, ‘Oh, God, I hope he’s right.’ And soon thereafter-boom-the soul’s gone from his eyes.”

Chilling, indeed. But - do we believe it? Read the rest of this entry »

This story documents some interesting research — turns out that rather than dedicate vast tracts of land to fueling cars, it would make more sense from a carbon point of view to let the farms revert to forest and continue using fossil fuels for cars.

I took a long trip up to Montreal to visit my best friend Thomas, who is a painter. Pride compels me to post a link to some of his stuff. There’s a lot that could be said about that; our conversations tend to be incredibly dense and traverse a great deal of territory. But I’ll leave that aside and instead speak about my trip:
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Next time someone asks you what studying evolution has ever done for humankind, you can tell them: “It cures AIDS, Biyotch!”

Whether that’s true is unclear at the moment, but still, this is insanely cool stuff. The Cre/lox system is a well-known tool in the molecular biologist’s napsack. It’s a very simple system that developed in the bacteriophage^* P1. Many phage have the same basic strategy for replication that HIV does - integrate yourself into the host genome. The host then goes through repeated cycles of replication, copying the phage DNA in the process. At the right time, it expresses Cre recombinases, which recognize the two identical “loxP”^† sites flanking the inserted phage genome, neatly excise the intervening viral DNA and stitch together the flanking sequences.
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In the “Stuff you can’t make up” department, the head of the WHO’s HIV/AIDS program, which today announced that men should be circumcised in order to reduce their chance of getting HIV by 60%, is named Kevin De Cock.

I’m not sure how I feel about the recommendation myself. Actually, I can tell you that my immediate reaction was anger, before I read the study, which makes it clear that the effect is almost certainly real (that is, attributable directly to the circumcision and not attendant factors). It seems risky in the extreme to pin a lot of emphasis on something with a relatively modest effect if it’s only going to result in more risk-taking behavior. It’s also not cheap at all to circumcise everyone in sub-Saharan Africa (it costs $50-100 a slice), which means it’s arguably a big waste of money as well. But maybe they know what they’re talking about - I’m not a public health specialist.

This is a typical conversation in my kitchen:

I’m currently watching the first season of Battlestar Galactica, usually while cooking dinner. The premise of the show is that an evil race of robots destroys almost the entire human race, leaving only a small population of 50,000 individuals alive.

This immediately prompted us to pause the movie and launch into a discussion of the population genetics implications of such a crash.

Now, contrary to conventional wisdom, there is a huge difference between the actual and apparent genetic size of a population. That is, even though there are 6 billion people on this planet, human beings are remarkably genetically uniform; in fact, they show the amount of variation one would expect from a much smaller ideal population. This discrepancy leads population geneticists to speak of a quantity called effective population size - in the case of humans, about 10,000 individuals. This is such a small number because, first, there is population structure that prevents truly random mating between all individuals in the population, and, second, the human population has undergone at least a few “bottlenecks” - instances of dramatic population collapses - and the ancestral population was probably considerably smaller than the modern population. Thus, the amount of actual variation in our population is low.

A bit of Googling around led us to a paper by Masatoshi Nei, wherein he describes simulations of population crashes and subsequent rapid expansion. The upshot is: even absurdly unrealistic population crashes (down to N=2 individuals) do not eliminate most of the variation. I think in that extreme instance, the reduction was only from 15% down to 8% - so long as your 2 individuals are randomly selected, of course. This is pretty remarkable, and it suggests that the immediate problem will not be fitness loss from low genetic variation - you’ll lose most rare, private variations (variation that only exists in you & your immediate relatives, e.g.), but most of this stuff is unimportant or even harmful. What WILL be retained is the bulk of frequent variation - stuff that is either beneficial or neutral, and so has not been eliminated by purifying selection. Of course, it takes on the order of 1/(mutation rate) generations (10⁸) to recover your initial level of variation, but never mind that. We’re merely concerned with survival, here.

The second problem is inbreeding depression. This is exactly what it sounds like: when you have babies with your parent or sibling, you’re much more likely to encounter severe recessive phenotypes that drastically reduce fitness. Note that this is a DIFFERENT problem from low genetic variation - I am genetically not all too distant from anyone on earth, but inbreeding depression results mostly from the expression of rare, private variation that no one else has - except my relatives.

So, after a bottleneck, inbreeding depression will surely be a problem. This possibly results in ‘purging’, that is, the speedy elimination of deleterious variation via selection in a highly homozygous/inbred population. This puts pressure on the population - inbreeding load - fewer individuals are surviving and the general fitness of the population is lower. Populations may founder at this stage, although purging is believed to result in a rapid recovery of fitness.

At any rate, 50,000 individuals is, in genetic terms, a great many, and I’m pretty certain that inbreeding depression would not be a severe problem in such a population (especially if they’re all free to mingle as the Galactica population would be).

Last night’s conversation included: group selection in chickens and its eugenics implications, a recitation of some Hindu mythology (mostly the Avatars of Vishnu), some tales of the Buddha and other Zen masters, the story of Kalidas, a discussion of the Inquisition as viewed by the book Demon Lovers, and Hitler’s vegetarianism. The evening culminated with us watching Triumph des Willens.^*

Continuing our series, “Creatures that exist on this planet that you^* never even fucking HEARD of”, I present the babirusa, the pig-deer of Indonesia. Check out this tusk arrangement! Spectacular. Those secondary tusks are actually their upper canines, which curve back and grow through their skulls. Ow! Impacted.