Getting a D in Health

Greetings, indoor, computer-reader.

The Sunbathing Ape

It's natural for us to feel drawn to amazing photographs of sun-soaked landscapes. We humans evolved as mostly-naked, outdoorsy folks in sunny Africa. Although the cultures (and to some degree the genes) of migrating peoples have done what they can to adapt to more polar environments, if you dig at all deep into our biology you'll see we still aren't fine-tuned to live indoor, boreal lives.

One of the biologically unmet expectations humans in the USA and Canada experience is low sun exposure, leading to Vitamin D deficiency. This article in the Globe and Mail suggests that Canadians typically have about one third of optimal concentrations of vitamin D in their bloodstream.

What's D Good For?

Until recently, it was thought that the major effect of vitamin D deficiency was rickets. Since (last time I checked) rickets wasn't an endemic problem to North Americans, vitamin D was seen as being a non-issue; the mandated additions of D and A to dairy products seemed to be sufficient to keep bone formation normal in children.

However, vitamin D has more functions than merely the regulation of bone density. It's also an important chemical precursor to a lot of important cellular signaling mechanisms: not having sufficient vitamin D is the equivalent of trying to run a government when there's a shortage of notepads to write on.

D and Cancer Rates

One of the worst consequences of screwing up chemical messages is to impede natural anti-cancer cellular mechanisms. Does our D-prived culture result in fact in increased cancer rates? The only way to know for sure is with a double-blind experiment where groups are given vitamin D and placebos at random, and to track prevalence of cancers in the two groups. That's exactly what this study did, and what they found is almost unbelievable. Giving 1.5g supplemental Calcium with 1100 IU per day (about 3 liters of milk worth, but the study used pills) decreased cancer rates by 77% after one year.

Great moons of Neptune! That's a huge decrease! The cautious part of me finds it hard to believe that one factor could be responsible for over half of cancers, and to be fair the study tracked only 1200 women over 4 years, and thus wasn't able to notice enough cases of cancer to have really tight confidence intervals: the range of cancer decreases still consistent with the study is 91%-40% 19 times out of 20. Still, I've started feeding vitamin D to my wife as well as taking it, if not daily, than at least often.

Public Health Consequences

Suppose the study's numbers bear up, and that about half of cancers could be prevented by 1100 IU of vitamin D per day. Would it be a good policy for health insurers (or friendly socialist governments like Canada's) to simply hand out vitamin D supplements? It looks like the cost of vitamin D is pretty much nothing: this bottle of 250 pills (almost a year's supply) with 1000 IU of vitamin D is only $10. On the flipside, the annual cancer rate in the US is 1 in 200. If that could be halved by the D supplement, and if treatment costs on average $40 000, that's an expected savings of $100 per year. Pay one dollar into prevention, get 10 out in unneeded treatment. (Oh, then there's the whole increase in lifespan and quality of life issue too.)

Last Word

I suppose the cautious policy approach would be to conduct a larger study to figure out where within the wide confidence interval the truth lies. However, I'm inclined to start ramping up vitamin D production and consumption programs, maybe even with heavy subsidy by governments, HMOs or otherwise. Let's get a D in health.

Cookie Dough: Cold Killer?

Greetings, bowl-lickers.

A friend of mine who enjoys the odd clandestine spoonful of uncooked cookie dough suggested to me last night that I look into the risks involved in his filthy habit. (Just kidding - I regularly eat raw cookie dough by the scoop.)

We're told never to eat cookie dough because raw eggs may contain the bacterium Salmonella enterica, which can make you sick. Despite all the warnings, cookie dough eating is rampant in North America. Does cookie dough cause widespread poisoning deaths, or is it just another paper tiger? Read on to find out.



Salmonellosis: Symptoms and Rates

Any medical condition with a Latin name sounds scary. However, the majority of Salmonella infections cause gastro-intestinal upset and a fever for 4 to 7 days and then go away without formal medical intervention. If you're old, an infant, or have a weak immune system, you could need antibiotics to make your infection go away, and a particularly bad Salmonella infection can cause lasting conditions like arthritis or death. However, these big-ticket fears are relatively uncommon; this CDC study says the ratio of illnesses to hospitalizations to deaths for nontyphoidal salmonellosis is roughly 2,426 to 28 to 1.

The same CDC study estimates that the number of cases of salmonellosis in the United States is about 182 000 per year, or about 1 in 1 500; but since most infections go unreported it's really hard to tell. Its best guess is that salmonellosis from shell eggs causes about 2000 hospitalizations and 70 deaths per year: in other words, salmonella from eggs is about 1000 times less deadly than the flu (from this .pdf, page 2; this comparison is apt since both flu and salmonellosis are grave threats mostly to people with compromised immune systems).

Is Cookie Dough a Big Culprit?

Most of the salmonellosis outbreaks that make the news come from large-scale slip-ups where dozens of people get ill, rather than from small families tasting the occasional batch of cookie dough. Is this just because it takes a certain number of cases before a story is newsworthy, or is there another cause at work?

This CDC page warns that in large-batch recipes where 500 eggs are used the Salmonella risk is greater, since one contaminated egg could taint the whole batch. So what's the risk of getting salmonellosis from eating cookie dough from a two-egg recipe?

This study estimates that only 1 in 30 000 eggs is potentially contaminated with Salmonella, so at most there is a 1 in 15 000 chance that your dough is going to have any Salmonella bacteria. (If the first egg doesn't have Salmonella, the second egg has a smaller than 1 in 30 000 chance of having it too, so 1 in 15 000 is an over-estimate of the risk.) Assuming that it's certain that you will catch an infection from tainted dough, that puts your risk of death from tasting the dough at less than 1 in 36 million; if you have a healthy immune system your risk is considerably smaller. The daily chance of getting a flu as bad as a non-fatal flu-like Salmonella infection are 1 in a few hundred, so you really don't need to worry about salmonella from cookie dough: background risk levels are much higher.

EDD, LED and GHAF

Let's put that 1 in 36 million figure in perspective. The Equivalent Driving Distance (EDD) is just under 2 miles (for those new here, that means a 2-mile car trip is as likely to kill you on average as eating 2 raw eggs) and the Life Expectancy Decrease (LED) is less than 37 seconds (eating 2 raw eggs decreases your life expectancy by only 37 seconds - here I assumed on average my readers might have 42 years left in life and divided by 36 million). For more on the LED and EDD risk metrics, see this introductory blog post and this wiki page for recording risk levels.

So on average the risk of being killed by your baking is negligible. But is the fear over-hyped? Considering there are 294 000 Google hits for "salmonella raw eggs America" and only 70 Americans die of Salmonella from raw eggs, the Google Hits per Annual Fatality (GHAF) hype-metric is 4 200: about as high as for West Nile virus. (See an introduction to the GHAF metric here and a list of GHAFs for various risks here.)

Conclusion: Lick On!

Eating cookie dough gives you a negligible risk unless you have a particularly weak immune system. Whip yourself up a batch and eat it all: it really doesn't matter. Oh, and please save me a spoonful while you're at it.

Bon Appetit!

LeDopore

Killer Cellphones?

"Pronto? MoshiMoshi? Hello?"

I was reading Digg today, which pointed me to an article speculating that cellphones are causing "colony collapse disorder," the name for an alarming phenomenon whereby the majority of honeybees in every colony are mysteriously disappearing. (By the way, this isn't jsut about the honey bees produce. The value of their crop pollination is in the billions per year; would anyone like to post a comment with a more exact figure?) The article sounded interesting until they went off the deep end by vilifying cellphones with a few cherry-picked debunked claims:

Evidence of dangers to people from mobile phones is increasing. But proof is still lacking, largely because many of the biggest perils, such as cancer, take decades to show up.

Most research on cancer has so far proved inconclusive. But an official Finnish study found that people who used the phones for more than 10 years were 40 per cent more likely to get a brain tumour on the same side as they held the handset.

Equally alarming, blue-chip Swedish research revealed that radiation from mobile phones killed off brain cells, suggesting that today's teenagers could go senile in the prime of their lives.

Chilling. Let's go into an account of how much damage a cellphone can do, and let me cite a few studies of my own.

Traffic Dangers

We have lots of evidence that cellphones impair driving ability. A University of Utah study found that cellphone conversations impair about as much as a .08% blood alcohol content, the threshold for the legal drunk-driving limit in many North American states. The World Health Organization says talking on a cellphone while driving increases your risk of accidents by a factor of 3 to 4. Taking a 100-mile drive decreases your life expectancy on average by about one hour, i.e., it has and LED of one hour (see posts with the tags LED and EDD for more, or this one which introduces them). Talking on your cellphone bumps the LED up to three or four hours, meaning that the driving-related risk starts to overcome the old-age-related risk you'd incur anyways if you call people while driving.

Other than impairing driving ability (and repetitive stress injuries from thumb-typing), cellphones aren't going to hurt you. Let's take a look first at the physics of cellphones (which will show them to be benign) and then take a look at the epidemiology of cancer among cellphone users, citing the most thorough study ever done, which happens to be Danish (Long Live Fear-Dispelling Vikings!).

The Physics of Cellphones

Cellphones communicate by broadcasting microwaves to cell towers. They use one of two frequency ranges: either about 850 MHz (the PCS band) or about 1900 MHz (the cell band). The peak power of a cellphone's transmission is about 2 Watts, so the amount it broadcasts into your head isn't more than about 1 Watt.

There are three potential concerns which make cellphones potential health risks: heat, chemical damage, and brain interference. Let's assess each potential risk.

Of Cellphones and Sunbeams

It turns out many of you non-hat wearers heat your head with electromagnetic radiation on a daily basis. A fusion-powered blob of gases over 100 million km away bakes your melon with an intensity of over 1000 Watts per square meter on a cloudless day. If the cross-sectional area of your head is about 3% of a square meter, that means the sun warms your head with over 30 times the power intensity of a cellphone. If cellphone-related heat can cause damage, so can the sun.

Mutagenic Conversations?

The next most commonly-feared etiology of cellphone-related cancer is through the photons in the microwaves causing genetic damage by affecting our DNA. However, the energy in even the highest-energy cellphone photons is far too low: a 1900 MHz photon has an energy of less than 8 microelectronvolts: about 100 000 times less energetic than the kind of photon needed to make any chemical change. At body temperature, random thermal fluctuations give every molecule constant kicks of over 25 millielectron volts: over 1000 times as powerful as a cellphone photon. No cellphone is going to turn you into a toxic avenger.

Nokia Mind Control?

I've seen one more way in which fear-mongers propose that cellphones could harm you:. They think it's possible that the pulses of electromagnetic energy could interfere with brain functions. It's true that neuroscientists use pulses of transcranial magnetic energy to temporarily (and, we hope, reversibly) poke an area of gray matter to try to figure out what it does. Could cellphones be doing the same?

Again, the relative magnitudes are way off: neuroscientists use field strengths around 10 Tesla, while cellphones typically have much smaller magnetic field strengths: around 50 Gauss or 5 mTesla (1 Tesla = 10 000 Gauss: one of those Metric System anomalies). Once again there's a yawning, factor-of-1000 gulf between the strength of a cellphone and the effect size needed to make worrying sane. It's even worse when you take into account the fact that the energy associated with a magnetic field goes as the square of the field strength, so it's more like a factor-of-1-million difference between what a cellphone is and what we'd worry about.

Epidemiology

By now, it shouldn't surprise you to find that the most extensive study done on cellphones (the Danish one I alluded to) "found no evidence for an association between tumor risk and cellular telephone use among either short-term or long-term users." The study followed 420 095 persons for up to 21 years each, and saw that cancer rates were not higher than among the population in general. Breath a sigh of relief, and don't believe the fear-mongers who say cellphones are risky.

What about studies which show a correlation between cancer and cellphone use? There's a dirty little secret in science called publication bias. In a nutshell, it's precisely those stories which seem to defy common thinking which seem most newsworthy, get the most press, and get published. In cases where there's a lot of public interest and attention, it's a good policy to disregard studies with small sample sizes, since there are probably 20 unpublished small studies with null results for every 1 study with a stunning effect that's significant at the 5% level.

Conclusions

I don't know that much about bees, but cellphones are safe to humans, provided that their attention isn't needed elsewhere and that it doesn't over-stress them to have a cellphone. It's not totally outrageous to guess bees might be confused by cellphones, since the Earth's magnetic field is only about 0.3 Gauss. I'm not an expert of bee navigation, but it shouldn't be to hard to experimentally verify the connection between active cellphones and bee death. In the meantime, color me skeptical, especially considering that the article repeats loony fears.

Today's Oxymoron: Airport Security

Greetings, passengers.

Show of hands: how many of you out there feel safer due to the airport security measures which supposedly keep bombs off planes? If you raised your hand you must think both that there are plenty of terrorists who try to bring down planes, but that the security checkpoints are in general pretty good at keeping them out. In this post, I hope to disabuse you of both of these notions.

First of all let me vent a little. I'm sick and tired of people talking about terrorists in general terms. I hear it all the time: "terrorists look just like us," "terrorists think what bringing down planes is God's will," and other such phrases which imply that there are enough terrorists to lump them into a uniform seething pile of hatred.

In truth, there are very few terrorists in the United States. When was the last time you heard about a US plane hijacking? Terrorism just isn't a big enough threat to justify its looming shadow over the US psyche.

The 90% Hole in the Airport Security Net

Why am I so sure that there aren't dozens of annual attempts at bringing down planes which we don't hear about due to the covert actions of TSA officials who anonymously shield us? It turns out security is regularly audited by undercover teams of agents who try to smuggle bomb-like devices aboard planes, and they succeeded in about 90% of post-September 11 2001 attempts, as reported here.

The take-home message is that the world doesn't hate us as much as militant politicians want us to believe. If about 90% of attempted plane bombings would be successful and yet US passenger planes don't regularly explode, we're left with no other conclusion than airline terrorism is exceedingly rare. If there's been one take-off for every 5 seconds since September 11, that's more than 30 million terrorism-free flights.

Conclusions

We're safe in the air, not because of an army of screeners, but because people don't hate Americans as much as we're told. Now, dear readers, could you let me know if you think our paranoia over plane bombing is just garden-variety misplaced fear, or does it come from a conspiracy of plutocrats in a position to profit from it?

The Google Hype-Meter

Greetings, West Nile mosquito-swatters.

I hope that by now you will be familiar with my style of putting over-hyped risks in their place. But how do you determine how over-hyped a problem is? Today I'm going to introduce a new metric to assess how out-of-proportion a particular death threat is: the Google Hits per Annual Fatality or GHAF metric.

Google and Hype

First of all, let me admit that reducing such a nebulous idea as "hype" to a number is an inexact science at best. However, I happen to be an inexact scientist: the perfect blogger for the job.

The people who post web content are not representative of the human race as a whole, so if there's something which netizens preferentially talk about, Google is going to reflect that bias. However, in most cases this bias will distort reality by at most about a factor of 10, so any enormous differences in the whole-world hype devoted to certain risk factors should be also present in a subject's Internet chatter. Luckily, some small risks are so enormously exaggerated that even an inexact measure like the GHAF can find them with confidence.

Calculating the GHAF

So, if we're agreed that Google hits will approximate the amount of talk on a subject, we can divide the number of hits by the annual death rate of a scare to get the GHAF, a relative measure of how much that particular problem has been overblown. Let's take a look at a few real-world examples of the GHAF.

Raw Data

• Malaria in Africa (GHAF = 1.5, 3 million Google hits [1] per approximately 2 million annual deaths [2])
  
• Cancer in the United States (GHAF = 94, 54 million hits [3] per 570 280 annual deaths: page 1 of [4], .pdf warning: 6 MB)
• West Nile Virus in the United States (GHAF = 5 500, 911 000 hits [5] per 165 annual deaths [6])
• vCJD, the human disease from eating a mad cow, worldwide (GHAF = 81 000, 1.4 million hits [7] for 139 cases over 8 years [8] - see my blog entry for an editorial[9])
  
• Alligator Attacks in the United States (GHAF = 293 000, 461 000 hits [10] per 1.57 annual deaths [11] - possibly the fatality rate is underestimated by this list and possibly a lot of the Google hits came from attacks on non-human targets)
  

Summary

The GHAF hype metric has a huge variability. It is a few thousand time greater for West Nile in the US than for malaria in Africa. Working from the assumption that most human life should be treated with roughly the same degree of care, these wildly differing GHAFs indicate that we spend far too much time worrying about the wrong things. With the GHAF, we can measure just how skewed our fears are.

The above list is far from exhaustive; does anybody want to look into adding traffic deaths or killer bees? I've set up a wiki page to keep track of the GHAFs of various risks. Feel free to add to it!

In any case, there's a huge variation in how much hype a risk gets compared with the actual danger involved. I realize there are only so many articles one can read about a certain risk before becoming inured to it, so one would expect the GHAF to be lower for real risks as not as much press will go to the millionth victim as to the first. However, the number of Google hits a risk gets is not even an increasing function of associated body count, showing that our problems run deeper that just weariness over old news.

Conclusions

I've already introduced two new measures of danger, the life expectancy decrease (LED) and the equivalent driving distance (EDD). However, these measures only ask how dangerous an activity is; they do not report how much that danger has been magnified by the media. With the GHAF, we can quantify just how out-of-proportion the hype is around a certain fear, and perhaps allow this measure of exaggeration to shape policy.

I look forward to your additions to my wiki page. What will my intelligent readers discover?

Warning Labels on Soda Pt 2: the Real Risk

Greetings, fellow nerds.

Last post, I ridiculed the warnings on the side of 2 liter soda bottles; in-depth studies did not find a single instance of them causing any serious eye injury. Today I'm going to estimate your health risks once the bottle is open.

If the soda you bought wasn't diet, then it's loaded with one of American nutritionists' worst nightmares: high fructose corn syrup (HFCS). HFCS is the most common caloric sweetener in soft drinks in the United States, in part because agricultural corn subsidies make corn plentiful and cheap.

HFCS: Empty Calories Without Filling You Up

It's a real shame that corn was chosen as the US's crutch crop, because HFCS happens to be not just pure sugar, but it's a kind of stealth sugar which doesn't make you feel less hungry. HFCS calories then don't displace other calories in your diet.

In the year 2000, a study was undertaken where human subjects were made to consume 450-calorie portions of either soda or jelly beans on a daily basis. Whereas the jelly bean-eating group ate fewer calories to compensate for the fact that they had to eat jelly beans (if only I were a five-year-old when this study started - talk about your dream job!), the soda-drinking group's appetite did not decrease at all - in fact drinking soda may have increased the subjects' appetite (although this increase was not statistically-significant).

The study I mentioned is not alone: research has shown that HFCS may be a serious culprit in the epidemic of obesity since HFCS can be directly converted to fat easily, and a 2006 summary of recent research has shown sugar-sweetened beverages to be dangerous in cross-sectional, prospective and experimental studies.

There is a mountain of scientific evidence that drinking HFCS in soda is bad for you. There's even been talk of putting a Surgeon General's warning on soda cans, since they are so unhealthy. How unhealthy are they? Here's my estimate.

Health Impact of the HFCS in Soda

If you drink that 2L bottle of non-diet soda, you're adding its whole 1000 calories to your diet, since HFCS doesn't fill you up. According to an earlier estimation of mine, eating 800 extra calories has a 94 in a million chance of killing you, which makes the risk associated with consuming a single soda bottle is about 118 in a million: there's a greater than 1 in 10,000 chance that drinking a 2L bottle of non-diet soda will kill you in the following 15 years.

Conclusion

Drinking the soda in a 2L bottle is at least one million times more risky than opening the bottle. Yet, the warning label on the bottle is for the latter, not the former. I wonder if maybe the label is there to try to assure us that the most dangerous part of enjoying the soda is opening it, lulling us into a false sense of security. In any case, once again we see that Americans are concerned with the wrong risks. Let's stop fear-mongering about things which won't hurt us and try to educate ourselves about things that might.

PS I've added drinking 2L of HFCS soda to the ever-expanding risk list wiki. So far, it's the first activity to warrant a yellow alert.

EDIT: I've added the life expectancy decrease (LED) and equivalent driving distance (EDD) metrics to this post. See this post for an introduction to the LED and EDD.

If consuming a 2L bottle of non-diet soda has a 118 in a million chance of killing you within 15 years, then its EDD is (1 billion miles / 14.6 * 118 / 1 million) = over 8,000 miles. So, it's safer to drive for 8000 miles than to consume a 2L bottle of non-diet soda.

The LED is (80 years * 118 / 1 million) = about 3 and a half days: enough to give you pause.

Under Pressure: Attack of the Killer Soda Pop

Greetings, fellow nerds.

If you consume soft drinks in the United States, chances are that you've noticed that this warning has begun to appear on two liter soda bottles. When I first saw it, I could hardly believe my eyes. I find it hard to imagine what possible circumstances could conspire to cause the cap to blow off with enough force to do bodily harm. So why the warning label? Does it really help, or is it just the brainchild of a misdirected torte lawyer?

I'm going to argue that the real dangers of soda come from drinking it, not opening the lid. I'm going to expose how skewed our senses of risk and responsibility are by showing that the high fructose corn syrup in soda does far more damage than its allegedly explosive top. This post will cover the risks of getting blinded by a rocketing soda pop top, while the next one will look into the health consequences of drinking that same soda.

The Letter Never Sent

When I set out to uncover the statistics behind the warning labels on soft drink bottles, I had imagined having to write to a representative of some bottling authority with a request for statistics on eye injury resulting from opening plastic bottles. I'd say my friends and I are casually interested in why these warning labels were deemed necessary, and ask for the reasoning behind the warnings.

I was kind of looking forward to composing the letter. Setting the right tone would be key: I'd have to come across as earnest while acknowledging the whimsical nature of my request. Usually, public relations people at corporations give you the benefit of the doubt and respond in good faith. However, it turns out injury statistics from soda bottles are well-known and published, so writing is unnecessary. I might still write that letter; if you'd like me to carry through with this plan let me know in a comment.

The Answer's Before Our Eyes

I'm not planning on writing the above letter because the British Journal of Optometry has already answered my question. In this publication (.pdf warning), titled “Serious eye injuries caused by bottles containing carbonated drinks”, they say “plastic and metal cans pose little danger: we found no related injury among the 12 889 cases.” Their database held combined data from the US, Hungarian and Mexican eye injuries from 1982 – 2002 (although it didn't have data for all countries and all years).

The paper's authors (F Kuhn, V Mester, R Morris and J Dalma) found not one instance of a soda pop bottle causing an eye injury in any of the countries in any year. It would be a stretch to say that absolutely no eye injuries happened because of pop bottles during the 1982-1999 period in the States (2000-2002 US data not published in Kuhn et al.) since the database of eye injuries used (USEIR) collects information of only serious eye damage, and not all states of the US contribute data to USEIR yet. Still, the fact that Kuhn et al. found not one case of plastic bottles causing eye damage over a 20 year span is suggestive that they're pretty harmless. If you know of someone who has been injured by a plastic bottle top, please leave me a reply about it.

Incidentally, champagne is not so benign. Kuhn. Et al. mention 43 cases of severe eye injury from sparkling wine corks to the face; the majority of these (37) were in Hungary. The remaining 6 wine cork injuries happened to Americans. If we assume the USEIR reflects only about half of all eye injuries, that's still less than 1 serious American injury per year. (Aside: Does anybody know what Hungarians put in their hooch that makes it so explosive? Kuhn et al. are baffled too.)

I'm Armed and Carbonated

Because I'm a physical sciences nerd, I'm going to figure out how dangerous pop bottle caps could be under ideal firing conditions. Typical soft drinks are pressurized to about 300 kPa. If the surface area of the cap is 3 square cm, the cap is under about 90 Newtons of force, or about 20 pounds. If we assume that some manufacturing error resulted in the cap suddenly becoming loose after a vigorous shaking of the soda at room temperature, this 90 Newtons would act on the cap for as long as the cap blocks the exit path of the gas: about 2 cm. If that 90 Newtons accelerates the cap for 2 cm, the energy transferred to the cap would be only 1.8 Joules. Most accidental cap accidents would be under less-than-ideal launch conditions, so I would be surprised if caps blew off with more than 1 Joule of energy.

How much is 1.8 Joules? About the same amount of energy as a snapped rubber band (one with a spring constant of about 250 N/m), if you stretch it three or four inches. That might sting if it hit you in the eye, but it's not likely to do permanent damage even with a direct hit. It probably wouldn't be too hard to get pop bottles approved as projectile toys for kids old enough not to try to swallow the cap.

In summary, my analysis suggests there isn't enough punch in a plastic bottle cap to do serious harm, and the lack of any evidence of eye injuries backs up my case. From here on in, I'm going to assume that the risk of serious injury from pop bottle tops to consumers (forewarned or no) is 0. Of course it isn't exactly 0, but the Kuhn et al. study covered about 5 billion person-years of exposure to pop bottle tops and didn't find a single serious injury, suggesting an upper bound on the injury rate of about 1 per 10 billion: close enough to 0 not to matter.

Time lost to the warning label

Even though an in-depth study failed to find even one instance of a plastic bottle cap damaging anybody's eye, one might think that it's better to abide by the precautionary principal, that is to warn people of the pressure danger in opening their soda on the off chance that we might prevent even one eye injury. I can imagine the person making the decision to put warnings on all plastic bottles would have a warm, fuzzy feeling if they saved the vision of even one child.

I disagree with the precautionary principal for two reasons. First, the cost of having warning labels is not zero: the precious seconds of our lives we waste worrying about inflated risks add up. Second, ubiquitous, petty, self-important warning labels can inure the public to warnings on genuine risks.

Time Lost Reading Gratuitous Fear-Mongering Messages

How many lifetimes have been wasted reading this warning message? Let's assume that, on average, every American reads this warning once per year. (I don't know if the rest of the world has adopted the warning label yet. Let's hope the insanity has been confined to the Home of the Mega Lawsuit.) If it takes about 10 precious seconds of your life to read through the text, that means that nationwide, about 95 years of life are wasted every year we insist of putting these gratuitous warnings on soda bottles. Equivalently, as you read this, you can expect 95 Americans are busy reading through the above text about how their life is potentially threatened by the intense pressure of the liquid refreshment in their hands.

Think of the good which could be done with those 95 person-years. Movies, novels and poetry written, walks in the park, vacations; all of these and more might have been accomplished if it were not for these unnecessary, attention-whoring portents of soda pop doom. There are some who balk at doing moral algebra. I think that 95 years of vision wasted by eye injury is in principal equivalent to 95 years of vision wasted by reading a warning label.

Since the net effect of the warnings is to decrease the visual lifetime of the consumer, I propose that the soda bottle companies stop printing the warnings. I also propose that we allow companies complete immunity from lawsuits arising from activities whose associated risk is so small that to post warning labels does more net harm than good.

Warnings, Warnings Everywhere...

... nor anyone to think. Perhaps the most damaging consequence of posting warnings on soda pop bottles is that we end up reflexively ignoring them. I hesitate to read every warning label I see (in truth, I didn't even notice this one below until this minute when I started looking for warning labels).

What's on the bottom of my keyboard? Is there a risk of electric shock? Perhaps deadly chemicals leak up from between the keys every midnight. How would I know? I plugged in my keyboard, it worked, and I'm happy. There's no way I'm going to pursue every last nagging, ass-covering warning I see out there, and that means I'll ignore warning signs when there are real dangers too.

I think we should standardize a color-coded warning label system, where different risk orders of magnitude have different colors. You could ignore anything less than a yellow then, unless you were exposed to the risk all the time. Manufacturers would be immune to lawsuits over correctly-labeled risks, and would be made liable for time lost if they grossly overstate the risk. I've started a list of color-coded risks - check out my wiki and add to it if you feel so inclined.

Conclusions

Gratuitous warning labels (such as the one on pop bottles) make us worry about the wrong things. There are genuine risks out there, but the system we have for making people aware of them is broken. We need to push through laws that protect companies from one-off lawsuits caused by the failure to alert customers of excessively-small risks, and then maybe we can talk about demanding that risk labels be removed when the opportunity costs or reading them outweigh the benefit they do.

EDIT: I'm adding information of the life expectancy decrease (LED) and equivalent driving distance (EDD) for opening a bottle of soda. See this post for an introduction to the LED and EDD.

If Americans open roughly 100 soda bottles per year, and if the annual risk of getting an eye injury from opening a soda bottle is less than 1 in 10 billion, the risk of opening each bottle is less than 1 in a trillion. That means that even if we were to assume any serious injury from a soda bottle were fatal, you life expectancy would decrease from opening a soda bottle by only 2.5 milliseconds (80 years - a typical lifespan / 1 trillion). Opening a soda bottle therefore has an LED of 2.5 milliseconds or less.

The EDD is computed by the fact that 14.6 driving fatalities occur every billion miles. The distance you'd have to drive to incur the same risk as opening a soda bottle is therefore 1 billion miles / 14.6 / 1 trillion; the EDD is less than 4.5 inches; so driving more than the length of a pickle is more risky than opening a soda bottle, once again with the ridiculous assumption that all bottle top eye injuries would be fatal.

Mad about BSE

Greetings, fellow nerds.

This will be just a quick post about the relative risks between the "mad" and the "cow" in mad cow disease. In truth, the danger "tainted beef" poses to us is so small that as a consumer, you should forget about mad cow disease entirely: it's a waste of neurons. I'd even feel guilty making you read this post if it weren't for the fact that it exposes the sensationalism behind mad cow disease reporting.

Assessing Mad Cow Lethality

Mad cow disease in cows is called bovine spongiform encephalopathy (BSE), and to date there have been at least 188515 reported cases of it worldwide. Common sense suggests that there are a whole lot of unreported cases too, considering the incentives farmers have to keep things quiet. The disease humans contract by eating infected cows is called variant Creutzfeldt-Jakob disease (vCJD), and there have been a total of 170 confirmed cases worldwide. This number is probably not exaggerated (in fact the false positive rate for vCJD might be rather high), so you might think of 170/188515 (or about 900 per million) as an upper bound on the chances of contracting vCJD from eating an entire mad cow. However, probably not all of the 188515 cows were consumed in their entirety, which means that 900 per million might be a good ballpark figure as to the actual transmission rate from eating a whole cow.

If there are roughly 250 lbs of meat per cow, and if a typical beef meal has a quarter pound of meat, the odds of catching vCJD from a single meal of infected beef are 900 in a billion. When you consider that in the time period the 188515 cows were detected, the UK (the country hardest-hit by BSE) produced about 100 million cows, the risk of getting vCJD from eating one randomly-chosen UK beef meal is about 2 in a billion.

No Consensus among Academics

Why aren't I just reporting what the medical journals say about BSE to vCJD transmission rates? Because these estimates are all over the place. This study in the journal "Risk Analysis" by Eric Grist shows that there's nothing like consensus regarding the risk of a human contracting vCJD from eating an infected meal: published transmission rates vary from 0.9 in a billion to 7 in a thousand (c.f. my estimate of 900 per billion based on case numbers). The "Risk Analysis" article continues on to point out that the 7 in a thousand measure is obviously inconsistent with observed vCJD infection rates. (Thank you, Dr. Grist!) Perhaps even researchers are prone to sensationalism, especially if the said sensationalism might result in extra funding.

New Risk Metrics

We need better units for analyzing risks. It's hard to grok these raw numbers without an everyday context, so I'm going to introduce two new metrics:

1. Life Expectancy Decrease (LED)
   
2. Equivalent Driving Distance (EDD)
   

The LED measures the expectation of the decrease in life expectancy based on taking the risk once, assuming an 80 year lifespan. So for example, the LED from eating a meal with UK beef at the height of the mad cow scare is (80 years * 2 per billion) = 5 seconds. Compare that to the LED associated with the extra calories in your fast food meal: (80 years * 94 per million) = 2.7 days. The extra risk of vCJD is insignificant next to the threat of the extra calories involved with taking a big bite of beef.

Driving cars is a risky activity that most of us have come to terms with. Driving therefore provides an ideal reality check that helps us put new risks in perspective. This DOT report (page 8 of the .pdf) shows that there are about 14.6 vehicular fatalities for every billion miles traveled. The EDD of a new risk is the length of the car trip with the equivalent level of risk. For example, the EDD of the untested UK beef meal is (2 per billion * 1 billion miles / 14.6) = 720 feet; less than one Manhattan city block. Again, if the beef was in a fast food meal, the EDD from the extra calories is over 6400 miles: greater than the radius of the Earth.

Conclusion: Calories Matter More than Prions

If you spent more than 5 seconds worrying about contracting vCJD from beef, even at the height of the mad cow scare in the UK, you've been had. Also, if you think a fast food meal saves time, you should consider the 2.7-day lifespan decrease it brings (unless you're underweight - see my blog entry). It's true that the risk was unknown at the time (so maybe caution was indicated), but I'm getting sick of people worrying about false alarms, especially when there are more pressing issues which aren't getting enough attention.

I'm also disillusioned with the media, although I can see their point. Nobody will buy a paper saying "Get Off Your Butt and Get Healthy," but "New Plague Risk Sweeps the Nation: Will YOU Die?" has more zing.

As new crises come up in the news, I'm going to try to keep up with the LED and EDD metrics for them. With any luck, they'll catch on as popular reality checks for how risky a new terror actually is.

Why Biometrics Scare Me

Greetings, fellow nerds.

I am a lover of technology. I love my Mac. I love the Internet. I love my doubly-shock-absorbing bicycle. I even once had a dream in code. Yet today I'm going to tame my technotropic tendencies to warn you against the threat of widespread biometric identification.

There are few technologies less viscerally appealing to tech nerds than biometrics: imagine a world where machines recognize you for the rich, influential 1337 h4xx0or you are just by scanning your body. Nothing short of tech porn.

In some limited circumstances, biometrics might be appropriate. For instance, if a security guard monitors the process of you putting your finger/retina/receding hairline on a scanner as an extra security layer, that's fine. However, biometrics; when substituting keys, credit cards or passwords; have three serious flaws:

1. Biometrics give thieves an incentive to chop off parts of your body.
2. You give out your biometric data all the time, whether you intend to or not.
3. If you get your biometric identity stolen, you're screwed forever (unless you believe in reincarnation).

Don't Give People an Incentive to Cut You Up

Issue #1 means that not only would I personally refuse to use biometrics, but also that I have an incentive to make nobody use biometrics for identification. I don't want to have my hand chopped off only for thieves only for them to discover I didn't have a fingerprint-enabled bank account like most normal people.

Do you think it's far-fetched for criminals to chop off parts of the body for their biometric payload? It's already happened. Even though biometric identification is rare, we're starting to see the criminal reaction to it. I'd rather give up my cards and keys, thank-you-very-much. I'm horrified to see that the ICICI bank in India is also planning on opening widespread fingerprint-based ATMs for rural farmers who might find carrying cards to be too much of a trouble. I suppose a fingerprint-and-pin solution might somewhat discourage finger-theft, but your average robber might take fingers just in case, the same way a North American mugger wouldn't leave their marks' bank cards behind.

Don't Leave Credit Card Copies Everywhere

Issue #2 is pretty straightforward: getting someone's fingerprint is usually not very hard. Moreover, fooling a scanner with a print lifted from a glass is surprisingly straightforward. Even though expert techniques haven't yet been developed for getting a scanner to accept a print lifted off a glass (at least I'm not familiar with these cloak-and-dagger techniques), some first-try methods have a success rate of 80%. Some scanners can even be fooled by fogging them up by blowing on them to reveal the print of the last person to use them. Unless you'd be OK with leaving copies of your credit card on every smooth surface you touch, you shouldn't use your fingerprints as card substitutes either.

Getting Replacement Fingers and Eyes is Hard

Issue #3 illustrates the importance of disposable layers of security. I've had my credit card info stolen, and it was no big deal. VISA* called me one night to confirm some unusual charges which had gone through my account. When I said I hadn't made these charges, they sent me a replacement card and an affidavit to sign two days later (I guess it's in their best interest to keep me buying), and my old VISA card was sloughed off painlessly. I didn't pay a dime. (My story is not uncommon; identity theft happens to about 9 million Americans a year.)

The point is that fingerprints and retinal patterns are not things you want to have to slough off, ever. I like it that getting a new credit card didn't involve surgery. It's a feature (not a bug) that you can dispose of a credit card if its information gets compromised. Let's not take a step backwards in functionality for the sake of some flashy tech porn.

Conclusions: Now is the Time to Rant

Even though biometrics aren't widespread, the time to rant against their replacing credit cards is now. It's easier to nip a bad technology in the bud than it is to defeat it once it gets serious backing. How are we going to execute the said nip? By talking. That's all. I hope the scenarios I've laid out are sufficiently grizzly to spread through pool halls and cocktail parties; if they spread widely enough we will have done our job.

Take care; go do something amazing with your fingers while you still have them.

*I swear they didn't pay me to write this; I think it's important to get the word out if you feel like a company has done you right.

Death match: Big Macs vs. Unprotected Sex

Greetings, fellow nerds.

My Spanish teacher in Costa Rica (Carlos P. - the P. stands for a word which happens to be the foulest word in the Portuguese language, which was entertaining to the Brazilian immigration officials - that's entirely another story though) asked me why Americans are fanatical about staying AIDS-free, but don't give a pair of dingo's kidneys if they die of being too fat. Carlos, the more I think about it, the more it sounds like you're on to something, and I'm going to follow up your comment with a numerical analysis: today we're going to weigh the risk of HIV contracted from having unprotected sex against the increased risk of dying from obesity by eating one Big Mac™.

HIV risk from unprotected sex: what are the numbers?

First off, let's quantify the HIV risk of having sex with an American chosen at random. The CDC estimates the percentage of HIV-positive US residents to be 0.4% (as of 2003). That's already a low number, but to asses the risk of catching HIV from unprotected sex we have to multiply by the transmission rate: that is, given that you have unprotected sex with somebody who's HIV-positive, what are your chances of getting it?

What is this transmission rate? Take a guess. Now decrease it by a factor of 10. If your guess was like mine, you'd still be way above the truth. I don't know if it's general squeamishness or over-zealous sex ed teachers, but the risk of HIV transmission between otherwise-healthy people is between 5 and 50 cases per 10,000 acts, depending on exactly what kind of (more-than-just-oral) unprotected sex you're having (Wikipedia link + original article). That means if you and your (randomly-selected vis. HIV status) American partner are healthy, you have between a 2 in a million and a 20 in a million chance of contracting AIDS from unprotected sex.

Let's put that into perspective. If you live to be 80, you'll have lived 29 200 days. What are the chances (everything else being equal) that today your number's up? That would be 1 / 29200 = 34 in a million, almost twice the HIV risk associated with receptive anal intercourse from a randomly-chosen American male.

My heart goes out to people who have contracted HIV from unprotected sex. I'm sure they have been demonized for being so careless as to indulge in this (so-called) risky behavior. Let's find out just how risky their behavior really was, in terms of Big Mac™ eating.

What's the Lethal Dosage of Big Macs™?

First of all, I don't want to single out Big Macs™, McDonald's™, or even just the fast food industry as unique bringers of ill-health. The Big Mac™ is however a nearly-ubiquitous unit of culinary over-indulgence; let it here symbolize any overly-calorific meal.

There's a good chance that fast food-related factors other than too many calories cause health problems. Films such as "Super Size Me" suggest that high concentrations of fast food can kill - suppose Morgan Spurlock had spent 100 days on the McDonald's™-food-only diet and found that to be lethal. Then we could estimate the risk of eating a Big Mac™ to be 1 in 300 (for 300 meals). That's a risk of more than 3000 per million meals, or between 150 and 1500 times the risk of contracting HIV from unprotected sex. When spread out over many years, the lethality of Big Macs™ can't be that high, so let's get a low-ball estimate of the risk on Big Mac™ poses by its calories alone.

Weight Gain from a Big Mac™ Meal

Surprisingly, if you eat a Big Mac™ and nothing else as a meal, you get about the right number of calories. Assuming that you should be eating 1800 calories a day, the Big Mac™'s 600-calorie payload doesn't sound so bad. It's the side dishes which add the real risk. Full meals at fast food restaurants can have as many as 1825 calories - 1025 too many for an 1800 calorie-a-day diet. For now, let's assume the typical fast food meal has 800 superfluous calories which will be carried around by the diner essentially forever. (I'm not sure if eating too much has a net positive or negative effect on one's metabolism: if you're heavy you might decide to drive instead of walk so much that it counteracts the need to fuel a bigger body.) That 800 extra calories per fast food meal translates to just under a quarter pound of extra body weight; let's see what that does for your health.

Mortality Increase per Big Mac™

I could give you a laundry list of symptoms you could get by being overweight, but instead I'll just boil it down to a number: how much does your mortality rate increase if you have that extra quarter pound on your paunch? According to this JAMA article, in 2000, 111 909 excess deaths were caused by obesity among the 23.3% of Americans who were obese or extremely obese (defined as having a BMI above 30). In 2000 there were 281,421,906 Americans total, which means that 0.17% of obese people died that year from being obese. That's just for the year though - since HIV can let you live for 15 years or more, the risk of dying from obesity in the same span of time you'd expect as from an HIV infection is 2.5%, or 1 in 40.

The last factor to consider is how likely it is for an extra quarter pound to push you into the danger zone. (Aside: in reality, there probably isn't any sharp divide between safe and risky BMIs, but we can still get a feel for the effect size of being obese by this discretization.) From the same study, 33.8% of Americans have a BMI from 25 to 30. Assuming an even distribution of BMIs in the 25-30 range and an average height of 5'10", about 0.8% of people with a BMI between 25 and 30 would be tipped into the BMI > 30 class from that one extra fast food meal. If we assume the risk of already-obese people is at least as great as the risk to overweight people, that means that for 47.1% of the American population, eating one Big Mac™ has a .8% chance of increasing your mortality risk over the next 15 years by 2.5%. Multiplying probabilities, the total risk of that Big Mac™ killing you within 15 years (again, assuming you're a randomly-chosen American) is at least 94 in a million, or between about 5 and 50 times the HIV risk of unprotected sex! That's an average too; if you're overweight, Big Macs™ are at least twice as deadly.

Caveats

There are a few weak points in my argument; let me list them. Here are some factors which may make HIV more dangerous than I let on.

1. People who have more unprotected sex with multiple partners tend to have partners with higher HIV risk too.
2. Other STDs can increase the rate of transmission of HIV by increasing the volume of fluids exchanged.

Additionally, I didn't factor in that being underweight can be risky too; in other words, Big Macs™ could be a benefit to skinny people.

However, my final analysis also didn't take into account the fact that fast food is nutritionally poor, an additional danger I have not accounted for. Moreover, I only counted the obesity risk over 15 years, while the risk in fact continues for as long as you are obese.

Conclusion: Big Macs™ are More Deadly than Unprotected Sex in America.

It would be incorrect to state that every Big Mac™ consumed poses more risk of death than every act of unprotected sex. It also would be wrong to claim that the HIV/AIDS epidemic has been totally eclipsed by a wave of obesity; factor #1 under Caveats is too big to ignore in an epidemiological context. However, given my reasonable assumptions, I find that on average Big Macs™ are 5 to 50 times more deadly than unprotected sex with a randomly-chosen American. Carlos P., your intuition was right.

Here's the take-home message:

1. HIV is harder to contract than you might think.
2. Too much food can kill you.
3. We should worry more about our diets, and perhaps less about disease.
4. If you're like me, you probably worry too much about the wrong things.
   

To address #4, I've started a wiki to keep track of the risks around us. Help me complete and update it; then maybe we can keep a sense of perspective when it comes to banal topics like Big Macs™ and ominous-sounding plagues like HIV/AIDS.