Monday, February 09, 2009

CPSIA By The Numbers, Part 3: Scary Sounding Chemicals

This is part 3 in a n-part series called "CPSIA By The Numbers". Part 1 is here. Part 2 is here. This series is also being cross-posted to Endangered Whimsy. Today's installment is more of a science post than a math post, I'm afraid; the next one will have more numbers, I promise. I went off on a bit of a tangent and it seemed better as its own post than when I tried to integrate it into the next batch of numbers.


Boy, it sure seems like it's a dangerous world out there for our kids. Why, any number of dangers lurk all over the house, just waiting for the chance to grab our innocent children by the ankles and make them DIE. Right? Right???

And yet, we find that unprecedented proportions of children somehow make it to adulthood unscathed. How is that possible when we hear on the news about the incontrovertible scientific proof of the latest boogeyman coming after our kids?

One thing that I've noticed about human beings is our tendency to completely misjudge risk when we aren't actively thinking about it. We'll strap our child onto a wheeled hulk of metal and machinery and hurtle 80 miles an hour down the road to go buy organic produce for her to eat. We'll drink diet soda with our super-sized double-bacon-and-heart-attack cheeseburger. We'll use the potty, reach for the sink knob, turn on the sink and wash our hands with the latest antibacterial soap, and then with our newly clean hands touch the exact same knob to turn the sink off. People have a natural affinity for straining at a gnat while swallowing a camel whole. It's part of being human, and it's why turning to numbers to quantify risk is always a fascinating exercise.

Here's how the exercise typically goes: scientists will do a study, only to have a science reporter (usually defined as a person who got better grades in English classes than in Science classes) misreport their results. Science asks good questions, but a lot of the time, scientific research results in the answer, "We just don't know." "Scientists Did Study, Still Don't Know Squat" is not a very sensational headline, though, so it usually gets jazzed up a bit, into something like "Scientists Study Potentially Deadly Toxin," with the story going on to suggest that they just haven't found anything bad about it... yet. Misunderstandings like these are why so many people believe in "toxins"-- while "toxin" is a broad term for anything that can be poisonous, it is more often used as a sort of modern-day version of "demon". Toxins: they're in everything around you-- and only righteous actions can fend them off!


So how can we know if something is actually bad for us?

First, we can start by ignoring rhetoric. Take it from someone who teaches people how to do it: you can "spin" the facts to make the most innocuous things sound bad. Watch as Penn and Teller get people to sign a petition against water, merely by calling it by the scarier-sounding name "dihydrogen monoxide" and giving some highly spun facts about it, such as that it's in every river, stream, lake, and ocean, and that hundreds of people a year die from accidental inhalation of it. You can read more horrible-sounding dihydrogen monoxide facts here. You may notice how similar they are to the scary rhetoric about phthalates.

Second, we can start by understanding the limitations of science. An experiment is set up with two hypotheses, or possible explanations. The "default" explanation, that random chance caused the thing you're investigating (English translation: "stuff happens") is called the null hypothesis and the thing you're trying to prove is called the alternative hypothesis. You either prove or fail to prove your alternative hypothesis with statistical certainty; you can't disprove it. Failure to prove is different from disproof in that failure to prove tells us nothing, while disproof tells is the hypothesis is false. So suppose we set up an experiment where the null hypothesis is that random chance is responsible for a reproductive defect (such as the epidemic of missing testicles among male members of Congress) and the alternative hypothesis is that phthalates are responsible for this defect. This experiment will either prove phthalates are responsible, or will tell us nothing. It cannot exonerate phthalates. That is why you will not find a single study showing that phthalates do not cause harm. However, if you see several studies with similar hypotheses, and none of them shows phthalates causing harm, it's pretty safe to conclude that phthalates don't.

One other limitation of scientific studies has to do with the sample that is studied. I could study a sample of children, for example, and conclude that 50% of all children in the U.S. have Asperger's Syndrome and the other half have food allergies, but I'd be soooo wrong because (a) my "sample" consisted entirely of my own kids and (b) there were only four of them. As a general rule, samples are more effective the larger they are and the more randomly selected they are. So when you see a study, look carefully at the sample size and the way it was selected. True random sampling isn't done due to consent issues, but think about who would volunteer for a study, and draw your own conclusions. When I was in college they used to advertise in the student paper for volunteers for various studies; they'd pay us $10 to push buttons with wires stuck to our heads for an hour. What college student would turn down an easy $10... and what professional wouldn't? If you didn't suspect you had a problem, or you didn't need the money, would you volunteer for a study?

Third, we can weigh scientific evidence and news rhetoric along with what we see with our own eyes. Headlines are constantly trumpeting new dangers to kids, but look around you. Are kids safer and healthier than they used to be? If 90% of carseats are indeed improperly installed, as is so often cited, how come kids seem to be safer in car accidents than they were back when carseats were easier to install? If phthalates cause reproductive harm to boys, and they've been around since the 1930's, and they're in everyone's bodies and all our rivers, how come the vast majority of men seem to have, ahem, no problem using their reproductive systems? Don't be afraid to ask those kinds of questions; give in to your inner scientist!

Observe your own world. When you hear that babies who get all lotioned up have elevated levels of phthalates, don't jump to "OhMyDeityOfChoice, GET THE LOTION OFF MY CHILD!!!!" And definitely don't jump to "I'll just switch to Super Eco-Organic Lotion because it's made with all natural ingredients, and it says 'Toxin Free' on the label!" Think instead, "Gee, all my brothers and sisters got lotioned up as babies, and judging by their own kids, looks like their reproductive systems did just fine. How bad are these phthalate things anyway?"

Finally, we must weigh the costs against the benefits. Phthalate exposure in utero has been shown to reduce anogenital distance in males (that's how far of a hike it is between the "waste disposal plant" and the "recreation area"), but phthalates are found in medical devices that save the lives of expectant mothers and their babies. Think it'd be worth losing those lives to try to make the average boy's perineum longer? Lead in bicycle tire valve stems makes them easier to machine. If a child's bike is taken away from him, he loses an opportunity for fun, safe exercise and for learning responsibility. Is losing the minuscule chance that your child might get lead poisoning on the off-chance he decides to eat his bike tire worth the consequent obesity and dependency that will be fostered in your child? Are you willing to pick weevils out of your flour bin and tend your friend who's ill with malaria in order to eliminate pesticides and preserve wetlands?

Imagine what a wonderful world it would be if all the evil "toxins" were exorcised... but afterward ask yourself, "And then what?" What would we be forced to sacrifice to achieve such millennial perfection? Anyone who answers that nothing would have to be sacrificed is selling something. It is an unbending law of the universe that there ain't no such thing as a free lunch.