My Life as a Guinea Pig

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The problems with casting so wide a net are manifold. For one, Duncan starts to sound like your great-aunt enumerating her real and imagined ailments at Thanksgiving. The state of his earwax (wet) is neither interesting nor elucidating. All this chatter dilutes his critical argument that chemicals really do mess with our genes. Moreover, Duncan is occasionally sloppy. He says he does not have a genetic mutation that would make him vulnerable to mercury toxicity, but reverses himself in an article based on the book in Discover magazine. He calls variants of flame-retardant molecules "cogeners" instead of congeners. At one point he says he has a DNA marker on the DRD4 gene that may lead to risk-taking behavior, but later refers to it as his DRD3 gene.

I imagine that Duncan ran into the classic challenge that comes with writing about human environmental health: the lack of conclusive information. It's easier and more fun to write about medical gadgets and promising pills. But to his credit, before he switches gears he explains the conundrum well. Data on the human health impact of chemical exposures are sparse; there is far more information on lab animals in controlled experiments. And scientists know very little about which genes may help us or hurt us when we're exposed to potential toxins, how these genes interact or override one another, or how toxins actually change gene expression. In fact, much of the new personal genetic testing is about as accurate and useful as palm reading. As Fintan Steele, a geneticist with the Broad Institute of MIT and Harvard, has put it, recreational genetics is just another form of navel-gazing, neither interesting nor particularly rigorous.

Duncan begins to concede as much. When he tests his DNA at several start-up companies, including 23andMe and deCODEme, he receives contradictory information about his heart-attack risk. One service evaluates a mutation and "scores" him as having a 64 percent higher risk than other people. Another service notices a different mutation and estimates a lower risk. And although he has a gene that supposedly encodes for risk-taking, he proved risk-averse in the gambling tests.

Experimental Man doesn't quite fulfill its potential. Duncan leaves much unsaid about environmental health, and he misses a major opportunity in not exploring endocrine disruption, either as a theory or in the reality of his own body. Given that he tests nearly every part of his body, why neglect his hormone levels, which are known to be affected by chemicals in the environment and are critical for everything from metabolism to fertility?

So here's a friendly challenge to the Experimental Man, whose worthy project continues in an interactive Web site funded by the Center for Life Science Policy at the University of California, Berkeley: go test your sperm count, your testosterone levels, and the functioning of your adrenal system. Then talk to experts about how phthalate exposure has affected scientific measures of masculinity, like belly fat in grown men and even -- prepare yourself -- the distance between anus and genitals. Now that would be a brave and revealing metric for Duncan's  Experimental Man to add to his list.