July 30th, 2008

rock shadow

PCBs, girls, and vegetarianism

As some of you know, my mom's side of the family has consisted of quite a few more girl babies than boys for several generations back now. My sister and cousins have all had girls (five daughters between my sister and four cousins). My mom and aunts all had girls (six of us). My grandmother had five girls, and though I don't have the records, I've been told that her twelve siblings had several times more girls than boys. In her generation, there were five girls before the first boy, and in my grandpa's family, there were also a number of girls born before the first son (which I think was him, the youngest).

I've always figured my family was just a statistical anomaly. My sister has looked into various chemistry or dietary reasons for this (wanting to have a boy next), but the research I've seen on this has generally been pretty sketchy and incomplete, so I've decided to chalk it up to chance -- at least, until I see compelling evidence otherwise.

Well, I read an interesting article today that seems to indicate that there are some chemicals out there that do noticeably tip the scales. I've long known that the benzene and other chemicals in sunscreens mimic estrogen, shifting the sex of fish toward the "default" female, even during an individual fish's life, and having similar effects in rats and other animals. I have blogged about the cosmetics safety database listing the safety of sunscreens. (It looks like the famous "wear sunscreen" column, in which the author said the only sure advice she could give was to wear sunscreen, might have been wrong after all.) I had also heard that PCBs, common in flame retardants and coolants, and other chemicals had documented effects on development, especially sexual development. But this is the first I've heard of the chemicals actually causing a shift in sex ratios at birth.

According to the article, the Arctic populations that the Arctic Monitoring and Assessment Program studied had imbalances that were particularly pronounced (twice as many girls as boys, where before the ratio was 1.1 boys for every girl) because of their reliance on marine meat, which is high on the food chain and thus had heavy concentrations of these chemicals.

Though it's doubtful that anything like this has caused the generations-long surplus of girls in my family, it does make me reconsider my "just-chance" stance on the trend. It also places even more importance on one of my main reasons for being vegetarian for 9 or so years through my youth and into college. Collapse )