Increasingly, environmental journalism is taking on the color of naivity. Take this entry in Plenty Magazine’s “Your Daily Green Bit,” written by Jessica A. Knoblauch, which focuses on the risks of phthalates in vinyl window shades:
the relatively low cost of vinyl shades doesn’t outweigh the potential health affects of surrounding yourself with chemical-laden sun screens. Besides, surviving the school year is hard enough without worrying your window coverings are making you fat.”
Let’s start with the obvious mistake: the research pointed to in the link is about Bisphenol A (BPA) and Perfluorooctanoic Acid (PFOA) and rodent studies; there is no mention of phthalates. Second, there is no scientific justification for thinking that sleeping in a room with a vinyl shade will make you fat based on these or other studies.
There is at least one study which showed that several phthalate metabolites had “statistically significant positive correlations with abdominal obesity and insulin resistance in adult U.S. males,” which means that the fatter and more insulin resistant the man, the greater the quantity of phthalate metabolites in his urine.
But the simple fact of a correlation doesn’t mean that phthalates caused the obesity. It could be the case that men who are fat retain more phthalates than men who are not; in fact, the authors of the study listed seven limitations on the interpretation of their findings, among which include the study being cross-sectional, so it is only a snapshot of at a single point in time and cannot determine causality; and the database they used contained no data on sex hormone levels, thereby limiting examination of the mode of action by which they hypothesize that phthalates might cause obesity. (This, naturally, didn’t stop journalists from touting a connection).
In order for any chemical to be implicated as a factor in obesity, there has to be a route of exposure. So there would have to be some way of getting the chemicals out of the blinds and into the bloodstream for anything to take place. The studies cited by Knoblauch involved administering the chemical to pregnant rodents – and then seeing what the effect is in their offspring.
The article doesn’t say whether this was done by feeding (oral exposure) or in utero (by injection), but as BPA loses all estrogenic capacity in humans after oral exposure, the test involving BPA would have to have been by injection. So, even if you spend hours licking a vinyl blind or sniffing vinyl blinds in direct sunlight, whatever BPA you might absorb (and where is the evidence that BPA offgases in sunlight?) is not going to disrupt your endocrine system, make you fat, or reveal anything other than the likelihood that you need psychological help.
Moreover, the study cited on BPA used mice. The European Union’s risk assessment specifically noted that mice process BPA in a way that is so different from humans these kinds of studies have no relevance to human health. As for PFOA, studies of workers and other populations exposed to high levels of PFOA have not found any connection between exposure to the chemical and obesity.
The one thing this article does manage to demonstrate is that Plenty’s “Your Daily Green Bit” should be taken with a heaped serving of skepticism.