I’m afraid we can look forward to a lot more of this kind of nonsense.

Several days ago an article titled “Is Your Shower Curtain Making You Fat?” appeared in the magazine Spry and was then reprinted in the Dodge City Daily Globe.  The article drew readers’ attention to the dangers of endocrine disrupting chemicals (EDCs), giving 5 examples of chemicals used in everyday consumer products (BPA, phthalates, PVC, PFC’s, and PBDFs).

With a quote from a professor of pharmacology and references to a couple of crude, published studies, the author, Catherine Winters, conveyed the message to her readers that they are surrounded by products containing EDCs that can play havoc with hormonal signaling and induce disease.  The shower curtain reference was based on a study that found that shower curtains containing PVC, or polyvinyl chloride, “release up to 108 volatile organic compounds (VOC), some of which could be detected in the air 28 days after the curtain had been hung.”

Nowhere in the article is there any mention of the kind of exposure to the chemicals required to cause the adverse health effects mentioned.  You would think that she is talking about occupational exposure where one is breathing in dust and fumes from these chemicals 40 hours a week, week-in and week-out.  In fact, exposures encountered in daily life are likely to be trivial to non-existent.

English: Plastic bottles in the back of a pickup truck, ready for recycling (Photo credit:... [+] Wikipedia)

I refer to this article not because of the wide reach of these publications but because the story is symptomatic of something that is very widespread, not to say pervasive.  We read and see claims and suggestions of this type, if slightly less obviously silly, in newspapers, including the New York Times, the media more generally, and, even in supposedly peer-reviewed scientific journals.

So this is really a general, society-wide phenomenon.  In part, the media and the public are encouraged to believe these unfounded scares by poor studies that get published in journals, because scientists and institutions that should know better give them currency.  The media can then be depended on to pick up the titillating results of these sloppy studies.

If, in fact, as I wrote last week, we are far from understanding the causes of the obesity epidemic, we can be sure that in the coming years a great deal of attention will be focused by researchers on possible factors that have received less attention but that MAY play a role in the increase in obesity over the past 3 decades.

A hint of a new tidal wave of research that will undoubtedly generate countless new linkages between  various exposures and a multitude of health effects is contained in a 2009 paper entitled “Ten Putative Contributors to the Obesity Epidemic.”  The paper has 22 authors and is 79 pages long.  The lead authors are from the Pennington Biomedical Research Center at LSU and the University of Alabama at Birmingham.

Along the same lines as I discussed last week, the authors start out by calling into question the usual explanations of the obesity epidemic.  They write that, “Marketing practices of energy-dense foods and institutionally-driven declines in physical activity are the alleged perpetrators for the epidemic, despite a lack of solid evidence to demonstrate their causal role.”  They refer to these widely cited factors as the “Big Two.”

While allowing that the Big Two – excessive intake of calorie-dense foods and lack of physical activity – play a role, the authors make the case that other factors, which have received little  attention, may contribute to weight gain.  For each of the 10 “putative” factors, they summarize the different types of evidence (experimental, ecologic, epidemiologic, etc.) and discuss how each factor might contribute to the problem.

This certainly represents an ambitious research program.  Some of the items represent more focused hypotheses that could be tested (assortative mating; sleep deficit; increasing maternal age), whereas others represent whole new disciplines (i.e., the microbiome; endocrine disruptors).

These factors may well merit study in relation to obesity, but it should be pointed out that, at present, the evidence for some of them is very slight.

To the extent that these questions are well-formulated and high-quality studies are carried out to address them, this proposed program is a positive development and is likely to produce new and useful knowledge.

However, while the authors do a credible job of laying out the scientific evidence for their 10 factors, there is a disturbing lack of critical perspective on some of the data they present.  For example, in their discussion of endocrine disruptors they refer to the fact that most of the population has measurable levels of these chemicals in their blood and urine, but they do not question whether these trace amounts are likely to have any biological effect.  They also refer to an association of levels of phthalate breakdown products in urine with abdominal obesity in the NHANES, without any qualification regarding the uninterpretability of such an association in a cross-sectional study (i.e., where are the data have been collected at one point in time).

It is fine to study these things, and, if done right, we are likely to gain new and important knowledge.  But the results are unlikely to bear out simplistic ideas.  They are more likely to turn our attention to things that we didn’t suspect heretofore.

We should understand that there can be contributing factors that may play a subtle role and modifying factors that may increase the risk of obesity for a particular subgroup that has other risk factors.  But these things are going to be difficult to study and to definitively tease apart.

The problem is that when an issue is the focus of so much attention – from the media, from health officials, the medical community, and marketers of all sorts – science does not proceed quietly out of the public eye to uncover new and useful knowledge.  What is expected is immediate delivery of findings that will make a difference.  And these will be seized on by some scientists and by willing journalists to churn out more nonsense like the Dodge City Daily Globe article.

Geoffrey Kabat is a cancer epidemiologist at the Albert Einstein College of Medicine and a contributing editor at STATS (Statistical Assessment Service) at George Mason University.   He is the author of Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology.