What this suggests, it’s clearly not certain yet, but it’s a huge signal saying we should be looking at the possibility that these phthalate are ratcheting up the sensitivity of the immune system in background, which then creates this hyper reactivity to triggers for asthma, and maybe a very significant factor contributing to the asthma epidemic.  I find it interesting because there’s a molecular basis for it that makes sense.  There’s now Epidemiological data that are consistent with it and I think it’s a huge signal that scientists working in this field should be paying attention to.  At the same time I think it’s a signal that tells me people should be cautious about their use of materials that contain phthalate.

One of the great mysteries of public health today is asthma. Why? Asthma is now, in the United States it’s one of the single, it is the single biggest cause of kids going into hospitals today.  It’s one of the leading causes of childhood death today.  Asthma is a major problem and it’s come upon us suddenly over the last two decades.  Think back 20 years ago and look at the data.  Asthma was no where near as prevalent then as it is today.  The question is why?  What’s going on?  The people who study asthma have some good ideas about asthma triggers.  Is it in the environment that provokes an asthma attack?  But that’s a different question from why is the immune system of that kid hypersensitized to the triggers?  The triggers have been around forever.  There aren’t more cockroaches today then there were 50 years ago, there may be fewer.  There aren’t dramatically more.  There aren’t as many more cockroaches or other triggers like that.  In fact in a lot of places the air itself is cleaner than it was 20 years ago.  Yet this respiratory problem is dramatically worse.  Scientists have separated the study of asthma into two different types of issues.  Triggers, how the triggers work.  How do we help kids avoid the triggers and manage the disease?  And the other area of research is well what’s causing the hypersensitization initially?  Why is that immune system so reactive now when it didn’t use to be?  We don’t have the answers.  We do have some clues.  There’s some fascinating work that’s been done looking at how kids growing up in areas where there’s a lot of diesel appear to be more at risk to developing asthma over time, particularly if they spend a lot of times outdoors in those circumstances.  But for me one of the most intriguing studies that’s come out, a piece that was published last summer, in the summer of 2004, where a group of Swedish Epidemalogists studied kids in Sweden and looked at risk factors for asthma, asthma itself, not the triggers but asthma itself and discovered that kids that had relatively high levels of a plastic compound called phthalate, they were at much greater risk to developing asthma than the kids who didn’t.  Now this material, phthalate are big group of chemicals and this was one type of phthalate called Diethylhexyl phthalate, DEHP, it’s used in vinyl tiles and other things like that to alter the characteristics of vinyl, of polyvinylchloride.  And in vinyl tiles, as people walk across it over years it creates dust.  So the dust in rooms that have vinyl tiles have phthalate in the dust.  And this science finding showed that the presence of phthalate in the dust of kids in their bedrooms as they’re growing up predisposes them to asthma. 

Well I was fascinated by that result because it turns out there’d been some speculation previously that if you look at the molecular structure of phthalate, this particular phthalate, and especially what it becomes when it gets inside your body and enzymes chew it up and change it chemically into what it’s called a metabolite.  That metabolite is very similar in structure to a key signaling system in our bodies that controls the sensitivity to the immune system.  This study was really interesting to me because it reminded me of a study that had been published almost seven years prior.  It proposed that the molecular structure of what that phthalate becomes when it gets inside your body and is chewed up by enzymes, it becomes a metabolite, which is a minor variation on the phthalate.  What that metabolite looks like when you look at the actual structure of the molecule, it looks very similar to a natural signal that our body uses to adjust the sensitivity of the respiratory tract immune system.  And so what this suggests, it’s clearly not certain yet, but it’s a huge signal saying we should be looking at the possibility that these phthalate are ratcheting up the sensitivity of the immune system in background, which then creates this hyper reactivity to triggers for asthma, and maybe a very significant factor contributing to the asthma epidemic.  I find it interesting because there’s a molecular basis for it that makes sense.  There’s now Epidemiological data that are consistent with it and I think it’s a huge signal that scientists working in this field should be paying attention to.  At the same time I think it’s a signal that tells me people should be cautious about their use of materials that contain phthalate.