Part of a much larger story.

Posted by John Peterson Myers at Oct 09, 2008 10:10 PM |

The press release from Elsevier, one of the world's leading scientific publishers, led with "Plastic World findings on bisphenol A, phthalates and flame retardants urge regulatory action" under the title "Six Environmental Research Studies Reveal Critical Health Risks from Plastic."

The two biggest stories generated by the publication both focused on the same one paper, Dr. Shanna Swan's new data on phthalates and development of the male reproductive tract.  Martin Mittelstaedt's coverage in the Globe and Mail (Toronto) was superb, as always (he writes prolifically on environmental health).  In USA Today, Liz Szabo wrote another excellent piece. She, too, regularly writes on these and related issues. Both reporters excel at taking complicated science, finding its essential points, and writing about it effectively and accessibly.  And neither are afraid to take on difficult and charged issues.

Swan's paper extended her research on phthalates in two important ways.  First, in addition to confirming, once again,  that boys exposed to higher phthalate levels have altered genital development, she now finds an association between higher phthalate exposure and reduced penis size.  No wonder her study got attention... Second,  with a larger sample size than before she now finds that the metabolite of DEHP, a very common phthalate used to soften PVC plastic, shows associations.  In the earlier work it did not reach statistical signficance. This was surprising because experiments with laboratory animals predict that DEHP should have an effect.

But "Plastic World" doesn't stop with Swan.  Taken together, the collected papers paint an astounding picture of the unexpected consequences of that long-ago prescient prediction in The Graduate: 'plastics.'  These new results give 'plastics'  a whole new and far less positive meaning:

Charles Moore examines the explosion of plastic pollution in the ocean. For a long time, plastic debris was regarded as nothing more than an aesthetic problem.  But as the volume has grown exponentially over the last 2 decades, and as understanding has deepened about the role of micro-plastic debris in concentrating persistent organic pollutants, as well as on the inherent toxicity of some plastics and plasticizers, this assessment is changing.  There are places in the North Pacific now where plastic fragments outweigh life. Tiny plastic particles are being consumed by zooplankton and filter-feeding whales, entering the food chain. And larger pieces have become a significant part of the diet of birds, turtles and fish.

Jörg Oelhmann leads a critical reassessment of environmental risks posed by plastic and plasticizers in freshwater environments in Europe, emphasizing bisphenol A and endocrine disruption. Because BPA and phthalates are continuously released, they are regularly detected in aquatic environments. While EU risk assessments of the resulting exposures have given them a wash, Oehlmann and his coauthors conclude that this reassurance is not justified by current data.

Paola Palanza heads a review of bisphenol A's effect on brain structure, brain chemistry and behavioral development.  For example, in multiple animal studies, low doses of BPA during pregnancy reduces sex differences in behavior.  This issue went white hot last summer when the National Toxicology Program concluded that they had 'some concern' about BPA's impact on the developing nervous system.

Chris Talsness reviews recent toxicological findings on brominated flame retardants, the PBDEs, whose use has become ubiquitous and whose chemical characteristics are quintessentially persistent and bioaccumulative. Structurally similar to PCBs, they are now known to disrupt thyroid hormone action, raising big worries about their possible impact on development because of the central role that thyroid hormone plays in growth and development. Rodent studies implicate the PBDEs in impacts on neurodevelopment and reproduction.  "Their presence in human breast milk is particularly troubling due to exposure of nursing children."

Kembra Howdeshell and her coauthors summarize research on the 'phthalate syndrome' in rodents:  Exposure in the womb causes decreased testosterone levels during development which then leads to abnormal development of the male reproductive tract, including increased incidence of hypospadias and undescended testes.  Of special relevance to people, because people are exposed to multiple phthalates simultaneously and continuously, is work in Earl Gray's EPA lab on phthalate mixtures and the 'phthalate syndrome.'  The bottom line? The animal studies show that mixtures of phthalates can act in an additive fashion, so that mixtures composed of doses of individual phthalates too low to have an effect by themselves can together cause adverse effects.  This helps understand, perhaps, why Shanna Swan's studies reveal associations between phthalates and changes in reproductive tract development in boys can occur at levels beneath those typically found effective in rodent experiments.

Take home message: There's a lot of new science accumulating on unexpected health risks of plastics and plasticizers, both for organisms (including people) and for large scale ecosystem processes.  These reviews will provide reporters with good entrees into some of the most rapidly moving research fronts in this field. And they also identify for reporters some of the leading scientists in the world who are working on these issues.