Thursday, August 06, 2015

PVC-induced Acroosteolysis?

I look forward to my inbox on Thursdays because in it will be the links to The New England Journal of Medicine's "Images in Clinical Medicine". These are open access images that doctors from around the world have submitted that show something that is visually unusual in a patient that they examined and possibly treated. The images can be photographs, MRI's, x-rays, etc. and have a brief discussion about the condition, treatment and outcome.

This week, PVC was considered (but ruled out) as inducing the fingertip bones in this man's hands to be absorbed by his body:

The condition is called acroosteolysis [1]. PVC gets blamed for lots of things, but I thought it was odd that it, the polymer itself, would get the blame. A more likely cause would be the monomer (vinyl chloride, VCM), the catalyst or any of the various additives that are added to PVC (and there are A LOT of additives added to PVC). I dug a little further and that is where it gets interesting. I found a link to an Italian-language report on acroosteolysis in people that used to manually clean the tanks used to polymerize PVC.

"The disease was observed for the first time in mid-1963 in Belgium (Jemeppe) in a chemical plant operated by Solvay, and affected two workers whose job was the manual cleaning of vessels used for the polymerization of vinyl chloride; similar cases occurred in almost all PVC production plants all over the world, but not in the plants where the main activity was the production of vinyl chloride monomer (VCM). Little more than one hundred cases are described in the scientific literature, and this number increases by a few dozen if we consider known but unpublished cases. These figures confirm the rarity of the disease, which peaked at the end of the 1960's and disappeared during the 1970's, probably due to the complete elimination of manual reactor cleaning. Observation of the disease lasted no more than fifteen years and the disease was not replicated in experimental conditions on animals.

The disease was clinically characterized, had a short latency (from several months to several years), was rare and unequivocally linked to the manual cleaning of PVC polymerization tanks. However many questions still remain open: the period when the disease first appeared (many years after the start of PVC production in the world), the etiology of the disease (the most accredited hypothesis considers three concomitant factors: a chemical factor--one of the many substances used during polymerization, and particularly vinyl chloride monomer, a physical factor--microtraumas of the fingers during manual cleaning, individual susceptibility), the pathogenetic mechanism (in particular: the role of skin, respiratory, or digestive system, as entrance door), a method (or test) to screen subjects potentially predisposed to the disease. In our view acroosteolysis of manual tank cleaners in PVC production is an occupational disease which is distinct from "vinyl chloride disease" as identified by Viola (1974)."

That's a puzzler alright. PVC was first produced commercially back in the 1920's and yet this condition didn't appear until the 60's. So what changed? And what is there that the workers would have been exposed to that would have led to acroosteolysis, such a very rare and unusual condition? Despite what the doctors stated, I doubt that it is the PVC itself as workers that process PVC in all it forms don't seem to suffer this way. Most of the additives to the PVC would be added in a post-polymerization operation (having all those compounds around during the polymerization would be a nightmare). So what was the cause?

Given that the condition amongst workers has extinguished itself, I doubt that we will ever know what the cause was.

[1] If I am parsing this word correctly, acro- refers to the extremity, osteo- refers to bone and -lysis refers to the breaking down. Acroosteolysis - a good name.

[2] That second to last sentence needs some help, but it's beyond me as to how to rewrite it correctly, so I left it as it was originally written.

Previous Years

August 6, 2014 - So you want to develop sustainable polymers, do you?

August 6, 2013 - Where There's Smoke, There's Bad Smells

August 6, 2012 - The Secrets of Oobleck Revealed - Partially

August 6, 2010 - Backlash on BPA - Infertility Report


Anonymous said...

It's a poorly written abstract. There are some issues with other parts of the abstract as well (e.g. "little more than..." instead of "fewer"; "1960's" for 1960s).

My favored approach, faced with something like this, is to break down any overly long sentences and thereby reduce their complexity. I also like to enhance parallelism where possible (and here it was difficult, hopefully the solution is not too tortured). I think the main problem here is that the information on hypothetical etiology really needs its own paragraph, but as constructed, individual susceptibility is also meant to lead in to the discussion on the pathogenetic mechanism.

So here's a solution:

However, many questions still remain unanswered. There is a discrepancy between the onset of PVC production and the first appearance of the disease that remains unaccounted for. The etiology of the disease is still controversial, with the most widely accredited etiological hypothesis considering three concomitant factors: substances employed in polymerization, especially vinyl chloride monomer, constitute a chemical factor; microtraumas of the fingers suffered in manual cleaning constitute a physical factor; and individual susceptibility constitutes a limiting factor. The pathogenetic mechanism is still unknown, with possible entry-point roles of skin, respiratory and digestive systems under consideration. An effective test for potential genetic predisposition to the disease has yet to be developed.

Anonymous said...

The abstract it's not poorly written, it's poorly translated. The original article is in Italian and I'm a native Italian speaker.