Many of you may not remember how much fuss there was about a strange affliction that veterans of the first Gulf War reported soon after they returned from the Middle East. But in the early 1990s it was big news: Gulf War Syndrome. The synmptoms were of the sort it would be easy to dismiss because they aren't "threshhold" types of things where a person knows something is wrong. Instead they are vague and could conceivably be assigned to all sorts of causes: stress, PTSD, depression, etc.. Now--about what, 18 years later?--we have a report that suggests the syndrome is real and that the cause could perhaps be one of two things: pesticide exposure or exposure to substances used to protect against nerve gases.
As is usually the case the news didn't get super-specific about the names of things. So I checked Wikipedia to see what's there and was delighted to see they've got a nice description of the report contents on the site. To see it just search Gulf War Syndrome.
The pesticides were probably used to protect our soldiers from communicable diseases or simple irritation associated with insects, including sand flies. They were likely organophosphates or carbamates. These substances are acetylcholine esterase inhibitors. Aceetylcholine is a neurotransmitter that is removed from the synapse by acetylcholine esterase. The inhibitors block the enzyme, causing a buildup of acetylcholine in the synapse and altered nerve function. Hence the insects get screwed up and croak. Hence, perhaps with lots of exposure, people get symptoms related to nerve function. Such a syndrome is described for farm workers who get accidental poisoning, although symptoms of massive exposure don't sound quite the same as those described for the Gulf War Syndrome.
The other possible source of the problem are agents used to protect against nerve gases that could have been used as chemical warfare. These agents include Soman (mentioned in the Wikipedia article) and also more familiar agents like Sarin and VX....which we have manufactured in the U.S. and which are now being destroyed at places like the Umatilla Chemical Depot in Umatilla. Just like the pesticides, these substances are all acetylcholine esterase inhibitors. They act via a very similar biochemical mechanism.
Interestingly, the protection against such agents that may be implicated in the Syndrome is again an acetylcholine esterase inhibitor. It is called pyridostigmine. I'm not sure how it works but my guess is that it competes for binding to the acetylcholine esterase but does so reversibly, so it can block the nerve agent without causing severe or long-term effects. .....or maybe it does. ....maybe in combination with exposure to other acetylcholine esterase inhibitors.
Check out the structures for pyridostigmine and for the pesticide sevin on Wikipedia. See the similarity?
It's a fascinating and sad story that continues to unfold.
3 comments:
Listening to OPB this morning and there was an article about the Oregon board of fisheries wanting to ban three different pesticides because they interfere with salmon's olfactory sense and therefore limited their ability to return to spawn.
They mention on the side the effects on people, but it seemed an aside to the salmon issue.
It made me think of Gulf War Syndrome in the sense that our bodies are completely run by chemical reactions, and we are creating chemicals to do a variety of things. It appears to me that little time is spent when developing chemicals looking at how they might mimic or mask the chemicals that we manufacture within ourselves.
I tend to agree. We have the FDA to help us understand and regulate food and drugs, but when it comes to other exposures there is less regulatory oversight. Although I'm sure the producers of commodity and agricultural chemicals are concerned about health and the environment. And there are MSDSs for lots of things we interact with, for instance, in the lab. But life is rich and complex and we don't really understand the details all that well.
So maybe we shouldn't be completely surprised by things like the npr story about salmon and pesticides.
I am interested in seeing the line drawings of these compounds. Like with the melamine on the chalkboard, it makes sense to look at how similar the different compounds are, how they might mimic each other. And that of course opens the door to all manner of questions as to what they do after that.
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