Monday, February 28, 2005

Perchlorates as Medicine?

Back in the 1950's, perchlorate was approved by the FDA as a treatment for hyperthyroidism. It appears that the dose is sometimes more than a gram a day. There does seem to be some worry about causing goiter in unborn children, whose thyroid glands are more susceptible to perchorate.

As I mentioned in the post for methylmercury, the dose makes the poison. It appears (from the review by Wolff linked above) that perchlorate passes quickly through the body, unchanged. This suggests that low levels in water would not be a problem for adults, because the dose is low, and the perchlorate isn't retained (except, perhaps, in breast milk as noted below). The toxicity reported in Wolff's review for adults comes only at high, prolonged doses and the harm caused to children in utero (caused by perchlorate crossing the placenta, after the mother ingested a gram of the stuff) is based on pretty high doses, certainly more than from drinking water containing perchlorate in the 50-100 parts per billion range. So I think it is likely that adults are not directly threatened by perchlorates in the environment (nor did the reports in the news suggest that there is any threat to adults. I'm just walking myself throught this, confirming that I come to the same conclusions). The original article that I linked about perchlorates suggests that breastfed infants would get too much, based on the levels in human breast milk. If the ion doesn't concentrate in the body, then the perchlorates in the water couldn't be the only source in breast milk. (I reach a conclusion from the article. I'm both fact-checking the article, and making sure I understand the issues involved.) So, where's the rest coming from? Irrigation water? Natural sources? Is it possible that perchlorate does get stored in some people? More to find out...

Sunday, February 27, 2005

New books

I recently downloaded a copy of Daniel J. Jacob's Introduction to Atmospheric Chemistry from his website. I intend to learn more about environmental science because I think that environmental debates are very important. Currently, I am far from convinced that the sky is falling. I am generally skeptical of the climatologists' ability to forecast future temperatures, but I agree that if global warming is occurring, and whether the cause is mankind, then we have a lot of work to do. Not necessarily to stop or reverse it (even supporters of Kyoto acknowledge that it alone could do little to change things, even if it is correct in its assumptions, while already being fantastically expensive) but to figure out how to live with it.

All this said, I admit readily that I am not an environmental scientist, and I have a lot to learn to fairly evaluate either side of global warming/environmentalism arguments. If I can make some sense of the pdf of Jacob's book, I'll pay the sixty bucks to get the hardcover from Amazon.

I also just received Classical Dynamics: a contemporary approach by Jose and Saletan. Nothing that's politically explosive here, like global warming, yet surprisingly, this area of physics has been influential in popular culture in the past couple of decades. Classical Dynamics, more often called Classical Mechanics, is a foundational subject in physics, and it deals with the motions of average-sized things. It's called classical to distinguish it from quantum mechanics, an altogether different kettle of fish concerned with very small things.

I had a course in mechanics when I was a physics undergrad, and have followed the emergence of new science from this oldest of physical theories since the 1980's. Chaos, fractals and complexity, which is where mechanics has begun to make a cultural impact, have emerged fairly recently. I was also a mathematics minor in college, so the inclusion in this volume of more modern mathematical techniques makes me excited to slog through it. Even when it's interesting, I find theoretical physics a hard row to hoe. Perhaps impatience is the best explanation for why I became a chemist rather than a physicist...

Glaciers and Volcanos on Mars

The European Space Agency has some great pictures of the North Pole of Mars, taken by the Mars Express probe. It appears that there may be some active volcanos on Mars.

I am philosophically supportive of manned space exploration, but this sort of result, like those of NASA's Mars Exploration Program rovers Spirit and Opportunity, makes the case for doing as much as possible by robots before risking the lives of humans.

Then, there's the spectacular success of the Cassini-Huygens mission to Titan, a place we are not likely to ever send people.

There are people of all political stripes that think that this sort of thing is a waste of money. I disagree, and would argue that it stretches both our technical abilities and our conceptions of ourselves to explore in this way. If I have a complaint, it's that these results, and what they imply, aren't getting more media attention.

Friday, February 25, 2005

Benefits have costs...

At TechCentralStation, Sandy Szwarc has an article on methylmercury in fish. Methylmercury is very toxic- but as with any toxin, the dose determines the effect. Szwarc points out that proposed emission standards might reduce methylmercury levels in seafood by as little as one-tenth of a part per billion.

There is some reason to question whether current levels of methylmercury in fish are dangerous to people or children in utero (for examples, follow the links in Szwarc's article). I'm willing to grant that if my wife were pregnant, I would suggest she eat fish that has the lowest levels of methylmercury. In the presence of perfectly good alternatives, chosing lower methylmercury fish is pretty much cost free.

However, if it is true that enacting new expensive mercury emission standards will reduce methylmercury in fish (and elsewhere in the environment) by so little, then the expected benefits don't justify the costs. Emotionally it can seem that any reduction is a good thing. But paying for something one place means that there isn't money for something else, so we should be circumspect about paying too much for too little benefit.

Thursday, February 24, 2005

Perchlorates in Breast Milk

In the past few days, there have been a few stories about "Rocket Fuel in Breast Milk", a melodramatic reference to measured levels of perchlorates in human and cow's milk. Perchlorates are used in rocket fuel, fireworks, and explosives. They occur naturally, and are also made commercially. There are industrial sites where there is significant perchlorate contamination. This raises an obvious question: Did the perchlorate in breast milk come from rocket fuel contamination (or from any other industrial process)? And is it something to worry about?

Perchlorate Chemistry

Perchlorate is made up of a chlorine atom surrounded by 4 oxygen atoms- a tetrahedral structure- and it is properly called an ion, since it has a net charge (of -1, in this case), though it's just called perchlorate in the news. It is very reactive because in it, chlorine is highly deprived of electrons. Perchlorate will wrench the electrons from other compounds to satisfy this deficit, causing strong and often abrupt chemical changes. Organic chemists that I know tend to be wary of perchlorate salts, because they can detonate (hence their uses in explosives). However, the amount and form of perchlorate found in water supplies isn't a detonation hazard. It is a hazard to health because it interferes with iodide use in the thyroid gland.

Perchlorate in the Environment

There appears to be a lot of contamination near chemical plants that used perchlorates. The contamination dilutes quickly as one gets farther from the source. The contaminant is essentially diluted to zero when measured perchlorate falls to the naturally occurring level.

In some cases, at least, the natural backround level is not well known and has only recently been measured- an interesting example is in Texas- and found to be surprisingly high in an area where there is no obvious anthropogenic source (up to 20 parts per billion) . Researchers at Texas Tech have found that both lightning and ultraviolet radiation can generate perchlorates from sodium chloride, i.e. table salt. This makes conclusions about what is background and what is contamination harder, but perhaps not impossible.

Environmental Chemistry is not my forte, but this is interesting enough to spend some time researching, and I will post what I find. At this stage, I am ignorant of what is known about perchlorates and their natural distribution in the environment, to say nothing of what sort of health effects can be expected at a given exposure level. I have a lot to find out. Sounds like fun.

Wednesday, February 23, 2005

Howdy, y'all.

I would have liked my maiden post to has some great scientific or social import, but the best I can do is the blog equivalent of "Hello, World!" , which programmer types will recall as the output of the first program that introduced them to programming in the C language. "Howdy, y'all" is a reflection of my western Kentucky roots, and also reflects my delight at people being surprised to meet a scientist with a southern accent.

Assuming I can find time to keep the site updated, I plan to focus on science with some reference to economics and politics, at least when the intersection of these is interesting.

Doing science requires borrowing from areas that are outside one's area of expertise- one learns a lot of new and often unfamiliar things as a matter of course as a scientist.

While I am a professional scientist, I really can't talk much about what I do professionally. There are all sorts of intellectual property issues involved. I have a great deal of envy for academic scientists, who more or less have to talk about their work. But I am a scientist all the time, not just at work. I learn new stuff that interests me as an individual, and as a citizen. In this context, I am going to record a little of what I'm learning about, and why.

I build some electronic things, usually to help me measure something. I don't intend to make this a techie blog, but if it makes sense to me, I might include some of what I do for fun here.

Science and scientific method are powerful tools for understanding things like health, climate, risks of various kinds, and new technology, and one need not be an expert to learn to appreciate and evaluate the news that emerges from science. If I can record some of this in a way that someone might find useful, then this blog will be worth my time.