Once I got over my initial freakout, I realized that the water guy that called me yesterday has to be wrong. When I initially got the test results back, I didn't just talk to the specialist, I also did research on my own. I would've noticed if the levels were outrageously high. I sent the testing to be done at a particular lab that is some distance from where I live, and I'm guessing the specialist I'm consulting with on the water treatment system doesn't see results from this lab very often. Sometimes, results are reported in parts per million, sometimes as micrograms per liter, and sometimes as nanograms per milileter. I am guessing that the test results I gave him are in a different measurement than he is used to, and he didn't notice. Like, the rate is really .18 whatever, and he's seeing it as 18, because it's in a different unit of measurement.
All of the information I had at the time (based on my discussion with the specialist then and my own research) was that the levels came back at not quite twice the acceptable level established by the EPA (not like 200 times, as yesterday's specialist seemed to think). But, the EPA had set the "acceptable" level at about triple the level that I have until 2001. Which is why the expert I consulted told me not to worry too much about it (because for decades the "acceptable" rate included my rate), and why I didn't worry too much about it. Because of rock formations in my part of the universe, it's pretty common to have arsenic (and radon), and people have been living with it for generations. Several of my neighbors, who presumably have water similar to mine, are quite old. And several of my other neighbors have had babies who seem to be just fine. That's not to say I don't want to fix the problem, but rather that perhaps the guy freaked me out unnecessarily yesterday.
Also, because I knew the arsenic level was higher than the EPA deems acceptable, I haven't been drinking the water since I got pregnant. Since ingestion is the principal means of exposure (not, say, through the shower), baby should be fine. (Fingers crossed).
And now, for a little laugh, a MIL update: yesterday T. had the "big talk" with her. She promised him that she "hasn't told anyone." (Not entirely the point, but okay.) He said the conversation seemed to go well, although it sound like she more understood it to mean she shouldn't tell other people, rather than that I don't want to discuss it with her. And then she told him she's been buying beach toys for the baby (she lives on a beach). I had to ask whether she understood there wouldn't actually be a baby to play with them THIS summer. Argh!