alt Hacker News> It's still nasty stuff
I've only ever personally used DMSO in chemistry labs, but Wikipedia [0] makes it look pretty safe: it claims that it has a higher LD50 than ethanol and that it's been FDA approved for human usage, so I wouldn't call it nasty. Now, I wouldn't really want to drink it because the side effects and taste sound pretty unpleasant, but it appears that it would be safe to do so.
[0]: https://en.wikipedia.org/wiki/Dimethyl_sulfoxide#Toxicity
DMSO readily absorbs through your skin, meaning it is a great carrier for pretty much anything else that you don't want in you.
At the scale of "washing tons of soil to remove DDT" it'd be quite unfortunate if something went wrong and tons of DDT tainted DMSO got dumped into the wild.