DDT exposure routes are ingestion, transdermal and inhalation. The only IDLH number I can find is for inhalation @ 500 mg/m^{3. The NIOSH exposure limit (for the workplace) is 0.5 mg/m}3.

IRIS summaries for non-carcinogenci chronic health hazard and lifetime carcinogenicity are listed here:

http://www.epa.gov/iriswebp/iris/subst/0147.htm

here’s another interesting recent defense of Rachel Carson:
http://www.isreview.org/issues/57/feat-rachelcarson.shtml

DDT is not highly toxic to humans but is unlikely to be used on a bed net that a child or infant might suck on overnight. Just imagine the uproar.

The link below shows the potencies of the various insecticides approved for IRS - it appears that the insecticides approved for use on bed nets are also used for IRS. It is worth noting that the only insecticide on the list with a potency approaching the pyrethroids (bendiocarb) was withdrawn from the US market because of the danger it poses to children, who might lick sprayed surfaces.

http://www.who.int/whopes/Insecticides_IRS_Malaria_ok.pdf

I don’t understand. I didn’t think that DDT has genuine mammalian toxicity (I’ll check). I would guess it is the higher potency.

OK no luck with google scholar so I (blush) went to the Wikipedia. My reading of the evidence is that it is about what one would expect for a benign chemical. However, it seems very likely that concerns about human toxicity of DDT are a factor. I will go on about the wiki at my blog (when blogger lets me)

Anyway I learned something here. Thanks.

It’s funny how libertarians, while supposedly so excited by the true free market, always seem to end up supporting distorting monopolies – nuclear power, aerial spraying, big tobacco, big oil.

It’s almost as if they weren’t being honest about their motives.

It’s not clear to me exactly why pyrethroids are favoured more in this context than in relation to spraying.

Comments are still open here, with one of the more bellicose of the Volokh commenters:
http://www.thechristianalert.org/index.php/2008/02/15/ddt?blog=5

Or, please, feel free to drop by my blog and leave a comment on any of the several threads about DDT and Rachel Carson. I posted a day or so ago about the happy piece of news I had missed earlier—Sen. Coburn released his hold on the bill to name the post office in her hometown after Rachel Carson, and the ceremony took place on May 27, in Springdale, Pennsylvania.

Every bit of small encouragement helps—helps me, at least.

I don’t see any advantage to untreated bed-nets. The evidence that insecticide on bednets saves many lives is strong
http://bmj.bmjjournals.com/cgi/content/full/322/7281/249
(note permethrin not DDT in that case). I don’t see how suggesting to people that they put insecticide on their bed-nets could reduce their use of bed-nets.

That’s a key part of what drives global warming denialism in the US, and that’s why you don’t see that denialism to the same extent in the UK. Like evolution by natural selection, which is an existential threat to a certain popular variety of religious fundamentalism, global warming is an existential threat to libertarianism.

You cannot hold that minarchism is the solution to every problem, and yet believe that human-induced climate change is one of the biggest problems facing our planet. The two beliefs simply are not compatible.
Just as you cannot simultaneously believe that the Bible (or the Torah, or the Koran, etc. etc.) is the unerrant word of God, to be taken literally, and that evolution is fact.

Cognitive dissonance is a powerful thing.