Rush Limbaugh and DDT

Rush Limbaugh has been on a crusade in favor of DDT for years.  His rationale?  DDT kills mosquitoes. Mosquitoes are the main vector for malaria.  One analysis suggests that the ban on DDT may have killed as many as 20 million children.  Like a lot that Rush says, this sounds remotely plausible: malaria kills about 1.2 million a year, and about half of them are children.  But that's where the plausibility ends.   Among the problems: DDT is still allowed in all the countries that have high death rates due to mosquitoes, as long as it's strictly being used for vector control.  Because of the numerous problems with DDT, it's no longer used as much as it once was.  One of those many problems is that widespread, but not overwhelming use of DDT has led to many strains of DDT resistant mosquitoes.  Rush doesn't believe in evolution either, so this wouldn't be a problem for him, I suppose.

DDT (dichlorodiphenyltrichloroethane) is an organochloride contact insecticide.  It's able to penetrate the insect's exoskeleton and disrupt the functioning of their nerves.  While it's less toxic for vertebrates, it's a potent endocrine disruptor for them.   Endocrine disruptors interfere in a variety of ways with the body's system of hormones, causing various malfunctions.  One of its worst effects is that it causes the eggs of birds to be very thin-shelled, leading to very few of them surviving to hatching.  During the fifteen years it was heavily used, it nearly led to the extinction of many species of birds, notably including the bald eagle and western brown pelican.  (despite living in areas where both species had once been common, I never saw a single one of either between 1967 and 1983.  I remember how excited I was when I saw my first eagle in 1983.   Now I see them all the time).     DDT breaks down very slowly in the environment, which allows it to remain in the food chain, accumulating in the higher vertebrates, far from where it was originally deployed.  While DDT is a solid at room temperature, many of the other organochlorides are potent solvents--one of them, carbon tetrachloride, was widely used as in dry cleaning and in fire extinguishers.  Their widespread use led to kidney and liver disease, cancers, birth defects, damage to the ozone layer, and countless other bad effects.  They are so useful that they are not completely banned, but use is much more careful than it was in the '50s and '60s.

There are many other toxins that are not endocrine disruptors and break down relatively quickly.  For example, pyrethrum.  This is still mildly toxic to humans, but has far fewer ecological consequences.  The mosquitoes seem to have had a harder time adapting to these.  The remain more expensive than DDT, but they're nearly as effective.  More research needs to be done.   Making birds extinct is not the answer.