There’s nothing worse than mosquitoes, right? Those little biters have ruined many a party, baseball game or virtually any other outdoor activity – especially in the spring and summer.
So why not just, well, get rid of them? We tried that in the United States – and the results were, um, not great.
“So the US had malaria at one point,” entomologist Tanya Latty told me for the latest episode of my podcast, “Downside Up.” “Not naturally, but it was brought in, two types of malaria were brought into the US. One from Britain, with the British settlers. The other type came in from Africa via enslaved people. And so those two types of malaria then established and became a problem in the southern US, and it was a very concerted effort in the ’40s to eliminate that particular mosquito from the United States using DDT, which at the time was all the rage.”
DDT is short for dichlorodiphenyltrichloroethane. And during the 1940s, it was seen as a panacea for America’s malaria problem – as well as a way to prevent body lice, polio, typhus and a bunch of other ailments.
DDT was so popular – and presumed safe – that there are videos of scientists actually drinking (yes, drinking!) the stuff as a way to prove its innocuousness. There was also footage of kids being sprayed with fire hoses of DDT from around that same time.
The theory was that “you could use DDT and it wouldn’t kill you or make you particularly sick, at least not immediately, as far as we know, but it would have a negative impact on the insects,” said Latty. “It would knock them out very quickly.” (DDT disrupts the nervous system of mosquitoes.)
The problem? It did a number on the rest of the environment, too. While mosquitoes might have been killed with a small amount of DDT, the animals that ate mosquitoes were exposed to larger amounts of DDT. As you went up the food chain, the amount of DDT that animals were ingesting became significant – and started to cause damage.
“By the time you get to top predators – like in the US, things like bald eagles – they’re getting pretty big doses compared to what was sprayed in the environment, and that started to have an impact on their ability to reproduce in birds,” explained Latty (There was even a point when bald eagles were on the verge of extinction because of the harmful effects of DDT.)
There are other environmental hazards caused by DDT, including the fact that it impacts all sort of insects – not just the mosquitoes we were trying to get rid of – and that it lingers in the environment for a very long time.
By the early 1970s, the US had banned the use of DDT in everything – including mosquito prevention.
There are other options to limit the mosquito population that have been developed since – including gene editing. But the DDT test case is a useful reminder that when we begin to fiddle around with nature, the consequences are often well beyond our imagination.