Donald Trump has baffled medical professionals and energy experts alike, claiming windmills can cause cancer.
The US President was giving a speech at the National Republican Congressional Committee's spring dinner on Tuesday when he made the false claim.
"We've ended the war on American energy - the United States is now the number one producer of oil and natural gas anywhere in the world, and that all happened over the last two years," he told the crowd.
"Hillary [Clinton, former presidential rival] wanted to put up wind. Wind. If you have a windmill anywhere near your house, congratulations - your house just went down 75 percent in value. And they say the noise causes cancer. You told me that one. Reaow, reaow, you know the thing makes the sonar."
There is no evidence windmills can cause cancer.
"The American Cancer Society is unaware of any credible evidence linking the noise from windmills to cancer," the organisation told the New York Times.
In contrast, the World Health Organization estimates fossil fuels - like the ones Trump says the US now leads world production in - killed 4.2 million people a year, with 91 percent of the world's population living in areas where its air pollution guidelines are not met.
A 2012 analysis found that for every trillion kWhrs of energy produced in the US, coal kills 15,000, wind kills 100 (usually from falls during maintenance) and nuclear power, zero.
A 2013 study found no evidence home values are impacted negatively by nearby wind projects, and the New York Times said a wind farm built near Trump's golf course in Scotland didn't affect its property value.
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Trump went on say windmills are creating "graveyards" for birds.
"If you love birds, you'd never want to walk under a windmill because it's a very sad, sad sight. It's like a cemetery. We put a little, we put a little statue for the poor birds. It's true. You know, in California if you shoot a bald eagle they put you in jail for five years - but the windmills wipe them out."
It's unclear exactly how many birds are killed by windmills each year. One study found it could be up to 328,000 a year in the US - but this figure is dwarfed by how many die after crashing into buildings, which the US Fish and Wildlife service estimates could be as high as 988 million - 3000 times more.
Trump has a history of lying and making false statements. As of last month, the Washington Post had collected more than 9000 since he became President in 2017.