As he was returning to the White House from a rare trip to the West Coast, Trump told reporters on Air Force One late Wednesday that there’s a tremendous amount of raw sewage and used needles from San Francisco’s homeless going into storm drains and then into the Pacific Ocean.

The president accuses the city of being in “total violation,” as he planned to ask the Environmental Protection Agency (EPA) to serve them with a notice soon.

“We have tremendous things that we don’t have to discuss pouring into the ocean. You know there are needles, there are other things,” Trump said, without getting specific on what environmental laws San Francisco might have violated. “They have to clean it up. We can’t have our cities going to hell. These are great cities. And we can’t lose our great cities like this.”

Trump’s comments came after he spent two days meeting supporters and fundraising in the San Francisco Bay Area, Los Angeles, and San Diego. The president also toured a barrier under construction near the U.S.-Mexico border. Before heading west, Trump said that homelessness in San Francisco and L.A. was ruining “the prestige” of two of California’s largest cities.

But San Francisco city leaders struck back at Trump. Mayor London Breed responded to the president on Twitter late Wednesday by saying her city is responding to all issues.

“The President is cutting clean air and clean water standards, restricting our ability to regulate car emissions, and denying climate change even exists. He’s cut funding for homelessness and affordable housing. In SF, we’re meeting the challenges on our streets,” Breed said in a series of tweets. “If the President wants to talk about homelessness, we are committed to working on actual solutions, like adding 1,000 new shelter beds by next year and working to pass a $600 million affordable housing bond to create more badly needed housing.

“We’re dedicating services and treatment for our most vulnerable suffering from mental illness and addiction. We will continue to do this work, and we wish the federal government would offer support on solutions that help people exit homelessness,” Breed continued.

California State Senator Scott Weiner, a frequent Trump critic whose district includes San Francisco, also chimed in Wednesday by tweeting, “More Trump slander against cities, this time San Francisco. Trump is making homelessness & addiction worse by cutting healthcare & affordable housing. I wish Trump would have his EPA enforce against actual environmental problems, but I guess that would be too much to ask.”

Nearly 10,000 people are reported to be homeless in San Francisco, according to the city’s official count released in July. Among the homeless people polled, when asked what prevents them from escaping homelessness, 63% said that they couldn’t afford to pay rent in the city, one of the largest in the country. That figure is up from 54% in 2017, and 48% in 2015.

The average rent for a one-bedroom apartment in San Francisco is more than $3,700— and climbing, according to rentcafe.com.

When polled about what contributed to being homeless, 26% of respondents blamed job loss, 18% cited alcohol or drug problems, and 13% said eviction. Another 12% of those polled also cited conflicts with family or friends who had previously provided shelter.

Trump’s warning of taking action against San Francisco also came on the same day that he revoked California’s waiver for auto emissions, likely setting up a potential legal battle between the Trump administration and the state, which has repeatedly sued over Trump’s previous policies.

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