First, on Monday, U.S. Environmental Protection Agency (EPA) Administrator Andrew Wheeler sent a letter to the state warning that the federal government would hold back highway funds if it did not address a backlog of air pollution control plans, according to The New York Times. Then, on Thursday, Wheeler sent another letter to California Gov. Gavin Newsom giving the state 30 days to respond to a series of concerns about its implementation of water quality regulations, The New York Times reported further.

"[T]he EPA is concerned that California's implementation of federal environmental laws is failing to meet its obligations required under delegated federal programs. The cost of this failure will be paid by those Californians exposed to unhealthy air and degraded water," Wheeler wrote in Thursday's letter.

The letters come about a week after the administration formally moved to withdraw California's power to set its own vehicle emission standards under the Clean Air Act, a power the state has argued is essential to protecting its air quality.

"We need the extra clean cars to meet the standards set by the federal government," California Air Resources Board Chairwoman Mary Nichols said in a press conference last week reported by The New York Times. "If this prevails, millions of people in California will breathe dirty air. There will be more pollution, more asthma, more hospitalizations, more premature deaths."

California officials say this week's letters are not about the state's environment at all, but are rather further retaliation for the state's opposition to the administration's agenda on issues like immigration and environmental deregulation. California Attorney General Xavier Becerra has sued the Trump administration 62 times in federal court, according to The Washington Post. The state has 30 lawsuits pending against the administration over environmental issues alone, according to The New York Times.

"There's a common theme in the news coming out of this White House this week. The president is abusing the powers of the presidency and weaponizing government to attack his political opponents," Newsom spokesman Nathan Click said in an email reported by The Washington Post. "This is not about clean air, clean water or helping our state with homelessness. This is political retribution against California, plain and simple."

Click's remarks were a clear response to a whistleblower complaint that President Donald Trump pressured the Ukrainian government to investigate former Vice President and Democratic primary candidate Joe Biden and his son Hunter ahead of the 2020 election, which has prompted 220 House members to support an impeachment inquiry, according to TIME.

An overarching theme coming out of the White House:

Trump persistently weaponizing our government to attack political opponents.

The Director of Natl Intelligence, the DOJ, the EPA...all being used to attack those that stand in his way.

This is about retaliation. Nothing more. https://t.co/eF0adb1qt1

— Gavin Newsom (@GavinNewsom) September 26, 2019

In Thursday's letter, Wheeler echoed remarks made by Trump last week that homelessness in California was threatening its environment.

"If these Democrat liberal politicians don't straighten it out, the federal government will have to come in. We're not going to lose cities like Los Angeles, San Francisco and others that are great cities. We're not going to allow that to happen to our cities," Trump said, as NPR reported.

Wheeler's letter cites reports of human feces piled on the streets of Los Angeles and San Francisco.

"The EPA is concerned about the potential water quality impacts from pathogens and other contaminants from untreated human waste entering nearby waters," Wheeler wrote. "San Francisco, Los Angeles and the state do not appear to be acting with urgency to mitigate the risks to human health and the environment that may result from the homelessness crisis."

But environmental and homeless advocates have criticized the president for treating homelessness as a threat primarily to the environment or appearance of certain cities, instead of to the well-being of homeless people themselves.

"The way to reduce the impacts from homeless encampments is to reduce homelessness," Save the Bay Executive Director David Lewis told NPR.

Our ED @DavidLewis speaks out: "@realDonaldTrump has less standing to complain about #pollution and #homelessness than pretty much anybody since his administration is actively gutting the #CleanWaterAct and other environmental laws that protect us all from pollution.” https://t.co/zCNRgabRDq

— Save The Bay (SF) (@saveSFbay) September 19, 2019

Wheeler also accused California of other water quality problems. The Washington Post highlighted two, and explained California's response:

His examples include a "years-long practice" in San Francisco of discharging more than a billion gallons of combined sewage and storm water annually into San Francisco Bay and the Pacific Ocean without treating it fully for all biological contaminants.

San Francisco officials said this discharge is being done under a federally approved permit, and 99 percent of it is storm water.

San Francisco is one of the few major American cities that combine storm water and sewage flows that is not operating under a federal consent decree. It is spending billions to upgrade its aging infrastructure, including $4.8 billion to improve regional and local water systems used by 2.7 million people. It has also launched a 20-year, multibillion-dollar sewer system upgrade.

Thursday's letter also called out high amounts of lead and arsenic in California water, but former Obama-era regional EPA head Judith Enck said that other states, like Texas and Louisiana, had more violations.

"I'm not going to say that enforcement isn't a problem, but there are other states that are far worse than California," Enck told The New York Times. "This an obvious attempt at political intimidation."

Our take on @realDonaldTrump's attack on #cleanercars: "Trump has married his administration-wide hostility to the environment to his personal vendetta against California." @EcoWatch https://t.co/ssv5x2qeDf

— Safe Climate Campaign (@safe_climate) September 22, 2019