“For the first time in a generation, we are able to restrict chemicals already in commerce that pose risks to public health and the environment,” Jim Jones, then the assistant administrator for EPA’s Office of Chemical Safety and Pollution Prevention, said in December 2016, as he proudly announced the planned ban on certain uses of TCE. “Once finalized, today’s action will help protect consumers and workers from cancer and other serious health risks.”

At least that was the plan. But then came the Trump administration. More than two years later, no final action has been taken on any of these three proposed bans. And while the agency has said it soon intends to move at least on methylene chloride, no action is currently planned for TCE or NMP, despite the well-established public health threats associated with both these chemicals.

Similarly, on pesticides, the Trump-era EPA rejected a proposed ban on the use of chlorpyrifos, which is used on more than 60 crops, particularly in California, and has been blamed for sickening farm workers and causing development disabilities in their children. Instead, the EPA has agreed to simply to do more studies on the threats of chlorpyrifos.

The pullback on the planned restrictions on these substances reflects the massive shift in management and regulatory philosophy that has taken place at the EPA during the Trump era — not just in the way it handles toxic chemicals, but across the agency’s public health and environmental mission, from the way it protects clean air and clean water to efforts to combat climate change.

This has not simply been the typical pendulum swing that occurs anytime the party in charge at the White House flips.

Jones, the former EPA official, was no tree-hugging liberal. He had spent 30 years at the agency, under both Democrat and Republican administrations, and after he left the EPA in early 2017 he took a job with an industry trade association that represents major industrial chemical companies such as the BASF Corporation.

But well before 2016, it had been obvious to just about anyone who tracked how toxic chemicals are regulated in the United States that the time had finally come for the EPA to make some tough choices — choices that in some cases meant restricting the use of certain chemicals that might be profitable sales lines for the manufacturers. Yet once the agency had documented that specific chemicals were clearly a threat to public health, it needed to be able to move to prohibit their use.

The federal government had fallen so far behind in this task that major retailers like Wal-Mart and Target had become de facto regulators, as they were making decisions to stop selling certain harmful products, including methylene chloride, even before the EPA took action.

As a reporter at The New York Times based in Washington, I have had a particular interest in how the EPA regulates toxic chemicals and pesticides, given just how directly decisions related to these products impact the daily lives of so many people in this country — from farmworkers and dry-cleaning shop employees, to homeowners and consumers.

Prior to the election of President Trump, I specialized in writing about corporate lobbying in Washington, looking at such topics as how the pharmaceutical industry worked to kill off any price controls, or how the energy industry successfully moved during the Obama administration to get the ban on the export of crude oil lifted.

Once Trump moved into the White House, I watched his team fill key spots across federal agencies. Every president appoints experts who have views that reflect his own, and these people have work experience in the fields and industry sectors they are charged with helping to regulate.

David McIntosh, a former air pollution attorney at the Natural Resources Defense Council (NRDC), one of the country’s most influential environmental groups, took a job early in the Obama administration as a senior legislative adviser to then-EPA Administrator Lisa Jackson. Michael Goo, NRDC’s former legislative director on climate issues, soon thereafter joined McIntosh at the EPA and helped Jackson craft what would become the Clean Power Plan; after leaving the EPA, Goo was hired by NRDC as a lobbyist.

So why is it any different that the Trump administration appointed a former American Chemistry Council executive, Nancy Beck, to help oversee toxic chemical regulation, or that the EPA itself is now run by a former coal lobbyist and the Interior Department is run by a former oil industry lobbyist? That is a question I get asked frequently, particularly by conservatives.

My answer is that both sides — liberals and conservatives — do basically stack the decks, filling key jobs with people who are sympathetic to their world views and committed to executing on that mission. But there is something materially different about this alignment in the Trump era — it is such an extreme flipping of roles, with huge consequences on public policy.

Beck, in her role as a top executive at the American Chemistry Council — a trade association that represents an industry that sells at least $500 billion worth of products each year — had helped lead the charge against the regulation of certain toxic chemicals and against the rules the EPA intended to use to decide when their use should be banned or restricted.