When Scott Pruitt resigned as head of the Environmental Protection Agency (EPA) in July amid multiple ethics scandals, he left behind dozens of environmental policies and proposals that are poised to radically shift the agency’s mission.

But environmental advocates say Pruitt did more than change policies: He worked to alter the fundamental way the EPA functions, overseeing a decline in funding, staff, and access to scientific information, a direction that acting EPA chief administrator Andrew Wheeler is expected to continue.

While many of these policies are still up for legal challenge or could be reversed by another administration, they could have global implications for climate change, air and water pollution, and a host of green industries, from sustainable design to electric cars. Here is an overview of key changes to date.

Energy and the Climate
Pruitt was a major supporter for the United States’ June 2017 withdrawal from the international Paris Agreement to reduce greenhouse gas emissions. In fact, during Pruitt's tenure, the Trump administration took policy actions designed to “roll back all the important regulations issued in the last administration to reduce carbon dioxide and other greenhouse gas pollutants,” says David Doniger, senior strategic director of the Climate and Clean Energy Program at the Natural Resources Defense Council and a former EPA staffer.

One such target is the Clean Power Plan, a rule enacted under the Clean Air Act in 2015 by the Obama administration, which introduced strict controls on emissions from coal-fired power plants and encouraged states to switch to cleaner energy sources. Last October, Pruitt signed a measure to repeal the plan based on the grounds that it exceeded the Clean Air Act’s authority. But this July, the EPA instead proposed a replacement policy, dubbed the Affordable Clean Energy Rule, which removes those strict emissions requirements and requires only modest changes to coal plants; because the government has a legal obligation to address greenhouse gases, the replacement policy may withstand legal challenge better than an outright repeal.

Fuel-efficient transportation is also in the EPA's crosshairs. In April 2018, Pruitt pledged to review Obama-initiated standards that aimed to improve fuel efficiency for cars and some trucks. Shortly after Pruitt’s departure, the EPA proposed the new Safer Affordable Fuel Efficient (SAFE) rule in August that would freeze emissions standards from model year 2012 through 2026. By letting federal standards remain at the status quo, the rule would forgo an opportunity to tackle emissions from the transportation sector—the largest source of greenhouse gases in the U.S. According to a Union of Concerned Scientists' analysis, the rollback will be responsible for allowing 2.2 billion metric tons of greenhouse gases into the atmosphere by 2040.

Air and Water Pollution
In January, the EPA moved to suspend the Clean Water Rule for two years as part of an effort to rescind or revise it. The 2015 rule clarified longstanding legal confusion about the scope of the Clean Water Act by extending federal pollution regulations to small waterways and wetlands, not just larger navigable waterways. Suspending or rescinding the rule would mean fewer protections for streams and wetlands that serve as habitats and drinking water sources.

In response to lawsuits by states and environmental groups, a federal judge issued an injunction of the rule’s suspension on Aug. 16, allowing the rule to remain in effect in the 26 states that have not legally challenged it. Despite this, its ultimate future remains in limbo.

The EPA also blocked progress made by the Obama administration on curbing air pollutants and methane (a potent greenhouse gas) from the nation’s booming oil and gas operations. And the agency is reviewing its role in the Regional Haze Program under the Clean Air Act, which requires states to create plans tackling visibility problems in national parks and wilderness areas.

Chemical Regulations
In April, the Pruitt-led EPA attempted to delay a proposed ban on the pesticide chlorpyrifos, which has been found to pose risks to fetal and childhood development, but the action was found to be unjustified in a federal court. The agency recently raised further concern among environmental groups about the way it reviews the health and safety risks of new chemicals under the Toxic Substances Control Act. The 1970s-era law had been amended in 2016 to improve the process of evaluating health risks of new substances on the market. But in August, the EPA announced a new framework for the chemical-safety review process that environmental advocates and Democratic lawmakers have argued is too weak and limited in the information it considers.

A Limited EPA
Under Pruitt, the EPA has drastically redefined the scope of its responsibilities and oversight. “The agency is largely responsible for implementing a bunch of statutes, and those statutes aren’t just cookbook recipes,” says Joseph Goffman, executive director of the Environmental & Energy Law Program at Harvard University and a former EPA administrator. His group at Harvard tracks environmental regulatory rollbacks under the Trump administration and ways that the EPA’s mission has shifted. Goffman says even the interpretation of existing policies has changed; for instance, the cost–benefit ratios of policies that curb pollution have fallen because the organization has re-evaluated the health benefits of pollution reduction.

The EPA has also suffered budget cuts, though the reductions have been far less significant than what the Trump administration initially requested. For fiscal year 2019, the administration is seeking a $2.5 billion cut from the EPA’s annual budget, a 23 percent reduction. The agency’s staff numbers are at their lowest since the 1980s. Under Pruitt, the role of science in informing agency decisions has also shrunk; science advisory panels have been filled with industry representatives rather than actual scientists.

A Mixed Legacy
While Pruitt’s tenure certainly instigated a series of regulatory rollbacks, his effectiveness is up for debate. Much of his intended agenda has not yet been executed. In fact, many of his efforts to suspend or delay Obama-era rules have been rejected by the courts, says Lisa Heinzerling, a professor at Georgetown University Law Center. “The courts have found basic legal errors in these efforts, including failure to provide required process, failure to follow clear law, and failure to explain decisions in reasoned terms,” she says.

The oversights seem to be continuing. For instance, the Clean Power Plan replacement issued just after Pruitt's exit does not fully address its consequences to public health, and “this kind of [oversight] may doom the agency's deregulatory policies in court,” Heinzerling says.

But Goffman notes that even if Pruitt’s policies do not survive, he will have a lasting impact on the environment by allowing more greenhouse gases to escape into the atmosphere thanks to SAFE while stalling progress on clean energy investments. “We need a policy right now to lock in at least the downward emissions trajectory that’s currently projected for the power sector, and to trigger additional investment in clean energy so as to accelerate that downward trajectory in the medium term and long term,” he says. And under Wheeler’s leadership, Goffman adds, “the agenda that we saw Pruitt build and deploy during his year and half in office will be pursued with at least the same vigor.”