The following is part three of three in a series looking at EPA rules that might not be as well known as the Clean Power Plan or the Clean Water Rule — commonly referred to as the Waters of the U.S., or WOTUS — but that still could be altered significantly under the new Trump administration. This story will look at former President Barack Obama's environmental legacy more broadly and the potential impact of reversing eight years of his policies. The first article discussed the National Ambient Air Quality Standards and the second looked at the effluent standards.

Surrounded by St. Patrick's Day revelers and a display of seafood, the Sierra Club's Mary Anne Hitt revealed, on a live TV broadcast in 2011, the level of mercury found in a lock of hair from "Good Morning America" host Sam Champion.

The results? Champion exhibited a mercury level that was two to three times what the U.S. EPA deemed safe. "I'm not too happy about that," Champion quipped.

Hitt explained that Champion's mercury levels could go down in three to four months if he were to stay away from seafood with high mercury content, such as swordfish and other predators, and switch instead to species that typically have lower mercury levels, including salmon and trout.

Whether Champion lowered his mercury levels following Hitt's "Good Morning America" appearance is unclear. But if he did, Hitt, the director of the Sierra Club's Beyond Coal Campaign, suggested in a recent interview that his achievement may have been due in part to the enormously successful mercury rule. According to Hitt, pregnant women no longer have to worry as much about exposure to the chemical as the nation's coal-fired power plants have moved to cut emissions of mercury in direct response to that rule.

"I think sometimes we don't do as good of a job as we should [at] connecting the dots to the benefits in people's real lives," Hitt said. Champion's haircut was part of a larger campaign by the Sierra Club that offered free testing and education on reducing mercury exposure. "I was just for some reason thinking back on that, and thinking, there is something very tangible that we can point to over the past eight years."

Hitt also said sulfur dioxide and nitrogen oxide pollution are at their lowest levels since the group began tracking emissions. "The bottom line is we have seen very dramatic reductions in air pollution from coal-fired power plants that is ... linked to very serious health problems like asthma attacks and heart attacks, and premature deaths," Hitt said. "So the air is cleaner, and it's gotten cleaner over the past eight years, and that is something very exciting."

And thanks to the coal ash rule and effluent standards, Hitt said, the power industry is on track to prevent the discharge of 1.4 billion pounds of pollutants into the nation's waterways.

These are just a few examples of the environmental legacy left behind by former President Barack Obama, according to Hitt. With the change in administration, she and other environmentalists worry about the impact President Donald Trump's policies may have on air and water. Trump has pledged to roll back environmental regulations, restore the coal industry and encourage further investment in natural gas extraction.

"When President Obama went into office, there were no federal standards whatsoever for mercury pollution from coal plants, carbon pollution from coal plants, water pollution from coal plants, and the standards for air pollution were not adequately protecting our health," Hitt said.

According to American Lung Association Senior Vice President for Advocacy Paul Billings, the Clean Power Plan, Cross-State Air Pollution Rule and Mercury and Air Toxics Standards, combined, are expected to prevent as many as 50,000 premature deaths per year once fully implemented. CSAPR and MATS have already been implemented, but many of the gains that have been achieved thus far will be lost should continued progress on those rules be slowed down, Billings said.

"You hear a lot of shrill, over the top rhetoric from the polluters and their friends in Congress. Clean Air is overwhelmingly popular with the American people, and the Clean Air Act passed with strong bipartisan majorities," Billings said.

Trump has said that the Clean Power Plan for regulating carbon emissions from existing power plants will be at the forefront of his efforts to roll back some of Obama's environmental regulations. But Hitt said she is concerned about all the other clean air and water rules on the books, saying that she is unsure exactly what other regulations might be in the new president's sights. The Natural Resources Defense Council's David Doniger said various conservative think tanks, such as the Heritage Foundation and Americans for Prosperity, have come up with "hit lists" of regulations they would like the new administration to repeal.

But given the amount of work involved in rescinding a rule, both Doniger and Hitt see Trump's regulatory rollback policy as overly ambitious.

"You have to tear a building down by the same ... process that you built it up. So it isn't something that can be done with a stroke of a pen," said Doniger, who is the director of the NRDC's climate and clean air program. "If they try to do these things by executive order ... you'll see a pretty quick response from us in the public and, if appropriate, in the courts."

Hitt agreed. "There are only so many days in the year and as we have seen over the past eight years, the wheels of government turn slowly for better or for worse." She believes that Trump will face judges that are not particularly sympathetic to his agenda.

"One thing I remember from the George W. Bush administration is they came in making great promises about wiping all the air and water regulations off the books and tying the EPA's hands behind its back. Most of the things that they tried to do were illegal," Hitt said. The Trump administration "may be making these grand proclamations, but they may very well overreach and do things that the courts may find are illegal."

Doniger called on Democrats in Congress to stand up against any attempts to weaken environmental laws. Democrats boycotted a vote to advance Scott Pruitt, Trump's nominee for EPA administrator, on Feb. 1 and 2, but Republicans were able to move the matter forward anyway.

'Smart regulation'

But while environmentalists are fretting about the future of environmental policy, energy industry leaders are cheering what they see as a chance to ease burdensome regulations that hampered investment under Obama. National Mining Association President Hal Quinn, speaking at the U.S. Energy Association's State of the Energy Industry conference in Washington, D.C., on Jan. 31, cheered efforts underway in Congress to repeal the Stream Protection Rule. That rule adds new water quality monitoring and restoration requirements for coal producers operating near streams and was pushed through in the waning days of Obama's presidency.

"I'm sleeping much better," Quinn quipped. "For the last three years I was sleeping like a baby. I was waking up every three hours and crying." He expects Republicans to move on lifting the coal leasing moratorium as well.

Obama also placed a moratorium on offshore drilling in parts of the Arctic and Atlantic oceans in December 2016. American Petroleum Institute President and CEO Jack Gerard said drilling in these areas could create as many as 800,000 jobs. According to Gerard, "It's more about smart regulation. It's more about, how do you accomplish your stated objective and purpose, without imposing unnecessary and undue cost."

Quinn said permitting a new coal mine can take eight to 10 years, which is twice the amount of time it took to build the Golden Gate Bridge.

Gerard said trillions of dollars in investments could be made in energy infrastructure in the U.S., but over-regulation has had a "chilling effect" in boardrooms across the nation.

"We've got to restore the rule of law in the United States. I know that sounds extreme, but that is in fact what has happened in some of these processes and these permitting decisions," Gerard said. "We've got to be able to tell those that risk private sector dollars, that when you meet and qualify in a permitting process, that we're going to honor that permit."