Gina McCarthy — Boston native, Irish Catholic, lover of Guinness beer and a good laugh — has been a central player in the Obama administration’s work to reduce greenhouse gas pollution and combat global warming at home and abroad.

A career environmental bureaucrat and a veteran of Republican administrations in Massachusetts and Connecticut, McCarthy promised a “common sense” approach to fighting climate change during her 2013 confirmation hearing.

Although she contends that the Obama administration has pursued exactly that, the Environmental Protection Agency has run into stiff opposition from the oil, gas and coal industries in recent years.

The administration’s central effort to regulate carbon emissions from power plants, for example, remains stalled in federal court.

President-elect Donald Trump has vowed to scrap that Clean Power Plan and other key environmental regulations from the Obama era, and his nominee to replace McCarthy, Oklahoma Attorney General Scott Pruitt, seems eager to give it his best shot.

As she prepares to leave office, McCarthy sat down with The Washington Post to discuss the accomplishments and frustrations of her tenure. She reflected on the water crisis in Flint, Mich., the importance of continued domestic and global leadership on climate change and the need to protect the integrity of the science at EPA and other federal agencies.

The exchange that follows has been edited for length and clarity:

The Washington Post: What are your thoughts about your potential successor, Scott Pruitt? You’re certainly familiar with him, but usually from the opposing side of a courtroom. He’s been among the most outspoken critics of EPA.

Gina McCarthy: I’m thinking he has a big role to do here. He really doesn’t have a great deal of familiarity with the agency and the breadth of what it does, even though he has sued us on a number of occasions. I’m looking forward to him spending a little bit of time before he jumps at what his priorities are, because talking about it outside and then sitting at this table is a whole different ballgame. He is smart enough to know that he’s taking an oath to do a job, that this agency has a good mission and we’re proud of it. He’s going to have to figure out how he makes his mark.

TWP: Donald Trump has promised to roll back any number of things that the Obama administration has done, namely the Clean Power Plan. He has promised to pull out of the Paris climate agreement, which you played a key role in. He’s promised to get rid of the Waters of the U.S. rule. He’s called what EPA does “a disgrace.” And the folks that he is appointing seem determined to see that through. How have you wrestled with the prospect of much of your work being undone?

McCarthy: I’ve certainly heard all of this. I’m concerned, without question, by much of what I’d call political rhetoric. But I feel pretty confident that what we have done is really very solid work. There are clear records, factual records and science behind the decisions we’ve made. While I know that Mr. Pruitt, when he was attorney general, called what we did overreach in many different ways, if you really look at it, this is standard work we do in this agency and have done for a long time very successfully. So I don’t feel like we’ve broken new ground as much as we’ve applied the law and the science the way we’re supposed to.

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[And] he hasn’t just gone after the Clean Power Plan; he’s gone after the Clean Water Rule, he’s gone after Clean Air Act rules that we have done. Mercury and air toxics standards — it’s already done, [companies] are already complying. We’re so past that. We’ve worked our way through regulations that were either not done in the prior administration or done badly and came back to us. There was a long, very large body of work we had to get through. As far as I know, we’ve done it extraordinarily well. So it’s not like a blink of an eye and all that goes away.

TWP: You said it’s not partisan to care about clean air and clean water. And [Trump and his nominees] say the same thing, that they care about the EPA’s mission of clean air and clean water. But they argue you have to free companies from unnecessary regulations. What would your response to that be?

McCarthy: It probably won’t surprise you to know I disagree. … The goal of government is supposed to be to have both. Where you can have cost-effective regulation and regulation that grows jobs, that’s where you ought to go. I don’t think EPA’s only task is to regulate. Our task is to reduce pollution with the best tools available. So we do it with voluntary programs as well as regulation.

TWP: You mentioned the evidence that underpins the regulations you’ve written. I’d like to talk about the role of science, because there’s been a lot of talk about that in recent days and worries whether the next administration will rely on science, will trust the science, will protect scientists. From your perspective, what role does science play at EPA?

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McCarthy: Science is everything. Almost every action we take is bounded by what the science tells us. It’s based on a factual record of where the world is today and what is our obligation under our mission. Science needs to be protected. Any effort to undermine that science in a way that would give undue influence to folks that aren’t scientists is a really big problem.

But it’s not just for EPA. You can’t selectively say, “I’ve decided I don’t like the science on climate, so let’s find a way to revisit that,” without saying, “I’m revisiting the way the United States of America and, frankly, every country does science.” It’s something that people need to watch and protect. In this agency, if we’re asked who worked on climate change, I have a list of 15,000-plus people. Because everybody in this agency, one way or another, has touched the issue of climate.

Why wouldn’t something like climate change, which impacts everything we do, not be on everybody’s agenda? It’s just important for people to remember that the career staff were hired for their scientific credentials, and our job is to make sure that their integrity is maintained.

TWP: Can you illustrate an example or two … where you’d be lost without the scientific basis?

McCarthy: It’s fundamental to how we do clean air. I need to understand how dirty air hurts individuals to know what clean air looks like and what the goals are we should be moving toward. If I don’t have science, I don’t have anything. It is fundamental to absolutely everything we do.

The amount of science that goes into an Energy Star label, it’s enormous. For us to actually evaluate appliances and to tell people the greenhouse gas reductions achieved through those but also the energy savings and costs — it’s changed appliances forever.

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TWP: What regrets will you leave with? Or maybe a better way to ask that is, how could the EPA have done better while you were here? Where did it fall short?

McCarthy: One of the areas, I think, is an area the next administration is going to have to make some big progress on: clean drinking water. There have been lots of lessons learned about how vulnerable some communities are. I really wish that the Clean Water Rule could have been better received by folks who didn’t understand it or that just read news stories about it. The Clean Water Rule is essential for source protection for 170 million people who rely on rivers and streams that are now unprotected for their drinking water.

So it’s a big deal. And the investment that needs to be made in drinking water is substantial. Now, the president-elect wants to do infrastructure investments? I just hope that this agency is able to put drinking water on the table as part of that. There are old, aging systems that we continue to rely on, and we just can’t. Nobody really wants to spend money when all it is are pipes in the ground that you’re never going to see. But ask people that same question when they have a contaminant in their drinking water system.

TWP: Are there other things you wish had gone differently?

McCarthy: EPA does not have the strong relationships with rural communities that it has with urban communities. We work in a lot of communities, we work on a lot of urban-related issues. We have great relationships with mayors. But we have tended to not be able to have a very compelling rural agenda and to build constituencies there. That’s been challenging for us. Because we do know that runoff from agriculture and storm water — all these small sources of nutrients that are getting in our waters and streams — are the biggest challenge we face right now.

If we can’t identify a partnership or collaborative approach, we’re going to be in trouble in trying to figure out how to address those in ways that won’t require huge investments downstream in treatment facilities. Certainly, I didn’t make the progress I wanted to make in building bridges with agriculture and in finding a way to articulate a really robust rural strategy. I know rural America is struggling right now, and I think when they see the word “regulation,” they just look at that as being money that they’ll have to spend. I look at it as being investments that need to be made. So, there’s an opportunity the next administration could take in recognizing how you meet this environment and economy nexus in rural communities. It’s a challenge.

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TWP: The EPA acknowledged shortcomings in Flint. Obviously, there was also a huge state role there. But how confident are you that Flint can be made whole again, whatever that might mean? Trust was long ago lost. How does that get fixed?

McCarthy: That’s a really good question. I know the drinking water situation is getting fixed. We’ve made more progress than anyone could have anticipated at this point. But Flint was never just a drinking water problem. It was a community that was very vibrant at one point, with large auto manufacturing businesses, and it just got disinvested in the ’70s and ’80s in a way that devastated their economy. If you go there, you know this didn’t happen a year or two ago. This is a significant problem.

Flint is not alone in being a shrinking city. We’re doing great at getting the water quality up, but it’s too large a system. They have neighborhoods where they have one person living in them. You can’t service one person in a system like that without having stagnant water everywhere. Stagnant water is not your friend in a drinking water system. So there are long-term challenges there that have to be fixed. And it’s a real serious question about how the economics work in a city that has such high poverty levels with such high vacancy. It’s like Detroit, only smaller. There needed to be a huge national effort to address that.

TWP: If the next administration pulls back from climate action domestically and internationally, what role are cities and states going to play in combating this issue? And is that enough, if you essentially don’t have the federal government participating?

McCarthy: I’ve worked at the local level and the state level and the federal level. I’ve been working on climate change now for 25 or 30 years. The only action that the United States has been doing up until a very short time ago has happened at the local and the state level. Mayors are our champions. The reason is that they cannot deny the impacts that are happening. Good luck saying “climate change isn’t real” in some of the communities that are facing the brunt of the intense storms and the fires that are raging and the droughts that are happening. People know it’s not business as usual. And so they’re demanding action.

States and regional efforts are going to continue. But I’m hoping that if this next administration sees the same value in international leadership, that will not be the only thing happening.

TWP: And for you personally, what’s next?

McCarthy: Vacation for a little bit. And then we’ll see. I’m not retiring. I may be over the hill, but I don’t think I am — depends on how big a hill, I guess. I’ll still be active in these issues, and I’ll find an opportunity for myself. … I think I’ll be as vocal as I can be. This is a great agency, and its career staff needs continued support. While I recognize that the next administration can put its mark on things, I’m going to be watching the science more than anything else, because I need to make sure our science remains credible.

