In Mill Town (St. Martin’s, Sept.), Arsenault chronicles the changing fortunes of her environmentally imperiled hometown of Mexico, Maine.

Mill Town begins as an environmental exposé, then morphs into a eulogy of Mexico. Was that always the plan?

Like its river, the stories of my town and my family have had many detours, winding paths, and eddies. This started as a genealogy story. But an accumulation of moments—just like the dioxin in our town’s river and in our bodies, expanded the scope. For example, when my husband and I were living in Curacao, I could see the Venezuelan oil refineries pumping garbage out of their smokestacks, impacting the poorer neighborhoods located downwind. It then dawned on me that yes, this was happening in my hometown, too.

You’ve observed how politicians often fail to base environmental and public-health policy issues on science. How did you see that play out in what residents called “Cancer Alley?”

In Mexico, our mill and hospital kept silent. Meanwhile, the state government created definitions—like burning old tires isn’t a hazard, but a new fuel source. At the federal level, the EPA often relinquishes much of its regulatory responsibility to the states. It’s a loop.

There’s a poignant moment when you run into an old friend while visiting Mexico, and you say things have changed there. She responds, “No, you’ve changed.” Was she right?

It shook me a little. Like sure, I have, but what does that mean? It made me wonder if genealogy was all I should be writing about.

On that thread—exploring your Acadian heritage—you’ve said that it’s a culture known for its discretion. Did that hinder you from telling this story?

Well, I didn’t start writing this book until I was 44 years old, so sure! For years, I wasn’t even certain I had a story to tell. But yes, as French-Canadian Catholics, we were taught to keep our noses clean and our heads down. You could question things, but not cause too much trouble.

How do you feel about starting your writing career at this point in life?

I don’t do things I regret, and I don’t regret things that I do. I probably couldn’t have written this story earlier. I didn’t have the perspective, the mental space, nor the time before to do it.

You write that “home is the heart of human identity, a blurry backdrop, like that fake plastic tree I leaned on for my high school yearbook photograph.” Does Mexico remain your home?

If someone asks where I’m from, I say “Mexico, Maine.” Thomas Wolfe said, “You can’t go home again.” But you can and you should. It’s where we’re from, and what makes us who we are, like it or not.