Francisco Cantú worked as a US border patrol agent between 2008 and 2012. A third-generation Mexican American, he lives in Tucson, Arizona and his job included tracking migrants in the Sonoran desert, which separates Mexico from the US. After leaving the agency, he studied creative writing and his essays and translations have appeared in magazines including The Best American Essays, Guernica and Harper’s. A former Fulbright fellow and the recipient of a Pushcart prize and a 2017 Whiting award, his first book, The Line Becomes a River, is based on journals he kept while patrolling the border and was described by US Esquire as “a must-read for anyone who thinks ‘build a wall’ is the answer to anything’”. It is published in the UK in March by Bodley Head (£14.99).

Where did the impetus to be a border agent come from?

I grew up in south-west Arizona, where my mother was a park ranger. As a child I was very close to the landscape – always out in these wild places. I went on to study immigration and border policy in Washington DC, but when I was in college reading books and academic accounts of the border, I really felt like something was missing. By the time I graduated I knew that I wanted to go back to the border, to deepen my understanding of it and be out in it.

What led you to write about your time working there?

Well, when I left, it all seemed infinitely more complex than when I joined. Writing this book was a way of grappling with those complexities and I was really concerned with acknowledging them. Acknowledging the human cost of our border policy, and the ways in which individuals are caught up in it. This policy is pushing people to cross, away from the cities, away from the heavily patrolled areas, into the most remote and dangerous parts of the desert where many of them die. I mean [our policy] really serves to weaponise that landscape. So I carry those people with me, inside me and I hold them in my mind. We don’t acknowledge or mourn these people’s deaths, we don’t read about them every day, we don’t even name them. So many of them are unidentified.

You cite a Wall Street Journal article saying that only a couple of decades ago workers commonly travelled back and forth across the border, but that after the US crackdown the border increasingly fell under the control of drug cartels, who sometimes kidnap and torture migrants in order to extort money from their families or force them to be drug mules.

If you’re a migrant looking to cross the border, looking for a job or to reunite with your family, you have to expose yourself to a different degree of risk nowadays. You have to pay for safe passage and it’s not like you’re just paying someone to bring you across. You’re also paying for protection or the blessing of the cartels that are patrolling the area in which you are crossing.

In the book you write about the emotional pressures of the job – encountering people who have been lost in the desert for days with no water, people who have escaped from violent people-smugglers, or whose friends or family have died trying to cross. At one point you say that your mind had become so filled with violence you could barely sleep and when you did you suffered terrible nightmares. Is it typical that agents suffer that sort of mental anguish?

Well, the turnover rate is very high. The suicide rate is proportionate with other law enforcement careers. But in the border patrol there isn’t a culture of talking about the way you might be impacted by the trauma or the violence of the job. I’ve shared this book with a handful of my former colleagues and most of them will say to me: “Oh, wow, I didn’t know you were going through so much, or: “I didn’t know you were having a hard time.” And it’s true, I never talked about it. I never talk about the nightmares I had with any of those guys. No matter where you stand on border policy, the job that border patrol agents are asked to do is extremely difficult and also kind of insane. I don’t think you have to become soulless in order to do the work, but I do think it is work that endangers the soul.

I have no urge to look away from the border, not just our border but borders globally

Could you make sense of it all once you’d walked away?

Part of my reason for writing this book was looking back on my time in the patrol and thinking about all the ways that I was lending myself and my identity to help enforce ultimately flawed policies. And when I look at them now, these are policies that feel violent and inhumane. And so in the book, and in my life, I was really trying to grapple honestly with my own culpability and with all the ways that I can and cannot extract myself from the work that I did and from the institutions I was a part of.

What books are you reading at the moment?

I’ve been slowly making my way through a book of academic essays called Borderwall As Architecture [by Ronald Rael]. Though I really think some of the best writing about the border is being done by poets. I’m reading a book by Javier Zamora called Unaccompanied [about the author’s journey from El Salvador to the US]. And I’m reading poems by Eduardo Corral in [a collection called] Slow Lightning. I’m a translator so I’m always thinking about what hasn’t been translated yet.

Do you read novels at all?

For me, reading fiction is sort of an escape, my guilty pleasure. I only recently read Junot Díaz’s The Brief Wondrous Life of Oscar Wao. Also Juan Gabriel Vásquez’s The Sound of Things Falling, about drug violence in Colombia.

Which books inspire you?

One that’s been really impactful for me is by Svetlana Alexievich, who won the Nobel prize a few years back. She was the first person who won in nonfiction and her book Voices from Chernobyl (The Oral History of a Nuclear Disaster) made a really big impact on me. I think it’s so important to amplify other people’s voices.

What next?

Writing is where I see myself being able to do the most meaningful work. I still see it as a tool for exploring all the questions that I still have, about the way that violence is normalised in a society. I have no urge to look away from the border, not just our border but borders globally. I think they’re sort of these microcosms of all of these painful, beautiful, violent, incomprehensible mysteries of our modern lives. We’re embodied by them.

• Francisco Cantú is appearing at Sydney Writers festival 2018, held between 30 April - 6 May at Carriageworks.

• The Line Becomes a River by Francisco Cantú is published by Bodley Head (£14.99). To order a copy for £12.74 go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99