La Zona is such a closed area, a dangerous, outlaw area. My time in the Zona was a time outside of society, almost out of the real world. And the girls there had such a sense of irony and sarcasm. They were also really interested in my film. They'd be like, "Thank God we live in Mexico, because our kind of prostitution has a heart. We wouldn't want to sit behind a glass cage or be sold by our own mothers. We have free will."

You can become an alcoholic working in an office in Los Angeles. It's very easy to say because I do this shameful job I take drugs or drink, but the real reason prostitutes take drugs and drink is because prostitution is a party area. It's not about desperation, it's the surroundings.

On one hand, prostitutes don't struggle because it's simply their life. In Mexico and elsewhere, once they get out of these places [brothels] they have a pretty square life. In Bangladesh it's different because they live in the brothel, it's sort of a prison, but still there are two sides. When they think of their religion and their upbringing, they can be very moralistic. They're moralistic about giving blow jobs. On the other hand, they have an everyday life where there's no room for shame.

I've made many documentaries, but prostitution was the hardest in terms of gaining the trust of the people being filmed.

I don't aestheticize anything. I don't even use lights. The working girls do one thing all day: They make themselves pretty. That's their job and their money. In a way, I had the best makeup artists, hairdressers, and art designers in the world.

I think beauty is the splendor of truth, so if the people I portray think they're beautiful, they're beautiful. I don't make them that way.

Sometimes the presence of a camera is like opening a door, because many people want what Andy Warhol called "15 minutes of fame." But prostitutes don't want that.