MY Roman Catholic mother, who hailed from Montrose, Angus, where I have lived for nearly two decades, used to talk about water as “Adam’s wine”. “Aren’t we lucky?” she would say, “to have pure water coming out of the tap?”

Like most children, I took this for granted. It wasn’t until I travelled extensively to film in Afghanistan, Pakistan and Tanzania that I witnessed the desperate impact a lack of fresh water can have on communities. And so, it may seem strange that it wasn’t toxic water in the developing world that became the focus of my latest documentary Flint which airs on the BBC Scotland channel. But rather, the richest and most powerful nation on the planet – the United States of America.

I first went to the city of Flint, Michigan, in the summer of 2015 by chance. I had just screened one of my previous films in nearby Detroit. A Dangerous Game (2014) is about the environmental impact of luxury golf courses for the superrich, and the film shines a light on the huge amount of drinking water golf courses guzzle in the desert in places like Las Vegas. After the screening, a Detroiter suggested I should head through to nearby Flint with my camera. Not only were residents there facing sky-high water bills, I was told, but their water was poisoning them.

Flint is the birthplace of General Motors (GM) and in the middle of the last century it was one of the most prosperous cities in the world. However, when GM shut its biggest plant in the 1970s, the city shrank rapidly from 200,000 to half that number today.

And so the infrastructure was built for a city twice that size. Bizarrely, one of the key tools for raising money in both Flint and Detroit is water. Flint residents – the majority of whom are African American – pay the highest water bills in the US.

In a bid to balance the city’s books, Michigan’s then-governor Rick Snyder sent a team of “emergency managers” to run the city. They decided on a cost-saving switch for the city’s drinking water, from the Great Lakes – to the local, contaminated river.

When I arrived, the people of Flint had been drinking this water for a year. They had immediately noticed problems – hair loss and skin rashes to start with. But then came unexplained miscarriages and mystery deaths. Those in power kept insisting the water was safe – the city’s mayor went on TV to reassure residents, drinking a cup of Flint water live on air to “prove” it.

With no-one listening to their concerns (either at the local city or state level), residents were forced to take matters into their own hands. They contacted Professor Marc Edwards, arguably America’s leading water expert. Based at Virginia Tech University, Edwards galvanised a group of his students to collect data from residents, who organised a massive city-wide water test in August 2015. The results shocked America and the world.

Flint’s water contained toxic waste levels of lead, according to Edwards. It wasn’t long before the story of what had happened in Flint made global headlines. But as I continued to film with local residents, I was struck by how little the state seemed to be doing in response.

A single case of water was on offer for Flint families, if you could drive to the local fire station to pick it up. If you were elderly and didn’t have a car, you had to walk or take the bus.

After the news cameras packed up and left Flint in early 2016, I continued to document what I saw – and it was deeply shocking. By that stage, the city’s water supply had been switched back to the Great Lakes. But large amounts of contaminants remained because the corrosive water had stripped off the protective layer inside Flint’s old lead pipes, leaving chunks of the metal floating around the system.

Flint residents were left to fend for themselves. The authorities told residents it was now “safe” to drink water with a filter. But America’s Environmental Protection Agency then warned the filters could not cope. The people of Flint did not know who to trust.

As celebrities such as Dark Waters star Mark Ruffalo descended on Flint, the confusion intensified. Residents were warned by Ruffalo’s not-for-profit Water Defence: “There are a lot more contaminants in this water than you’re being told about.” His group began their own city-wide water testing in Flint homes. And that is where the film Flint takes an unexpected twist.

For that you’ll have to watch the film, but I can provide an update on the situation in Flint itself.

Because of Covid-19, we have been unable to screen Flint in front of live audiences across the United States. Instead, the film has been playing “virtually” at festivals such as Washington DC, Detroit and Minneapolis. We’ve been holding Zoom panel discussions with local residents for post-screening Q&As.

What has struck me is how intensely real Flint’s water disaster remains today. Not only do residents have coronavirus to contend with, but trust in their water remains shattered. Many residents still use bottled water for bathing and showering. And just how those toxic lead levels will impact on the city’s children in their lives ahead has yet to fully emerge.

Anthony Baxter is producer/director of Flint. Five years in the making, the film is on the BBC Scotland channel at 10pm on Tuesday.