On an early summer afternoon about a dozen people waited to get their samples taken at a municipal building in Braine-le-Chateau, a picturesque town in the French-speaking Wallonia region.

"Initially local authorities told us that measurements were reassuring, but in reality, they didn't have any and were simply trying to keep people calm as best they could," Douglas, a 35-year-old consultant who preferred only to give his first name, told AFP.

"This kind of game has to stop," he said, adding he hoped the blood-sampling campaign launched in June would help shed light on the situation.

Anger in the region first erupted in 2023 when an investigation by local broadcaster RTBF revealed the authorities had ignored longstanding warnings about high levels of per- and polyfluoroalkyl substances (PFAS), often called forever chemicals.

It emerged that the US military, which has an airbase in the small city of Chievres, had warned the local water company in 2017 about high PFAS levels in drinking water, following an incident involving firefighting foam.

The US base advised its personnel to drink bottled water -- but locals were left in the dark for years, even after the regional government was told of the issue in 2018.

PFAS are a family of synthetic chemicals that take an extremely long time to break down.

Chronic exposure to even low levels of the chemicals has been linked to liver damage, high cholesterol, reduced immune responses, low birth weights and several kinds of cancer.

A group of more than 10,000 human-made chemicals that repel heat, water and oil, PFAS are used in nonstick pans, stain-proof carpets, and other products.

But their use is increasingly being restricted across the world due to adverse health effects.

In June an Italian court sentenced executives at a chemical plant to jail terms of up to 17 years for polluting water used by hundreds of thousands of people with the chemicals.

- 'Putting out fires' -

Water samples in Braine-le-Chateau last year revealed levels five to six times higher than a safety standard of 4 nanograms/litre (ng/L) for four PFAS recently agreed by Belgian authorities.

The exact source of the pollution has not yet been confirmed and a judicial investigation is underway.

Authorities have since ordered water distribution firms to install activated carbon filters -- a move they say has contained the issue.

Large-scale blood testing was carried out in Chievres in early 2024 -- and later extended to nearby areas.

Authorities said almost 1,300 people across about 10 municipalities had their blood samples taken to confirm exposure to the chemicals in recent weeks, as part of a fresh campaign launched in June.

The results, which could lead to new health recommendations, are expected later this year.

Wallonia's government, which took office last summer, has also decided to bring forward to 2025 new European Union rules requiring that drinking water must not exceed a total of 100 ng/L for 20 substances in the PFAS family.

"We have taken radical measures and all our distributors are now complying with this standard," Yves Coppieters, the regional minister for health and the environment, told AFP.

Nevertheless he acknowledged that "the population is very concerned", adding that without clarity on the source of the pollution, it might take decades to resolve the issue.

"Telling people not to eat their home-grown eggs and vegetables, setting standards for sewage sludge... for now I'm just putting out fires," said Coppieters, who favours a ban on all products containing PFAS.

Denmark, Germany, the Netherlands, Norway and Sweden have submitted a joint proposal for the EU to ban the production, sale, and use of almost all forever chemicals.

And the European Commission has said it is looking to ban PFAS in everyday consumer products.