The Danish Environmental Agency (Miljøstyrelsen) released the number of polluted locations following consultation with local municipalities.
While 25 locations had already been reported to authorities as potential health risks, that number has now more than doubled according to information released by the authority.
Pollution at the 52 sites comes from fire service training. The chemicals in question are found in the foam used by emergency services to put out fires.
The pollution can represent a health risk to humans if ingested via cattle, gardens with edible plants, leisure fishing or bathing in contaminated areas, the Environmental Agency said.
At 35 of the 52 locations, analysis of the suspected pollution is underway or further investigation has been ordered, it said. No details have been revealed as to investigations at the remaining locations but the agency is to follow up on the issue with local authorities, it said.
PFAS (per- and polyfluoroalkyl substances) are large group of synthetic chemicals used in various products since the early 1950s. Their past uses include foam in fire extinguishers, food packaging and in textiles, carpets and paints.
PFAS and the related PFOS persists in the environment and have been detected in humans and wildlife, giving rise to with health concerns.
“(PFAS) can be detected in low concentrations in the blood in populations all over the world. PFAS is unwanted in the environment and its impact on health is a cause for concern,” the Danish Environmental Agency said.