Eating a fish caught in the river or lake anywhere in the United States is like drinking a month’s worth of water that’s contaminated with toxic “forever chemicals,” according to CBS.

The chemicals, called PFAS, were founded in the 1940s to resist water and heat are used on household items such as non-stick pans, textiles, fire suppression foams and food packaging.

Now, according to CBS, those chemicals are indestructible and pollutants have built up over time in the air, soil, lakes, rivers, food, drinking water and even our bodies.

Researchers say they have analyzed over 500 samples from  rivers and lakes across the United States between 2013 and 2015.

The median level of PFAS in the fish was 9,500 nanograms per kilogram, according to a study published in the journal Environmental Research.

Nearly three quarters of the detected “forever chemicals” were PFOS, one of the most common and hazardous of the thousands of forms of PFAS.

Eating just one freshwater fish equalled drinking water with PFOS at 48 parts per trillion for a month, the researchers calculated.

Last year, the Environmental Protection Agency lowered the level of PFOS in drinking water it considers safe to 0.02 parts per trillion.

The total PFAS level in the freshwater fish was 278 times higher than what has been found in commercially sold fish, the study said.

There have been growing calls for stricter regulation for PFAS, which have been linked to a range of serious health issues including liver damage, high cholesterol, reduced immune responses and several kinds of cancer.