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In this investigation, scientists measured concentrations of these chemicals in the tissues and diet of tree swallows, a migratory bird found throughout North America.

Researchers noted the high concentration of forever chemical perfluorohexane sulfonate at a site whose sources include residual from the manufacturing plant near Cottage Grove, Minnesota, and associated waste disposal sites, but also from other numerous other household and industrial sources originating in the Minneapolis/St. Paul metropolitan area.

The investigators found that despite differences in exposure levels to these chemicals, there was no statistically significant association between chemical exposure and reproductive outcomes such as whether birds hatched or grew to the point where they could take flight.

Because of their strong chemical bonds, these substances do not easily degrade in the environment.

A new study published in Environmental Toxicology and Chemistry by Oxford University Press reports that many tree swallow populations across the United States are living in areas with high levels of exposure to “forever” chemicals.