Found in fire-fighting foams, grease-resistant pizza boxes, nonstick frying pans and stain-resistant rugs, synthetic chemicals—called PFCs—make our everyday lives a little more convenient. In the long run, though, they make life much more toxic for us—and wildlife. 

Most recently, researchers found this persistent pollutant in all five species of endangered or threatened sea turtles at levels approaching those known to be toxic in other animals, according to a study from Hollings Marine Laboratory in Charleston, South Carolina. 

Once thought biologically inert, the most toxic members of the PFC family of perfluoroalkyl compounds never degrade in the environment and have become widespread since their invention in the 1950s, contaminating wildlife the world over. 

The chemicals enter our water supply, making their way to the sea, where they are ingested by filter feeders such as mussels and sponges. “Through the food web, one particular PFC, called PFOS, has accumulated in the turtle’s tissues to levels that are nearing those that impair the neurological and immune systems,” says Jenn Keller, biologist and lead author. “In laboratory animals, the chemical is also known to cause liver and thyroid damage, testicular and mammary gland tumors and reproductive problems.”

PFCs have also turned up in the blood of albatrosses, bald eagles, dolphins, polar bears, seals and sea lions—and in the blood of almost every U.S. resident screened for the chemical. 

The U.S. Environmental Protection Agency has made some progress in reducing PFC use. However, because they do not break down naturally, the chemicals will persist in the environment for years to come. 

Turns out these modern-day marvels aren’t so marvelous after all.