Researchers have found concerning levels of a harmful class of industrial chemicals in infants that are exclusively breast-fed, according to a report on Fox News.

A new study by scientists at the Harvard T.H. Chan School of Public Health in Boston and Danish institutions discovered that concentrations of perfluorinated alkylate substances (PFASs), a class of potentially harmful chemicals, can build up in breast-fed infants by as much as 20-30 percent each month.

PFASs are used in waterproof clothing, paints and some food packaging.  A recent study linked these chemicals to problems with the immune and reproductive systems in laboratory animals.

The researchers also  found increased levels in children who were partially breast-fed, but at a lower rate.  Some of the children tested actually had blood levels of PFASs that were higher than their mothers’.

The study was done on 81 children form the Faroe Islands and the scientists believe most of the PFASs come from a seafood diet.  The nation is located about halfway between Norway and Iceland, in the North Atlantic.  Researchers noted that mothers in North America have similar levels of PFASs in breast milk to those in the study.

The United States and other countries currently have regulations to limit the use of two types of PFASs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), in drinking water.  Earlier studies have uncovered evidence that those two compounds may cause harm to hormones and possibly cause cancer.

The co-leader of the study, Dr. Philippe Grandjean of Harvard, said there are ways for nursing mothers to eat seafood while limiting their exposure to PFASs.  He recommended eating sardines and smaller fish that haven’t accumulated harmful levels.

He also warned mothers to be aware of PFAS levels in their local drinking water, as some states in the U.S., notably Ohio and West Virginia, sometimes have high concentrations.

The scientists advise that breast milk is still the healthiest option for infants and they encourage mothers to continue to breast-feed.  They say their purpose for releasing the findings is to raise awareness of the situation.

The findings were published in the journal Environmental Science & Technology.