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Exposure to “forever” chemicals can put children and young adults at higher risk for a broad range of diseases, including diabetes, cardiovascular diseases and cancer, according to a study published Wednesday in Environmental Health Perspectives.

Researchers at the Keck School of Medicine of the University of Southern California found that PFAS, or per- and polyfluoroalkyl substances — used in a wide variety of consumer products — disrupt key biological processes.

“We found that exposure to a combination of PFAS not only disrupted lipid and amino acid metabolism but also altered thyroid hormone function,” Jesse A. Goodrich, Ph.D. assistant professor of population and public health sciences and lead author of the study said in a press release.

“Together, our findings raise the possibility that increased risk of metabolic disorders associated with PFAS exposure are caused by alterations in thyroid hormones and mediated by changes in lipid metabolism,” the study stated.

The finding about the effects of PFAS on thyroid hormone function is important because this hormone plays a key role in growth and metabolism. Any changes to its functioning during puberty can influence development of many diseases later in life, such as cancer, diabetes, heart disease.

Children and adolescents are going through critical stages of development during which exposure to PFAS may make them more susceptible to the chemicals’ negative effects.

PFAS: ‘forever’ and ‘everywhere’

PFAS are a class of more than 4,000 synthetic chemicals used to help products resist heat, oil, stains and water.

Referred to as “forever chemicals” — because they don’t break down in the environment and can build up in people’s blood and organs — the chemicals already are linked to increased risk of cancer, harm to fetal development, kidney and testicular cancer, and thyroid disease.

People can be exposed to PFAS through contaminated drinking water, food and air and through contact with consumer products made with PFAS.

Thousands of studies have linked individual PFAS chemicals to different types of disease, but researchers at the Keck School set out to find how exposure to a mix of multiple PFAS — which is what most people have in their bodies — impacts the biological processes of children and young adults.

To accomplish this, the research team analyzed blood samples from 312 adolescents who participated in the Study of Latino Adolescents at Risk, and 137 children from the Southern California Children’s Health Study.

All of the children and adolescents had a mixture of PFOS, PFHxS, PFHpS, PFOA and PFNA, common types of PFAS, in their blood, and ver 98% of participants also had a PFAS called PFDA, thought to be an endocrine disruptor, in their blood.

The researchers also measured thousands of naturally occurring chemicals in the blood and developed a biostatistical method to test how the PFAS affected these different chemicals.

This allowed them to determine how the PFAS exposure changed the way the body metabolized lipids and amino acids and altered thyroid hormone function.

Their results were consistent with earlier studies showing that exposure to individual PFAS during childhood was associated with disruption in lipid and fatty acid metabolism — but they also found other effects.

“Our findings were surprising and have broad implications for policymakers trying to mitigate risk,” Goodrich said.

According to the researchers, the study demonstrates the need to address PFAS as a whole, rather than focusing on harms caused by individual PFAS compounds.

“Our findings lend support to the argument that PFAS should be regulated as a chemical class rather than being regulated on a chemical-by-chemical basis,” the study’s authors said.

The overwhelming research that links PFAS with adverse health issues has led to widespread calls for testing of people and products and for stronger regulation of the chemicals.

Some manufacturers have eliminated particular PFAS, like BPA, but they may be replaced with other chemicals that also put people’s health at risk.