One major source of that PFAS is sewage contamination from failed septic systems and wastewater leaks in urban areas. This is evident by the presence of the types of PFAS – such as PFOS, PFOA, PFPeA, PFHxS, PFHxA, PFBA and PFBS – that are used as stain and grease repellents and in carpets, food packaging materials and household products.

Another major source is represented by the predominance of 6-2 FTS in the Miami River – 6-2 FTS is a fluorotelomer PFAS typically used in aqueous film-forming foam found at military and airport facilities. The Miami River flows past rail yards, industries and Miami International Airport on its way to Biscayne Bay.

We also used a model to predict how ocean currents would disperse PFAS coming out of those canals and into coastal areas. We found that the PFAS concentrations were highest close to the canals, decreased along the bay and declined as ocean water became deeper and more saline, which makes PFAS less soluble in water.

Overall, PFAS concentrations were almost six times higher in surface waters near land compared with deep-water samples collected 13 to 33 feet (4 to 10 meters) below the surface in the bay and offshore. That suggests the highest risk is to pelagic fish that hang out in surface waters, such as mackerel, tunas and mahi-mahi.

The levels of PFOS and PFOA in our study were below the Florida Department of Environmental Protection advisory levels in surface water for human health exposure. However, the advisory levels might not be protective of human and marine life.

They do not take into consideration that these chemicals accumulate through the food chain. Higher concentration in the top of the food web means PFAS could pose a greater risk to dolphins, sharks and humans that consume fish.

Many types of PFAS identified in our samples are not regulated, and their potential toxicity is unknown. We believe there is a need for federal and state agencies to develop guidelines and implement action plans to protect people and the aquatic life in Biscayne Bay.

Given the persistence of PFAS and their widespread use, it is not surprising that these forever chemicals are found in almost all water systems in South Florida and are showing up in coastal waters around the world.

While scientists look for effective and efficient ways to eliminate and remove these chemicals from water, food and the environment, people can limit their use of PFAS-containing products to reduce the amounts of these chemicals that get into the marine environment.

Here are some common products that contain PFAS to watch for: Teflon nonstick cookware; food packaging for fast food and popcorn; water-resistant clothing and cosmetics; and treated carpets.

This article was updated April 10, 2024, with the EPA issuing the first federal drinking water standards for PFAS.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Natalia Soares Quinete, Florida International University and Olutobi Daniel Ogunbiyi, Florida International University

Read more:
What are PFAS, the ‘forever chemicals’ showing up in drinking water? An environmental health scientist explains

How to destroy a ‘forever chemical’ – scientists are discovering ways to eliminate PFAS, but this growing global health problem isn’t going away soon

New PFAS guidelines – a water quality scientist explains technology and investment needed to get forever chemicals out of US drinking water

Natalia Soares Quinete receives funding from National Science Foundation.

Olutobi Daniel Ogunbiyi receives funding from the National Science Foundation awarded through FIU Institute of Environment and Center for Research and Excellence in Science and Tech.