Study finds flame retardant TCEP biomagnifies in rivers but dilutes in oceans

A new study comparing marine and freshwater food webs found that toxic organophosphate flame retardants behave very differently depending on the ecosystem. Researchers say TCEP biomagnifies in the Songhua River but dilutes in Liaodong Bay, a split that could affect risk assessments for fish, wildlife and people.

Why it matters: - The same flame retardant can move up a river food chain or fade out in an ocean food web. - That difference matters for pollution monitoring, fish consumption risk and how regulators assess chemical safety. - The study suggests freshwater ecosystems may need more scrutiny than marine systems for some organophosphate esters, especially TCEP.

What happened: - Researchers from Changchun Normal University and the Chinese Academy of Sciences compared organophosphate ester behavior in two aquatic food webs for the first time side by side. - The study analyzed 498 organisms from 34 species collected in Liaodong Bay and the Songhua River in northeastern China. - The findings were published in ENGINEERING Environment, Volume 20, Issue 11, 2026. The paper is available via the study DOI.

The details: - Organophosphate esters are added to furniture, electronics, textiles and building materials to reduce fire risk or improve flexibility. - The chemicals are mixed into products rather than chemically bound, so they can leach into air, dust and water over time. - In the marine food web, tri-n-propyl phosphate, or TPP, was the dominant compound, with a median concentration of 147 ng/g lipid weight. - In the freshwater system, tris(2-chloroethyl) phosphate, or TCEP, was the most abundant compound, reaching 266 ng/g lipid weight. - All eight organophosphate esters showed biodilution in Liaodong Bay, meaning concentrations dropped at higher trophic levels. - TCEP biomagnified in the Songhua River, with a trophic magnification factor of 1.75. - Freshwater phytoplankton were especially strong accumulators, with bioaccumulation factors above the commonly used threshold of 3.7 for five organophosphate esters. - Compounds with intermediate hydrophobicity, measured as log Kₒw between 2.5 and 5, were most readily taken up. - Salinity, pH and dissolved organic carbon each helped shape the different accumulation patterns. - The study found non-cancer risks from eating seafood and river fish stayed low for all compounds. - Cancer risk was more concerning for TCEP in the Songhua River, where incremental lifetime cancer risk ranged from 10⁻⁶ to 10⁻⁴ in most organisms.

Between the lines: - The results challenge the assumption that a chemical’s behavior in one aquatic environment can be applied to another. - Marine-based risk models may underestimate exposure in freshwater systems where conditions favor accumulation. - The authors said TCEP was the biggest surprise because it diluted in the marine web but built up in the freshwater web. - The study also reinforces that salinity and dissolved organic carbon are not background variables; they can change whether a pollutant accumulates or dissipates.

What's next: - Regulators may need ecosystem-specific screening for organophosphate esters instead of relying on one-size-fits-all assessments. - Freshwater fish monitoring may need to prioritize TCEP and similar chemicals with biomagnification potential. - The findings point to a broader need for cross-ecosystem comparisons of persistent contaminants before setting health guidance.

The bottom line: - TCEP behaves like two different chemicals depending on whether it is in a river or the ocean, and that difference could matter for environmental and human health risk.