Plastic Chemicals in Nigerian Streams and Fish Exceed Safe Health Limits, Study Warns

A new study from Nigerian researchers has delivered one of the most comprehensive assessments to date of plastic-derived chemicals in the country’s food and water systems, and the findings are stark. Water drawn from three streams that supply drinking water to rural communities, along with twenty-three species of fish collected from a major market, the artisanal fishery of the Lagos Lagoon, and the artisanal fishery of the Osun River, all carried burdens of plastic-related compounds high enough to raise serious health concerns. The research, led by Kehinde Oluwasiji Olorunfemi of the Federal University of Technology Akure and published in Environmental Science and Pollution Research, focused on three families of chemicals that are intimately tied to the modern plastics economy: phenolic compounds, phthalate esters, and polybrominated diphenyl ethers, commonly abbreviated as PBDEs.

These chemicals are not incidental contaminants. Phenolics such as bisphenol A and 4-nonylphenol are used in polycarbonate plastics, epoxy resins, and surfactants, and they are well-documented endocrine disruptors capable of interfering with hormone signaling at very low concentrations. Phthalates, including DEHP, DBP, BBP, and DnOP, are plasticizers added to polyvinyl chloride to make it flexible, and they are notorious for leaching out of products over time because they are not chemically bound to the polymer matrix. PBDEs are brominated flame retardants once widely incorporated into furniture foams, electronics, and textiles; although many formulations have been phased out in industrialized countries, they persist in the environment, bioaccumulate in fatty tissues, and continue to cycle through aquatic food webs. Because all three groups resist degradation and accumulate in organisms, rivers and fish become long-term reservoirs of human exposure.

The analytical approach was rigorous. Phenolic, phthalate, and PBDE compounds were extracted separately from the water and fish samples and quantified by gas chromatography coupled with mass spectrometry, the gold-standard technique for identifying and measuring trace organic pollutants in complex environmental matrices. Risk assessment then followed established models from the United States Environmental Protection Agency, allowing the team to translate measured concentrations into estimates of non-carcinogenic hazard and lifetime cancer risk for people who drink the water or eat the fish. This two-step design, combining high-sensitivity measurement with standardized risk modeling, is what gives the study its policy relevance, because it moves beyond simply reporting pollution levels to quantifying what those levels mean for human health.

The results for stream water were unambiguous. The hazard index, a metric that sums the risk contributions of all chemicals within a group and compares that total against a safe threshold of 1.0, exceeded the safe limit for phenolics, phthalates, and PBDEs in every stream sampled. In practical terms, this means the combined concentrations of these plastic-related chemicals in water that rural residents drink are high enough to plausibly induce non-carcinogenic health effects, which for endocrine-disrupting compounds can include developmental, reproductive, thyroid, and metabolic disturbances. No single chemical needed to reach a dangerous level on its own; the cumulative burden of each chemical family was sufficient to cross the line.

Cancer risk estimates for the water were equally troubling. The target cancer risk for DEHP, the most abundant and most studied phthalate, ranged from 0.003 to 0.007 in the stream waters. To appreciate the scale of that figure, regulatory agencies generally consider an acceptable lifetime cancer risk to lie between one in a million, expressed as 10 to the power of minus six, and an upper bound of 10 to the power of minus four. The measured values exceed even that upper bound, meaning the estimated cancer risk from drinking DEHP-contaminated water from these streams is orders of magnitude above what regulators would tolerate in a treated public water supply.

The fish samples told a similar story. Six individual chemicals, namely 4-nonylphenol, bisphenol A, DEHP, DBP, BBP, and DnOP, were detected in 100 percent of all fish samples analyzed, regardless of species or source. That complete detection frequency is significant because it indicates not isolated contamination events but pervasive, system-wide pollution of the aquatic environments from which Nigerians obtain a major protein source. Fish are particularly effective at accumulating these lipophilic compounds from water, sediment, and prey, so concentrations in tissue can far exceed those in the surrounding water, effectively concentrating the chemical burden that reaches the dinner plate.

PBDE contamination in the fish exceeded regulatory benchmarks by dramatic margins. The sum of six PBDE congeners, BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, and BDE-154, surpassed the Environmental Quality Standard value of 8.5 times 10 to the power of minus six by several orders of magnitude in fish from all three sources. Environmental Quality Standards are threshold values set to protect human consumers and ecosystems from harmful substances in biota, and exceeding one by such a wide margin signals that flame-retardant pollution has become deeply embedded in the food chain of the Lagos Lagoon and the Osun River. Prior research has shown that PBDEs in fish tissue can even serve as an indicator of broader plastic contamination in aquatic habitats, linking this finding to the wider problem of plastic waste mismanagement.

The cancer risk calculations for fish consumption may be the study’s most consequential finding. Target cancer risk from DEHP in the fish species ranged from 2 times 10 to the power of minus five to 1.5 times 10 to the power of minus three, again exceeding the 10 to the power of minus six safe threshold across the board, and in the worst cases by three orders of magnitude. The authors conclude that prolonged consumption of DEHP-contaminated fish from these sources poses a significant risk of cancer to exposed persons. For communities where fish from the Lagos Lagoon or the Osun River is a dietary staple, this transforms an everyday food choice into a chronic exposure pathway, and it suggests that the health costs of plastic pollution are being paid quietly, meal by meal, long before disease appears.

The study was funded by the Jennifer Ward Oppenheimer Research Grant 2021 and supported by Oppenheimer Generations Research and Conservation, with fish species identified by technologists at the Federal University of Technology Akure’s Department of Fisheries. Its publication comes amid mounting evidence of plastic pollution across Nigerian waterways, including recent work documenting excessive microplastic contamination in the Osun River and coastal communities of Ondo State. Together, these findings strengthen the case, made by some of the same researchers, that Nigeria should restrict single-use plastics and improve waste management. More immediately, the results argue for monitoring and public health interventions in the affected communities, where untreated stream water and locally caught fish remain daily necessities. As plastic production continues to grow globally, studies like this one make clear that the chemicals embedded in those materials do not stay in the products; they migrate into rivers, into fish, and ultimately into people.

Subject of Research: Human health risk assessment of plastic-related chemicals in Nigerian stream water and consumed fish

Article Title: Human health risk assessments of plastic-related compounds (phenolics, phthalates and PBDEs) in selected stream water and fish consumed in Nigeria

Article References: Olorunfemi, K. O., Olowolagba, O. J., Idowu, G. A., Oriji, A. Y., Isah, I. A., & Aiyesanmi, A. F. (2026). Human health risk assessments of plastic-related compounds (phenolics, phthalates and PBDEs) in selected stream water and fish consumed in Nigeria. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-026-38242-5

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38242-5

Keywords: plastic pollution, phthalates, phenolics, PBDEs, risk assessment, Nigeria, stream water, fish consumption, DEHP, endocrine disruptors, GC-MS, cancer risk