The scale of the global plastic problem provides the backdrop. Humanity has manufactured more than 8 billion tons of plastic since 1950, and only about 9 percent has been recycled. Global production reached roughly 350 million tons in 2017, and projections warn that by 2050 the oceans could carry more plastic than fish by weight. Researchers classify plastic debris by size, from megaplastics larger than 50 centimeters down to microplastics between 1 micron and 5 millimeters and nanoplastics below 1 micron. Fibers, granules, fragments, and pellets are the most common microplastic forms in the environment. Because these particles are lightweight, winds and currents scatter them widely, and polymer density determines whether they float at the surface, drift through the water column, or settle into sediments. Studies estimate that between 4.8 and 12.7 million metric tons of plastic enter the ocean every year, and a 2017 analysis found that just five Asian countries accounted for 80 percent of mishandled plastic reaching the sea.

Bangladesh’s vulnerability stems from a combination of geography, economics, and governance. The country spans 148,460 square kilometers and is home to roughly 166 million people, with a plastic manufacturing sector that has expanded rapidly over the past two decades. An extensive network of inland canals, combined with weak waste management infrastructure, funnels plastic debris into rivers that ultimately drain into the Bay of Bengal. Recycling remains in its infancy, and disposal in open areas, riversides, and roadsides is common. Thin polyethylene bags remain popular because they are cheap and no affordable alternative has achieved wide adoption. The government banned polyethylene bags thinner than 55 micrometers in 2002 and mandated jute packaging in 2010, yet enforcement has been inconsistent, and the share of plastic in Dhaka’s landfills rose from 1.74 percent in 1992 to 6.5 percent in 2014.

The review’s technical inventory reveals the diversity of contamination. Across water, sediment, and biological samples, the most frequently detected polymers were polyethylene, polypropylene, polystyrene, polyamide, polyethylene terephthalate, polyvinyl chloride, high-density and low-density polyethylene, polyurethane, ethylene vinyl acetate, and acrylonitrile butadiene styrene. Particle sizes ranged from below 0.5 millimeters to 5 millimeters, and most particles were transparent or white, followed by black, blue, green, and a spectrum of other colors. Detection methods varied: most studies relied on Fourier Transform Infrared spectroscopy, some used Attenuated Total Reflectance-FTIR, and a few applied micro-FTIR, while stereomicroscopy and scanning electron microscopy supported imaging and sizing. Boxplot analyses in the review showed high variability in abundance across riverine, coastal, wastewater, and sediment samples, with coastal riverine sediments and agricultural soils amended with textile sludge among the most contaminated, and coastal fish showing elevated particle loads.

Perhaps the most alarming finding concerns the dinner table. The authors calculated the Estimated Daily Intake of microplastics using mean contaminant concentrations, national consumption rates, and an average adult body weight of 60 kilograms. With average fish consumption at 55 grams per day and salt intake at 9 grams per day, fish and salt emerged as the largest dietary contributors. Benchmarked against World Health Organization thresholds, dietary exposure in Bangladesh falls into the moderate to high-risk categories depending on the food item. The evidence extends beyond seafood: a Dhaka investigation found 343 plastic particles per kilogram in samples of five well-known and two off-brand sugars, mostly particles larger than 300 micrometers. Tea bags fared even worse, with an empty bag containing 477 microplastic particles and a filled bag 505, reportedly the highest levels recorded anywhere, underscoring how deeply the particles have penetrated everyday consumer products.

The ecological consequences are equally troubling. Microplastics adsorb heavy metals, pathogens, and polycyclic aromatic hydrocarbons, delivering toxic cargo to the organisms that swallow them. Aquatic animals suffer oxidative stress, reduced nutrient uptake, suffocation, internal abrasions, and impaired movement. Crustaceans are the most studied taxonomic group, followed by fish, mollusks, worms, echinoderms, and rotifers, organisms that occupy every tier of aquatic food webs. Filter-feeding mollusks are particularly efficient at accumulating particles and toxins, and because they are widely eaten by humans, they form a direct bridge between contaminated ecosystems and human diets. Laboratory work shows that microplastics accumulate in the digestive systems, gills, and stomachs of crabs and fish, damage genetic material in mussels, and cause immunotoxicity, neurotoxicity, and genotoxicity when particles carry adsorbed pollutants.

Polymer chemistry determines the specific hazards. PVC commonly contains phthalate plasticizers that can leach into the environment and disrupt endocrine function, contributing to reproductive toxicity and carcinogenicity. PET, ubiquitous in beverage packaging, is synthesized with antimony trioxide, leaving residual antimony that can migrate into stored liquids at elevated temperatures and pose oxidative and endocrine risks; PET also releases acetaldehyde, an irritant and potential carcinogen, when heated. PE, though relatively stable, fragments into micro- and nanoplastics that infiltrate dust, river sediments, and salt. Experiments on food-contact plastics heated to 70 degrees Celsius for two hours documented significant migration of lead, cadmium, mercury, chromium, and antimony, with PET samples exceeding European limits for antimony and chromium, a chronic exposure concern given how widely such packaging is used in Bangladesh.

For human health, the picture is one of persistence and accumulation. Microplastics have long half-lives in tissues, weakening immune cells and causing chronic inflammation, swelling, obstruction, and cell death. Oxidative stress, cytotoxicity, and tissue translocation have all been linked to exposure, and patients with inflammatory bowel disease show markedly higher microplastic burdens than the general population. Laboratory studies report disrupted mitochondrial membrane potential and reduced growth of Caco-2 intestinal cells after exposure. Particles can also act as carriers for microorganisms and can absorb or release chemicals from their matrices, meaning the dose, the polymer, and the adsorbed contaminants together dictate the harm.

The review closes with a roadmap rooted in existing law rather than new frameworks. The authors urge stricter enforcement of the 2023 amendment to the Plastic Waste Management Act, which formalized Extended Producer Responsibility, and propose an implementation roadmap including a dedicated regulatory body, a centralized registration and reporting platform, and Producer Responsibility Organizations to coordinate collection and recycling. They recommend scaling up jute-based packaging under the Mandatory Jute Packaging Act of 2010, which requires bulk commodities to be bagged in jute with penalties of up to one year in prison or a fine of roughly 409 US dollars, and promoting innovations such as the biodegradable jute cellulose Sonali Bag. Regionally coordinated research into polymer-specific toxicity, a national monitoring network, investment in recycling infrastructure, public education campaigns, and engagement in international plastic agreements complete the strategy. Compared with India and Pakistan, Bangladesh shows higher contamination in some matrices, though polymer types and sources are broadly similar across South Asia, making coordinated regional action essential to protect both ecosystems and public health.

Subject of Research: Microplastics contamination of freshwater and marine ecosystems and human dietary exposure in Bangladesh

Article Title: Microplastics contamination in freshwater and marine ecosystems, its impacts, and sustainable mitigation pathways in Bangladesh: a systematic review

Article References: Bhuyan, M. S., Nayan, A. H., Chowdhury, S., Chowdhury, S. U. M. B., Mondal, M. A. I., Islam, M. T., Karim, S. M. R., Meraj, G., & Abouleish, M. Y. (2025). Microplastics contamination in freshwater and marine ecosystems, its impacts, and sustainable mitigation pathways in Bangladesh: a systematic review. Discover Toxicology, 2(1), Article 14. https://doi.org/10.1007/s44339-025-00034-w

Image Credits: AI Generated

DOI: 10.1007/s44339-025-00034-w

Keywords: microplastics, Bangladesh, marine pollution, freshwater ecosystems, polyethylene, polypropylene, textile fibers, food contamination, human health, Extended Producer Responsibility, plastic waste management, PRISMA review

The core difficulty the researchers faced is philosophical as much as technical. Substitution, by its nature, can never be directly observed, because it only exists relative to a counterfactual: a version of history in which the substitute product was never produced, or produced at a different rate. Econometric studies can measure how markets responded to past price shocks, but they cannot answer the fundamental question of what would have happened had a product simply not existed. Life cycle assessment, the standard tool for comparing the environmental footprints of products, sidesteps the problem entirely by implicitly assuming perfect substitution—that one unit of product A displaces exactly one unit of product B—without ever measuring whether markets actually behave that way. Prior attempts to estimate displacement rates across various sectors have produced averages of roughly 40 to 60 percent, but with enormous variation and deep uncertainty rooted in the price elasticities that drive the calculations.

To break through this impasse, the team adopted system dynamics modeling, a simulation technique that represents a system’s behavior through feedback loops rather than static statistical correlations. Their model, named SubText, covers the three fiber categories that together account for more than 90 percent of the global fiber market: synthetic fibers, represented by polyester, which makes up 85 percent of synthetics; regenerated cellulosic fibers, represented by viscose, which accounts for 90 percent of that category; and cotton. The model is built on conventional microeconomic supply and demand equations, with demand responding to prices, income, and population, and supply responding to prices, feedstock availability, and feedstock costs. The crucial innovation lies in the inclusion of empirically estimated cross-price elasticities, which capture how strongly the consumption of one fiber responds to price changes in competing fibers—the higher the cross-price elasticity, the closer the substitutes.

The model’s architecture reflects the peculiar dynamics of the textile market. Balancing feedback loops link price to demand, price to supply, and price to profit to production capacity, generating the oscillating behavior typical of commodity markets. A single reinforcing loop transmits substitution effects between fiber pairs through their mutual prices. The researchers also introduced parameters rarely seen in market models, including an elasticity for the share of fast fashion, which serves as a proxy for a production strategy emphasizing quantity over quality, and a supply constraint for cotton that reflects the fact that the land area devoted to cotton cultivation has remained nearly unchanged for decades. Supply in the model is pushed by feedstock availability: crude oil extraction for synthetics, cotton seed harvest for cotton, and pulpwood harvest for cellulosic fibers. Time delays of one to two quarters for supply adjustments and a 22-year average mill lifetime for capacity divestments complete the picture of a market that responds sluggishly and asymmetrically to shocks.

The calibration process is where the approach earns its credibility. The researchers first assigned plausible parameter values from the literature and expert judgment, then ran a Powell optimization procedure with up to 5,000 iterations per variable to minimize the mismatch between modeled and statistical production and price data for the period 2004 to 2021. The model successfully reproduced long-term trends for all three fibers, smoothing out only the price peaks caused by extreme shocks. This calibration to historical data is what allows the method’s most novel step: recreating alternative histories. In scenarios P1 through P3, the researchers simulated the past development of the market with one of the three fibers effectively removed, comparing the resulting trajectories against the actual historical baseline. The difference between the two reveals, for the first time in a calibrated framework, how much the remaining fibers would have expanded had one competitor never grown.

The results are striking. The strongest substitution effect ran between regenerated cellulosic fibers and cotton: had viscose production not increased since 2004, 32 percent of that unrealized increase would have been compensated by higher cotton production, accompanied by a higher cotton price. In the forward-looking scenarios, a one-unit increase in cellulosic fiber production led to a 31 percent reduction in cotton production, closely matching the backward-looking estimate. Every other substitution pair produced far weaker effects, with a maximum of 8 percent displacement in supply-shock scenarios. Cotton proved the most responsive fiber overall, likely because it is the most commoditized of the three, while synthetics and cellulosics—still in the growth phase of their product life cycles—barely reacted to market shocks. Most tellingly, synthetics appeared almost completely isolated from the other fibers: changes in the production and price of cotton or viscose had essentially no effect on polyester output.

The environmental implications follow directly from these modest displacement rates. When the researchers recalculated displacement factors using their empirical rates instead of the conventional one-to-one assumption, the picture darkened considerably. Because a unit increase in one fiber displaces at most a third of a unit of another fiber, the majority of any supply increase simply adds to total consumption rather than replacing anything. When the researchers combined these empirical displacement rates with cradle-to-gate life cycle inventory data from ecoinvent, the global warming potential flipped from a net avoided emission to a net caused emission in all applicable substitution cases. The only exception was cellulosic fibers substituting for cotton, where the displacement rate was high enough to preserve avoided impacts in marine and terrestrial eutrophication, water use, and freshwater ecotoxicity. In every other case and most impact categories, expanding the supply of the supposedly greener fiber increased the sector’s overall environmental load.

The sensitivity analysis reinforced both the strengths and the limits of the method. The backward-looking scenarios proved remarkably stable, because any alternative parameterization would have degraded the fit between modeled and observed historical data, providing a built-in check against arbitrary assumptions. The forward-looking scenarios, by contrast, remained volatile, sensitive to the growth trajectory of fast fashion—which the researchers identified as the single largest source of variance—and prone to nonlinear responses when supply constraints or profitability thresholds were hit. Notably, without incorporating the fast fashion effect, the model’s baseline production would have fallen 47 percent short for synthetics, 45 percent for cellulosics, and 13 percent for cotton by 2021, suggesting that the explosive growth of cheap, disposable fashion, along with population and income growth, drives fiber production far more than any substitution dynamics do.

The authors are careful to frame their estimates as orders of magnitude rather than precise numbers, and to note that displacement rates are specific to the period, region, and market structure studied. Still, the broader message is hard to escape. For bioeconomy strategies that lean heavily on substitution as a pathway away from fossil resources, the textile case delivers a sobering verdict: the fossil-based synthetic fiber market is almost completely insulated from the production of alternative fibers, and cellulose-based fibers mostly substitute for each other rather than for polyester. Policies that encourage supply growth, such as subsidy schemes for novel fibers, are therefore unlikely to reduce the sector’s environmental footprint on their own. The researchers argue that alternative pathways—emission pricing, feedstock supply quotas, and measures targeting the overconsumption fueled by fast fashion—deserve far more attention, and that the alternative-history simulation method they pioneered should now be replicated across other sectors to test how widely these conclusions hold.

Subject of Research: Quantifying displacement rates and substitution dynamics among cotton, synthetic, and regenerated cellulosic textile fibers using system dynamics simulation

Article Title: Quantifying the unquantifiable: simulation of displacement rates among textile fibers

Article References: Hurmekoski, E., & Boiger, T. (2026). Quantifying the unquantifiable: simulation of displacement rates among textile fibers. Journal of Industrial Ecology. https://doi.org/10.1007/s44498-026-00161-6

Image Credits: AI Generated

DOI: 10.1007/s44498-026-00161-6

Keywords: substitution, displacement rate, textile fibers, system dynamics, life cycle assessment, fast fashion, cotton, viscose, polyester, counterfactual scenarios, industrial ecology, bioeconomy