Industrial Boom Leaves Toxic Metal Fingerprint in Bangladesh Coastal Soils

Along the southeastern coastline of Bangladesh, where the Bay of Bengal meets one of the country’s fastest-growing industrial corridors, the soil itself has become a chemical archive of rapid development. A new study of the Mirsarai Export Processing Zone, published in Discover Geoscience, reports that twelve trace elements measured in surface soils show significant enrichment over natural background levels for all but iron, painting a picture of widespread, industrially driven contamination in a region that was largely undeveloped only a decade ago. The research, led by Md. Shazzadur Rahman of the University of Rajshahi and the Bangladesh Council of Scientific and Industrial Research, is the first comprehensive post-development assessment of soil quality in the zone, and its findings carry uncomfortable implications for the millions of people living near export processing zones across South Asia.

The team collected soil samples from thirteen sites inside and around the Mirsarai zone, taking triplicate samples from the top ten centimeters of the surface layer with stainless-steel spades. After air-drying, oven-drying at 110 degrees Celsius, homogenization, and sieving through a two-millimeter nylon mesh, the samples were digested with a combination of nitric and perchloric acids and analyzed by inductively coupled plasma mass spectrometry at BCSIR laboratories in Dhaka. Quality control was rigorous: certified reference materials from the National Institute of Standards and Technology, including NIST CRM 2709a and 2710a San Joaquin Soil, were digested and analyzed in triplicate with each batch, metal recoveries fell within 90 to 110 percent, and replicate precision stayed below five percent relative standard deviation. Calibration curves for every element exceeded a linearity coefficient of 0.999.

The concentrations the instrument returned were striking. Arsenic averaged 22.48 milligrams per kilogram, selenium 6.01, lead 69.88, cobalt 97.80, chromium 234.48, copper 157.23, manganese 3460.11, nickel 250.34, and zinc 476.83 milligrams per kilogram. Concentrations of arsenic, nickel, chromium, cadmium, and lead were nearly three times higher than guideline values set by the International Atomic Energy Agency and GESAMP, the joint group of experts on the scientific aspects of marine environmental protection. Compared with other Bangladeshi industrial areas, including the Dhaka Export Processing Zone, the Chittagong ship-breaking area, and the Chittagong port, Mirsarai’s soils were substantially more contaminated in chromium, copper, nickel, zinc, and manganese, and exceeded levels reported from industrial sites in Pakistan, southern India, West Bengal, and China, often by factors of two to ten.

To translate raw concentrations into a contamination verdict, the researchers deployed a battery of pollution indices. The geoaccumulation index, contamination factor, enrichment factor normalized to iron, toxic units, the pollution load index, and the Nemerow integrated pollution index each told part of the story, and together they converged on a consistent conclusion. Every site exceeded the pollution load index threshold of 1, with the worst site scoring 4.30. Every Nemerow index surpassed the acceptable limit of 3, peaking at 138.56. Enrichment factors were extreme: selenium reached 1098.88 relative to the crustal baseline, arsenic 133.67, manganese 58.07, zinc 64.06, and cobalt 50.85, values that by convention indicate overwhelmingly non-crustal, that is anthropogenic, origins. Iron alone, used as the normalization reference, remained essentially uncontaminated with a contamination factor of 0.11.

Spatial mapping using inverse distance weighting revealed that contamination is anything but uniform. Arsenic, iron, manganese, and chromium concentrated in the central and southeastern parts of the zone, while cadmium and mercury accumulated in the central and northwestern sectors. The central region emerged as the most contaminated overall, a pattern the authors attribute to localized industrial discharge stacking multiple pollutant sources on top of one another. The soils themselves amplify the risk: neutral to slightly alkaline pH, high electrical conductivity of 17 to 23 decisiemens per meter driven by saline intrusion, low to moderate organic matter, and sandy loam to clay loam textures all govern how strongly these elements are retained and how readily they become mobile and bioavailable.

Tracing the pollution to its origins required multivariate statistics. Pearson correlation analysis showed iron and manganese locked together with a correlation coefficient approaching unity, alongside strong associations of iron with cobalt, chromium, copper, and lead, a signature of natural iron-manganese oxyhydroxide scavenging overlaid by industrial input. Tight metal clusters, such as cobalt with nickel at 0.971 and lead with zinc at 0.949, pointed to shared industrial sources. Principal component analysis extracted three components explaining 89.62 percent of total variance: the first, accounting for 62.56 percent, combined lithogenic material with heavy industry fingerprints of iron, manganese, cobalt, chromium, copper, lead, nickel, zinc, and arsenic; the second, at 17.55 percent, isolated selenium and mercury, implicating combustion, chemical production, and atmospheric deposition from industrial boilers; the third captured cadmium alone, linked to electroplating, battery waste, and pigment manufacturing.

The study’s most innovative contribution is a Source-Pathway-Receptor model that explicitly links specific industries to specific contaminants and exposure routes. Textile dyeing, leather processing, electroplating, battery manufacturing, metal finishing, and electronics operations were identified as the principal sources of arsenic, chromium, copper, zinc, lead, cadmium, nickel, and cobalt. In a country where export processing zones often lack effective wastewater treatment infrastructure, untreated or minimally treated effluents flow into nearby water bodies and gradually load the underlying soils. Because trace elements are persistent and non-biodegradable, the soil functions as a long-term sink, and under shifting physical and chemical conditions these stored pollutants can be remobilized into the wider Bay of Bengal environment, where benthic organisms readily take up bioavailable metal forms.

Ecological risk assessment identified selenium as the dominant threat, with an ecological risk factor of 601.40, far above the very-high-risk classification, followed by arsenic at 149.85 and mercury at 106.45. Every one of the thirteen sampling sites exceeded a potential ecological risk index of 600, with the worst site scoring 1501.39. The human health picture was more alarming still. Using the United States Environmental Protection Agency framework across ingestion, dermal, and inhalation pathways, the team found that cobalt posed the highest non-carcinogenic risk to children, with a hazard index of 8.54, followed by manganese at 2.62, chromium at 2.05, and arsenic at 1.45, all above the safety threshold of 1. For adults, only cobalt exceeded the threshold, at 2.25. Children face roughly 3.1-fold higher carcinogenic risk than adults, driven by their higher soil ingestion rates, lower body weight, and greater dermal absorption, with nickel, chromium, and arsenic all surpassing the acceptable lifetime cancer risk limit of 1.0 times ten to the minus four.

To move beyond single-point estimates, the researchers ran a Monte Carlo simulation with 100,000 iterations at a 95 percent confidence level. The probabilistic analysis confirmed a mean total carcinogenic risk of 1.58 times ten to the minus four for children, exceeding even the upper bound of the generally acceptable range, with ingested chromium alone contributing more than 70 percent of the total. The fifth to ninety-fifth percentile range for children spanned 1.30 to 1.90 times ten to the minus four, indicating the risk is consistently high rather than a statistical outlier. For adults, the mean risk of 4.24 times ten to the minus four was about 3.7 times lower, though worst-case percentiles still crossed the unacceptable threshold, and inhalation gained relative importance for adults, who breathe roughly twenty cubic meters of air daily compared with six for children. Sensitivity analysis identified body weight, exposure frequency, and trace metal concentration as the most influential parameters.

The authors acknowledge that uncertainties arise from analytical variability, spatial heterogeneity, and default exposure assumptions that may not capture population-specific sensitivities, but they argue the USEPA-based framework is conservative and widely accepted. Their conclusion is unambiguous: the Mirsarai Export Processing Zone is a significant multi-metal pollution hotspot, and without strict industrial effluent control, improved waste management, and continuous soil monitoring, the ecological and public health costs of Bangladesh’s industrial ascent will keep compounding in the very ground beneath it. As export processing zones proliferate across the developing world, the Mirsarai data offer a sobering template for what happens when economic growth outpaces environmental safeguards, and a quantitative baseline for the remediation that must now follow.

Subject of Research: Trace element contamination, sources, and health risks in soils of an industrial export processing zone on the coast of Bangladesh

Article Title: Geochemistry, sources, human health and ecological risk of trace elements in soil from the Mirsarai export processing zone, southeastern coast of Bangladesh

Article References: Rahman, M. S., Uddin, M. R., Moniruzzaman, M., Mostafa, M. G., Takeya, L. A., Rahman, M. A., Hossen, M. N., Ashikuzzaman, M., & Abid, A. A. (2026). Geochemistry, sources, human health and ecological risk of trace elements in soil from the Mirsarai export processing zone, southeastern coast of Bangladesh. Discover Geoscience, 4(1), Article 333. https://doi.org/10.1007/s44288-026-00696-y

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00696-y

Keywords: trace elements, soil contamination, export processing zone, Bangladesh, heavy metals, health risk assessment, ecological risk, Monte Carlo simulation, source apportionment, ICP-MS, industrial pollution, Bay of Bengal