Industrial Soils in Iran Carry a Hidden Cancer Risk From Nickel, Study Warns

In the sprawling industrial estates that ring the city of Neyshabur in northeastern Iran, the ground beneath factories, warehouses, and truck routes has been quietly accumulating a chemical record of decades of industrial activity. A new study published in the journal Environmental Geochemistry and Health has now decoded that record, and its findings carry a warning that extends well beyond the city limits. Researchers led by Mohammad Hassanabadi and Safoura Javan of the Workplace Health Research Center at Neyshabur University of Medical Sciences measured the concentrations, mapped the spatial distributions, and calculated the health risks of heavy metals in soils surrounding four industrial estates. Their conclusion is stark: while most metals remain within acceptable limits, nickel concentrations exceed guideline values, chromium levels approach the recommended threshold, and the carcinogenic risk associated with nickel surpasses the safety standard set by the United States Environmental Protection Agency in two of the four estates studied.

The research team focused on the estates of Attar, Miyanjolgeh, and two other industrial zones in the Neyshabur region, an area whose rapid industrial growth has gradually altered the chemical makeup of surrounding soils. Soil samples collected around these estates were analyzed for a suite of heavy metals, including nickel, chromium, cadmium, iron, and manganese. The analytical strategy combined classical geochemical assessment with spatial mapping and directional analysis, allowing the researchers to distinguish between metals that originate from the natural geological background and those whose patterns betray an industrial or agricultural fingerprint. This distinction matters enormously, because regulatory decisions about remediation and land use hinge on knowing whether elevated concentrations reflect human activity or simply the local bedrock.

The results revealed a striking contrast between different metals. Iron and manganese displayed stable, predictable patterns consistent with their natural lithogenic origin, varying little across the study area and showing no clear relationship to the industrial estates. Nickel and chromium, by contrast, exhibited pronounced spatial heterogeneity, with concentrations fluctuating sharply over short distances. The researchers interpret this patchiness as evidence of a dual origin: a naturally elevated geochemical background, common in regions with metal-rich parent rocks, superimposed on localized emissions from nearby industrial facilities. This combination makes nickel and chromium the two priority metals for environmental monitoring and health risk evaluation in the region, standing out as more consequential than the other elements measured.

Cadmium told a different story altogether. Rather than peaking near the industrial estates, cadmium concentrations increased with distance from the estates themselves, a pattern the researchers attribute to a blend of urban and agricultural sources. Cadmium is a well-known contaminant of phosphate fertilizers and is also associated with urban runoff and traffic-related deposition, so its distribution suggests that the agricultural lands and settlements surrounding the industrial zones contribute as much to soil cadmium as the factories do. This finding complicates the conventional assumption that industrial estates are the sole or even dominant sources of soil metal contamination in mixed land-use landscapes, and it underscores the need for source apportionment that considers the full mosaic of human activities.

Perhaps the most visually compelling evidence came from the directional analysis. When the researchers examined how concentrations varied along different compass bearings, they discovered peaks in metal levels along the north–south axis close to several of the estates. This orientation is unlikely to be a coincidence. It aligns with the layout of industrial facilities, the direction of major transportation corridors, and the prevailing pathways of atmospheric pollutant transport. In other words, the geometry of industrialization itself, from factory siting to truck traffic to wind-driven dispersal of dust and emissions, appears to be imprinted on the soil chemistry. Such directional signatures offer a powerful, low-cost tool for identifying pollution pathways and for positioning future monitoring stations where they will capture the most meaningful data.

With the spatial patterns established, the team turned to the central question: what do these concentrations mean for human health? Using a standard health risk assessment framework, they evaluated both non-carcinogenic and carcinogenic risks for adults and children, considering the principal exposure routes of soil ingestion, inhalation, and dermal contact. The non-carcinogenic hazard results were reassuring. For both adults and children, the hazard indices remained within safe limits, indicating that the measured levels of metals in the soils are unlikely to cause adverse non-cancer health effects such as organ damage or developmental toxicity through routine environmental exposure.

The carcinogenic risk calculations, however, delivered the study’s most consequential finding. Nickel, acting chiefly through the ingestion pathway, produced a lifetime cancer risk that surpassed the USEPA’s acceptable threshold in the Attar and Miyanjolgeh estates. Under USEPA guidance, a carcinogenic risk value above the regulatory range suggests that the probability of developing cancer over a lifetime of exposure exceeds what is considered tolerable for the general population. The fact that ingestion, rather than inhalation, emerged as the dominant pathway highlights a particular vulnerability: soil particles enter the body through hand-to-mouth contact, consumption of insufficiently washed produce, and the general incidental ingestion of dust, a route that is especially significant for children who play in contaminated soils.

The researchers emphasize that even modest levels of pollution can translate into long-term health burdens when exposure persists over decades. Nickel compounds are classified as human carcinogens in certain forms, and chronic exposure has been linked to respiratory cancers and other adverse outcomes in occupational settings. The Neyshabur findings suggest that environmental exposure around industrial estates, at concentrations that might appear unremarkable in a single soil sample, can accumulate into a meaningful population-level risk when integrated across a lifetime. This is the essence of the integrated risk assessment approach the study champions: rather than evaluating each metal or pathway in isolation, it combines concentration data, spatial analysis, exposure modeling, and regulatory benchmarks into a single coherent picture of public health vulnerability.

The study also carries important implications for environmental management in Neyshabur and for the many rapidly industrializing regions it resembles. Because nickel and chromium show both natural and industrial contributions, the authors argue that monitoring programs must account for the local geochemical background before attributing exceedances solely to industrial emissions. At the same time, the directional concentration peaks provide actionable intelligence: pollution control efforts, dust suppression measures, and land-use restrictions can be targeted along the identified north–south corridors and around the specific estates where carcinogenic risk is highest. For cadmium, the distance-related gradient points toward agricultural best practices, including fertilizer management, as a complementary lever for reducing soil contamination.

The research was conducted by a team from Neyshabur University of Medical Sciences and Shiraz University of Medical Sciences, with ethical approval under code IR.NUMS.REC.1403.058, and the underlying data are available within the article and its supplementary materials. Its publication comes amid a growing body of work documenting heavy metal contamination in Iranian soils, from urban centers like Isfahan and Yazd to industrial complexes in Zanjan and Arak, and it adds a rigorous spatial and risk-based dimension to that literature. For the residents of Neyshabur, the message is measured but clear: the non-cancer risks from industrial soil pollution remain under control, but the nickel-driven cancer risk near Attar and Miyanjolgeh demands sustained monitoring, targeted intervention, and a management framework that treats soil not as an inert backdrop to industrial growth, but as an active medium through which pollution reaches the human body.

Subject of Research: Heavy metal soil pollution and human health risk assessment around industrial estates in Neyshabur, Iran

Article Title: Integrated health risk assessment and management of heavy metal pollution in industrial estates of Neyshabur, Iran

Article References: Hassanabadi, M., Marufi, N., YazdanDoust, M., Mehralian, M., Rahimimoghadam, S., & Javan, S. (2026). Integrated health risk assessment and management of heavy metal pollution in industrial estates of Neyshabur, Iran. Environmental Geochemistry and Health, 48(15), Article 604. https://doi.org/10.1007/s10653-026-03494-0

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03494-0

Keywords: heavy metals, soil contamination, nickel, chromium, cadmium, health risk assessment, carcinogenic risk, industrial estates, Neyshabur, Iran, spatial analysis, environmental monitoring