Airborne lead dominates the exposure picture in Salafchegan’s industrial corridor
Industrial zones can push lead into both air and soil, but the two compartments do not always behave in the same way. In the Salafchegan Special Economic Zone in Iran, geostatistical sampling showed a striking separation between the atmosphere and surface soil: mean airborne lead reached 12.88 µg/m³, while mean soil lead measured 3.05 mg/kg. The pattern suggests a setting in which lead is being emitted, redistributed, and repeatedly lifted back into the air rather than settling quietly into the ground.
The environmental context matters here. Semi-arid terrain, strong winds, and industrial activity create conditions in which contaminated dust can stay mobile. In this zone, high wind energy appears to limit persistent accumulation in surface soil and instead favors resuspension of deposited material. In practical terms, that means the hazard is not locked in one compartment; it keeps cycling through the air that workers and nearby residents breathe.
Spatial heterogeneity mapped with kriging and inverse distance weighting
Fifty-six sampling stations formed the backbone of the assessment, and the spatial analysis did not produce a flat or uniform contamination field. The ordinary kriging maps showed marked heterogeneity, with a coefficient of variation of 58.36%, and identified industrial hotspots across the zone. Such variability is important because a single site average can conceal local pockets of exposure that are far more relevant to day-to-day inhalation risk.
Investigators compared Ordinary Kriging with Inverse Distance Weighting during cross-validation. Both methods generated comparable prediction errors, yet ordinary kriging was selected for the final mapping because it adds two advantages that matter in environmental surveillance: it estimates prediction uncertainty through kriging variance and it explicitly accounts for spatial autocorrelation. For a pollutant such as lead, which rarely distributes itself randomly, a method that respects spatial structure provides a more faithful map of likely exposure.
A short sentence captures the core finding: the industrial zone was not uniformly contaminated, but unevenly burdened.
Wind-driven resuspension may be keeping lead in circulation
Lead does not behave like a gas, yet the study’s results point to a circulation pattern driven by dust and wind rather than simple settling. The reported disparity between atmospheric and soil concentrations was attributed to the region’s high wind energy, described by a DPt value of 936. In a semi-arid industrial area, that kind of mechanical energy can lift contaminated particulates from roads, open ground, and industrial surfaces back into the air, blurring the boundary between deposition and re-emission.
That mechanism has direct implications for exposure control. If dust resuspension is maintaining elevated airborne levels, then soil remediation alone will not fully address the problem. Air quality management has to account for road dust, uncovered surfaces, industrial emissions, and the physical forces that keep particles suspended long after they are released.
Children faced the higher modeled burden despite hazard indices below 1
The risk assessment moved beyond concentration mapping and into probabilistic health estimation. Using a Monte Carlo simulation with 10,000 iterations, the analysis calculated total non-carcinogenic risk and found it remained below the permissible threshold, with Hazard Index values below 1. Even so, the modeled burden was not evenly distributed across age groups. Children consistently showed greater vulnerability than adults to lead exposure.
That difference is biologically plausible even when the overall index stays below the usual cutoff. Children breathe more air relative to body size, spend more time close to ground-level dust, and are more likely to ingest contaminated particles through hand-to-mouth behavior. Lead exposure in early life also carries a lower margin for error because developing nervous systems are more sensitive to toxic metals. A risk estimate below 1 does not erase those differences; it simply means the aggregate non-carcinogenic burden did not cross the study’s chosen benchmark.
Why the map matters for monitoring policy
The study’s real value lies in how it links environmental chemistry to local conditions. Lead contamination did not appear as a static soil problem; it behaved as a climate-shaped exposure problem. In an industrial zone with strong winds, the atmosphere becomes the dominant compartment for concern, and the most informative surveillance strategy is one that tracks both airborne particles and surface deposits over time.
Regular monitoring around industrial sites is therefore not a generic recommendation but a direct response to the spatial pattern observed here. Hotspots need targeted attention, and environmental control measures should be designed around dust suppression, source control, and repeated sampling in zones where industrial activity and wind exposure overlap. The maps also show why averaging data across an entire site can be misleading: the places most likely to matter clinically and operationally may be small, localized, and easy to miss without spatial modeling.
Even with a non-carcinogenic hazard index below threshold, the exposure profile remains relevant for public health planning. Lead is a cumulative toxicant, and its behavior in a semi-arid industrial setting can change quickly with weather, disturbance, and land use. The unresolved issue is not whether the metal is present, but how effectively local control measures can interrupt the dust cycle that keeps it moving through air and settlement zones.