Winter Air Turns Deadliest for Rajasthan’s Sandstone Carvers, Study Finds

In the dusty workshops of Rajasthan, where artisans coax intricate motifs out of blocks of Jodhpur sandstone, the air they breathe changes dramatically with the seasons. A new study from researchers at Malaviya National Institute of Technology Jaipur has now quantified that seasonal shift in unprecedented detail, and the numbers are sobering. Personal respirable dust exposure among carvers nearly tripled from spring to winter, rising from 1.00 milligrams per cubic meter in spring to 1.35 in summer and reaching 2.95 milligrams per cubic meter in winter. Because sandstone is rich in crystalline silica, dust of this kind carries a well-documented risk of silicosis, an incurable and often fatal scarring of the lungs. The findings, published in the journal Air Quality, Atmosphere & Health, suggest that the coldest months of the year, when many people assume outdoor pollution is the only concern, may in fact be the most dangerous time to stand at a carving bench.

The research team, led by Shubham Sharma with Nivedita Kaul and Sumit Khandelwal as co-authors, monitored a working sandstone-carving unit in Rajasthan across three seasons. Rather than relying on a single measurement technique, they combined two complementary approaches. Workers wore personal sampling equipment that captured the respirable fraction of dust, the particles small enough to penetrate deep into the lungs, over their shifts. At the same time, real-time instruments logged concentrations of particulate matter in four size classes: PM10, PM4, PM2.5 and PM1, corresponding to particles with aerodynamic diameters of ten, four, two-and-a-half and one micrometer or less. A 31-channel aerodynamic particle sizer resolved the full size distribution of the airborne dust, while concurrent meteorological measurements recorded the temperature, humidity and wind conditions surrounding each sampling campaign.

The seasonal contrast in fine-particle concentrations was striking. Winter recorded the highest particulate levels of any season, with mean PM2.5 concentrations reaching 109.3 micrograms per cubic meter at the workplace. To put that figure in context, it is roughly an order of magnitude above the annual guideline value recommended by the World Health Organization, and it represents the air in the immediate breathing zone of the artisans rather than a distant ambient monitor. The researchers attribute the winter spike to a combination of factors that converge during the cold months. Temperature inversions and stagnant air suppress the dispersion of dust away from the work area, lower humidity and cooler temperatures alter how particles remain suspended, and the enclosed or semi-enclosed nature of many carving workshops traps emissions close to the source.

Particle size matters as much as particle quantity, and here the study revealed a seasonal fingerprint in the dust itself. During winter, the size distributions showed enhanced accumulation of submicron particles, those smaller than one micrometer, which are the fraction most capable of reaching the deepest regions of the lung and even crossing into the bloodstream. In spring and summer, by contrast, the coarse mode of the distribution grew stronger, reflecting larger fragments that settle more quickly but can still irritate the upper airways. The ratios between size fractions told a consistent story: the contribution of PM1 relative to PM2.5 remained relatively stable across seasons, indicating that once particles are in the fine range, their internal composition shifts little, while the ratio of PM2.5 to PM4 varied more, marking the boundary where seasonal effects reshape the dust cloud.

One of the most technically interesting aspects of the work lies in how the team handled the statistics. The four PM fractions are nested within one another, meaning PM10 includes PM4, which includes PM2.5, which includes PM1. This nesting produces severe multicollinearity: correlations among the fractions exceeded 0.90, making it statistically treacherous to attribute effects to any single size class using ordinary regression. The researchers therefore applied principal component regression, a technique that first compresses the correlated particle-size and meteorological variables into a small set of uncorrelated components and then regresses the outcome on those components. The resulting models explained between 90.4 and 97.7 percent of the variation in PM1 concentrations, an unusually high degree of explanatory power for field exposure data.

The principal component analysis also showed that the drivers of fine-particle concentrations change with the calendar. Associations between PM1 levels and the particle-size and meteorological components varied from season to season, meaning that no single control strategy calibrated in one season can be assumed to work year-round. Strong correlations among all PM fractions pointed to a common source, the mechanical working of the stone itself, but meteorology determines how much of that source ends up in the breathing zone. In winter, the same grinding and chiseling that produces a manageable dust cloud in a breezy spring workshop instead accumulates into a dense, fine-particle haze that lingers around the artisan’s face for hours.

The health stakes of these measurements are not abstract. Sandstone from Rajasthan contains substantial crystalline silica, and inhaling respirable silica dust causes silicosis, a progressive disease for which there is no cure once fibrosis sets in. Studies cited by the authors document high prevalences of silicosis among stone carvers in Brazil, Thailand and Canada’s Nunavut territory, as well as among sandstone mine workers across Rajasthan itself. Indian surveys have reported respiratory symptoms, reduced spirometric readings and radiological abnormalities among stone-cutting workers, and Rajasthan’s own silicosis compensation program has disbursed grants for diagnosed cases and deaths. Previous work by the same research group examined respiratory deposition of particles in stone carving using real-time mass and number concentrations, and the new study extends that line of inquiry by adding the seasonal dimension and the full size-resolved picture.

What makes the findings actionable is their specificity. Because winter emerges as the season of peak exposure, dust-control interventions can be timed and intensified when they matter most. The literature on stone fabrication points to several engineering controls that have proven effective elsewhere: on-tool shrouds and local exhaust ventilation that capture dust at the point of generation, wet methods that suppress dust before it becomes airborne, and enclosure of grinding stations. The study’s seasonal size distributions offer a further clue for control design, since a system tuned to capture coarse particles in summer may underperform against the submicron accumulation mode that dominates in winter. Administrative measures, such as rotating workers away from grinding tasks during high-exposure periods and ensuring proper use of respiratory protection, can also be scheduled around the winter peak.

The authors are careful to frame the scope of their conclusions. The measurements come from a single sandstone-carving workplace monitored over three seasons, and they note that larger multi-site and longer-duration investigations are required to establish how broadly the seasonal patterns apply across the stone-carving sector. Rajasthan’s carving industry is vast and largely informal, ranging from heritage-restoration workshops to small units producing export-quality decorative stonework, and working conditions can differ substantially between sites. Nonetheless, the study provides something the sector has lacked: a seasonally resolved, size-resolved characterization of what carvers actually breathe, grounded in personal sampling rather than area monitors alone.

For the artisans of Rajasthan, the message embedded in the data is quietly urgent. The dust that glitters in a shaft of winter sunlight is not merely a nuisance but a precisely measurable hazard whose finest particles concentrate exactly when the weather conspires to keep them airborne and close. The study’s models, explaining more than ninety percent of the variance in fine-particle concentrations, demonstrate that this hazard is predictable, and what is predictable can be managed. As India’s natural stone industry faces growing scrutiny over labor conditions and occupational disease, research of this kind supplies the evidence base on which targeted regulation, engineering investment and worker protection can finally be built, season by season and micron by micron.

Subject of Research: Seasonal particulate matter exposure and particle size distribution among sandstone-carving workers in Rajasthan, India

Article Title: Seasonal variation in particulate emissions, particle size distribution, and worker exposure at a sandstone-carving workplace in Rajasthan

Article References: Sharma, S., Kaul, N., & Khandelwal, S. (2026). Seasonal variation in particulate emissions, particle size distribution, and worker exposure at a sandstone-carving workplace in Rajasthan. Air Quality, Atmosphere & Health, 19(10), Article 217. https://doi.org/10.1007/s11869-026-02110-5

Image Credits: AI Generated

DOI: 10.1007/s11869-026-02110-5

Keywords: particulate matter, respirable dust, silica exposure, silicosis, sandstone carving, occupational health, Rajasthan, PM2.5, particle size distribution, principal component regression, air quality, worker exposure