Assessment of Silica Dust Exposure and Pulmonary Impairments Among Marble and Granite Workers in Islamabad, Pakistan

Abstract

Silica exposure in marble and granite quarries poses a serious threat to human health and the environment in Islamabad, Pakistan. This study aims to assess the prevalence of pulmonary impairments among quarry workers and analyze the concentrations of PM2.5 and PM10 particles comprising silica in marble and granite factories. The study uses a cross-sectional research approach and combines elemental analysis, spirometry evaluation, and low-volume air sampling to measure environmental and human health parameters. Using a low-volume sampler, samples of particulate matter (PM2.5 and PM10) were collected from major processing units i.e. wet sawing, polishing, and sealing, kitchen countertop fabrication and cluster (where all the processes were being done simultaneously and their silica and heavy metal content were examined using ICP-MS and SEM-EDX techniques. Results showed that silica concentrations in PM10 and PM2.5 reached 133.9 µg/m³ and 141.9 µg/m³ respectively in the wet sawing unit, both exceeding the NIOSH occupational exposure limit (50 µg/m³). SEM-EDX analysis revealed irregular quartz-rich particulates with angular morphology and sharp edges, indicating high pulmonary deposition potential. Health risk assessments found the lifetime cancer risk (LTCR) for chromium in PM₁₀ up to 3.9 × 10⁻³, far exceeding the USEPA acceptable limit (<1 × 10⁻⁶). For silica (Si), the LTCR ranged from 2.1 × 10⁻⁴ to 2.7 × 10⁻⁴ across all processing units, also above the USEPA’s tolerable threshold, indicating a significant carcinogenic potential. In terms of non-cancerous risk, the hazard quotient (HQ) for manganese reached 9,160 and iron 4,890, both in PM₁₀, signaling extremely elevated risk. For silica, HQ values across units ranged from 9.7 to 12.3, consistently above the acceptable limit of 1, confirming that silica exposure alone poses a substantial chronic inhalation risk to workers. All tested units demonstrated HQ > 1 for multiple elements, underlining unacceptable exposure levels throughout the industry. Questionnaire analysis showed that 52% of workers reported persistent cough, 49% experienced shortness of breath, and 41% complained of wheezing. Additionally, 36% noted limitations in physical activity due to breathing difficulty, reflecting a strong symptom burden. Concurrently, spirometry on male workers aged 18 to 60 demonstrated a high prevalence of pulmonary abnormalities, including restrictive and obstructive lung function patterns. Statistical analysis revealed a significant relationship between dust exposure levels and reduced lung function indicators, including FEV1 and FVC.Based on the findings, the study recommends targeted interventions in Islamabad's marble and granite quarries, such as the installation of localised dust suppression systems in high-risk zones, the provision and mandatory use of silica-rated personal protective equipment (PPE), and regular medical surveillance with spirometry assessments for all quarry workers. Furthermore, stringent enforcement of water-based dust control in wet cutting and grinding activities, as well as awareness training for workers and supervisors on silica dangers and safe practices, is critical to reducing health risks and improving occupational safety standards in the region.