Occupational whole-body vibration exposure and low back pain: epidemiological insights from Indian coal mining

Objective To examine the association between whole-body vibration (WBV) exposure and self-reported low back pain among dumper operators, and to assess the epidemiological relevance of lumbar injury risk thresholds proposed in ISO 2631–5:2018. Methods A cross-sectional study was conducted among dumper operators (n = 304) from an opencast coal mine in India. Structured interviews were used to collect data on self-reported low-back pain (LBP), demographic characteristics, and work-related risk factors. WBV exposure was measured using tri-axial accelerometers placed on vehicle seats and cabin floors, following the guidelines of ISO 2631–5:2018. Biomechanical models were then applied to compute the risk of lumbar injury (RA) values across different levels of the lumbar spine. Logistic regression models were employed to examine associations between estimated RA values and self-reported LBP. In addition, classification models, namely Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis (QDA), Logistic Regression, and Gaussian Naive Bayes were evaluated to determine robust RA thresholds for predicting LBP. Results The 12-month prevalence of self-reported LBP was 37%, with RA values ranging from 0.27 to 0.93. Although 99.7% of participants were classified as low-risk by existing ISO thresholds (RA < 0.8), substantial LBP prevalence was observed. Logistic regression indicated significant associations between RA values, high physical workload, poor psychosocial work environment, and duration of WBV exposure with 12-month LBP (p < 0.05). LDA yielded the highest classification accuracy (71%) and identified an optimal RA threshold of 0.55 (95% CI 0.51–0.62), confirmed through bootstrapping and chi-square validation (OR = 3.20, p < 0.001). Conclusions The current RA thresholds defined in ISO 2631–5:2018 may underestimate the risk of lumbar injury in this occupational group. This study identifies and validates a refined RA threshold of 0.55, which demonstrates stronger alignment with epidemiological evidence from the field. These findings highlight the need to revisit and revise existing WBV exposure guidelines to better safeguard spinal health in mining environments.