Occupational exposure at petrol stations and red- green colour vision deficiency: a case-control study from Sudan

Occupational exposure to petroleum-derived organic solvents has been associated with acquired colour vision impairment. Evidence from low- and middle-income settings remains limited. To examine the association between occupational exposure to benzene/gasoline and red-green colour vision deficiency among petrol station workers in Khartoum State, Sudan. An analytical case-control study was conducted (February May 2022) at 19 petrol stations. Adult male participants were classified as cases (red-green colour vision deficiency) or controls (normal colour vision) using Ishihara plates (1999 edition). Exposure status (occupational petrol station work) and covariates were obtained via structured interviews. Visual acuity was assessed using the Landolt C Snellen chart. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated; multivariable logistic regression was used to adjust for age, smoking status, and work duration. A total of 176 participants (88 cases, 88 controls) were included. Occupational exposure was more frequent among cases than controls (64.8% vs. 47.7%). Exposure was associated with higher odds of red-green colour vision deficiency (adjusted OR ≈ 2.0; 95% CI 1.09–3.66; p = 0.02). Visual acuity was largely normal in both groups. Smoking was common but was not independently associated with colour vision deficiency after adjustment (p > 0.05). Occupational exposure at petrol stations was associated with red-green colour vision deficiency. Given the cross-sectional nature of exposure assessment and use of a screening tool for colour vision, findings should be interpreted as associative. Enhanced occupational health surveillance and eye safety practices are warranted.