The 2021 tuberculosis (TB) preventive treatment guidelines in India included silicosis as a screening group, yet latent TB infection (LTBI) testing for silica-dust-exposed individuals is underemphasized. Focusing on an estimated 52 million silica-dust-exposed workers, particularly agate-stone workers in Khambhat, Gujarat, our study aims to estimate LTBI prevalence, identify predictors, and gather insights from TB and silicosis experts. Employing a sequential explanatory mixed-methods approach, a cross-sectional study involved 463 agate-stone workers aged ≥ 20 years in Khambhat, using IGRA kits for LTBI testing. In-depth interviews with experts complemented quantitative findings. Among agate-stone workers, 58% tested positive for LTBI, with predictors including longer exposure, type of work, and BCG vaccination. Our findings reveal a nearly double burden of LTBI compared to the general population, particularly in occupations with higher silica dust exposure. Experts advocate for including silica-dust-exposed individuals in high-risk groups for LTBI testing, exploring cost-effective alternatives like improved skin sensitivity tests, and shorter TB preventive treatment regimens to enhance compliance. Future research should explore upfront TB preventive treatment for silica-dust-exposed individuals with high LTBI prevalence and optimal exposure duration. This study underscores the urgent need for policy changes and innovative approaches to TB prevention among silica-dust-exposed populations, impacting global occupational health strategies.

OBJECTIVE: Agate workers are chronically exposed to silica dust generated from agate grinding, which makes them susceptible to silicosis. In the absence of diagnosis at an early stage, the workers continue to be exposed to silica dust until the development of silicosis. The present study was undertaken to investigate total lactate dehydrogenase (LDH) activity in blood samples of silica-exposed agate workers as a non-invasive way to measure silica-induced toxicity.
METHODS: Blood samples were collected from agate workers and control subjects. Total LDH activity was measured in the blood plasma and blood cells of agate workers and non-exposed (control) subjects using sodium pyruvate as a substrate. The reduction of pyruvate to L-lactate with the concurrent oxidation of nicotinamide adenine dinucleotide (NADH) during the assay was monitored by change in absorbance (or optical density (OD)) at 340 nm at the fixed interval of 10 min. The ratio of LDH activity (blood plasma/blood cells) in the blood samples was calculated as a measure to detect cytotoxicity in exposed workers.
RESULTS: The LDH activity in blood plasma samples of exposed workers was found to increase about 25 times, while the activity in the blood cells of silica-exposed agate workers was reduced to 10% of control subjects. The ratio of LDH activity (blood plasma/cells) was found to be 6.6 in the silica-exposed agate workers, while it was 0.02 in control (non-exposed) subjects.
CONCLUSIONS: This study proposes that total LDH activity and the LDH ratio (plasma/cells), along with occupational exposure history, are markers for silica exposure-induced toxicity in agate workers.