The workers are regularly exposed to silica dust as the jewellery and decorative items are made by polishing, chipping, and drilling agate stones, which contain more than 60 per cent free silica.

Inhaling silica dust impairs the immune system and increases the risk of developing tuberculosis.

The findings, published in Nature's Scientific Reports journal, showed that the "burden of latent tuberculosis infection (LTBI) in India's agate stone workers is nearly double the national average (31 per cent)".

About 58 per cent were found to have LTBI — higher than the 41 per cent reported for high-risk groups.

Moreover, those indulged in polishing and chipping stones, which generate more dust and finer particles, showed higher LTBI positivity compared with those drilling.

Workers' low income, poor nutrition, and overcrowded living conditions increase their susceptibility to LTBI, the study showed.