‘Invisible’ silicosis: Detection kits now on radar

Ahmedabad: A lesser known, hardly recognized, and often overlooked early stage of the deadly silicosis called the “subradiological silicosis” or invisible silicosis (radiologically) is now demanding urgent attention from health experts and policy makers of the country. Silicosis is a lung disease caused primarily by inhaling silica dust.

Scientists at ICMR-NIOH (Indian Council of Medical Research-National Institute of Occupational Health) have argued for the first time that if silicosis is detected at the subradiological stage, major silico-tuberculosis and lung cancer occurrences can be prevented. These diseases afflict lakhs of citizens in India.

Subradiological silicosis is silicosis detectable by the pathological examination of the lung tissue but is not visible radiologically, that is, on x-rays.

Scientists at NIOH, based in Ahmedabad, are now in the final stages of obtaining new detection kits for subradiological silicosis from Indian manufacturers for mass use. The scientists had found in an earlier study of silicosis that a certain level of the protein released from the lungs into our bloodstream called “CC16” has the potential to indicate silicosis at an early stage. But now, NIOH says, this same protein has been found to indicate subradiological or invisible silicosis and silico-tuberculosis as well. NIOH scientists say that an intervention at this stage can help save lakhs of Indians who are vulnerable to contracting tuberculosis or lung cancer.

“The kits can be made available at taluka or village level health centres for periodic screening of workers of stone quarries, mines, or relevant industries,” said ICMR-NIOH director Dr Kamalesh Sarkar. “The kit detects the level of serum CC16 and if its value remains between 9 and 12 nanogram/millilitres, then it is an indicator of subradiological stage of silicosis.”

Sarkar said that subradiological silicosis is an important risk factor for tuberculosis. Recently, the South African mining authority had inquired about the availability of CC16 kits in the Indian market from Dr Sarkar for screening their 3.85 lakh ex-miners. “Their study showed that of every 100 workers suffering from silicosis, 57 had subradiological silicosis and 43 were diagnosed with x-rays,” said Sarkar.

Sarkar added: “People with less than 10 years of exposure usually suffer from subradiological silicosis that can be detected only by the pathological examination of the lung tissue.” He went on to say: “So, eliminating tuberculosis requires focusing on both visible and invisible silicosis. India has a huge burden of all forms of silicosis.”

Recently, scientists in South Africa had studied silicosis and associated tuberculosis among miners and had found that subradiological silicotic workers had more than twice the risk of contracting lung tuberculosis. The risk continues even after leaving their jobs, when silica dust exposure ends. “India needs to revisit its silicosis compensation system based on chest x-ray as subradiological silicosis is also an occupational disease with no x-ray based evidence,” said Sarkar. If this is missed due to ignorance, a vital opportunity to prevent silicosis and tuberculosis will be lost.