Dear Editor,
Silicosis is a respiratory disease that presents with cough, exertional dyspnea, chest pain, loss of appetite, weight loss, etc.[1] The disease is common among mine, quarry and construction workers, and is the most common occupational lung disease.[1,2,3,4] Jodhpur is the major sandstone belt of Rajasthan where there are more than 12,000 mines and quarries (DMRC’ 2002).[5]
Ever since the coronavirus pandemic started, it was cautioned that patients with overt or covert pre-existing lung diseases are more likely to develop COVID-19 infection, probably due to a compromised immune system and state of their health. The purpose of this study was to test this hypothesis among the residents living in five silicosis-prone villages and sub-urban areas of Jodhpur among mine and quarry workers working in the sandstone belt of Rajasthan.
Data of a total of 2,000 subjects who underwent COVID-19 testing in the sandstone belt of Jodhpur (Rajasthan) were obtained. The current study used a mixed method approach: Telephonic survey of those tested positive for COVID-19 (n = 167) among the residents living in the silicosis prone area. A cross section of the sandstone mine and quarry workers were used as comparison controls (n=110 workers). The study was done between June 2020 to December 2020 and the study was approved by Institute Ethics Committee.
Residents who underwent COVID-19 testing were interviewed regarding their COVID-19 positive status and diagnosis of silicosis (if anyone had). A total of 167 subjects (36.08 ± 16.75 years; M: F = 120:47, 154 adults) were found to be COVID-19 positive out of a population of 2000 mentioned above (8.35%). None of the 167 subjects, who tested positive out of the 2000 studied carried a diagnosis of silicosis.
To test the hypothesis that patients with diagnosis of silicosis are more likely to have COVID-19, a survey of mine workers was done on the ground, among a different subset of mine workers (n = 110; all adult males) regarding their COVID-19 status in which a total of 3 (2.72%) were found to be COVID-19 positive, based on laboratory reports. As per the data available in public domain, as of 11 January 2021, India's percent positivity was at 5.86%, that of Rajasthan was at 5.7%, and Jodhpur district and Fidusar area were at 5% and 4.1% respectively. No patient carrying COVID-19 positive status and a confirmed diagnosis of silicosis was identified in the current study.
None of the COVID-19 positive patients had a diagnosis of silicosis in the present study. Several factors could have accounted for lack of any patient with diagnosis of silicosis and COVID-19 positive status in the present findings. Social distancing is a proven intervention to check COVID-19 spread. High incidence of malaria in this area could have conferred protection against the development of COVID-19 (as per one of the stated hypotheses that malaria protects against COVID-19).[1] Apart from this, a potentially inherent lack of susceptibility of silicosis patients to COVID-19 cannot be ruled out. In recent times, from 23 November to 29 November 2020, more than 3000 cases were reported from Jodhpur area with a percent positivity of around 20%. Even till December 2020, Jodhpur's positivity hovered around 12%. Chi-squares analysis of the results ((165/2000 = 8.5%) and (3/110 = 2.5%)) showed a statistically significant difference with P < 0.05. This suggested that both groups were different, implying that in mines and quarries, social distancing could have been responsible for a lower frequency.
Though not definitive and though this is an initial report, the study results indicate that subjects in silicosis-prone area may not be at a higher risk for developing COVID-19, as proposed otherwise. However, it goes without saying that all residents should follow guidelines for prevention of COVID-19 infection.
Biological mechanisms protecting silicosis patients or those constantly exposed to dust from COVID-19 are unknown but could potentially be extensive pulmonary fibrosis found in these patients where inflammation with activated macrophages/lymphocytes is already present.[5]
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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