This study was undertaken in collaboration with the International Development Research Centre (IDRC), Canada, consisting of clinico-radiological examination and ventilatory function tests in 5777 underground coal miners and 1236 surface coal miners. This study revealed that the prevalence of pneumoconiosis (category 1/1 and more) in underground coal miners was 2.84% and in the surface coal workers it was 2.10%. Majority of the cases of neumoconiosis (84.1% of total cases) in underground coal miners belonged to category 1/1.
There were no cases of pneumoconiosis higher than category 2/2. Only three cases of progressive massive fibrosis (PMF) were found in underground coal miners and none in surface coal workers. The prevalence of chronic respiratory symptoms amongst the underground miners was 31.3%, which was significantly higher than that amongst the surface coal workers (17.3%). The overall prevalence of functional abnormalities of lung in underground coal miners and surface coal workers was 45.4% and 42.2% respectively.
The prevalence of obstructive (inclusive of mixed) type of functional abnormalities of lungs amongst underground coal miners and surface coal workers was 28.9% and 24.1% respectively. The environmental study indicated that the air borne dust concentrations were much higher than the suggested threshold limit values (TLV) in underground and surface coal mines. The noise levels and the parameters of heat stress also exceeded the TLVs.
This study established a low prevalence of pneumoconiosis and absence of more severe cases of pneumoconiosis in Indian coal miners and also reported very high prevalence of non pneumoconiotic respiratory morbidity in coal miners.
Non-occupational Pneumoconiosis in High Altitude Villages of Ladakh
Till recently it was believed that the problem of silicosis and other types of pneumoconiosis is limited to industries and mines only, although a few scattered case reports describing non‑occupational pneumoconiosis cases are available. NIOH made detailed investigation of the cases of non occupational pneumoconiosis reported from certain villages of Ladakh. Environmental epidemiological study showed the prevalence of pneumoconiosis to be 2.0%, 20.1% and 45.3% respectively in three villages. The chest radiographs were indistinguishable from those of miners and industrial workers suffering from pneumoconiosis. There are no industries and mines in this district and the pneumoconiosis observed amongst the villagers was attributed to dust stormsand exposure to soot from domestic fuels used for cooking and heating. The dust concentrations in the kitchens without chimneys varied from 3.22 to 11.30 mg/M3 with a mean value of 7.50 mg/M3.
Dust samples sufficient enough to allow measurement of the dust concentrations could not be collected during the periods of dust storms, but preliminary analysis of the samples indicated that about 80% of the dust was respirable and its free silica contents ranged between 60 and 70%. This study is one of its kind reporting endemic non occupational pneumoconiosis.