GENERATION OF DATABASE ON OCCUPATIONAL DISEASES (Achievements)

Prior to the establishment of National Institute of Occupational Health (NIOH), very limited and scattered data were available on occupational diseases in the country. Over the last three decades, NIOH has generated baseline data on pattern of common and important occupational morbidities such as silicosis, byssinosis, asbestosis, coal workers’ pneumoconiosis (CWP), noise induced hearing loss, pesticide toxicity, metal exposure, excessive heat exposure etc. The details of some of these conditions are given below: 

Silicosis     

Silicosis is the commonest and one of the most serious occupational diseases. It is irreversible fibrosis of the lungs caused by inhalation of free silica dust. It is estimated that about 3 million people working in various types of mines, ceramics, potteries, foundries, metal grinding, stone crushing, agate grinding, slate pencil industry etc., are occupationally exposed to free silica dust and are at potential risk of developing silicosis. Silica exposure also predisposes to development of pulmonary tuberculosis, which is an important public health problem in the country. Some of the landmark studies carried out by NIOH are as follows: 

Slate Pencil Industry:   

Slate pencil cutting is a cottage type of industry, located in the Mandsaur district of M.P. Slate pencils are made by cutting slate stone on a circular electric saw and during this process, clouds of dust are generated pervading the work environment. An environmental and epidemiological study consisting of clinical examination, pulmonary function test, chest X-ray and laboratory investigations, carried out in  slate pencil workers revealed following results:

                                    The air borne free silica dust levels were several times higher than the limits prescribed under the Factories Act. Radiological evidence of silicosis was observed in 54.6% slate pencil workers and progressive massive fibrosis (PMF) was found in 17.7% slate pencil workers. About 50% of the workers suffering from silicosis were below 25 years of age and had worked for less than 7 years. Immunological studies among workers having silicosis showed increase in the levels of serum IgG and serum IgM. Pulmonary function test showed high prevalence of obstructive type abnormality and these abnormalities were seen even in workers with normal chest radiograph. Follow up examination of these workers after an interval of sixteen months revealed rapid progression of the disease and it was  related to the stage of silicosis during initial examination. About 4% of the subjects who had  participated in the initial survey died during the intervening  period. Their mean age at the time of death was 34.7 (18‑55)  years and the mean duration of work was 11.75 (3‑20) years. All  the deceased  subjects were male and were suffering from PMF.

 Agate Industry:

             Agate grinding and polishing is a traditional vocation in the Khambhat Taluka of Gujarat and Jaipur (Rajasthan). Following sporadic reports of silicosis and deaths among the agate grinders, NIOH carried out detailed clinico-radiological  survey of agate workers which showed that the problem of silicosis  was most severe  among the agate grinders. The prevalence of  silicosis in male and female agate grinders was  39.8% and 34.2%  respectively. About 19% of the male agate grinders and 22% of female agate grinders developed silicosis within five years. The overall prevalence of tuberculosis amongst male and female agate grinders was 37.4% and 40.3% respectively. Pulmonary function abnormalities were found in about 51% grinders. The mean "total" and  "respirable" dust concentrations during agate grinding were 25.4 (14.5 ‑ 35.1)  and 2.74 (1.73 ‑  4.04) mg/M3 respectively, which are much higher than the prescribed limits. The free silica contents of the dust  was 60%.

 Quartz Grinding:

 Quartz powder is widely used in the industry for making glass, ceramics and potteries, as chemical filters, fillers etc. In almost all the states of the country, thousands of workers are engaged in quartz grinding. Quartz grinding is one of the deadliest occupations causing exposure to almost 100% free silica leading to silicosis in a matter of few months.

             Studies in quartz crushing units revealed evidence of silicosis in 12% workers. More than 90% of these workers were exposed for less than 3 years.  Some cases of silicosis were observed in workers exposed for less than 1 year. Relatively low prevalence of silicosis observed was due to the “healthy worker effect” i.e. the sick workers not reporting for the work as the job demanded high degree of physical fitness. This was confirmed from house to house survey by the local factory inspector, who reported that the missing workers (absentees) numbering about 490 had died at a very young age presumably due to silicosis. The mean concentrations of air borne respirable dust in six factories ranged from 1.9 mg/M3 to 24.3 mg/M3 with 95% to 99% free silica contents. The prescribed limit is 0.025 mg/M3 of air.  

            Another study among sand grinders, who had worked on an average for only 5 years, showed 28.1% prevalence of silicosis.  

Stone Quarries:

   An environmental and epidemiological survey carried out in stone quarry workers revealed evidence of silicosis in 22.4% workers. About 32% workers showed radiological evidence of tuberculosis. Most of the cases of silicosis were found in the workers who had worked for over 10 years. The mean total  dust concentrations in two quarries were 3.38 and 3.72 mg/M3 and respirable dust concentrations in two quarries were 0.80 and 0.85 mg/M3 respectively  with about 70%  free silica. 

Mica Processing Industry:

  Radiological examination of mica processing workers revealed evidence of pneumoconiosis of category 1 or more in 6.23% workers and evidence of pleural  thickening was found in 4.3% workers. In female mica processing workers the prevalence of pneumoconiosis was 2.7%.

Asbestosis

Exposure to asbestos causes asbestosis, lung cancer and mesothelioma of pleura and peritoneum. In India, the total use of asbestos is 1.25 lakh tonnes, out of which more than 1.0 lakh tonnes is being imported. Significant occupational exposure to asbestos occurs mainly in asbestos cement factories, asbestos textile industry and asbestos mining and milling. NIOH has carried out studies in all these industries and generated baseline data. Following is the summary of these studies.

 Asbestos Cement Industry:

   There are 18 asbestos cement factories located in different parts of the country. NIOH carried out environmental epidemiological studies in four asbestos cement factories located in Ahmedabad, Hyderabad, Coimbatore and Mumbai. The prevalence of asbestosis in these factories varied from 3% to 5%. The levels of asbestos fibres were found to be higher than the permissible levels of 2fibres/ml  in two of the factories. 

Asbestos Textile Industry:

  Making of asbestos yarn and ropes is done mostly in the unorganised sector of industries with very poor safety measures. The average levels of air borne asbestos fibres varied from 216 to 418 fibres/ ml. The permissible level is 2 fibres/ml. The prevalence of asbestosis was 9%. This relatively low prevalence of asbestosis despite high environmental levels was attributed to high labour turn over. Cases of asbestosis were observed in workers having less than 10 years exposure in contrast to the reported  average duration of over 20 years.

Asbestos Mining and Milling:

   In India, the mining and milling of asbestos is done in Cuddapah (Andhra Pradesh) and Devgarh (Rajasthan). Environmental and epidemiological studies in mining and milling units were carried out in both the places. In asbestos mines at both locations, the air borne fibre levels were within permissible limits. The average fibre levels in milling units varied from 45 fibres/ml to 244 fibres/ml of air. The overall prevalence of asbestosis in mining and millingnits was 3% and 21% respectively.  

Byssinosis

Byssinosis is an occupational lung disease caused by exposure to cotton, flax and hemp dust.  Maximum number of workers with byssinosis are reported in the cotton textile industry as it is one of the largest industries in the world. In India, there are about 1.07 million workers engaged in the manufacture of cotton textiles. The  workers engaged  in the initial processes of textile manufacturing (blow, card, frame and ring frame) are exposed to cotton dust and develop the disease after some years of exposure.  Several studies have reported byssinosis in India but they failed to demonstrate the severity and magnitude of the disease.  The low prevalence reported in those studies created an impression that the disease is not an important problem.  The epidemiological studies conducted by NIOH for the first time showed a very high prevalence of the disease especially in blow (30%) and card (38%) sections. These prevalence figures were same as reported in U.K. and other countries of the world.

Pneumoconiosis and Other Respiratory Morbidities Among Coal Miners in India

 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 pneumoconiosis (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.

Noise Pollution and Health Effects

 Noise is ubiquitous in industry. Continuous exposure to noise levels above 90 dBA can produce adverse auditory and non-auditory health effects. Studies carried out by NIOH showed that the sound pressure levels were very high in various industries, ranging from 102-114 dBA in textile industries, 93-103 dBA in pharmaceutical firms, 90-102 dBA in fertilizer plants, 90-119 dBA in oil and natural gas complexes in Bombay High, 60-102 dBA due to road traffic in Ahmedabad city, 90-102 dBA in surface rail traffic, 70-111 dBA in metro rail, 90-112 dBA for air traffic. The following health effects were observed due to excessive noise. 

Auditory Effects:

  Hearing acuity of textile weavers aged 25-39 years, exposed to a noise level of 102-104 dBA was found to be poor. Noise induced hearing loss (NIHL) at 4000Hz was as high as 30 dB in the age range 25-29 yrs, 40 dB in the age range 30-34 yrs and 45 dB in the age range 35-39. The NIHL at 4000Hz is known to be irreversible.  

Non-auditory Effects: 

In addition to hearing loss, exposure of workers to noise levels of 90-119 dBA was also found to result in sleep disorders, mental fatigue, annoyance and reduced alertness, compared to those working in a relatively quiet room (60-75 dBA). Further, it was seen that the speed of performance was impaired significantly by noise. Adverse effects of noise were observed in tweezer dexterity with higher degree of degradation observed at moderately different levels of the task. Similar observation was also noticeable in two hand coordination. Reaction time was enhanced under high noise condition. Certain physiological measures (oral temperature, pulse rate and skin temperature) were also found to be high in workers engaged at high noise condition. 

Production Efficiency:

  The production data of each weaver collected for at least 15 days after the weavers were found to have had worn hearing protection devices (ear plug and ear muff) for 30 successive days was examined. The results showed that the production of the weavers wearing ear-muffs aided with ear plugs was significantly higher than the other weavers.  The findings thus suggest that the weavers with hearing protection devices had an increased rate of production, parallel to the increasing degree of protection from noise rendered by the protective devices. 

Interaction effects: Noise and Heat:

  The interaction effects of noise and heat on neuromotor based functions were studied in acoustic chamber. The combined effect of heat (35°C) and noise (100 dB) caused higher error rate in card sorting (face value) and decreased accuracy in reasoning ability. 

Noise and Illumination: 

The interaction effect of noise and illumination on performance efficiency examined under six experimental conditions of three levels of illumination (50, 150 and 300 Lux) and two levels of noise (70 and 100 dB) revealed significant slowing of response rate in letter cancellation test in noise condition of 100 dB and progressive improvement with the gradual rise of illumination level. The combined effect of noise and illumination on the accuracy scores reflected performance decrement under high illumination level (300 Lux) and under high noise condition (100 dB). The rate of decline in the accuracy and efficiency of performance in hand precision test under high illumination level was significantly more pronounced under noise condition than in the quiet condition (70 dB) 

Occupational Exposure to Heavy Metals 

Occupational exposures to metals were evaluated in a number of industries such as printing press, type foundries, ceramic and pottery foundries, battery reconditioning shops, garage workers, mining and smelting plants, silver foundries and refinery, etc. In some of the units like smelting, printing press, battery reconditioning shops, refinery etc. the lead exposure was observed to be higher than the TLV. Appropriate preventive measures were suggested to minimize the lead exposure in these industries.  

Occupational Exposure to Organochlorine Pesticides 

The study on insecticide hexachlorocyclo-hexane (HCH) was of its own kind that covered all the four HCH manufacturing units in the country. Beta HCH was found to be a predominant isomer present in the blood samples of exposed workers.  This is due to accumulation of Beta-HCH  which is a stable isomer, has a long half-life  and is almost non-biodegradable.  Beta-HCH was found even in the serum samples of workers who had  discontinued their  jobs for several years.  Therefore Beta-HCH is taken as the marker for cumulative exposure for HCH and lindane for immediate past exposure.  

About 25% of serum samples of workers with significantly high levels of serum HCH residues showed circulating immune complexes(CIC) of IgG and 20% showed CIC of IgM whereas CIC of C3 and C4 were not detected. Electro cardiogram abnormalities such as Left Ventricular Hypertrophy (LVH), Left Anterior Hemiblock, Right Bundle Branch Block and Wolff Parkinson White Syndrome were reported for the first time. Increased activity of Lucine amino peptidase. 5-nucleotidase, and Gamma Glutamyl transpeptidase, Ornithine Carbamoyl Transpeptidase was also observed. 

Agricultural Ergonomics 

Several studies have been undertaken to examine health and safety of the workers in agriculture. Research on the problems of agricultural work force has a precise emphasis to resolve problems of work environment, to alleviate rigors at the workplace and to improve performance ability of the workers.. Emphasis has been given on the principles of ergonomics, i.e., work simplication and workload classification, modification of work methods and manually operated tools and implements. 

1.                        The farm population was examined with reference to (i) possible changes in working capacity with nutrition, increasing age and organic constitutional differences, (ii) the mean level of energy expenditure during occupational tasks in farming and non-farming seasons, (iii) setting work standards as relative severity of maximal working capacity. About 63% of the total man-hours were occupied by moderately heavy tasks; average working day energy expenditure corresponds to 30 to 40% of maximal work capacity of persons. Based on large number of observations, recommendations arrived at the permissible daily energy output as 4.6 MJ. In summery, the recruitment, selection and placement of labour may be possible based on the work capacity data of the farm workers. A better form of work organisation through the management of human labour may thereby be possible.

2.                        Modification of work methods and manually operated tools and implements — attempts were made to simplify manually operated farm tools and implements, by which the physical demand of work may be minimized. Studies were carried out in different types of weeders to remove weeds from dry and wet land, plough for deep and shallow ploughing, serminated seedlings to minimize time requirement of seeding operation, threshing operation either by manual beating or pedal threshing, use of different types of hand tools, including sickle, beater, shovel, etc. A prototype of a ploughing device was designed for better tillage.  

Women in Industry: Health and safety 

The institute has a dedicated thrust on the problems of the health of women, towards prevention of occupational hazards and promotion of health and safety of women workers in diverse occupational activities. The studies have been undertaken including workforce in unorganised and organised sectors. 

·        Physiological evaluation of women agricultural workers in relation to workload, working climate and handtools.

·        Anthropometry and nutritional status of women in small scale industry, e.g., beedi industry, garment manufacturing, 

·        Work stresses of women engaged in telecommunication, hospital services, beedi industry, garment manufacturing, khadi, etc.

·        Work methods and posture analysis of women in sitting work in small industries.

·        Work, health and safe exposure of women in hot environment, with special reference to simulated experimentation in the climatic chamber.