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International Journal of Preventive and Public Health Sciences • Sep-Oct 2015 • Vol 1 • Issue 3 1
Original Article
ABSTRACT
Background: Silicosis is an age-old occupational disease and remains a major occupational health problem in India.
Objective: To assess the prevalence of X-ray positive silicosis cases among chest symptomatic patients in a sample of a high-
risk group visited the special clinic at Minakhan Rural Hospital.
Materials and Methods: A clinic-based retrospective cohort study was conducted among 156 consecutive symptomatic
patients of suspect silicosis attended the special health clinic from October to December 2013 using a predesigned proforma,
confirmed by chest X-ray. Data analysis was done by Microsoft Office Excel 2010 and Statistical Package for the Social Sciences
2007.
Results: About 78.85% were diagnosed clinically to have silicosis, 69.23% had history of exposure, 50.64% were confirmed
radiologically, all were male, 55.29% were in the age group 30-44 years; statistically higher prevalence of X-ray-positive silicosis
was seen with longer duration of exposure, and strength of agreement between the chest physician and the radiologist was
good.
Conclusion: There is the need for formulating a countrywide strategy for prevention and control of silicosis in industrial
populations.
Key words: Cohort study, Occupational disease, Radiology, Silicosis, X-rays
INTRODUCTION
The full name of silicosis is a 45 letter word and the longest
word in the English language: Pneumonoultra microscopic
silicovolcanoconiosis.1
It is an inorganic pneumoconiosis (dust-
related disease); probably the oldest and the most common
occupational lung disease globally; occurs due to overexposure
and inhalation of crystalline silica dust which penetrate the
respiratory system and deposit on lung alveoli; cause the
development of scar tissue in the lungs. The disease is marked
by inflammation, scarring, and nodular lesions in the upper
lobes of the lungs.1
Occupations which are closely related to silica containing
dust exposure are mining, tunneling, road construction, rock
drilling, pottery making, sandblasting, stone cutting, quarrying,
etc.2,3
Silicosis is a fatal and incurable disease, only symptomatic
treatment is available, lung transplantation can be done for
most severe cases.2
There are 3 types of silicosis: Chronic or classical silicosis,
accelerated silicosis, and acute silicosis.
However, Pérez-Alonso et al. (2015) recommended to
update the diagnostic classification used until date because
Prevalence of X-Ray Positive Silicosis Cases among
Workers in a Stone Crushing Factory: A Clinic-Based
Retrospective Cohort Study
Suchandra Mitra (Chaudhury)1
, Mausumi Basu2
, Bimal Krisha Paul3
, Dipankar Maji4
, Kunal Kanti Dey5
,
Debjit Chakraborty6
1
District Epidemiologist, Integrated Disease Surveillance Program, North 24 Parganas, West Bengal, India, 2
Associate Professor, Department of
Community Medicine, IPGME&R and SSKM Hospital, Kolkata, West Bengal, India, 3
Deputy Chief Medical Officer of Health-II, North 24 Parganas,
West Bengal, India, 4
Deputy Director of Health Services (PH & CD), Swasthya Bhavan, Kolkata, West Bengal, India, 5
Assistant Chief Medical Officer
of Health, Barasat Sadar, North 24 Parganas, West Bengal, India, 6
State Epidemiologist, Integrated Disease Surveillance Program, Kolkata, West
Bengal, India
IJPPHS_5(3)_04_OA
DOI: ???
CORRESPONDING AUTHOR:
Dr. Mausumi Basu,
FA9, D. B. Nagar, Flat-A6, Kolkata - 700 059, India.
E-mail: basu.mausumi544@gmail.com
Submission: 00-0000; Peer Review: 00-0000; Acceptance: 00-0000; Publication: 00-0000;AQ1
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Mitra, et al.: Silicosis among Workers in a Stone Crushing Factory www.ijpphs.net
2 International Journal of Preventive and Public Health Sciences • Sep-Oct 2015 • Vol 1 • Issue 3
some cases of early silicosis can be missed among workers in
the production and installation of kitchen countertops.4
The ILO/WHO Global Program on Elimination of Silicosis
proposed to eliminate silicosis by 2030 as an occupational
disease and also suggested that each country should have a
national silicosis elimination program.5,6
Silicosis is prevalent all over India, especially in Western
and Central parts. As per recent estimates (2013) from India,
there are more than 3 million workers exposed to containing
dust silica and another 8.5 million work in construction and
building activities, who are similarly exposed to quartz.7
Slate pencil cutting, stone cutting, and agate grinding
industry carry a high risk of silicosis in India.3
Rajasthan alone
produces about 90% of sandstone,8
whereas deposits of
sandstone containing 96% of SiO2 found in Dhaulpur and
Karauli districts of Rajasthan.9
It was first reported in India by Krishnaswami Rao in1934
from Kolar Gold Fields. A historic study on Silicosis from 1940 to
1946 by Dr. Anthony Caplan and others among 7643 workers
of Kolar Gold Fields detected 3472 workers suffered from the
disease.10
There are very few epidemiological studies on silicosis
in India where the prevalence of silicosis varied from 3.5% in
ordnance factory11
to 54.6% in slate pencil industry.12
Saiyed
and Tiwari showed the prevalence of silicosis among stone
quarry workers was 21% and in the stone crushers was 12%.13
The varying prevalence in various sectors is due to the
silica concentration in the workplace environment and duration
of exposure to Silica. As there is no specific therapy for this
disease, steps should be taken for its prevention. The best way
to prevent silicosis is to identify workplace activities that produce
crystalline silica dust and then to eliminate and/or control the
dust. Thus, a mechanism should be in place for addressing
compensation issues and rehabilitation of affected workers.3
The problem of Silicosis in West Bengal is among stone
crushing/quarrying workers of Birbhum district. “West Bengal
Silicosis Control Programme” was conceived in July 2012 as a
state initiative which was piloted in Birbhum.
In Lakshmi Stone Factory of Asansole, West Bengal, India,
several workers are involved to perform stone crushing for
many years. However, there is no systematic documentation of
patients’ records to date. With this background, a program was
designed with the objective of to assess the prevalence of X-ray
positive silicosis cases among chest symptomatic patients in
a sample of a high-risk group (ex-workers) visited at a special
clinic at Minakhan Rural Hospital, Bashirhat Health District
under North 24 Parganas.
MATERIALS AND METHODS
Study Type and Setting
A clinic-based analytical retrospective cohort study was
conducted at a special health clinic at Minakhan Rural Hospital
(RH), after getting information from CMOH regarding 7
deaths at Minakhan Block of Bashirhat Health District, North
24 Parganas.
Study Population and Duration
The study was carried out among consecutive symptomatic
patients of suspect silicosis who attended the special health
clinic at Minakhan RH from October to December 2013, a
period of 3 months.
Sample Size and Sampling Technique
It was decided that all consecutive symptomatic patients
of suspected silico-tuberculosis who would attend the
arranged special health clinic at Minakhan RH during the
study period would be our sample size. Thus, the sample
size came to 156.
Inclusion Criteria
1. Patients above 14 years of age;
2. Not seriously ill;
3. Ex-worker of the Lakshmi Stone Crushing Factory;
4. Lived at Minakhan;
5. Complained of a chronic cough for more than 3 months
and/or breathlessness;
6. History of exposure to silica for more than 1 year;
7. Gave informed verbal consent.
Exclusion Criteria
1. Patients aged less than or equal to 14 years;
2. Seriously ill;
3. Not gave informed verbal consent to participate in the
study.
Study Variables
Age, gender, duration of exposure to silica, clinical findings, and
X-ray findings.
Study Tools
A predesigned proforma, relevant records and reports, and
chest X-ray. The proforma had 3 parts; Part 1 consisted of
socio-demographic variables of the study population, Part 2
consisted of clinical findings by chest physicians, and the Part 3
consisted of X-ray findings.
Data Collection Technique
Patients came at Health Clinic of Minakhan RH, North
24 Parganas, one medical team with chest physician examined
and treated them. A clinical assessment form was filled up by
the physician following history taking and clinical examination.
The nature and purpose of the clinic were explained to the
participants by the physicians and the accompanying Health
workers. The eligible study population were referred for chest
X-ray after examined by the chest physicians.
Chest X-Ray
Of the 156 symptomatically suspected patients identified by
the health workers based on inclusion criteria, 123 cases were
clinically suspected to have silicosis by the chest physicians at
the clinic and were referred for chest X-ray at Minakhan RH using
a 300-mA machine. The X-rays were examined independently
by a radiologist and a chest physician. The X-rays were
interpreted as positive by the presence of fibrosis and opacities
in lung fields. Study population were diagnosed to have silicosis
if either of the chest physician and/or the radiologist rated the
X-ray as positive. The inter-rater agreement between the chest
physician and the radiologist was 0.786 by Cohen’s kappa
coefficient statistics.
Data Analysis
Data were entered in Microsoft Office Excel 2010 (Microsoft
Corp, Redmond, WA, USA) and analyzed with Statistical
Package for the Social Sciences (SPSS Inc. Released 2007.
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www.ijpphs.net Mitra, et al.: Silicosis among Workers in a Stone Crushing Factory
International Journal of Preventive and Public Health Sciences • Sep-Oct 2015 • Vol 1 • Issue 3 3
SPSS for Windows, Version 16.0. Chicago) and Epi-info 6.04d
(Centers for Disease Control and Prevention, Atlanta, GA, USA,
2001) using percentages Chi-square; and relative risk was used
to demonstrate the association of duration of exposure to silica
dust and Silicosis, and Kappa statistics was used to show the
strength of agreement between the chest physician and the
radiologist. P < 0.05 was considered as significant.
RESULTS
Distribution of the study population as per prevalence of
silicosis was demonstrated in Table 1. It was seen that among
156 symptomatically suspected silicosis; 123 (78.85%) were
diagnosed clinically to have silicosis, 108 (69.23%) had a history
of exposure to silica dust, and 79 (50.64%) were confirmed
radiologically as having silicosis. Thus, among 123 presumptive
cases; 79 (64.27%) had confirmed silicosis and prevalence
among symptomatic workers with a clear history of exposure
was 73.15%.
The demographic profile of the presumptive cases
shown in Table 2. In this study, all participants were male;
about 21.95% were in the age group 15-29 years, 55.29%
were in the age group 30-44 years, 20.32% were in the age
group 45-59 years, and only 2.44% were 60 years or more.
In the age group 15-29 years, there were two cases below
18 years.
Adequate exposure history could be elicited for
108 (69.23%) participants only. About 63 (58.33%) of the
patients were found to have been working in the industry for
more than 5 years. It was seen that with longer duration of
exposure, higher prevalence of X-ray-positive silicosis was seen
which was statistically significant (P < 0.05) (Table 3).
Strength of agreement between the chest physician and
the radiologist was shown in Table 4. Kappa statistic was
0.786 (95% CI 0.671-0.900), and the strength of agreement
was good (i.e. between 0.61 and 0.80).
Chest X-rays of different phases of silicosis and picture of
stone crushing factories are attached as Figure 1.
DISCUSSION
In the present study, the prevalence of radiologically confirmed
silicosis was 50.64% which was comparatively high than other
similar studies in India and abroad.14-19
Study at stone cutting factories at Malayer-Azandarian
(Hamadan province of Iran) by Aghilinejad et al.14
revealed
prevalence of silicosis was 8.9%, Churchyard et al.15
at gold
miners of South Africa showed prevalence of silicosis to be
18.3-19.9%, Athavale et al.16
at India indicated an incidence of
silicosis among flour mill workers working with silica containing
grinding stones was 30.4%, Chen et al.17
among tin miners in
China identified the prevalence was 33.7%, Tse et al.18
in gold
miners at China revealed the prevalence of accelerated silicosis
was 29.1%, and Pérez-Alonso et al.19
among Spanish quartz
conglomerate workers demonstrated 20% prevalence rate. In
contrast, Chaudhury et al.20
at agate workers at Khambhat of
Gujarat demonstrated the prevalence was 69.1% which was
higher than our study.
With regard to age and gender prevalence, all of this
study population were male, and 55.29% were in the age
Table 1: Distribution of the study population as per prevalence of
silicosis (n=156)
Prevalence Number Percentage
Clinically presumptive cases 123 78.85
Exposure history obtained 108 69.23
Radiologically confirmed cases 79 50.64
Total patients examined 156 100
Table 2: Age group distribution of presumptive cases (n=123)
Age group (in years) Number Percentage
15-29 27 21.95
30-44 68 55.29
45-59 25 20.32
≥60 03 02.44
Total 123 100
Table 3: Relation among duration of exposure with X-ray confirmed silicosis
(n=108)
Duration of
exposure
X-ray confirmed silicosis
(n (%))
Chi-square;
P value
Relative risk
(95% CI)
Positive Negative Total
More than
5 years
54 (85.71) 9 (14.29) 63 (58.33) 12.15; 0.000 1.54; 1.16-2.04
≤5 years 25 (55.56) 20 (44.44) 45 (41.67)
Total 79 (50.64) 29 (49.36) 108 (100)
CI: Confidence interval
Table 4: Strength of agreement between the chest physician and the
radiologist (n=123)
Chest X-ray diagnosis
Diagnosed by
chest physician
Diagnosed by radiologist
Positive Negative Total
Positive 74 7 81
Negative 5 37 42
Total 79 44 123
Kappa statistic: 0.786 (95% CI 0.671-0.900) and the strength of agreement
was good (i.e., between 0.61 and 0.80), CI: Confidence interval
Figure 1: Chest X-rays showing uncomplicated and complicated silicosis;
(a) Normal chest X-ray, (b) Simple Silicosis, (c) Progressive massive fibrosis,
(d) Eggshell calcification - almost exclusively silicosis
dc
ba
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4 International Journal of Preventive and Public Health Sciences • Sep-Oct 2015 • Vol 1 • Issue 3
group 30-44 years with a mean age of 43 years, whereas in
Coimbatore study by Sivanmani and Rajathinakar21
94% were
male and only 1 was female, with a mean age of 55 years.
This high prevalence among males was seen in earlier studies
also.14-20
The prevalence of silicosis was related to cumulative
exposure to silica dust in the present study and many other
previous studies.14-20
Limitations
The results were not generalizable to the community as it was
a clinic-based study. For 3 months after the clinic opened, 7
death from Silicosis reported from the different private sector
which we are not included in our study for some technical
problem.
CONCLUSIONS
In our study, it was of great concern that more than half of all
chest symptomatic cases examined in this clinic were diagnosed
as silicosis by positive X-ray picture. Middle age group males
with longer duration of service were mostly affected. There was a
statistically significant association between duration of exposure
to silica dust and development of silicosis which was a significant
determinant of risk of Silicosis. There was a good agreement of
diagnosis of silicosis by chest physicians and radiologists.
Recommendations
The Lakshmi Stone Crushing Factory at Asansole is a small,
limited factory. We observed those victims who were directly
exposed to the silicon dust as workers of the factory. But,
children and non-exposed persons should be screened for
further studied.
The troubled community working in this industry knew
the consequences but still continued to work with silicon dust
to earn their livelihood. Many people denied that they were
currently working in the industry, despite their occupation being
known to the Health Workers. Our findings provided evidence
of the catastrophic effects of exposures to silica in the workers,
which calls for urgent protective measures.
The study confirmed that there was need of periodic
medical examination of stone factory workers. In the absence
of specific treatment only approach is primary prevention,
i.e., control the exposure to respirable crystalline silica dust. So,
the implementation of periodic air-monitoring and dust control
strategies in stone factories, use of personal protective devices
for workers should be mandatory. Education plays a critical role
in control measures in the workplace betweem employers and
workers.
ACKNOWLEDGMENT
We are highly acknowledge the Chief Medical Officer of
Health (CMOH)-North 24 Parganas, CMOH - Bashirhat
Health District, Deputy Chief Medical Officer of Health – II
North 24 Parganas, Assistant Chief Medical Officer of Health
(ACMOH) - Bashirhat, ACMOH-Barasat, District Tuberculosis
Officer (DTO) - North 24 Parganas, Block Development Officer
(BDO) - Minakhan Block, and Block Medical Officer of Health
(BMOH) – Minakhan Block.
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who.int/occupational_health/publications/newsletter/gohnet12e.pdf. [Last
accessed on 2015 Sep 16].
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7. Jindal SK. Silicosis in India: Past and present. Curr Opin Pulm Med
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8. Indian Bureau of Mines: Indian Minerals Yearbook 2012. Nagpur:
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9. Rajasthan Department of Mines and Geology: (n.d.). Available from: http://
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10. National Institute of Miner’s Health. Ministry of Mines. Government of India.
Available from: http://www.nimh.gov.in/aboutus.html. [Last accessed on
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11. Viswanathan R, Boparai MS, Jain SK, Dash MS. Pneumoconiosis
survey of workers in an ordnance factory in India. Arch Environ Health
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12. Saiyed HN, Parikh DJ, Ghodasara NB, Sharma YK, Patel GC, Chatterjee SK,
et al. Silicosis in slate pencil workers: I. An environmental and medical study.
Am J Ind Med 1985;8:127-33.
13. Saiyed HN, Tiwari RR. Occupational health research in India. Ind Health
2004;42:141-8.
14. Aghilinejad M, Naserbakht A, Naserbakht M, Attari G. Silicosis among
stone - Cutter workers: A cross-sectional study. Tanaffos 2012;11:38-41.
15. Churchyard GJ, Ehrlich R, teWaterNaude JM, Pemba L, Dekker K,
Vermeijs M, et al. Silicosis prevalence and exposure-response relations in
South African goldminers. Occup Environ Med 2004;61:811-6.
16. Athavale A, Iyer A, Sahoo D, Salgia K, Raut A, Kanodra N. Incidence of
silicosis in flourmill workers. Indian J Occup Environ Med 2011;15:104-8.
17. Chen W, Zhuang Z, Attfield MD, Chen BT, Gao P, Harrison JC, et al.
Exposure to silica and silicosis among tin miners in China: exposure-
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18. Tse LA, Li ZM, Wong TW, Fu ZM, Yu IT. High prevalence of accelerated
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19. Pérez-Alonso A, Córdoba-Doña JA, Millares-Lorenzo JL, Figueroa-Murillo E,
García-Vadillo C, Romero-Morillo J. Outbreak of silicosis in Spanish quartz
AQ2
Figure 2: ???
• Silicosis is responsible for substantial morbidity and mortality
• Silicosis causes enormous economic loss to the nation as a whole and industry
in particular. Silicosis is a preventable disease and can be totally eliminated
• Many countries have reduced incidence of silicosis by appropriate.
AQ3
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