This document discusses silicosis, an occupational lung disease caused by inhalation of crystalline silica dust. It provides details on the epidemiology, pathogenesis, clinical features, diagnosis, and prevention of silicosis. The key points are: 1. Silicosis is prevalent among stone crushers and quarry workers in West Bengal, India. It has a long latent period and exposure to silica dust can cause irreversible lung scarring. 2. Prevention strategies include controlling dust at the source, using ventilation systems, training workers, conducting health monitoring, and enforcing exposure limits. 3. A silicosis prevention program in West Bengal aims to guide action to eliminate silicosis through coordination between

1. Epidemiology - Silicosis
Dr. Palash Das, MD
Associate Professor, Community Medicine
CMSDH, Kamarhati, Kolkata - 700058

2. Stone Crusher

3. Quarry

4. Genesis of state silicosis project
GPES
encourages to establish
NPES
to engage government, national employers’
and workers’ organizations, as well as other
partners concerned in its active
implementation.

5. Genesis of state silicosis project
• Aim: To guide action in order to prevent and
ultimately eliminate silicosis as an
occupational disease and to protect workers
against this incurable and often highly
disabling disease.
• West Bengal has proposed outline for State
Silicosis Project (SSP)

6. What is the full name of silicosis?
• Probably this is the first time you come across with
this 45 letter word and the longest word in the
English language.
Pneumonoultramicroscopicsilicovolcanoconiosis

7. Magnitude of the problem
This incurable disease affects tens of millions
of workers engaged in hazardous dusty
occupations in many countries.

8. Magnitude of the problem
West Bengal: Silicosis is prevalent in the
eastern five districts – i.e. Purulia, Bankura,
Birbhum, Paschim Medinipur and Burdwan.
Affected 23 Blocks are situated in these five
districts. These blocks are not evenly
distributed.

9. Magnitude of the problem
Purulia: Balarampur, Barabazar, Manbazar-I, Manbazar-
II, Bundwan
Burdwan: Salanpur, Barabani, Jamuria, Ranigunj,
Asansol Municipal Corpn., Faridpur-Durgapur
Birbhum: Muraroi-I, Nalhati –I, Rampurhat-I,
Mahammad Bazar,
Bankura: Saltora, Mejia, Borjora, Chhatna, Gangajalghati
Paschim Medinipur: Binpur I/II, Jhargram, Gopiballavpur
I/II

10. Magnitude of the problem
Birbhum district: Stone crushing set-ups: 1063,
Quarries: 248
Tens of thousands workers are involved for
their earning in the smoky environment
caused by crystalline silica dusts.
The susceptible population: Estimated to be
3634367 (around 40 lakhs at present).

11. Silica dust concentration
• Permissible limit of crystalline silica in air is 0.1
mg/m3
(OHSA)
• Respirable dust concentrations in three factories of
India: : 1.8-14.0 mg/m3
near the jaw crusher, 3.4-46.7
mg/m3
near the hammer mill and 4.2-50.3 mg/m3
near the screening cum bagging processes.
• In West Bengal: This can be done at stone crushing
factory during working and also non-working hours.
Factually during work, the area was seen cloudy /
smoky (module figure 1, 2, 3, 4).

12. Socio-economy of silicotics
• Social and economic impact of the silicosis
attracts attention of social leaders,
economists, policy makers of health, labour
organizations.
• Disability and death of these precious
productive population make the state
pressurised on its economy.

13. Socio-economy of silicotics
• Estimated impact on state economy resulting
from sickness absenteeism, lost working days,
loss of qualified labour, reduced productivity,
burden on worker’s compensation system
• Health care costs
• Estimate of economic benefits by prevention
program

14. Target Groups at risk
• The incidence of silicosis is primarily
predominant among the stone crushers and
quarry workers;
• However workers of other industries are
employees of mining and related milling
operations, silicon and ferrosilicon
foundries, agriculture, ceramic industries,
construction industries in the state of West
Bengal.

15. Causal exposures/industries
• Mining: Tunnel drillers/blasters, roof bolters,
transportation crew are at highest risk (also
face workers and others)
• Quarries: Workers who blast, cut, and
transport stone.
• Stone-working: Stone-masonry (granite
dressing and grinding), Flint-knapping

16. Causal exposures/industries
• Heavy engineering and manufacture: Shot
blasting, Preparation and use of grinding
wheels/stones, Use of compressed airlines to
clean off silica-containing material
• Foundries: Sand-moulding, Shot-blasting,
Compressed air cleaning of moulded items,
Fettling, Ceramics and pottery making, Brick-
making

17. Epidemiology
• Long latent period between exposure to silica
and onset of disease.
• The risk of disease varies according to level of
exposure.
• People are exposed to noxious dusts running
an unacceptably high risk and silicosis is
world-widely spread

18. Epidemiology
• Up to 30-50% of workers in primary industries
and high risk sectors may suffer from silicosis
and other pneumoconioses.
• Increased incidence of tuberculosis with the
increasing severity of silicosis.

19. Epidemiology
• It is possible to significantly reduce the
incidence rate of silicosis with well-organized
silicosis prevention programs
• Only approach towards the protection of
workers’ health is the control of exposure to
crystalline silica dusts

20. Epidemiology
• Incubation period may vary from few months
up to 6 years of exposure.
• Respirable crystalline silica (RCS) is found in
stone, rocks, sands and clays.

21. Patho-physiology
• Chemical composition of dust, size of
particles, duration of exposure and individual
susceptibility influence incidence
• The higher is the concentration of free silica in
the dust, the greater is the hazard.
• Particles between 0.5 to 3 µ enter into the
lungs with ease.
• The longer is the duration of exposure the
greater is the risk of developing silicosis.

22. Patho-physiology
• Exposure to RCS over a long period can cause
fibrosis (hardening or scarring) of the lung
tissue with a consequent loss of lung function
• The particles are ingested by the phagocytes
which accumulate and block the lymph
channels.
• Pathologically silicosis is characterized by a
dense nodular fibrosis. The nodule varies in
size ranging from 3 to 4 mm in diameter.

23. Forms of silica
• Crystalline silica: Quartz, cristobalite,
tridymite
• Microcrystalline silica: Minute quartz crystal
bonded together with amorphous silica (Flint)
• Amorphous silica: Kieselguhr from skeleton of
diatoms; Less toxic than crystallint silica;

24. Patho-physiology
Silica dust particles in lungs
Ingestion by macrophages
Inflammatory response by tumour necrosis factors,
IL – 1, Leukotriene B4,other cytokines
Fibroblast proliferation and collagen production
Fibrosis and nodular lesions (Nalp 3 inflammasome)

25. Patho-physiology
• Clinically, the onset of the disease is insidious.
Some of the early manifestations are irritant
cough, dyspnoea and pain in chest.
• Impairment in lung function is more in
advanced disease.
• An X-Ray of chest shows – “Snow-storm”
appearance in the lung fields.

26. Some recognized types of silicosis
• Simple chronic silicosis:
• Sub-acute silicosis:
• Accelerated Silicosis:
• Acute Silicosis:
• Progressive massive fibrosis (PMF):

27. Clinical features
• In most cases, exposure for few months to
years is required.
• The main symptoms of silicosis are (1) a
persistent cough, (2) persistent shortness
of breath, (3) weakness and tiredness

28. Examinations of patients
• History of the patient’s problem
• X-Ray chest: Patchy small airway consolidation,
upper- and mid-zone nodular fibrosis, with classical
feature of ‘egg-shell’ calcification of the hilar lymph
nodes
• Computerised Tomographic Scan of Chest:
• Pulmonary Function Test (PFT): Impaired pulmonary
function.
• Tests for Tuberculosis
• Other relevant tests for other disease:

29. ILO Classification
• The size of small round opacities
– p (up to 1.5 mm),
– q (1.5-3 mm),
– r (3-10 mm).
– Irregular small opacities are classified by width as
s, t, or u (same sizes as for small rounded
opacities).

30. ILO Classification
• Lung Zones:
– Each lung is mentally subdivided by the reader
into 3 evenly spaced zones
– upper, middle, and lower
– The zones in which the small parenchymal
opacities appear are recorded.

31. ILO Classification
• Profusion (frequency) of small opacities
• 4-point major category scale (0, 1, 2, 3),
• Each major category divided into three, giving
a 12-point scale between 0/- and 3/+
• 0/-, 0/0, 0/1, 1/0, 1/1, 1/2, 2/1, 2/2, 2/3, 3/2,
3/3, and 3/+

32. ILO Classification
Major Category (first number) 0 refers to the
absence of small opacity and category 3 represents
the most profuse in X-Ray
Minor category (second number) represents either
the profusion seriously considered as an alternative,
or if none, the same profusion as the major category.
Example: If the reader thinks the x-ray has profusion
most like the standard x-ray for category 1, but
seriously considered category 2 as an alternative
description of the profusion, then the reading is 1/2.

33. ILO Classification
• Large opacities are defined as any opacity greater
than 1 cm that is present in a film. These are
classified as category A (Combined dimension
does not exceed 5 cm)
• Category B (Opacities whose combined dimension
exceeds 5 cm but does not exceed the equivalent
area of the right upper lung zone)
• Category C (size is greater than category B)

34. Normal Radiograph

35. Small Parenchymal Opacities in Coal
Workers' Pneumoconiosis

36. Large Parenchymal Opacities (Progressive
Massive Fibrosis) in Coal Workers’
Pneumoconiosis

37. Possible complications
• Lung Cancer
• Progressive massive fibrosis
• Respiratory failure
• Tuberculosis
• Further problems: Chest infections,
pulmonary hypertension, heart failure,
arthritis, kidney diseases, COPD

38. Diagnostic Protocol
• An expert professional (Occupational Diseases
Specialist), Chest Specialist, Pulmonologist
• Occupational exposure limit of 0.1 mg/m3
to 0.05
mg/m3
)
• Suspected case: History of occupation in
hazardous industry and cough of long duration with
dyspnoea identified by any person.
• Probable Case: History of occupation in hazardous
industry and cough of long duration with progressive
exertional dyspnoea, loss of weight, emphysema
verified by an experienced professional person
(Doctor).

39. Confirmed case
• History of occupation in hazardous industry
and cough of long duration with progressive
exertional dyspnoea, loss of weight,
emphysema and X-Ray of Chest showing
“snow storm” appearance.

40. Role of a General Physician
Suspect the condition after asking about
patients’ symptoms and work history, and
listening to his lungs with a stethoscope.
– Referral to a specialist
– A chest X ray
– A CT Scan of the patient’s chest
– Lung function testing (spirometry
– Test for TB

41. Diagnostic algorithm
Cough for ≥ 2 weeks in a dyspnoeic
patient of silica industry
Two samples of sputum
Negative for AFB Positive for AFB
Antibiotics for 10 - 14 weeks NSSP TB
X-Ray Chest – PA View if symptoms persist
“Snow Storm” appearance Consistent with TB lesion
v

42. Silicosis Treatment
• No cure for silicosis
• Treatment aims to relieve symptoms and
improve quality of life
• Exposure to silica: Reduce
• Smoking: Stop smoking
• TB surveillance: Regular test for TB
• Vaccination: Pneumococcal vaccination
• Long-term oxygen therapy, Bronchodilators,
antibiotics, Corticosteroid, a lung transplant,

43. Thank you

44. Prevention of silicosis

45. Control of the source
This aims at preventing or minimizing the use
or generation/release of a hazardous agent
(silica).
Identification and understanding of the hazard
creation/emission mechanisms; anticipate
hazards and avoid risky situations
Measures:
Substitution of materials and equipment,
Modification of processes, Wet methods, and
adequate work practices

46. Control at the transmission path
Measures should prevent hazardous agents
from being disseminated or propagated
Means:
Isolation: Perform the operation inside an enclosure,
Local exhaust ventilation: Remove the particles, as
they are generated thus preventing them to disperse
in the work environment and be inhaled,
Good housekeeping: Avoid dust accumulation and
formation of secondary sources

47. Control at the transmission path
• Engineering measures: Well designed exhaust
ventilation, proper installation and operation,
routine check up and well maintenance
• Otherwise it will not be efficient and may
even give an undesirable “false sense of
security”.

48. Control at the level of the worker
Measures: Adequate work practices,
education (including risk communication)
and training, personal hygiene and health
surveillance
Good work practices (always linked with
training) to eliminate or minimize hazards
even at their source.

49. Control at the level of the worker
Masks and helmets of good quality can
efficiently minimize entry of dust, well
adapted to the worker, comfortable, routinely
checked and well maintained.
Periodic monitoring of the work environment
and workers’ health, workers’ education and
periodic review are also considered to identify
and to prevent the medical problem of
workers if any.

50. Table of prevention and control
Levels Measures
Control of the
source
- Elimination
- Substitution of materials
- Substitution/modification of processes and
equipment
- Maintenance of equipment
- Wet methods
- Work practices
Control in the
transmission
path:
Isolation: - of the source (closed systems,
enclosures), - of workers (control cabins)
Local exhaust ventilation

51. Table of prevention and control
Levels Measures
Measures
related to the
worker:
- Work practices
- Education (risk communication) and training
- Personal hygiene
- Personal protective equipment
- Health surveillance
Other measures
related to the
work
environment:
- Lay-out
- Good housekeeping
-Storage, labelling
-Warning signs and restricted areas
-Environmental monitoring/alarm systems

52. Role of employer/factory
• Comply OEL of crystalline silica in the air (0.1
to 0.05 mg/m3
)
• Introduce engineering control measures like
exhaust ventilation, dust collection system,
water sprays, wet drilling, enclosed cabs, drill
platform skirts.
• 2. Conduct air monitoring at work places and
implement corrective action when silica levels
are excessive.

53. Role of employer/factory
• 3. Supply Vacuum cleaning equipment with
HEPA filters and wet sweeping instead dry
sweeping
• 4. Regular training and sensitization of
workers: Health effects, engineering controls
and work practices, maintenance of good
housekeeping
• 5. Provide respirators

54. Role of employer/factory
• Make pre-employment medical check up.
Provide medical surveillance with X-ray
(ILO/WHO rating competent)
• Report to compensation commissioner and
Chief Inspector for Occupational Health &
Safety in TB and silicosis
• Hang proper Signages to identify areas where
respirable silica dust is present for use of PPEs
• Do Forestation (by the employer authority)

55. Preventive strategy
• National level: Establish specific regulations,
enforce occupational exposure limits, Inspect
systematically;
• Apply technical standards and safety measures;
• Organize the reporting system on silicosis
occurrence
• Provide governmental advisory services to
industry and workers on the application of
preventive programmes and safe work
practices.

56. Enterprise level
Avoid the formation of silica-containing dusts;
use of engineering controls; comply exposure
limits and technical standards; Keep
surveillance of the work environment and
workers’ health; Use personal protective
equipment; Educate workers; Disseminate
technical information

57. Institutional
Provide collaboration between principal
stakeholders
• Governmental agencies such as Ministries of
Labour, Health, Environment, Industry, Mines,
Transport, Construction, Science and
Technology,
• Employers’ and Workers’ organizations; Non-
governmental organizations,
• Workers’ Compensation Board; Social
Security Institutions; Academic institutions

58. Programme implementation
• Establish a co-ordinating body or a steering
committee at the state level & maintain it
• Determine methods of operation
• Meet every six months for task
• Establish specific task forces
• Screen the susceptible population
• Manage the detected cases
• Apply preventive activities
• Monitor the activities and evaluate

59. Thank you

60. Monitoring and evaluation of SSP

61. Outcome (Impact)
Are the silica dusts generated as before?
Are the key outcomes established by the
preventive strategy being met?
Are over-exposures being reduced?
Are dust control technologies being
introduced?
Are health and hazard surveillance systems
established?

62. Process
Are the actions or processes supporting
prevention taking place?
Has there been appropriate training,
information dissemination, professional
certification (e.g., laboratories, Industrial
Health professionals, X ray classification using
the ILO 2000 System etc)?
Is the quality and quantity of workplace
inspections improving?

63. Administration
Is the program coordination and
administration effective and efficient?
Does steering committee discuss progress
in the SSP execution at least annually?
Does steering committee formulate
recommendations aiming at its further
improvement?

64. Survey Format
• Name:
• Address:
• Age yrs Sex: M / F
• Work place: Stone crushing factory / Quarry / other
• Type of work:
• Employment: Daily rate / Casual / Permanent
• Years of work (Duration):

65. Complaints if any
• Nature Yes (Write Y) No (Write N)
• Dry cough
• Cough with chest pain
• Cough with sputum
• Cough with blood
• Respiratory distress
• Fever
• Anemia
• Weight loss
• Loss of appetite
• Acidity
• Vision problem
• Headache
• History of TB

66. Treatment
• Having treatment Yes No
• Duration
• Treatment for what
• Treatment from where

67. Survey format
• Survey Area
• Survey date
• Name of Survey worker and designation
• Signature

68. Referral Card
• Name:
• Address:
• Age: yrs Sex: M / F
• Symptoms & signs
• Provisional diagnosis
• Treatment given and suggested
• Referred to (Doctor / Facility)
• Reason of referral
• Date of Referral
• Investigations suggested
• Further advice given Signature referring doctor

69. Monthly feedback form
• Name of District
• Survey period
• Distribution of workers and beneficiaries
Character Number
Health Workers (HW) No. of HW involved:
No. of HW present:
Screening of people No. of people screened:
No. of people eligible:
Persons with clinical findings No. of suspected cases:
No. of people screened:

70. Monthly feedback form
Distribution of HWs, beneficiaries, medical problems
Number of Health
Workers involved
Location (Block) Number (ASHA, ANM,
HA etc)
Persons screened Total Male Female
Persons
diagnosed with
disease
Total Male: Female
Type of disease Disease Male Female
Silicosis
Suspected
Probable:
Confirmed
Silico-Tuberculosis
Silicosis with other
co-morbidity

71. Monthly feedback form
Cumulative cases Silicosis
Suspected:
Probable:
Confirmed:
Silico-Tuberculosis
Silicosis with other co-
morbidity
Male Female
Referred for further
investigation &
treatment
Total Male Female
Other comments if any
CMOH Deputy CMOH II

72. Thank you