Epidemiology silicosis

Epidemiology - Silicosis

Dr. Palash Das, MDAssociate Professor, Community Medicine

CMSDH, Kamarhati, Kolkata - 700058

Stone Crusher

Quarry

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.

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)

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

Magnitude of the problem

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


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.


Purulia: Balarampur, Barabazar, Manbazar-I, Manbazar-II, BundwanBurdwan: Salanpur, Barabani, Jamuria, Ranigunj, Asansol Municipal Corpn., Faridpur-DurgapurBirbhum: Muraroi-I, Nalhati –I, Rampurhat-I, Mahammad Bazar, Bankura: Saltora, Mejia, Borjora, Chhatna, GangajalghatiPaschim Medinipur: Binpur I/II, Jhargram, Gopiballavpur I/II


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).

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).

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.

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

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.

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

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

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

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.

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

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.

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.

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.

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;

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)

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.

Some recognized types of silicosis

• Simple chronic silicosis:• Sub-acute silicosis: • Accelerated Silicosis:• Acute Silicosis:• Progressive massive fibrosis (PMF):

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

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:

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).

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.

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/+

ILO ClassificationMajor 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.

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)

Normal Radiograph

Small Parenchymal Opacities in Coal Workers' Pneumoconiosis

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

Pneumoconiosis

Possible complications

• Lung Cancer• Progressive massive fibrosis• Respiratory failure• Tuberculosis• Further problems: Chest infections,

pulmonary hypertension, heart failure, arthritis, kidney diseases, COPD

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).

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.

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

Diagnostic algorithmCough 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

Spirometry, CT scan of chest NSN TB Silicosis

v

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,

Thank you

Prevention of silicosis

Control of the sourceThis 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

Control at the transmission pathMeasures 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

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”.

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.

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.

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

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

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.


• 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


• 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)

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.

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

InstitutionalProvide 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

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

Thank you

Monitoring and evaluation of SSP

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?

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?

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?

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):

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

Treatment• Having treatment Yes No

• Duration

• Treatment for what

• Treatment from where

Survey format• Survey Area

• Survey date

• Name of Survey worker and designation

• Signature

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

Monthly feedback form• Name of District• Survey period• Distribution of workers and beneficiaries

Character NumberHealth 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:

Monthly feedback formDistribution of HWs, beneficiaries, medical problems

Number of Health Workers involved

Location (Block) Number (ASHA, ANM, HA etc)

Persons screened Total Male FemalePersons diagnosed with disease

Total Male: Female

Type of disease Disease Male FemaleSilicosisSuspectedProbable:ConfirmedSilico-TuberculosisSilicosis with otherco-morbidity

Monthly feedback form

Cumulative cases SilicosisSuspected:Probable:Confirmed:Silico-TuberculosisSilicosis with other co-morbidity

Male Female

Referred for further investigation & treatment

Total Male Female

Other comments if any

CMOH Deputy CMOH II

Thank you

Health & Medicine

Epidemiology silicosis