Silicosis is one of the most important occupational health illnesses in the world. It is a progressive lung disease caused by inhalation of silica over a long period of time. Silicosis is characterized by shortness of breath, cough, fever and bluish skin.
Silica (SiO2 / silicon dioxide) is crystal-like mineral found in abundance in sand, rock, and quartz. Silicosis occurs most commonly as an occupational disease in people working in the quarrying, manufacturing and building construction industries. It is also reported from population with non-occupational exposure to silica dust from industrial as well as nonindustrial sources.
Exposure to large amounts of free silica may not be noticed because silica is odourless, non-irritant and does not cause any immediate health effects, but long-term exposure to crystalline silica-containing dust is associated with pneumoconiosis, and progressive massive fibrosis of the lung (PMF), lung cancer, pulmonary tuberculosis, and other lung diseases and airways diseases. In India, more than 10 million workers are at risk of silicosis.
In 1999, the Indian Council of Medical Research(ICMR) reported that around 3.0 million workers are at high risk of exposure to silica; of these, 1.7 million work in mining or quarrying activities, 0.6 million in the manufacture of non-metallic products (such as refractory products, structural clay, glass and mica) and 0.7 million in the metals industry. There are also around 5.3 million construction workers at risk of silica exposure.
In India silicosis is prevalent in Gujarat, Rajasthan, Pondicherry, Haryana, Uttar Pradesh, Bihar, Chhattisgarh, Jharkhand, Orissa and West Bengal among the workers of construction and mining. Prevalence of silicosis in India ranges widely from 3.5% in ordnance factory to 54.6% in the slate-pencil industry and this variation in prevalence is due to the silica concentrations in different work environment, duration of exposure and the job demands.
Silicosis is an incurable condition with its potential to cause permanent physical disability. As there is no effective specific treatment of silicosis, the only way to protect workers’ health is control of exposure to silica-containing dusts and to detect cases early through monitoring of currently and formerly exposed workers along with proper management to reduce disability.
Factory Act of India (1948) mandates a well ventilated working environment, provisions for protection from dust, reduction of overcrowding and provision of basic occupational health care. The main challenge of eliminating silicosis in India is in the informal, unregulated sectors of industry which do not fall under the control of the Factory Act of India. The National Human Rights Commission (NHRC) also emphasized for regulation of working environment, protective equipment to workers with proper health education.
IEC Booklets about silicosis in Hindi by ‘National institute of occupational health’(NIOH), India may be seen at:
Silicosis is characterized by shortness of breath, cough, fever and bluish skin.
Silicosis can present in three different forms as acute, accelerated and chronic.
Chronic silicosis: It is most common form of the disease, generally develops after 10 or more years of exposure to low levels of crystalline silica. There is an abnormal chest X-ray in the beginning and then person will slowly develop a cough and breathing difficulty.
Accelerated silicosis: This form of silicosis tends to show up five to 10 years after exposure to higher levels of crystalline silica.
Acute silicosis: It occurs with short-term exposure to very high levels of crystalline silica. Person experiences fever and sharp chest pain along with breathing difficulty. These symptoms can appear suddenly. Acute silicosis can lead to death with in few months.
Symptoms developed due to scarring of lung tissues known as pneumoconiosis.
Silicosis is caused by exposure to crystalline silica. Silica (SiO2 / silicon dioxide) is combination of silicon and oxygen. Silicon is very reactive, does not remain in the element form but combines either with oxygen and forms free silica (SiO2) or with oxygen and other elements and forms silicates such as asbestos. Silica and silicates constitute the bulk of most kinds of rocks, clays and sands.
Crystalline silica is found in rock, brick, and concrete. Grinding, sawing, crushing, or drilling of these materials produce a fine powder that causes serious respiratory problems.
The silica milling industry provides basic raw material to a large number of other industries such as silica flour is used in glass and high quality ceramics manufacturing, as abrasive cleaner, inert filler in paint and rubber industry, in making of toothpaste, scouring powder, abrasive soaps, chemical filtration, metal polishing. These dust particles, mostly 10 microns in size and smaller, are too small to see, but can penetrate to the deepest part of the human lung when inhaled. Chronic inhalation of such respirable crystalline silica (RCS) dust can lead to severe lung disease, such as silicosis and lung cancer. Further silicosis increases the risk of developing tuberculosis. RCS exposure has also been linked to kidney and auto-immune diseases.
Occupational exposure to silica occurs at workplaces in factories like quartz crushing facilities (silica flour milling), agate, ceramic, slate pencil, glass, stone quarries and mines. Silica flour in India is produced by small factories.
Non-occupational exposure to silica- Silicosis is also reported in population with Non-occupational exposure from industrial sources and non-industrial sources.
Similarly, the people who shape and polish the agate stones in workshops in their homes are found to suffering with silicosis along with their families and neighbors.
Crystalline silica” or “quartz” is a potent fibrogenic substance. Silica dust does not have any warning signal, because it is tasteless, odourless and non-irritant. Therefore, a large amount of dust may be inhaled by a worker without any warning sign. Various occupations where earth’s crust is disturbed can cause silicosis.
Person working in an occupation with exposure to inhaled silica or having non occupational exposure to silica with the symptoms like cough, phlegm, or breathing difficulty, or no symptoms (even working for long times) should be evaluated for silicosis.
Diagnosis of silicosis can be done with detailed occupational history, physical examination by health-care provider (decreased chest expansion, diminished intensity of breath sounds, areas of hypo resonance and fine to medium crackles in lung area, and tachypnea) and different investigations for the confirmation of silicosis. Investigations include:
As there is no cure for silicosis, prevention is still the best way to avoid the disease. Once diagnosis of silicosis is confirmed, management depends on the degree of lung damage.
Mild to moderate cases may need medicines to decrease sputum production, such as inhaled steroids and inhaled bronchodilators to relax the air tubes. While in severe cases people may need urgent treatment with oxygen and support for breathing.
Once the disease advances, the management is similar to many other chronic lung diseases and needs a multidisciplinary or team approach.
To keep the disease from getting worse, it is important to stay away from any additional sources of silica and other lung irritants, such as indoor and outdoor air pollution, allergens and smoke, and individual should be moved to a work position with no risk of exposure or counselling for changing of occupation may be required. Oxygen support or other ways to manage chronic lung failure, like the use of noninvasive ventilator devices, may be needed. In severe cases lung transplant may be considered.
Advice to silicosis patient:
Prevention of silicosis is an important step in the field of occupational health. The best way to prevent silicosis is to identify workplace activities that produce crystalline silica dust and then to eliminate or control the dust.
An effective silicosis preventive strategy is based on the primary and secondary prevention approaches.
Primary prevention includes the control of silica hazard at source by the engineering methods of dust control. If occupational exposure to dust is avoided, silicosis will cease to occur.
Secondary prevention includes the surveillance of the working environment to assess the adequacy of dust control measures, exposure evaluation to assess the health risk for workers, and surveillance of the workers’ health for early detection of the disease.
Primary prevention aims at interrupting the “chain of exposure” - the process by which hazardous agents are formed/used and transmitted from their source to the receptor (worker). The hierarchy of controls is: control of the source, control at the transmission path, control at the level of the worker.
Control of the source-
Control of the source aims at preventing or minimizing the use or generation/release of a hazardous agent by:
Control at the transmission path: Whenever source control is not sufficient, measures should be taken along the transmission path to prevent hazardous agents from being disseminated and thus reaching workers, such methods are:
Control at the level of the worker includes indispensable measures such as adequate work practices, education (including risk communication) and training, personal protective equipment, personal hygiene and health surveillance.
Workers should use personal protective respiratory equipment as suggested by NIOH or other safety equipment experts. The dust masks are of little value when the dust concentrations are high as the dust particles will clog the pores in the filter resulting in a choking sensation and discontinuance of the use of masks by workers and also the masks are not suited for hot and humid climate. Respirators should be used along with other effective dust control measures.
Any person who works in the industries with exposure to inhaled silica should get regular health checkups and should be monitored for signs and symptoms of lung disease. The periodical medical examination of workers and the dust measurements should be integrated to evaluate the change in morbidity.
Relocation of industry from residential area to industrial area may be indicated to prevent exposure to general population.
Recommendations to prevent development of silicosis:
Activities to strengthen occupational health in India:
Factory Act of India (1948): This Act mandates a well ventilated working environment, provisions for protection from dust, reduction of overcrowding and provision of basic occupational health care. Silicosis is a notified disease under the Mines Act (1952) and the Factories Act (1948).
Construction Industry Development Council (CIDC): The planning commission, Government of India (now Niti Aayog) jointly with the Indian construction industry has set up CIDC to take up for the development of the Indian construction industry.
Ministry of Health and Family Welfare Government of India is supporting NIOH to develop the best possible technique for prevention and control of silicosis in agate workers and quartz cutting industries.
Silicosis health-care units have been established in silicosis-risk districts by the states, where free chest X-ray and pulmonary function tests are done. Regular inspections are made to industries that use silica, with active involvement of nongovernmental organizations (NGOs) to ensure proper monitoring.
Dust control technique for prevention of pneumoconiosis by NIOH- click here