Construction dust can seriously damage the health of construction workers and if exposed for longer times can eventually even kill them. About 22,000 to 52,000 persons per year are dying due to inhaling polluted air in USA alone – most of whom are construction workers. In Great Britain, over 500 construction workers are believed to die every year from lung cancer. America and Europe have enacted rules to mitigate the effects of dust.
In India, though there are several regulations like the Factories Act, 1948, Mines Act, 1952, Metalliferous Mines regulation, 1961, and Building and Other Construction Workers (Regulation of Employment and Conditions of Service) Act, 1996 and Rules, they specify much higher limits of particulate matter and silica dust which are harmful to construction workers. Moreover, these limits are rarely imposed. The rules directed towards construction water disposal, plastic bags, or smoke emitted from chimneys of cement plants are good, but often present only on paper and rarely implemented.
In this article issues such as main causes of construction dust, its effect on workers, international rules to mitigate the problem, equipment that should be used, etc. are briefly discussed. Hope this will bring awareness within the building industry in India and start a movement towards mitigating the effects of construction dust.
Dr. N. Subramanian and Er. Vivek Abhyankar
Clean air, water, and food are the birthright of every person on earth and are considered basic necessities. Air pollution has become a growing concern in the world, with an increasing number of acute air pollution episodes in many cities worldwide. Both ambient (outdoor) and household (indoor) air pollution are considered the biggest environmental risks affecting health, and are responsible for about one in every nine deaths annually (WHO Report, 2016). More than 90% of air pollution-related deaths occur in low-and middle-income countries, mainly Asia and Africa, followed by low-and middle-income countries in the eastern Mediterranean region, Europe and Americas. Some places have air pollution levels several times higher than those considered safe by the World Health Organization’s (WHO) air quality guidelines.
According to WHO, in 2016, ambient/outdoor air pollution alone killed around 4.2 million people in the world, mainly from non-communicable diseases (see Fig.1), while household air pollution from cooking with polluted fuels and technologies caused an estimated additional 3.8 million deaths. According to WHO, air pollution is mainly responsible for non-communicable diseases (NSDs), causing an estimated 24% of all deaths from heart disease, 25% from stroke, 43% from chronic obstructive pulmonary disease, and 29% from lung cancer. Only one person in ten living in a city complies with the WHO air quality guidelines. Air pollution continues to rise at an alarming rate, and affects economies and the quality of life of people living in cities; it is now considered a public health emergency. Air pollution can also be used as a marker of sustainable development, as sources of air pollution also produce green-house pollutants (e.g. CO2).
Fig. 1 Deaths attributable to ambient (outdoor) air pollution in 2012 by country (WHO Report, 2016)
While a number of air pollutants are associated with significant mortality, including NOx, ozone, carbon monoxide, and sulphur dioxide, particulate matter (PM2.5) is most commonly used as the proxy indicator of exposure to air pollution, and has been most closely studied (WHO Guideline, 2005). Particulate matter consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. The major components of PM are sulphates, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water. The most health-damaging particles are those with a diameter of 10 μm or less, which can penetrate and lodge deep inside the lungs. Both short- and long-term exposure to air pollutants have been associated with health impacts. Small particulate matter (PM2.5) pollution has health impacts even at very low concentrations. WHO recommended guideline values are shown in Table 1, above which there will be concern for human health. Fig 2 shows the annual median concentration of PM2.5, in μg/m3, in different countries of the world as per WHO.
|Table 1 Limits of particulate matter, affecting health of humans|
|Size of particulate matter||Annual mean||24-hour mean|
|PM2.5||10 µg/m3||25 µg/m3|
|PM10||20 µg/m3||50 µg/m3|
Fig. 2 Global map of annual median concentration of PM2.5, in µg/m3 (WHO Report, 2016)
Air pollution in India is affecting not only the health of people in big cities like New Delhi, Mumbai and Kolkata, but also national monuments like the Taj Mahal, which is losing its luster and colour due to increasing industrial pollution (In addition to air pollution, India is experiencing water pollution of several rivers including river Ganga, due to unauthorized discharge of industrial wastes and raw sewage).
Fig.3 Most polluted megacities with PM10 concentrations (www. timesofindia.indiatimes.com)India tops the world in bad air quality and has 14 out of the 15 most polluted cities in the world in terms of PM2.5 concentrations, the worst being Kanpur with a PM2.5 concentration of 173 μg/m3, followed by Faridabad (172 μg/m3), Varanasi (151 μg/m3) and Gaya (140 μg/m3). In 2016, Delhi’s PM2.5 annual average was 143 μg/m3, more than three times the national safe standard, while the PM10 average was 292 μg/m3, more than 4.5 times the national safe standard, as shown in Fig. 3 (in comparison, Beijing, China’s PM2.5 concentration was only 73 μg/m3).
According to health experts, PM10 particles can penetrate the lungs and may even enter the bloodstream. It can cause heart disease, lung cancer, asthma, and acute lower respiratory infection (see section on Health risks). The pollutions responsible for this kind of pollution are of various types – Industrial flues and wastes, medical wastes, IT wastes, bio-degradable wastes (food), construction wastes, etc. We will limit the scope to pollution due to construction wastes and specifically ‘construction dust’.
Causes / Sources of Construction Dust
Many of us living in busy metros like Delhi, Mumbai, Pune, Kolkata, Chennai, or Bangalore might have experienced the effects of construction dust in the form of sneezing, heaviness in breathing or coughing, reddening or itching eyes, etc. In rapidly industrializing and urbanizing cities, smoke and dust are created due to the exhaust fumes from vehicles, smoke from factories, and dust from construction sites. According to Rakesh Kumar, Director, National Environmental Engineering and Research Institute (NEERI), the main factors contributing to Mumbai’s high air pollution (64 μg/m3 of PM2.5 and 104 μg/m3 of PM10 levels) is construction activity (which accounts for 30% of dust particles), followed by vehicular emissions. In addition, natural dust also plays a part.
Fig.4 Dust generated during drilling and grinding
Reliable statistics are not available for India, but several industries are known to expose their workers to silica dust. Dusts that pose greater risk for workers are: (a) Construction dust [sandblasting, rock drilling/grinding (Fig. 4), masonry work, jack hammering, tunneling, road milling/laying, mixing of cement and concrete involving fine particles of cement, fly ash, and silica fumes)]; (b) Mining dust (produced while cutting or drilling through sandstone and granite); Stone crushing dust (produced while making aggregates/manufactured sand for concrete or roads); (c) Agate polishing dust, (d) Dust due to Cement/brick manufacturing (it is interesting to note that the Central Government is planning to ban use of burnt clay bricks in its construction projects across the country); (e) Foundry dust (grinding, mouldings, shakeout, core room); (f) Ceramics, clay, and pottery dust; (g) Stone cutting/sawing dust (abrasive blasting, chipping, grinding) (Fig. 5); and (h) Glass manufacturing dust.
Fig. 5 Dust generated during sawing
Fig.6 Dust generated during demolition of old structuresIn addition, some mills grind silica-containing rock into a fine powder that is used in some industrial applications. Agriculture in many areas is also linked to silica exposure (http://www.okinternational.org). The drilling / sawing of timbers, tiles, stones, glass, metals, asbestos, etc., generate very fine and extremely hazardous dust. Huge amounts of fine dust is also generated and inhaled in demolition sites (Fig. 6), excavations or sites where rock mass is blasted/broken, dry sand is loaded/unloaded, dried bentonite mud is used during piling works, etc. Yet another source of dust generation is the mud sticking to the tyres of construction vehicles. Such vehicles, (if tyres are not washed regularly) spread the mud on city roads, which gets converted to dust, after drying.
Sand blasting is another activity that could generate loose dust if done without proper shed (Fig. 7).
Fig. 7 Sand blasting in open (left), sand blasting shed (right)
Types of Dust
In many of the above activities, in addition to dust, noise and vibrations are generated, which increases the annoyance of the common public. The three main types of dust generated due to these activities are (http://www.hse.gov.uk/pubns/cis36.pdf):
- Silica dust: Silica dust is created when workers are dealing with materials containing crystalline silica, such as sand, stone, rock, sandstone, brick, concrete, and mortar (also known as respirable crystalline silica or RCS).
- Wood dust: Wood dust is generated when working with softwood, hardwood, and wood-based products such as medium density fiberboard (MDF), and plywood.
- Lower toxicity dusts: This type of dust is created when working with materials containing little-to-no silica, such as gypsum (in plasterboard), limestone, dolomite and marble.
As per www.osha.gov, exposure to respirable crystalline silica can occur during common construction tasks, such as using masonry saws, grinders, drills, jack-hammers and hand-held powered chipping tools; operating vehicle-mounted drilling rigs; milling; operating crushing machines; using heavy equipment for demolition or certain other tasks; and during abrasive blasting and tunneling operations. In USA alone about two million construction workers are exposed to respirable crystalline silica in over 600,000 workplaces.
In India, there are about 3 million workers formally employed in the formal economy with potential exposure to silica dust. Further, approximately 8.5 million more work in construction and many more in the informal industries with exposure to silica dust. Thousands of these workers develop silicosis every year and die directly from it, or from secondary causes such as TB or lung cancer. However, relatively few of these deaths are recorded as being caused by silicosis or as being work-related in national statistics (http://www.okinternational.org).
Fig. 8 Dust particle deposition in the respiratory systemAnyone who breathes these dusts should know the damage they can do to the lungs and health. Fig. 8 shows the deposition of dust particles in the respiratory system, depending on the size of the dust particle.
As mentioned, the main dust-related diseases affecting construction workers are:
- Lung cancer
- Chronic obstructive pulmonary disease (COPD)
Assuming a daily average of PM10 concentration in 2000 as 23.8 μm/m3, these particles were estimated to kill 22,000 to 52,000 people per year in the USA alone (Beiser, 2018 and Mokdad, et al., 2004). Every year in Great Britain, over 500 construction workers are believed to die from lung cancer caused by silica dust alone (IOSH,2014). Recently, the Global Burden of Disease (GBD) Study established that ambient outdoor air pollution due to particulate matter <2.5 μm (PM2.5), was the fifth ranking global risk factor in 2015, causing 4.2 million deaths annually, with cardiovascular deaths accounting for most of these deaths (Münzel et al.,2018)-See Fig.9.
Fig. 9 Deaths attributable to ambient particulate matter pollution by year and cause (Münzel et al., 2018).Nano-sized ultrafine titanium dioxide (TiO2) or zinc oxide (ZnO) has been found to cause inflammation of the lungs and lung cancer in lab animals. The National Institute for Occupational Safety and Health (NIOSH) has determined that ultrafine TiO2 should be considered a potential occupational carcinogen. OSHA has no specific regulation or permissible exposure limit (PEL) for any engineered nano-material. However, NIOSH has a recommended airborne exposure limit (REL) for ultrafine TiO2 of 0.3 mg/m3 as a time-weighted average (TWA) concentration for up to 10 hours/day during a 40-hour week (Singh, 2016).
The health hazards due to the demolition of buildings must be specially mentioned. When a building is demolished, the mechanical action of crushing creates particulates of dust from the materials used in the building. These particulates enter the air and spread throughout the environment. Other machines that are used repeatedly in the worksite may further circulate these particulates. Atmospheric conditions like wind can worsen the spread of dust (Badiali, 2016).
Older buildings may contain now banned materials like lead (which was used in lead-based paints and water pipes), asbestos (which has been proven to cause fatal diseases such as asbestosis, pleural disease, and lung cancer), and mercury (used in gas pressure regulators, boiler heating systems, and thermostats). There are other less well-known potential health hazards caused by demolition of buildings. Arsenic and heavy metals like chromium, copper, iron, and manganese, which are harmful to humans, might have been used in pressure treated wood manufactured before 2003. According to the Massachusetts Water Resource Authority “The amount of mercury present in one mercury thermometer is enough to pollute 5 million gallons of water” (Badiali, 2016). Benzene, a chemical related to natural gas, is also found harmful to humans.
In 1971, the Occupational Safety and Health Administration (OSHA) of USA developed a standard, which limits worker exposure to silica to an average of 250 μg/m3 over eight hours. After continued research and discussion, OSHA has now issued an updated silica standard for construction which limits the respirable silica exposure to workers to an average of only 50 μg/m3 over eight hours (29 CFR 1926.1153, 2016). Employers who do not comply with the requirements of this standard could receive financial penalties from OSHA. Serious or other-than-serious penalties could attract up to $12,934 each-and repeat offenses or violations deemed by the agency to be willful in nature are subjected to financial penalties of up to $129,336 each (Dobson, 2018).
OSHA’s Table 1 (similar to Table 2 presented here, based on U.K. standards) also shows exposure control techniques for 18 common construction activities. Most tasks in Table 2, especially when done indoors, require a respirator with an assigned protection factor (APF) of 10 or 25. Table 3 shows the protective equipment that may provide APF of 10 and 25. In addition, OSHA stipulates that the worker must be medically evaluated every 30 days, which may include (a) A health history, and (b) A physical examination (chest X-ray, pulmonary function test, and TB skin test).
Employers will be responsible for: (1) Training employees, (2) Assuring that they have the correct tools (respirators, tools with integrated water systems, and tools with integrated High-Efficiency Particulate Air (HEPA) vacuum systems), and (3) Assuring that personnel who need medical evaluations are identified and receive them as mentioned in the standard. Project leaders have to understand that there is an additional cost involved to the tune of $250 to $500 per worker per month for such medical evaluations.
|Table 2 Controls for common high-risk tasks (http://elcosh.org)|
|Task||Engineering and Work Practice Control Methods||Control the dust by using|
|Cutting concrete kerbs, blocks and paving with a cut-off saw||
|Chasing concrete and raking mortar||
|Cutting roofing tiles with a cut-off saw||
|Scabbling or grinding with hand-held tools||
|Short-duration drilling (15–30 min) with hand-held rotary power tools||
|Drilling holes with handheld rotary power tools as a ‘main activity’||
|Dry coring||Limit the number of holes during design/planning itself||
|Wet coring||Limit the number of holes during design/planning itself||
|Using a hand-held breaker in enclosed spaces with limited ventilation||
|Abrasive pressure blasting||
|Soft strip demolition||
|Removing small rubble, dust and debris||
|Cutting wood with power tools||
|Sanding wood with power tools||
|Sanding plasterboard jointing||Using other finishes/systems||On-tool extraction using an H, M, or L Class extraction unit|
|RPE-Respiratory protective equipment
1RPE for wood dust
The risk from wood dust is specific to the type (species) of wood. In general, RPE with an APF of 20 is appropriate; particularly for higher residual dust levels, such as when sanding, and for all work with more toxic woods such as hardwoods, western red cedar and MDF. RPE with an APF of 10 is suitable for work with less residual dust and when the wood is of lower risk (e.g., pine).
In the UK, the Health and Safety Executive (HSE) has set a maximum exposure limit (MEL) for silica dust of 0.3 mg/m3 (averaged over eight hours). In addition, in some countries like the USA, there is a requirement that all products containing more than 0.1% silica should carry cancer warnings. There is no such proposal for reducing permissible limit for silica dust or for labeling products with silica in India at present. There is no statute in India specifically dealing with silica and silicosis and the subject is covered by various Occupational Health and Safety legislations dealing with different economic activities. In general, Indian regulations like the Factories Act, 1948, Mines Act, 1952 and Metalliferous Mines regulation, 1961, and Building and Other Construction Workers (Regulation of Employment and Conditions of Service) Act, 1996 and Rules, specify the Permissible Exposure Limit (PEL) for quartz as 0.1 mg/m3, which is less stringent than the current OSHA limits. Moreover, construction in India is not an organized sector and in several Indian construction sites this limit is found to be crossed to a great extent without any prejudice.
Reducing the Effects of Construction Dust
Three key steps that have to be considered while controlling the dust and its effects are (also see Wu, et al. 2016):
- Assessment of the risks: It is necessary to assess the risks linked to the work and materials (see Table 2 for the high-risk tasks). The tasks that involve more energy will result in higher risks. High-energy tools such as cut-off saws, grinders, and grit blasters could produce considerable dust in a very short time. Workers, who are doing the same kind of work daily (which involve dusts) or those in longer shifts, will be more affected by dusts. In general, more dust will build up in enclosed spaces.
- Controlling the risks: The amount of dust can be controlled by using (a) Water, which damps down the dust clouds (see Fig. 10). To be effective, enough water should be supplied at the right quantities during the entire operations. Just wetting the material beforehand is not sufficient, and (b) On-tool extraction, which removes dust as it is being produced (see Fig. 11). Such systems consist of several parts: the tool, capturing hood, extraction unit, and tubing. The proper system should be used for any application, as they are marked as H (High), M (Medium) or L (Low) Class filter units. A general commercial vacuum may not serve the purpose.Fig. 10 Saws fitted with inexpensive water-spray dust suppression equipment, result in a liquid slurry which is much easier to control (www.pavingexpert.com/saws_01.htm)Fig. 11 Vacuum dust extractor muzzle (www.pavingexpert.com/saws_01.htm)In addition to water or ‘on-tool extraction’, respiratory protection equipment (RPE) has to be used (Table 2). The RPE used should be adequate for the amount and type of dust (Table 3). RPE has an assigned protection factor (APF) which shows how much protection it gives to the wearer. For the normal level of construction dust, APF of 20 may be adequate. (This means that the wearer breathes only one twentieth of the amount of dust in the air). Disposable masks or half masks should be worn correctly and may become uncomfortable if worn for long periods. Moreover, face fit testing is needed for tight-fitting masks. According to OSHA, anyone using tight-fitting masks also needs to be clean shaven. Powered RPE should be recommended, when people are working for more than an hour without a break. As RPE is the last line of protection, there should be proper justification for using it alone, without other protection systems.
The above systems could be combined and other controls, such as (a) limiting the number of people near the work, (c) rotating the workers, (c) using enclosed space to work to avoid dust escaping/spreading, (d) using mechanical ventilation to remove dusty air from the work area if work is done indoors, and (e) using work clothes that do not retain dust. In addition, the workers should be properly trained to do the job and using controls.
- Review (the controls): It is also important to review whether the controls used are effective by carrying out dust exposure monitoring, cleaning, storing, and maintaining the equipment, and supervising the workers.
In most industrialized countries, the construction industry is one of the most significant industries in terms of contribution to gross domestic product (GDP). It also has a significant impact on the health and safety of workers. The construction industry is both economically and socially important. In construction, workers perform a great diversity of activities, each one with a specific associated risk. The worker who carries out a task is directly exposed to its associated risks and passively exposed to risks produced by nearby co-workers. In India, the profit margins of the construction sector are very slick as compared to the investments; mostly illiterate village farmers join the construction sector as workers/foremen. Due to illiteracy, there is no awareness about environmental rules/regulations and human rights; the workers are highly deprived and under privileged in most of the construction companies.
No one really cares about the health and safety of construction workers in India and the maximum protection given is the helmet. As mentioned earlier, those engaged as construction workers are uneducated and hence may not even be aware of the dangers, and the materials they are handling, which may pose health hazards. In addition to solid dust particles in the fumes, there may be gases, which are collectively called VOCs (volatile organic compounds), when they are handling paints and other petroleum-based products.
Several products like lime cause irritation to the eyes and skin and are injurious. Handling of very fine products like cement, fly ash, silica fume is also dangerous if the workers are not wearing masks. The smog in the streets not only has dust but also exhaust gases from buses, cars and autos. The exhaust from auto rickshaws is especially very bad for health as the fuel is not burnt properly. For a long time, India was having a policy of pricing diesel lower than that of petrol, though it is more dangerous to health than petrol. The current government recently corrected that mistake. Some fumes are colourless and odourless, but at the same time lethal (example: carbon monoxide, which can cause headache and dizziness, even coma and death).
In India, reliable statistics are not available on how many people are affected by dust allergy, asthma, and other diseases caused by PM, but there are many industries where exposures to silica dust are known to exist. National TB control efforts do not include silica dust controls. The enforcement agencies in India have limited manpower and resources to measure silica dust in the work environment. They also do not have access to proper sampling equipment and accredited analytical laboratories. In addition, there is lack of facilities for diagnosis of silicosis and lack of awareness among workers, employers, and even among medical practitioners.
The socio-economic context of the potential victims, (including those under bonded labor) has to be considered while designing national strategies for prevention and control of such diseases. In this context, it is important to note that there are several temporary workers or those who are employed through middle men (who are not licensed contractors) for whom acts such as Factory Act and ESI Act are not applied. The report by OK International discusses these as well as other lacunae in the Indian legislative provisions relating to dust exposure and proposes several recommendations to rectify the situation in India (OK International report, 2009).
The authors wish to acknowledge that the images used in this paper are derived from various internet sources.
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Dr. N. Subramanian earned his PhD from IIT, Madras in 1978. He worked in Germany as Alexander von Humboldt Fellow during 1980-82 and 1984. He has 40 years of professional experience which includes teaching, research, and consultancy in India and abroad. Dr. Subramanian has authored 25 books and more than 240 technical papers, published in International and Indian journals and conferences. Elected as one of the distinguished Alumnus of the Anna University, he has won the Lifetime Achievement Award from the Indian Concrete Institute (ICI), the Tamil Nadu Scientist Award, and the ACCE(I)-Nagadi best book award for three of his books. He served as the past National Vice-President of ICI and ACCE (I). He is also in the editorial/review committee of several journals
Er. Vivek G. Abhyankar, C. Eng. (India), is currently DGM (Design), L&T TIIC and has more than nineteen years of professional experience in planning and design, detailing of various enabling and permanent works in Concrete and Steel. He was also a visiting faculty for Graduate and Post-Graduate students in Structural engineering at VJTI and SPCE. He is a certified structural engineer of MCGM. Life member of various professional bodies and contributed in more than 25 technical papers and 3 chapters in books and guided more than 10 M. Tech. and AMIE projects.