Abstract
Airborne hazards in the workplace cause illness and fatalities when dust and chemicals are inhaled at a workplace (UKHSE 2015). Besides breathing in airborne dust, another danger is that explosions start when dust ignites from sparking machinery especially from circular saws (Hedlund et al. 2014). The amount and type of airborne dust is regulated by the HSE. The Quantitative Risk Management Framework was identified as practical method for evaluating and finding solutions to control airborne dusts that cause explosions and health problems. Another evaluation tool is the Control Banding Tool that was developed specifically to assess the risk of small diameter dust particles during the welding of stainless steel. Case studies were reviewed and showed that the Local Exhaust Ventilation (LEV) systems are successful in removing airborne dust. LEV is an engineering control that works better than administrative controls and is safer than personal protective equipment (PPE). PPE is the least desired solution to hazardous problems in the workplace (NIOSH, 2013).
1.0 Ensuring Worker Safety from Airborne Dust and Dust Explosions
1.1 Introduction
Airborne contaminants in the workplace occur in gaseous form or as aerosols (WHO 1999a) Aerosols are airborne dusts, sprays, mists, smoke and fumes (WHO 1999a). Employers are responsible for health hazard reduction and must provide and maintain safety precautions (UK HSE 1974; UK HSE 1999; UKHSE 2013). Inhalable dust is defined by BS EN 481 1993 as “airborne material which is capable of entering the nose and mouth” (UK HSE 2002, p, 3). Two categories cover airborne dust; organic (such as wood) and inorganic (such as stainless steel) (HSE 2013). Sawing wood and grinding stainless steel as well as sanding and polishing are typical sources causing airborne dust (Garcia et al. 2014; NIOSH 2013).
Control of Substances Hazardous to Health Regulations (COSHH) is the section of the UK Health and Safety Executive laws for workplace safety of atmospheric contaminants. Approximately 13,000 deaths from lung disease and cancer were reported in 2015 due to dust and chemicals inhaled at UK workplaces (UKHSE 2015). Wood dust exposure causes nasopharngeal cancers and the dust fills the nasal cavity inhibiting breathing (Binazzi et al. 2015; Siew et al. 2015). ). Resin dust from sanding, sawing wood or particle board is considered hazardous because formaldehyde is an ingredient in the resin (HSE 2013).
Explosions and fires occur when wood or metal dust ignites from sparking machinery especially from circular saws (Hedlund et al. 2014). Work place hazardous dust is defined as “small solid particles, conventionally taken as those particles below 75 μm (micrometer) in diameter, which settle out under their own weight but which may remain suspended for some time” (WHO 1999). Welders are at risk from nanoparticles of dust, which have “a considerably weak . . . gravity field; the size is two or three dimensions lower than 100 mm” (ASTM 2007 cited by Albquerque eta l. 2015)
1.2 Health Risks and Regulations
Occupational asthma, rhinitis and allergies; with symptoms of “fever, cough, and worsening breathlessness and weight loss” are health risks and so is cancer caused by toxic woods that are “respiratory sensitizers” (UKSHSE 2013, pg. 1). Risk is high for pulmonary diseases; the dust passes from the lungs through the body and can cause liver diseases (UK HSE 2012). Particles between 0.5 to 7 microns in diameter are considered the most hazardous because the dust particles land in the bronchiole or alveoli and become absorbed into the body (COSHH 2016). Wood dust exposure causes nasopharngeal cancers and the closure of the nasal cavity (Binazzi et al. 2015; Siew et al. 2015).
Carpenters and furniture builders are at risk from inhaling “finely divided” . . . “a known human carcinogen” (Yuan et al. 2014; NTP 2014). Hardwood airborne dust is considered toxic (UK HSE 2002). COSHH Regulations 2000 assigned soft/hard woods workplace exposure limits of not more than 5 mg/m3 per eight hour work shift (HSE 2002). “Cumulative exposure to wood dust” causes higher risk for lung cancer (Vallieres et al. 2015, p. 9). Gioffre et al. (2011, p. 161) measured worker exposure in six Italian wood factories noting that different wood types cause “complex mixtures of dusts and biological agents with various health risks.”
Explosions and fires occur when wood or stainless steel dust ignites from sparking machinery often from circular saw use (Hedlund et al. 2014). COSHH) Regulations 2002 are expected to be followed by industries and includes small business employers of woodworkers to protect them from “dust and sparks from (an) abrasive wheel” (UK HSE 2012, pg. 5).
1.3 Case Studies
The furniture and fixtures industry makes up approximately 24 percent of total dangerous global dust incidents; the accidents were caused by wood dust (Khan and Buiyan 2013). The airborne dust concentrations ranged from 0.1 to 2.2 mg/m3; in particle-board mills the range was from 0.4 to 3.4 mg/m3 and in furniture factories the range was from 0.1 to 1.5 mg/m3 (IARC 1995:228-229).
Wood dust exposure was reduced in two furniture factories by a factor of two indicating that the managers focused on reduction at “the highest exposure” levels (Schlunssen et al. 2001, p. 167). Researchers concluded that factory size does not influence dust exposure management (Schlunssen et al. 2001). The average dust diameter was found to be very low; the “mean was equal to 1.17 ±0.62 mg/m3” within the “range of 0.17 to e.44 mg/m3” in 54 Danish furniture factories (Schlunssen et al. 2002: 23). Therefore after only four to seven hours breathing was allowed in order to protect the nasal cavity of workers (Schlunssen et al. 2002).
Local Exhaust Ventilation (LEV) cleans the air by collecting dust with a hood, ducts and fans allows the dust to be moved into a collection repository (UK HSE 2011; Pocock 2012). In some LEV designs the dusty air is filtered and returned to the work environment (UK HSE 2011; Pocock 2012). LEV can remove 90 percent of the dust with the appropriate “vacuum extraction source” (Pocock 2012). Regular maintenance and monitoring are required for LEV systems to ensure optimum air flow and performance (Hasan et al. 2012). Inthavong, Tian and Tu (2009, pg. 125) found that ventilation design on the “roof (with) an angled outlet provided (the) greatest total particle clearance and a low number of particles” for workers carrying out woodturning with circular saws. Khalaji et al. (2011) recommends a centrally positioned dust collection system in order to save money.
1.4 Management Controls
The WHO (1990, p. xxi) organized the Prevention and Control Exchange (PACE) in order to create an exchange of awareness, information sharing creating the political will for hazard prevention and control and to aid nations in their efforts to “strengthen and develop . . . technical and managerial capacities . . . in the workplace.”
Figure 1 Hierarchy of controls (NIOSH, 2013, p. 9)
The hierarchy of controls calls for hazard reduction at the source as the best solution. (See fig. 1) Engineering controls are favoured over protective equipment. Ventilation, enclosure, substitution and isolation are examples of engineering controls. Engineering controls are necessary when electric circular saws or hand power tools produce a source of inhalable silica concrete dust (Garcia et al. 2014; Shepherd and Woskie 2010). Effective dust control interventions remove dust and maintenance “becomes a daily part of work processes (Shepherd and Woskie 2010).
The Quantitative Risk Management Framework (QRMF) design is the appropriate hierarchy for identifying and reducing dust explosion risk. A sugar refinery was a study location to test QRMF (Abuswer, Amyotte, Khan et al., 2013, pg. 1530). The three main steps of QRMF are the use of a “combined management protocol,” the use of a dust explosion simulation model and the implementation of hierarchy controls (Abuswer et al. pg. 1530).
Using the QRMF, at first the hazards need to be identified and understood and then a detailed map of workers, machines and structures impacted by a dust explosion is produced (Abuswer et al., 2013). Recording details for the map takes a long time so using the Dust Explosion Simulation Code (DESC), a computer model can quickly generate the results after the details have been input. Explosion event risk likelihood is analyzed with 10 years of historical data to calculate risk probabilities. The next steps call for risk estimation, environment evaluation, the implementation of risk controls and then a study to identify residual hazards and their consequences (Abuswer et al., 2013). Finally risk re-estimation is carried out as new data becomes available (Abuswer et al., 2013).
Risk is integral to risk management and three essential phases are part of the evaluation according to Singh (1990).
Identify the hazard and the features of the hazard including the chemical characteristics, concentration, location, area hazard covers and “the nature of the hazard” Singh, 1990, p. 769; WHO 1990).
Evaluation of the hazard including a “vulnerability analysis” (Singh, 1990, p. 769), and
Risk evaluation.
Conventional pumps have not shown success at removing nanoparticles from welding stainless steel so a control banding tool was developed to evaluate for the risk of Metal Active Gas arc welding on stainless steel (ASTM 2007 cited by Albuquerque eta l. 2015:Chalupka 2010). The control banding tool was applied to compare welding processes for the best method to reduce small diameter dust particles and it helps identify the best removal method such as exhaust hood gas ventilation, localized ventilation or containment (Albuquerque et al. 2015; Chalupka 2010).
1.5 Conclusion
In 2015 airborne hazards caused approximately 13,000 deaths from lung disease and cancer (UKHSE 2015). The illnesses were blamed on dust and chemicals inhaled at UK workplaces (UKHSE 2015). Breathing in dust at work is a health safety problem that causes cancer, trouble breathing as well as asthma and lung related diseases (Binazzi et al. 2015; Siew et al. 2015). Fire and explosions area another type of hazard that take place when dust ignites from sparking machinery, especially from circular saws (Hedlund et al. 2014). The employer is responsible for the safety of the workers; in order to improve safety and reduce risk airborne dust must be controlled. The amount and type of airborne dust is regulated by the HSE.
The hierarchy of controls recommends elimination of the problem as the best solution but that is usually cost prohibitive or no method has yet been developed to accomplish that solution. Engineering controls are considered better than administrative controls and personal protective equipment is the least desired solution to hazardous airborne dust problems in the workplace (NIOSH, 2013). Sawing wood with and without resins is a risk due to the airborne dust; the dust from resins is considered hazardous due to the formaldehyde in resins. Sawing, grinding, sanding, polishing and polishing stainless steel is a high health risk unless engineering controls are applied.
The Quantitative Risk Management Framework was identified as a particularly useful process to identify and reduce dusk explosions as well as useful for evaluating and finding solutions for other types of airborne dusts. Another evaluation tool is the Control Banding Tool that was developed specifically to evaluate the risk of small diameter dust particles during the welding of stainless steel. Local Exhaust Ventilation (LEV) systems are popular; some are attached to the saws, grinders or other tools; some LEV designs are structurally introduced into the workroom. Ideally, the collected air with dust can be filtered and reintroduced back into the work environment using an LEV design.
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