Sawdust (or wood dust) is a by-product or waste product of woodworking operations such as sawing, sanding, milling and routing. It is composed of very small chips of wood. These operations can be performed by woodworking machinery, portable power tools or by use of hand tools. In some manufacturing industries it can be a significant fire hazard and source of occupational dust exposure.
Sawdust, as particulates, is the main component of particleboard. Research on health hazards comes from the field of occupational safety and health, and study of ventilation happens in indoor air quality engineering. Sawdust is an IARC group 1 Carcinogen.
Two waste products, dust and chips, form at the working surface during woodworking operations such as sawing, milling and sanding. These operations both shatter lignified wood cells and break out whole cells and groups of cells. Shattering of wood cells creates dust, while breaking out of whole groups of wood cells creates chips. The more cell-shattering that occurs, the finer the dust particles that are produced. For example, sawing and milling are mixed cell shattering and chip forming processes, whereas sanding is almost exclusively cell shattering. [1]
A major use of sawdust is for particleboard; coarse sawdust may be used for wood pulp. Sawdust has a variety of other practical uses, including serving as a mulch, as an alternative to clay cat litter, or as a fuel. Until the advent of refrigeration, it was often used in icehouses to keep ice frozen during the summer. It has been used in artistic displays, and as scatter in miniature railroad and other models. It is also sometimes used to soak up liquid spills, allowing the spill to be easily collected or swept aside. As such, it was formerly common on barroom floors. [2] It is used to make Cutler's resin. Mixed with water and frozen, it forms pykrete, a slow-melting, much stronger form of ice.[ citation needed ]
Sawdust is used in the manufacture of charcoal briquettes. The claim for invention of the first commercial charcoal briquettes goes to Henry Ford who created them from the wood scraps and sawdust produced by his automobile factory. [3]
Cellulose, fibre starch that is indigestible to humans, and a filler in some low calorie foods, can be and is made from sawdust, as well as from other plant sources. [4] While there is no documentation [5] for the persistent rumor, based upon Upton Sinclair's novel The Jungle , that sawdust was used as a filler in sausage, cellulose derived from sawdust was and is used for sausage casings. [6] Sawdust-derived cellulose has also been used as a filler in bread. [7]
When cereals were scarce, sawdust was sometimes an ingredient in kommissbrot . Auschwitz concentration camp survivor, Dr. Miklós Nyiszli, reports in Auschwitz: A Doctor's Eyewitness Account that the subaltern medical staff, who served Dr. Josef Mengele, subsisted on "bread made from wild chestnuts sprinkled with sawdust". [8]
Airborne sawdust and sawdust accumulations present a number of health and safety hazards. [9] Wood dust becomes a potential health problem when, for example, the wood particles, from processes such as sanding, become airborne and are inhaled. Wood dust is a known human carcinogen. [10] [11] Certain woods and their dust contain toxins that can produce severe allergic reactions. [12] The composition of sawdust depends on the material it comes from; sawdust produced from natural wood is different from that of sawdust produced from processed wood or wood veneer.[ citation needed ]
Breathing airborne wood dust may cause allergic respiratory symptoms, mucosal and non-allergic respiratory symptoms, and cancer. [13] In the US, lists of carcinogenic factors are published by the American Conference of Governmental Industrial Hygienists (ACGIH), the Occupational Safety and Health Administration (OSHA), and the National Institute for Occupational Safety and Health (NIOSH). All these organisations recognize wood dust as carcinogenic in relation to the nasal cavities and paranasal sinuses. [14]
People can be exposed to wood dust in the workplace by breathing it in, skin contact, or eye contact. The OSHA has set the legal limit (permissible exposure limit) for wood dust exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The NIOSH has set a recommended exposure limit (REL) of 1 mg/m3 over an 8-hour workday. [15]
Water-borne bacteria digest organic material in leachate, but use up much of the available oxygen. This high biochemical oxygen demand can suffocate fish and other organisms. There is an equally detrimental effect on beneficial bacteria, so it is not at all advisable to use sawdust within home aquariums, as was once done by hobbyists seeking to save some expense on activated carbon.[ citation needed ]
Sawdust is flammable and accumulations provide a ready source of fuel. Airborne sawdust can be ignited by sparks or even heat accumulation and result in dust fire or explosions.[ citation needed ]
At sawmills, unless reprocessed into particleboard, burned in a sawdust burner, or used to make heat for other milling operations, sawdust may collect in piles and add harmful leachates into local water systems, creating an environmental hazard. This has placed small sawyers and environmental agencies in a deadlock.[ citation needed ]
Questions about the science behind the determination of sawdust being an environmental hazard remain for sawmill operators (though this is mainly with finer particles), who compare wood residuals to dead trees in a forest. Technical advisors have reviewed some of the environmental studies, but say most lack standardized methodology or evidence of a direct impact on wildlife. They do not take into account large drainage areas, so the amount of material that is getting into the water from the site in relation to the total drainage area is minuscule.[ citation needed ]
Other scientists have a different view, saying the "dilution is the solution to pollution" argument is no longer accepted in environmental science. The decomposition of a tree in a forest is similar to the impact of sawdust, but the difference is of scale. Sawmills may be storing thousands of cubic metres of wood residues in one place, so the issue becomes one of concentration.[ citation needed ]
Of larger concern are substances such as lignins and fatty acids that protect trees from predators while they are alive, but can leach into water and poison wildlife. Those types of things remain in the tree and, as the tree decays, they slowly are broken down. But when sawyers are processing a large volume of wood and large concentrations of these materials permeate into the runoff, the toxicity they cause is harmful to a broad range of organisms. [16]
Wood flour is finely pulverized wood that has a consistency fairly equal to sand or sawdust, but can vary considerably, with particles ranging in dimensions from a fine powder to roughly that of a grain of rice. Most wood flour manufacturers are able to create batches of wood flour that have the same consistency throughout. All high quality wood flour is made from hardwoods because of its durability and strength. Very low grade wood flour is occasionally made from sapless softwoods such as pine or fir.[ citation needed ]
Wood flour is commonly used as a filler in thermosetting resins such as bakelite, and in linoleum floor coverings. Wood flour is also the main ingredient in wood/plastic composite building products such as decks and roofs. Prior to 1920, wood flour was used as the filler in ¼-inch thick Edison Diamond Discs. [17]
Wood flour has found a use in plugging small through-wall holes in leaking main condenser (heat exchanger) tubes at electrical power generating stations via injecting small quantities of the wood flour into the cooling water supply lines. Some of the injected wood flour clogs the small holes while the remainder exits the station in a relatively environmentally benign fashion.[ citation needed ]
Because of its adsorbent properties it has been used as a cleaning agent for removing grease or oil in various occupations. It has also been noted for its ability to remove lead contamination from water. [18]
Wood flour can be used as a binder in grain filler compounds.[ citation needed ]
Large quantities of wood flour are frequently to be found in the waste from woodworking and furniture companies. An adaptive reuse to which this material can be directed is composting.[ citation needed ]
Wood flour can be subject to dust explosions if not cared for and disposed of properly.[ citation needed ]
As with all airborne particulates, wood dust particle sizes are classified with regard to effect on the human respiratory system. For this classification, the unit for measurement of particle sizes is the micrometre or micron (μm), where 1 micrometre = 1 micron. Particles below 50 μm are not normally visible to the naked human eye. [19] Particles of concern for human respiratory health are those <100 μm (where the symbol < means ‘less than’).[ citation needed ]
Zhang (2004) [20] has defined the size of indoor particulates according to respiratory fraction:
Respiratory fraction | Size range |
---|---|
Inhalable | ≤ 100 μm |
Thoracic | ≤ 10 μm |
Respirable | ≤ 4 μm |
Diminutive | ≤ 0.5 μm |
Particles which precipitate in the vicinity of the mouth and eyes, and get into the organism, are defined as the inhalable fraction, that is total dust. Smaller fractions, penetrating into the non-cartilage respiratory tract, are defined as respirable dust. [21] Dust emitted in the wood industry is characterized by the dimensional disintegration of particles up to 5 μm, and that is why they precipitate mostly in the nasal cavity, increasing the risk of cancer of the upper respiratory tract. [22]
The parameter most commonly used to characterize exposures to wood dust in air is total wood dust concentration, in mass per unit volume. In countries that use the metric system, this is usually measured in mg/m3 (milligram per cubic metre) [23]
A study to estimate occupational exposure to inhalable wood dust by country, industry, the level of exposure and type of wood dust in 25 member states of the European Union (EU-25) found that in 2000–2003, about 3.6 million workers (2.0% of the employed EU-25 population) were occupationally exposed to inhalable wood dust. The highest exposure levels were estimated to occur in the construction sector and furniture industry. [24]
Wood dust is known to be a human carcinogen, based on sufficient evidence of carcinogenicity from studies in humans. It has been demonstrated through human epidemiologic studies that exposure to wood dust increases the occurrence of cancer of the nose (nasal cavities and paranasal sinuses). An association of wood dust exposure and cancers of the nose has been observed in numerous case reports, cohort studies, and case control studies specifically addressing nasal cancer. [25]
To lower the concentration of airborne dust concentrations during woodworking, dust extraction systems are used. These can be divided into two types. The first are local exhaust ventilation systems, the second are room ventilation systems. Use of personal respirators, a form of personal protective equipment, can also isolate workers from dust.[ citation needed ]
Local exhaust ventilation (LEV) systems rely on air pulled with a suction force through piping systems from the point of dust formation to a waste disposal unit. They consist of four elements: dust hoods at the point of dust formation, ventilation ducts, an air cleaning device (waste separator or dust collector) and an air moving device (a fan, otherwise known as an impeller). [26] The air, containing dust and chips from the woodworking operation, is sucked by an impeller. The impeller is usually built into, or placed close to, the waste disposal unit, or dust collector.[ citation needed ]
Guidelines of performance for woodworking LEV systems exist, and these tie into occupational air quality regulations that exist in many countries. The LEV guidelines often referred to are those set by the ACIAH.[ citation needed ]
Low-volume/high-velocity (LVHV) capture systems are specialised types of LEV that use an extractor hood designed as an integral part of the tool or positioned very close to the operating point of the cutting tool. The hood is designed to provide high capture velocities, often greater than 50 m/s (10,000 fpm) at the contaminant release point. This high velocity is accompanied by airflows often less than 0.02m3/s (50 cfm) resulting from the small face area of the hood that is used. [27] These systems have come into favour for portable power tools, although adoption of the technology is not widespread. Festool is one manufacturer of portable power tools using LVHV ventilation integrated into the tool design.[ citation needed ]
If suitably designed, general ventilation can also be used as a control of airborne dust. General ventilation can often help reduce skin and clothing contamination, and dust deposition on surfaces. [28]
″There was once a time when sawmill operators could barely give away their sawdust. They dumped it in the woods or incinerated it just to get rid of the stuff. These days, they have ready markets for sawdust…″, according to a report in 2008. [29] For example, sawdust is used by biomass power plants as fuel or is sold to dairy farmers as animal bedding. [29]
A carcinogen is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruses and bacteria. Most carcinogens act by creating mutations in DNA that disrupt a cell's normal processes for regulating growth, leading to uncontrolled cellular proliferation. This occurs when the cell's DNA repair processes fail to identify DNA damage allowing the defect to be passed down to daughter cells. The damage accumulates over time. This is typically a multi-step process during which the regulatory mechanisms within the cell are gradually dismantled allowing for unchecked cellular division.
Fiberglass or fibreglass is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinyl ester resin—or a thermoplastic.
Spray painting is a painting technique in which a device sprays coating material through the air onto a surface. The most common types employ compressed gas—usually air—to atomize and direct the paint particles.
Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. It is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis. Silicosis, particularly the acute form, is characterized by shortness of breath, cough, fever, and cyanosis. It may often be misdiagnosed as pulmonary edema, pneumonia, or tuberculosis. Using workplace controls, silicosis is almost always a preventable disease.
Carbon black is a material produced by the incomplete combustion of coal tar, vegetable matter, or petroleum products, including fuel oil, fluid catalytic cracking tar, and ethylene cracking in a limited supply of air. Carbon black is a form of paracrystalline carbon that has a high surface-area-to-volume ratio, albeit lower than that of activated carbon. It is dissimilar to soot in its much higher surface-area-to-volume ratio and significantly lower polycyclic aromatic hydrocarbon (PAH) content.
Chemical hazards are hazards present in hazardous chemicals and hazardous materials. Exposure to certain chemicals can cause acute or long-term adverse health effects. Chemical hazards are usually classified separately from biological hazards (biohazards). Chemical hazards are classified into groups that include asphyxiants, corrosives, irritants, sensitizers, carcinogens, mutagens, teratogens, reactants, and flammables. In the workplace, exposure to chemical hazards is a type of occupational hazard. The use of personal protective equipment may substantially reduce the risk of adverse health effects from contact with hazardous materials.
Particle board, also known as particleboard or chipboard, is an engineered wood product, belonging to the wood-based panels, manufactured from wood chips and a synthetic, mostly formaldehyde based resin or other suitable binder, which is pressed under a hot press, batch- or continuous- type, and produced. Particle board is often confused with oriented strand board, a different type of fiberboard that uses machined wood flakes and offers more strength.
IARC group 1 Carcinogens are substances, chemical mixtures, and exposure circumstances which have been classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC). This category is used when there is sufficient evidence of carcinogenicity in humans. Exceptionally, an agent may be placed in this category when evidence of carcinogenicity in humans is less than sufficient, but when there is sufficient evidence of carcinogenicity in experimental animals and strong evidence in exposed humans that the agent (mixture) acts through a relevant mechanism of carcinogenicity.
Environmental hazards are those hazards that affect biomes or ecosystems. Well known examples include oil spills, water pollution, slash and burn deforestation, air pollution, ground fissures, and build-up of atmospheric carbon dioxide. Physical exposure to environmental hazards is usually involuntary
Occupational lung diseases comprise a broad group of diseases, including occupational asthma, industrial bronchitis, chronic obstructive pulmonary disease (COPD), bronchiolitis obliterans, inhalation injury, interstitial lung diseases, infections, lung cancer and mesothelioma. These can be caused directly or due to immunological response to an exposure to a variety of dusts, chemicals, proteins or organisms. Occupational cases of interstitial lung disease may be misdiagnosed as COPD, idiopathic pulmonary fibrosis, or a myriad of other diseases; leading to a delay in identification of the causative agent.
Nanotoxicology is the study of the toxicity of nanomaterials. Because of quantum size effects and large surface area to volume ratio, nanomaterials have unique properties compared with their larger counterparts that affect their toxicity. Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation, fibrosis, and carcinogenicity for some nanomaterials. Skin contact and ingestion exposure are also a concern.
The use of podiatry drills, in the absence of engineering controls and personal protective equipment, is an occupational hazard to the healthcare provider. Nail dust collected during foot care procedures performed in office settings has been found to contain keratin, keratin hydrolysates, microbial debris, and viable fungal elements, including dermatophytes and saprotrophs. Exposure to nail dust and the associated risk will vary with the policies and practices in place, the type of podiatry drill used, therapy technique, frequency of procedures, personal protective equipment utilized and the use of ventilation systems.
Indoor mold or indoor mould, also sometimes referred to as mildew, is a fungal growth that develops on wet materials in interior spaces. Mold is a natural part of the environment and plays an important part in nature by breaking down dead organic matter such as fallen leaves and dead trees; indoors, mold growth should be avoided. Mold reproduces by means of tiny spores. The spores are like seeds, but invisible to the naked eye, that float through the air and deposit on surfaces. When the temperature, moisture, and available nutrient conditions are correct, the spores can form into new mold colonies where they are deposited. There are many types of mold, but all require moisture and a food source for growth.
Indoor bioaerosol is bioaerosol in an indoor environment. Bioaerosols are natural or artificial particles of biological origin suspended in the air. These particles are also referred to as organic dust. Bioaerosols may consist of bacteria, fungi, viruses, microbial toxins, pollen, plant fibers, etc. Size of bioaerosol particles varies from below 1 μm to 100 μm in aerodynamic diameter; viable bioaerosol particles can be suspended in air as single cells or aggregates of microorganism as small as 1–10 μm in size. Since bioaerosols are potentially related to various human health effects and the indoor environment provides a unique exposure situation, concerns about indoor bioaerosols have increased over the last decade.
Inhalation is a major route of exposure that occurs when an individual breathes in polluted air which enters the respiratory tract. Identification of the pollutant uptake by the respiratory system can determine how the resulting exposure contributes to the dose. In this way, the mechanism of pollutant uptake by the respiratory system can be used to predict potential health impacts within the human population.
Dustiness may be defined as the propensity of a finely divided solid to form an airborne dust (aerosol) from a mechanical or aerodynamic stimulus. Dustiness can be influenced by particle morphology (shape), size, and inter-particle forces. Dustiness increases the risk of inhalation exposure.
Occupational dust exposure occurs when small particles are generated at the workplace through the disturbance/agitation of rock/mineral, dry grain, timber, fiber, or other material. When these small particles become suspended in the air, they can pose a risk to the health of those who breath in the contaminated air.
The health and safety hazards of nanomaterials include the potential toxicity of various types of nanomaterials, as well as fire and dust explosion hazards. Because nanotechnology is a recent development, the health and safety effects of exposures to nanomaterials, and what levels of exposure may be acceptable, are subjects of ongoing research. Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation, fibrosis, and carcinogenicity for some nanomaterials. Skin contact and ingestion exposure, and dust explosion hazards, are also a concern.
Occupational hazards of fire debris cleanup are the hazards to health and safety of the personnel tasked with clearing the area of debris and combustion products after a conflagration. Once extinguished, fire debris cleanup poses several safety and health risks for workers. Employers responsible for fire debris cleanup and other work in areas damaged or destroyed by fire are generally obliged by occupational safety and health legislation of the relevant national or regional authority to identify and evaluate hazards, correct any unsafe or unhealthy conditions and provide any necessary training and instruction and personal protective equipment to employees to enable them to carry out the task without undue exposure to hazards. Many of the approaches to control risk in occupational settings can be applied to preventing injuries and disease. This type of work can be completed by general construction firms who may not be fully trained specifically for fire safety and on fire hazards.
Any type of woodworking that involves cutting, either by hand or machine, releases sawdust. Because fine sawdust can float through the air, it can be easily inhaled without proper protection, leading to damaging injuries to a woodworker's skin and lungs. Sawdust is also an IARC group 1 Carcinogen.