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.
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]
Sawdust is a primary ingredient in many types of processed chicken. [9]
Airborne sawdust and sawdust accumulations present a number of health and safety hazards. [10] 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. [11] [12] Certain woods and their dust contain toxins that can produce severe allergic reactions. [13] 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.
Breathing airborne wood dust may cause allergic respiratory symptoms, mucosal and non-allergic respiratory symptoms, and cancer. [14] 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. [15]
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. [16]
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.
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.
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.
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. [17]
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.
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. [18]
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.
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. [19]
Wood flour can be used as a binder in grain filler compounds.
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.
Wood flour can be subject to dust explosions if not cared for and disposed of properly.
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. [20] Particles of concern for human respiratory health are those <100 μm (where the symbol < means ‘less than’).
Zhang (2004) [21] 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. [22] 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. [23]
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) [24]
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. [25]
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. [26]
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.
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). [27] 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.
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.
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. [28] 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.
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. [29]
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″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. [30] For example, sawdust is used by biomass power plants as fuel or is sold to dairy farmers as animal bedding. [30]
Formaldehyde ( for-MAL-di-hide, fər-) (systematic name methanal) is an organic compound with the chemical formula CH2O and structure H−CHO, more precisely H2C=O. The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as aqueous solutions (formalin), which consists mainly of the hydrate CH2(OH)2. It is the simplest of the aldehydes (R−CHO). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings. Small amounts also occur naturally.
Coal dust is a fine-powdered form of coal which is created by the crushing, grinding, or pulverization of coal rock. Because of the brittle nature of coal, coal dust can be created by mining, transporting, or mechanically handling it.
Acrylonitrile is an organic compound with the formula CH2CHCN and the structure H2C=CH−C≡N. It is a colorless, volatile liquid. It has a pungent odor of garlic or onions. Its molecular structure consists of a vinyl group linked to a nitrile. It is an important monomer for the manufacture of useful plastics such as polyacrylonitrile. It is reactive and toxic at low doses.
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. However, carbon black can be used as a model compound for diesel soot to better understand how diesel soot behaves under various reaction conditions as carbon black and diesel soot have some similar properties such as particle sizes, densities, and copolymer adsorption abilities that contribute to them having similar behaviours under various reactions such as oxidation experiments. Carbon black is used as a colorant and reinforcing filler in tires and other rubber products; pigment and wear protection additive in plastics, paints, and ink pigment. It is used in the EU as a food colorant when produced from vegetable matter (E153).
Particle board, also known as particleboard, chipboard, and low-density fiberboard, is an engineered wood product manufactured from wood chips and a synthetic resin or other suitable binder, which is pressed and extruded. Particle board is often confused with oriented strand board, a different type of fiberboard that uses machined wood flakes and offers more strength.
Bromoform is an organic compound with the chemical formula CHBr3. It is a colorless liquid at room temperature, with a high refractive index and a very high density. Its sweet odor is similar to that of chloroform. It is one of the four haloforms, the others being fluoroform, chloroform, and iodoform. It is a brominated organic solvent. Currently its main use is as a laboratory reagent. It is very slightly soluble in water and is miscible with alcohol, benzene, chloroform, ether, petroleum ether, acetone and oils.
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.
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.
Potassium nitrate is an oxidizer so storing it near fire hazards or reducing agents should be avoided to minimise risk in case of a fire.
Glycidol is an organic compound that contains both epoxide and alcohol functional groups. Being bifunctional, it has a variety of industrial uses. The compound is a slightly viscous liquid that is slightly unstable and is not often encountered in pure form.
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.
Occupational toxicology is the application of toxicology to chemical hazards in the workplace. It focuses on substances and conditions that people may be exposed to in workplaces, including inhalation and dermal exposures, which are most prevalent when discussing occupational toxicology. These environmental and individual exposures can impact health, and there is a focus on identifying early adverse affects that are more subtle than those presented in clinical medicine.
Butyl acrylate is an organic compound with the formula C4H9O2CCH=CH2. A colorless liquid, it is the butyl ester of acrylic acid. It is used commercially on a large scale as a precursor to poly(butyl acrylate). Especially as copolymers, such materials are used in paints, sealants, coatings, adhesives, fuel, textiles, plastics, and caulk.
Occupational dust exposure can occur in various settings, including agriculture, construction, forestry, and mining. Dust hazards include those that arise from handling grain and cotton, as well as from mining coal. Wood dust, commonly referred to as "sawdust", is another occupational dust hazard that can pose a risk to workers' health.
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.
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