A downdraft table is a dust control device that reduces airborne wood dust during woodworking operations.
Hazard Analysis — Wood dust
Problem:Workers that cut boards and panels may face hazards from wood dust.
Cutting boards and panels generates wood dust which can cause irritations or allergic reaction following contact with the skin, respiratory tract or eyes. Exposure to some wood dusts has also been linked to respiratory ailments such as occupational asthma and shown to be associated with nasal cancer.
When wood dust comes into contact with the skin, its non-allergic effect is usually irritation, which can lead to rashes or irritant dermatitis. The skin on the scalp, eyelids, neck, forearms, the backs of hands and genitals is most sensitive to irritation from wood dust. These symptoms usually take approximately 15 days to develop and will only persist as long as the affected skin site remains in contact with the source of the wood dust.
Wood dust from certain species contains sensitizers and can cause allergic contact dermatitis. This type of allergic reaction can produce the same effects as the non-allergic reaction to wood dust. The difference is that once the body is sensitized, it will set up an allergic reaction that can enable the skin to react more severely to even a small amount of that particular wood dust (or related wood species) in subsequent episodes of exposure.
Exposures to wood dust can affect the respiratory tract, such as the nose. Inhalation of wood dust can cause runny nose (rhinitis), sneezing, stuffed nose and nose bleeds. These symptoms usually arise from irritation, but can also be a consequence of allergic sensitization. Several studies have suggested that, although rare, certain wood dusts, especially oak and beech (confirmed human carcinogens), but perhaps also birch, mahogany, teak, walnut (suspected human carcinogens) may cause nasal cancer.
Inhalation of wood dust can lead to obstructive patterns of respiratory changes, which limit breathing flow rates and impair lung function. One lung condition attributable to wood dust exposure (especially Western Red Cedar) is occupational asthma, which includes wheezing, coughing, tightness across the chest and shortness of breath. Some wood dust can also cause asthma as an allergic reaction once the body is sensitized to that wood species.
Wood dust that comes into contact with the eyes can cause watering, soreness and inflammation of the eyes (conjunctivitis).
Performing one or more of the wood operations below can determine if you are exposed to wood dust at your worksite:
- Reparing machine
Over an 8-hours total weight average (TWA), the American Conference of Governmental Industrial Hygienists (ACGIH) published a threshold limit value (TLV) of 1 mg/m3 for wood dust, excluding western red cedar. The TLV for western red cedar is 0.5 mg/m3. Oak and beech wood dust have been confirmed as human carcinogens and birch, mahogany, teak, and walnut are classified as suspected human carcinogens (ACGIH, 2011). Risk of health effects increase when wood dust exceeds the permissible exposure level.
To assess the risk of wood dust exposures, here are other things to consider:
- Are you cleaning with compressed air?
- Are you dry sweeping?
- Are you disturbing dust on machines during maintenance work?
Regulations & Standards:
The Federal OSHA standard for non-specific total dust is 15 mg/m3. This permissible exposure limit (PEL) also serves as a surrogate for wood dust exposure and 5 mg/m3 for respirable dust. However, the American Conference of Governmental Industrial Hygienists (ACGIH) has adopted a threshold limit value (TLV) of 1 mg/m3 for the inhalable fraction of wood dust from all species and 0.5 mg/m3 for the inhalable fraction of Western Red Cedar.
Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete State plans (covering both the private sector and state and local government employees) and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands - which cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements.
Other hazardous substances that may grow on or be added to wood and be present in wood dust include:
- Molds and fungi
- Resin binders
- Paint stripper
- Glues and adhesives
- Waterproofing compounds
- Paints, laquers, and varnishes
- Sealants, dyes, and bonding agents
These substances may cause or contribute to skin, eye, and lung irritation, allergic reactions and occupational asthma. There are also several wood preservatives that are toxic and present cancer risks (creosote, pentachlorophenol [PCP] and copper arsenate).
Wood dust can create a combustible dust hazard.
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