Confused about the meaning of dust, combustible dust, particulate matter, PM2.5, PM10, coarse particulates, fine particulates, inhalable particulates, respirable particulates, nanoparticles, smoke, black smoke, black carbon, fibers, fumes, aerosols and mists? Concerned about how these may affect health and safety of your workers? Uncertain about your legal responsibilities and how to manage these hazards at your site?
Relax. You are not alone. This is a confusing topic and I’ve spent some time pulling together pertinent information for you. All you need to do is invest some time reading this blog post. You will then know what you need to know!
In the following sections of this post, I (1) provide a definition of these key contaminants, (2) list typical sources that lead to elevated levels in the workplaces, (3) discuss regulatory issues, (4) describe health concerns, and (5) offer suggestions to protect your workers from these hazards. I’ll conclude the post with a discussion of what you can do to identify and evaluate whether you have a serious problem at your site.
There is a lot of information to cover, so, I have broken this down into two posts.
Part 2: Smoke, Fumes, Mist and Aerosols
Feel free to skip to the section(s) that are of most interest to you and save the others for later review.
Smoke, Black Smoke & Black Carbon
Definition: Black smoke is defined by EPA as smoke in the exhaust emissions of a diesel-powered motor vehicle that (1) produces a dark achromatic visual value and produces no predominant hue or (2) a hue of the portion of the visible light spectrum which lies between green and violet. Smoke is defined by EPA as the emissions, including airborne solid and/or liquid particles, exclusive of water vapor, released into the atmosphere from a process of combustion. Black carbon (BC) is described by EPA as the most strongly light-absorbing component of particulate matter (PM), and is formed by the incomplete combustion of fossil fuels, biofuels, and biomass.
Black smoke was traditionally used in the past but has been largely replaced by black carbon as the measure of the dark component of smoke, in part because it is an important climate change driver. There is a strong relationship between the two variables.
Sources: An EPA study on emissions of BC lists many different sources arising from open biomass burning, energy/power hydrocarbon combustion, industrial processes, mobile sources and many other categories. Heavy-duty diesels were noted to account for 77% of BC in the US. Streets et al (2001) studied BC in China, where roughly one-quarter of the global anthropogenic emissions arise. In China high rates of coal and biofuels are the primary source of BC.
Regulations: Black smoke is regulated in many countries, primarily as it pertains to emissions from mobile and stationary sources such as generators, power plants and vehicles. In most developing countries, the wording in regulations is typically along the lines of no “black smoke to be emitted”, so that regulations are are most often qualitative rather than quantitative in nature.
Black carbon is generally regulated indirectly via vehicle emission tests, regulating types of fuels, limiting biomass burning, operating permits, etc.
Health: EPA notes that BC is a component of both PM10 and PM2.5 (see Part 1 for a discussion of PM2.5 and PM10). Thus, the potential health impacts noted for those variables above also apply to black carbon (and black smoke).
Control: Measures for control of combustion-related sources, as discussed above for PM10 and PM2.5, apply directly to black smoke and black carbon.
Fibres are solid particles with its length many time greater than its width. Asbestos is an example. I have discussed asbestos in a previous blog post: What You Need to Know About Asbestos in Asia – Because What You Don’t Know Can Kill!. Refer to that post for additional information.
Definition: OSHA defines fumes as “particles formed when a volatilized solid, such as a metal, condenses in cool air. This physical change is often accompanied by a chemical reaction, such as oxidation. Examples are lead oxide fumes from smelting, and iron oxide fumes from arc-welding. A fume can also be formed when a material such as magnesium metal is burned or when welding or gas cutting is done on galvanized metal.”
Regulations: In developed countries there are typically specific regulations that may apply to fumes, particularly with respect to specific chemical compounds associated with fumes, e.g., OSHA 1925.55 App A. Gases, vapors, fumes, dusts, and mists. In contrast, most developing countries do not specifically regulate fumes, albeit there may be indirect regulations related to ventilation requirements, safe work practices, etc. It is thus incumbent upon the HSE professional to understand the legal requirements where he/she operates.
Health: Acute exposure to fumes can result in eye, nose and throat irritation, dizziness and nausea. Chronic exposures and health impacts are dependent upon the type, duration and intensity of exposure. For instance, asphalt fumes contain carcinogenic polycyclic aromatic hydrocarbons that can cause cancers. Asphalt fumes have also been cited as causing various conditions such as asthma, chronic bronchitis, emphysema, and other conditions.
Studies of workers in the electronic industry in the US and England found that 20% of workers in soldering areas showed clinical symptoms of asthma caused by the work environment. Lead fumes from solder cause a wide range of adverse health effects. These include fatigue, irritation and anemia along with other reproductive effects such as spontaneous abortion and sterility.
The makeup of welding fumes varies widely depending upon the type of welding, the type of metal used and welding rod composition. Fumes may contain any or all of the following metals: aluminum, antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, silver, tin, titanium, vanadium and zinc. Potential health impacts from prolonged exposure to these fumes may cause lung damage and various types of cancer, including lung, larynx and urinary tract cancers. Health effects from certain fumes may include metal fume fever, stomach ulcers, kidney damage and nervous system damage. Prolonged exposure to manganese fumes can cause Parkinson’s–like symptoms. Gases such as helium, argon, and carbon dioxide displace oxygen in the air and can lead to suffocation, particularly when welding in confined or enclosed spaces. Carbon monoxide gas can form, posing a serious asphyxiation hazard.
Control: The HSE professional must understand the hazards of the specific fumes that their workers may be exposed to and provide information and training specific to the particular hazard at their site. In general, control systems include appropriate ventilation and exhaust systems combined with appropriate PPE: respiratory protection, proper clothing, gloves, eye protection, etc.
Definition: Aerosols are defined in a number of different way; a definition provided by NIOSH is that they are small particles (dust, solids) or droplets (liquid phase or mist) suspended in air. Note that OSHA defines aerosols as a material which is dispensed from its container as a mist, spray, or foam by a propellant under pressure, and also defines a category of flammable aerosols. What we typically refer to as haze can be caused by light scattering of aerosols.
We have discussed the particulate phases of aerosols in Part 1 and in the following section on mist we discuss the liquid phase.
Definition: OSHA defines mist as “liquid droplets of a substance or mixture suspended in a gas (usually air)”.
Sources: Process in which water or other liquids are sprayed, such as spray painting, metalworking, plasma and laser cutting, CNC machines, food processing, etc. are sources of mist in the workplace. Strong inorganic acid mists containing sulfuric acid may be produced as a result of the use of mixtures of strong inorganic acids including sulfuric acid, in industrial processes such as acid treatment of metals, phosphate fertilizer manufacture, lead battery manufacture, and various other industries.
Regulations: In developed countries there are typically specific regulations that may apply to mists, particularly with respect to specific chemical compounds associated with mists, e.g., OSHA 1925.55 App A. Gases, vapors, fumes, dusts, and mists. In contrast, most developing countries do not specify standards for mists, albeit there may be indirect regulations related to ventilation requirements, safe work practices, etc. It is thus incumbent upon the HSE professional to understand the legal requirements where he/she operates.
Health: Potential health impacts from exposure to mists are dependent upon the toxicity and concentrations of the constituents in the mist, plus duration and intensity of exposure. Acute exposure to a wide variety of fumes can result in eye, throat, and skin irritation. Exposure to mineral oil mist can cause pulmonary effects and dermatitis. Long-term exposure to metal cutting/grinding fluids can lead to certain types of skin cancer. Strong inorganic acid mists containing sulfuric acid are known to be human carcinogens based on sufficient evidence of carcinogenicity from studies in humans. Additional adverse health effects from breathing sulfuric acid mists in particular include tooth erosion and respiratory tract irritation.
Control: The HSE professional mucst understand the hazards of the specific fumes that their workers may be exposed to and provide information and training specific to the particular hazard at their site. In general, control systems include appropriate ventilation and exhaust systems combined with appropriate PPE: respiratory protection, proper clothing, gloves, eye protection, etc.
How to Identify and Evaluate Risks of Airborne Particles
WHO suggests a systematic approach to identify and evaluate if a potential air contaminant problem exists, and this approach may be worth considering to investigate airborne issues at your facility. In particular, they propose that if any process is being carried out that releases significant amounts of contaminants into the workspace, then an assessment should be made to establish if people are at risk from that exposure.
This assessment is done by looking systematically at the workplace to see whether there is a problem and in general terms what could be done to minimize risks to workers. The assessment should determine which hazardous materials are in use, in what amounts, and how much of which fraction may become airborne and lead to exposure, among other factors. This can include:
- An initial “walk-through” survey of the workplace. The walk-through survey will not usually include detailed measurement, although direct-reading instruments may be used to gain a rough picture of the risks present. Obvious and avoidable risks can be dealt with immediately, and schemes exist for using basic substance and use information to decide what controls are appropriate.
- The controls in use should be examined to determine their effectiveness, and the eventual need for other or additional controls should be considered.
- Maintenance and cleaning procedures should be examined to ensure that they are effective and do not give rise to excessive exposure.
- The position of workers and the organization of their tasks should be appraised in view of the location and nature of the contaminant sources.
- The level of training and information of the workforce should also be assessed. It should be ensured that management favours work practices that reduce or eliminate risks.
- Quantitative evaluations of airborne constituents may be performed for a number of reasons, for example: to assess workers’ exposure in relation to an adopted standard, to determine the need for control measures or to assess the effectiveness of control strategies.
- The results of quantitative evaluations are usually compared with occupational exposure limits. The determination of the contaminant air concentrations to which workers are exposed involves air sampling and further analysis of the collected sample, chemically, gravimetrically or microscopically.
- Sampling for exposure assessment is usually carried out by means of a personal sampler, attached to the worker, and which consists of a pump (air mover) and a sampling head located in the worker’s breathing zone.
- Sampling of workers’ blood, urine and/or hair for biomarkers or levels of contaminants and medial tests may be useful to establish baseline levels of exposure and to monitor effectiveness of control measures.
- Other measurements may be helpful to understand where the airborne contaminants are coming from, or at what moment(s) of the work cycle it is being emitted. Often, but not always, the workers involved may be able to say where and when dust, gases, smoke or mists are emitted.
Of course, if you have any concerns about dust, smoke, fumes, aerosols, mists or any other air quality issues at your facility and/or need assistance in designing and/or carrying out the assessment, feel free to contact us. We will most certainly be pleased to help.
Thanks for reading. Keep safe. Be healthy. Respect your environment.
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Photo Credits: Fumes image courtesy of Rybson at www.freeimages.com