All you need to know about dust control

Dust is a nuisance. Fugitive dust pollutes the air we breathe and contaminates our land and water resources. It is harmful to human health and safety, has a negative impact on the growth of plants, insects and animals both on land and in water.

Dust can also negatively affect the economy of companies as excess exposure to it can result in productivity loss, sick leave and operational downtime.

Human activities that generate dust are a real concern today. Gravel roads, mining, broadacre, agriculture, recreation, industry and stockpiles can all generate significant amounts of dust, which can have serious consequences if left uncontrolled.

Dust control or dust management is often never-ending, requiring a commitment and investment of both time and money.

In this article, we will explore the different solutions available for solving dust control challenges in various industries with the hope of guiding you to a sustainable solution for your dust control needs.

table of contents

      1. What is dust control?

      Dust control is the system implemented to reduce or eliminate dust emissions from the activities that generate airborne and fugitive dust and cause erosion. The amount of dust generated depends on several factors, including the nature of the surface, to what degree the surface is disturbed and climactic conditions. In arid or semi-arid regions such as those with deserts or places with periods of dry weather, dust generation is typically a larger issue.

      Dust control is the system implemented to reduce or eliminate dust emissions from the activities that generate airborne and fugitive dust and cause erosion.

      Dust control is relevant in many areas. In activities such as mining, broadacre, agriculture, recreation, and industrial stockpiling, large open areas of loosely bound materials can generate copious amounts of dust. To safely work in and use these areas, dust control measures must be taken. On dirt and gravel roads, vehicular traffic will generate dust, causing an inherent problem.

      Since fine particles in the road surface are essential in holding the unpaved road together, it is not a simple matter of just removing the dust. Sealing unpaved roads with asphalt, concrete pavement or other impermeable materials would eliminate the dust problem. However, the cost of paving roads is not justified by its low traffic volume.

      Depending on the amount of dust generated, different palliative treatments of dust suppressing additives can be applied. Watering the dust creating surfaces has traditionally been a simple and effective way of reducing nuisance dust. Many other types of dust suppressants have been developed over the years.

      A publication by the USDA Forest Services has classified dust palliatives into seven product groups:

      1. water
      2. water-absorbing
      3. petroleum-based
      4. organic nonpetroleum based
      5. electrochemical
      6. synthetic polymer
      7. clay additive products

      A more detailed description of different dust control methods is given in section ‎5.

      2. Why dust control?

      The short and simple answer to that question is because it is the most profitable and responsible option. A good system for proper dust control will protect the health of employees, increase safety, reduce maintenance and operating costs, reduce site emissions and preserve the environment.

      Health

      Air-born dust is recognised by the World Health Organization as a risk to human health (WHO SDE OEH 99.14). Dust particles are associated with multiple negative health effects, particularly to the respiratory and cardiovascular system. These effects include asthma and other pulmonary diseases, as well as forms of respiratory cancer, including cancer of the lung cavity lining. The type and size of dust particles and the amount and duration of the exposure, determine the impact on health. For example, coal dust particles are highly carcinogenic, and in mining and open coal pit haul roads exposure can be significant and is a known cause of black lung disease. Silica dust is another mineral linked to increased health hazards. Dust emissions are regulated by national guidelines with occupational exposure limits for protecting workers, road users and local residents.

      Dust control benefits the environment and employee health as well as saving costs.

      Safety

      Vehicular traffic on a dusty road, be it on a local or industrial site, reduces vision and is, therefore, clearly a safety hazard. Surface road dust reduces traction, which itself is a safety issue. Combined with reduced visibility it is a dangerous combination. In addition, unpaved or untreated roads will deteriorate more rapidly, and often have rutting, wash boarding or corrugation and potholes that cause vibration contributing to long-term vehicle wear. Also, there is a high risk of loose gravel causing damage to windshields and chipping paint. In mining operations, the presence of fine particles can be a significant safety hazard with occurrences such as coal dust self-combustion and stockpile fires.

      Economy

      Employing proper dust control can be economically advantageous. Even for low volume unpaved roads, dust palliatives preserve the fines of the road materials. Retaining these fines reduces the loss of aggregate and, therefore, lowers cost of maintenance and replacement of road materials.

      In industrial settings, a layer of loose materials reduces traction and lowers drivability. As a result, fuel consumption is increased and driving speeds are reduced, translating to higher costs and lower production.  Dust from stockpiles and transfer points is a loss of valuable material and is a financial loss. Evolved dust particles can also have an abrasive effect leading to wear and tear on equipment and machinery, in addition to the wear caused by uneven and deteriorating roads.

      Dust from agricultural and forestry roads is not only an issue for the health and well-being of workers but can also negatively affect crop economy. Airborne dust that settles on nearby vegetation can reduce crop yields by burying seedlings, causing loss of plant tissue, stunted growth, reducing photosynthetic activity and increasing soil erosion. Dust can impede the function of pesticides.

      Public image

      Dusty roads that soil homes, vehicles, plants and people are harmful to a positive image and environment. When a roadside picnic table is always covered in dust, it is not very inviting and likely will not be used. Audiences are not attracted to excessively dusty sporting tracks and arenas, which also has a negative economic impact. Selection of a dust suppressant can have an impact on public perception. Environmentally friendly and sustainable dust control products are generally much better regarded.

      3. What are the environmental benefits of dust control?

      The most obvious impact of dust is what you see; soiled homes, vehicles, plants and fauna. Fine suspended dust particles contribute significantly to the particulate loading in the atmosphere making road dust a major source of air pollution. Airborne dust can contaminate nearby vegetation and aquatic resources. This can be particularly harmful to agricultural roads where excessive dust can affect plant growth.

      Traditional dust suppressants

      Although benefitting the environment by minimising dust particles, some dust suppression additives can have a negative environmental impact. Dust suppressants may eventually run off, leach into the groundwater or be carried away to surrounding areas by adhesion to vehicles, or by dust particle migration.

      Chemical analysis of the suppressant can determine if harmful constituents are present. The potential impact on local aquatic, and plant life is normally evaluated via toxicity testing and oxygen availability testing. A standard measurement of toxicity is the LC50 or the Lethal Concentration, expressed in parts per million (ppm) that will produce a 50 per cent mortality rate in the test group in 96 hours. The larger the concentration, the less toxic the material. The Biochemical Oxygen Demand (BOD) test measures the oxygen used by microbes as it digests the product in water. There are no standard tests for measuring how dust palliatives impact the plant community. However, some tests have been performed that simply observe the impact on plant life.

      Magnesium chloride and calcium chloride salts are commonly used dust suppressants. As chlorides are toxic to aquatic life and impact vegetation and wildlife, they should only be used after careful consideration. There is no natural process by which chlorides are broken down, metabolised, taken up, or removed from the environment. If there is any risk of leaching to groundwater, water analyses before and after application are recommended. Salts should not be used in proximity to vegetation with low salt tolerance, such as various varieties of alder, hemlock, larch, maple, ornamentals, and pine.

      Petroleum-based products can introduce potentially toxic materials. Further, the production of these products can have a negative environmental impact causing increased global warming and the production of toxic side streams.

      Eco-friendly dust suppressants

      Traditionally and continuing in some areas of the world today, watering is the most simple and convenient way of suppressing dust. Simply by wetting surfaces, the increased moisture prevents the soil from disintegrating. However, water can be a scarce and costly resource and requires frequent and expensive reapplication.

      Dustex® from Borregaard is a lignin-based biopolymer derived from sustainable forests. This product has low toxicity towards aquatic and terrestrial species and can be regarded as an eco-friendly alternative when used for dust control. A Life Cycle Analysis (LCA) performed on Dustex documents the CO2 footprint of this product and reveals that Dustex is a sustainable solution compared to other dust control agents. 

      When selecting which dust suppressant to use, you should consider how it affects the surrounding ecosystem when it eventually breaks down. Into what constituents will it break-down and where do they end-up? Choosing a dust suppressant that is sustainable has become a priority for many customers.

      4. Who is dust control for?

      Dust control is for everyone in an area where the incidence of health-threatening dust inhibits safe and efficient operations.

      Dust control is relevant in many different areas like mining and construction haul roads, construction and mining sites, temporary bypasses, road shoulders, mine dumps and works, quarries, streets and roads in rural and residential areas, roads in game reserves, dust sensitive agricultural and forestry roads, parking areas and sports fields. Dust control is also important on other dust prone surfaces such as waste and mineral dumps and stockpiles, rural airstrips, mine tailings piles, industrial access roads, laydown yards, railcar toppings, etc.

      Municipalities, townships and districts

      Dust control is for those responsible for road maintenance in municipalities, townships and districts. It can be local roads, parking lots, bicycle lanes, trails, roads in game reserves, road shoulders, sand dunes, etc.

      Industry

      Dust control is important in a number of applications: construction site roads; mine access roads; quarry roads; solar and windfarm roads; haul roads; mineral dumps; quarries and dump surfaces; stockpiles; Broadacre; laydown yard; tailing ponds and railcar toppings.

      Agriculture

      It is often needed to reduce dust on agricultural roads. Road dust adversely affects crop growth, as discussed in section 2.  

      Forestry

      Dust suppression is important for sensitive forestry roads. Improving both visibility and drivability on roads and protecting vegetation from dust. The effects of dust on nearby vegetation have been discussed in section 2.  

      Recreation

      Dust control is used to prevent dust on sporting tracks like rallycross, motor cross, mountain biking, horse arenas, golf cart tracks, etc.

      5. What methods of dust control exists?

      Traditionally and continuing in some parts of the world today, watering has been perceived to be the most simple and convenient way of suppressing dust. By wetting surfaces, the increased moisture prevents the soil from disintegrating. However, during hotter months or in dry arid regions, water has only a short dust suppression effect. The water can quickly evaporate in as little as 10 minutes, and dust rises again almost immediately.

      Watering alone in such conditions would require frequent repeating. This method of dust control is labour intensive, ineffective, and a waste of limited water resources. The cost of constant watering can be very high, considering the high cost of labour, fuel, tanker maintenance, pump maintenance, tanker investments and shortage of groundwater for human consumption.

      Over the years, many ways to reduce and eliminate dust have been developed. In some cases, physical means of dust control can be sufficient. If wind is the main cause of dusting in a mineral dump location, a good solution can be wind shields. On a low traffic volume road, it might be enough to reduce speed in the dry periods to avoid road dust. In other cases, chemical binders are used for a palliative treatment preventing the generation of dust. This will be discussed more in detail in the following section.

      A publication by the USDA Forest Services has classified dust treatments into seven groups: water, water-absorbing products, petroleum-based products, organic nonpetroleum based products, electrochemical products, synthetic polymer products and clay additive products.

      In Table 1 we have listed products and grouped them according to product groups.

      Dust control additives – product group Dust control additives – products
      Water Water
      Water absorbing products Calcium chloride brine and flakes, magnesium chloride brine, sodium chloride
      Petroleum-based products Asphalt emulsions, cutback asphalt (liquid asphalt), dust oils, modified asphalt emulsions
      Organic nonpetroleum products Lignin based biopolymers, resins, tall oil emulsions, molasses, animal fats, vegetable oils
      Electrochemical products Enzymes, ionic products, sulfonated oils
      Synthetic Polymer products Polyvinyl acetate, vinyl acrylic
      Clay Additives Bentonite, montmorillonite

       

      6. How do dust control agents work?

      Dust suppressants work either by increasing the moisture content of surfaces or by binding particles together.

      Higher moisture on the soil surface causes the particles to stick together (agglomerate). Increased water content can be achieved either by spreading water or through the application of water-absorbing products. Hygroscopic salts such as calcium chloride and magnesium chloride, absorb water from the air. Surfaces treated with these salts have a higher water content than untreated soils. However, slippery roads, vehicle corrosion and negative effects of chloride on the environment are disadvantages of salt application. Rainfall eventually removes salts from the roadway, making the practical duration of a salt application typically not more than one year.

      Lignin based biopolymers derived from wood, work by binding particles together, thereby decreasing the likelihood of particles becoming airborne. In addition, multiple applications of this sustainable binder will improve the strength of the road over time. Lignin based biopolymers are considered to be non-corrosive and have a documented low toxicity towards aquatic and terrestrial species. Hence, they can be regarded as an eco-friendly and sustainable alternative to salts.

      Petroleum-based binders coat particles with a thin layer, increasing particle mass and decreasing the chance of becoming airborne. These products are derived from non-sustainable sources and are not biodegradable, meaning they will remain in the local environment.

      7. What results to expect with dust control?

      With a dust control program, you should expect less dust and dust issues negatively affecting safety, health and the environment. You can expect less complaints from neighbours, authorities and workers while reducing the number of accidents and increasing productivity.

      You should expect that information regarding the environmental impact of the dust suppressant itself should be easily available for you. You do an important job for the environment by implementing dust control. Be sure to choose an eco-friendly and sustainable dust suppressant product for your dust control program.

      Through the use of a good dust control agent on roads, you should also expect lower maintenance costs. The dust control agents will preserve the fines in the road by binding them together.  This binding of fines holds the aggregates, and there will be less need for blade maintenance and aggregate replacement. A study conducted in Colorado in the 1990’s by T.G. Sanders, concludes that road dust suppressants (lignin and chloride-based products) reduced dust by 50-70%, and the total aggregate losses were 42-61% less than the untreated control section.

      Those changing from simple water application to employing one of the other dust control methods, either for road or industrial dust control, can expect to significantly reduce labour, fuel, equipment maintenance and other associated costs. Perhaps most significantly, consumption of water will decrease by as much as 90% - critical in areas where water is a scarce resource.

      8. What are the costs and benefits of dust control?

      In addition to causing damage to properties and health and environmental issues, poor dust control will also cause economic damage. Excessive dust can limit profitability. For instance, decreased drivability on dusty mining roads or stunted crop growth near dusty agricultural roads has a measurable impact on time and crop yields, respectively.

      A road without dust suppression will quickly deteriorate, requiring frequent and costly maintenance and replacement of gravel. The cost of poor or no dust control can far exceed the cost of investment in good application of suitable dust suppressants. The direct cost of the dust suppressant, the reapplication rate, and application method (equipment and labour requirement) will affect the total cost of treatment.

      In the table below, we compare the cost of using water to the cost of using a dust palliative for mitigating dust on a mining road (typical values).

      Table: Dust Palliative Cost Savings vs Water per Year

        Costs using water Costs using palliative Palliative savings
      Labour 500,000 50,000 450,000
      Fuel 250,000 25,000 225,000
      Tires 100,000 75,000 25,000
      Equipment maintenance 50,000 5,000 45,000
      Water permit penalties 50,000 0 50,000
      Lost production 1,000,000 200,000 800,000
      Road maintenance 100,000 40,000 60,000
      Water cost/water pump 50,000 10,000 40,000
      Palliative -- 1,000,000 (1,000,000)
      Total 2,100,000 1,405,000 695,000

      SHE comparison:

        Water Palliative
      Health - +
      Safety/lost time - +
      Environmental - +
      Community goodwill - +

      A study by du Plessis compared the efficacy of using a lignin-based dust palliative, compared with a water-only strategy to suppress dust on haulage roads related to mining activities. The study results showed that the required application frequency decreased by 50% when the road was treated with a lignin-based dust palliative.

      The water usage associated with this binder was reduced by 50.2% and dust fallout by 53.8%. From the study, the financial impact when using a lignin-based dust palliative compared to water on the maintenance, running and fuel cost of vehicles associated with dust suppression was calculated to be a net savings of 30%.

      9. How to pick a good dust control agent

      Choosing the correct dust control additive to suit your needs is important and can save you time and money in future maintenance and increase your productivity.

      Some questions you should ask yourself when selecting a dust control agent are:

      • Does the dust palliative comply with federal, state, and local laws and regulations?
      • Is it suitable for weather conditions and seasonal variations?
      • Is it suitable for the materials being treated?
      • Is it suitable for the type and amount of traffic?
      • Does the product have a good track record?
      • Is the additive a liquid or powder? Does it dissolve in water?
      • Is the necessary equipment available for application?
      • Is the road surface re-workable after it is treated with the additive?
      • When the additive is applied, does it need to be incorporated into the top few inches of road surface?
      • Will the additive wash away or erode? How soon? How cost-effective is it?
      • How frequently will re-application be needed?
      • Is the additive corrosive to equipment or vehicles?
      • What precautions are needed when using the additive?
      • Is it hazardous to humans when used according to the instructions?
      • Do remnants of the additive affect surrounding ecosystems?
      • Does the additive break down, and what becomes of the components?
      • Is the additive sustainably sourced and does it have a low carbon footprint?

      10. How do I apply dust control agents?

      The way to apply a dust suppressant depends on the type of additive, i.e. liquid or powder, and the type of surface to be treated, i.e. roads or stockpiles.

      The simplest form of dust control consists of a direct application onto an unprepared surface. If the dust palliative is a liquid or a powder that can dissolve in water, it can be sprayed onto the surface. This spray-on dust suppression method is used to treat roads, construction sites, earthworks, quarries, etc. The product may be applied either from a water cart as a diluted solution under pressure through spray nozzles, or simply through a hose.

      Some dust palliatives like salts can be applied either as powder or flakes spread evenly onto the surface. The surface is sometimes hydrated with water from a water truck.

      For optimal results in most cases, it is necessary to prepare the road prior to treatment. This includes ensuring that road materials are of high quality (proper percentage of fine material, correct plasticity, etc.) and if not, should be remedied by hauling in and applying the correct materials. The surface should be prepared with good crown and shoulder drainage (this can be difficult to correct afterwards). Usually, the road is scarified, breaking up the top few centimetres of soil surface to allow for quick and even penetration of the dust suppressant.

      Pre-watering before applying a dust suppressant might be necessary to assure optimum moisture content. Applying to dry areas may yield uneven absorption with the product sitting mostly on the surface and not penetrating to the desired level. Saturating the road with excessive water could cause runoff of the product.

      Curing time before you can allow traffic back on the road will depend on the type of suppressant additive and application method.

      Generally, higher application rates or increased frequency are required when there are high traffic volume, low humidity conditions, low fines content in the surface and a poorly bladed surface.

      For industrial applications such as stockpiles, load-out areas, railcar toppings, transfer points and underground mining roads, proper application is generally more specialised.  Application is dependent on the specific dust issues, types of processes and types of materials.  In such cases, it is important that you consult with the product manufacturer or with companies specialising in these applications.

      Read more about how to apply the sustainable lignin-based dust suppressant Dustex®.