Particulate matter and coal dust

Airborne Particles

Airborne particles––also known as particulate matter (PM), particulates, or aerosols––refer to any mixture of solids and liquid droplets in the atmosphere. Particles can be directly emitted into the air or formed through chemical reactions of gaseous pollutants.

Particles are often distinguished by their size. The terms PM₁, PM_2.5, and PM₁₀ are common ways particles are described, measured, and regulated, with the number indicating the diameter of the particles in micrometers. Particles can also be discussed in the terms of very-fine (PM₁), fine (PM_2.5), and coarse (PM₁₀) particles, with PM₁₀ generally referring to as dust. Particle size, composition, and shape affect how particles are regulated under the U.S. Clean Air Act and their health impacts.

Coal Dust

Coal dust is a type of particulate matter that contains coal. Coal dust particles tend to be larger in size, including PM_2.5 and PM₁₀, as well as even bigger PM that is visible with the unaided eye. Coal dust is lost from the atmosphere through settling and deposition, leaving black dust films on outdoor and indoor surfaces. Coal dust contains toxic heavy metals that have serious health impacts at ambient concentrations and exposures below the U.S. Environmental Protection Agency National Ambient Air Quality Standards (NAAQS).

Coal Dust Emissions

Coal dust is produced through physical processes that wear on the brittle coal rocks during mining, transport, and storage to generate coal particles that are then uplifted to the atmosphere and carried by winds. There are various physical disturbances that can unsettle coal particles and uplift them into the air. The distance traveled by the coal dust emissions depends on the size of particles, with smaller particles generally reaching farther distances, and the conditions in the atmosphere. Physical disturbances influencing coal dust emissions and downwind impacts include weather and wind patterns and the transporting and handling of coal.

Wind and weather disturbances

In Southeast Newport News, coal is stored in large open piles, and these stockpiles are susceptible to wind erosion with coal particles easily becoming airborne. The wind speeds over the coal piles influence the coal dust emissions and transport downwind, with higher wind speeds associated with higher airborne particle concentrations. As wind speeds increase, atmospheric particulate matter in the air increases, and there is an overall increase in dust fluxes to the atmosphere of particulates such as coal. The direction of airborne dust travel is determined by the wind direction. Higher particulate matter and black carbon concentrations have been observed in the neighboring community when winds blow from of the Curtis Bay coal export terminal.

Rain events are associated with lower airborne coal dust concentrations, as the water droplets reduce both dust emissions and force airborne particles out of the air and back to the surface through a process called wet deposition. This is similar to the use of water sprayers for wet dust suppression.

Relative humidity influences coal dust particle size, with higher humidity associated with larger particles as the dust particles clump together. Lower humidity increases the overall concentration and the amount of fine dust particles specifically.

In January 1987, the Virginia Air Pollution Control Board (APCB) published a study on coal dust emissions from the terminals in Southeast Newport News titled, Control of Fugitive Emissions from Open Coal Storage in Newport News, Virginia. As part of this study, the researchers developed a mathematical formula for the effective wind forces (K_t) on the terminals' coal piles using readily available meteorological measurements. Here, SP is the wind speed in miles per hour, T is air temperature in °F, RH is relative humidity (%), P is the air density in pounds (lbs) per cubic feet, and μ is the air viscosity in lbs per cubic feet hours. The constant of 1.68 is the value of P divided by μ at standard conditions of 70°F, RH of 60%, and P of 29.92 inches Hg. The term T/RH reflects the tendency of the coal piles to emit particles when temperatures are high and/or RH is low.

$K_t=SP\left(\frac{T}{RH}\right)\left(\frac{P}{\mu *1.68}\right)$

The relationship between the measured total airborne particle concentration and the daily summed Kt for those sample days. This line is labeled TSPunc/t. The second line, labeled CEunc, shows only the un-combusted coal portion of those measured particles. The title reflects that the total particles were measured using a hi-volume sampler and "EK_t" should read "ΣK_t". This is figure 3 in the 1987 study Control of Fugitive Emissions from Open Coal Storage in Newport News, Virginia.

This equation was developed to guide and optimize wet dust suppression with sprayers in Southeast Newport News. The 1987 study reported a strong relationship between the daily summed K_t and the amount of particles measured using a high-volume air sampler. The 1987 APCB study cited a 1984 study from the U.S. Environmental Protection Agency (EPA) Office of Air, Noise and Radiation, and the Office of Air Quality Planning and Standards as having reported dust emissions can become significant at winds of 12 miles per hour. We note that we instead found a similar report from 1985, archived below.

Coal transporting and handling disturbances

Transportation of coal: The transport of coal in uncovered open-top rail cars results in significant amounts of coal dust being emitted into the air by the jostling of the rail cars or due to wind and weather. Along the transportation route, coal dust can blow over residential and agriculture areas, polluting the air, crops, and waterways. The company BNSF has conducted studies that indicate 500 lbs to 1 ton of coal can escape from a single coal car during travel along a railway.

Coal handling: Loading and unloading piles of coal from rail cars into coal piles can unsettle dust particles which get released into the air.

• • Equipment at the terminal which manages and moves coal piles, such as bulldozers and conveyor belts, can release coal dust into the air.
  • The transfer of coal onto ships at the port can similarly unsettle dust particles.
  • In June 1989, Virginia's Department of Air Pollution Control Board set limits on the emissions from each ship unloading operation, each conveyor belt, the bucket elevator, silo airslides, and the truck loadout system to 0.3 lbs/hr for both particulate matter and PM₁₀ for each respective coal handling operation.
    • In July 1994, this emission limit was increased to 1.6 lb/hr.

Evidence of Atmospheric Coal Particulate Deposition

In a study conducted at the Lambert’s Point Docks, sample soils were collected to examine the extent of particulate coal and the associated Arsenic deposition to local soils.  The amount of particulate coal that occurs in the surface soil samples (4cm depth) of the study area averaged 7.1 weight% and an associated mean Arsenic value of 13.3 mg/kg. There was a decrease in the amount of particulate coal with increasing distance from Lambert’s Point Dock. There was also an increase in the amount of particulate coal eastward of Lambert’s Point Dock (the prevailing wind direction for the region is from the west). These results indicate that much of the Hampton Roads region of Southeastern Virginia has experienced atmospheric deposition of particulate coal, along with As concentration, originating from the Lambert’s Point Docks.

• Another study by William Joseph Bounds, Old Dominion University, sought to determine the distribution of coal dust added to the local soils by the coal shipping processors occurring at Lamberts Point Docks. These results indicated substantial levels of coal dust within the soils of the study area, with coal levels ranging from 3.2 weight% to 19.9 weight%. Additionally, arsenic levels ranged from undetectable levels to 17.4 mg/kg in these coal samples.
• July 2017, The Virginia Department of Health examined potential public health implications of particulate matter measuring 10 microns (PM₁₀) and less generated by the Norfolk Southern’s Coal Pier at Lambert’s Point coal terminal. Monitors located at Hampton Roads Sanitary Department facility (north of coal piers) and east of the pier administration building collected an average of 14.46 and 17.58 µg/m³, respectively. The study detected a PM₁₀ concentration below the NAAQS PM10 standard (150 µg/m³), claiming it is not expected to harm people’s health. It’s important to address that there is an apparent gap between residential local scientific knowledge and the results of this study.
• Tidewater Air Monitoring Evaluation (TAME) project is an ongoing Virginia Department of Environmental Quality 18-month investigation to study atmospheric toxic metals and particulates at Lambert’s Point and East End communities. They hope to study and reduce the potential health risks associated with dust coming from nearby coal storage and transportation facilities. If you live in Lambert's Point or the Southeast communities and would like to host a sensor, please contact John Brandt at john.brandt@deq.virginia.gov or (757) 407-2341.
• Have not been able to locate data and/or research on coal particulate air pollution in adjacent communities.

Documents

• EPA Office of Air, Noise and Radiation, and the Office of Air Quality Planning and Standards, Compilation of Air Pollution Emission Factors, January 1985
• Virginia Air Pollution Control Board, Control of Fugitive Emissions from Open Coal Storage in Newport News, Virginia, 1987
• Aneja et al., Particulate matter pollution in the coal-producing regions of the Appalachian Mountains: Integrated ground-based measurements and satellite analysis, Journal of the Air & Waste Management Association, 67, 4, 421–430, doi:10.1080/10962247.2016.1245686, 2019
• Coal Dust Residues on Homes in Southeast Newport News, 2024–2025 Photographs

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  Coal Dust Residues
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  Coal Dust Residues
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  Coal Dust Residues