Particulate Matter and Dust

Particulate Matter
Particulate matter is essentially small particles that are suspended in the air and settle to the ground slowly.  These particles may be re-suspended if disturbed.  The most common sources of particulate matter from oil and gas operations are dust or soil entering the air during pad construction or from traffic on access roads, and diesel exhaust from vehicles and engines used to power machinery at oil and gas facilities.  Particulate matter can also be emitted during venting and flaring operations.

PM10 particles (with a diameter less than 10 micrometers) are small enough to be inhaled and can cause adverse health effects. 

PM2.5 particles (with a diameter less than 2.5 micrometers) can lodge deep within the lungs and cause serious health problems.  They are the main cause of visibility impairment, or haze.  Secondary particles are formed as a result of chemical reactions involving gases and other particles in the atmosphere.  Particles formed in this manner are fine particles.  The most common precursor gases involved in these reactions are nitrogen oxides (NOx), sulfur dioxide (SO2), volatile organic compounds (VOCs), and ammonia (NH3).  NOx, SO2, and VOCs are emitted during oil and gas operations. 

PM2.5 can cause respiratory ailments, painful breathing, chronic bronchitis, and premature death.  Some particulates, such as diesel exhaust, are carcinogenic. 

Dust
Dust can cause nuisances such as hay fever and allergies.  Crops and vegetation near unpaved roads can be covered with airborne dust, stunting their growth due to the shading effect and clogging of the plants' pores.  As a result, cattle and wildlife may avoid this vegetation. 

Dust Suppression

Water is probably the oldest of all dust suppressants. Typically, it is applied by spraying it over the road surface. 
Drawbacks: Water's dust suppressing capacity is very temporary because of evaporation. Heavy applications of water can create soft mud or penetrate the road to the sub-base, causing major road failure. Consequently, several light applications are preferable to one heavy application.

Chloride compounds such as calcium chloride (CaCl2), magnesium chloride (MgCl2) and the less popular sodium chloride (NaCl2) are used because they attract and absorb moisture from the atmosphere and retain it for extended length of time, which significantly reduces the evaporation of moisture from the road surface. Thus, they are more effective dust suppressants than plain water.
Drawbacks: Chloride compounds have the disadvantage of dissolving in water, and therefore can be washed out during wet weather conditions. They are also corrosive.

Lignin derivatives include a variety of industrial waste products, animal fats, and vegetable oils; the most popular is ligninsulfonate, which is a waste product from the paper-making industry. When used as dust suppressant, the lignin polymers act as glue binding the soil particles together. According to the New Mexico State University Molecular Biologic Program, a by-product of the soybean crushing process, called soapstock, is now being used as dust suppressant on dirt and gravel roads throughout the Midwest. This alternative is said to be more environmentally safe in places where runoff is a concern, and supposedly lasts longer than most other alternatives.
Drawbacks: Ligninsulfonate dissolves in water, and so it is easily washed away during wet weather conditions.

Resinous adhesives include waste oils, tars, bitumen, and by-products from the plastic industry. Of all these products, cutback asphalt and asphalt emulsions are most widely used as dust suppressants. 
Drawbacks: According to the Minnesota Pollution Control Agency, "When applied to roads, waste oil can seep into groundwater, runoff into surface waters or spread into the air with dust particles. Once in ground or surface waters even small amounts of used oil can contaminate large quantities of drinking water. . . Used oil reduces the amount of oxygen in water, damaging fish and other aquatic life."  Consequently, waste oils are prohibited from use as a dust suppressant in Minnesota.Very little quantitative information currently exists on the environmental impacts from the use of dust suppressants (other than water). Landowners should be aware that the application of dust suppressants has been noted to cause slipperiness on unpaved roads in wet weather conditions. The water quality effects of the use of dust suppressants are still not entirely known, however the chloride compounds and the lignin additives commonly used contain contaminants such as chlorides, heavy metals and organic compounds that are regulated by the U.S. Environmental Protection Agency.