Rapid City has a history of poor air quality conditions associated with dust (PM10) and has been in jeopardy of being designated a non-attainment area for PM10. It is in the community’s best interest to control and reduce dust (PM10) levels to the best extent possible to avoid a non-attainment designation. Our air quality is also influenced by smoke (mainly PM2.5) from forest fires, open burning and wood burning devices. Air quality is important to our community because it can affect the health of individuals with respiratory problems. The community’s economy is also affected by air quality. If the city is designated non-attainment, some businesses may not want to locate in this community or existing businesses may want to relocate. Other financial impacts include possible loss of highway construction funds and the imposition of more restrictive requirements on development and construction activities.
Rapid City’s air quality problems are caused by a combination of factors. Local topography, weather conditions, and the location of quarrying operations on the northwest edge of the city all contribute to air quality problems. Read more about Rapid City's air quality history. Episodes of poor air quality occur during high wind events and during periods of strong temperature inversions.
High winds cause air quality problems if conditions have been dry for several days and sustained winds exceed 20 mph and peak winds exceed 40 mph. These kinds of high winds usually come from the northwest as a cold front moves through the region. Dust from quarrying operations and other activities that expose soil is picked up by the high winds and dispersed throughout west Rapid City.
Strong temperature inversions cause air quality problems when the air temperature is near 32 °F, the average wind speed is less than 8 mph, and the inversion layer is less than 4500 feet. The bowl-like topography of west Rapid City created by the surrounding mountain ridges traps pollutants close to the ground during these periods of strong temperature inversions. Poor air quality results if these inversion conditions persist for more than 12 hours.
Rapid City’s predominant air quality pollutant is particulate matter (PM10 and PM2.5). Particulate matter consists of the solid particles and liquid droplets found in the air. Individually, these particles are droplets that are invisible to the naked eye. Collectively, they can appear as clouds or a fog-like haze.
Particulate matter can be directly emitted into the air through industrial mining operations, construction sites, wind-blown dust, tilled fields, unpaved roads, vehicles, crushing and grinding operations and burning of wood. Fugitive dust control measures are used to reduce the amount of dust that is generated from construction activities.
Other particulate matter may be formed in the air from a chemical change of gases, such as fuel combustion of motor vehicles, at power plants and from other industrial processes.
The Clean Air Act, last amended in 1990, requires the Environmental Protection Agency to set the National Ambient Air Quality Standards for six air pollutants, which are called the criteria pollutants. The six criteria pollutants are carbon monoxide, nitrogen dioxide, ozone, lead, particulate matter and sulfur dioxide. The Clean Air Act established two types of National Air Quality Standards. The Primary Standards are set to protect public health and the Secondary Standards are set to protect public welfare. Access the EPA’s website for the National Ambient Air Quality Standards, air pollution data and maps for South Dakota on the Airdata webpage or obtain environmental facts on air quality and other environmental issues at the EPA’s Envirofacts Data Warehouse.
To determine the quality of Rapid City’s air, the South Dakota Department of Environment and Natural Resources conducts air quality monitoring. Click here to view the locations of the air quality monitoring sites in Rapid City.
Locally, particulate matter from fugitive dust sources and burning are regulated within the Air Quality Control Zone by Pennington County Ordinance No. 12 and Rapid City Municipal Code Chapter 8.34.
Particulate matter is a health concern because it can penetrate into the sensitive regions of the respiratory tract. Particulate matter has been linked to:
- aggravation of asthma;
- increase in respiratory symptoms like coughing and difficult or painful breathing
- chronic bronchitis;
- decreased lung function; and
- premature death.
The people at most risk from particulate matter pollution are children, the elderly and people with cardiovascular or lung diseases.
Environmental impacts include reduced visibility, atmospheric deposition and aesthetic damage. Additional information regarding the health and environmental impacts of air pollution can be obtained through the Environmental Protection Agency website.