Air Pollution Control Program

State Implementation Plan

There are six different criteria pollutants for which the U.S. Environmental Protection Agency is required to set National Ambient Air Quality Standards, or NAAQS.  EPA is also required to review each national air standard every five years to determine if the current standard is still adequate to protect public health, or if it should be revised.

Once EPA revises or sets a new standard for a criteria pollutant, then EPA designates areas across the country as either nonattainment or attainment/unclassifiable based on air quality monitoring or modeling data. If an area is designated as nonattainment for a certain national air standard then this means the area either is not meeting the standard or is significantly contributing to an area that is not meeting the standard. Missouri’s State Implementation Plan, or SIP, is a compilation of all rules, regulations and documents that provide the state the authority to implement, enforce, attain, maintain and demonstrate compliance for each standard as required under the Clean Air Act. All State Implementation Plans are required to go through public comment periods and if adopted by the Missouri Air Conservation Commission, they are then submitted to EPA for adoption in the federally approved state implementation plan. If EPA adopts the plan submission, then the state implementation plan becomes federally enforceable. Missouri’s federally approved State Implementation Plan is available on EPA's website. Every time a standard is revised the state is required to submit a State Implementation Plan to EPA three years after the revised standard is published.

Types of State Implementation Plans

Every time an air standard is revised, the state is required to submit a State Implementation Plan. For attainment/unclassifiable areas, the state is required to submit an infrastructure State Implementation Plan that demonstrates the state’s authority to implement and enforce the standard and demonstrate that compliance with the standard will continue to be maintained. For nonattainment areas, the state is required to submit several different documents as part of the State Implementation Plan for these areas under each standard in which the area has been designated nonattainment. 

The scope of the different State Implementation Plan submittals required for each nonattainment area depends on the severity of the nonattainment area and the pollutant for which the area has been designated nonattainment. 

All nonattainment areas are required to submit an attainment demonstration State Implementation Plan.This portion of the State Implementation Plan lays out all of the control strategies required to demonstrate the nonattainment area will meet the new standard by a certain date, known as the attainment date. A Rate of Progress Plan or a Reasonable Further Progress Plan is only required for certain severity levels of ozone nonattainment areas. This State Implementation Plan document must show the plans and controls required to demonstrate that total emissions in the nonattainment area will decrease at least by 15 percent in the first six years and by 9 percent every three years after that until the area attains the standard. Finally, once an area that has been designated as a non-attainment area has monitored pollutant levels in compliance with the standard for three years, then the area can submit a maintenance plan and be redesignated to maintenance area. The maintenance plan must demonstrate how the area will continue to maintain compliance with the standard for 10 years after attainment has been reached.

This Web page shows the more recent State Implementation Plans submissions the state has made to EPA. Some submissions have been federally approved, while others are still pending EPA approval. State Implementation Plan elements are revised from time to time, and the more recent revisions to State Implementation Plans are also listed on this website.

Ozone | Particulate Matter | Lead | Carbon Monoxide
Nitrogen Dioxide | Sulfur Dioxide | Regional Haze | Interstate Transport

Ozone

The first Ozone NAAQS was published in 1979. The standard was based on one-hour average concentrations.  In 1997, EPA revised the ozone NAAQS and the new standard was based on a design value stemming from 8-hour average concentrations. In 2008, EPA again revised the ozone standard. The 2008 standard is lower than the 1997 standard, but still based on a design value stemming from 8-hour average concentrations. However, EPA is currently reconsidering the 2008 ozone standard that was set, and it could be changed again in 2011. More information is available on the department's Ozone Information Web page.

2008 8-hr O3 Standard: currently 75 parts per billion, or ppb

This standard is currently under reconsideration by EPA.When EPA promulgates the final standard the state will begin to develop the required SIP elements. Once developed and adopted by the Missouri Air Conservation Commission, the SIP documents will be placed here.

1997 8-hr O3 Standard: 80 ppb

This standard was published by EPA in 1997, but litigated in the courts until 2004. This standard is based on a three year design value, which is calculated by taking the fourth highest daily high 8-hour average concentrations recorded each year, for three years, and averaging the three years together. Due to rounding conventions, compliance with this standard is considered to be met when the highest monitored design value in an area is below 85 ppb.

St. Louis Area

Kansas City Area

Infrastructure SIP

1979 1-hr O3 Standard: 120 ppb

This standard was revoked when the 8-hour ozone standard was published in 1997. While the standard is revoked, the control strategies developed to address this standard are still in effect unless they have been replaced by more stringent control strategies. Compliance with this standard was met when monitored ozone values reflected that no more than one expected exceedance would occur annually.

St. Louis Area

Kansas City Area

Inspection and Maintenance SIPs

When new or revised National Ambient Air Quality Standards are published the EPA also releases implementation requirements for those new standards that must be included in State Implementation Plans. The I/M Program is required by ozone implementation rules for all moderate ozone non-attainment areas.  This State Implementation Plan defines the passenger vehicle emission inspection requirements for vehicles registered within the St. Louis ozone non-attainment area. More information is available on the Gateway Vehicle Inspection Program Web page.

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Particulate Matter

Particulate matter is divided into two different groups based on the health effects of smaller sized particles. Fine particles are those particles smaller than 2.5 microns in size (PM 2.5). Coarse particles are those particles smaller than10 microns in size (PM 10). More information is available on the department's Fine Particulate Matter Web page.

PM (2.5)

2006 PM(2.5) Standard:

Annual Standard: 15 micrograms/cubic meter; 24-hr Standard: 35 micrograms/cubic meter

Compliance with the annual standard is based on the 3 year average of the annual arithmetic mean. The 24-hour standard is based on a three year design value, which is calculated by taking the 98th percentile of the daily high 24-hour average concentrations recorded each year, for three years, and averaging the three years together. The entire state is currently designated as attainment or unclassifiable under this standard.

Infrastructure SIP

1997 PM (2.5) Standard

Annual Standard: 15 micrograms/cubic meter; 24-hour standard: 65 micrograms/cubic meter

Compliance with the annual standard is based on the three year average of the annual arithmetic mean. The 24-hour standard is based on a three year design value, which is calculated by taking the 98th percentile of the daily high 24-hour average concentrations recorded each year, for three years, and averaging the three years together.

St. Louis Area

 

Infrastructure SIP

PM(10)

2006 24-hr PM(10) Standard: 150 micrograms/cubic meter

The 24-hour PM(10) standard was unchanged in 2006. This standard is violated if the three-year average of the highest 24-hour concentration each year exceeds 150 micrograms/cubic meter. The 2006 revision also revoked the annual PM(10) standard. The entire state is currently designated as either attainment or unclassifiable under this standard.

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Lead

Additional information, including health effects and air monitoring of lead is available on the department's Airborne Lead Web page.

2008 Standard: 0.15 micrograms/cubic meter

Plans are currently being developed they will be added when adopted by the Missouri Air Conservation Commission and submitted to EPA. Compliance with this standard is based on a three month rolling average.

Infrastructure SIP

1978 Standard: 1.5 micrograms/cubic meter

Compliance with this standard is based on the average monitored values of a three month calendar quarter.

Herculaneum area

Glover area

Buick

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Carbon Monoxide

Additional information is available on EPA's Carbon Monoxide Web page.

2011 Standard - 1-hour standard: 9ppm; 8-hour standard: 35 ppm

The 1-hour and 8-hour values for this standard were not changed in 2011, however monitoring requirements for this standard are expected to require that near roadway monitors be placed in areas with high population counts. A violation of this standard occurs if either the 1-hour average or 8-hour average standards are exceeded more than once in a year.

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Nitrogen Dioxide (NO2)

Additional information is available on EPA's Nitrogen Dioxide Web page.

2010 Standard: Annual Standard: 0.053 ppm; 1-hour standard: 100 ppb

Monitoring requirements for this standard are expected to require that near roadway monitors be placed in areas with high population counts. The entire state of Missouri is currently designated as attainment or unclassifiable under this standard. A violation of this standard occurs if the monitored annual arithmetic mean exceeds this standard.The 1-hour standard is based on a three year design value, which is calculated by taking the 98th percentile of the daily high 1-hour average concentrations recorded each year, for three years, and averaging the three years together.

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Sulfur Dioxide (SO2)

Additional information is available on the department's Sulfur Dioxide Web page.

2010 Standard: 1 hour standard: 75 ppb

In 2010, this standard was revised. The revised standard revoked the annual and 24-hour standards. Previous to this recent NAAQS revision, the entire state was designated as attainment or unclassifiable under the annual and 24-hour standards.  Under this revised standard, modeled pollutant concentrations are expected to be used to designate nonattainment and attainment areas. The state is currently developing recommendations to be submitted to EPA for the boundary designations under this standard. This standard is based on a three year design value, which is calculated by taking the 99th percentile of the daily high 1-hour average concentrations recorded each year, for three years, and averaging the three years together.

Secondary standard (3-hour average): 500 ppb

The secondary standard for SO2, is currently under consideration for revision. The entire state is currently designated as attainment or unclassifiable under this standard.

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Regional Haze Plan

All states were required by the Clean Air Act to submit Regional Haze SIPs in order to address visibility in Class I areas.  This SIP addresses pollutants that affect visibility, and also those that cause acid rain.

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Interstate Transport SIPs

Under Section 110.A.2.D. of the Clean Air Act, states are required to submit SIPs in order to demonstrate that emissions in their state do not have a significant impact on downwind states’ ability to meet or maintain the NAAQS for all criteria pollutants. Typically, ozone and particulate matter are the two criteria pollutants in which long range transport of pollutants and precursors can have a significant impact on downwind states.

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