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Contact information
For information on particle pollution, contact:
Karen Walsh

Particle pollution

Particle pollution, also called particulate matter or PM, is solid particles or liquid droplets suspended in the air. Exposure to these suspended particles and droplets can cause serious health problems in humans, especially those with respiratory conditions such as asthma and cardiac disease. The DNR's Air Management Program monitors particle pollution around the state and issues advisories when levels become potentially harmful.

To reduce particle pollution, state and federal regulations target nitrogen oxides (NOx) and sulfur dioxide (SO2) emissions from power plants and industrial combustion sources. Additionally, mobile source control programs, such as low-emission vehicles and cleaner gasoline, help reduce volatile organic compounds (VOC) and NOx emissions from mobile sources.


Particle pollution basics

Particle pollution is defined as solid particles or liquid droplets that are suspended in air. These can be fine particles with an aerodynamic diameter of 2.5 microns or less (PM2.5), inhalable coarse particles with an aerodynamic diameter of 10 microns or less (PM10) or Total Suspended Particles (TSP) with an aerodynamic diameter of 100 microns or less. In Wisconsin, the DNR monitors inhalable coarse and fine particles. For a sense of scale, the average human hair is 70 microns in diameter.

Fine particles (PM2.5)

Fine particles (PM2.5) may be emitted directly into the atmosphere but are more commonly created by reactions of other pollutants. Fine particles in the air may be consist of hundreds of different chemicals, but sulfur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOC) and ammonia are the basic building blocks for most of the fine particles. Sources of fine particle emissions include forest fires and wood stoves. Sources of the precursor pollutants that chemically react to form fine particles include power plants, industries and automobiles. Wind can carry fine particles hundreds of miles from their sources. Fine particle.levels typically peak in winter but concentrations can also be high in summer.

Coarse particles (PM10)

Inhalable coarse particles usually result from some type of mechanical action such as crushing or grinding, or from wind-blown dust. Sources of inhalable coarse particles include roadways and dusty industries. Inhalable coarse particles are typically not transported great distances.

Total Suspended Particles (TSP)

Total Suspended Particles (TSP) consist of particles typically less than 100 microns in size. Wisconsin has a TSP standard to help protect citizens from damage caused by TSP. There are several TSP monitors operated by industrial facilities and audited by DNR staff. Currently there are no areas in Wisconsin that are violating the state TSP standard.

Health effects

Both inhalable coarse and fine particles pose health problems, because they can bypass the body's natural defense mechanisms and affect both the lungs and heart. Scientific studies have linked particle pollution exposure to a variety of health problems, including:

  • increased coughing or difficulty breathing;
  • decreased ability of the lung to transfer oxygen to the lung;
  • aggravated asthma;
  • chronic bronchitis;
  • irregular heartbeat;
  • nonfatal heart attacks; and
  • premature death in people with heart or lung disease.

People with heart or lung diseases, children and older adults are the most likely to be affected by particle pollution exposure. Even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particle pollution. For more information about asthma, visit Air Quality Information for Health Professionals and the U.S. Environmental Protection Agency [exit DNR].

Environmental effects

Particle pollution scatter light and is the major cause of reduced visibility in the United States. Many fine particles can also be acidic, causing acid rain and making lakes and streams more acidic. Deposition of nitrogen-containing particles may change the nutrient balance in lakes and rivers, affecting the diversity of ecosystems or damaging forests or crops. In addition, particle pollution can damage statues, monuments and buildings made of stone and other materials.

For more information


Overview of particle pollution standards

The federal Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to develop two types of air quality standards for key air pollutants.

  1. Primary standards - These standards protect public health, including the health of groups especially affected by air pollution, such as individuals with asthma or cardiac disease, children and the elderly.
  2. Secondary standards - These standards protect public welfare and the environment, including protection against damage to animals, crops and buildings.

There are also three primary national ambient standards for particle pollution.

  1. Annual PM2.5 – 15µg/m3 (arithmetic annual mean concentration)
  2. 24-Hour PM2.5 – 35 µg/m3 (98th percentile average concentration)
  3. 24 Hour PM10 – 150 µg/m3 (maximum concentration)

The secondary standards are currently the same as the primary standard for particle pollution. For more details see National Ambient Air Quality Standards [exit DNR].


Compliance and nonattainment areas

Particle pollution's harmful effects on human health and the environment prompted the federal government to set air quality standards for the amount of particle pollution in the air over certain time periods. Counties that do not meet these federal standards receive a nonattainment designation that triggers increased pollution control requirements for businesses in the area, along with other efforts to reduce particle pollution levels.

Nonattainment designation

When a county is identified as not meeting a federal air quality standard based on monitored values of the outside air, it is designated by the U.S. Environmental Protection Agency (EPA) as nonattainment and given a target date to meet the standard. State plans are then prepared that include regulations for controls on emissions needed to reduce the air pollution and meet the standard. If at any time monitoring data shows that air quality has improved and the county now meets the standard, the state can request EPA to redesignate the county to attainment status.

On October 8, 2009, the EPA issued new information regarding PM2.5 designations.

Attainment demonstrations

An attainment demonstration is a plan that ensures that an area with an air quality problem like nonattainment will attain the air quality standards in the requisite time period. The plan contains the necessary analyses and control program to demonstrate that enough pollutants have been removed from the atmosphere so that pollutant concentrations will not exceed the federal standard in the future.

Control strategies and regulations

Although Wisconsin has yet to develop rules for stationary sources that directly address particle pollution, there are a number of control programs designed to meet other Clean Air Act requirements that provide reductions in the pollutants that form fine particles. Those programs include:

  • Wisconsin's acid rain program, which limits emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) from power plants;
  • the EPA's Clean Air Interstate Rule [exit DNR], which further limits SO2 and NOx from power plants; and
  • Reasonably Available Control Technolgy (RACT) for volatile organize compounds and NOx in southeastern Wisconsin, designed to address high ozone concentrations in the area.
Mobile aources

There are several state and federal pollution-control programs aimed at mobile sources, including both highway vehicles, such as cars, and off-road equipment, such as all-terrain vehicles (ATVs). The federal government also regulates the fuels these vehicles and other equipment use, with a goal of having cleaner-burning fuels that do not contribute as much air pollution. Regulations include motor vehicle emission standards, vehicle inspection and maintenance, the required use of reformulated gasoline, ultra-low sulfur diesel fuel, low sulfur gasoline, and gasoline vapor-recovery programs.

For more information on mobile sources visit our Vehicles (mobile sources) page.

Voluntary reduction programs

In some areas, governments, businesses and partner organizations have developed local and regional voluntary programs to reduce air pollution.


Visibility protection and haze

Visibility is degraded when light is scattered by tiny particles in the air, which reduces the clarity and color of what we see. This is referred to as haze and often occurs when the air is humid. Haze degrades visibility in many American cities and scenic areas. Air pollutants that contribute to fine-particle formation and haze come from a variety of natural and manmade sources.

The U.S. Environmental Protection Agency's (EPA) Regional Haze Rule calls for state and federal agencies to work together to improve visibility in 156 national parks and wilderness areas [exit DNR], including the Grand Canyon, Yosemite, the Great Smoky Mountains and Shenandoah. These parks and pristine areas are called Class I Areas.

The haze rule requires that states, in coordination with EPA, the National Park Service, U.S. Fish & Wildlife Service, the U.S. Forest Service and other interested parties, develop and implement air quality protection plans to reduce the pollution that degrades visibility. The overall goal is to eliminate the manmade effects on visibility by the year 2064. Interim milestones were established to insure that states are on track to meet the 2064 goal. The first state plans for regional haze were due in December 2007. Wisconsin has not yet submitted its haze plans, but the DNR is working with surrounding states, federal land managers and tribes to develop the plans.

Visit EPA's haze program [exit DNR] to learn more about the haze rule.

Regional planning organizations

Map of regional planning organizations in the continental United States.

Because regional haze can originate from sources located across large geographic areas, EPA has encouraged the states and tribes to address visibility degradation from a regional perspective. Five regional planning organizations have been created to address regional haze.

Midwest Regional Planning Organization

Wisconsin is a member of the Midwest Regional Planning Organization (Midwest RPO) that was formed to facilitate regional planning to address the regional haze regulations adopted by in 1999. The primary objective of the Midwest RPO is to assess both visibility impairment due to regional haze in the mandatory Federal Class I areas located inside the borders of five Midwestern states – Illinois, Indiana, Michigan, Ohio and Wisconsin – and the impact of emissions from those states on visibility impairment due to regional haze. Members of the Midwest RPO include the five states, tribes, federal land managers and EPA. For more information, please visit the Midwest Regional Planning Organization [exit DNR].

For more information on the other four planning organizations, please visit the following web sites.

Wisconsin's regional haze Site Implementation Plan (SIP)

A Site Implementation Plan (SIP) helps describes a state's strategy for meeting certain air quality goals regarding visibility. In Wisconsin, the Midwest Regional Planning Organization (MRPO) has shown that the state's emission sources impact visibility in four of the 156 mandated Class I areas listed under the Regional Haze Rule of the Clean Air Act – two areas in northern Michigan and two areas in northern Minnesota.

Wisconsin must submit to the EPA an SIP to demonstrate it is making sufficient efforts to help meet reasonable progress goals for visibility improvement at these Class I areas. The SIP describes Wisconsin's strategy for meeting the progress goals by 2018 for these four Class I areas, with the eventual goal of achieving pristine visibility conditions by 2064. This strategy takes advantage of emissions reductions from various control programs, and includes submission of a plan for the application of Best Available Retrofit Technology (BART) for specific emission sources.

The DNR proposed Regional Haze SIP requirements in July of 2011 for public comment. The Department received comment from Georgia Pacific, U.S. Forest Service, National Parks Service, EPA and joint comments from Sierra Club and the Midwest Environment Defense Center. The DNR has provided response to these comments and has amended the Wisconsin Regional Haze SIP accordingly.

The following documents support Wisconsin's Regional Haze SIP. The Regional Haze SIP is divided into three parts: 1) Wisconsin Regional Haze SIP, 2) Wisconsin's Implementation of BART and 3) Revisions to Wisconsin's State Implementation Plan for Protection of Visibility. The public comments received on the July 2011 proposed Regional Haze SIP are also included below.

Wisconsin's implementation of BART
  • Cover Letter [PDF] — Implementation of BART
  • Attachment 1 [PDF] — U.S. EPA SIP checklist
  • Attachment 2 [PDF] — Draft BART Technical Support Document for EGUs — Dated July 1, 2011
  • Attachment 3 [PDF] — Draft BART Technical Support Document for Non-EGUs — Dated July 1, 2011
  • Attachment 4 [PDF] — Final BART Determination and Summary of Changes from Draft Technical Support Documents
  • Attachment 5 [PDF] — BART Modeling for PCA-Tomahawk, Thilmany, and Wausau-Mosinee
  • Attachment 6 [PDF] — Draft Administrative Order (AO) for Georgia Pacific
    * To be finalized after proposedapproval by the U.S. EPA
  • Attachment 7 [PDF] — Template for EGU BART Permit Revisions for Implementation of BART
    * To be finalized in EGU specific permits after proposed approval by the U.S. EPA
  • Attachment 8 [PDF] — BART Analysis Submitted by Georgia Pacific
  • Attachment 9 [PDF] — Proof of Public Hearing on July 29, 2010 (Response to Public Comments Included in Attachment 3)
  • Attachment 10 [PDF] — Proof of Public Hearing on September 13, 2011 and Summary / Response to Public Comments
Revisions to Wisconsin's State Implementation Plan for Protection of Visibility
  • Cover Letter [PDF] — BART Rule
  • Attachment 1 [PDF] — U.S. EPA SIP checklist
  • Attachment 2 [PDF] — Chapter NR 433, Wis. Adm. Code, as amended
  • Attachment 3 [PDF] — Section NR 484 (11m), Wis. Adm. Code
  • Attachment 4 [PDF] — Proof of public hearing, including public hearing notice, for BART rules adoption. Copy of legal notice from February 9, 2007 Wisconsin State Journal
  • Attachment 5 [PDF] — Background for AM-04-06 and public comments received for BART rules adoption — summary and response
  • Attachment 6 [PDF] — Proof of public hearing, including public hearing notice, for BART rules revision. Copy of legal notice from March 22, 2010 Wisconsin State Journal
  • Attachment 7 [PDF] — Background for AM-06-09 and public comments received for BART rules revision — summary and response
Comments received on July 2011 Regional Haze SIP

Improving visibility

There are a number of efforts underway to help improve visibility in Class I areas. They include Best Available Retrofit Technology (BART) requirements, reasonable progress and regional haze consultation.

Best Available Retrofit Technology (BART)

Best Available Retrofit Technology (BART) affects certain large sources of NOx, SO2 or direct particle pollution. The BART relates only to sources that began operation between 1962 and 1977. The federal regional haze regulation requires that BART determination be based on an analysis of the best system of continuous emission control technology available, performed on a source-by-source basis taking into account the following criteria:

  • the costs of compliance;
  • the energy and non-air quality environmental impacts of compliance;
  • any pollution control equipment in use at the source; and
  • the remaining useful life of the source.

Wisconsin's BART rule establishes a procedure for determining requirements to control SO2, NOx and particle pollution emissions from sources subject to BART, which are mainly boilers at electric generating power plants and at pulp and paper facilities. However, please note that the electric generating power plants subject to BART do not need to install, operate and maintain BART for SO2 and NOx controls if they are subject to the SO2 and NOx trading programs that are part of the Clean Air Interstate Rule (CAIR).

Reasonable progress

Wisconsin, as all other states, must develop a plan to address reasonable progress in all Class I areas where emissions from the state significantly contribute to visibility degradation. The purpose of reasonable progress is to insure that continuing progress is being made toward the 2064 visibility goal. The reasonable progress plan must address five factors which should be considered in evaluating potential emission control measures to meet visibility goals:

  • cost of compliance;
  • time necessary for compliance;
  • energy and non-air quality environmental impacts of compliance;
  • remaining useful life of any existing source subject to such requirements; and
  • uniform rate of progress.
Regional Haze Consultation - Northern Class I Areas

Michigan and Minnesota, along with representatives of other states – including Wisconsin – tribal governments and federal agencies are working to address visibility impairment due to regional haze in four northern class I areas: Boundary Waters Canoe Wilderness Area, Voyageurs National Park, Isle Royale National Park and Seney National Wilderness Area.

To support consultation in the development of reasonable progress plans for the Northern Class I Areas, the interested parties created a technical document that addresses the causes of visibility degradation in the area. The key findings of the document are as follows.

  • The chemical species which affect visibility impairment include ammonium sulfate and, to a lesser degree, ammonium nitrate and organic carbon.
  • The pollutants and source sectors that contribute the most to visibility impairment include:
    • sulfur dioxide emissions from power plants/electrical generating units (EGUs) and certain non-EGUs, which lead to sulfate formation;
    • nitrogen oxide emissions from a variety of sources such as motor vehicles, which lead to nitrate formation; ammonia emissions from livestock waste and fertilizer applications are also important, especially for nitrate formation; and
    • organic carbon concentrations, which are thought to be mostly secondary organic aerosols of biogenic origin and, on an occasional episodic basis, from fire activity.
  • The source states that contribute the most to visibility impairment are Michigan, Minnesota and Wisconsin. Other nearby states contributing to visibility.
  • Current visibility levels are well above natural conditions.

For more information, read LADCO's Regional Haze in the Upper Midwest: Summary of Technical Information [PDF exit DNR].

Minnesota “Ask”

Through the regional consultation process, the Minnesota Pollution Control Agency (MPCA) determined that Wisconsin significantly contributes to visibility impairment at Boundary Waters Canoe Area Wilderness and Voyageurs National Park. The MPCA asked the states that contribute to visibility impairment at those sites to consider the following control programs when developing their visibility plans.

  • Implement BART
  • Statewide average emission rate for power plants to match Minnesota's voluntary emission rates
    • NOx – 0.25 lbs/mmBtu
    • SO2 – 0.25 lbs/mmBtu
  • Continued assessment of reasonable measures for industrial/commercial/institutional boilers, reciprocating engines and turbines

For more information, see Minnesota's regional haze plan [exit DNR].

Vermont “Ask”

Through the regional consultation process with the Mid-Atlantic/Northeast Visibility Union (MANE-VU), Vermont determined that Wisconsin significantly contributes to visibility impairment at Lye Brook Wilderness Area. Vermont asked the states that contribute to visibility impairment at Lye Brook to consider the following control programs when developing their visibility plans.

  • Implement BART
  • 90 percent SO2 reduction at selected power plants
    • Pleasant Prairie is the only identified power plant in Wisconsin and is already installing scrubbers that would meet that 90 percent goal.
  • 28 percent SO2 reduction from non-power plant sources
    • The 28 percent reduction is relative to 2018 on-the-books emission projections.

For more information on Vermont's regional haze plan, please see the Summer haze event [exit DNR].


Particle pollution resources and air monitoring data

There are a number of resources regarding air monitoring available to the public, for both in Wisconsin and around the country. There are also publications about particle pollution health effects and links to information about air quality watches and advisories, as well as technical documents related to particulate matter rules at both the state and federal levels.

Air quality forecasts and monitoring data
Particle pollution health information

The DNR also has additional air outreach resources available.

Air quality advisory program
Important particle pollution documents

The following documents and links provide technical information on regulations, including proposed federal and state rules, information about particle pollution rule violations and information on attainment with federal air quality standards.

PM2.5 redesignation

Redesignation request

Under the federal Clean Air Act (CAA), the U.S. Environmental Protection Agency (EPA) is required to identify areas that do not meet National Ambient Air Quality Standards (NAAQS) for particle pollution (PM2.5). In 2009, Milwaukee, Racine and Waukesha counties were designated nonattainment by EPA [PDF exit DNR].

In June 2012, the DNR submitted a request to EPA to redesignate these counties from nonattainment to attainment based on monitoring data collected betweeen 2008-2011. Learn more about Wisconsin's air quality trends.

In light of a recent court decision (Natural Resources Defense Council v. EPA), EPA requested that states, including Wisconsin, supplement their redesignation requests with additional information. This document is intended to fulfill this request: Supplemental Information for a June 2012 Redesignation Request and Maintenance Plan for the 24-Hour Fine Particulate Matter National Ambient Air Quality Standard [PDF].

On February 18, 2014, EPA published a Federal Register notice proposing to redesignate the three counties to attainment for the 2006 24-hour PM 2.5 health standard. The EPA proposes to approve all parts of Wisconsin's plan. Comments were due to EPA by March 20, 2014.

Redesignation documents

Last revised: Tuesday March 25 2014