Air quality in Wisconsin

Air quality index (AQI) and PM2.5 air pollution in Wisconsin

Last update at (local time)


Real-time Wisconsin
Most polluted city ranking

#cityUS AQI
1 Manitowoc


2 Kenosha


3 Pleasant Prairie


4 Sheboygan


5 Bayside


6 Sparta


7 Chetek


8 Augusta


9 Eau Claire


10 Delafield


(local time)


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Real-time Wisconsin
Cleanest city ranking

#cityUS AQI
1 Rhinelander


2 Shell Lake


3 Ashland


4 Boulder Junction


5 Turtle Lake


6 Waunakee


7 Crandon


8 Mount Horeb


9 Siren


10 Hudson


(local time)

Unhealthy for sensitive groups
Very unhealthy
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How to best protect from air pollution?

Reduce your air pollution exposure in Wisconsin


Is Wisconsin a state with high pollution levels?

Wisconsin is a state in the Upper Midwest region of the United States, bordered by four other states and Lake Michigan to the east and Lake Superior to the north. Wisconsin is the 23rd largest state by total area. In 2019, the estimated population was just over 5.8 million people. The state capital is Madison and is second in size to Wisconsin’s largest city, Milwaukee.

Looking back over the historic data it can be seen that the air quality remains very stable. In figures just released on the IQAir website, the average reading in 2020 was 8.1 µg/m³ which was within the target suggested by the World Health Organisation (WHO). For 11 months of the year, the target figure was achieved, only in December was it exceeded by a half-point. (10.5 µg/m³) which is still classed as being “Good”. Over the previous three years, the numbers have not significantly changed with 7.2 µg/m³, 8.1 µg/m³ and 8.5 µg/m³ respectively.

How is the air quality in Wisconsin measured?

Following the introduction of the Clean Air Act, many states were tasked with monitoring their air quality and putting in annual reports so it could be recorded. In Wisconsin, there are 30 ozone (O3) monitoring stations and 19 Particulate Matter (PM2.5) measuring stations. Additionally, the Department of Natural Resources (DNR) measures sulphur dioxide (SO2), nitrogen oxide (NO) and carbon monoxide (CO).

Data from Wisconsin’s monitoring network is validated and reported to the EPA to determine just how well air pollution controls and programs are working to improve air quality and meet the stated federal standards. In addition, by using continuous monitoring data, the DNR quickly informs the public when air pollution reaches unhealthy levels.

In 2016, the American Lung Association ranked Sheboygan, WI as the 22nd most ozone polluted city in the entire country.

What are the sources of air pollution in Wisconsin?

There are four main sources of air pollution which can be broken down further. There are mobile sources such as cars, buses, aeroplanes, trucks, and trains. There are stationary sources such as power plants, oil refineries, industrial facilities and factories. Natural sources can be wind-blown dust, wildfires and volcanoes, as well as some pollution producing sites, for example from agricultural areas, cities, and wood-burning appliances.

Mobile sources account for more than 50 per cent of all the air pollution in the US and the primary mobile source is the automobile. Stationary sources, such as power plants, emit large amounts of pollution from a single location, these are also known as point sources of pollution.

Carbon monoxide (CO) is a colourless, odourless and tasteless gas. It is caused by automobile emissions, with high levels possible near large parking areas, traffic jams or congested city streets where large numbers of slow-moving cars accumulate around junctions and intersections. The accepted level is generally regarded as being 35 ppm (parts per million) and nearly all areas of Wisconsin are below this level.

Can the quality of air in Wisconsin be improved?

Wisconsin's air quality is slowly improving. The Wisconsin Department of Natural Resources (DNR) 2020 Air Quality Trends Report has been published and confirms decreasing concentrations of most pollutants across the state.

The report, which includes air quality data through 2019, finds that concentrations of most pollutants for which the Environmental Protection Agency (EPA) has set national air quality standards have decreased in all regions of the state since monitoring began. Due in part to these significant reductions, 95 per cent of Wisconsin's population lives in areas meeting all federal air quality standards.

The shoreline along Lake Michigan has historically been an area of high ozone pollution, however, this has gradually been decreasing and it is now almost 25 per cent lower than it was 20 years ago. Among other reductions recorded were an 89 per cent drop in sulphur dioxide and a 60 per cent reduction in carbon monoxide emissions. All of these reductions have been attributed to a more fuel-efficient system of using fossil fuels and more efficient engines in road vehicles.

What can be done to lessen the risk of poor air quality in Wisconsin?

The fewer vehicles are used for travel, the better it will be for the local environment. Consider using or starting a carpool system with colleagues at work. Try to adapt to public transport if and when possible. Cycling or walking are other possibilities and most cities now have networks of safe tracks and paths for this very reason.

Air pollution is a serious problem in northeast Wisconsin. This region suffers from a multitude of air emissions sources, some locally produced and others that cross over from southeast Wisconsin and northern Illinois.

The major source of air pollution is from vehicle traffic. Cars and trucks release a wide variety of toxic gases and particulates, and because we have so many of them, their combined health effects are high. Even the abrasion of their tyres on the road surfaces and the action of brake discs/drums cause tiny amounts of PM2.5 to enter the atmosphere. This region is particularly impacted due to the large number of diesel trucks serving major manufacturers. Diesel engines create more pollution than gasoline engines and seem to have escaped many of the clean air regulations imposed on gasoline-powered cars. The vehicle pollution is compounded by the rapid urban growth and sprawl in northeast Wisconsin. More people are driving further.

Vehicle emissions include carbon dioxide (CO2), carbon monoxide (CO), nitrous oxides (NOx), polyaromatic hydrocarbons (PAHs), particulates (PM2.5 and PM10) and other combustion by-products. Escaped gasoline vapours also contain a variety of petroleum pollutants.

Coal-fired power plants and large manufacturing businesses are two other major contributors to local air pollution. Coal burning is particularly dirty by releasing sulphur dioxide, carbon dioxide, carbon monoxide, nitrous oxides, PAHs, mercury, arsenic, particulates, and many other toxic substances. In 2012, Wisconsin utilities agreed to spend more than $1 billion to clean up ageing coal-fired power plants under a settlement with the US. Environmental Protection Agency. The industrial Fox River Valley (including the Green Bay area) is a significant regional air pollution source.

What else can be done to reduce air pollution in Wisconsin?

One way of reducing car journeys is to travel to local shops on foot or cycle there. Try to buy enough provisions for a month and use local shops to top up on things you run out of.

Walking or cycling to school is a good way to start the day and it is proven that active children grow into active adults and are often healthier because of it.

For the daily commute, try to leave the car at home for one day each week and choose alternative ways of getting there. Try the Park and Ride facilities which can be surprisingly convenient and might even save time on the journey. Public transport reduces congestion on the city streets as well as reducing our individual carbon dioxide emissions. CO2 emissions per passenger for train and coach are, on average, six to eight times lower than car travel.

If you’re often travelling to a similar location, such as work or school, as someone else locally it’s worth considering car sharing or carpooling. Schemes such as these are often organised by companies on behalf of their staff. Carpooling ultimately takes at least one vehicle off the road and can lead to saving on fuel.

Consider planting greenery around your locality, either in public places or your own garden. It is a well-known fact that plants clean the air around them by absorbing carbon dioxide.

When the time is appropriate to change your car, consider getting one of the newer models such as a hybrid or an electric vehicle. Many local governments offer incentives when buying such vehicles and often continue to offer incentives during their daily use.

“Green” cars are often exempt from congestion charges and are often allowed to drive through areas of the city that gas-powered cars are not permitted.

Burning solid fuels, such as in open fires and wood-burning stoves have a significant impact on air pollution. They produce a considerable amount of particulate matter very close to home. Avoid burning leaves and rubbish in your garden too. In some areas of the city, this practice is banned as it is a smoke-free zone.

Is Wisconsin adopting stricter air pollution standards?

Parts of Wisconsin have some of the cleanest air in the country. The same report says the Eau Claire/Menomonie and La Crosse/Onalaska areas both had zero "high pollution" days over a three-year period.

And Ashland, Forest, and Taylor counties also had perfect scores.

Ozone is a toxic gas that is not emitted from vehicle exhausts or factory chimneys. But those kinds of emissions in the atmosphere, when combined with sunlight and heat, form ozone. It often appears downwind from those emission sources, responsible for the smog that is often seen above big cities.

Particle pollution, on the other hand, has a different source. Actually, an entire range of sources from road dust, forest fires, wood burning and power plants or industry.

Those particles which are smaller than a human hair can get into the lungs and cause health problems.

Wisconsin air quality data attribution

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Which is the most polluted city in Wisconsin?


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