Pollution Sources


The EPA currently recognizes three categories of pollution sources: Mobile Sources, Area Sources, and Point Sources. Each contribute to the poor air quality in Utah. Every year we learn more vital information that helps us to further clean our air. Take some time to educate yourself about pollution in Utah.

Pollution Sources

Types of Emission sources and their contribution to pollution in percentage. [21]

This chart is based on the Utah Department of Air Quality 2008 emissions inventory report for the four urbanized Wasatch Front counties combined: Davis, Salt Lake, Utah and Weber. These percentages represent averages from a typical winter weekday.

Emission source Mobile Sources Area Sources Point Sources
% of total emissions 57% 32% 11%
Examples Vehilces including cars, trucks, planes, lawnmowers, etc. Homes, small businesses, restaurants, aerosol products, etc. Mines, refineries,  large industry, etc.


In Utah, mobile sources are the primary contributor to our poor air quality, contributing 57% of the overall PM2.5. While mobile sources include things like lawnmowers and air traffic, the lion’s share of pollution comes from our cars and trucks. You can make a difference by using public transportation and carpooling. But, having a basic understanding of the technology present in your car can also help you to make informed decisions about your driving habits. [6]

Cold starts - Catalytic Converter

“Cold starts create the vast majority of vehicle pollution. When you start your vehicle, your catalytic converter is cold and it’s not working. It takes a few minutes of operation to warm up to the point that the catalytic converter is removing the emissions. It's that first couple of minutes when 60 percent of the emissions on a trip are created.” [7].

Chaining your trips together not only makes sense but it pollutes less. What you may not know is that your car's catalytic converter reduces your tailpipe emissions. In order for catalytic converters to run properly they need to be warm. The fewer times you start your car after the engine cools down, the better your catalytic converter works.

Catalytic Converters were first installed in cars in 1975 and have since become standard equipment. They filter the gas from the combustion in your engine before it leaves as exhaust. When the gas passes through a standard 3-way converter, nitrogen oxides, carbon monoxide and unburnt hydrocarbons are turned into nitrogen, carbon dioxide and water vapor. [8]

Vehicle Improvements

While cars emit less pollution than 40 years ago thanks to better technology and cleaner fuel, there are more cars on the road and we drive more miles on average. Therefore, cars and trucks are still a major source of pollution in Utah and worldwide. [9]

Vehicle Tiers - Tier III emission standards from the EPA

Recently, the Environmental Protection Agency has released a series of new regulations aimed at lowering the sulfur content of gasoline, while at the same time, raising the miles per gallon capability of most vehicles.  In the so-called Tier III standard, cars will be required to get 55 miles per gallon. Tier III will phase into Utah between 2017-2025, but some states like California have adopted the new standard in 2013. [10]

Area Sources - Homes & Buildings

The next largest contributor to poor air quality in Utah are Area Sources at 32%. These are places like your home, small businesses or small manufacturing companies.

Wood Burning in particular contributes an inordinate amount of pollution.

In 2013, Kerry Kelly and Dr. Robert Paine of the Program for Air Quality, Health and Society noted that homes heated with wood contribute 3,000 times more polluting than heating your home using natural gas.

Point Sources - Industrial

The remainder of the pollution (11%) we experience in Utah is formed in Point Sources. These include things like medical waste incinerators, large scale mines, and refineries. While these sources do contribute to our poor air, they are contained in specific areas and work with state and federal regulators to maintain acceptable levels of emissions.