How does ozone pollution in San Juan County compare with neighboring counties?

Hannah Grover
Farmington Daily Times
Bluffs are pictured, Monday, April 29, 2019, from Lions Wilderness Park in Farmington. San Juan County received a "D" grade from the American Lung Association for ozone pollution.
  • Ozone pollution peaked in San Juan County in 2005 to 2007.
  • Ozone increases risk of asthma, strokes, heart attacks and congestive heart failure.
  • The American Lung Association has graded counties for air quality over the past 20 years.

FARMINGTON — The American Lung Association gave San Juan County a “D” grade for ozone pollution in the State of the Air report released this month.

The report analyzed ozone and particle pollution in each county from 2015 through 2017 and gave the counties a grade based on the number of days the air pollution exceeded standards.

According to the report, San Juan County had nine days that exceeded standards for ozone pollution during those three years, or an average of three high ozone days a year.

Counties that have an average of 2.1 to 3.2 days exceeding standards each year are given a “D” grade.

How does this year's grade compare to previous years?

The county dropped a letter grade in this year’s report. Last year’s report analyzed the years 2014 through 2016. During that time, there were less than two days of high ozone on average each year. The 2014 through 2016 time period had some of the lowest ozone levels since the American Lung Association began releasing the State of the Air report 20 years ago.

Ozone pollution in San Juan County peaked during the 2005 to 2007 time frame with an average of 23.8 days exceeding federal standards each year.

While previous reports have ranked Farmington’s air as the cleanest in the country in terms of particle matter, there was not enough data to grade San Juan County for particle pollution between 2015 and 2017.

What is ozone?

Ozone is created when nitrogen oxide (NOx) and volatile organic compounds react with sunlight. The primary source of NOx and VOCs is the burning of fossil fuels such as oil, natural gas and coal.

An EPA website reported that regional ozone levels were low Monday when high school athletes competed during Monday's Piedra Vista Invitational at Piñon Hills Golf Course in Farmington. Aztec's Isabelle Peralta swings at her ball on the first-hole tee box.  Check if planning outdoor activities during times when air quality is poor.

According to the report, ozone pollution has been increasing nationwide partially due to climate change. Warm weather makes it more likely for ozone to form. 

American Lung Association Director of Advocacy JoAnna Strother said 2015 through 2017 were the warmest years on record according to the National Oceanic and Atmospheric Administration.

Exposure to ozone can irritate lungs and long-term exposure has been linked to premature death. According to the American Lung Association, children exposed to ozone pollution are more likely to develop asthma. The American Lung Association states ozone pollution also increases the likelihood of strokes, heart attacks and congestive heart failure.

Strother said people should minimize the time they spend outside on high ozone days. The Environmental Protection Agency's air quality website,, can be used to monitor air quality.

How did neighboring counties score?

La Plata County, Colorado: The county scored an “F” for ozone pollution in the State of the Air report. Between 2015 and 2017, La Plata County had 13 days exceeding standards for ozone pollution, or 4.3 days each year. However, La Plata County received an “A” for particle pollution.

While San Juan County has seen declines in ozone pollution in the past 20 years, La Plata County has seen increased days of high ozone pollution. Between 2000 and 2004, La Plata County averaged zero days each year exceeding standards.

La Plata County registered its highest number of days exceeding ozone standards in the 2009 to 2011 time frame when it had an average of 7.3 high ozone days each year.

Montezuma County, Colorado: The southwest corner of Colorado scored a “B” for ozone pollution.

Between 2015 and 2017, Montezuma County had one day that exceeded ozone standards, or an average of 0.3 days each year. This is a slight increase from the 2014 to 2016 time period, when the county did not have any days exceeding ozone standards.

Montezuma County’s ozone pollution peaked in the 2005 to 2007 time period when it had an average of 6.7 days exceeding ozone standards each year.

San Juan County, Utah: Southeast Utah scored a “B” for ozone pollution for the third consecutive year. This is the best grade San Juan County has received.

During the 2015 to 2017 time period, San Juan County had one day that exceeded ozone standards. Ozone pollution peaked in San Juan County in the 1998 to 2000 time frame when it had an average of 6.3 days exceeding ozone standards each year.

Rio Arriba County: The State of the Air Report gave Rio Arriba County a “C” for ozone pollution.

Data for ozone levels in Rio Arriba County became available in 2013. The 2015-2017 time frame has the worst ozone pollution since 2013. There were three days exceeding standards during that time frame, or an average of one day each year. There were no days exceeding standards between 2014 and 2016.

Sandoval County: After seven consecutive years of scoring an “A” for ozone pollution, Sandoval County has dropped to a “B” after having a single day exceeding standards between 2015 and 2017.

Sandoval County’s ozone pollution peaked in the 2002 to 2004 time frame when it had an average of 14.7 days each year exceeding standards.

Apache and McKinley counties: Apache County, Arizona and McKinley County did not have enough ozone data available.

How can ozone levels be reduced?

Strother said reducing emissions will help clean up the air. She said the American Lung Association is calling for Congress to adopt science-based policies that will reduce emissions.

On an individual level, Strother said driving less, or even refueling vehicles at night, can reduce ozone pollution.

"We can all make a difference," she said.

Hannah Grover covers government for The Daily Times. She can be reached at 505-564-4652 or via email at