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August 26, 2020

Ozone reaches dangerous levels

Air pollution threatens the health of Boulder County residents

Boulder County, CO - Extraordinarily high levels of ground-level ozone were recorded in Boulder County this week. The combination of hot temperatures, wildfire smoke, and air pollution have created environmental conditions that threaten the health of Boulder County residents.

Air quality monitoring stations in Longmont and at the Boulder Reservoir recorded dangerous spikes in ground-level ozone on August 25, with the highest measurements, taken from 5 minute averages, reporting 102 parts per billion shortly after 1 pm in Boulder and over 115 parts per billion around the same time in Longmont. The federal health standard is 70 parts per billion. The highest 8-hour ozone average concentration on August 25 was 79 parts per billion at the monitoring site in Boulder. Ozone has often been in the "unhealthy for sensitive groups" to generally "unhealthy" categories this summer, with over 40 ozone action days issued for the Front Range. Recognizing this potential health threat, local governments in Boulder County have engaged air researcher Dr. Detlev Helmig to monitor multiple pollutants at five sites. This data can be viewed in real-time at

These high ozone levels are due to a number of human influences on the environment that have converged in the last few weeks,” said Collin Tomb, Air Quality Team Lead at Boulder County Public Health. A mixture of air pollution from the use of fossil fuels during activities such as driving, heating and cooling, electricity generation, and manufacturing — in addition to emissions from oil and gas production contribute to the high ozone levels we’re seeing now.

While driving declined in the early days of the coronavirus pandemic, traffic is returning to normal levels. Oil and gas production is nearly as active as at this time in 2019.

These human activities contribute to ground-level ozone and also fuel climate change, which in turn increases the length and severity of wildfire season in the Western United States. Wildfire smoke contributes to ozone and increases particulate matter in the air. The combination of fine particulates in smoke with lung-burning ozone can be harmful to everyone, but it is particularly damaging for seniors, children, and those with heart and lung conditions – many of the same people who are at added risk from COVID-19.

"The bottom line is that these are dangerously high levels of ozone,” said Cindy Copeland, Air Quality Specialist at Boulder County Public Health. “These high levels are continuing and they are only partially due to smoke. Because of climate change, wildfires are becoming more part and parcel of daily life in Colorado during the summer and shouldn’t be discounted as exceptional events. Emissions from the sources that we can control need to be reduced even further so we don’t continue to have such unhealthy conditions during the summer months when people both need to work outside and want to enjoy the outdoors.

The public is advised to monitor air quality conditions in their area and avoid prolonged exertion outdoors when air quality is poor. Air quality conditions can be monitored at

Individuals can take action to reduce ozone emissions and the impacts of climate change by reducing driving, combining car trips, switching to electric lawn equipment, and filling up on gasoline after 5pm. Learn more by visiting

Anyone concerned about the impacts of ozone pollution on health or the climate can make their voices heard at upcoming virtual public hearings of the Colorado Air Quality Control Commission. A public hearing on ozone and hydrocarbons from oil and gas will be held September 17 and a meeting of the Greenhouse Gas (GHG) Strategy Subcommittee will be held September 25. Public comments can be sent to by following submittal instructions on the Air Quality Control Commission web page to have those comments applied to a specific issue.

For more information about air quality and public health or Boulder County’s sustainability mission, visit or contact Christian Herrmann at