State health department investigating an elevated benzene measurement

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(REMOTE, Dec. 15, 2021) The Colorado Air Monitoring Mobile Lab measured a level of benzene slightly above the health guideline value during community monitoring of oil and gas activity in Weld County last week. The measurement does not reflect an immediate health risk to nearby residents but indicates a need for further investigation. CDPHE will conduct an investigation with the assistance of the Colorado Oil and Gas Conservation Commission.


The Colorado Air Monitoring Mobile Lab is part of a suite of community air monitoring programs at CDPHE. This includes the department’s new mobile monitoring van, the Mobile Oil/gas Optical Sensor of Emissions (MOOSE), which has advanced emissions tracking capabilities; as well as aerial survey flights to locate and measure emissions from oil and gas operations; and a range of stationary monitors the department can deploy when needed.


“We are committed to problem solving, working with local governments, and ensuring Colorado communities are clean, safe and healthy,” said Shaun McGrath, Director of Environmental Health and Protection at the Colorado Department of Public Health and Environment. “Under the leadership of Director Jill Hunsaker Ryan and the Polis Administration, we’ve been able to expand community air monitoring and response, and we’re pleased to do so. With increased monitoring capability, we are better able to find sources of pollution, investigate, and then take actions where possible.”

The mobile lab measured a benzene level of 9.9 parts per billion (ppb) in a community north of Union Reservoir on Dec. 11 and confirmed the results Dec. 13. The federal Agency for Toxic Substances and Disease Registry’s (ATSDR) short-term health-based guideline is 9 ppb. Health-based guidelines help identify areas, contaminants, and conditions that require further attention. They are set much lower than the levels at which people would typically experience negative health impacts. 

The state public health and environment department sent the mobile lab to the community to gather more information about emissions near Cub Creek Energy’s Knight operation in Weld County. The mobile lab was parked approximately 600 feet from the operation when it collected the 9.9 ppb measurement, but there is not enough information to determine the exact source or sources of the elevated benzene level. This elevated level is the only one that has occurred during more than 400 hours of monitoring at this site so far.

The state will:

  • Inspect the Cub Creek Energy Knight operation and evaluate other potential sources nearby.

  • Continue to measure benzene and other volatile organic compounds at this site.

  • Determine whether elevated benzene levels are occurring more frequently and notify the public accordingly.

  • Analyze all the data collected during the elevated measurement.

Benzene is a volatile organic compound that is released into the air from many sources, including industries, vehicles, landscaping tools, cigarette smoke, and household products. People are exposed to low levels of benzene every day. Whether the chemical will cause health impacts depends on how much is in the air and how long and how often people breathe it in. Exposure to benzene at levels higher than those measured in this event can cause short-term health impacts such as headaches, skin and eye irritation, and respiratory issues. 

People who are experiencing serious or persistent symptoms that may be related to benzene should contact a health care provider. People who have health concerns about oil and gas operations or who have questions about this measurement can contact the Oil and Gas Health Information and Response Program at 303-389-1687 or