U.S. EPA monitored outdoor air near the Sterigenics facility to better understand the levels of ethylene oxide (EtO) in the air. The first monitors began collecting air samples on Nov. 13, 2018.  Read the Quality Assurance Project Plan for Field Sampling Plan for Ambient Air Ethylene Oxide Monitoring near Sterigenics Facility, Willowbrook, IL

Air samples were collected every three days, over a 24-hour time frame, for three full months.

See the full available data set below or review the data by monitoring date with general wind direction and speed for each sampling period.

• Full Data Table: Ethylene Oxide Concentrations in Outdoor Air - 24-hour averages (PDF)(1 pg, 66 K)
  (updated 4/25)
• Ethylene Oxide Ambient Sampling Plan for Sterigenics (Willowbrook, IL) (PDF)(5 pp, 2 MB, Oct. 26, 2018)
• How to Read a Wind Rose (PDF)(1 pg, 111 K)
• November 2018: Ethylene Oxide Concentrations in Outdoor Air - 24-hour averages (PDF)(6 pp, 591 K)
• December 2018: Ethylene Oxide Concentrations in Outdoor Air - 24-hour averages (PDF)(10 pp, 673 K)
• January 2019: Ethylene Oxide Concentrations in Outdoor Air - 24-hour averages (PDF)(10 pp, 673 K)
• February 2019: Ethylene Oxide Concentrations in Outdoor Air - 24-hour averages (PDF)(12 pp, 714 K)
  (updated 3/21)
• March 2019: Ethylene Oxide Concentrations in Outdoor Air - 24-hour averages (PDF)(11 pp, 692 K)
  (updated 4/25)