News Flash

Air Quality

Posted on: September 8, 2021


ragweed electron microscope

Ragweed can be found in the eastern and midwestern United States. In Southwest Ohio, ragweed season begins in late August and can prevail into early October. 

Ragweed grains – like most pollens – are released in the morning, peaking at midday. A ragweed grain is 20 to 25 micrometers in diameter. To give you perspective, a human hair has a diameter of approximately 50 – 70 micrometers. 

How do you know how much ragweed is in our local air? We at the Southwest Ohio Air Quality Agency provide pollen counts as a public service. Each morning, Monday through Friday, our technician retrieves the 24-hour collection from our rooftop “Rotorod.” The technician uses a pink dye to make pollen grains visible under the microscope. The technician, using a grid and mathematics, identifies and counts the different pollen grains.  The technician uses a specific calculation to account for how long the collection period was. After completing the day’s count, the information is posted on our website,

How can you survive ragweed season?

  • Avoid peak ragweed hours of 10 a.m. to 3 p.m.
  • Keep windows closed at home and in the car.
  • Change clothes and wash hands after you’ve been outside. Pollen can cling to clothing. 
  • And, consult with your health care provider for medical advice to manager your symptoms.


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