Can Pesticides Linger After Application?

Dec 10, 2018

Pesticides are chemicals that are used to kill different types of organisms including fungi, bacteria, and insects.  These chemicals are typically sprayed onto fields or in homes where pests may be lurking. When using pesticides, we often only think about it’s intended effect which is to eliminate the pest.  However, we rarely consider the effects on air quality after pesticides are sprayed. In this blog post, I will provide some information on pesticides and testing for these chemicals.

Pesticide Testing 

Testing for pesticides in the air after the chemical has been applied can be tricky because typically these chemicals are semi- or non-volatile compounds.  Semi-volatile compounds have a low vapor pressure and therefore they have a slow rate of evaporation and may spend most of the time in a condensed state on surfaces (not in the air).  However, semi-volatile pesticides can become airborne again if they heat up, which can happen on a hot day or if direct sunlight hits the area with pesticides. The heat causes the pesticide molecules to travel faster and increases the chances of some molecules escaping into the air.

If you want to know if pesticides are present, taking an air sample for non-volatile pesticides may not be the best way to test.  An air sample may show that there are no pesticides in the air but there could still be some residual pesticide chemicals that are condensed on surfaces in the environment.

Pesticides in Dust

Sometimes these chemicals condense on house dust.  Collecting a dust sample from the environment and getting the sample analyzed for pesticides may provide a better picture of pesticides that were applied in the past.  A dust sample can show if pesticides such as permethrin and chlordane are present. Settled pesticides in dust can be potentially hazardous because they can become airborne along with the dust.   2,4-D is an herbicide commonly used to kill weeds along roadsides, in forests, and on corn and soybean crops in North America. This particular herbicide is commonly found in dust inside of homes .  These chemicals used in the outdoor environment can be tracked into homes on the bottom of a person’s shoes, on their clothes, or through air infiltration.


Pesticides are commonly used in outdoor and indoor environments.  The best way to avoid the accumulation of pesticides indoors is to minimize the use of pesticides whenever possible, and opt for more natural approaches such as “integrated pest management”. If pesticides are to be used, it should be done in a well-ventilated area, and follow the manufacturer’s directions.  The EPA website provides more helpful tips on reducing pesticide exposure. If you are concerned that your home may have high levels of pesticides, Indoor Science offers a dust test that includes an analysis of several types of pesticides including carbamates, organochlorines, and pyrethroids.