Types of Drift


Crop duster

Pesticide drift is all too common in places where agricultural and residential areas intersect.

Even the most careful, responsible pesticide sprayer cannot control what happens to pesticide droplets once they are released from his plane or tractor. And when conditions are right, these droplets can end up settling on someone’s yard, on another farmer’s crops, or on the skin of someone who happens to be at the wrong place at the wrong time. This type of drift - when a pesticide application misses it’s target - is called spray drift and is what most people think about when they hear the phrase “pesticide drift.” It’s common, it’s dangerous, and it’s what existing regulations try to prevent.

95% - 98% of applied pesticides miss their target, reaching nearby people and wildlife, waterways, soil and air.Source: Miller GT (2004), Sustaining the Earth, 6th edition. Thompson Learning, Inc. Pacific Grove, California. Chapter 9, Pages 211-216.

Another kind of drift that’s also common and dangerous, but largely ignored is called volatilization drift. This type of drift happens when pesticides slowly evaporate into the air from out of the soil or off of a crop after application, and it can take place for several days following an application.

Fighting pesticide drift has been one of PAN’s main areas of focus for the last several years. The EPA's December 2009 recognition and investigation of volatilization drift is a direct result of our field work and advocacy.

Spray Drift

Spray drift is an ongoing problem wherever pesticides are used—in agriculture, in forestry, and even in homes and gardens. Sometimes the spray drift blows in from some distance away. Other times people are sprayed directly, like when a reckless applicator fails to turns off his sprayer when he reaches the edge of the field.

  • May 2009, outside of Fresno, CA :: Two elementary school children were sprayed with a mixture of 3 chemicals while waiting for the bus. “We thought the tractor wouldn’t get us, but it did,” explained 10-year-old Nancy Lada. “I told the bus driver that I wasn’t feeling good. Like, I was feeling sick. My head hurt, I wanted to throw up … I was itching.” This was 1 of 7 reported drift incidents involving school buses that year in the region.
  • 2009,  Imperial Valley, CA :: Macario Vargas is a 59-year-old farmworker who’s spent his whole life working in Imperial County. In 2009, a plane sprayed the field two fields away from where he was working; it was windy, and the pesticide drifted toward Vargas and his coworkers. He didn’t notice anything until that evening, when his upper body started to sting and itch. The next day, his skin was blistering and he was in pain. He eventually ended up in the hospital as his symptoms worsened to vomiting, extreme pain, headaches, blurred vision, and irritated eyes. Farmworkers are frequently the victims of spray drift when nearby fields are sprayed. Macario Vargas’s story is not unusual (PDF).

Spray drift doesn’t need to settle directly on people to do damage. Children can be exposed to pesticides when playing in a field or on a playground that has been previously drifted on. We thought the tractor wouldn’t get us, but it did...          My head hurt, I wanted to throw up. - Nancy Lada, 10-year-old drift victim And around the country, agricultural commissioners and state departments of agriculture routinely investigate cases of crop damage, in which a grower’s crops are harmed or even ruined because a crop duster sprayed the wrong field, or pesticide mist drifted in from a neighbor. Organic growers are particularly susceptible since any pesticide contamination can make their crop unsellable and jeopardize their certification.

KQED Reports on Pesticide Drift

DriftCatcher Part 1
QUEST on KQED Public Media.

DriftCatcher Part 2
QUEST on KQED Public Media.


Volatilization Drift

While less recognized than spray drift, volatilization drift is no less dangerous. Volatilization happens when a pesticide is applied to a field and then hours or even days later, the pesticide vaporizes from the surface of plants or out of the soil, and that invisible vapor cloud moves offsite.

Fumigant pesticides are particularly prone to this type of drift, as these chemicals are often gases or very volatile liquids, and they are applied at very high rates (typically hundreds of pounds per acre). The fact that most fumigant pesticides are also extraordinarily toxic makes this problem even worse. Scarcely a year goes by without an incident in which dozens or even hundreds of people are made ill when a volatilized pesticide cloud drifts out of fumigated field.

  • Yerington, NV, 2007 :: 150 farmworkers were sickened by a chloropicrin cloud that drifted in from a field 1/3 of mile away. The chemical - a severe irritant that was used as chemical warfare agent in World Wars I and II - had been applied the previous day, and transported to the workers area by volatilization.
  • Pescadero, CA, 2006 :: organic farmer Larry Jacobs lost $1 million in revenue, when the insecticides diazinon, chlorpyrifos, and dimethoate were detected in his sage, dill, and rosemary. The pesticides had been applied to nearby Brussels’ sprouts fields, and contaminated his crop via volatilization. In a landmark case, Larry successfully sued the applicator, Western Farm Services, for $1 million in damages.