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Student scientists pinpoint problems with pesticide

Lauren McDougald and Amanda Clark show off their research on chloropicrin, a widely used pesticide, at the Western Spectroscopy Association Conference on Jan. 20 in Pacific Grove, CA. (Doug Wade)

Two Mills undergraduate chemists shared their research results with grad students and post-docs at the Western Spectroscopy Association Conference on Jan. 20. in Pacific Grove, CA.

Junior Lauren McDougald and sophomore Amanda Clark spent their summer studying chloropicrin for Dr. Elisabeth Wade, the project’s lead scientist and Mills College’s chemistry department head.

First employed in chemical warfare, chloropicrin is now used as a fumigant—or pesticide—for many California crops, such as strawberries, which tend to develop parasitic worms.

“If you ever grow strawberries in your backyard, you see the effect,” Wade said, referring to the parasites. “The first year, the strawberries are very big. Then every year after that, they get smaller and smaller and smaller.”

Farmers spray strawberry fields with chloropicrin before anything is planted, sterilizing the soil.

“It just kills everything,” McDougald said of the pesticide.

Wade and her research assistants wanted to know what happens chemically when the liquid form of chloropicrin evaporates into the air.

“One of the scary things about chloropicrin is it hasn’t had this kind of research done on it,” Clark said.

Farmers haven’t always used chloropicrin as a pesticide.

“We’ve replaced a fumigant that was bad with something that we don’t know is better or worse,” Clark said.

That first “bad” fumigant was methyl bromide, which has been banned because it hurts the ozone layer, according to Clark.

Chloropicrin works well as a fumigant because it’s a good warning agent against overexposure to the pesticide. Not only does chloropicrin give off tell-tale fumes, but farmers know they’re reacting to the pesticide when they tear-up or vomit, according to McDougald.

“It’s kind of safer for the farm workers,” Clark said, “but is it better for the environment?”

The research showed that when chloropicrin is exposed to sunlight it forms two other chemical compounds, phosgene (also once used as a chemical weapon and which has potential affects on the ozone layer) and nitrosyl chloride (a highly toxic compound).

This was expected, McDougald said. But when oxygen was added to the mix in order to imitate a farm’s actual atmosphere, smog contributors (NO2 and N2O2) showed up, too.

“We just get even more dangerous chemicals from a dangerous chemical,” McDougald said.

After collecting and analyzing the data for Wade, McDougald and Clark shared their results at a talk last fall, which was open to the Mills community. They then turned their talk into a poster, which they presented at the spectroscopy conference in Asilomar this January.

It was a first-time experience for both, and they were one of the few undergraduates there. The vast majority of attendees were grad students and post-docs.

“At first I was so intimidated to go there and have to talk to these people,” McDougald said, “but then I talked to them and they’re just normal people. Just like me.”

Clark said she felt something similar.

“There were times when I thought, ‘Okay, too much science. I’m not quite sure what they’re saying anymore,’” she said. “But then I’d look over to the grad students and I could tell there were points when they were saying, ‘Okay, I’m not sure what the speaker’s talking about either.’”

But meeting grad students at the conference allowed Clark to imagine what it would be like if she continued on in physical chemistry.

“There were a lot of lasers,” Clark said, laughing. “I got lost in a lot of the laser talk, to be honest. It showed me that there’s a lot more to learn.”

McDougald said it felt good to be a Mills woman at the conference.

“I remember this one chemist from Berkeley,” she said. “He was like, ‘Oh, Mills has a chem. department? I didn’t know that.’ And I was like, ‘Grrr,’” McDougald laughed. “It was nice to be there and show people that, oh yeah, Mills, this little bitty college, it does have a chem. department that actually does stuff.”

And that chem. department has its undergraduates out of the classroom and doing stuff early.

“A couple of my friends back home were surprised that I already had an internship (with Wade) just after freshman year,” Clark said. “I get that exposure early on, instead of reaching senior year and going, ‘Oh my God, I have to apply to grad school. Do I actually want to do this?’”

Clark, just a sophomore at Mills and with an internship and conference under her belt, said she definitely wants to study chemistry further.

Lab partner McDougald didn’t always feel the same way.

Over winter break, McDougald came back to work for Wade without Clark.

“I was pretty much the only person in this one little dark room, doing my little trials. It was so depressing. I was all alone all day in the Natural Science Building. I got to the point where I was like, ‘Screw this research. It doesn’t even matter. Nobody’s going to care.’”

But many people at the conference cared.

“This one guy I met there,” McDougald said, “he was just so thankful that we were looking at the fumigant. He was like, ‘When are you going to publish? When are you going to show this to people? This needs to get out there.’”

“It made me feel like what we were doing is a lot more important. It made me just want to get back to doing work.”

Farm workers harvest strawberries in Salinas, CA. Chloropicrin is often used as a pre-plant fumigant for many California crops. (Courtesy of Wiki Commons)