On top of that, she just received the prestigious, and highly competitive, STAR fellowship to support her research for the doctoral dissertation. She is investigating the relationship between dietary exposure to pesticides and neurocognitive health.
The three-year fellowship program, sponsored by the Environmental Protection Agency (EPA), supports masters and doctoral degree candidates in environmental studies by covering tuition fees and other expenses and providing a yearly stipend, up to $37,000 per year of support. Curls current project blends earlier research she did while studying for a masters degree in the department and while working for three years after graduation with Dr. Richard Fenske, professor of environmental and occupational health sciences.
An epidemiological cohort is the foundation of the center where Curl works, the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) directed by Dr. Joel Kaufman, professor of environmental and occupational health sciences, epidemiology, and medicine. The study involves more than 6,000 men and women from six communities in the United States. The participants are from diverse racial and ethnic groups.
While the Multi-Ethnic Study of Atherosclerosis (MESA) broadly investigates the early stages of atherosclerosis, MESA Air specifically examines the relationship between exposure to air pollution and progression of the very early stages of heart and blood vessel disease.
Curls research is unusual for a doctoral candidate in environmental and occupational health sciences because she is bridging her background and interest in exposure sciences with epidemiology, toxicology, and environmental medicine. She has an advantage because she has studied and worked with department faculty since 1998, with a hiatus of seven years when she worked for both a nonprofit in Connecticut and an environmental consulting firm in Colorado and then in Seattle.
In her earlier research for her masters thesis in 2000, Curl investigated levels of pesticide exposure in children whose families worked in agriculture. Then, in follow-up work after graduation, she and Fenske examined the differences in pesticide exposure between suburban Seattle kids, children of farmworkers in Eastern Washington, and children who had a parent working as a pesticide applicator.
The results surprised them. They expected the children who lived in Seattle to have the least exposure, which they measured using levels of pesticide metabolites in urine samples. Although exposures were higher in farmworkers children during periods of active crop-spraying, in non-spray periods, exposures for Seattle kids were actually higher than the kids in Eastern Washington.
Pesticides are regularly applied to orchards. Studies led by Fenske, who directs the Pacific Northwest Agricultural Safety and Health Center, demonstrated that in agricultural families, there were significant associations between pesticide levels in house and vehicle dust, and between pesticide metabolite levels in farmworkers and their children. This supports the idea of a “take-home” exposure pathway – that farmworkers bring pesticides home with them on their clothes and shoes.
So what explained the higher levels of exposure in Seattle kids?
“We puzzled about that and then we looked at income and reported dietary patterns. We found that the kids living in Eastern Washington were poorer and werent eating a lot of fruits and vegetables. The pesticides that we were looking for—organaphosphates—are used on fruits and vegetables,” explained Curl. “The more affluent kids in Seattle might be getting more dietary exposure. At certain times of year, diet could be an even more important route of exposure than having a parent that works in agriculture.”
They tested the theory by comparing metabolite levels of 40 two- to five-year-olds whose parents reported that they ate either primarily organic or primarily conventionally grown food. They found the children who ate conventional food were exposed to more pesticides.
“We thought there might be a measurable difference,” said Curl, “but there was a ten-fold difference in levels. That surprised us.” The study attracted a great deal of media attention. Everyone wanted to know if feeding kids organic versus conventionally grown produce had any effect on childrens health.
In 2003, Curl was quoted in The New York Times, saying “We don’t know. Nobody does.” “Ever since then it has really plagued me,” Curls said, “Its been a thing in the back of my head all of these years. We can show that the exposure is different, but we dont really know what this means in terms of health effects.”
Now she intends to find out. She is currently examining the relationship between dietary pesticide exposure and neurocognitive outcomes. Previous studies have associated low-level pesticide exposure with neurocognitive changes in farmworkers and in children living in farming communities.
Curl will be using data already being gathered by the MESA study, whose participants fill out a 20-page food frequency questionnaire every two years to provide detailed information about their diets. Curl intends to add some questions that specifically ask about the individuals organic fruit and vegetable consumption. These individuals also give urine samples and take neurocognitive tests.
She will calculate dietary exposure to pesticide by comparing the individuals record of fruit and vegetable consumption to the U.S. Department of Agricultures data for pesticide application to these foods, and scaling the individuals exposure by how much of their consumption was organic. Curl will verify the individuals exposure assessment using the urine samples, although she admits that the urine samples are imperfect.
“Whats in the urine is only a representation of what you ate for the past two days,” Curl explains. Organophosphorus pesticides, which is the predominate type of pesticide used in the Unites States, are processed quickly through the body and excreted within about 48 hours. “But you do tend to eat the same kinds of things,” she adds.
She plans to pair dietary pesticide exposure to the individuals cognitive health, which is assessed by a series of neurocognitive tests completed by each person in the MESA cohort. She hypothesizes that people who have higher levels of pesticides in their diet will perform more poorly on the neurocognitive tests.