Jacqueline Barkoski: Exploring Associations Between Horse Care Pesticides and Autism

Photo: Kathleen Navarro and Jacquelin Barkoski
Kathleen Navarro and Jacquelin Barkoski. Photography by Berkeley Event Photographer Genevieve Shiffrar.

Horse owners do not mind getting their hands dirty. Take grooming, for instance. Brushing the horse’s coat and spraying it with fly repellent are part of the routine. Sometimes, horse owners apply the pesticide by hand, first spraying it on their own skin before wiping it on the animal. Soon, however, we will know if caring for a horse has unintentional consequences thanks to research by Jacqueline Barkoski and her colleagues from UC Davis.

Barkoski, a doctoral student in the UC Davis Graduate Group in Epidemiology, and her academic supervisor, Irva Hertz-Picciotto, are investigating the health effects of pesticides like fly repellent, particularly pyrethroid and pyrethrin-based products, which are widely used in the horse industry. These products have been linked to neurotoxicological effects in human and animal studies. They question whether a woman’s exposure to these pesticides during the first trimester of pregnancy may be related to developmental outcomes of the child, including autism.

COEH faculty Irva Hertz-Picciotto is the principal investigator and director of the UC Davis Center for Childhood Autism Risks from Genetics and the Environment, or CHARGE. Launched in 2003, CHARGE is the first comprehensive study of environmental causes and risk factors for autism and developmental delay.

“There is evidence to show the perinatal period is a critical window of exposure for the development of autism,” says Barkoski. “Specifically, in the first trimester when the neural tube is forming, it is believed that exposures during this time can have an impact on the neurodevelopmental system of the child. It contributes to the rationale for looking at mothers who use pyrethroid and pyrethrin-based products while they are pregnant.”

The horse industry is a $4.1 billion dollar business in California, reports Barkoski. There are roughly 50,000 horse owners in the State and the majority of them are women.

Coincidentally, a couple of years ago, some parents contacted the CHARGE study to ask researchers, “I and my friends all ride horses and our kids have autism – do you think there is anything going on?”

“There are so many chance events, and you can’t assume just from their questions that something related to their horse riding is causing autism,” says Barkoski. “But pyrethroid and pyrethrin-based products are used in a variety of horse care products, including coat conditioners and sun screens. They also come in different forms such as sprays, wipes, and concentrates. And no one has looked at what exposures humans are receiving as well as animals.”

Barkoski first developed a pilot survey and interviewed horse owners in Davis, California, to learn about the industry, and to find out how and when the products are used. Building on her pilot, she plans to distribute the survey to a study population of 36,000 women. She is also collecting product information so she can identify pesticide concentrations using U.S. Environmental Protection Agency databases.

“I’m working with PhD student Kathleen Navarro at UC Berkeley to build an exploratory exposure assessment,” adds Barkoski. COEH faculty John Balmes and Katherine Hammond from the Division of Environmental Health Sciences are her advisors.

Barkoski completed her master’s degree in Public Health from the University of Michigan in April 2012. Her thesis examined a longitudinal birth cohort in Mexico City to investigate links between prenatal lead exposure and autism-like behaviors. She has a background in exposure science, toxicology, and epidemiology.

While a student in Michigan, Barkoski gained insight into autism spectrum disorder by working with families at a local autism center. “It’s hard to find a baby sitter for a child with special needs,” explains Barkoski, “so we would host “Kids Night In” events where parents could drop-off their children. It helped me to realize autism is truly on a spectrum and each child is different.”

Most products used in the home to eliminate pests such as cockroaches and ants contain pyrethroids and/or pyrethrins, notes Barkoski. She hopes her study will lead to a convincing rationale to further examine pyrethroid exposures during pregnancy to determine their influence on autism and other neurodevelopmental disorders.

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