Copyright
© 1999 The Seattle Times Company
Local News : Sunday, August 22, 1999
Pesticide
use and children's health: UW study aims to gauge the danger
by Warren
King
Seattle Times medical reporter
MALAGA, Chelan County - Behind the flat ridge, the deep-rose sunrise is turning pink as Mike Harrison prepares to try to eliminate the worry that has plagued him for months.
Many of his cherry trees have not weathered the cold, wet spring well. He's climbing into a disposable, white "moon suit" to protect himself from the mix of chemicals he is about to spray on his orchard.
"If they find a single fruit fly, even a dead one, in my shipment, I can't sell any cherries in California or even ship them through California," Harrison said earlier this summer as he worked 20 acres of cherry trees on his farm near Wenatchee.
Up the hill, Dr. Alex Liu, a University of Washington public-health researcher, helps two of his graduate students set up a laser device to measure how the cloud of pesticide drifts in the still, cool morning air. Soon the beams shoot across the hill and bounce back to produce spikes of light on a small field computer.
The two unlikely allies - farmer and researcher - are cooperating to gauge the double-edged sword of agriculture: pesticides.
Pesticides used on a huge variety of crops are under increasing scrutiny for their potential health effects, especially on children. Scientists are concerned about children's exposures through food and through the environment.
Earlier this month, the Environmental Protection Agency announced a stepped-up, 18-month schedule for completing its review of "organophosphates," a group of 39 older, widely used pesticides. Other common pesticides also are targeted for analysis.
The agency took action against two organophosphates. It banned the use of methyl parathion on most tree fruits, grapes and a variety of vegetables. And it cut back on the amount farmers can use of another pesticide, azinphos methyl, which is widely used in orchards.
The same concerns that prompted those actions are behind a $6.6 million project at the University of Washington. Now nearly a year under way, the program is attempting to fill a huge void of information on the effects of pesticide exposure in children. Most pesticide research has focused on adults, and as a result, health officials must resort to educated guesses when setting limits on children's exposure.
"We just don't know how much of a problem there is. This is part of an overall look nationally at children's health: Are we really being protective of children?" asks Dr. Elaine Faustman, UW professor of environmental health and director of the five-year project paid for by the EPA and the National Institute of Environmental Health Services.
Named the Children's Environmental Health Research Center, the project is one of eight funded in response to President Clinton's 1997 executive order that agencies consider children's health when issuing regulations. Six are unrelated to pesticides.
But another pesticide project at the University of California at Berkeley is focusing on the chemicals' effects on pregnant women and their unborn children.
At the UW, researchers are investigating ways in which children are exposed to pesticides, especially in farm settings, and the biochemical and molecular reasons children are more at risk.
They are looking at everything from dust samples taken from farm workers' homes to children's genetic susceptibility to pesticides. The research will add to the substantial data already amassed on children's exposure through food.
No one doubts that children are especially vulnerable to pesticides. During early childhood development, cells divide rapidly, making them more susceptible to harm from toxins. And kids, being kids, set themselves up for exposure even though they are not in the fields.
"They crawl in the dirt and on the carpet, where pesticide may be tracked in, the dog brings it in on his fur, and there is an amazing amount of hand-to-mouth activity," says Faustman.
Pesticide also drifts, despite the best efforts of orchardists like Harrison who spray only when there is little or no breeze.
Harrison drives his blue Ford tractor down the long lines of graceful cherry trees, pulling an Air Blast sprayer that looks like a jet engine. A gray, ghostlike plume of pesticide rises about four stories high in the morning sun, moves slowly to the west and gradually dissipates.
"This is beautiful. You can totally see this stuff," graduate student Ming Tsai says as he watches a line on the computer screen spike.
Rob Crampton, the other student, adjusts the laser beam, part of the LIDAR (light detection and ranging system) that measures distance by timing reflections off the plume to the millisecond.
On the edge of the orchard is an air pump, pulling air through a filter that later will be analyzed to determine pesticide concentrations in the area.
"We want to know if farmers' and workers' residences will be contaminated by drift, and we want to know to what degree," says Liu. "We believe that in this kind of environment . . . where the house is next to the orchard, that drift is the major source of exposure."
Harrison is convinced the way he sprays his orchard is safe for his family and his neighbors.
He is letting researchers use his land in the interest of science and to ensure that government pesticide restrictions are reasonable. He wants to make sure regulators don't assume farmers always use the maximum amount of pesticides allowable.
"It will just take time to figure out what all the research means," he says.
A UW study in 1995 found azinphos methyl in the house dust of 70 Wenatchee homes. Levels of the pesticide in the homes of agricultural workers were five times that of non-farm workers. Researchers have found that pesticides inside homes break down very slowly compared with residues broken down outside by rain and sun.
In another 1995 UW study in the Wenatchee area, researchers found that traces of azinphos methyl and methyl parathion were four times higher in the urine of agricultural workers' children than in other children. That study concluded that one-third of the farm children were exposed at levels deemed unacceptable by the EPA. The levels were cumulative, so no action was taken against growers for excessive single exposures.
"The biological levels were higher (in Wenatchee farm children) than what you would expect from only dust ingestion. So that suggests other sources and pathways of exposure . . . the pesticide drift and children's behavior," says Dr. Richard Fenske, UW professor of environmental health and head of the project's field-based studies.
The researchers also will enlist farm children to wear Global Positioning System (GPS) devices for several days around the time of spraying to track where they play. In the end, the tracking data, urine samples from the kids and drift information all will be analyzed.
"We'll see if and when we can predict elevated levels of exposure," says Fenske.
Developmental delays found
Most of the UW research focuses on organophosphates, pesticides that debilitate the nervous system of crop-destroying bugs. Unfortunately, they can do the same thing to humans.
In the worst exposures, the pesticide causes spasms before the muscles become flaccid and paralyzed. Death can occur when muscles in the airways contract or fail, a foamy secretion fills the lungs and, in extreme exposures, the brain's respiration center fails.
Typical serious exposures cause nausea, headaches, blurred vision, muscle weakness and impaired concentration.
Few studies have been conducted on the effects of chronic pesticide exposure in adults. Subtle memory problems, irritability and a sensitivity to chemical odors have emerged as possible effects, although scientists say the findings need more confirmation.
Even less research has been conducted on children exposed to pesticides over long periods of time. But a study published last year in the journal Environmental Health Perspectives attracted significant attention among scientists.
Researchers from the University of Arizona and the Instituto Tecnologico de Sonora examined two groups of 4- and 5-year-old Yaqui Indian children in northwestern Mexico.
All 50 children involved had similar genetic backgrounds, diets, drank basically the same water and had similar social behaviors. One group, living in the foothills, had no exposure to pesticides. The other, living in the agricultural Yaqui Valley, was chronically exposed to organophosphates and other pesticides.
The children grew at the same rate, but the exposed children demonstrated decreases in stamina, gross and fine eye-hand coordination, 30-minute memory and the ability to draw a figure.
Three years later, those children were still behind in their development, according to Dr. Elizabeth Guillette, lead author of the study and a research scientist at the University of Arizona.
Guillette says she has no precise comparisons with U.S. children, but believes some children of migratory farm workers in the U.S. are exposed at the same levels as the Yaqui children. She says she has conducted research with farm workers and has heard many stories of significant exposures.
"It's a very provocative study, but it definitely needs to be repeated to see if someone following a similar methodology has similar results," says Keifer, co-director of the UW's Pacific Northwest Agricultural Safety and Health Center.
Questions for farm workers
In the Yakima Valley, UW researchers are assessing the ways children are exposed to relatively low levels of pesticides through the so-called "take-home pathway."
"Pesticides attach to you," says Dr. Beti Thompson, a Fred Hutchinson Cancer Research Center scientist, UW professor and director of one of the project's field studies. "It's like sheetrock dust - it covers your clothes, your cap, your body. And if you go home with it, it can get on everything from the floor to the washing machine."
In the tiny town of Mabton, near Sunnyside in Yakima County, Guadalupe Sotelo waits outside the house where agricultural worker Elpedio Garcia, 37, lives with his parents, brother, sister-in-law and two nephews. He is one of about 500 people researchers will interview in the valley's farm communities.
When Garcia arrives home, Sotelo, senior interviewer for the study, is invited into the living room after she explains she is there to learn more about his exposure to pesticides. With other family members listening intently, she proceeds through a 29-page questionnaire with Garcia.
"In the past three months, after working in the fields, how often did you take off your shoes or boots before entering your home?" she asks in Spanish in a typical question. "How often did you wash your work clothes separately from the regular household laundry? . . . How long after work did you usually shower or take a bath? . . .
"After work, how often did you hold young children in your household while wearing your work clothes? . . . How often were carpets in your home vacuumed?"
For 20 minutes, Sotelo, a skilled interviewer and former farm worker, asks about Garcia's work and exposures to pesticides.
Besides questions about possible home contamination, she asks how often Garcia wears protective equipment in the fields and whether his employer provides it, as required by law. She asks whether warnings are given about pesticide applications, as required by law, and if he has had any symptoms of exposure.
Later, Sotelo will return to obtain urine samples from one of Garcia's nephews, 2-year-old Edwin. Dust samples will be vacuumed from four areas in the house. Edwin will get a toy for his efforts, the family $50.
Soon researchers will conduct "community intervention" - giving families ideas about how to prevent contamination in their homes, and farmers ideas about how to better protect workers. Two years from now, they will take more urine and dust samples and compare them with samples taken before explaining preventative measures.
"We hope we'll see a decrease," says Thompson. "People in the valley really care about their children. This is really a way to foster behavioral change."
Assessing danger to kids
A major focus of the project is to assess through laboratory studies just how vulnerable children are to the effects of pesticides.
In the tests, rat fetuses and newborn rats will be exposed to three pesticides: chlorpyrifos and benomyl, both organophosphates, and arsenic, which is no longer used but lingers in the soil of some farms.
The scientists will then look at the effects on three areas of the brain that develop rapidly near the time of birth - the mid-brain and hippocampus, associated with memory; and the cerebellum, associated with muscle control.
Possible changes in brain tissue, development and behavior will be assessed.
Researchers, for example, will observe how well they grow, when the rat pups' eyes open, when their teeth grow out of their gums, when they are able to turn themselves over. They will watch their reaction to noise and how well they negotiate a maze.
"We want to see which exposures are safe and which aren't," says Dr. Thomas Burbacher, director of the project's lab-based studies. "We want to provide background data for pesticide regulators so we'll have regulations with a scientific basis."
In another laboratory study, researchers are examining genetic differences that make people more or less vulnerable to pesticides. The study centers on two different forms of the enzyme paraoxonase, which breaks down pesticides and toxins in the body.
The pesticides involved include chlorpyrifos, used against bugs like carpenter ants, grasshoppers and spiders; diazinon, a common home and farm insecticide; methyl parathion, still allowed on some row crops; and sarin, the nerve gas used in biological warfare.
What type of paraoxonase you produce - and how well your liver produces it - determines how well you cope with a given toxin. People in different ethnic groups produce different amounts of paraoxonase. And young children, especially in their first six months, produce almost none of the enzyme.
Scientists hope the research will add to data they use to develop exposure limits for different groups and ages of children. Researchers also are trying to genetically engineer the enzyme so it could be produced for use in pesticide-exposure emergencies.
"What we do know now," says UW geneticist Clement Furlong, director of the study, "is that young children, especially newborns, need to avoid any exposure to pesticides."
