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Pesticide
Exposure and Childhood Development in the Yaqui Valley
BACKGROUND: Pesticides in two Yaqui Communities in Sonora Mexico In the 1950s, the indigenous Mayan people living in the Yaqui Valley in the Mexican state of Sonora hit a philosophical divide. Some wanted to adopt the so-called ćGreen Revolutionä modern farming techniques, including the use of pesticides and tractors, while others wanted to continue with traditional farming and ranching methods. Those wishing to adopt the modern techniques (including use of pesticides and tractors) moved to the valley of their region, and those who did not occupied the foothills. Yaqui Valley is now one of the largest agricultural areas in Mexico (31,000 hectares / 76,600 acres) and annually produces 1/2 million tons of fruits and vegetables annually, mainly for export to the U.S. and Canada. Along with increased production has come greatly increased pesticide use in all other respects, even genetic, the communities of the valley and the foothills do not differ. In the late 1980ās, the Institute for Technology in Sonora (ITSON) conducted studies in the Yaqui Valley and found high levels of pesticides in cord blood and breast milk. In the early 1990s, Dr. Jose Luiz Perez Gonzales conducted a health effects study in the Yaqui Valley and found that children had extremely high levels of pesticides in their porous organs that in some cases had led to death. Unfortunately, because of the political climate of the time, his team was not allowed to expand or even continue the study. Elizabeth Guillette, an anthropologist and research scientist, learned about these studies in the mid-1990s and obtained permission from the Mexican government to continue testing on the condition that she not use the word Īpesticide,ā which the Mexican government thought would create undue alarm among the residents of the communities. She agreed to conduct a generic ćenvironmental study.ä THE STUDY: Yaqui Valley Mothers Suspect Chemicals Are Harming Children Dr. Guillette and Maria Mercedes Meza, a chemist for Institute of Technology in Sonora (ITSON) carried out the study, entitled ćAn Anthropological Approach to the Evaluation of Preschool Children Exposed to Pesticides in Mexico,ä funded by the U.S. Government and printed in the scientific journal, Environmental Health Perspectives in June 1998. Their
study was conducted in farming communities of the Yaqui Valley
and in Tescopaco. Tescopaco, in the Sierra Madre foothills,
is the 'control site' because it is the town furthest from the
farms, about 80 km away (approximately 50 miles). These towns
are considered interesting communities to compare because the
people in these areas are very similar genetically. Those who farm in the valley use a wide mix of pesticides so it is impossible to tell what specific pesticides they have been exposed to. There is strong evidence of DDT usage and exposure, among dozens of other chemicals. Farmers would not reveal information about specific pesticides, in part because pesticides are tied to bank loans, and the banks are not willing to reveal what is being used with certain crops. However, they did tell Dr. Guillette and Ms. Meza that pesticides were applied thirty to forty times a season - about three times the number of applications reported by experts in the U.S. and Canada. The families under study lived in towns surrounded by farms. The children are exposed to aerial and ground spraying in their environment where they play and from the food they eat. Many of the valley families told the researchers that they are often showered with pesticides that come into their homes and cause problems like headaches and diarrhea. Dr. Guillette was initially interested in cancer - the dramatic, obvious outcome, like that found in laboratory rats subjected to huge amounts of chemicals. But mothers in the valley insisted that the researchers search for broader, perhaps subtle effects. The mothers already suspected that chemicals were affecting their children, but could not identify specific health effects. To uncover hidden impacts, the researchers used common intelligence and developmental diagnostics ö for example asking children, ages four and five, to perform a series of play activities corresponding to developmental levels. Tests consisted of simple tasks such as catching a ball, and dropping raisins into a bottle cap. Pediatricians to measure development in children use these same tests. Children of age three should have been able to accomplish these tasks. The research team noticed right away that the Valley children showed deficits in energy levels and in hand and eye coordination. The 4 and 5-year-old Valley children weren't performing at the level of a three year old. Childrenās
Drawings Dramatically Illustrate Problem There were also differences in behavior. The foothill children were observed to be busy with group play, whereas the valley children were more apt to play alone. Local teachers also complained that the valley children were much more difficult to teach, as they have trouble remembering and often have behavioral problems. They Yaqui mothers from the valley also reported more problems getting pregnant and higher rates of miscarriage, stillbirth, neonatal death and premature birth. Dr. Guillette made a second trip to the region two years after the first to follow up on the developmental progress and health of the children. In the second trip she noted that the valley children had continued developmental and mental deficits, including poor, sense of balance, and poorer general health. The exposed children lacked the balance to turn around on a 2x4 plank and walk back to the starting location whereas the lesser exposed could. She also found that the 7-year-old valley (exposed) children were only drawing at the 4-year-old level. The 7-year-old lesser-exposed were identifying people by gender, with a dress or pants, appropriate hair, fingers, facial features and shoes. During this second trip to Sonora, she also surveyed the children for illness during the past three months and found that the valley children had been ill about six times more often than the lesser-exposed children in the foothills. The valley children had high rates of upper respiratory infection and other symptoms such as allergies. Some of the illnesses in the valley children were associated with direct pesticide exposure, such as rashes and gastrointestinal problems. Endocrine
Disruption Suspected REFLECTIONS ON THE PROJECT: Simple Methods Generate Powerful Data The methods used in this study are attractive because they are simple and inexpensive. For example, the team Dr. Guillette is now working with in a similar study using three community researchers. A diagnostic test for a single child takes about 30 minutes. An interview with the parent of the child also takes about 30 minutes. Compared to other monitoring techniques discussed in this handbook, these methods require little technical expertise. Essentially, one merely has to follow the directions in the handbook developed by Dr. Guillette (see below). Dr. Guillette will review your interview forms, data analysis and help solve related problems using e-mail. Typical equipment includes: tape measure, tennis balls, a 2x4 plank, raisins to drop into a bottle cap, and gallon jugs. Because Dr. Guilletteās study was so widely read and well received, many researchers are now looking at how children function, especially mentally. The studies have been used mainly in the context of decreasing exposures (for example, pesticide bans in Canada resulted from this type of study). Also, through the UN convention for the elimination of POPS (Stockholm Convention), similar diagnostic methods are being used in India and elsewhere in the developing world. It is important to keep in mind that the diagnostic techniques described in this case study are not a magic bullet. As with all health effects monitoring, these methods are not sufficient evidence that the results seen are the result of any particular contaminant. They can, however, be used in conjunction with other evidence to build such a case. Researchers must also be careful not to exclude the community in designing or executing the study. Lack of community involvement in this study occurred because this monitoring study was the first of its kind and basic testing methodologies were being adapted for use at the community level. And, of course, the study was directed in response to mothersā concerns about their childrenās health. Collaboration with the community at all phases will enrich any similar studies and ensure that the best possible results are achieved. Dr. Guillette has produced a manual outlining the simple and elegant diagnostic methods used in her Yaqui research and elsewhere. It is available for download at: http://www.oztoxics.org/cmwg/library/documents_1/Community%20Health%20Assessment%20Manual.pdf Web links and contact info http://ehp.niehs.nih.gov/members/1998/106p347-353guillette/guillette-full.html Accounts of Elizabethās work in Mexico: http://www.mindfully.org/Pesticide/Cautionary-Pesticide-Tale.htm http://www.futurenet.org/25environmentandhealth/guillette.htm
4 Year Olds
5 Year Olds
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