Page 397 - Environment: The Science Behind the Stories

THE SCIENCE BEHIND THE STORY

Pesticides and in the valley and foothills continued
Child Development to share the same culture, diet,
education system, income levels,
in Mexico’s Yaqui and family structure.
At the time of the study, in
Valley 1994, valley farmers planted crops
With spindly arms and big, round eyes, twice a year, applying pesticides up
one set of pictures shows the sorts of to 45 times from planting to harvest.
stick figures drawn by young children A previous study conducted in the A yaqui family
everywhere. Next to them is another valley in 1990, focusing on areas
group of drawings, mostly discon- with the largest farms, had indicated
nected squiggles and lines, resembling high levels of multiple pesticides The researchers also measured
nothing. Both sets of pictures are in the breast milk of mothers and in each child’s height and weight. When
intended to depict people. The main the umbilical cord blood of newborn all tests were completed, each child
difference identified between the two babies. In contrast, foothill families was asked what he or she had been
groups of young artists: long-term avoided chemical pesticides in their promised and received a red balloon.
pesticide exposure. gardens and homes. Although the two groups of
Children’s drawings are not a typi- To understand how pesticide children did not differ in height and
cal tool of toxicology, but anthropolo- exposure affects childhood develop- weight, they differed markedly in other
gist Elizabeth Guillette was interested ment, Guillette and fellow researchers measures of development. Valley
in the effects of pesticides on children studied 50 preschoolers aged 4 to 5, of children lagged far behind the foot-
and wanted to try new methods. She whom 33 were from the valley and 17 hill children in coordination, physical
devised tests to measure childhood from the foothills. Each child under- endurance, long-term memory, and
development based on techniques from went a half-hour exam, during which fine motor skills:
anthropology and medicine. Search- researchers showed a red balloon, • Valley children had great difficulty
ing for a study site, Guillette found the promising to give the balloon later as a catching the ball.
Yaqui valley region of northwestern gift, and using the promise to evaluate • The average valley child could jump
Mexico. long-term memory. Each child was then for 52 seconds, compared to 88
The Yaqui valley is farming coun- put through a series of physical and seconds for foothill children.
try, worked for generations by the mental tests: • Each group did fairly well repeating
indigenous group that gives the region • Catching a ball from distances of up to numbers, but valley children showed
its name. Synthetic pesticides arrived 3 m (10 ft) away, to test coordination poor long-term memory. At the end
in the area in the 1940s. Some Yaqui • Jumping in place for as long as pos- of the test, all but one of the foothill
embraced the agricultural innovations, sible, to assess endurance children remembered that they had
spraying their farms in the valley to • Drawing a picture of a person, as a been promised a balloon, and 59%
increase their yields. Yaqui farmers measure of perception remembered it was red. However, of
in the surrounding foothills, however, • Repeating a short string of num- the valley children only 27% remem-
generally chose to bypass the chemi- bers, to test short-term memory bered the color of the balloon, only
cals and to continue following more • Dropping raisins into a bottle cap 55% remembered they’d be getting
traditional farming practices. Although from a height of about 13 cm (5 in.), a balloon, and 18% were unable to
differing in farming techniques, Yaqui to gauge fine-motor skills remember anything about a balloon.

Scientists first noted endocrine-disrupting effects decades function, brain and nervous system function, and other hor-
ago, but the idea that synthetic chemicals might be altering the mone-driven processes. Evidence is strongest so far in non-
hormones of animals was not widely appreciated until the 1996 human animals, but many studies suggest impacts on people.
publication of the book Our Stolen Future, by Theo Colburn, Some researchers argue that the sharp rise in breast cancer
Dianne Dumanoski, and J.P. Myers. Like Silent Spring, this book rates (one in eight U.S. women today develops breast cancer)
integrated scientific work from various fields and presented a may be due to hormone disruption, because an excess of estro-
unified picture that shocked many readers—and brought criti- gen appears to feed tumor development in older women. Other
cism from some scientists and from the chemical industry. studies suggest that endocrine disruptors may account for ris-
Today, thousands of studies have linked hundreds of ing rates of testicular cancer, undescended testicles, and geni-
396 substances to effects on reproduction, development, immune tal birth defects in men. For example, a 2009 study determined

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