Page 398 - Environment: The Science Behind the Stories

little that looked like a person. By the
standards of developmental medicine,
the 4- and 5-year-old valley children
drew at the level of 2-year-olds.
Some scientists greeted Guillette’s
study skeptically, pointing out that
its sample size was too small to be
meaningful. Others said that fac-
tors the researchers missed, such as
4-year-olds 5-year-olds different parenting styles or unknown
health problems, could be to blame.
Drawings by children in the foothills Prominent toxicologists argued that
because the researchers lacked time
and money to take blood or tissue sam-
ples to check for pesticides or other
toxic substances, the study results
couldn’t be tied to agricultural chemi-
cals. Regardless of these criticisms,
Guillette maintains that her findings
show that nontraditional study methods
are a valid way to track the effects of
environmental toxicants and that pesti-
cides present complex, long-term risks
to human growth and health.
4-year-olds 5-year-olds In a follow-up study published in
Drawings by children in the valley 2006, Guillette and her colleagues found
that adolescent girls in the valley had
Figure 1 data from children in Mexico’s yaqui valley offer a startling example of apparent developed significantly less mammary
neurological effects of pesticide poisoning. Young children from foothills areas where
pesticides were not commonly used drew recognizable figures of people. Children of the tissue than girls from the foothills—a
same age from valley areas where pesticides were heavily used drew less-recognizable result, they hypothesized, that could be
figures. Adapted from Guillette, E.A., et al., 1998. Environmental Health Perspectives 106: 347–353. due to higher exposure to endocrine-
disrupting chemicals in utero. In some
cases, the reduction in mammary tissue
• Most valley children missed the drawing could earn 5 points, with 1 development was large enough to
bottle cap when dropping raisins, point each for a recognizable feature: potentially prevent some girls from being
whereas foothill children dropped head, body, arms, legs, and facial able to breastfeed their children. As this
them into the caps more often. features. Foothill children drew pictures and other studies suggest, the effects
The children’s drawings exhibited that looked like people, averaging about of toxic substances can potentially span
the most dramatic difference between 4.5 points per drawing. Valley children, multiple generations, supporting calls for
valley and foothill children (Figure 1). in contrast, averaged 1.6 points per long-term studies of the effects of toxic CHAPTER 14 • Envi R onm E n TA l H EA lTH A nd T o xi C ology
The researchers determined each drawing; their scribbles resembled chemicals on human health.

that workers in Chinese factories that manufactured BPA had Much of the research into hormone disruption has brought
four times the rate of erectile dysfunction as workers in fac- about strident debate. This is partly because a great deal of
tories where BPA wasn’t present. A follow-up study in 2010 scientific uncertainty is inherent in any young and developing
found that workers with detectable levels of BPA in their urine field. Another reason is that negative findings about chemi-
were two to four times more likely to have reduced sperm cals pose an economic threat to the manufacturers of those
counts and poorer sperm quality than workers in which no chemicals. For instance, Tyrone Hayes’s work has met with
BPA was detected. While the BPA exposure in these workers fierce criticism from scientists associated with atrazine’s
was far higher than that experienced by the average American, manufacturer, which stands to lose many millions of dollars
they represent some of the first studies to link bisphenol A if its top-selling herbicide were to be banned or restricted in
exposure to reproductive abnormalities in humans. the United States. 397

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