Page 382 - Environment: The Science Behind the Stories

Published in 2003 in the journal 10
Current Biology, Hunt’s findings set off a 8 With condition
new wave of concern over the safety of Without condition
bisphenol A. The findings were disturbing 6
because sex cells of mice and of people Mean BPA concentration (ng/ml)
divide and function in similar ways. “We 4
have observed meiotic defects in mice at
exposure levels close to or even below 2
those considered ‘safe’ for humans,”
the research paper stated. “Clearly, the 0
possibility that BPA exposure increases Diabetes Arthritis Cancer Asthma Thyroid
the likelihood of genetically abnormal Cardiovascular disease disease
offspring is too serious to be dismissed
without extensive further study.”
Since that time, dozens of other Figure 3 in a 2008 epidemiology study, average bisphenol A concentrations were
studies of BPA at low doses have significantly higher for Americans with diabetes and cardiovascular disease. Error bars
documented harmful effects in lab ani- are 95% confidence intervals. Adapted from Lang, I.A., et al., 2008. Association of urinary bisphenol A
mals, including reproductive disorders concentration with medical disorders and laboratory abnormalities in adults. JAMA 300: 1303–1310. Used
related to estrogen mimicry but also by permission of the American Medical Association.
other maladies ranging from thyroid
problems to liver damage to elevated
anxiety. Scientist Frederick vom Saal, Survey, the researchers got a repre- Previous studies of the mecha-
whose research in 1997 had shown the sentative sample of adults in the U.S. nisms by which BPA acts in cell cultures
first evidence for BPA’s effects, said in population. After controlling the data and in rodents’ bodies helped explain
2007, “This chemical is harming snails, for race/ethnicity, education, income, how and why BPA might affect liver
insects, lobsters, fish, frogs, reptiles, smoking, body mass, and other enzymes and diabetes. However, the
birds, and rats, and the chemical indus- variables, they tested for statistical reasons for cardiovascular effects
try is telling people that because you’re correlations between a series of major remain unclear.
human, unless there’s human data, you health disorders and the concentration This first direct indication of
can feel completely safe.” of BPA in people’s urine. human health impacts from BPA
Vom Saal did not have to wait These researchers’ analyses was a correlative study that does not
long for the first human study to showed that Americans with high BPA establish causation. To demonstrate
appear. In 2008, the Journal of the concentrations showed high rates of that BPA actually causes the observed
American Medical Association pub- diabetes and cardiovascular disease effects, researchers would need to
lished research led by Iain Lang (Figure 3), as well as abnormal concen- track people with low and high BPA
and David Melzer of the Peninsula trations of three liver enzymes. The team levels for years, predict who would
Medical School, Exeter, U.K. Lang and found no association with a number of most likely get sick, and test these
Melzer’s team took an epidemiologi- other conditions such as cancer, stroke, predictions with future data. It will
cal approach (pp. 393–394) to assess arthritis, thyroid disease, and respiratory take many years to complete such
BPA’s possible effects on people. diseases. The researchers also explored long-term studies. In the meantime, CHAPTER 14 • Envi R onm E n TA l H EA lTH A nd T o xi C ology
Using data from 1455 participants in correlations with other estrogenic com- more and more scientists are urging
the U.S. government’s latest National pounds and found that these did not regulators to restrict BPA based on the
Health and Nutrition Examination show the associations that BPA showed. evidence already at hand.

poverty, and poor hygiene can each foster various illnesses. Infectious disease is a greater problem in developing coun-
Lifestyle choices also matter: Smoking can lead to lung can- tries, where it accounts for close to half of all deaths. Infec-
cer, and lack of exercise can lead to heart disease. tious disease causes many fewer deaths in developed nations
Over half the world’s deaths result from noninfectious because their wealth allows their citizens better public sani-
diseases, such as cancer and heart disease, and infectious dis- tation and hygiene (which reduce the chance of contracting
eases account for almost 1 of every 4 deaths that occur each an infectious disease) and access to medicine (which enables
year—nearly 15 million people worldwide (Figure 14.3b). people to receive treatment if they contract a disease). 381

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