My favourite journal. Enjoy.
 
February 19, 2008 
Plastic (Not) Fantastic: Food Containers Leach a Potentially Harmful  Chemical
Is bisphenol A, a major ingredient in many plastics, healthy for children  
and other living things?
By David Biello  

 
 
CHEMICAL LEACHING: When  exposed to hot water, plastic bottles--including 
baby bottles--leach a chemical  that is known to mimic estrogens in the body.
COURTESY OF THE UNIVERSITY OF CINCINNATI
Bisphenol A (BPA) is a ubiquitous compound in plastics. First synthesized in  
1891, the chemical has become a key building block of _plastics_ 
(http://www.sciam.com/article.cfm?id=how-are-polymers-made)  from polycarbonate to 
polyester; in the U.S.  alone more than 2.3 billion pounds (1.04 million metric tons) 
of the stuff is  manufactured annually. 
Since at least 1936 it has been known that BPA mimics estrogens, binding to  
the same receptors throughout the human body as natural female hormones. And  
tests have shown that the chemical can promote _human breast cancer cell 
growth_ 
(http://www.sciam.com/article.cfm?id=bringing-cancer-to-dinner-table-breast-cancer-cells-grow-under-influence-fish-flesh)  as well as decrease  sperm 
count in rats, among other effects. These findings have raised questions  about 
the potential health risks of BPA, especially in the wake of hosts of  studies 
showing that it leaches from plastics and resins when they are exposed  to 
hard use or high temperatures (as in microwaves or dishwashers). 
The U.S. Centers for Disease Control (CDC) found traces of BPA in nearly all  
of the urine samples it collected in 2004 as part of an effort to gauge the  
prevalence of various chemicals in the human body. It appeared at levels 
ranging  from 33 to 80 nanograms (a nanogram is one billionth of a gram) per 
kilogram of  body weight in any given day, levels 1,000 times lower than the 50 
micrograms  (one millionth of a gram) per kilogram of bodyweight per day 
considered safe by  the U.S. Environmental Protection Agency (EPA) and the European 
Union's (E.U.)  European Food Safety Authority (EFSA). 
Studies suggest that BPA does not linger in the body for more than a few days 
 because, once ingested, it is broken down into glucuronide, a waste product 
that  is easily excreted. Yet, the CDC found glucuronide in most urine 
samples,  suggesting constant exposure to it. "There is low-level exposure but 
regular  low-level exposure," says chemist Steven Hentges, executive director of the 
 polycarbonate / BPA global group of the American Chemistry Council.  "It  
presumably is in our diet." 
BPA is routinely used to line cans to prevent corrosion and food  
contamination; it also makes plastic cups and baby and other bottles transparent  and 
shatterproof. When the polycarbonate plastics and epoxy resins made from the  
chemical are exposed to hot liquids, BPA leaches out 55 times faster than it  
does under normal conditions, according to a new study by Scott Belcher, an  
endocrine biologist at the University of Cincinnati. "When we added boiling  water 
[to bottles made from polycarbonate] and allowed it to cool, the rate [of  
leakage] was greatly increased," he says, to a level as high as 32 nanograms per 
 hour. 
A recent report in the journal Reproductive Toxicology found that  humans 
must be exposed to levels of BPA at least 10 times what the EPA has  deemed safe 
because of the amount of the chemical detected in tissue and blood  samples. 
"If, as some evidence indicates, humans metabolize BPA more rapidly  than 
rodents," wrote study author Laura Vandenberg, a developmental biologist at  Tufts 
University in Boston, "then human daily exposure would have to be even  higher 
to be sufficient to produce the levels observed in human serum." 
The CDC data shows that 93 percent of 2,157 people between the ages of six  
and 85 tested had detectable levels of BPA's by-product in their urine.  
"Children had higher levels than adolescents and adolescents had higher levels  than 
adults," says endocrinologist Retha Newbold of the U.S. National Institute  
of Environmental Health Sciences, who found that BPA impairs fertility in 
female  mice. "In animals, BPA can cause permanent effects after very short periods 
of  exposure. It doesn't have to remain in the body to have an effect." 
But experts are split on the potential health hazards to humans. The Food and 
 Drug Administration has approved its use and the EPA does not consider it 
cause  for concern. One U.S. National Institutes of Health (NIH) panel agreed, 
but  another team of government scientists last year found that the amount of 
BPA  present in humans exceeds levels that have caused ill effects in animals. 
They  also found that adults' ability to tolerate it does not preclude 
damaging  effects in infants and children. 
"It is the unborn baby and children that investigators are most worried  
about," Newbold says, noting that BPA was linked to increased breast and  prostate 
cancer occurrences, altered menstrual cycles and diabetes in lab mice  that 
were still developing. 
Fred vom Saal, a reproductive biologist at the University of  Missouri–
Columbia, warns that babies likely face the "highest exposure" in human  
populations, because both baby bottles and infant formula cans likely leach BPA.  "In 
animal studies, the levels that cause harm happen at 10 times below what is  
common in the U.S." says vom Saal, who also headed the NIH panel that concluded  
the chemical may pose risks to humans. 
Amid growing concern, Rep. John Dingell (D–Mich.) chairman of the House  
Committee on Energy and Commerce, has _launched an investigation_ 
(http://energycommerce.house.gov/Investigations/Bisphenol.shtml)  into BPA, sending letters  
last month to the FDA and seven manufacturers of infant products sold in the  
U.S. requesting information on any BPA safety tests as well as specific levels  
in the baby goods. The companies that make Similac, Earth's Best and Good 
Start  have already responded, confirming that they coat the inside of their cans 
with  BPA but that analyses did not detect it in the contents. They also 
emphasize  that FDA has approved BPA for such use. 
"Based on the studies reviewed by FDA, adverse effects occur in animals only  
at levels of BPA that are far higher orders of magnitude than those to which  
infants or adults are exposed," says FDA spokeswoman Stephanie Kwisnek.  
"Therefore, FDA sees no reason to ban or otherwise restrict the uses now  
authorized at this time." 
FDA first approved BPA as a food container in 1963 because no ill effects  
from its use had been shown. When Congress passed a law—the Toxic Substances  
Control Act of 1976—mandating that the EPA conduct or review safety studies on  
new chemicals before giving them the nod, compounds like BPA were already on 
the  market. Therefore, they were not subject to the new rules nor required to  
undergo additional testing unless specific concerns had been raised (such as 
in  the case of PCBs). "The science that exists today supports the safety of 
BPA,"  ACC's Hentges says, based largely on research his organization has 
funded. 
But other studies since 1976 have shown that small doses (less than one part  
per billion) of estrogenlike chemicals, such as BPA, may be damaging. "In 
fetal  mouse prostate you can stimulate receptors with estradiol at about two 
tenths of  a part per trillion, and with BPA at a thousand times higher," vom 
Saal says.  "That's still 10 times lower than what a six-year-old has." In other 
words,  children six years of age were found to have higher levels of BPA's 
by-product  glucuronide in their urine than did mice dosed with the chemical 
that later  developed cancer and other health issues. 
Further complicating the issue is the stew of _other estrogen-mimicking 
chemicals_ 
(http://www.sciam.com/article.cfm?id=bringing-cancer-to-dinner-table-breast-cancer-cells-grow-under-influence-fish-flesh)  to which humans are  
routinely exposed, from soy to _antibacterial ingredients in some soaps_ 
(http://www.sciam.com/article.cfm?id=strange-but-true-antibacterial-products-may-do-more-h
arm-than-good) . The effects of  such chemical mixtures are not known but 
scientists say they may serve to  enhance the ill effects of one another. "The 
assumption that natural estrogens  are somehow immediately good for you and 
these chemicals are immediately bad,"  Belcher says, "is probably not a reasonable 
assumption to make." 
The chemical industry argues that unless BPA is proved to have ill effects it 
 should continue to be manufactured and used, because it is cheap, 
lightweight,  shatterproof and offers other features that are hard to match. "There is 
no  alternative for either of those materials [polycarbonate plastics and epoxy 
 resins] that would simply drop in where those materials are used," Hentges  
says. 
Not so, says vom Saal, who notes that there are plenty of other materials,  
such as polyethylene and polypropylene plastics, that would be fine substitutes 
 in at least some applications. "There are a whole variety of different kinds 
of  plastic materials and glass," he says. "They are all more stable than  
polycarbonate." 
Concern over BPA is not confined only to the U.S. Japanese manufacturers  
began to use natural resin instead of BPA to line cans in 1997 after Japanese  
scientists showed that it was leaching out of baby bottles. A subsequent study  
there that measured levels in urine in 1999 found that they had dropped  
significantly. 
A new E.U. law (Registration, Evaluation, Authorization and Restriction of  
Chemical Substances, or REACH), which took effect last year, requires that  
chemicals, such as BPA, be proved safe. Currently, though, it continues to be  
used in Europe; the EFSA last year found no reason for alarm based on rodent  
studies. European scientists cited multigenerational rat studies as reassuring  
and noted that mouse studies may be flawed because the tiny rodent is more  
susceptible to estrogens. 
For now, U.S. scientists with concerns about BPA recommend that anyone  
sharing those worries avoid using products made from it: Polycarbonate plastic  is 
clear or colored and typically marked with a number 7 on the bottom, and  
canned foods such as soups can be purchased in cardboard cartons instead. 
If canned goods or clear plastic bottles are a must, such containers should  
never be microwaved, used to store heated liquids or foods, or washed in hot  
water (either by hand or in much hotter dishwashers). "These are fantastic  
products and they work well … [but] based on my knowledge of the scientific  
data, there is reason for caution," Belcher says. "I have made a decision for  
myself not to use them."



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