"All the World's a Stage We Pass Through" R. Ayana

Tuesday, 16 November 2010

Girls Now Begin Puberty Aged Nine

Girls Now Begin Puberty Aged Nine
BPA, Plastics & Chemical Poisoning
GROWING numbers of girls are reaching puberty before the age of 10, raising fears of increased sexual activity among a new generation of children.
Scientists believe the phenomenon could be linked to obesity or exposure to chemicals in the food chain, and is putting girls at greater long-term risk of breast cancer.
A study has revealed that breast development in a sample of 1,000 girls started at an average age of 9 years and 10 months — an entire year earlier than when a similar cohort was examined in 1991.
The research was carried out in Denmark in 2006, the latest year for which figures were available, but experts believe the trend applies to Britain and other parts of Europe. Data from America also point to the earlier onset of puberty.
Scientists warn that such young girls are ill-equipped to cope with sexual development when they are still at primary school.
“We were very surprised that there had been such a change in a period of just 15 years,” said Anders Juul, head of the Department of Growth and Reproduction at the University hospital in Copenhagen, a world leader in the study of hormones and growth.
“If girls mature early, they run into teenage problems at an early age and they’re more prone to diseases later on. We should be worried about this regardless of what we think the underlying reasons might be. It’s a clear sign that something is affecting our children, whether it’s junk food, environmental chemicals or lack of physical activity.”
Hitting puberty early can mean longer exposure to oestrogen, which is a factor in breast cancer. There is also a greater risk of heart disease.
A number of artificially produced chemicals have been blamed for interfering with sexual development, notably bisphenol A, a plastic found in the lining of tin cans and babies’ feeding bottles.
Juul’s research team is now testing blood and urine samples from girls in the study to see if a direct link can be drawn between early sexual maturation and bisphenol A.
Another factor in puberty could be diet. Children are eating more than previous generations and growing bigger — and in many cases becoming obese.
There has been a steady lowering in the onset of puberty. In the 19th century, it was at about 15 for girls and 17 for boys.
The international standard for normal puberty in white girls was set in the 1960s at 12Å for the age when periods begin and at about 14 for boys when their voices break and their growth surges.
A more recent consensus in Britain has proved elusive. “Although we don’t have clear data here, there is evidence the same thing [as in Denmark] is happening for reasons that we don’t understand,” said Richard Sharpe, head of the Medical Research Council’s human reproductive sciences unit in Edinburgh.
“We don’t know if this is the result of better nutrition or environmental factors, but it does create social problems for girls who are already living in a sexualised society.”
Sharpe said boys had also been affected by the phenomenon. Choir schools have reported an increasing number of boys dropping out because their voices had broken at the age of 12 or 13.
Richard Stanhope, an expert in hormonal disorders in children who recently retired from Great Ormond Street hospital, said specialists in his field believed they were seeing more children going through early puberty.
“All the things we experience as teenagers are difficult enough to cope with, but when it happens at 10 or 11 it is much worse,” he said.
“These children are also at a much higher risk of being sexually abused because it is hard for some adults to understand and behave appropriately towards them.”
Girls who reach puberty early often find themselves teased at school. “I had to wear a bra at 9,” said one girl, who did not want to be named. “I used to pretend to be ill to get out of changing for PE.
“The worst part was men coming on to me as though I was an adult when actually I was 11.”
A study published in the journal Public Health Nutrition last Friday showed a link between high meat consumption and earlier puberty in girls.
Researchers at Brighton University found that 49% of girls who ate meat 12 times a week at the age of 7 had reached puberty by the age of 12 1/2, compared with 35% of those who ate meat four times a week or less.
From http://www.timesonline.co.uk/tol/news/uk/health/article7148975.ece


BPA, Chemical Used To Make Plastics, Found To Leach From Polycarbonate Drinking Bottles Into Humans

A new study from Harvard School of Public Health (HSPH) researchers found that participants who drank for a week from polycarbonate bottles -- the popular, hard-plastic drinking bottles and baby bottles -- showed a two-thirds increase in their urine of the chemical bisphenol A (BPA). Exposure to BPA, used in the manufacture of polycarbonate and other plastics, has been shown to interfere with reproductive development in animals and has been linked with cardiovascular disease and diabetes in humans.
The study is the first to show that drinking from polycarbonate bottles increased the level of urinary BPA, and thus suggests that drinking containers made with BPA release the chemical into the liquid that people drink in sufficient amounts to increase the level of BPA excreted in human urine.
In addition to polycarbonate bottles, which are refillable and a popular container among students, campers and others and are also used as baby bottles, BPA is also found in dentistry composites and sealants and in the lining of aluminum food and beverage cans. (In bottles, polycarbonate can be identified by the recycling number 7.) Numerous studies have shown that it acts as an endocrine-disruptor in animals, including early onset of sexual maturation, altered development and tissue organization of the mammary gland and decreased sperm production in offspring. It may be most harmful in the stages of early development.
"We found that drinking cold liquids from polycarbonate bottles for just one week increased urinary BPA levels by more than two-thirds. If you heat those bottles, as is the case with baby bottles, we would expect the levels to be considerably higher. This would be of concern since infants may be particularly susceptible to BPA's endocrine-disrupting potential," said Karin B. Michels, associate professor of epidemiology at HSPH and Harvard Medical School and senior author of the study.
The researchers, led by first author Jenny Carwile, a doctoral student in the department of epidemiology at HSPH, and Michels, recruited Harvard College students for the study in April 2008. The 77 participants began the study with a seven-day "washout" phase in which they drank all cold beverages from stainless steel bottles in order to minimize BPA exposure. Participants provided urine samples during the washout period. They were then given two polycarbonate bottles and asked to drink all cold beverages from the bottles during the next week; urine samples were also provided during that time.
The results showed that the participants' urinary BPA concentrations increased 69% after drinking from the polycarbonate bottles. (The study authors noted that BPA concentrations in the college population were similar to those reported for the U.S. general population.) Previous studies had found that BPA could leach from polycarbonate bottles into their contents; this study is the first to show a corresponding increase in urinary BPA concentrations in humans.
One of the study's strengths, the authors note, is that the students drank from the bottles in a normal use setting. Additionally, the students did not wash their bottles in dishwashers nor put hot liquids in them; heating has been shown to increase the leaching of BPA from polycarbonate, so BPA levels might have been higher had students drunk hot liquids from the bottles.
Canada banned the use of BPA in polycarbonate baby bottles in 2008 and some polycarbonate bottle manufacturers have voluntarily eliminated BPA from their products. With increasing evidence of the potential harmful effects of BPA in humans, the authors believe further research is needed on the effect of BPA on infants and on reproductive disorders and on breast cancer in adults.
"This study is coming at an important time because many states are deciding whether to ban the use of BPA in baby bottles and sippy cups. While previous studies have demonstrated that BPA is linked to adverse health effects, this study fills in a missing piece of the puzzle—whether or not polycarbonate plastic bottles are an important contributor to the amount of BPA in the body," said Carwile.
The study was supported by the Harvard University Center for the Environment and the National Institute of Environmental Health Sciences Biological Analysis Core, Department of Environmental Health, HSPH. Carwile was also supported by the Training Program in Environmental Epidemiology.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
Skin is no barrier to BPA, study shows
Finding suggests handling store receipts could be significant source of internal exposure
Bisphenol A readily passes through skin, French scientists report. Best known as an estrogen-mimicking constituent of some plastics and resins, BPA is also found in a large share of cash register receipt paper in the United States and Europe, a trio of studies recently indicated. One of the three also showed that the powdery coating easily rubs off onto the hands.
“The new study is now unequivocal in showing that yes, BPA can go through human skin,” says Frederick vom Saal of the University of Missouri-Columbia.
It may also explain why a survey due to appear in an upcoming issue of Environmental Health Perspectives found that among nearly 400 pregnant Cincinnati-area women, the highest BPA concentrations were in cashiers. However, Joe M. Braun and his coauthors note, "these results should be interpreted cautiously since estimates from cashiers were based on 17 women."
The French work, posted online in advance of print in Chemosphere, was conducted at INRA, the National Institute for Agricultural Research in France. Its Toulouse-based team has been investigating excised but still living skin tissue as an alternative to live animals for safety tests of cosmetics and other chemicals.
Toxicologist Daniel Zalko and his coworkers collected pig ears from slaughterhouses within five minutes of an animal being killed. In less than two hours, the tissues were in the lab where researchers removed the skin, cut it into tiny disks and cultured each in a dish.
The scientists applied BPA at various concentrations to the dry outer surface of the skin. The lowest concentration used would have delivered a dose of BPA that is in the ballpark of what could rub off onto an equivalent area of skin from handling receipt paper, Zalko says.
After three days more than half of the BPA had diffused through the skin and into the growth medium. In a living animal, Zalko says, the diffused chemical would likely be circulating in blood throughout the body.
Enzymes active in the skin transformed the majority of the BPA into metabolites known as conjugates, which have chemical “add-ons” to the main BPA molecule. BPA principally is converted into the compounds BPA glucuronide and BPA sulfate. Though such transformations are often assumed to render a chemical nontoxic, “that would be a false assumption,” Zalko says, “because any compound that has been conjugated can be deconjugated.”
To validate the value of pig skin as a human surrogate, Zalko’s group also ran the BPA experiments using tiny samples of healthy human skin that had been removed from the abdomens of roughly 40-year-old women during various surgical procedures. Again, almost half of the BPA applied passed completely through the skin. And Zalko cautions that this pass-through rate might be conservative since the cultured human skin samples weren’t as fresh — and therefore porous — as the pig ears had been.
Moreover, far less of the BPA exiting the human skin was conjugated compared with pig skin, and what had been transformed was less likely to be in the glucuronide form.
The role of metabolites in BPA’s potential toxicity is complicated, vom Saal says, because the body can — and regularly does — conjugate and deconjugate compounds. “It’s well known,” for instance, “that the body is full of desulfating enzymes, which play a role regulating estrogen levels during pregnancy.”
These new data reinforce concerns about store receipts, he adds, “because we know from many thermal papers that receipts can contain a heck of a lot of BPA.” And that BPA is about as likely to rub off receipt paper as a coating of talcum powder would be, he says.
Vom Saal’s team is just launching a study with volunteers to measure not only how much BPA people get on their hands from holding thermal receipt paper, but also whether the compound goes on to show up in their blood and urine. Those data could be available by the end of the year.
Meanwhile, the leading producer of thermal-receipt stock in the United States — Appleton Papers, which claims to have been BPA-free since 2006 — is looking to help consumers identify its receipts. “Consumers have made it clear that they want an easy way to distinguish Appleton’s receipt paper from our competitors’ paper, which all contain BPA,” says company vice president Kent Willetts. “We are preparing to launch a BPA-free receipt paper that can be quickly and easily distinguished from all others. We will rush that product to market and have it in retailers’ hands in time for the holiday shopping season.”
by Janet Raloff @ http://www.sciencenews.org/view/generic/id/64972/title/Skin_is_no_barrier_to_BPA,_study_shows

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