Environmental Toxin Bisphenol A (BPA) Can Affect Newborn Brain, Mouse Study Shows

ScienceDaily (Oct. 26, 2011) — Newborn mice that are exposed to bisphenol A develop changes in their spontaneous behavior and evince poorer adaptation to new environments, as well hyperactivity as young adults, according to researchers at Uppsala University. Their study also revealed that one of the brain's most important signal systems, the cholinergic signal system, is affected by bisphenol A and that the effect persisted into adulthood.

• Our environment contains a number of pollutants, including bisphenol A, which is used in plastics in a number of different applications. When plastic products are used, bisphenol A can leak out, which is especially problematic as it is used in baby bottles, tin cans, plastic containers, plastic mugs, which are used by people of all ages. Both in Sweden and globally, bisphenol A is widely used, and the substance has been found in human placentas, fetuses, and breast milk.

In recent years measurable amounts of bisphenol have been found in dust from regular homes, but opinion differs regarding any negative effects of bisphenol A, and risk assessments from various parts of the world present contradictory recommendations, even though the information used comes from the same research reports. In Sweden, the Swedish Chemicals Agency and the Medical Products Agency are working on a ban for bisphenol A in baby bottles and certain other plastic products.

In humans and mammals, the brain develops intensively during a limited period of time. In human babies, this brain development period runs from the seventh month of gestation through the first two years of life. The corresponding period for mice takes place during the 3-4 first weeks after birth. Uppsala researchers have shown in previous research studies that various toxic compounds can induce permanent damage to brain function when they are administered to newborn mice during this developmental period. Examples of such compounds are so-called brominated flame-retardants, polychlorinated biphenyls (PCBs), and DDT.

In an entirely new study, these researchers examined whether exposure to bisphenol A during the neonatal period can cause permanent damage to brain function. In the experiment different doses of bisphenol A were given to mice when they were ten days old. The mice underwent a so-called spontaneous behavior test as young adults, in which they were made to change cages from their well-known home cage to another identical one during one hour. Normal mice are very active during the first 20 minutes, exploring the new home environment. This activity declines during the next 20 minutes, and in the final 20 minutes it drops even more, and the mice settle down and sleep.

"In our study we found that a single exposure to bisphenol A during the short critical period of brain development in the neonatal period leads to changes in spontaneous behavior and poorer adaptation to new environments, as well as hyperactivity among young adult mice. When this is examined again later in their adult life, these functional disturbances persist, which indicates that the damage is permanent and do not in fact disappear," says Henrik Viberg at the Department of Organism Biology.

Using the same behavioral method, it was also examined whether the individuals that had received bisphenol A during their neonatal period reacted differently than normal individuals to adult exposure to nicotine, which would indicate that one of the brain's most important signal systems, the cholinergic signal system, was affected. Normal animals exposed as adults to the given dose of nicotine experience dramatically increased activity compared with animals that were not exposed to nicotine. Animals that had been exposed to bisphenol A during their neonatal period and then received nicotine as adults did not evince the same hyperactivity as normal animals at all. This indicates that the choligernic signal system had been affected and that these individuals had had developed increased sensitivity to this type of exposure in adulthood. Once again, this effect was induced during the neonatal period but persisted into adulthood.

"We have previously seen this type of effect from several other environmental toxins that are still prevalent in both indoor and outdoor environments. As these effects are similar to each other, it's possible that several different environmental toxins, including bisphenol A, may work together in causing disturbances during brain development. This in turn may mean that the individual dosages of the various environmental toxins that are required to cause disturbances may be lower than those we examined in our studies of, for example, Bisphenol and brominated flame-retardants," says Henrik Viberg.

Columbus blamed for Little Ice Age

Depopulation of Americas may have cooled climate

By Devin Powell

Web edition : 10:43 am

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MINNEAPOLIS — By sailing to the New World, Christopher Columbus and the other explorers who followed may have set off a chain of events that cooled Europe’s climate for centuries.
The European conquest of the Americas decimated the people living there, leaving large areas of cleared land untended. Trees that filled in this territory pulled billions of tons of carbon dioxidefrom the atmosphere, diminishing the heat-trapping capacity of the atmosphere and cooling climate, says Richard Nevle, a geochemist at Stanford University.
“We have a massive reforestation event that’s sequestering carbon … coincident with the European arrival,” says Nevle, who described the consequences of this change October 11 at the Geological Society of America annual meeting.
Tying together many different lines of evidence, Nevle estimated how much carbon all those new trees would have consumed. He says it was enough to account for most or all of the sudden drop in atmospheric carbon dioxide recorded in Antarctic ice during the 16th and 17th centuries. This depletion of a key greenhouse gas, in turn, may have kicked off Europe’s so-called Little Ice Age, centuries of cooler temperatures that followed the Middle Ages.
By the end of the 15th century, between 40 million and 80 million people are thought to have been living in the Americas. Many of them burned trees to make room for crops, leaving behind charcoal deposits that have been found in the soils of Mexico, Nicaragua and other countries.
About 500 years ago, this charcoal accumulation plummeted as the people themselves disappeared. Smallpox, diphtheria and other diseases from Europe ultimately wiped out as much as 90 percent of the indigenous population.
Trees returned, reforesting an area at least the size of California, Nevle estimated. This new growth could have soaked up between 2 billion and 17 billion tons of carbon dioxide from the air.
Ice cores from Antarctica contain air bubbles that show a drop in carbon dioxide around this time. These bubbles suggest that levels of the greenhouse gas decreased by 6 to 10 parts per million between 1525 and the early 1600s.
“There’s nothing else happening in the rest of the world at this time, in terms of human land use, that could explain this rapid carbon uptake,” says Jed Kaplan, an earth systems scientist at the Federal Polytechnic School of Lausanne in Switzerland.
Natural processes may have also played a role in cooling off Europe: a decrease in solar activity, an increase in volcanic activity or colder oceans capable of absorbing more carbon dioxide. These phenomena better explain regional climate patterns during the Little Ice Age, says Michael Mann, a climate researcher at Pennsylvania State University in State College.
But reforestation fits with another clue hidden in Antarctic ice, says Nevle. As the population declined in the Americas, carbon dioxide in the atmosphere got heavier. Increasingly, molecules of the gas tended to be made of carbon-13, a naturally occurring isotope with an extra neutron. That could be because tree leaves prefer to take in gas made of carbon-12, leaving the heavier version in the air.
Kaplan points out that there’s a lot of uncertainty in such isotope measurements, so this evidence isn’t conclusive. But he agrees that the New World pandemics were a major event that can’t be ignored — a tragedy that highlighted mankind’s ability to influence the climate long before the industrial revolution.