- Email: [email protected]
Fresh concerns over safe limit to arsenic in drinking water
For new stories every day, visit newscientist.com/news
Visuals Unlimited/naturepl.com
THE wooden hearts of two cedar trees hold a 1200-year-old cosmic mystery – evidence of an unexplained event that rocked our planet in the 8th century. Cosmic rays are subatomic particles that tear through space. When they reach Earth they react with the oxygen and nitrogen in the atmosphere, producing new particles. One of these – carbon-14 – is taken up by trees during photosynthesis and is “fixed” in the tree’s annual growth ring. Fusa Miyake at Nagoya University, Japan, and his colleagues examined the carbon-14 content of two Japanese cedar trees and were surprised to find that there was a 1.2 per cent increase in the amount of the isotope between AD 774 and 775. The typical annual variation is just 0.05 per cent (Nature, DOI: 10.1038/nature11123). What cosmic event led to the ray boost? A supernova would do it, but Miyake points out that such an event would still be visible today. It could have been a solar flare – but only if the flare was more energetic than any discovered so far. “I cannot imagine a single flare which would be so bright,” says Igor Moskalenko, an astrophysicist at Stanford University, California, who was not involved in the work. “It may be a series of weaker flares over the period of one to three years.”
Cosmic climate change may have stunted black hole formation A WARMING of the early universe caused by the greediest of black holes could have stunted the growth of the rest. Astronomical surveys suggest that supermassive black holes weighing a billion times more than the sun had formed before the universe was a billion years old. The seeds for these behemoths are thought to be black holes weighing just a few tens of solar masses. To get so big in less than a billion years, the seed black holes must have sucked in gas at a colossal rate.
In this scenario, you would expect to see a distribution of black hole masses, with intermediatesized black holes (those between 105 and 107 solar masses) in numbers orders of magnitude greater than what we see in our local universe. Something must have limited the growth of these black holes. Now Takamitsu Tanaka at the Max Planck Institute for Astrophysics in Garching, Germany, and colleagues have a climate-based explanation. They show that a prodigious amount of X-rays emitted as
the supermassive black holes gulped gas would have heated up the universe. Black holes need cool gas to grow so this would have slowed down the growth of other black holes in smaller protogalaxies, even as the growth of black holes in the most massive protogalaxies continued apace (arxiv.org/abs/1205.6467v1). “This global warming process could have basically quenched the latecomers,” says Tanaka. “The early ones end up being the monsters and they prevent the overgrowth of the rest.” FINBARR O’REILLY/Reuters/Corbis
Tree rings record vast stellar event
New concerns over arsenic in water HOW safe is our drinking water? If pregnant or lactating mice are given water containing levels of arsenic considered safe for humans, their offspring have severe growth problems. Arsenic in drinking water has been linked to many health problems. The US Environmental Protection Agency states that water containing up to 10 parts per billion (ppb) of arsenic is safe. Joshua Hamilton at the Marine Biological Laboratory in Woods Hole, Massachusetts, and his colleagues gave water containing arsenic at 10 ppb to pregnant and lactating mice, then monitored the development of their pups. The pups grew more slowly than normal. The arsenic was not passed through the milk, but it limited the nutrients it contained (PLoS One, DOI: 10.1371/journal. pone.0038249). Humans and mice show significantly different responses to arsenic, but the results are still important, says David Polya at the University of Manchester, UK, who was not involved in the work. “The adverse health effects observed here add support to concerns over the adequacy of the 10 ppb recommendation,” he says.
‘Menstrual huts’ prevent cuckoldry ENSURING your partner doesn’t cheat is a perennial problem. Perhaps one solution is religion. Beverly Strassmann at the University of Michigan in Ann Arbor has spent years studying the Dogon people of Mali, west Africa. Women who practise the traditional Dogon religion, unlike those who are Muslim or Christian, spend five days a month around the time of menstruation in a highly visible “menstrual hut”. Strassmann tested paternity in 1700 Dogon father and son pairs and found that those who practised the traditional religion were four times
less likely to be raising someone else’s son than those who practised Christianity (Proceedings of the National Academy of Sciences, DOI: 10.073/pnas.1110442109). The findings suggest that the huts make it easier for husbands to monitor wives close to fertile periods. No differences were observed between the Dogon and the Muslim group, perhaps because women are required to tell their husbands when they menstruate. Strassmann suggests that these traditions may have developed as a way to boost reproductive success.
9 June 2012 | NewScientist | 17
Visuals Unlimited/naturepl.com
THE wooden hearts of two cedar trees hold a 1200-year-old cosmic mystery – evidence of an unexplained event that rocked our planet in the 8th century. Cosmic rays are subatomic particles that tear through space. When they reach Earth they react with the oxygen and nitrogen in the atmosphere, producing new particles. One of these – carbon-14 – is taken up by trees during photosynthesis and is “fixed” in the tree’s annual growth ring. Fusa Miyake at Nagoya University, Japan, and his colleagues examined the carbon-14 content of two Japanese cedar trees and were surprised to find that there was a 1.2 per cent increase in the amount of the isotope between AD 774 and 775. The typical annual variation is just 0.05 per cent (Nature, DOI: 10.1038/nature11123). What cosmic event led to the ray boost? A supernova would do it, but Miyake points out that such an event would still be visible today. It could have been a solar flare – but only if the flare was more energetic than any discovered so far. “I cannot imagine a single flare which would be so bright,” says Igor Moskalenko, an astrophysicist at Stanford University, California, who was not involved in the work. “It may be a series of weaker flares over the period of one to three years.”
Cosmic climate change may have stunted black hole formation A WARMING of the early universe caused by the greediest of black holes could have stunted the growth of the rest. Astronomical surveys suggest that supermassive black holes weighing a billion times more than the sun had formed before the universe was a billion years old. The seeds for these behemoths are thought to be black holes weighing just a few tens of solar masses. To get so big in less than a billion years, the seed black holes must have sucked in gas at a colossal rate.
In this scenario, you would expect to see a distribution of black hole masses, with intermediatesized black holes (those between 105 and 107 solar masses) in numbers orders of magnitude greater than what we see in our local universe. Something must have limited the growth of these black holes. Now Takamitsu Tanaka at the Max Planck Institute for Astrophysics in Garching, Germany, and colleagues have a climate-based explanation. They show that a prodigious amount of X-rays emitted as
the supermassive black holes gulped gas would have heated up the universe. Black holes need cool gas to grow so this would have slowed down the growth of other black holes in smaller protogalaxies, even as the growth of black holes in the most massive protogalaxies continued apace (arxiv.org/abs/1205.6467v1). “This global warming process could have basically quenched the latecomers,” says Tanaka. “The early ones end up being the monsters and they prevent the overgrowth of the rest.” FINBARR O’REILLY/Reuters/Corbis
Tree rings record vast stellar event
New concerns over arsenic in water HOW safe is our drinking water? If pregnant or lactating mice are given water containing levels of arsenic considered safe for humans, their offspring have severe growth problems. Arsenic in drinking water has been linked to many health problems. The US Environmental Protection Agency states that water containing up to 10 parts per billion (ppb) of arsenic is safe. Joshua Hamilton at the Marine Biological Laboratory in Woods Hole, Massachusetts, and his colleagues gave water containing arsenic at 10 ppb to pregnant and lactating mice, then monitored the development of their pups. The pups grew more slowly than normal. The arsenic was not passed through the milk, but it limited the nutrients it contained (PLoS One, DOI: 10.1371/journal. pone.0038249). Humans and mice show significantly different responses to arsenic, but the results are still important, says David Polya at the University of Manchester, UK, who was not involved in the work. “The adverse health effects observed here add support to concerns over the adequacy of the 10 ppb recommendation,” he says.
‘Menstrual huts’ prevent cuckoldry ENSURING your partner doesn’t cheat is a perennial problem. Perhaps one solution is religion. Beverly Strassmann at the University of Michigan in Ann Arbor has spent years studying the Dogon people of Mali, west Africa. Women who practise the traditional Dogon religion, unlike those who are Muslim or Christian, spend five days a month around the time of menstruation in a highly visible “menstrual hut”. Strassmann tested paternity in 1700 Dogon father and son pairs and found that those who practised the traditional religion were four times
less likely to be raising someone else’s son than those who practised Christianity (Proceedings of the National Academy of Sciences, DOI: 10.073/pnas.1110442109). The findings suggest that the huts make it easier for husbands to monitor wives close to fertile periods. No differences were observed between the Dogon and the Muslim group, perhaps because women are required to tell their husbands when they menstruate. Strassmann suggests that these traditions may have developed as a way to boost reproductive success.
9 June 2012 | NewScientist | 17