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Scientists Urge Study of Environmental Factors That May Speed Aging
New paper urges more work on “gerontogens” in the environment


PHOTOGRAPH BY LYNN JOHNSON, NATIONAL GEOGRAPHIC CREATIVE




Ed Yong
National Geographic
PUBLISHED MAY 28, 2014

Why do our bodies age at different rates? Why can some people run marathons at the age of 70, while others are forced to use a walker?
Genes are only part of the answer. A trio of scientists from the University of North Carolina argue in a new paper that more work needs to be done on “gerontogens”—factors, including substances in the environment, that can accelerate the aging process.
Possible gerontogens include arsenic in groundwater, benzene in industrial emissions, ultraviolet radiation in sunlight, and the cocktail of 4,000 toxic chemicals in tobacco smoke. Activities may also be included, like ingesting excessive calories, or suffering psychological stress.
Writing in Trends in Molecular Medicine, Jessica Sorrentino, Hanna Sanoff, and Norman Sharpless argue that focusing on such factors would complement more popular approaches like studying molecular changes in old bodies and searching for genes that are linked to long life.
"People have focused on slowing aging, which always struck me as premature," says Sharpless. Even if scientists announced tomorrow that they’d discovered an antiaging pill, he says, people would have to take it for decades.
"Getting [healthy] people to take medicine for a long time is challenging, and there are always side effects," Sharpless says. "If you identify stuff in the environment that affects aging, that’s knowledge we could use today."
Frailty and Mental Decline
Twin studies have suggested that only around 25 percent of the variation in the human life span is influenced by genes. The rest must be influenced by other factors, including accidents, injuries, and exposure to substances that accelerate aging.
"The idea that environmental factors can accelerate aging has been around for a while, [but] I agree that the study of gerontogens has lagged behind other areas of aging research," says Judith Campisi of the Buck Institute for Research on Aging.
She adds that scientists have become more interested in these substances in recent years after learning that many types of chemotherapy, and some anti-HIV drugs, can speed the onset of age-related traits like frailty and mental decline.
The quest to identify gerontogens is partly a quest to find better way of measuring biological age. There are several options, each one imperfect.
Researchers could look in the brain and measure levels of beta-amyloid, a protein linked to Alzheimer’s disease, but these levels would not reflect aging in other parts of the body.
They could measure the length of telomeres—protective caps at the end of our DNA that wear away with time. But doing so is hard and expensive, and telomere length naturally varies between people of the same age.
Sharpless’s team has focused on one particular aspect of aging—a process called senescence, in which cells permanently stop dividing. Senescent cells accumulate as we get older, and they contain ten times the usual levels of a protein called p16.
Glowing Mice
The team has developed a strain of mice that produce a protein that glows whenever they make p16. “When they get older and have lots of senescent cells, they glow like crazy,” says Sharpless. “When you expose them to gerontogens, they’ll glow at a younger age than you expect.”
The team members are using their mice to test potential gerontogens, and they’ve sent the animals to around 50 different labs that are doing the same. They’re also working with a company called HealthSpan Diagnostics to create a version of their p16 test that could measure biological age in people.
"One marker isn’t going to do it. You need a panel," says Sharpless. "The perfect test doesn’t exist, but I’m certain that within my lifetime we’ll have the ability to measure someone’s physiological age with precision."
read more from Nat Geo

scienceyoucanlove:

Scientists Urge Study of Environmental Factors That May Speed Aging

New paper urges more work on “gerontogens” in the environment

PHOTOGRAPH BY LYNN JOHNSON, NATIONAL GEOGRAPHIC CREATIVE

Ed Yong

National Geographic

PUBLISHED MAY 28, 2014

Why do our bodies age at different rates? Why can some people run marathons at the age of 70, while others are forced to use a walker?

Genes are only part of the answer. A trio of scientists from the University of North Carolina argue in a new paper that more work needs to be done on “gerontogens”—factors, including substances in the environment, that can accelerate the aging process.

Possible gerontogens include arsenic in groundwater, benzene in industrial emissions, ultraviolet radiation in sunlight, and the cocktail of 4,000 toxic chemicals in tobacco smoke. Activities may also be included, like ingesting excessive calories, or suffering psychological stress.

Writing in Trends in Molecular Medicine, Jessica Sorrentino, Hanna Sanoff, and Norman Sharpless argue that focusing on such factors would complement more popular approaches like studying molecular changes in old bodies and searching for genes that are linked to long life.

"People have focused on slowing aging, which always struck me as premature," says Sharpless. Even if scientists announced tomorrow that they’d discovered an antiaging pill, he says, people would have to take it for decades.

"Getting [healthy] people to take medicine for a long time is challenging, and there are always side effects," Sharpless says. "If you identify stuff in the environment that affects aging, that’s knowledge we could use today."

Frailty and Mental Decline

Twin studies have suggested that only around 25 percent of the variation in the human life span is influenced by genes. The rest must be influenced by other factors, including accidents, injuries, and exposure to substances that accelerate aging.

"The idea that environmental factors can accelerate aging has been around for a while, [but] I agree that the study of gerontogens has lagged behind other areas of aging research," says Judith Campisi of the Buck Institute for Research on Aging.

She adds that scientists have become more interested in these substances in recent years after learning that many types of chemotherapy, and some anti-HIV drugs, can speed the onset of age-related traits like frailty and mental decline.

The quest to identify gerontogens is partly a quest to find better way of measuring biological age. There are several options, each one imperfect.

Researchers could look in the brain and measure levels of beta-amyloid, a protein linked to Alzheimer’s disease, but these levels would not reflect aging in other parts of the body.

They could measure the length of telomeres—protective caps at the end of our DNA that wear away with time. But doing so is hard and expensive, and telomere length naturally varies between people of the same age.

Sharpless’s team has focused on one particular aspect of aging—a process called senescence, in which cells permanently stop dividing. Senescent cells accumulate as we get older, and they contain ten times the usual levels of a protein called p16.

Glowing Mice

The team has developed a strain of mice that produce a protein that glows whenever they make p16. “When they get older and have lots of senescent cells, they glow like crazy,” says Sharpless. “When you expose them to gerontogens, they’ll glow at a younger age than you expect.”

The team members are using their mice to test potential gerontogens, and they’ve sent the animals to around 50 different labs that are doing the same. They’re also working with a company called HealthSpan Diagnostics to create a version of their p16 test that could measure biological age in people.

"One marker isn’t going to do it. You need a panel," says Sharpless. "The perfect test doesn’t exist, but I’m certain that within my lifetime we’ll have the ability to measure someone’s physiological age with precision."

read more from Nat Geo

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On April 26, 1986, a sudden surge of power during a reactor systems test destroyed Unit 4 of the nuclear power station at Chernobyl, Ukraine, in the former Soviet Union. The accident and the fire that followed released massive amounts of radioactive material into the environment.

Emergency crews responding to the accident used helicopters to pour sand and boron on the reactor debris. The sand was to stop the fire and additional releases of radioactive material; the boron was to prevent additional nuclear reactions. A few weeks after the accident, the crews completely covered the damaged unit in a temporary concrete structure, called the “sarcophagus,” to limit further release of radioactive material. The Soviet government also cut down and buried about a square mile of pine forest near the plant to reduce radioactive contamination at and near the site. Chernobyl’s three other reactors were subsequently restarted but all eventually shut down for good, with the last reactor closing in 1999. The Soviet nuclear power authorities presented their initial accident report to an International Atomic Energy Agency meeting in Vienna, Austria, in August 1986.

After the accident, officials closed off the area within 30 kilometers (18 miles) of the plant, except for persons with official business at the plant and those people evaluating and dealing with the consequences of the accident and operating the undamaged reactors. The Soviet (and later on, Russian) government evacuated about 115,000 people from the most heavily contaminated areas in 1986, and another 220,000 people in subsequent years (Source: UNSCEAR 2008, pg. 53).

The Chernobyl accidents severe radiation effects killed 28 of the site’s 600 workers in the first four months after the event. Another 106 workers received high enough doses to cause acute radiation sickness. Two workers died within hours of the reactor explosion from non-radiological causes. Another 200,000 cleanup workers in 1986 and 1987 received doses of between 1 and 100 rem (The average annual radiation dose for a U.S. citizen is about .6 rem). Chernobyl cleanup activities eventually required about 600,000 workers, although only a small fraction of these workers were exposed to elevated levels of radiation. Government agencies continue to monitor cleanup and recovery workers’ health. (UNSCEAR 2008, pg. 47, 58, 107, and 119)

The Chernobyl accident contaminated wide areas of Belarus, the Russian Federation, and Ukraine inhabited by millions of residents. Agencies such as the World Health Organization have been concerned about radiation exposure to people evacuated from these areas. The majority of the five million residents living in contaminated areas, however, received very small radiation doses comparable to natural background levels (0.1 rem per year). (UNSCEAR 2008, pg. 124-25) Today the available evidence does not strongly connect the accident to radiation-induced increases of leukemia or solid cancer, other than thyroid cancer. Many children and adolescents in the area in 1986 drank milk contaminated with radioactive iodine, which delivered substantial doses to their thyroid glands. To date, about 6,000 thyroid cancer cases have been detected among these children. Ninety-nine percent of these children were successfully treated; 15 children and adolescents in the three countries died from thyroid cancer by 2005. The available evidence does not show any effect on the number of adverse pregnancy outcomes, delivery complications, stillbirths or overall health of children among the families living in the most contaminated areas. (UNSCEAR 2008, pg. 65)

Experts conclude some cancer deaths may eventually be attributed to Chernobyl over the lifetime of the emergency workers, evacuees and residents living in the most contaminated areas. These health effects are far lower than initial speculations of tens of thousands of radiation-related deaths.

The accident caused the largest uncontrolled radioactive release into the environment ever recorded for any civilian operation, and large quantities of radioactive substances were released into the air for about 10 days. This caused serious social and economic disruption for large populations in Belarus, Russia and Ukraine. Two radionuclides, the short-lived iodine-131 and the long-lived caesium-137, were particularly significant for the radiation dose they delivered to members of the public.

It is estimated that all of the xenon gas, about half of the iodine and caesium, and at least 5% of the remaining radioactive material in the Chernobyl 4 reactor core (which had 192 tonnes of fuel) was released in the accident. Most of the released material was deposited close by as dust and debris, but the lighter material was carried by wind over the Ukraine, Belarus, Russia and to some extent over Scandinavia and Europe.

The casualties included firefighters who attended the initial fires on the roof of the turbine building. All these were put out in a few hours, but radiation doses on the first day were estimated to range up to 20,000 millisieverts (mSv), causing 28 deaths – six of which were firemen – by the end of July 1986.

The next task was cleaning up the radioactivity at the site so that the remaining three reactors could be restarted, and the damaged reactor shielded more permanently. About 200,000 people (‘liquidators’) from all over the Soviet Union were involved in the recovery and clean-up during 1986 and 1987. They received high doses of radiation, averaging around 100 millisieverts. Some 20,000 of them received about 250 mSv and a few received 500 mSv. Later, the number of liquidators swelled to over 600,000 but most of these received only low radiation doses. The highest doses were received by about 1000 emergency workers and on-site personnel during the first day of the accident.

Initial radiation exposure in contaminated areas was due to short-lived iodine-131; later caesium-137 was the main hazard. (Both are fission products dispersed from the reactor core, with half lives of 8 days and 30 years, respectively. 1.8 EBq of I-131 and 0.085 EBq of Cs-137 were released.) About five million people lived in areas of Belarus, Russia and Ukraine contaminated (above 37 kBq/m2 Cs-137 in soil) and about 400,000 lived in more contaminated areas of strict control by authorities 


The plant operators’ town of Pripyat was evacuated on 27 April (45,000 residents). By 14 May, some 116,000 people that had been living within a 30-kilometre radius had been evacuated and later relocated. About 1000 of these returned unofficially to live within the contaminated zone. Most of those evacuated received radiation doses of less than 50 mSv, although a few received 100 mSv or more.

In the years following the accident, a further 220,000 people were resettled into less contaminated areas, and the initial 30 km radius exclusion zone (2800 km2) was modified and extended to cover 4300 square kilometres. This resettlement was due to application of a criterion of 350 mSv projected lifetime radiation dose, though in fact radiation in most of the affected area (apart from half a square kilometre) fell rapidly so that average doses were less than 50% above normal background of 2.5 mSv/yr.  

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