Reunion day

April 20th was some sort of red-letter day and Stephen was literal sporting and spouting red! Sahji, Sreenath, Riju and me came together after a really long period, we had been on our own ways and there was never much chance to meet, but with the magnetic Riju around there was no escaping. The ocassion also was a happy one for Dr Anirudhan who now heads the dept at Kariavattom for the next 3 years. Shaji is dabbling with Metamorphism as well as Hydrogeology these days, and his MSc students have started looking into the fluid processes in cordierite formation from the KKB. With a US govt GIS analyst in the form of Riju offering collaboration the dept's GIS endeavors are bound to get a boost, as also some international exposure.

Kerala: Natural Radiation - no risk?

Natural radiation poses no major risk

K. S. Jayaraman


Team leader Sher Ali.Genetic risk due to high natural background radiation is "a lot less than one has imagined earlier," according to a study just reported by researchers at the National Institute of Immunology NII in New Delhi1.

While natural background radiation may be responsible for varying alterations, it leaves the DNA of the vital germ line intact, they say. "Our study shows that the germ line is protected because the human genome has some unknown but powerful mechanism of protecting it," Sher Ali, a molecular geneticist who led the team told Nature India.

The findings should put at rest fears that people living in coastal areas of the south Indian state of Kerala are at risk of becoming infertile because they are exposed to natural background radiation that is ten-fold higher than the worldwide average. The radiation is the result of thorium bearing monazite minerals in the beach sands.

In their study the NII team looked for possible structural variations in the Y chromosome in blood and semen samples of 390 males of two generations at Chavara and Thevara — two high radiation regions of Kerala. They compared the results with those obtained from similar samples from 390 healthy unexposed males of matched age groups from Kochi (Kerala) and 400 normal males from different parts of India.

"We chose the Y chromosome as it is an ideal candidate to be assessed for possible genetic alterations induced by ionizing radiation due to its haploid status (having only one member of chromosome pair)," Ali said.

Containing fewer than 50 genes or gene families coding for proteins, Y-chromosome is not essential for life but harbors several testis-specific genes necessary for sperm production, and hence continuation of the species. At least three non-overlapping regions of the Y chromosome — (Azoospermia factors a, b, and c) — are essential for sperm production. Micro-deletions in these regions affecting one or more of the candidate genes (DAZ, RBMY, DBY, and USP9Y) cause male infertility. The SRY gene in the Y chromosome plays a predominant role in male sex determination.

The scientists found that barring two per cent, all the 790 unexposed (control) males from Kerala and other parts of India were free from micro-deletions. In contrast more than 90 per cent of males exposed to background radiation showed random micro-deletions in the Azoospermia factor. And, in about 80 per cent of them tandem duplication and multiple copies of 11 different Y-linked genes were found. For instance, more than 85 per cent of exposed males showed 2-8 copies of the SRY gene.

But remarkably all these genetic alterations in the exposed population were detected only in blood samples but not in the germ line (sperm) samples suggesting that sperm cells are somehow protected from background radiation. "Absence of micro-deletions in the germline explains the normal fertility status of the exposed males," Sanjay Premi, one of the authors told Nature India.

Where do the germ cells derive the protection from? Ali says that germ cells, originating from the gonad's somatic cells, most likely activate some still unknown genes that sense the defective ones and triggers apoptosis (programmed cell death). "The defective sperms are eliminated and quickly replaced by fresh ones and thus what we see is always a clean picture in case of germ line," Ali said. However that is not true in case of blood cells meaning blood cells are not treated in the same way as germ cells in the body. "I would love to call it nature's marvel," Ali said adding that "this is the hypothesis; we are yet to prove this."

According to the NII scientists the tandem duplication and multiple copies of genes detected in blood samples of exposed population "is a possible genome strategy to absorb the mutational loads caused by the radiation."

Previous studies on the high radiation areas of Kerala were focused on the cases of Down's syndrome, congenital malformations, chromosomal aberrations in humans and phenotypic changes in the rats. Some groups also focused on the frequencies of the repeated abortions in human females. "In other parts of world, people have studied rates of minisattellite mutations, mitochondrial mutations in the populations exposed to radiations due to industrial accidents or nuclear bombings," said Premi. "On the contrary, we have analysed the single chromosome Y in a much greater detail both at somatic and germ line levels. To our information no one in the world has analysed germ line and somatic cells in the manner we have done."

Premi said that on the basis of the study it has been concluded that the study populations have adapted themselves to the high background radiation. "The (genetic) alterations we recorded were random and did not represent any major Y chromosome-related recombination losses or duplications reported in the literature which has been held responsible for the infertility."

References
Premi, S. et al. Unique signatures of natural background radiation on human Y chromosomes from Kerala, India. [journal]PLoS ONE[/journal] 4, e4541. 2009)

Granite slabs and radioactivity

What's lurking in your granite countertop?

By KATE MURPHY
THE NEW YORK TIMES

August 03, 2008

Shortly before Dr. Lynn Sugarman of Teaneck, N.J., bought her summer home in Lake George, N.Y., two years ago, a routine inspection revealed it had elevated levels of radon, a radioactive gas that can cause lung cancer. So she called a radon measurement and mitigation technician to find the source. “He went from room to room,” says Sugarman, a pediatrician. But he stopped in his tracks in the kitchen, which had richly grained cream, brown and burgundy granite countertops. His Geiger counter indicated that the granite was emitting radiation at levels 10 times higher than those he had measured elsewhere in the house.

When the technician told her to keep her daughter several feet from the countertops just to be safe, she says, “I had them ripped out that very day,” and sent to the state Department of Health for analysis. The granite, it turned out, contained high levels of uranium, which is not only radioactive but releases radon gas as it decays. “The health risk to me and my family was probably small,” Sugarman says, “but I felt it was an unnecessary risk.”

As the popularity of granite countertops has grown in the last decade — demand for them has increased tenfold, according to the Marble Institute of America, a trade group representing granite fabricators — so have the types of granite available. For example, one source, Graniteland (graniteland.com) offers more than 900 kinds of granite from 63 countries. And with increased sales volume and variety, there have been more reports of “hot” or potentially hazardous countertops, particularly among the more exotic and striated varieties from Brazil and Namibia.

“It’s not that all granite is dangerous,” says Stanley Liebert, the quality assurance director at CMT Laboratories in Clifton Park, N.Y., who took radiation measurements at Sugarman’s house.

DUELING OPINIONS

Allegations that granite countertops may emit dangerous levels of radon and radiation have been raised periodically over the past decade, mostly by makers and distributors of competing countertop materials. The Marble Institute of America has said such claims are “ludicrous” because although granite is known to contain uranium and other radioactive materials like thorium and potassium, the amounts in countertops are not enough to pose a health threat.
Indeed, health physicists and radiation experts agree that most granite countertops emit radiation and radon at extremely low levels. They say these emissions are insignificant compared with so-called background radiation that is constantly raining down from outer space or seeping up from the earth’s crust, not to mention emanating from manmade sources like X-rays, luminous watches and smoke detectors.

But with increasing regularity in recent months, the Environmental Protection Agency has been receiving calls from radon inspectors as well as from concerned homeowners about granite countertops with radiation measurements several times above background levels. “We’ve been hearing from people all over the country concerned about high readings,” says Lou Witt, a program analyst with the agency’s Indoor Environments Division.

In June, Suzanne Zick, who lives in Magnolia, Texas, a small town northwest of Houston, called the EPA and her state’s health department to find out what she should do about the salmon-colored granite she had installed in her foyer a year and a half ago. A geology instructor at a community college, she realized belatedly that it could contain radioactive material and had it tested. The technician sent her a report indicating that the granite was emitting low to moderately high levels of both radon and radiation, depending on where along the stone the measurement was taken.

TAKING ACTION

The EPA recommends taking action if radon gas levels in the home exceeds 4 picocuries per liter of air (a measure of radioactive emission); about the same risk for cancer as smoking a half a pack of cigarettes per day. In Sugarman’s kitchen, the readings were 100 picocuries per liter. In her basement, where radon readings are expected to be higher because the gas usually seeps into homes from decaying uranium underground, the readings were 6 picocuries per liter.
The average person is subjected to radiation from natural and manmade sources at an annual level of 360 millirem (a measure of energy absorbed by the body), according to government agencies like the EPA and the Nuclear Regulatory Commission. The limit of additional exposure set by the commission for people living near nuclear reactors is 100 millirem per year. To put this in perspective, passengers get 3 millirem of cosmic radiation on a flight from New York to Los Angeles.

A “hot” granite countertop like Sugarman’s might add a fraction of a millirem per hour and that is if you were a few inches from it or touching it the entire time. Nevertheless, Witt says, “There is no known safe level of radon or radiation.” Moreover, he says, scientists agree that “any exposure increases your health risk.” A granite countertop that emits an extremely high level of radiation, as a small number of commercially available samples have in recent tests, could conceivably expose body parts that were in close proximity to it for two hours a day to a localized dose of 100 millirem over just a few months. David J. Brenner, director of the Center for Radiological Research at Columbia University in New York, says the cancer risk from granite countertops, even those emitting radiation above background levels, is “on the order of one in a million.” Being struck by lightning is more likely. Nonetheless, Brenner says, “It makes sense. If you can choose another counter that doesn’t elevate your risk, however slightly, why wouldn’t you?”

Radon is the second leading cause of lung cancer after smoking and is considered especially dangerous to smokers, whose lungs are already compromised. Children and developing fetuses are vulnerable to radiation, which can cause other forms of cancer. Witt says the EPA is not studying health risks associated with granite countertops because of a “lack of resources.”
The Marble Institute of America plans to develop a testing protocol for granite. “We want to reassure the public that their granite countertops are safe,” Jim Hogan, the group’s president, said earlier this month. “We know the vast majority of granites are safe, but there are some new exotic varieties coming in now that we’ve never seen before, and we need to use sound science to evaluate them.”

Research scientists at Rice University in Houston and at the New York state Department of Health are currently conducting studies of granite widely used in kitchen counters. William J. Llope, a professor of physics at Rice, says his preliminary results show that of the 55 samples he has collected from nearby fabricators and wholesalers, all of which emit radiation at higher-than-background levels, a handful have tested at levels 100 times or more above background.
Personal injury lawyers are already advertising on the Web for clients who think they may have been injured by countertops.

As for Sugarman, the contractor of the house she bought in Lake George paid for the removal of her “hot” countertops. She replaced them with another type of granite. “But I had them tested first,” she says.

ARE GRANITES A RADIATION RISK? (by Donald Langmuir, PhD, Professor Emeritus of Geochemistry, Colorado School of Mines)

It is worth noting that the stone industry, whether advertising countertops, building materials or monuments, terms many stones 'granites' that are not true granites to a geologist. A true granite, which is often grey or pink, is chiefly comprised of a potassium aluminum silicate mineral (K-feldspar or potassium feldspar) and quartz (silica or SiO2). Rocks called granites by the industry also include magnesium silicates (e.g. peridotites and serpentines) and a host of other chemically different rock-types, most of which contain much less uranium than does true granite.
As admitted by the author of 'Granite and Radon', there have been no direct measurements of radon release from granite countertops. Model calculations suggested by Dr. Richard Wanty, using a standard, scientifically accepted approach and conservative assumptions, indicate that the radon release from a granite countertop is orders of magnitude below detection by any known analytical method.

EPA standard, which is not to be exceeded in indoor air, is 4 picoCuries per liter of air (4 pCi/L). Eisenbud 1 indicates that the average contributions of radon from various sources to indoor air are 1.5 pCi/L from the soil (under and around the house), 0.01 pCi/L from public water supplies (0.4 pCi/L) from private wells), 0.05 pCi/L from building materials, and 0.2 pCi/L from outdoor air. These values are for the average house which is ventilated such that over one hour the air is changed 0.5 to 1.5 times. The vanishingly small amount of radon in household air that might be released from a granite countertop (0.00000074 pCi/L) as computed below, has been calculated assuming no exchange of indoor and outdoor air, which would further trivialize its significance. Note also that the radon content of outside air is 270,000 times greater than that released by the countertop.

There are certain properties of rocks that can increase their radon emanation efficiency, or in other words increase the release of radon from a given weight of rock. These are rock properties that maximize the exposure of internal or external rock surfaces to water or air, allowing any radon gas to escape. It is argued that such properties, which include rock porosity, fissuring and mylonitization, will increase radon releases. This is probably true, however, a granite with such properties would be too brittle to make into a countertop, and too open to take a polish, and so would not be marketable as a countertop - unless the rock pores were first filled with a chemical sealant. Such sealing would also eliminate any possible radon release problems.

The typical granite countertop in our example will release 7.4 x 10 -7 pCi/L of air. This corresponds to 2.7 x 10 -8 atom decays per second (dps). This represents 0.85 decays per year. In other words, less than one atom of radon is produced by the countertop in one year. This is hardly worth getting excited about.