Stripping Down Science (9 page)

This issue was the subject of a recent large study involving 30,000 initially healthy subjects who were given either daily aspirin or a placebo over an eight-year follow-up period by Edinburgh researcher Gerry Fowkes.
²⁶
He found no difference in subsequent heart attack rates between the people who took aspirin every day and those who didn't. But what he did see were twice as many ‘major bleeds' amongst the patients on aspirin compared with those not taking it. So, in the absence of a major heart disease risk, aspirin might do more harm than good.

Blood clotting aside, two other important health areas where aspirin can also make an impact are prevention of some cancers and Alzheimer's disease. In the latter case, researchers think that aspirin damps down inflammation in the nervous system, thereby reducing the levels of a protein called beta-amyloid that can otherwise build up in the brain, damage nerve cells and lead to dementia.

The same anti-inflammatory effect is also likely to be behind the observed reduction in breast, bowel and lung cancer risk in people who use aspirin for long periods, and researchers have also recently found that taking the drug can cut the risk of the cancers coming back in people with previously-treated malignancies. Andrew Chan, from Harvard in the US,
²⁷
recruited just under 1300 newly diagnosed bowel cancer patients, 549 of whom took regular aspirin. He compared how long these patients survived against 719 individuals with the same diagnosis who did not take regular aspirin.

The aspirin users, he found, had an overall reduction in mortality rate of 21%, and a 29% drop in their mortality from bowel cancer. The benefit was similar regardless of how advanced an individual's cancer had been when they were first diagnosed or how their disease was managed, suggesting that aspirin might be an excellent adjunct to existing bowel cancer therapies.

Why does it work? Unfortunately, this was an observational study, so the team do not know the precise mechanism by which aspirin achieves this significant life-prolonging effect, but interestingly they did find that the patients who enjoyed the most gains from the therapy had tumours that over-expressed a gene for another form of cyclooxygenase (COX) called COX-2. This enzyme also produces inflammatory prostaglandins, so perhaps by preventing their formation, aspirin reduces within tissues the oxidative stress that can damage DNA and encourage cells to become cancerous.

Most people believe that everything alive on earth today gets its energy, one way or another, from the sun. The dogma goes that plants capture sunlight and turn it into chemical energy and then other organisms feed on the plants, and ultimately on each other, funnelling the energy up the food chain until it arrives on our dinner plates. Indeed, even bacteria living in the scalding conditions of mineral-rich hydrothermal vents on the ocean floor still rely on the by-products of other organisms elsewhere on earth for their survival.

But now a trickle of water in a goldmine three kilometres beneath the earth's surface has revealed a population of bugs powered not by the sun but by radioactivity. And the finding therefore fuels speculation that life could eke out a similar existence deep underground on planets elsewhere in the solar system and beyond.

The findings have been made by US researcher Lisa Pratt and her colleagues.
²⁸
The team heard
about a deep fracture that had been opened up by drilling in a South African goldmine not far from Johannesburg. The team visited the site and collected samples of water that were pouring out of the fracture site. When they analysed the water, they found that it had a very ancient chemical fingerprint. In other words, it had been sealed off from the rest of the world for at least three million years and possibly for as long as 25 million years.

Even more exciting was the discovery that the water also contained the DNA profiles of a vast number of bacterial species. One strain of bacterium stood out because it was so abundant. It was a relative of the bugs known as
Fermicutes
, which are found at deep-sea hydrothermal vents. These bacteria can use hydrogen and sulphur compounds as an energy source and, through their growth, feed and sustain other types of microbes.

But where were these fracture-dwelling bugs getting the hydrogen and sulphur with which to sustain themselves in this underground pocket of water for the last 25 million years? The unlikely answer is natural radiation. In the mine, the surrounding rocks contain uranium.
The radioactivity it produces splits apart water molecules, producing highly reactive chemicals called free radicals. These react with minerals, such as pyrites (fool's gold) in the surrounding rocks, to produce hydrogen and sulphur compounds that the bacteria can use.

So, apart from shattering the myth that all life on earth depends upon the sun, these new findings suggest that life could well exist along the same lines elsewhere in space. And even if life as we know it became extinct on a planet where organisms once flourished, it's possible that somewhere beneath the surface there may well be a colony of thriving bacteria, fuelled by a nuclear reaction …

Apart from naturally radioactive rocks, another source of radiation is the stuff we churn out to fuel nuclear power stations, reactors aboard boats and submarines, and even the arms industry. Thankfully, it's a simple task to deal with the radioactive waste that's left over, isn't it? We can just turn it into concrete and bury it, can't we? ‘Wrong!' says a leading Cambridge scientist.
²⁹

While nuclear power, being carbon-neutral, may seem like a safe haven in the present climate-change storm, it brings with it a unique problem that, until now, has gone largely unappreciated. That is, what to do with the leftovers. Of course everyone knows that nuclear power stations produce a significant amount of high-level radioactive waste like uranium and plutonium: Britain has 470,000 cubic metres of the stuff loitering in temporary storage and the US is sitting on 50,000 tonnes of ‘hot rods'.

Until recently, we thought that getting rid of it was quite trivial in the grand scheme of things – you just need to encase it in something hard, bury it, and wait long enough for the radioactivity to die away. Admittedly, in the case of plutonium, that does mean waiting at least a quarter of a million years, but what's that between friends?! But therein lies the problem, because nuclear scientists had planned to mix waste plutonium and uranium with a synthetic mineral and fire it to bake the radioactive equivalent of bone china. The resulting ceramic, containing the radioactive atoms safely sequestered inside the crystal structure, could be buried without any risk of the material escaping.

Indeed, the idea has proved sufficiently popular with the US nuclear industry that they've already sunk US$7 billion into a prospective burial site in the Nevada desert called Yucca Mountain. But if they go ahead and finish the job, they could land themselves with a much bigger hole in their pockets than the one made by the anticipated US$100-billion price tag. This is because it's a myth that these ceramics are stable. In fact, research now suggests that they don't even last 1000 years, let alone the required 250,000.

This worrying result came to light when Cambridge earth scientist Dr Ian Farnan and his team developed a new way to see inside 25-year-old samples of these ceramic crystals that contain radioactive materials. What they saw made alarming viewing, because it showed that the crystals were falling to pieces, and much more quickly than scientists had expected.

When plutonium or uranium atoms undergo radioactive decay they spit out an alpha particle, which consists of two protons and two neutrons stuck together. This travels through the crystal and can pull electrons off some of the nearby atoms, but the damage is relatively minor. Far more serious, and what hadn't previously been appreciated, is what happens to the original uranium or plutonium nucleus. When this ejects the alpha particle, it recoils, like the kick of a gun, which sends it careering into other atoms in the crystal, knocking about 5000 of them off kilter at a time and destroying the integrity of the material.

The net result is that after just a few hundred years in storage, the proposed materials would be riddled with cracks and leakier than the
Titanic
. And after just 1500 years, and a far cry from the
required 250,000, the material would have fallen apart completely.

However, every cloud has a silver lining, even if it is slightly radioactive in this case. As Ian Farnan points out, it's better to know now than later, when the stuff might already have ended up in the ground. Thankfully, the technique he's developed can be used to identify more robust mineral recipes that can take a heavier radioactive beating, or even repair themselves so that they can go the distance without breaking down. Let's hope so.

Simpsons
fans will know only too well the opening sequence of the cartoon in which Homer discovers, during his commute, that he's taken some of his work home with him – in the form of a radioactive fuel rod from the nuclear power plant. Unsurprisingly, the lump of material he subsequently throws out of the car window is glowing a ghostly green colour. But basking in that radioactive light is a luminous myth of atomic-powered proportions, because most radioactive substances don't really glow at all, let alone light up green.

The basis of this belief stems from the late 1800s and early 1900s when the Polish pioneer of radioactivity Marie Curie, working in Paris with her husband Pierre, discovered the element radium, which they named after the Latin word
radius
, meaning a ray. Once they began to isolate the metal in reasonable amounts, the Curies noticed that it appeared to emit an attractive blue glow. According to biographer Barbara Goldsmith, Marie described the ethereal glow
as ‘fairy-like' and kept a jar of pure radium salts beside her bed, where it presumably functioned as an attractive, albeit potentially lethal, radioactive nightlight!

However, contrary to popular belief, the glow from the tube wasn't the radiation per se, but rather the effect it was having on other chemicals that were also present. This is because as radium decays, it spits out energetic particles and waves including alpha particles, beta particles and gamma rays. When these pass through a material they knock negatively charged electrons off some of the atoms, triggering a process called ionisation. Most of the electrons liberated like this subsequently snap back onto their parent atoms, but first they have to surrender the extra energy they gained to start with. To do this they pump out light, some of which is in the visible part of the spectrum, meaning we can see it.

Chemicals that behave like this, by emitting visible light when they are excited, are referred to as phosphors. As it turns out, Marie Curie's bedside sample would have contained the radium compounds radium bromide, radium fluoride and radium chloride, which are themselves phosphorescent. So when they were hit by the
radioactive emissions of the radium itself, they glowed, producing the blue light she found so soothing.