WILD WEATHER 

UPDATE (1:45 p.m. EDT): The damaged levee in Poplar Bluff, Mo., failed in multiple locations Tuesday, Reuters reports. The dam failures allowed the Black River to flood into sparsely populated areas, with another storm already bearing down on the region. Stay tuned to MNN for more details.

Severe thunderstorms and tornadoes continue to ravage the central U.S. today, hours after they killed at least five people in Arkansas and damaged levees in Missouri. And as that storm now pushes east into the Tennessee Valley, yet another violent system is already brewing in Texas and Arkansas, AccuWeather reports, endangering many of the same areas where tornadoes hit Monday night. It's all part of a wild final week in one of the most tornadic Aprils in recent history: Nearly 300 have been confirmed so far, topping the previous April record of 267 confirmed twisters, set back in 1974. "We've had nothing but tornadoes," one weary Midwesterner tells the New York Times. "I feel like I'm living in the Land of Oz."

At least five people died amid the storms in Arkansas Monday night, the AP reports — three drowning in floodwaters and two killed by what was likely a tornado. Destruction is widespread in Vilonia, Ark., where the path of a suspected tornado stretches three miles wide and 15 miles long. "The town's gone," one Vilonia resident tells the AP. And in the southeast Missouri town of Poplar Bluff, forecasters say the surging Black River is in "imminent danger" of overwhelming saturated levees, potentially inundating hundreds of homes and businesses. Some 1,000 residents were evacuated earlier in the day Monday, but police say the storms struck too quickly for sandbagging to be an option. There was too much area to cover, Police Chief Danny Whitely tells the AP, and it was too dangerous to put emergency workers on the failing levee. Instead, officers went door-to-door asking people to leave; now their hands are tied, especially with another storm system on the horizon. "Basically, all we can do now is wait, just wait," Whitely tells the AP.

As the Times reports, this month's tornado frenzy is a result of air masses from the Arctic and the Gulf of Mexico colliding over the U.S., and while it is extreme and unusual, it's not as apocalyptic as it seems. Historical tornado counts aren't very reliable, since radar and reporting techniques have improved dramatically in recent decades. For example, while 267 tornadoes were reported in April 1974, the actual number may have been closer to 500. "Today we seem to know about every single tree branch knocked down," says National Weather Service meteorologist Greg Carbin. "We have eyes everywhere, and we have radar and satellite. It would be very difficult for a tornado to sneak through unnoticed." Still, he adds, even just one tornado is a big deal. "Any tornado is extreme," Carbin tells the Washington Post. "People want to talk about 'normal tornadoes,' but a tornado is not normal in any sense of the word."

(Sources: ReutersAssociated Press, National Weather Service, AccuWeather, New York Times, Washington Post)

BLAST FROM THE PAST 

Twenty-five years ago this week, the world's worst nuclear disaster kicked off in Ukraine, triggered by an explosion at the Chernobyl nuclear plant that harmed or killed thousands of people and left a 19-mile radius uninhabitable. The anniversary comes at a coincidental crossroads for nuclear power, as Japan struggles with its own drawn-out nuclear crisis, which is once again forcing the world to rethink the wisdom of splitting atoms for energy. And as the Guardian reports, scientists now warn that future wildfires could start a new catastrophe at Chernobyl, pumping its loose radioactive particles into the atmosphere — and illustrating how nuclear disasters can linger even long after they've been laid to rest.

A consortium of Ukrainian and international experts are calling for a $13.5 million program to prevent such wildfires in Chernobyl's exclusion zone, which has already endured more than 1,000 fires in the last two decades. If a high-intensity "crown" fire grows large enough within the exclusion zone, the consortium warns, it could send radionuclides streaming over a wide area, possibly even cascading as far away as the U.K. A $6.5 million plan for "basic emergency measures" has already been approved by scientists in Ukraine, Yale University and the U.N., partly to protect the firefighters who must risk radiation exposure to prevent Chernobyl-area fires from growing too large. Many of the firefighters lack monitoring devices as well as adequate firefighting equipment, the Guardian reports. "I know when I am fighting a fire on radioactively contaminated ground — you get the heat just like an ordinary fire, but you get a tingling sensation too, like pins jumping all over your body," says local firefighter Jakov Kalynik. "I don't know how bad it is for me, there's no medical testing afterwards, we just go and wash."

Last month, one state forestry firm in Ukraine was reportedly "low on fuel," and was forced to use a horse and cart to bring water to a wildfire. The longer such wildfires are able to burn uncontrollably near Chernobyl, the consortium says, the higher the risk of reawakening the radioactive disaster from 25 years ago: "Strontium-90, plutonium and americium-241 are all extremely susceptible to upward atmospheric migration and dispersal via heat from fires. They create problems for firefighters and others who breathe them in. Radioactive smoke landing on crops ... even 150 km or more from the fire can create such concentrations of radiation in food it will be harmful to eat. Our studies, together with Yale University, have shown it is imperative we take measures to control the radiation [in] Chernobyl's forests."

(Sources: BBC News, Guardian)

SYNCHRONIZED SWIMMING 

Ants are famous for their feats of collective intelligence, with some scientists even comparing individual ants to neurons in a human brain. And as a new study by researchers at the Georgia Institute of Technology reveals, fire ants can even use their strength in numbers to assemble a "super-organism" that's virtually impervious to drowning, capable of floating on water for months on end.

Fire ants are native to Brazil, and were only introduced to the U.S. via Alabama shipping ports in the 1930s. Since flooding is a frequent problem back in their home country, they've developed an amazing survival technique when they find themselves in over their heads: Thousands of the insects lock their bodies together, linking legs and jaws, to form a living raft that's surprisingly air-tight. "Water does not penetrate the raft," lead author and Georgia Tech mechanical engineer Nathan Mlot tells the Washington Post. "If water can't come into contact with one ant, or the next, or the next, air can't get through." Biologists have long observed this phenomenon in nature, but until now, engineers have never examined how exactly it works. 

The secret, it turns out, is that each ant mildly repels water thanks to the bumpy and bristly surface of its exoskeleton. This is only enough to briefly save an individual ant from drowning, but that thin layer of air around its body can become a formidable life preserver when combined with other ants' air pockets. Fire ants in a raft cling so closely together that their adjacent air bubbles merge, eventually creating a waterproof buffer that protects the entire raft. Not only is this an impressive survival technique, but it could also inspire new methods of "swarm intelligence" in miniature robots, the Georgia Tech researchers say. "A simple robot is easier to program than a mega-smart one," Mlot says.

(Sources: Washington Post, Wired, Georgia Institute of Technology)

FIREPROOF FOOD 

A new study of pet dogs has found levels of flame retardants in their blood five to 10 times higher than in humans, e! Science News reports, raising concerns about both canine and human exposure to the widespread chemicals. Based on lab tests of the dogs' blood and of their food, the researchers at Indiana University believe the animals are at least partly being exposed via contamination of dog food, which likely takes place during the extensive processing the food undergoes.

The study focuses on polybrominated diphenyl ethers, or PBDEs, which have long been used as flame retardants in furniture, electronics equipment, and various other industrial and consumer products for safety reasons. The compounds are known to migrate out of the products and into the surrounding environment, where they can "bioaccumulate" in body tissues. PBDE mixtures with less brominated compounds are considered more dangerous than other types, and are listed as a "possible human carcinogen" by the U.S. Agency for Toxic Substances and Disease Registry. While the full range of PBDEs' health effects aren't known, they have been linked to thyroid hormone disruption, permanent learning and memory impairment, behavioral changes, hearing problems, delayed puberty, and birth defects, in addition to liver tumors in rats. The U.S. and the European Union have both phased out the less brominated varieties of PBDEs, but they remain in the environment; more brominated types are still used in the U.S., but are scheduled to be phased out by 2013.

The 17 pet dogs examined for the study all lived primarily indoors, and all ate diets consisting of dry dog food. The average level of PBDEs in the dogs' blood was 2 nanograms per gram, about five to 10 times higher than levels found in humans, while samples of their dog food showed levels around 1 nanogram per gram. That's much higher than PBDE concentrations in human food, and suggests PBDE in dog food comes from processing rather than from the food sources themselves, the researchers say. And while that's a serious concern, the situation is even worse for house cats — a previous study in 2007 found that PBDE levels in feline blood were 20 to 100 times higher than those found in humans. 

(Sources: e! Science News, Indiana UniversityATSDR, Environmental Working Group)

THIS DAY IN HISTORY

Frederick Law Olmstead is born, the "world's deadliest tornado" strikes, and more.

Russell McLendon

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Photo (tornado damage in St. Louis, Mo., on April 23): ZUMA Press

Photo (sarcophagus over the destroyed Chernobyl reactor): ZUMA Press

Photo (fire ant with droplet on its head): Nathan Mlot/Georgia Tech

Photo (puppy eating bowl of dog food): Jupiter Images

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