Japanese authorities are trying to prevent total meltdown at three nuclear reactors that were damaged in Friday’s tsunami. Engineers are flooding the reactors to cool them down, then venting the radioactive steam to prevent a dangerous build-up in pressure. Thousands have been evacuated, and helicopters have detected radioactive particles 60 miles from the reactors. How can the evacuees tell if they’ve been exposed to dangerous levels of radiation?

With a blood test. Nuclear plant workers, radiologists, and rescue workers can wear badges or special rings that tell them how much radiation is in their environment. Post hoc measurement is tougher, though. Public health workers may pass a device over the patient’s clothing. The air enters an oxygen- or argon-filled chamber, and the machine detects reactions between the gas and radioactive particles. Another option is to take a swab of the patient’s nose and mouth and perform a similar experiment. If either of these methods uncover radiation exposure, doctors then draw blood. Absorption of more than 500 millisieverts of radiation can depress white blood cell levels.

At this time, it doesn’t look like anyone in Japan has taken in this much radiation. The highest reported absorption so far is just 106 msv. To put that into perspective, workers at the Chernobyl plant absorbed more than 5,000 msv, and those were the survivors. Even 500 msv is fairly benign. White blood cell counts typically rebound within a couple of days, and the patient’s increased lifetime risk of cancer is barely worth mentioning. The average American has a one-in-two chance of developing some form of cancer. One-time exposure to 500 msv raises those odds to about one-in-1.9999.

On the off chance that an unfortunate nuclear plant worker shows signs of significant radiation exposure, treatment would depend on the type of radioactive particle involved. Radioactive cesium can be treated with a chelating agent, a chemical that binds to the particle and ushers it out of the body via urine. Those who inhale a dose of radioactive iodine aren’t as lucky. While it can be treated prophylactically with potassium iodide tablets, there’s no effective remedy after the exposure. The victim has to wait for his body to process the contaminant.

Bonus Explainer: When the evacuated families are allowed to go home, will they have to throw away their clothes and furniture?

Not if their windows were shut. A well-constructed home provides a very effective barrier to a radiation cloud. If one passed over your home today, and your windows and doors remained closed, the increase in radiation levels inside wouldn’t impact your health. But anyone who decided to throw open the shutters during the incident should have a professional check their interior for exposure. If serious penetration has occurred, decontamination (PDF) can include junking clothing and upholstered furniture, washing or sanding the walls, pulling up floorboards, and repainting with a special formula to seal off the remaining radioactive particles. Severely contaminated houses are condemned.

Exteriors are a different matter. There’s a pretty good chance that homes in the immediate vicinity of the plant have a layer of radioactive material on their rooftops. It’s better for residents to let the rain wash it away than to venture up there with a garden hose, though.

Bonus Bonus Explainer: Setting aside the nuclear issues, there seems to be an incredible amount of rubble lying around Japan. What will they do with all that debris?

Recycle or burn as much as possible, and landfill what they have to. Even in the best of times, waste management is challenging in Japan. The country has 10 times the population density of the United States and a dire shortage of landfill space. Local governments have issued a dizzying set of instructions to help residents determine what’s bound for the incinerator—Japan burns more than 80 percent of its trash—or the recycling plant, and what is worthy of their precious dumps. It’s not yet clear whether clean-up crews will follow these same principles, or if the government will simply the rules to expedite the clean up. In the United States, states issue debris management plans to address disposal concerns in the wake of a catastrophe.

Figuring out what to do with detritus from a natural disaster is tough even in the United States, which has plenty of room for trash. Hurricane Katrina generated more than 100 million cubic yards (PDF) of debris. State and local governments are still chipping, composting, and burning their way through downed plant matter. They were able to recycle a fair amount of construction debris, metals, and electronic devices, although some of it was too difficult to separate from hazardous and otherwise non-recyclable materials. Lax regulation of construction debris landfills, which normally don’t receive that much volume, became controversial. Several contractors were caught dumping huge amounts of trash in abandoned lots.

Got a question about today’s news? Ask the Explainer.

Explainer thanks Kelly Classic of the Health Physics Society.