After discovering dangerous levels of radiation in the tap water in Tokyo and surrounding areas, Japanese officials have warned parents to prevent their infants from drinking it — triggering a run on bottled water. Radioactive fallout from the struggling nuclear reactors in Fukushima prefecture has also prompted restrictions on agricultural products in Japan and several other countries. How dangerous are the contamination risks for Japan's reeling population? Here, a brief guide:

1. Tap water
Tokyo's water officials said Wednesday that they'd found dangerous levels of radioactive iodine-131 — 210 becquerels per liter, to be precise — in the city's drinking water. Although levels up to 300 becquerels per liter are considered safe for adult consumption, anything over 100 becquerels is a risk for babies. Officials pledged to deliver bottled water to the 80,000 homes with kids under age 1, but people in Tokyo and surrounding areas didn't wait around, emptying store shelves of bottled water. Though iodine levels had dipped back to 79 becquerels by Thursday, city officials said that "continued monitoring of the situation is essential."

2. Vegetables
Dangerous levels of radioactive contamination were found in 11 kinds of vegetables in Fukushima and neighboring Ibaraki prefecture. The Japanese government ordered those two prefectures, plus two more, to halt all shipments of affected vegetables, and restricted sales from six other surrounding prefectures. U.S. health experts agreed that the recorded radiation levels in these green leafy veggies don't pose much of a health risk, but a Japanese official still warned that people should "refrain from eating them as much as possible, as a precaution."

3. Milk
Dairy products are perhaps the biggest health concern, especially for Japan's children. In the U.S., milk that was contaminated by the 1986 Chernobyl nuclear plant disaster — cows ate grass blanketed in radiation, and kids drank the milk — is blamed for at least 6,000 cases of thyroid cancer so far. The U.S., Singapore, and Hong Kong have banned milk products from the four worst-hit prefectures, and Japan has suspended raw milk shipments from Fukushima and Ibaraki. That's a bit of an overreaction, says U.S. health physicist Peter Caracappa. He estimates you'd have to drink 58,000 glasses of tainted Japanese milk to raise your lifetime cancer risk by 4 percent.

4. Seafood
The high levels of radiation in the seawater around the Fukushima reactors are a big threat to Japan's multibillion-dollar seafood industry, and several Asian countries have already banned Japanese seafood. Japan insists that no fish are being caught anywhere near the reactors, and that they're diligently testing seafood, and have found no dangerous levels of radiation. A U.S. sushi chain's refusal to buy Japanese fish is an "overreaction," says Edward Flattau at The Huffington Post. But radiation could still increase as it moves up the food chain, from small fish to bigger ones, "insidiously concentrating at the top where we reside."

Sources: New York Times, Reuters, The National, The Daily Yomiuri, CNN, VPR, Bloomberg, Huffington Post