Sae Ochi should know better, and she knows she should know better. As the director of internal medicine at Soma Central Hospital, just 30 miles from the Fukushima-Daiichi nuclear power plant that melted down after a tsunami in 2011, part of her job is to monitor local radiation exposure levels. She has screened thousands of people, and only a few showed levels high enough for her most sensitive instruments to detect. She eats locally grown food sold at the supermarket and even the occasional wild berry, which probably does contain a bit of radiation. “When I go hiking, I will eat a berry or two, because it’s only a tiny amount and it looks so delicious,” Ochi says. But then she adds a caveat: “That’s because I have no children.” If Ochi were a parent, she says, she wouldn’t do it—even though she knows local radiation levels are negligible. “All mothers,” she says, “try to take zero risks.”

Researchers have accumulated and analyzed reams of data about food from Fukushima and the Pacific Ocean. A protective system stopped even potentially contaminated food from getting to the public. Extensive decontamination, monitoring, and regulations have made food from around Fukushima perfectly safe. Yet fear persists.

Between 2011 and 2014, an ambitious government program checked the radiation levels of nearly every kind of food produced in Fukushima. The program sampled milk at dairy centers once every two weeks, and tested fruits, vegetables, and tea leaves at their farms of origin, three days before they were scheduled to ship. In total, the program took nearly 900,000 samples. “When I saw this number, I was stunned,” says Georg Steinhauser, a chemist at Colorado State University. “This hasn’t been done in the history of mankind.” Steinhauser was the first researcher to dive into the mounds of data to try to figure out how radiation levels changed over time. His team focused on one leading indicator: cesium 137, one of the longest-lived radioactive byproducts of a meltdown. They dug into nearly 140,000 samples from the first year of the monitoring program.

For the vast majority of the samples, radiation levels were below Japan’s limits, the strictest in the world. The government’s standards limited radiation levels in food to just one-sixth the levels permissible in food imported to Europe, for example—and to just 1/100,000 the levels produced by naturally occurring radioactive isotopes in a human being. Steinhauser’s team found that just a year after the Fukushima meltdown, radiation in only 3.3 percent of the food exceeded Japan’s limits. The numbers rose to 4.0 percent in the second year, but eventually dropped to 0.6 percent by the end of August 2014. The food, it appears, is getting safer over time. Virtually no item above Japan’s limit—no piece of fruit, meat, or anything else—got into any supermarket.

After the Fukushima meltdown, government teams stripped the outer bark off of trees in the area, and removed the top several inches of soil. That kind of decontamination is specifically aimed at cesium, which falls out of the air like dust. “It’s transported by wind and clouds,” says Kathy Higley, a radioecologist at Oregon State University who studies decontamination. “Then it washes out, or it contacts and sticks to surfaces.” If it falls on plants that animals then eat, the animals get contaminated, too. But it turns out that cesium actually has a tough time getting into plants. They absorb it because chemically cesium looks a lot like the essential nutrient potassium, but Fukushima soil is already potassium-rich—and fertilized with even more. So the crops tended to take up the nutrient instead of the radioactive imposter. And cesium-137 tended to stick to the clay in the soil, too.

Of course, that’s just food produced in Fukushima. Some radiation did get into the ocean, and researchers detected radiation in fish along the coasts of Oregon and Washington—but in negligible amounts. “The fact that you can see it doesn’t mean that it’s a hazard,” says Delvan Neville, a graduate student at Oregon State University who studies radiation levels in albacore tuna. The enormous size of the Pacific dilutes radioactive isotopes until they're harmless. In fact, only one percent of the radioactivity in the ocean comes from Fukushima, Steinhauser says. The rest? Cold War-era nuclear weapons tests. “Fukushima has not made a big impact on overall radioactivity, believe it or not,” he says.

The problem is, a lot of people still don’t believe it. “People are really afraid that the Pacific is so contaminated that you can’t eat any fish anymore,” Steinhauser says. “It’s not true, and I find it very difficult. This is one of the biggest challenges in my work.”

Even the converted feel torn. Ochi, for example, knows it's important to dispel irrational fears, yet she sympathizes with the fearful. “Maybe there is nothing that is perfectly correct or perfectly wrong,” she says. “The most important thing is not to blame people who make a different decision.” But when those decisions are clearly wrong, such as extreme cases in which mothers feed their children McDonald’s because they think it’s safer, her rational side emerges. “Some people try too hard to avoid radiation, and bring in other health risks,” she says. It's a tug-of-war between fear and science, a conflict that remains a challenge in Fukushima.