Scientists report that radiation from the crippled Daiichi Nuclear Power Plant in Japan will reach the west coast of the U.S. sometime in April. Creative Commons

On the third anniversary of the Fukushima disaster, scientists report that radiation from the crippled Daiichi reactor in Japan will reach the West Coast of the U.S. sometime next month. But far from painting a nightmare scenario in which swimmers will sprout third arms and ordinary fish will become monsters, scientists say the level of radiation on its way to U.S. shores is very low and won’t pose a threat to humans or the environment.

In the same breath, researchers encourage increased monitoring and more testing of the waters off the coasts of California, Oregon and Washington, as the federal government currently does not sample Pacific Coast water for signs of radiation, Time reports.

That has led to some scientists and citizens taking the matter into their own hands. State park rangers in Oregon, for instance, take quarterly ocean water samples at three locations along the coast. They analyze the water for traces of cesium 137 and iodine 131, both of which already exist in the ocean at negligible levels.

In California, marine biologists already sample seawater around nuclear power plants to see if they’re affecting the environment. The results of those tests are all below the minimum detectable level, according to USA Today.

Washington does not test its waters for radiation.

Scientists say the radiation from Fukushima will reach Washington first and then move south, following the North Pacific currents. Already, trace amounts of radiation from the 2011 meltdown at Fukushima have been recorded in water samples collected off the coast of Vancouver, British Columbia. The isotope detected in Canada was cesium 134, radiation researchers will be looking for it along the west coast of the U.S.

The big question is, then: Are we safe? While current models predict that radiation coming from Japan will be so diluted by the time it reaches the U.S. as to be almost insignificant, Ken Buesseler, a chemical oceanographer in Massachusetts, isn’t flashing the green light just yet. Buesseler presented research on the issue at last week’s American Geophysical Union's Ocean Sciences Section in Hawaii.

"I'm not trying to be alarmist," Buesseler said, according to USA Today. "We can make predictions, we can do models. But unless you have results, how will we know it's safe?"

The answer will partly depend on the type of radioactive isotope that reaches U.S. shores. Cesium isotopes, for instance, are among the most dangerous radionuclides because they emit flesh-penetrating gamma rays, Bloomberg Businessweek notes.

Radioactive isotopes decay over time, but their half-lives, meaning the time it takes for half the isotope to break down into a more stable material, can be pretty long. Cesium 134, for example, has a half-life of two years.

Since the 2011 Fukushima nuclear disaster, scientists say as many as 20 trillion becquerels of cesium 137, 10 trillion becquerels of strontium 90 and 40 trillion becquerels of tritium were released into the Pacific Ocean.

Let’s not forget, however, that our oceans already contain vast amounts of radiation from nuclear power plants across the globe. Plants routinely pump radioactive water into our oceans, albeit less dangerous isotopes than cesium.

“There’s a point to be made that we live in a radioactive world and the ocean just has radioactive isotopes in it,” Buesseler told Bloomberg in February. “People have a limited knowledge of radioactivity.”

Scientists have long debated the health risks of radioactive material in the environment. We know that exposure to large amounts of radioactivity can cause nausea, vomiting, hair loss and hemorrhaging. More serious cases include damage to the central nervous system and death.

“There’s been a lot of confusion between the levels of radiation that have been detected and levels that are harmful,” Chad Nelsen, environmental director at the San Clemente-based Surfrider Foundation, told U-T San Diego last month regarding Fukushima radiation reaching the U.S. “So far, there have been no levels that are a real concern.”