Governments are stepping up scrutiny of domestic food and water supplies as radioactive material spreads from the country’s Fukushima Daiichi nuclear power plant.

The U.S. Environmental Protection Agency announced Wednesday that it was increasing its nationwide monitoring of milk, precipitation, drinking water and other potential sources of nuclear exposure.

So far, a sample of milk from Spokane, WA showed minimal amount of radiation, although still 5,000 times lower than the level at which the U.S. Food and Drug Administration (FDA) requires intervention.

“These types of findings are to be expected in the coming days and are far below levels of public health concern, including for infants and children,” said the EPA and FDA in a joint statement.

Patricia Hansen, an FDA senior scientist, noted that, “Radiation is all around us in our daily lives, and these findings are a miniscule amount compared to what people experience every day. For example, a person would be exposed to low levels of radiation on a round trip cross country flight, watching television, and even from construction materials.”

In Japan, on the other hand, radiation levels found in some foods in areas surrounding the damaged power plant have reached harmful levels.

The Japanese government has banned the distribution of raw milk and certain vegetables in Fukushima and 3 surrounding prefectures after tests detected harmful levels of radioactivity in these foods.

Two nuclear byproducts, iodine-131 and cesium-137, were found at varying levels in products grown in these regions, including spinach, broccoli and kakina, a local vegetable.

Data analysis of iodine levels in Japanese dairy and fresh produce from March 16-18 showed that the presence of radioactive iodine in food over that period was 5 times the acceptable level, according the FDA’s Import Alert on Japanese foods.

Since that time, tests have shown somewhat lower levels of radiation in other Japanese vegetables.

The government’s safety limit for iodine-131 is 2,000 becquerels per kilogram. For cesium-137, anything above 500 Bq/kg is considered dangerous.

This week, tests on wasabi from Fukushima showed an iodine-131 reading of 2500 Bq/kg, which surpasses the allowed concentration, and 340 Bq/kg of cesium, according to NPR.

And even among vegetables with levels of radiation not considered hazardous by the Japanese government, iodine-131 often succeeded 170Bg/kg, the level at which the U.S. Food and Drug Administration (FDA) recommends taking preventative measures.

Radioactive iodine does not last long in food. It has a half-life of eight days, meaning that it will decay to half its original amount in that time. However, “there is risk to human health if radioactive iodine in food is absorbed into the human body,” according to the FDA.

According to the World Health Organization (WHO), food containing iodine-131 must be eaten over a prolonged period of time in order for it to cause risks to humans. The element accumulates in the thyroid, and can increase the riskof thyroid cancer, especially in children.

Cesium-137 lingers much longer, with a half-life of 30 years. However, levels of radioactive cesium currently remain low relative to those of iodine in Japanese foods.

The FDA has already halted imports milk, fruits and vegetable from the Japanese prefectures of Fukushima, Gunma, Ibaraki and Tochigi, and is screening other foods imported from Japan, including seafood.  Food from Japan accounts for less than 4 percent of all U.S. imports.