Milk and meat can become contaminated when animals eat grass and other plants… (Everett Kennedy Brown /…)
Japan halted some food shipments Monday as officials from the World Health Organization warned that radioactive milk, spinach and other items posed a greater health threat than radioactive materials in the air. Tainted agricultural products turned up over the weekend, with some exceeding government standards for allowable radiation levels.
Here's some information on radiation and food safety:
How does food become tainted by radiation?
Plants can become poisoned when radioactive material enters the soil and is taken up by root systems. Radioactive particles in the air can also settle on food while it is growing.
Photos: Japan grapples with crisis
Milk and meat can become contaminated when animals eat grass and other plants that are radioactive. Radioactivity cannot contaminate food that is packaged or sealed, according to the U.S. Food and Drug Administration.
Does radioactive food look different?
No, it will not appear spoiled, the FDA says.
Why is it dangerous?
The radioactive substances are absorbed through the gut, and then enter the bloodstream and travel to various tissues. Iodine-131 is most likely to migrate to the thyroid gland, where it can increase the risk of thyroid cancer. Other types of radioactive materials, such as cesium, tend to migrate to bones and be stored there, said Dr. Daniel Zurosky, director of radiation safety at the University of South Carolina School of Medicine.
How severe is the risk?
It depends on the amount and type of radioactive substances. For instance, cesium is more dangerous than iodine because it takes longer to decay.
Absorbing radioactivity from food could increase the risk of certain cancers later in life. Children are more vulnerable than adults because they are still growing and absorb more contamination, pound for pound, compared with adults.
Can you still eat the food?
Plants that have only surface contamination can be washed and eaten. Radioactive material that entered through the root system cannot be removed. It's prudent to discard any questionable food and avoid eating produce, meat, milk, fish and mushrooms from contaminated areas.
Radioactivity can be removed from milk through a chelating process, said Roger A. Clemens, associate director of the regulatory science program at the USC School of Pharmacy. That would be an option for the Japanese government to consider.
What about water?
People may have to use bottled water to avoid contaminated tap water, Zurosky said. Radioactive water can be cleaned by filtering, but it would be an enormous task to meet the demands of an urban area.
Can crops be protected?
It is possible to cover vegetables, fruit and animal feed with plastic sheets or tarpaulins, according to the FDA. Livestock can be moved into barns.
How much radioactive material is permitted in foods?
The World Health Organization has established limits that serve as guidelines for governments. But there are no hard and fast rules in the United States, said George H. Pauli, a retired food safety official who spent 29 years at the FDA.
"You don't want people to slide up to the limit," he said. "It's treated on a case-by-case basis when there's a problem."
Radioactive material in food is measured in becquerels, or Bq. The limit for iodine-131 is 55 Bq per kilogram for infant food and 300 Bq per kilogram for other foods regulated by the FDA. For meat and poultry, which are regulated by the Department of Agriculture, the limit is 55 Bq per kilogram. The limit for cesium-134 and cesium-137 for all foods is 370 Bq per kilogram.
In Japan, some milk was reported to contain 1,510 Bq of iodine-131 per kilogram.
How does the FDA protect U.S. residents from radioactive food?
The FDA screens all imported food at U.S. borders, and the agency recently announced that screening for radiation contamination will be stepped up. The agency's food tracking system has been programmed to automatically flag all shipments of FDA-regulated products from Japan. The FDA is also working with the Japanese government to ensure imported food remains safe.
At this time, Japan isn't exporting any food products from Fukushima prefecture. Foods from Japan make up less than 4% of products imported to the United States, and only a fraction of those are dairy products.
The FDA probably won't monitor U.S. crops for contamination by radioactive particles that may have drifted across the Pacific Ocean because the risk is too small, Pauli said.
What if there were a nuclear accident here?
The FDA would advise state and local authorities, who would take the lead on removing contaminated products from the food supply. Generally speaking, officials would strive for zero contamination but would balance the risks of radioactivity against the desire to avoid food shortages. "Sometimes a tiny risk of radiation is better than the risk of starvation," Pauli said.
Photos: Japan grapples with crisis