It's routine protocol for agents at all ports of entry to screen for radiation with personal radiation devices, but now Homeland Security is directing agents to be more watchful.
"In an exercise of caution, and just to make sure everyone remains safe, we are doing screenings of passengers and cargo," said Secretary of Homeland Security Janet Napolitano. "If there happens to be a blip in terms of radiation."
Japan's nuclear crisis is drawing attention worldwide and is the reason many U.S. residents and Japanese nationals alike are leaving the country.
"I think everyone was paying attention to it," said Phoenix resident Kevin Strehlow. "I was definitely worried about the future with radiation levels because I know they are growing over time. Even in Tokyo, I know they're saying it's like getting an X-ray, but over time even that can grow worse."
"What's happening in Japan is quite scary," said Tokyo resident Mako Valentine. "We're not getting the real story so to be safe we came back to the States."
San Diego resident Pamela Molohon said she's relieved to be back in the U.S., but is worried about her son and his family.
"My daughter-in-law and I agreed not to take the children outside," said Molohon. "Don't take them outside needlessly because the situation can change from moment to moment."
For Tokyo resident Robert Dudley, the order to come home came from his mother.
"I'm going to have him go to Kaiser to get him checked out," said Dudley's mom Joyce Revis. "I already had that planned, he didn't know. I'm so glad, you don't even know. I am just glad my kid is back."
Homeland Security said that so far no harmful levels of radiation have reached the U.S. But radiation has been detected on several passengers at airports in the country, including Chicago and Dallas.
But what is the next step if harmful levels are found? Those individuals will meet with health officials, but where will they go? It's still unclear if there will be a quarantine process.