California has more federal workers than any other state - even Virginia and the District of Columbia, where many federal agencies are concentrated. They work for the Internal Revenue Service, the Bureau of Land Management, the Federal Aviation Administration, the Department of Defense and NASA, among others, and Boxer said they're hurting.
"They don't have a check," she said, meeting with reporters at her office on an unusually deserted Capitol Hill. "They're scared."
Boxer added that if the shutdown continues into next week, there could be local impacts in California. The national parks are closed for the duration, including Yosemite. The closure follows recent Rim Fire, which burned more than 300 square miles in and near Yosemite. The region depends economically on the park for the tourism it generates.
Boxer said about two-thirds of her 60 staff members are furloughed in Washington and California, including six who exclusively perform case work. That covers passport requests, veterans benefits, housing and mortgage assistance, Social Security and Medicare, immigration and education. She said her office received about 16,000 such requests in 2010.
"They're proud of the work they do," she said of her staff.
House Republicans insist on changes to the federal health care law, President Barack Obama's signature legislative achievement, before they will approve legislation to fund the government and raise the country's borrowing limit.
Republican leaders, including House Speaker John Boehner, have accused the president and Democrats of refusing to negotiate.
Boxer said there was nothing to negotiate. "This thing could end in 15 minutes," she said, if Boehner put a bill on the House floor with no strings attached.
"You don't negotiate showing up," she said. "The grownups have to stand up and say, 'we have to do our jobs.'"
She said Republicans are "sore losers" who refuse to accept that they lost the presidential election last year, and that their repeated efforts to repeal or delay the law have failed. The health-care law took effect on Tuesday.
"The irony is, they can't stop the Affordable Care Act," she said.
Editor's Note: This story has been updated to correct the number of furloughed workers in California from 150,000 to 50,000. Updated at 3:54 p.m. Oct. 3, 2013.