People working in Pittsburgh will be guaranteed time off for illness for the first time, under a new ordinance passed Monday by the city council.

The new law will require businesses with 15 or more employees to give workers five paid days off to care for themselves or a family member. Businesses with fewer employees will be required to provide 24 hours of paid sick time per year. Lawmakers and advocates in the city say that the law will affect 50,000 workers who lack paid sick time off.

“Paid sick days in Pittsburgh is a win-win,” Sue Frietsche, senior staff attorney at the Pennsylvania-based Women’s Law Project, said in a statement. “It’s a win for workers, and also a victory for public health.”

“Over three quarters of Pittsburgh’s service workers had no paid sick time, and these workers—food service workers, health care workers—come into close contact with lots of people,” she added. “When they come to work sick, they make other people sick.”

The Pittsburgh City Council passed the ordinance in a 7-1 vote less than a month after its introduction, to the ire of some business owners, who say they will challenge the ordinance in court, and the only abstaining council member.

Opponents of the law contend that it will hurt businesses and prove costly to the city despite growing evidence to the contrary. Business interest groups like the U.S. Chamber of Commerce have long opposed any laws allowing workers paid time off.

“If this is passed and successfully challenged in court, it’s going to be a costly mistake that taxpayers will have to fund,” said Councilwoman Darlene Harris, who abstained during voting.

The right-wing legislation mill known as the American Legislative Exchange Council (ALEC) has pushed copycat bills in legislatures across the country to preempt paid sick leave laws, including in Republican-dominated states like Arizona, Florida, Indiana, and Oklahoma. Wisconsin Gov. Scott Walker, a 2016 GOP presidential candidate, struck down Milwaukee’s paid sick leave ordinance in 2011. That ordinance received 70 percent of the popular vote three years earlier.

Evidence from the growing number of cities that have already mandated paid sick leave suggests that such laws benefit employers by lowering turnover and increasing productivity.

Pittsburgh is the 20th city nationwide to pass paid sick leave requirements. The first, San Francisco, put paid sick leave on the books in 2006. Four states—Connecticut, California, Massachusetts, and most recently Oregon—have also passed similar laws.

The Philadelphia City Council in February approved a paid sick leave measure, which also allows survivors of domestic violence to use the days to seek treatment, legal services, relocation, or other support.

Hours later, Republican state legislatures introduced SB 333, a bill that threatens to overturn both cities’ ordinances by prohibiting sick leave laws on the municipal level and voiding any such laws already in effect.

The bill was passed overwhelmingly by the state’s Republican-majority senate and is now being considered by the state house, also dominated by Republicans.

As part of a White House tour to support municipalities with paid sick leave laws, Valerie Jarrett, a senior advisor to President Obama, spoke out against Pennsylvania’s attempt to limit paid sick leave.

“Really look at the evidence,” Jarrett said during a roundtable discussion at the Philadelphia City Hall. “I think, frankly, Pennsylvania should follow Philadelphia’s lead. Don’t you?”

The White House tour is also meant to drum up support for federal legislation, which has stalled so far. During his 2015 State of the Union address, Obama made a call for city-level action, and this year members of Congress reintroduced the Healthy Families Act, which would give millions of workers up to seven paid sick days per year.

Republicans opposed the Healthy Families Act.

The United States is the only developed country with no national paid sick leave law, leaving nearly 40 percent of private sector workers with no paid days off.