It’s a problem hidden in plain sight, found throughout the U.S. and across the world. Human trafficking, or modern day slavery, is more pervasive than ever.

On Sunday, the U.N.’s World Day Against Trafficking, Pope Francis made an appeal to the world, urging countries to take action against “this abhorrent plague, a form of modern slavery.”

The International Labor Organization estimates that nearly 21 million people are victims of forced labor, human trafficking, and sexual exploitation— more than at any other time in history.

One in five of those victims are the most vulnerable among us: boys and girls, separated from their families and forced into prostitution, or labor that makes use of their small hands, like sewing or untangling fishing wire.

ChildFund International is one organization working to reduce the risks that children will be sold by traffickers and help ensure that young people around the world have a brighter future. ChildFund works with governments and local partners across the world to combat the kidnapping, buying, and selling of children.

High unemployment rates and poverty are just two of the factors that put children at risk. In India, for example, over 100,000 kids are trafficked each year across the border from Rajasthan to its neighboring state of Guajarat. These children are forced to work in cotton fields, often in debt bondage— to pay back what their families owe.

To combat this, ChildFund is working to strengthen five local organizations in Rajasthan to protect children, as well as families and community leaders, including promoting a series of mentoring activities, training, and coaching. ChildFund also works to increase access to education for children, a critical element to preventing trafficking— if kids stay in school, they are less likely to be lured away by traffickers.

Women, refugees, and those fleeing war or conflict are also at higher risk of enslavement. “Trafficking in people in conflict situations is not a mere possibility but something that happens on a regular basis,” said Maria Grazia Giammarinaro, the U.N.’s special rapporteur on human trafficking, in October 2016.

But modern slavery isn’t just a morally abhorrent crime. It’s a lucrative industry— human trafficking is one of the largest international crime industries in the world. Each year, forced labor in sectors like domestic work, agriculture, construction, manufacturing, and entertainment generates $150 billion in illegal profits.

Human trafficking has been found in every country throughout the world, including the U.S. Though it’s a domestic issue— trafficking in the U.S. being most prevalent in Texas, Florida, New York, and California — global crime networks can become a threat to America’s national security.

Drug dealers, money launderers, or arms dealers are in part enabled or funded by human trafficking activities. And some governments, such as North Korea, depend on forced labor to elicit revenue.

U.S. consumers also play an unwitting role. Some products Americans use and enjoy may have been produced by those in forced servitude. The U.S. State Department works to alert businesses during these situations so they may take direct action to insure they aren’t complicit in human trafficking.

The U.S. is taking action, leading global efforts to address human trafficking. Its policy involves three “P”s: preventing trafficking, protecting victims, and prosecuting traffickers.

Just six months ago, Congress passed the End Modern Slavery Initiative, legislation introduced by Senate Foreign Relations Committee Chairman Bob Corker and supported by a bipartisan Congress, faith-based organizations like Bread for the World and World Vision, as well as countless individuals.

“As I have seen firsthand, the stark reality of modern slavery is unconscionable, demanding the United States and civilized world make a commitment to end it for good,” said Corker when the bill was signed into law December 23, 2016.

“By providing strong U.S. leadership and leveraging our limited foreign aid dollars, this initiative will work with foreign governments and philanthropic organizations to match the funding being provided by the United States and create a coordinated effort to implement best practices to eliminate modern slavery and human trafficking around the globe,” stated Corker.

More recently, the State Department released the 2017 Trafficking in Persons Report. The Victims of Trafficking and Violence Protection Act of 2000, created because “the degrading institution of slavery continues throughout the world,” mandated the annual brief, which assesses what actions governments around the world are taking to address the issue.

At the report’s launch, Secretary Tillerson remarked, “Human trafficking is as old as humankind. Regrettably, it’s been with us for centuries and centuries. But… it is our hope that the 21st century will be the last century of human trafficking, and that’s what we are all committed to.”

Human trafficking affects Americans around the world and here at home. But it’s not just governments or private organizations that can take action to help stop modern slavery. The State Department’s Office to Monitor and Combat Trafficking in Persons, which leads America’s global engagement against compelled servitude, has a list of 15 action steps that any citizen can take to help fight human trafficking.

You can read more about how the End Modern Slavery Initiative works here.