Mark Zuckerberg, chief executive officer and founder of Facebook Inc., listens during a joint hearing of the Senate Judiciary and Commerce Committees in Washington, D.C., U.S., on Tuesday, April 10, 2018.

Facebook pays the reviewers responsible for filtering the site's most disturbing content just a fraction of its median salary, according to an explosive report by The Verge.

U.S.-based content moderators — third-party contractors at a company called Cognizant— earn $15 an hour, or $28,000 a year, according to the report. Managers at the content moderation sites earn $16 an hour. The median annual salaries for Facebook employees was $240,000 in 2017.

The report sheds new light on the emotional and physical toll of being Facebook's main line of defense against abusive content. The company has touted its growing workforce and security effort. The content the moderators have to look at include killings, porn and conspiracy theories, The Verge said.

"We value the hard work of content reviewers and have certain standards around their well-being and support," a spokesperson for Facebook said in a statement. "We work with only highly reputable global partners that have standards for their workforce, and we jointly enforce these standards with regular touch points to ensure the work environment is safe and supportive, and that the most appropriate resources are in place."

In a blog post later Monday, Facebook said the company knows "there are going to be incidents of employee dissatisfaction or hardship that call our commitment into question."

Current and former content moderators, under pseudonyms to discuss information protected by nondisclosure agreements, told The Verge employees are strictly capped at two 15-minute breaks and one 30-minute lunch during the day. They also told The Verge they felt disconnected from full-time, salaried Facebook employees.

Breaks are often spent fighting for time in too-small bathrooms, doing drugs or having sex to relax, The Verge reports. When employees tried to skirt the break limitations by using the bathroom during designated "wellness time," for example, they were told to stop.

According to a statement sent by Facebook, a Cognizant spokesperson said the company has investigated the issues raised in The Verge report and has "previously taken action where necessary and have steps in place to continue to address these concerns and any others raised by our employees."

"Cognizant is committed to providing a healthy, safe and positive work environment for all of our associates," the spokesperson said. "Our goal is to ensure that we provide a variety of support options including on-site counselors, a robust wellness program and resources and wellness classes covering a range of disciplines to support the needs of every employee involved in content moderation."

Cognizant did not respond directly to requests for comment from CNBC.

Read the full report at The Verge.

WATCH: Facebook might need to undergo 'fundamental change' in order to combat hate speech, says NYT's Ed Lee