Democratic senators are putting pressure on leading tech corporations to reveal the working conditions of their ghost employees—the unseen workers that categorize data and analyze replies and are crucial to the development of artificial intelligence.

In a letter sent to executives at nine companies on Wednesday, including Amazon.com Inc., Alphabet Inc., Meta Platforms Inc., Microsoft Corp., and International Business Machines Corp., a group of lawmakers complained that “despite the essential nature of this work, millions of data scientists around the world perform these stressful tasks under constant surveillance, low pay, and no benefits.”

Executives are being questioned by lawmakers on a wide range of topics relating to their data workers, such as whether or not they have the right to take breaks, contest suspensions, or seek mental health assistance when exposed to traumatic material.

Democrats, including former presidential candidate Elizabeth Warren of Massachusetts and a senator from Massachusetts, stated that tech companies “should not create AI at the expense of exploited workers.”

The letter was sent to new artificial intelligence businesses, OpenAI Inc., Inflection AI, Scale AI Inc., and Anthropic, in addition to well-known technology behemoths.