Space datacenters proposed by SpaceX, Jeff Bezos’s Blue Origin and others would release staggering levels of pollution that would probably alter the Earth’s atmosphere and be “catastrophic” for the planet, space industry experts and environmental groups warn in a new petition demanding a review of their impacts.

Tech companies have collectively proposed millions of “orbital datacenters” and are pressing forward with plans, which require Federal Communications Commission (FCC) approval. Among other issues, pollution from satellites and rockets burning up upon re-entry appears to be accumulating in the stratosphere at alarming levels. The spacecraft release black soot, rare metals, aluminum oxides and other pollutants with unknown effects.

Some scientists fear the pollution could destroy the ozone layer, potentially expose some people to higher levels of ultraviolet radiation, or help further destabilize the planet during the climate crisis. The pollution could also end up back on Earth, and millions of satellites would create a major source of light pollution.