WASHINGTON – The U.S. Environmental Protection Agency (EPA) is investigating Make Sunsets, a startup that has been launching balloons filled with sulfur dioxide (SO₂) into the atmosphere as part of a solar geoengineering project aimed at cooling the planet by reflecting sunlight back into space.
On April 15, 2025, the EPA sent a formal request for information to the company, seeking details on launch locations, SO₂ sourcing, and any coordination with local or federal regulators. The agency noted that the company’s website claims over 120 launches to date. SO₂ is a regulated pollutant under the Clean Air Act, known to cause respiratory issues, acid rain, and haze, and has been controlled since 1971 to protect air quality.
Make Sunsets describes its work as “stratospheric aerosol injection,” a method inspired by volcanic eruptions that temporarily lower global temperatures. The company sells “cooling credits” based on its releases, positioning itself as a climate tech firm. However, the EPA’s inquiry highlights potential regulatory gaps in private geoengineering activities.
The startup has already faced international backlash, including a ban on operations in Mexico. In the U.S., the investigation marks one of the first federal responses to growing private-sector interest in atmospheric modification. Make Sunsets has expressed willingness to cooperate and help develop a “regulatory framework,” according to statements from the company.
The probe remains ongoing, with no charges filed or penalties announced. Environmental groups have raised concerns about the lack of oversight for such experiments, while supporters argue they could provide short-term climate relief. The outcome may influence future U.S. policies on geoengineering proposals.
