Last month, the Environmental Protection Agency effectively disbanded a scientific panel of experts on microscopic airborne pollutants that helped the agency figure out what level of pollutants are safe to breathe. The agency also dropped plans for a similar panel of experts to help assess another dangerous pollutant, ground-level ozone.

These decisions were the latest assaults on science at an agency that depends on science to protect Americans’ health, safety and quality of life.

The disbanded panel on particulate pollution reported to the E.P.A.’s seven-member Clean Air Scientific Advisory Committee, which is responsible for advising the agency on overall air quality standards. Now, without the work of that panel, it is entirely likely that the advisory committee will lack the time and expertise to provide authoritative guidance on the regulation of this pollutant. The same can be said of ground-level ozone.

And that is no small matter. The E.P.A. itself says that numerous studies show that particulate pollution can lead to premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeats, aggravated asthma and decreased lung function. Ground-level ozone can affect the breathing of people with asthma, children, older adults, and people who are active outdoors.