According to inside climate new, A coalition of environmental activists and advocacy groups is urging the Biden administration to toughen federal regulations around soot pollution, a step that they said could prevent thousands of deaths each year from respiratory disorders.

The coalition, organized by the Climate Action Campaign, drafted a letter to President Joe Biden earlier this week calling on federal officials to institute the most rigorous air quality standards for fine particulate matter, or PM 2.5, to denote bits of pollution smaller than 2.5 microns—about one-thirtieth the diameter of a human hair.

The current standard for particulate matter from soot pollution is 12 micrograms per cubic meter of air as an annual average. The advocacy groups asked Biden to toughen that standard to 8 micrograms per cubic meter.

What is soot pollution?

The term soot refers to particulate matter with a diameter of 2.5 micrometers or smaller, commonly called PM 2.5. These fine particles are even smaller than dust and mold, or about 1/30 of the size of a human hair.

The emission of soot is caused by a wide range of sources, including coal as an energy source, oil refining, manufacturing, and even motor vehicles.

Soot pollution has been linked to cardiac arrest, asthma attacks and what experts call “premature deaths” from a range of cardiovascular and breathing disorders.

Most particulate matter is generated by vehicle exhaust, and emissions from power plants and other industrial operations.

“Each day that passes without updated limits is another day that millions of Americans are exposed to unhealthy and potentially dangerous levels of soot pollution,” the advocates wrote in a letter that was signed by more than 150 environmental groups from across the country.

The advocates cited a study released earlier this year by the Environmental Defense Fund, which found that as many as 19,600 deaths each year that are attributed to the harms of particulate matter could be avoided.