Sulfuric Acid

What is sulfuric acid?
Sulfuric acid (H2SO4) is a colorless, odorless, oily liquid that is very corrosive and reacts chemically with many other materials and substances. Sulfuric acid has a wide range of uses and is one of the world's most widely used industrial chemicals.

Where does sulfuric acid come from?
The most natural source of sulfuric acid released into the air comes from volcanoes. Many ordinary human activities release sulfuric acid into the environment. For example, cutting onions causes a chemical from the onions to mix with eye moisture to create dilute sulfuric acid.

How is sulfuric acid used?
In the United States, about 40 million tons of sulfuric acid are manufactured for industrial use each year. It has several industrial purposes, including for example:

• pulp and paper manufacturing;
• copper, steel and metal fabrication;
• fertilizer, chemical, textile, explosive and paint manufacturing;
• soap and detergent production;
• water treatment; and
• petroleum product refinement.

These activities release sulfuric acid into the environment; nearly all is released into the air.

Do electric utilities release sulfuric acid into the environment?
Yes. Sulfur is present in coal and oil. When electric utilities burn these fuels in their power plants, some of the sulfur is released. This sulfur combines with oxygen and water vapor to form dilute sulfuric acid vapor. As it cools, some of this sulfuric acid vapor forms tiny liquid droplets or thin films on tiny ash particles. Vapor, liquid droplets, and ash particles containing dilute sulfuric acid can enter the air in gases leaving power plant stacks.

About 3% of the sulfur in fuels burned by power plants is released into the air as sulfuric acid. The amount of sulfuric acid released by an individual power plant depends on the sulfur content of the fuel it burns, as well as operating and air pollution control practices at the plant.

How could sulfuric acid affect me?
There is no evidence that common exposures to the dilute sulfuric acid from power plants can harm human health. However, more concentrated levels of sulfuric acid fumes can irritate people's eyes, skin and breathing passages, and concentrated fumes can permanently damage the nose and lungs. Also, direct contact with concentrated sulfuric acid solutions can burn the skin and destroy eyesight, and swallowing them can be fatal.

Industrial workers are most likely to be exposed to concentrated sulfuric acid fumes or solutions in other industries. Both the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have set limits on the amount of sulfuric acid in workplace air.

Sulfuric acid has not been found to cause cancer in animals or to affect their reproduction. According to the Electric Power Research Institute, research to date has not shown a health risk from any acid aerosols at strengths common in U.S. air.

What does EPA say?
EPA refers to sulfur acid-bearing "mists, vapors, gas, fog, and other airborne forms of any particle size" as "sulfuric acid aerosols." The agency has not classified sulfuric acid as a hazardous air pollutant. For this reason, sulfuric acid was not included in EPA's 1998 analysis of health risks from power plant releases of hazardous air pollutants.

Researchers continue to study the possible health effects of breathing particles, including sulfuric acid aerosols.

Where can I get more information?

• Electric Power Research Institute
  3412 Hillview Ave.
  P.O. Box 10412
  Palo Alto, California 94303
  Phone (650) 855-2000
  
  
• The Agency for Toxic Substances
  and Disease Registry Information Center
  Phone (800) 447-1544