Key Terms

µg: The symbol for "microgram." A microgram is a measurement equal to one millionth of a gram. You may also see microgram listed as "mcg."

Action level (AL): Employee exposure (without use of a respirator) over an eight-hour time period to an airborne concentration of lead at the measurement of 30 micrograms per cubic meter of air (30 µg/m³).

Competent person: Someone able to identify existing and potential lead hazards in the surroundings or working conditions. This person has authorization to take immediate measures to eliminate these hazards.

Lead: In this course and in OSHA's Lead Standard, lead refers to metallic lead, inorganic lead compounds, and organic lead soaps. Not included in this definition are all other organic lead compounds.

Permissible exposure limit (PEL): The maximum worker lead exposure allowed. The U.S. PEL is 50 micrograms of lead per cubic meter of air (50µg/m³). This exposure is for an average over an eight-hour period.

Time-weighted average (TWA): A method for calculating a worker's daily exposure to a hazardous substance (in this case, lead) averaged to an 8-hour workday and taking into account the average levels of the substance and the amount of time spent in the area.

To learn more about Construction Lead Safety visit our Construction Lead Safety Online Training Certification web page.