PM2.5 Exposure Dose Calculator
Fine particulate matter (PM2.5) is small enough to reach deep into the lungs, which is why the U.S. EPA regulates it under the National Ambient Air Quality Standards. This calculator estimates the mass of PM2.5 you inhale during an exposure period. The inhaled dose equals the air concentration times the volume of air breathed (your inhalation rate times the exposure time) times the fraction of particles that deposit in the airways. With concentration in micrograms per cubic metre and breathing in cubic metres per hour, the result is in micrograms. Inhalation rate and deposition fraction depend on activity and particle behaviour, so both are user-editable inputs you can set from EPA exposure factors.
Inhaled dose formula
Air breathed = inhalation rate * exposure time
Total inhaled mass = concentration * air breathed
Deposited dose (ug) = total inhaled mass * deposition fraction
Deposited dose (mg) = deposited dose ug / 1,000
Concentration is in micrograms per cubic metre, inhalation rate in cubic metres per hour, and time in hours, so the inhaled mass comes out in micrograms.
PM2.5 exposure context
- PM2.5 is fine particulate of 2.5 micrometres diameter or smaller, regulated by the EPA.
- The EPA National Ambient Air Quality Standards set annual and 24-hour PM2.5 limits.
- Breathing rate rises with physical activity, increasing the volume of air inhaled.
- Only the deposited fraction stays in the respiratory tract; the rest is exhaled.
- This dose estimate complements, and does not replace, the regulatory concentration limits.
PM2.5 exposure: frequently asked questions
How is an inhaled PM2.5 dose calculated?
The inhaled mass equals the air concentration times the volume of air breathed times the fraction of particles that deposit in the airways: dose = concentration times inhalation rate times time times deposition fraction. With concentration in micrograms per cubic metre and breathing in cubic metres per hour, the result is in micrograms.
What is PM2.5?
PM2.5 is fine particulate matter with an aerodynamic diameter of 2.5 micrometres or smaller. Because the particles are small enough to reach deep into the lungs, the U.S. EPA regulates PM2.5 under the National Ambient Air Quality Standards. This calculator estimates how much mass you inhale at a given concentration.
What inhalation rate should I use?
Breathing rate depends on activity and body size, from roughly 0.5 cubic metres per hour at rest to several cubic metres per hour during heavy exertion. Because it varies, the inhalation rate is a user-editable input. EPA exposure factors handbooks publish representative values.
What does the deposition fraction mean?
Not every inhaled particle stays in the body; some are exhaled. The deposition fraction is the share that deposits in the respiratory tract, which depends on particle size and breathing pattern. It is an input defaulting to a conservative value you can adjust to match a published deposition estimate.
How does this relate to air quality standards?
The EPA sets the primary annual PM2.5 standard and a 24-hour standard as concentrations, not doses. This calculator turns a concentration into the mass you would inhale over a chosen period, which complements but does not replace the regulatory concentration limits.
Official sources
- U.S. Environmental Protection Agency: Particulate Matter (PM) Pollution.
- U.S. Environmental Protection Agency: NAAQS Table.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.