Ambient Air Quality Standards

Monitoring Program – Pollutants of Concern

The principal ambient air pollutants, based on public health concerns, have been identified by the U.S. Environmental Protection Agency (EPA) as “criteria” pollutants. The EPA established National Ambient Air Quality Standards (NAAQS) for these criteria pollutants. The standards of quality for ambient air in Nevada differ from EPA’s and shall not be exceeded. Detailed information on each criteria pollutant may be found on EPA’s criteria pollutant website.

Notes

A: The Director shall use the Nevada standards in considering whether to issue a permit for a stationary source and shall ensure that the stationary source will not cause the Nevada standards to be exceeded in areas where the general public has access.

B: The National standards are used in determinations of attainment or nonattainment. The form of a National standard is the criteria which must be satisfied for each respective concentration level of a standard for the purposes of attainment. The form for each National standard is set forth in 40 C.F.R. Part 50 and may be viewed at http://www.epa.gov/air/criteria.html.

C: Where applicable, concentration is expressed first in units in which it was adopted. All measurements of air quality that are expressed as mass per unit volume, such as micrograms per cubic meter, must be corrected to a reference temperature of 25 degrees Centigrade and a reference pressure of 760 mm of Hg (1,013.2 millibars); “ppm” in this table refers to parts per million by volume, or micromoles of regulated air pollutant per mole of gas; “µg/m3” refers to micrograms per cubic meter.

D: Any reference method specified in accordance with 40 C.F.R. Part 50 or any reference method or equivalent method designated in accordance with 40 C.F.R. Part 53 may be substituted.

E: National primary standards are the levels of air quality necessary, with an adequate margin of safety, to protect the public health.

F: National secondary standards are the levels of air quality necessary to protect the public welfare from any known or anticipated adverse effects of a regulated air pollutant.

G: The EPA revoked the National 1-hour ozone standard as it applies to all areas. However, anti-backsliding provisions in Federal law require certain areas to have continuing obligations under the National 1-hour ozone standard.

H: The 1971 National sulfur dioxide standards remain in effect for an area until 1 year after the area is designated for the 2010 National sulfur dioxide standard, except that in an area designated nonattainment for the 1971 National sulfur dioxide standards, the 1971 standards remain in effect until an implementation plan to attain or maintain the 2010 National sulfur dioxide standards is approved.

I: The ambient air quality standard for hydrogen sulfide does not include naturally occurring background concentrations.

Table of the National Ambient Air Quality StandardsPollutantPrimary/SecondaryAveraging TimeLevelFormCarbon Monoxide (CO)Primary8-hours9 ppmNot to be exceeded more than once per year1-hour35 ppmLead (Pb)Primary and secondaryRolling 3-month average0.15 µg/m3Not to be exceededNitrogen Dioxide (NO2)Primary1-hour100 ppb98th percentile of 1-hour daily maximum concentrations, averaged over 3 yearsPrimary and secondary1-year53 ppbAnnual meanOzone (O3)Primary and secondary8-hours0.070 ppmAnnual fourth-highest daily maximum 8-hour concentration, averaged over 3 yearsParticle Pollution (PM)PM2.5Primary1-year12.0 µg/m3Annual mean, averaged over 3 yearsSecondary1-year15.0 µg/m3Annual mean, averaged over 3 yearsPrimary and secondary24-hours35 µg/m398th percentile, averaged over 3 yearsPM10Primary and secondary24-hours150 µg/m3Not to be exceeded more than once per year on average over 3 yearsSulfur Dioxide (SO2)Primary1-hour75 ppb99th percentile of 1-hour daily maximum concentrations, averaged over 3 yearsSecondary3-hours0.5 ppmNot to be exceeded more than once per year