# 40 CFR Part 50, Appendix N to Part 50 - Interpretation of the National Ambient Air Quality Standards for PM2.5

*2.5*

*2.5*specified in § 50.7 and § 50.13 of this part are met. PM

*2.5*, defined as particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers, is measured in the ambient air by a Federal reference method (FRM) based on appendix L of this part, as applicable, and designated in accordance with part 53 of this chapter, or by a Federal equivalent method (FEM) designated in accordance with part 53 of this chapter, or by an Approved Regional Method (ARM) designated in accordance with part 58 of this chapter. Data handling and computation procedures to be used in making comparisons between reported PM

*2.5*concentrations and the levels of the PM

*2.5*NAAQS are specified in the following sections.

*2.5*NAAQS. In other cases, it may be more appropriate to retain the data for comparison with the levels of the PM

*2.5*NAAQS and then for EPA to formulate the appropriate regulatory response.

*Annual mean*refers to a weighted arithmetic mean, based on quarterly means, as defined in section 4.4 of this appendix.

*Creditable samples*are samples that are given credit for data completeness. They include valid samples collected on required sampling days and valid “make-up” samples taken for missed or invalidated samples on required sampling days.

*Daily values*for PM

*2.5*refers to the 24-hour average concentrations of PM

*2.5*calculated (averaged from hourly measurements) or measured from midnight to midnight (local standard time) that are used in NAAQS computations.

*Designated monitors*are those monitoring sites designated in a State or local agency PM Monitoring Network Description in accordance with part 58 of this chapter.

*Design values*are the metrics (

*i.e.*, statistics) that are compared to the NAAQS levels to determine compliance, calculated as shown in section 4 of this appendix:

*annual standard design value*”). If spatial averaging has been approved by EPA for a group of sites which meet the criteria specified in section 2(b) of this appendix and section 4.7.5 of appendix D of 40 CFR part 58, then 3 years of spatially averaged annual means will be averaged to derive the

*annual standard design value*for that group of sites (further referred to as the “

*spatially averaged annual standard design value*”). Otherwise, the annual standard design value will represent the 3-year average of annual means for a single site (further referred to as the “

*single site annual standard design value*”).

*24-hour standard design value*”).

*Extra samples*are non-creditable samples. They are daily values that do not occur on scheduled sampling days and that can not be used as make-ups for missed or invalidated scheduled samples. Extra samples are used in mean calculations and are subject to selection as a 98th percentile.

*Make-up samples*are samples taken to supplant missed or invalidated required scheduled samples. Make-ups can be made by either the primary or the collocated instruments. Make-up samples are either taken before the next required sampling day or exactly one week after the missed (or voided) sampling day. Also, to be considered a valid make-up, the sampling must be administered according to EPA guidance.

*98th percentile*is the daily value out of a year of PM

*2.5*monitoring data below which 98 percent of all daily values fall.

*Year*refers to a calendar year.

*2.5*standards.

*2.5*. For example, this could be demonstrated by site-specific chemical speciation profiles confirming all major component concentration averages to be within 10 percent for each calendar quarter.

*2.5*. Exceptions to the specified sampling frequencies, such as a reduced frequency during a season of expected low concentrations (

*i.e.*, “seasonal sampling”), are subject to the approval of EPA. Annual 98th percentile values are to be calculated according to equation 5 in section 4.5 of this appendix when a site operates on a “seasonal sampling” schedule.

*2.5*NAAQS and Data Reporting Considerations.

*2.5*data required to be submitted to EPA's Air Quality System (AQS) shall be used in the design value calculations.

*2.5*measurement data (typically hourly for continuous instruments and daily for filter-based instruments) shall be reported to AQS in micrograms per cubic meter (µg/m

^{3}) to one decimal place, with additional digits to the right being truncated.

*2.5*concentration data for each corresponding day of the year and the result shall be stored in the first, or start, hour (

*i.e.*, midnight, hour ‘0’) of the 24-hour period. A 24-hour average shall be considered valid if at least 75 percent (

*i.e.*, 18) of the hourly averages for the 24-hour period are available. In the event that less than all 24 hourly averages are available (

*i.e.*, less than 24, but at least 18), the 24-hour average shall be computed on the basis of the hours available using the number of available hours as the divisor (e.g., 19). 24-hour periods with seven or more missing hours shall be considered valid if, after substituting zero for all missing hourly concentrations, the 24-hour average concentration is greater than the level of the standard. The computed 24-hour average PM

*2.5*concentrations shall be reported to one decimal place (the additional digits to the right of the first decimal place are truncated, consistent with the data handling procedures for the reported data).

*i.e.*, that site's daily value); this includes all creditable samples and all extra samples.

*i.e.*, that site's daily value). If more than one valid collocated FRM/FEM/ARM value is available, the average of those valid collocated values shall be used as the daily value.

*2.5*NAAQS.

*2.5*NAAQS.

*2.5*NAAQS is met when the annual standard design value is less than or equal to 15.0 micrograms per cubic meter (µg/m

^{3}).

*2.5*NAAQS.

*2.5*NAAQS is met when the 24-hour standard design value at each monitoring site is less than or equal to 35 µg/m

^{3}. This comparison shall be based on 3 consecutive, complete years of air quality data. A year meets data completeness requirements when at least 75 percent of the scheduled sampling days for each quarter have valid data. However, years shall be considered valid, notwithstanding quarters with less than complete data (even quarters with less than 11 samples), if the resulting annual 98th percentile value or resulting 24-hour standard design value (rounded according to the conventions of section 4.3 of this appendix) is greater than the level of the standard.

*Rounding Conventions*. For the purposes of comparing calculated values to the applicable level of the standard, it is necessary to round the final results of the calculations described in sections 4.4 and 4.5 of this appendix. Results for all intermediate calculations shall not be rounded.

*2.5*standard design values shall be rounded to the nearest 0.1 µg/m

^{3}(decimals 0.05 and greater are rounded up to the next 0.1, and any decimal lower than 0.05 is rounded down to the nearest 0.1).

*2.5*standard design values shall be rounded to the nearest 1 µg/m

^{3}(decimals 0.5 and greater are rounded up to the nearest whole number, and any decimal lower than 0.5 is rounded down to the nearest whole number).

*2.5*NAAQS.

*2.5*is determined by first averaging the daily values of a calendar quarter using equation 1 of this appendix:

*q,y,s*= the mean for quarter q of the year y for site s;

*q*= the number of daily values in the quarter; and

*i q,y,s*= the i

^{th}value in quarter q for year y for site s.

*y,s*= the annual mean concentration for year y (y = 1, 2, or 3) and for site s; and

*q,y,s*= the mean for quarter q of year y for site s.

*i.e.*, for single site comparisons), skip to equation 4.B of this appendix.

*y*= the spatially averaged mean for year y,

*y,s*= the annual mean for year y and site s for sites designated to be averaged that meet completeness criteria , and

*s*= the number of sites designated to be averaged that meet completeness criteria.

*y*= the spatially averaged annual mean for year y (result of equation 3 of this appendix) when spatial averaging is used, or

*y,s*the annual mean for year y and site s (result of equation 2 of this appendix) when spatial averaging is not used.

*2.5*NAAQS

*Regular procedure for identifying annual 98th percentile values.*Identification of annual 98th percentile values using the regular procedure (table 1) will be based on the creditable number of samples (as described below), rather than on the actual number of samples. Credit will not be granted for extra (non-creditable) samples. Extra samples, however, are candidates for selection as the annual 98th percentile. [The creditable number of samples will determine how deep to go into the data distribution, but all samples (creditable and extra) will be considered when making the percentile assignment.] The annual creditable number of samples is the sum of the four quarterly creditable number of samples.

*Procedure:*Sort all the daily values from a particular site and year by descending value. (For example: (x[1], x[2], x[3], * * *, x[n]). In this case, x[1] is the largest number and x[n] is the smallest value.) The 98th percentile is determined from this sorted series of daily values which is ordered from the highest to the lowest number. Using the left column of table 1, determine the appropriate range (

*i.e.*, row) for the annual creditable number of samples for year y (cn

*y*). The corresponding “n” value in the right column identifies the rank of the annual 98th percentile value in the descending sorted list of daily site values for year y. Thus, P

*0.98, y*= the nth largest value.

Annual creditable number of samples for year “y” (cny) |
P0.98, y is the nth maximum value of the year, where n is the listed number |
---|---|

1-50 | 1 |

51-100 | 2 |

101-150 | 3 |

151-200 | 4 |

201-250 | 5 |

251-300 | 6 |

301-350 | 7 |

351-366 | 8 |

*Procedure:*Calculate the annual 98th percentiles by determining the smallest measured concentration, x, that makes W(x) greater than 0.98 using equation 5 of this appendix:

*High*= number of calendar days in the “High” season;

*Low*= number of calendar days in the “Low” season;

*High*d

*Low*= days in a year; and

*High*/(d

*High*d

*Low*) and d

*Low*/(d

*High*d

*Low*)” are constant and are called seasonal “weights.”

**Title 40 published on 2014-07-01**

no entries appear in the Federal Register **after** this date.

**Title 40 published on 2014-07-01**

The following are **ALL** rules, proposed rules, and notices (chronologically) published in the Federal Register relating to *40 CFR 50* **after** this date.

GPO FDSys XML | Text type regulations.gov FR Doc. 2014-30688 RIN 2060-AP38 EPA-HQ-OAR-2008-0699 FRL-9921-26-OAR ENVIRONMENTAL PROTECTION AGENCY Announcement of public hearings. The public hearings will be held on January 29, 2015, in Washington, DC and Arlington, Texas, and on February 2, 2015, in Sacramento, California. Please refer to SUPPLEMENTARY INFORMATION for additional information on the public hearings. 40 CFR Parts 50, 51, 52, 53, and 58 The Environmental Protection Agency (EPA) is announcing three public hearings for the proposed rule titled, “National Ambient Air Quality Standards for Ozone,” that was published in the Federal Register on December 17, 2014. The hearings will be held in Washington, DC, Arlington, Texas, and Sacramento, California. Based on its review of the air quality criteria for ozone (O 3 ) and related photochemical oxidants and national ambient air quality standards (NAAQS) for O 3, the EPA proposes to make revisions to the primary and secondary NAAQS for O 3 to provide requisite protection of public health and welfare, respectively. The EPA is proposing to revise the primary standard to a level within the range of 0.065 to 0.070 parts per million (ppm), and to revise the secondary standard to within the range of 0.065 to 0.070 ppm, which air quality analyses indicate would provide air quality, in terms of 3-year average W126 index values, at or below a range of 13-17 ppm-hours. The EPA proposes to make corresponding revisions in data handling conventions for O 3 and conforming changes to the Air Quality Index; to revise regulations for the Prevention of Significant Deterioration program to add a transition provision for certain applications; and to propose schedules and convey information related to implementing any revised standards. The EPA is proposing changes to the O 3 monitoring seasons, the Federal Reference Method (FRM) for monitoring O 3 in the ambient air, Federal Equivalent Method procedures for testing, and the Photochemical Assessment Monitoring Stations network. Along with proposing exceptional event schedules related to implementing any revised O 3 standards, the EPA is proposing to apply this same schedule approach to other future revised NAAQS and to remove obsolete regulatory language for expired exceptional event deadlines. The EPA is proposing to make minor changes to the procedures and time periods for evaluating potential FRMs and equivalent methods (including making the requirements for nitrogen dioxide consistent with the requirements for O 3 ) and to remove an obsolete requirement for the annual submission of documentation by manufacturers of certain particulate matter monitors.

GPO FDSys XML | Text type regulations.gov FR Doc. 2014-28674 RIN 2060-AP38 EPA-HQ-OAR-2008-0699 FRL-9918-43-OAR ENVIRONMENTAL PROTECTION AGENCY Proposed rule. Written comments on this proposed rule must be received by March 17, 2015. Public Hearings: The EPA intends to hold three public hearings on this proposed rule in January 2015. These will be announced in a separate Federal Register notice that provides details, including specific dates, times, addresses, and contact information for these hearings. 40 CFR Parts 50, 51, 52, 53, and 58 Based on its review of the air quality criteria for ozone (O 3 ) and related photochemical oxidants and national ambient air quality standards (NAAQS) for O 3, the Environmental Protection Agency (EPA) proposes to make revisions to the primary and secondary NAAQS for O 3 to provide requisite protection of public health and welfare, respectively. The EPA is proposing to revise the primary standard to a level within the range of 0.065 to 0.070 parts per million (ppm), and to revise the secondary standard to within the range of 0.065 to 0.070 ppm, which air quality analyses indicate would provide air quality, in terms of 3-year average W126 index values, at or below a range of 13-17 ppm-hours. The EPA proposes to make corresponding revisions in data handling conventions for O 3 and conforming changes to the Air Quality Index (AQI); to revise regulations for the prevention of significant deterioration (PSD) program to add a transition provision for certain applications; and to propose schedules and convey information related to implementing any revised standards. The EPA is proposing changes to the O 3 monitoring seasons, the Federal Reference Method (FRM) for monitoring O 3 in the ambient air, Federal Equivalent Method (FEM) procedures for testing, and the Photochemical Assessment Monitoring Stations (PAMS) network. Along with proposing exceptional event schedules related to implementing any revised O 3 standards, the EPA is proposing to apply this same schedule approach to other future revised NAAQS and to remove obsolete regulatory language for expired exceptional event deadlines. The EPA is proposing to make minor changes to the procedures and time periods for evaluating potential FRMs and equivalent methods (including making the requirements for nitrogen dioxide consistent with the requirements for O 3 ) and to remove an obsolete requirement for the annual submission of documentation by manufacturers of certain particulate matter monitors. For additional information, see the Executive Summary, section I.A.