Air Quality Index

How clean is the air in your metropolitan area? The U. S. Environmental Protection Agency (EPA) has provided a scale called the Air Quality Index (AQI) for rating air quality. This scale is based on the National Ambient Air Quality Standards (NAAQS) and is described in the Code of Federal Regulations, Part 58, Appendix G. This report is based on the AQI standards.

Interpreting the AQI

Reporting for December 5, 2012
Metropolitan Area or Non-Metropolitan County		Air Quality	Critical Pollutant	Air Quality Index Rating
				Ozone				Carbon Monoxide		Sulfur Dioxide		Nitrogen Dioxide		PM-10 (Std Cond)		PM-2.5 (Lcl Acpt)
				1-Hour		8-Hour		8-Hour		1-Hour		1-Hour		24-Hour		24-Hour
				AQI	ppb	AQI	ppb	AQI	ppm	AQI	ppb	AQI	ppb	AQI	µg/m³ (25° C)	AQI	µg/m³ LC
Amarillo -- Region 1
	Amarillo	Good	PM-2.5													20	4.9


Lubbock -- Region 2
	Lubbock ¹	††															§


Abilene -- Region 3
	Wichita Falls	Good	PM-2.5													19	4.5


Dallas-Fort Worth -- Region 4
	Dallas	Good	Ozone	*	40	30	35	3	0.3	18	13	24	26			26	6.2
	Fort Worth-Arlington	Good	Nitrogen Dioxide	*	41	31	36	4	0.4			32	34			29	6.9
	Navarro County	Good	Ozone	*	36	25	30			2	2	4	5			24	5.7


Tyler-Longview-Marshall -- Region 5
	Longview-Marshall	Good	PM-2.5	*	28	19	23			3	2	9	10			21	5.0
	Tyler	Good	Ozone	*	27	18	21					13	14


El Paso-Juarez -- Region 6
	Brewster County ¹	Good	PM-2.5		§		§									13	3.0
	El Paso ¹	Moderate	PM-2.5	*	39	28	33	30	2.7	15	11	54	57	52	57.0	58	15.3
	Juarez ¹	Good	Carbon Monoxide	*	28	18	21	42	3.7


Odessa-Midland -- Region 7
	Odessa-Midland	Good	PM-2.5													26	6.2


Waco -- Region 9
	Killeen-Temple	Good	Ozone	*	44	33	39
	Waco ¹	Good	Ozone	*	46	32	38	1	0.1		§	20	21				§


Beaumont-Port Arthur -- Region 10
	Beaumont-Port Arthur ¹	Good	PM-2.5	*	36	25	30	2	0.2	5	4	15	16			27	6.6


Austin -- Region 11
	Austin-San Marcos ¹	Good	Nitrogen Dioxide	*	42	31	36	4	0.3	1	1	33	35			23	5.5
	Fayette County ¹	Good	PM-2.5		§		§									25	5.9


Houston-Galveston-Brazoria -- Region 12
	Brazoria	Good	Ozone	*	28	20	24					19	21
	Galveston-Texas City	Good	PM-2.5	*	32	23	27			1	0	14	15			26	6.2
	Houston ¹	Good	PM-2.5	*	30	21	25	4	0.4	3	2	29	31			45	10.7


San Antonio -- Region 13
	San Antonio ¹	Good	Nitrogen Dioxide	*	48	35	41	3	0.3	4	3	37	39	13	14.5	24	5.7


Corpus Christi-Victoria -- Region 14
	Corpus Christi	Good	Ozone	*	55	40	47			2	2					29	7.0
	Victoria ¹	Good	Ozone	*	43	30	35						§


Lower Rio Grande Valley -- Region 15
	Brownsville-Harlingen-San Benito	Good	Ozone	*	57	40	47	0	0.0						§		§
	McAllen-Edinburg-Mission	Good	PM-2.5	*	41	31	36							18	19.7	33	7.9


Laredo -- Region 16
	Laredo ¹	Good	PM-2.5	*	47	31	37	9	0.8						§	38	9.2
	Maverick County	Good	PM-2.5													16	3.9
PM-10 is measured at standard pressure and temperature conditions.
PM-2.5 Acceptable is measured at local pressure and temperature conditions.
†† No AQI has been calculated for this metropolitan area. This can happen early in the morning before enough valid O₃ or CO hourly samples have been collected to create an eight-hour average and should clear up once enough samples are collected. If there are no measurements for any parameter, this indicates a data collection problem. Once this problem is resolved, the data will be filled in and a AQI will be calculated (if possible).
¹ Not all monitors are reporting for this metropolitan area.
§ No data of this type was collected on December 5, 2012 for this metropolitan area, or there were not enough valid hourly samples collected on this date to meet data completeness requirements of a minimum of 18 valid hourly samples in a day, or there have not been enough valid O₃ or CO hourly samples collected to create an eight-hour average.
* There is no AQI associated with hourly ozone averages less than 0.125 ppm (125 ppb).

PLEASE NOTE: Data in this table is collected from TCEQ air monitoring sites, local agencies, and private monitoring networks. Site specific information is available for each metropolitan area by clicking on the metropolitan area name. This data has not been verified by the TCEQ or the responsible entity and may change. While this is the most current data, it is not official until it has been certified by the appropriate technical staff. This table is updated hourly. Click here for information about all the monitoring sites.

Interpreting the AQI

Air Quality Index

Each NAAQS pollutant has a separate AQI scale, with an AQI rating of 100 corresponding to the concentration of the Federal Standard for that pollutant. Additional information about the AQI and how it can be used is available from the EPA.

Place your mouse pointer over the scale displayed above to view information about the Air Quality Index, and each of the rating levels.

The actual index calculation is different for each parameter measured and is specified by the EPA. The following table shows the various breakpoints used in calculating the AQI.

AQI Breakpoint Definitions
AQI Range	1hr Ozone in ppm	8hr Ozone in ppm	8hr Carbon Monoxide in ppm	1hr Sulfur Dioxide in ppm	24hr Sulfur Dioxide in ppm	1hr Nitrogen Dioxide in ppm	24hr PM-10 in µg/m³ (25° C)	24hr PM-2.5 in µg/m³ LC
0 - 50	Not Defined	0 - 0.059	0 - 4.4	0 - 0.035	Not Defined	0 - 0.053	0 - 54	0 - 12.0
51 - 100	Not Defined	0.06 - 0.075	4.5 - 9.4	0.036 - 0.075	Not Defined	0.054 - 0.1	55 - 154	12.1 - 35.4
101 - 150	0.125 - 0.164	0.076 - 0.095	9.5 - 12.4	0.076 - 0.185	Not Defined	0.101 - 0.36	155 - 254	35.5 - 55.4
151 - 200	0.165 - 0.204	0.096 - 0.115	12.5 - 15.4	0.186 - 0.304	Not Defined	0.361 - 0.64	255 - 354	55.5 - 150.4
201 - 300	0.205 - 0.404	0.116 - 0.374	15.5 - 30.4	Not Defined	0.305 - 0.604	0.65 - 1.24	355 - 424	150.5 - 250.4
301 - 400	0.405 - 0.504	Not Defined	30.5 - 40.4	Not Defined	0.605 - 0.804	1.25 - 1.64	425 - 504	250.5 - 350.4
401 - 500	0.505 - 0.604	Not Defined	40.5 - 50.4	Not Defined	0.805 - 1.004	1.65 - 2.04	505 - 604	350.5 - 500.4
500+	Not Defined	Not Defined	Not Defined	Not Defined	Not Defined	Not Defined	605 - 4999	500.5 - 999.9

The AQI for ozone is based on either the peak eight-hour running average since midnight OR the peak one-hour measurement since midnight. When calculating air quality for the current day, the Virginia DEQ uses a surrogate 8-hour average based on the current hourly average.
The AQI for carbon monoxide is based on the peak eight-hour running average since midnight.
The AQI for sulfur dioxide is based on the peak one-hour measurement since midnight. There is a secondary NAAQS based on a 24-hour average of sulfur dioxide sampled from midnight to midnight, but this NAAQS has such a high starting point that is is never expected to be reached.
The AQI for nitrogen dioxide is based on the peak one-hour measurement since midnight.
The AQI for PM-10 is based on a 24-hour average sampled from midnight to midnight.
The AQI for PM-2.5 is based on a 24-hour average sampled from midnight to midnight.

PLEASE NOTE: This data has not been verified by the TCEQ and may change. This is the most current data, but it is not official until it has been certified by our technical staff. Data is collected from TCEQ ambient monitoring sites and may include data collected by other outside agencies. This data is updated hourly. All times shown are in local standard time unless otherwise indicated.

Following EPA reporting guidelines, negative values may be displayed in our hourly criteria air quality data beginning 1/1/2013, down to the negative of the EPA listed Method Detection Limit (MDL) for the particular instrument that made the measurements. The reported concentrations can be negative due to zero drift in the electronic instrument output, data logger channel, or calibration adjustments to the data. Prior to 1/1/2013, slightly negative values were automatically set to zero.