Los Alamos County, New Mexico air quality history

Daily Air Quality Index summaries from EPA monitors in Los Alamos, New Mexico, 1988–2025.

100%

Good days in 2023

Median daily AQI, 2023

Days above 100 in 2023

121

Days with an AQI in 2023 (of 365)

In 2023, EPA reported a daily Air Quality Index (AQI) for Los Alamos, New Mexico on 121 days. 121 of those days (100%) were in the Good range, and the median daily AQI was 14. That median is lower than the typical monitored county in New Mexico (median 44 across 12 counties), and lower than the typical monitored U.S. county (43). The main pollutant was fine particles (PM2.5) on 121 days. Across the years with fuller monitoring, the share of Good days rose: an average of 82% in 1989–1991 versus 99% in 2013–2023.

EPA did not report an AQI for every day of 2023 here (121 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (2019, 2020, 2021, 2022, 2024, 2025…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2023

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Fine particles (PM2.5)	121	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Median AQI	90th pct.	Max AQI	Main pollutant
2025	82	82	0	0	13	27	42	PM2.5
2024	116	116	0	0	14	27	41	PM2.5
2023	121	121	0	0	14	27	50	PM2.5
2022	118	112	5	1	14	39	103	PM2.5
2021	119	115	3	1	14	34	109	PM2.5
2020	117	113	4	0	13	25	58	PM2.5
2019	117	117	0	0	12	21	42	PM2.5
2018	120	120	0	0	13	31	43	PM2.5
2017	116	115	1	0	12	27	54	PM2.5
2016	119	119	0	0	11	21	32	PM2.5
2015	114	114	0	0	13	26	44	PM2.5
2014	117	117	0	0	14	26	43	PM2.5
2013	121	119	2	0	14	34	58	PM2.5
2012	115	115	0	0	19	33	48	PM2.5
2011	110	103	7	0	14	32	93	PM2.5
2010	112	112	0	0	13	21	39	PM2.5
2009	109	108	1	0	15	27	68	PM2.5
2008	115	114	1	0	16	32	52	PM2.5
2007	118	115	3	0	17	28	63	PM2.5
2006	116	116	0	0	13	26	44	PM2.5
2005	115	114	1	0	14	27	54	PM2.5
2004	117	117	0	0	14	26	42	PM2.5
2003	112	110	2	0	17	28	52	PM2.5
2002	115	114	1	0	17	32	51	PM2.5
2001	121	120	1	0	15	28	58	PM2.5
2000	101	99	2	0	16	28	70	PM2.5
1999	102	102	0	0	18	32	44	PM2.5
1998	101	100	1	0	17	31	53	PM2.5
1997	102	100	2	0	19	34	52	PM2.5
1996	95	94	1	0	18	36	81	PM2.5
1995	90	90	0	0	15	29	47	PM2.5
1994	300	234	65	1	44	67	129	Ozone
1993	346	287	59	0	44	58	90	Ozone
1992	365	261	102	2	46	64	108	Ozone
1991	365	258	100	7	46	77	122	Ozone
1990	346	268	77	1	44	71	112	Ozone
1989	154	152	2	0	28	40	53	Ozone
1988	83	83	0	0	21	31	47	PM2.5

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

All monitored counties in New Mexico

Source: U.S. EPA AirData, “Annual AQI by County” files for 1988–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem