How bad was Thursday’s air quality? Region’s second-worst day recorded under modern index

Thursday marked the second-worst day for air quality in the Sacramento region recorded since 2003, according to Spare the Air, the region’s database for air quality measurements.

The Air Quality Index for particulate matter (PM2.5) measured an aggregate of 314 for the 24-hour period, based on readings from Sacramento, Placer, El Dorado and Yolo-Solano air districts.

Abysmal air quality conditions continued overnight and into Friday, with AQI readings exceeding 400 in Arden Arcade (408 at midnight) and downtown Sacramento (427 at 2 a.m.). The AQI scale tops out at 500.

Air quality has been better in some parts of the Sacramento area than others. East of Sacramento, the cities of Folsom and Roseville were faring much better, with AQI readings below 150 as of 7 a.m., than downtown Sacramento, where AQI has exceeded 300 all morning.


This live-updating map shows the combined readings for particulate matter and ozone.
AQI Animation -

The National Weather Service also warned of unhealthy air conditions, and forecasts predict winds will allow Camp Fire smoke to persist in Sacramento and the Valley through the weekend.

The only worse day on record than Thursday, using current federal Environmental Protection Agency standards, came Sept. 21, 2014, eight days after a 97,000-acre blaze called the King Fire sparked in El Dorado County. AQI in Sacramento peaked at 320 that day.

Spare the Air does not maintain individual day data for 2008. However, another database made available by the California Air Resources Board shows AQI readings did not exceed 300 that year.

From 2003 to 2007, AQI readings for particulate matter never exceeded 300, according to Spare the Air.

PM2.5 AQI was not recorded in Sacramento prior to 2003. AQI standards are reviewed every five years by the EPA, in accordance with the 1990 Clear Air Act.

Any AQI reading 300 or higher is denoted “hazardous,” meaning serious health effects can result from spending time outdoors. Sunday reached an AQI reading of 300; Thursday, Sunday and the September 2014 date are the only three “hazardous” days on record since 2009.

Visibility has also been reduced considerably — down to about a half-mile at Sacramento International Airport, according to NWS.

Smoky conditions have plagued Sacramento since the weekend. On Sunday, the city started handing out N95 respirator masks to residents for free, distributing them from fire stations. Handouts of the masks are ending, though, due to an advisory issued by the county this week warning that the masks do more harm than good.

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