July Fourth fireworks may bring ‘hazardous’ air quality to Southern California. What you need to know

L.A.’s love of fireworks makes for a colorful Fourth of July, with dozens of official celebrations and countless illicit explosions expected for the holiday.

But as each sparkler, Roman candle, palm and peony dissipates, it leaves behind a cloud of noxious gases, soot and finely ground toxic metals — some of which ends up in the lungs of revelers and passersby below.

Hazardous levels of air pollution are expected across central and southern Los Angeles County, northern Orange County, and Riverside and San Bernardino counties from 5 p.m. Saturday evening through 3 p.m. Sunday, according to the South Coast Air Quality Management District. Unhealthy air quality is also expected in northern Los Angeles County and southern Orange County.

Pollution levels are expected to build from dusk onward Saturday, as light winds and increased firework activity lead to an increase in smoke, a South Coast AQMD advisory said. Soot and particulates will likely linger through Sunday afternoon before being dispersed by the wind.

Firework-related pollution can trigger coughs, breathing problems, asthma flares and heart attacks, according to Los Angeles County Public Health, and anyone experiencing severe or worsening cardiovascular symptoms like chest pain or difficulty breathing should seek medical attention immediately.

Pyrotechnics set off at home are even more likely to trigger cardiovascular problems, the American Lung Assn. says, as the burst of pollutants takes place closer to the ground.

July 4 and 5 are traditionally two of the worst days of the year for the region’s air quality, according to South Coast AQMD. This year’s celebration comes on the heels of a late June warehouse fire in Boyle Heights that released extraordinary amounts of soot and smoke across the county, on par with pollution generated by the previous year’s wildfires.

To limit negative health effects, the L.A. County public health department recommends avoiding strenuous physical activity and keeping doors and windows closed. As whole house fans and swamp coolers can suck additional pollutants inside, the department recommends using air purifiers or air conditioners as alternatives when possible.