Air quality in wildfire-stricken Los Angeles improved on Thursday from hazardous peaks hit earlier this month, as tiny soot particles that can penetrate the lungs and brain dropped to moderate levels,

Calculating air pollution from wildfires and other events has become more complicated. That doesn’t mean it’s necessarily more accurate.

Wildfire ash carries many carcinogens that could cause short- and long-term health problems, including asthma attacks and difficulty breathing.

Ash from the recent LA County fires and burn scars formed by other wildfires in the fall can be dispersed by strong winds. See an air quality map.

The hazardous air quality in Los Angeles is largely a result of smoke from the Pacific Palisades Fire, intensified by strong Santa Ana winds.