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

Los Angeles is now a week removed from the day that multiple devastating wildfires erupted to torch tens of thousands of acres. But still, the question remains if people should wear masks to limit their exposure to toxins in the air.

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,

Dust and ash left behind from the January wildfires in Los Angeles County can be irritating and hazardous to health when it’s picked up by winds and spread throughout Southern California. Windblown dust and ash contain small particles that may cause irritation or exacerbate pre-existing health conditions,

Toxic smoke and dangerous particulate pollution are spreading far beyond the flames, leaving air quality at unhealthy levels in multiple counties.