Storyline: Wildfires in the Los Angeles area of Southern California have forced residents to remain indoors due to hazardous air quality. Health officials are warning of the long-term effects of toxic chemicals, ash, and particulate matter, which pose serious health risks to both humans and pets. Nathaniel Stern, a resident of West Los Angeles, normally spends a lot of time outdoors with his dog. However, a week and a half of wildfires have changed all that. Stern, along with many others, is concerned about the long-term impact of toxic chemicals and ashes in the air. The smoke from the fires is harmful to pets as well. Health officials point out that even on seemingly clear days, particulate matter, hazardous soot, and microscopic pollution from the burned areas remain in the air. Health officials warn residents to take precautions if they see ash in the air and to wear a mask to avoid exposure. Although the Air Quality Index has improved slightly in recent days, officials from the South Coast Air Quality Management District warn that conditions could worsen with more Santa Ana winds in the forecast. In such a case, they advise the public to wear N95 masks, stay indoors, and limit physical exercise. The fierce wildfires across the Los Angeles area have so far killed at least 27 people and destroyed more than 12,300 structures, local authorities confirmed on Thursday. Up to 200,000 people have been displaced by the fires. As of Wednesday, some 82,400 residents were under evacuation orders and another 90,400 faced evacuation warnings, according to Los Angeles County Sheriff Robert Luna. Shotlist: Los Angeles, USA - Recent: 1. Various of Nathaniel Stern, resident of West Los Angeles, leaving his house, walking with dog outdoors; 2. SOUNDBITE (English) Nathaniel Stern, resident, West Los Angeles: "This is the first time I've ever seen ashes from the sky here in West Los Angeles. Because of that, the air quality has been so bad, I haven't been able to take him out for a walk around the block or go for my evening runs. We've just been cooped up inside for the past week." 3. Various of Stern walking with dog outdoors; 4. Ash on ground; 5. SOUNDBITE (English) Dr Anish Mahajan, chief deputy director, Los Angeles County Department of Public Health (partially overlaid with shot 6): "There are fine particulates in the air that are of small size, 2.5 micrometers, much smaller than a human hair, that can be breathed in and lodged deep in your lungs and really cause health problems, especially in the short run for people who have health conditions. But there's also a lot of ash, debris and dust as a result of burning of structures, houses, homes, cars. They can be quite toxic, and they've come in a toxic form. And they are in the ash and the dust." [SHOTS OVERLAYING SOUNDBITE] 6. Various of ash, debris on ground; [SHOTS OVERLAYING SOUNDBITE] 7. Various of wildfires, houses; 8. SOUNDBITE (English) Brent Pascua, battalion chief, California Department of Forestry and Fire Protection (partially overlaid with shot 9): "[If] they smell smoke or if they're having issues breathing, wear a mask and move out of the area, go to somewhere where it's clear. Right now, we don't have any smoke, but it could easily turn around if we get those red-flag warnings back, and we get a new start even in the area. That could very well happen." [SHOT OVERLAYING SOUNDBITE] 9. Wildfires on mountains; [SHOT OVERLAYING SOUNDBITE] 10. Various of wildfires, houses. [Restrictions : No access Chinese mainland]