When my family returned home to Santa Monica last Sunday night, we breathed a sigh of relief. Our house is fine and the air quality is in the "good" category. Schools will reopen the next day. But as we were unpacking, I noticed what looked like salt-and-pepper snow dancing gently in the street. Ashes from the Palisades Fire, burning five miles north of us, were falling in all directions, covering the cars we had left behind. In the backyard it gathers in the small patch of lawn where we play and in small clusters in the garden where my kids recently planted carrots.

The next morning we walked to school and talked about the blue sky. My 8-year-old pointed to a pile of windblown ash on the side of the road. Children will stay indoors that day so the school can clean up playground equipment and yard debris.

As I walked the four blocks home, a city street sweeper buzzed by. When the truck's bristles hit the ash, it kicks up a car-sized cloud of dust, sending all the debris back into the air. I gripped the N95 mask tighter, took off my sunglasses, and jogged away. I closed the door tightly behind me.

That night, a local bookstore and mediation space held a "Crying in the Rain for the Fire-Destroyed Land" ceremony. Rain helps prevent more fires from starting and also helps wash away ash. Now, we're left to deal with it ourselves, wiping down surfaces, cleaning streets, and wondering what we're breathing in and what impact it will have on the waterways that absorb it.

Debris continued to fall Tuesday, so the school held a "walk-only" recess. My heart sank when I saw the gardeners arriving with leaf blowers. (Los Angeles County has temporarily banned their use because they kick up too much dust.) But no one knows exactly how to clean up the mess. A neighbor was cleaning the stairs with a Shop-Vac.

With smoke, the danger is obvious: you can see it, smell it, and get out of the way. Our phones kept vibrating, displaying the Air Quality Index, which measures air pollution but not ash. With ash swirling like poisonous plumes, it's hard to know what's safe. The residue from a house fire contains more toxins than the residue from a brush fire. PVC pipes, lithium-ion car batteries, plastic siding, flooring, and everything else that evaporates in a fire releases a host of chemicals (nickel, chromium, arsenic, mercury) into the air. Older homes may contain lead and asbestos. It wasn't until Wednesday, the day after the walking break, that Los Angeles County issued a volcanic ash advisory recommending staying indoors and wearing a mask and goggles when leaving home.

But much of our life in Los Angeles is outdoors: It's a city of year-round outdoor dining, winter temperatures hover around 60 degrees Fahrenheit, and surfers hit the water in January. If there is no rain in the forecast, how long will our lives be covered by a thin layer of toxic dust? It may take a long time: A webinar hosted by California's anti-drug community warned that ash from the fires would take years to dig out and pose a public health risk.

The prospect of continued exposure to airborne chemicals sounds ominous, but Thomas Borch, a professor of environmental and agricultural chemistry at Colorado State University, takes a more optimistic view. After the Marshall Fire ripped through towns in the Rocky Mountain foothills in 2021, Boch studied contaminants in the soil of homes near the fire. Some properties had higher levels of heavy metals, but most were still below worrying levels. Although living in a fine cloud of debris might feel apocalyptic, Boch told me the wind might help dilute the pollution near my home. "Many ashes are spread over a larger area," which helps mitigate their health effects, he said.

Once ash and soot seep into a home through doors, windows, shoes and clothing, "it's much more difficult to actually remove," he added. Cleaning can re-contaminate indoors and must be done with care. Botsch recommends that we vacuum with a HEPA filter and a wet mop to prevent contaminants from building up inside the house.

But real questions about human health and volcanic ash remain unanswered. Researchers have only recently begun to study how ash from structure fires differs from ash from wildfires. In Los Angeles, Bochy's colleagues set up 10 coffee bag-sized samplers around the fire (as close as allowed). They also plan to collect ash from within burned areas and from windblown dust to compare different toxins in smoke and ash, as well as their concentrations in the weeks and months after a fire.

If the rain does come, it will wash away most of the debris and the city will become clear again. But stormwater can also carry pollutants into streams, drinking water reservoirs or the Pacific Ocean. Maybe by then the wind will have blown away most of the ash, or in places outside the direct path of the fire, like near my house, we'll clear it ourselves. (Removing ash from fire areas is a regulated process.) My family is still waiting to pull up the yard vegetables, but I no longer worry about pinball and biking. We slowly wetted the stone patio and stairs and tried to gently sweep away the ash, while making sure we wore gloves, goggles and masks. Half the neighbors outside were wearing masks. We are still hovering like ashes from the crisis, waiting for the rain to set things right again.