
- Particulate matter from burned structures has led to dangerous chemicals such as lead, polyaromatic hydrocarbons and asbestos in the air.
- Get pros to clean in severely burn-impacted areas. They can minimize their exposure with better PPE, properly dispose of debris and minimize resuspension in the process.
- When air sensors are green, or for most people, yellow, and no obvious ash is floating around, there is no reason to curtail activity.
Even though the Palisades and Eaton fires are now mostly contained, the Santa Ana winds have led to new fires flaring up across Los Angeles County. While many of the latter have been in areas of dense brush, resulting in wildfire smoke, the destruction of homes, businesses and various structures in the earlier blazes has caused more dangerous problems with the air quality in Southern California.
Particulate matter from burned structures has led to toxic chemicals such as lead, polyaromatic hydrocarbons and asbestos in the air.
With the weather changing daily, UCLA’s Suzanne Paulson, professor of atmospheric and oceanic sciences and an expert on smog, ozone and air pollution, answered important questions about protecting yourself and your loved ones from those invisible dangers.
How do I know what the air quality is like in my specific area?
For rapidly changing conditions and highly localized pollution sources like fires, it’s best to rely on a dense network of real-time sensors such as purpleair, clarity and fire.airnow.gov, rather than from the air quality index, or AQI, on a weather app. The more general AQIs are based on larger areas and longer timescales, so they are not very useful under the current conditions. Do keep in mind that a single sensor can sometimes be inaccurate due to sensor error due to smoke from backyard barbecues, etc. Looking at several nearby sensors can give you a better picture of local air quality.What are the limitations of air quality sensors?
Many of the air quality sensor maps only show particle concentrations, but there are also gasses that are concerning, such as formaldehyde, polyaromatic hydrocarbons and nitrogen oxides, or NOx. However, the main factor controlling the hour-by-hour changes in concentrations of air pollutants is dilution, which is controlled by the atmosphere. If the particle concentrations are low, the gas concentrations from the same source will usually be low as well.One caveat is large ash particles (which are not detected by the sensor networks). While the gasses, smoke particles and respirable asbestos particles individually weigh too little to be rapidly removed from the air via gravity, bits of ash fall much more rapidly, so they can impact different areas than the gasses and smoke particles, which may drift far away.
Are there more metals in the air after the wildfires than usual?
Almost all’air pollution particles contain low levels of metals. These metals, however, can be very active biologically. A small number of real-time measurements showed extremely high levels of metals in the smoke plumes, but the airborne metal levels have now essentially returned to their normal levels.What counts as in or near a burn area?
Current thinking is that we should treat an area as "near a burn area" if it is within several houses of the burn, but also if there is a lot of ash or if the area is downwind of the fires. This includes areas that were in the smoke plume for an extended period or areas that are downwind of the fire now. People who live within a mile or so of the fires but weren’t in the smoke plume or downwind may only need to take precautions if the wind changes direction. For people spending time somewhere with a lot of ash, but in a place that is rarely downwind, they only need to take precautions until the ash is professionally removed.Get pros to clean in severely burn-impacted areas. They can minimize their exposure with better PPE, properly dispose of debris and minimize resuspension in the process.
What should I know about the impacts of ash on air quality?
In burn areas, ash can contain many toxic materials, which can become airborne as it is disturbed.Ash is too large for the sensors to detect. Also, the readings, especially near the fires, are likely worse than they appear because the sensors don’t measure everything we would like. There may be gasses, such as polyaromatic hydrocarbons, near the smoke sources and in the burn area, which can linger after the fires are over.
Ash is a completely different size from the fine and coarse particulate matter that composes smoke. Ash travels and deposits in different places. The ash particles fall comparatively fast and fall within 10s of minutes to the ground. The tiny particulate matter that can get into the lungs can drift long distances, and, depending on the size, can stay in the air for many hours or around a week.
How can I reduce my exposure to smoke or any high levels of air pollution?
- Stay inside: Being inside with windows closed generally cuts concentrations of both particles down by roughly 50%.
- Run AC, heating or just the fan: Running the heat, fan or air conditioning further reduces concentrations, even without specific filtration, because gasses and particles are removed on surfaces as the air passes through the system.
- While the air movement from heating systems helps clean the air, the basic filters many heating systems have do not help much with air quality inside the home. The filters are designed to keep much larger particles out of the HVAC system, not to clean the air. If a heating system can accommodate filters with higher filtration capacity, indicated by higher MERV, or minimum efficiency reporting value ratings, they can further clean the air.
- Use air-purifying HEPA or charcoal filters. HEPA filters are highly effective at removing particles, and charcoal filters can reduce gas concentrations.
- Wear masks: The tighter-fitting and more highly rated masks, like N95 and KN95, the better. These are designed to remove particles, but because air is forced to pass through very tight spaces, they will also reduce some gasses to some extent.
- Reduce exertion when concentrations of pollutants are high. Keeping pets and children inside when concentrations are high can reduce their exposure by half or more because everyone breathes less air when they move less.
How long do we need to be extra vigilant about air quality?
When the sensors are green, or for most people, yellow, and no obvious ash is floating around, there is no reason to curtail activity. However, while there are active burns, the particles may be more toxic than usual, so when the particle concentrations are higher, extra vigilance is warranted. In the burn areas, there will be reason for extra vigilance for an extended period, at least months.Paulson answered more questions about air quality here.