Masks – How much protection?
Dr. Wayne Cascio
Wayne Cascio, MD, who directs the EPA’s National Health and Environmental Effects Research Laboratory, notes that some public health officials don’t recommend wearing N95 masks during wildfire smoke events. “There’s a lot of concern that people won’t use them correctly and will therefore feel like they’re protected and will spend more time outdoors than they should and still not get the benefit,” he said. “The masks also pose a challenge for children and for people with severe asthma and COPD.”
Masks also have to fit properly, which can be problematic for kids, added Dr. Balmes, one of the authors of “Wildfires Disaster Guidance: Tips for Staying Healthy During Wildfires” (Am J Respir Crit Care Med. 2019;199[2]:3-4).
“Even the small versions don’t necessarily fit kids well, so they’re not recommended for kids,” he said. “It doesn’t mean a kid couldn’t wear them, but it’s not officially recommended. The actual physiologic work of breathing isn’t much increased by using the N95 mask, but if you’re already struggling to get your breath, or experience dyspnea, then it might be hard to wear one. People with milder COPD can wear an N95 mask just like people with mild asthma if they have to go out.”
The EPA published a tip sheet about where and when to use an N95 or P100 mask, with warnings about the limited protection these devices offer, especially if not used correctly. Most masks do not protect the wearer from harmful gases that can be in wildfire smoke.
Ventilation systems
The EPA also recommends that people with more severe disease should stay indoors and avoid using air conditioning units that only draw in air from the outside or do not have a recirculating option. “If you have to bring in outside air because that’s how your system works, you should have a MERV 13 or better filter to filter out the fine particles,” Dr. Balmes said. “Not every ventilation system can handle it, but most can. That will help the house.”
Dr. Cascio pointed out that the instruction to close all windows and doors is a difficult proposition for people who live in states with moderate weather climates such as Montana and Colorado, where few homes have central air conditioning. “The treatment may be worse than the disease in this case, because it may exacerbate heat stress,” he said. “Try to find a place that has cleaner air. That might be a public building, a school, a fitness center, or a library. Yet we don’t know a lot about whether those areas are cleaner or not. That is currently the subject of some research on our part.”
Traveling away from an area affected by wildfire smoke to ride out the conditions is one option, but that can backfire. One weekend when smoke from the 2008 North Carolina peat fire was particularly troublesome, Dr. Cascio and his family drove about 60 miles west of Greenville to the town of Zebulon, where a minor league baseball game was being played and the air quality was good.
“My thought was to get the family to a better environment for at least a few hours,” Dr. Cascio recalled. “When we arrived in Zebulon the air quality was good as advertised. However, the direction of the wind shifted and the smoke started to move due west and within a short time you could barely see the players on the field. This experience also pointed out one of the lessons of wildfire smoke. That is, in the short term, it is sometimes difficult to predict where it will be present because of the nature of changes in weather and wind.”