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Posted on behalf of Suren Bandara.

Who is affected?

In the last couple of weeks, California has seen the most lethal outbreak of wildfires in the state’s history (CNBC 2017). The huge wildfires swept across Sonoma, Napa and Mendocino counties, sending smoke and ash over San Francisco (about 50 miles away) and to some towns and cities even further away. While the wildfires are being controlled, concerns over the wildfire smoke, which can persist for days or even months, depending on the extent of the fire, have arisen. Although the air may look clear, it may have particulate matter than can cause respiratory distress. Anyone who spends time outdoors during and after a wildfire can be affected by poor air quality, and outdoor workers are especially vulnerable.

Health basis

According to the Centers for Disease Control and Prevention (CDC), wildfire smoke is a mix of gases and fine particles from burning vegetation, building materials, and other materials (CDC 2017). This complex mixture resulting from combustion may contain carbon dioxide, water vapor, carbon monoxide, hydrocarbons and other organic chemicals, nitrogen oxides, trace minerals, and particulate matter (USEPA 2016). Outdoor workers exposed to these compounds via wildfire smoke inhalation might be at risk of developing mild to severe health symptoms, including difficulty breathing, scratchy throat, runny nose, irritated sinuses, reduced lung function, asthma attacks, chest pain, heart failure, or even death (CDC 2017, USEPA 2016). Persons with preexisting pulmonary and cardiovascular conditions may be more likely to get sick if they breathe in wildfire smoke (USEPA 2016).

Precautions employers can take

According to the US EPA, particulate matter is the principal pollutant of concern for persons exposed to wildfire smoke. Particulate matter larger than 10 mm do not usually reach the lungs, but may irritate the eyes, nose, and throat. However, wildfire smoke may contain particulates that are <10 mm, which can be inhaled into the deepest recesses of the lungs and can affect both the lungs and heart (USEPA 2016). Fortunately, steps can be taken to avoid particulate inhalation from wildfire smoke exposure.

NIOSH recommends that persons working outdoors should don two-strap N95 particulate filtering facepiece respirators (which capture 95% of very small particles) or respiratory protection devices with a higher level of protection, such as a P100 respirator (which capture 99.97% of very small particles). A full list of NIOSH approved N95 masks listed by manufacturer can be found here.

NIOSH warns that respirators and surgical masks are designed for different functions, and do not provide the same types or level of protection. Paper “comfort” or “dust” masks commonly found at hardware stores are designed to trap large particles, such as sawdust (NIOSH 2017). Therefore, these masks will not protect your lungs from the small particles found in wildfire smoke.

According to NIOSH, you should limit the amount of vigorous activity outdoors when wildfire smoke is suspected. Individuals traveling in vehicles in the vicinity of wildfire smoke should close all windows and make sure air conditioning is set to ‘re-circulate’ mode (USEPA 2016).

Persons working in office and commercial buildings can also be exposed to the hazards of windborne wildfire smoke. Unlike in the home environment, where setting air conditioners to recirculation mode is advised, workers in office spaces or commercial buildings with HVAC systems are advised against eliminating or substantially reducing the outdoor air supply to the building (Cal/OSHA 2008). HVAC systems in office buildings typically filter and condition outdoor air, and often have exhaust systems that require makeup air from outdoors. HVAC systems should thus be operated continuously to provide the minimum quantity of outdoor air for ventilation in accordance with standards and building codes. According to California OSHA, to protect building occupants from outdoor air pollution, building managers and employers should ensure that the HVAC systems’ filters are not dirty, damaged, dislodged, or leaking around the edges, and make necessary repairs as required (Cal/OSHA 2008).  

Additionally, California OSHA encourages employers to take steps to reduce employee exposure to smoke, including, alternate work assignments and telecommuting. In buildings that lack a functioning filtration system that removes particulates from the air, employers are encouraged to provide relocation options for employees (Cal/OSHA 2008).

To get real-time data on current air quality in your area, visit the U.S. Environmental Protection Agency’s (EPA’s) Airnow.gov website. In addition, information is available from the CDC on protecting fire cleanup workers (here) and on well-being after a wildfire (here).

Cardno ChemRisk scientists have evaluated regulatory benchmarks and the underlying scientific literature regarding potential human health effects from particulate matter or other components of smoke, either from air pollution or wildfires. Cardno ChemRisk has a number of industrial hygienists and environmental health professionals who can assess exposure and risk of adverse health effects in specific settings. If you have any questions, or would like more information about our environment, health, and safety capabilities, please contact William Cyrs, CIH, at william.cyrs@cardno.com.