RESPIRAR data analysis reveals poor indoor air quality spikes in farmworker housing during Canada’s 2023 wildfire
An orange haze engulfs Greenbelt, Maryland, during a Canadian wildfire smoke episode on June 7th. Attribution: Photograph by Colin Seftor (NASA/SSAI). Public domain, via Wikimedia Commons
Last summer, RESPIRAR air quality monitors detected dangerous levels of indoor air pollution in migrant and seasonal farm labor housing on the Eastern Shore. Our data highlights the severity and far-reaching effects of wildfire smoke — especially when compounded by a preexisting poor baseline of indoor air quality.
As wildfires grow in size, frequency, and intensity, we must prepare for a future in which wildfire smoke will increasingly affect indoor and outdoor air quality. Wildfire smoke exposure, in particular, is expected to become a more frequent occurrence as wind patterns carry smoke across state lines, affecting regions far removed from the source.
The public health implications are of national concern. Millions of people, including communities in areas typically unaffected by wildfires, are now at risk.
Maryland felt the burn last summer
In June 2023, Marylanders experienced an eerie preview of a future where regional wildfire smoke episodes might become more common. When a lightning strike ignited wildfires in an unusually dry, forested region in Quebec, wind patterns blew the smoke thousands of miles away, down the Chesapeake Bay, covering the region in an ominous orange haze.
Canada's wildfire caused Maryland's air quality to approach unprecedented levels of air pollution and prompted government officials to issue alerts. Wicomico County Health Department advised the general public to minimize time outdoors. Montgomery County joined other regions and canceled outdoor activities for public schools. Governor Wes Moore urged Marylanders to stay indoors:
"Marylanders should consider limiting time spent outside and avoid prolonged or heavy exertion until air quality improves," said Moore in a statement. "The health and safety of Marylanders is our top priority."
Wildfire smoke, particulate matter, and worker safety
Air quality alerts often spike during wildfire episodes due to a complex mixture of gases and compounds, including fine particles with a diameter equal to or less than 2.5 micrograms. These tiny particles, known as particulate matter (PM) 2.5, can pose serious respiratory and cardiovascular health risks when inhaled, increasing susceptibility to respiratory viruses like COVID-19 and the flu.
A study completed in 2021 found that wildfire-specific PM2.5 is up to 10 times more harmful to human health than PM levels from other sources. During wildfire smoke episodes, this toxic matter can spread thousands of miles and is farther-reaching than other sources of air pollution.
As wildfires become more frequent, the need for preparedness among employers and workers is becoming increasingly urgent. During the Canadian wildfire in June, the US Department of Labor issued a statement urging employers to develop plans protecting outdoor workers from poor air quality.
Project Coordinator, RESPIRAR
"Wildfire smoke exposure can create major health hazards for outdoor workers. These hazards can be reduced with knowledge, safe work practices, and appropriate personal protective equipment,” said Doug Parker, Assistant Secretary for Occupational Safety and Health. “I urge all employers to have plans and preparations in place to protect workers by preventing or minimizing exposure to hazardous air quality.”
The Department of Labor and Occupational Safety & Health Administration (OSHA) also listed protective measures to reduce smoke exposure for outdoor workers, including requiring and encouraging workers to take breaks in smoke-free locations and providing NIOSH-approved respirators for voluntary use. These recommendations are not federally mandated, and to date, California and Oregon are the only two states with rules regulating on-the-job wildlife smoke exposure.
RESPIRAR monitors detect harmful indoor PM2.5 levels
Two RESPIRAR indoor air quality monitors were active in May and June 2023: one in a home rented to eight farmworkers near Salisbury and another near College Park for comparison. Our research team monitors indoor air quality in farmworker housing because healthy indoor air reduces exposure to respiratory viruses, including COVID-19 and the flu. As the team tests participants for COVID-19, among other viruses and cases of flu, we can compare test results with the farmworker indoor housing air quality results to find patterns.
Our team uses the Awair Omni air quality monitors to measure carbon dioxide, humidity levels, PM 2.5, temperature, and total volatile organic compounds. The varying types and levels of pollutants indicate air quality. To better understand how the Canadian wildfire affected indoor air quality, we looked at the PM 2.5 levels throughout June. We compared these levels with the values of federal outdoor standards and the associated Air Quality Index or AQI.
Indoor air pollutants are not federally regulated under the Clean Air Act and, therefore, federal guidelines and AQI values for indoor air quality do not exist. Many states, including Maryland, prohibit smoking in most indoor workspaces. California and New Jersey are the only states with indoor air regulations.
The AQI is a tool for communicating outdoor air quality with the public. It is calculated for four major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate pollution, carbon monoxide, and sulfur dioxide. Our team used the indoor particulate matter levels to derive AQI values, which were developed with the public health implications of outdoor air quality.
“The AQI was established for communicating outdoor air quality, including levels of particulate matter,” said Dr. Devon Payne-Sturges, co-director and lead researcher for the RESPIRAR Project. ”But we can and should apply that same approach to indoor particulate matter levels.”
During the wildfire smoke episode on June 7th and 8th, the Salisbury monitor documented significant PM2.5 spikes, with 24-hour averages exceeding the EPA 24-hour standard by 194% on the 7th and 145% on the 8th. Meanwhile, Maryland's Department of Environment recorded the highest particulate matter incident in the state's history on June 8th, nearly reaching a “very unhealthy” code purple, indicating conditions pose a health risk to the general population.
Marylanders experienced a brief reprieve from the smoke until wind patterns changed again on June 29, prompting a code red “unhealthy” air quality alert across the state. By midnight on June 30, the wind blew the wildfire smoke back to Salisbury. At this time, the RESPIRAR indoor monitor detected an hourly PM2.5 average spike of 109 micrograms per cubic meter of air (μg/m3), an hourly value 211% greater than the EPA 24-hour standard.
“The real-time data we collected signaled that the wildfire smoke was pretty evident. This shows how outdoor air can influence indoor air quality,” said Dr. Payne-Sturges.
Healthy indoor air quality is vital during wildfire smoke episodes to help limit overall smoke exposure. Outdoor workers, in particular, are at higher risk of adverse smoke-related health outcomes and need reprieves from the smoke.
Particulate matter spikes outside of wildfire incidents
RESPIRAR’s data analysis also shows how wildfire smoke can compound with pre-existing poor indoor air quality to create unhealthy living environments. This underscores the influence outdoor air quality has on indoor environments, particularly during extreme events like wildfires.
Air quality data from the same housing location near Salisbury show hourly PM2.5 levels reaching and exceeding those documented during the wildfire episodes. For example, on June 14, hourly indoor AQI values reached “very unhealthy” code purple levels. Throughout June, the 24-hour average indoor AQI spiked to code orange and red values 17% of the time in Salisbury, compared to 10% in College Park.
These spikes may be due to neighbors openly burning trash nearby. RESPIRAR staff and participants anecdotally observed these open burning incidents, which were informally documented as part of the study and, therefore, remain inconclusive.
Open-air burning is permitted in Maryland and regulated by the state’s Forest Service. Some Eastern Shore residents resort to open burning when trash collection services are not provided, and transportation to dumps is not a viable option.
Maryland Forest Service attributes 35% of ignited fires to improper debris or outdoor burning.
The world must 'learn to live with fire'
A 2022 UN Environment Programme report estimates that extreme fire incidents worldwide could increase by 15% by 2030, 30% by 2050, and 50% by 2100, emphasizing that the world must "learn to live with fire." As wildfires grow in frequency and intensity, safeguarding worker health becomes crucial, even in communities like Maryland that have historically been unaffected.
Following last summer's wildlife smoke episodes, RESPIRAR Project Coordinator Stephanie Hernandez spoke with workers about their experiences.
Despite the air quality alerts and visible smog, "everyone I spoke with confirmed that they worked during the wildfire smoke incidents," said Hernandez. "Their employers did not mention the wildfires or share recommendations for safety during the incidents."
Better communication and worker protection are essential. Safety protocols should include PPE equipment, reduced physical activity levels, smoke-free breaks, and access to indoor environments that protect workers from smoke.
In April 2024, a neighbor appears to be engaged in open burning practices across the street from a farmworker housing facility near Salisbury. Ongoing open burning incidents may explain particulate matter spikes at this location that fell outside the Canadian wildfire episodes.
RESPIRAR’s outreach team provided workers with masks, but many seemed unconcerned and did not wear them, reflecting a broader cultural norm that prioritizes work over safety.
"The priority for workers and employers is to make money, not health, so it is normalized to work in any condition until health concerns are prompted by employers," said Hernandez.
Until regulations are in place, workers and employers can sign up to receive real-time air quality conditions and forecasts on their smartphones through the Clean Air Partners and AirNow apps.
When the outdoor air quality index reaches orange (unhealthy for sensitive groups), red (unhealthy for everyone), or purple (very unhealthy) levels, employers can provide workers with N95 masks.
Healthy indoor air quality can be achieved through high-efficiency particulate air (HEPA) cleaners, air filters for window air conditioning units, and proper maintenance of central air conditioning and HVAC systems. Download our infographic exploring how workers and housing managers can maintain healthy indoor air quality.
Employees and employers can also refer to OSHA’s wildfire educational materials to learn more about workers’ rights and safety measures during wildfire episodes, as well as their information on indoor air quality.