Canadian smoke drifts through the Midwest

Air quality in the upper Mississippi River Valley, tainted Thursday by north winds blowing in smoke from Canadian wildfires, worsened from moderately affected in the morning to just plain unhealthy by afternoon. By 6:30 p.m. the Air Quality Index (AQI) was rated at Unhealthy for Sensitive Groups.

Midwest smoke map 06/15/2023
Midwest smoke map 06/15/2023

According to the National Weather Service (NWS) and AirNow.gov, smoke from fires burning in Ontario — north of Michigan, Wisconsin and Illinois — is forecast to cause a mix of air quality conditions into at least Saturday.

As of 4 p.m. Thursday, the AQI for northwest Illinois and eastern Iowa showed pollutants hovering between the conditions of unhealthy for those sensitive to pollution and unhealthy for anyone in the population. The Sterling Daily Gazette reported that sensitive groups include people with respiratory conditions or heart or lung disease — as well as children, teens, and seniors.

Those at risk are advised to stay indoors or at least shorten the time they are active outdoors.

AirNow.gov air quality index and smoke drift map
AirNow.gov air quality index and smoke drift map 06/15/2023AirNow.gov air quality index and smoke drift map

The New York Times reported that smoke from Canada fires is returning to smoke-weary residents of New York; it’s expected to be heaviest on Friday morning, but forecasters said the region would be spared the orange haze that settled last week, when a thick plume of smoke choked the air in New York City, delaying flights, closing schools, and sending people to hospitals with respiratory issues. The NWS said smoke had temporarily settled in the Upper Midwest, causing unhealthy levels in much of Minnesota, including the Twin Cities.

NOAA satellite image 06/15/2023

Accu-Weather reports said Canadian smoke is now settling across the Midwest; it had started to drift over Minnesota and the Dakotas earlier in the week, and by Thursday morning, wind had carried high-altitude smoke as far south as Oklahoma and east to Pennsylvania and New York. The worst smoke stretched from southern Minnesota to central Ohio, and emergency room physicians and nurses cautioned those at risk to stay indoors if possible.

“With the air quality at its current levels, we are beginning to see a slight increase in emergency rooms visits for patients suffering from respiratory issues,” said Sarah Alvarez-Brown, director of Emergency Services and Behavioral Health at CGH Medical Center in Sterling, Illinois. “On average, 20 percent of emergency visits involve respiratory issues and difficulty breathing, but over the last couple of days, we have seen this jump to 30 or 40 percent of visits. No matter your age — from infants to older adults — if you have a pre-existing respiratory condition, asthma, heart or lung disease, or you are sensitive to changes in air quality, you may want to limit your time outside or stay indoors, in an air-conditioned or air-purified environment, until the smoke and haze pass.”

Check AirNow.gov for updates; the maps are interactive and can be zoomed or changed by zip code. Air quality levels are updated hourly.

Canadian smoke update

Residents of eastern Canada and the United States shared unhealthy air quality as hundreds of northern wildfires burn. On June 7, unhealthy to hazardous air advisories were issued for the capital cities of Ottawa, Ontario, and Washington, D.C., and for populations along the smoke paths.

The Fire and Smoke Map from AirNow offers an interactive map-based tool with local precautions. For Ottawa on June 7, AirNow sensors identified a hazardous air quality index (AQI) in the 400s for PM 2.5 (particulate matter that is 2.5 micrometers or smaller; the average human hair is 30 times larger than the largest of PM 2.5 particulates). Due to the hazard of such a PM 2.5 loading, an advisory was issued to avoid all outdoor physical activity.

AirNow sensors with unhealthy air quality from Ottawa, Ontario to Washington, D.C.
AirNow sensors with unhealthy air quality from Ottawa, Ontario to Washington, D.C. Current map at fire.airnow.gov

In Washington, the AQI was unhealthy on June 7, with advisories to keep outdoor activities short and light, and to go indoors if you have symptoms. Sensitive groups should consider moving all activities indoors.

By the evening of June 8, the plume of unhealthiest air had shifted predominantly to the Northeast coast. In New York City, producers cited the effects of smoke when cancelling two Broadway shows and a Shakespeare in the Park performance. On June 6, New York City Mayor Eric Adams cancelled outdoor school activities. “We are taking precautions out of an abundance of caution to protect New Yorkers’ health until we are able to get a better sense of future air quality reports,” he said. “We recommend all New Yorkers limit outdoor activity to the greatest extent possible. Those with preexisting respiratory problems, like heart or breathing problems, as well as children and older adults may be especially sensitive and should stay indoors at this time.”

AirNow map for evening of June 8, 2023.
AirNow map for evening of June 8, 2023. Source: fire.airnow.gov

To track smoke risk, the IQAir Earth Map and the associated World AQI Ranking offer another set of monitoring tools, based on their IQAir network. As of June 7, their World AQI Ranking listed New York City as #2 and Detroit, Michigan as #5 as global cities with the worst air, with Toronto as #15. By the evening of June 8, New York City had dropped to #6, Toronto to #10, and Detroit to #24.

IQAir Earth map for June 7, 2023. Current map at www.iqair.com/us/earth.
IQAir Earth map for June 7, 2023. Current map at www.iqair.com/us/earth.

in an article for The Conversation, Christopher T. Migliaccio, a research associate professor in toxicology at the University of Montana, wrote on smoke toxicity and precautions to consider when exposed to smoke:

If there is smoke in the air, you want to decrease your exposure.

Can you completely avoid the smoke? Not unless you’re in a hermetically sealed home. The PM levels aren’t much different indoors and out unless you have a really good HVAC system, such as those with MERV 15 or better filters. But going inside decreases your activity, so your breathing rate is slower and the amount of smoke you’re inhaling is likely lower.

We also tend to advise people that if you’re in a susceptible group, such as those with asthma, create a safe space at home and in the office with a high-level stand-alone air filtration system to create a space with cleaner air.

Some masks can help. It doesn’t hurt to have a high-quality N95 mask. Just wearing a cloth mask won’t do much, though.

The BlueSky Canada smoke forecast for June 8 through June 10 offers a specific two-day outlook that doesn’t promise an end to smoke, but indicates that the thickest production may alternate with lighter periods of smoke. By June 10, something like clear skies may appear over Detroit, and the thickest fingers of smoke, from the Quebec fires through Ottawa to New York City, will become more intermittent. A look at the timing of the heaviest smoke may help to plan outside activities during the hours of clearer air.

The BlueSky Canada forecast also shows continued fire and smoke in western Canada and Alberta.

The BlueSky Canada smoke forecast from June 8-10, 2023.
The BlueSky Canada smoke forecast from June 8-10, 2023. For current forecast: firesmoke.ca/forecasts/current/

Rain forecast for western Canada

Western Canadian communities and firefighters may catch a welcome break next week with a forecast for precipitation — perhaps a good amount. Over the next week, areas along the Canadian Rockies may receive more than 100 mm (3.9 inches) while the Alberta-Saskatchewan border area may receive 20 mm (less than an inch), with soil moisture predicted to rise throughout the fire-impacted areas. This will likely slow fire spread and smoke volume, though fires at such scale will continue to produce smoke. An overall increase in humidity should lower fire danger.

The western provinces have experienced weeks of active fire behavior and growth, with an intensity comparable to that seen in the 2016 fires that burned Fort McMurray, Alberta and the heat domes and fires of 2021, when fires burned Lytton, British Columbia.

Precipitation forecasts from the National Center for Environmental Prediction

Phys.org reported that some 2,500 firefighters from across Canada backed by 400 military personnel have been deployed across Alberta and that more foreign help has been requested — with crews and incident management teams from the United States, Mexico, Australia, and New Zealand.

At one point nearly 30,000 Alberta residents were evacuated from their homes. Hazardous air quality and low visibility due to smoke were reported from British Columbia to Saskatchewan and as far south as Colorado and northern Texas.

PM2.5 average05/21 map
PM2.5 average
05/21 map

Situation Reports – National

The home page of the Canadian Wildland Fire Information System features maps of weather, fire behavior, and hot spots.

The Canadian Interagency Forest Fire Center Situation Report for May 20 indicated area burned to-date of 2.1 million hectares (nearly 5.2 million acres), with 15 new fires for a total of 226 currently active fires. Of those fires, 90 are identified as out of control. Canada is in its tenth day at its highest preparedness level of 5.

Situation Reports – Provinces with highest fire activity

Climate Change and Fire

In the Climate Atlas of Canada, an article on “Forest Fires and Climate Change” examines the impacts of climate change on Canadian fires and summarizes studies by Mike Flannigan and other scientists who predict that by 2100, western Canada will see a 50 percent increase in the number of dry, windy days that let fires start and spread, whereas eastern Canada will see an even more dramatic 200 percent to 300 percent increase in this kind of fire weather.  And by 2040, fire management costs are expected to double.

Flannigan, a professor of wildland fire at the University of Alberta, explores the impact in more detail on his website. “Fire is the major stand-renewing agent for much of the Canadian forest,” he says, “greatly influencing forest structure and function.”

The research he summarized indicates that the observed increases in area burned in Canada during the last four decades is the result of human-induced climate change. Additionally, he says it appears that temperature is the most important predictor of area burned in Canada with warmer temperatures associated with increased area burned.

Based on a 2005 analysis, Flannigan says current estimates are that an average of over 2 million hectares burn annually in Canada. Just shy of the third week of May, Canada has already recorded 2.1 million hectares burned.

University of Oregon launches new smoke research center

The University of Oregon in Eugene is launching a new research program to study effects of wildfire smoke and examine options for reducing risks. UO research professor Cass Moseley told KGW News that the center’s launch is due in part to efforts by Oregon’s U.S. Senators Ron Wyden and Jeff Merkley, who secured $800,000 in funding from the U.S. Environmental Protection Agency.

Research will focus in part on new ways to protect homes from smoke infiltration, along with more efficient communication with communities in emergencies and developing community action plans tailored to different regions in the Northwest.

The new Wildfire Smoke Research and Practice Center builds on research already completed through the Ecosystem Workforce Program (EWP), a joint venture between the UO and Oregon State University. KLCC reported that the EWP’s senior policy advisor Cass Moseley will head up the new center; she said recent incidents in the Pacific Northwest, particularly the 2020 Labor Day fires, highlighted the need for new smoke research. Much of Oregon, particularly the southern Willamette Valley, was choked with wildfire smoke for weeks during the 2020 fire season.

Those fires and the severe levels of smoke really emphasized the need for new research, according to Moseley. “And we saw this fall in Oakridge, several weeks of highly dense smoke as the fire there settled into that valley and really stayed; that community spent a lot of time and energy responding to that smoke event.”

Cedar Creek Fire, October 2022
Cedar Creek Fire Incident Command Post in Oakridge, Oct. 15, 2022 — Inciweb photo

The center’s launch was announced by Merkley and Wyden, who secured the funding to help communities prepare for wildfire smoke. One area of interest is the toxins released when manmade structures burn, as these risks became obvious during western Oregon fires in wildland/urban interface areas over the last few years. Most smoke research has focused on burning timber and wooden structures, and part of the new planned research will study effects of smoke from burning plastics, glass, fuels, and other synthetic materials. Moseley said the center has three co-investigators and a principal investigator leading the group, along with research assistants and graduate and undergraduate student assistants.

Judge dismisses lawsuit over Oregon’s new heat and smoke rules

When local residents who aren’t firefighters see summertime haze or clouds on the horizon, they often guess it’s smoke. Mid-summer they often think it’s wildfire smoke, and in the fall they suspect it’s a prescribed burn. This is a “common experience” with wildfire smoke, according to attorneys with Oregon OSHA, who successfully argued last week that it’s fairly easy to determine when the air is smoky and affecting air quality.

On Tuesday, according to the Salem Statesman Journal, a federal magistrate dismissed a lawsuit against Oregon OSHA in which plaintiffs claimed the state agency’s new heat and smoke rules somehow violated the 14th amendment of the U.S. Constitution and were unenforceable. Lawyers for Oregon Manufacturers and Commerce, Associated Oregon Loggers, and Oregon Forest Industries Council claimed that air quality fluctuations are caused by many factors, and not just wildfire smoke.

“Most times, it’s not obvious,” attorney James Anderson declared. “There’s no method to determine that air quality is due to wildfire smoke, or prescribed burn smoke, or other things that make up particulates.”

Magistrate Mark D. Clarke was not persuaded. “Why is it that complicated?” he asked. He said Oregonians are quite familiar with wildfire smoke. “I’m not sure any of us have any trouble knowing when wildfire smoke rolls in. I’m having trouble with that, factually.”

The lawsuit also claimed that OSHA’s rules to protect workers against extreme heat and smoke were too vague to be enforced. The new rules, as KGW-TV reported last July, took effect after recent heat waves in Oregon resulted in medical problems and deaths, prompting new requirements for employers to protect employees from heat-related illnesses. The new OSHA rules require, when the heat index hits or exceeds 80 °F, that employers provide shaded areas for workers to rest, more break time, and access to plenty of water. When temperatures exceed 90 then breaks must be longer, communication must be more frequent, and workers must be monitored more closely.

Dangerous heat exposure is risky especially for farm workers, according to Ira Cuello Martinez, policy director for Pineros y Campesinos Unidos del Noroeste (PCUN), Oregon’s farm worker union. “You’re constantly moving and doing repetitive motions, having to bend down, and there aren’t many shaded structures when it comes to the field or doing work in agriculture,” he said.

Wildfire smoke alters immune cells, promoting inflammation

Smoke Beaver Fire
Smoke at the Beaver Fire in Northern California, August 12, 2014. Photo by Bill Gabbert.

Immune cells that normally protect against inflammation and infections can be altered by wildfire smoke to promote inflammation. A long list of diseases are associated with  inflammation. Studies have shown that healthy individuals and those with pre-existing conditions are affected by the very small PM2.5 particles produced by wildfire smoke.

forecast 4 a.m. PDT October 26 fire wildfire smoke
Forecast for the distribution of smoke at 4 a.m. PDT October 26, 2019 in the San Francisco area and south as far as Santa Maria.

Below are excerpts from an article written by Tori Rodriguez first published in Pulmonology Advisor. It covers the effects of smoke on humans and suggests what could be done to mitigate the potential damage. One idea is for fire and local officials when considering evacuation guidelines to plan for not only the dangers of flames, but also the effects of smoke.


[With wildfires increasing] and the health issues that result, there is a real and growing need for clinicians to educate at-risk patients, according to Jennifer Stowell, PhD, a postdoctoral researcher in the department of environmental health at the Boston University School of Public Health and co-author of a recent study on the health effects of wildfires.2 “For clinicians, education of patients is paramount, especially for those with already compromised health,” said Dr Stowell.

Healthy individuals may also experience health consequences from wildfires, according to Angela Haczku, MD, PhD, professor of medicine at the University of California, Davis, School of Medicine and director of the UC Davis Lung Center. “During the 2020 California wildfire season, my team conducted a study on healthy individuals and found alarmingly increased numbers of abnormal, activated immune cells in the peripheral blood.3 These cells are normally responsible for protecting against inflammation and infections, but when altered by inhalation of wildfire smoke, they become the ones promoting inflammation,” she explained.

Research exposes burning issues

The vast majority of recent US wildfires have been concentrated in western states, including Washington (218 fires), California (153 fires), Montana (141 fires), and Utah (130 fires).Estimates show that more than 70,000 wildfires have burned an average of 7 million acres in the US annually since the year 2000.4

In addition to this geographic damage, a sizeable body of research has detailed the negative human health effects resulting from exposure to wildfire smoke:

  • In a study published in June 2022, Heaney et al found that “smoke event” days —  those with the highest amounts of particulate matter 2.5 (PM2.5) from wildfires — were linked to increases in unscheduled hospital visits in California for all respiratory diseases (3.3%; 95% CI, 0.4%-6.3%) as well as asthma specifically (10.3%; 95% CI, 2.3%-19.0%), with the largest effect observed among children ages 0 to 5 years with asthma.2

Stratified analyses demonstrated increased visits for all cardiovascular diseases, ischemic heart disease, and heart failure among non‐Hispanic White patients and individuals older than 65 years. The findings further suggested that the interaction between wildfire PM2.5 concentrations and high temperatures may further increase the need for hospital visits among patients with cardiovascular disease.

  • A 2022 scoping review found evidence of increased population-level mortality, respiratory morbidity, and rates of various types of cancer in association with exposure to PM2.5 and chemicals from wildfire smoke.5
  • Findings from a 2021 study indicate that particulate matter from wildfire smoke has a greater effect on respiratory health than particulate matter from other sources of emission, based on a comparison of the increase in respiratory hospitalizations associated with increases in wildfire-specific PM2.5 (increase in hospitalizations ranging from 1.3% to 10%) and non-wildfire PM2.5 (increase in hospitalizations from 0.67% to 1.3%) in Southern California.6
  • Research published in 2021 showed that a 10 µg/m3 increase in wildfire PM2.5 was correlated with increased hospitalizations for all respiratory diseases, asthma, chronic obstructive pulmonary disease (COPD), and ischemic heart disease in Colorado. Wildfire PM2.5 was also associated with an increase in deaths due to asthma and myocardial infarction.7
  • Other results reported in 2021 linked wildfire PM.2.5 exposure in Alaska to elevated odds of asthma-related emergency department (ED) visits among various population, with odds ratios ranging from 1.10 (95% CI, 1.05-1.15) to 1.16 (95% CI, 1.09-1.23).8
  • A 2018 study analyzed data pertaining to 21,353 inpatient hospitalizations, 25,922 ED presentations, and 297,698 outpatient visits during periods of heightened smoke exposure from the 2007 San Diego wildfires. The results demonstrated a 34% increase in ED visits for respiratory diagnoses and a 112% increase in ED visits for asthma. Even greater increases in ED visits were observed among children aged 0 to 4 years with respiratory diagnoses  (73% increase) and in children aged 0 to 1 year with asthma (243% increase).9
  • Studies have also demonstrated increases in ED visits and hospitalization rates for asthma and other respiratory diseases in relation to wildfire PM2.5 in states such as Oregon and Nevada.10,11
  • Additionally, findings from multiple studies point to a potential connection between wildfire smoke exposure and higher rates of COVID-19 infection and associated mortality. In 1 study, researchers found that COVID-19 cases and related deaths increased by 56.9% and 148.2%, respectively, after the onset of the California wildfires that began in September 2020 compared with the period of time from the onset of the pandemic to just before the wildfires began.12
  • Results of another recent study suggest that “wildfire smoke inhalation sequesters activated, pro-inflammatory [natural killer] cells to the affected tissue compartments and may interfere with [COVID-19] vaccine effectiveness,” according to the authors.13

We interviewed Drs Stowell and Haczku to find out more about what clinicians need to know about the health effects of wildfires. Notably, Dr Haczku recently chaired the 2022 third annual NorCal Symposium on Climate, Health, and Equity.

“The size of the particulate matter is important….Particles larger than 10 micrometers in diameter are deposited in the nose, mouth, and upper airways, while PM2.5 is sucked directly down to the alveoli…causing disruption and inflammation.”
Dr Angela Haczku, Director of the University of California Davis Lung Center and chair of the 2022 NorCal Symposium on Climate, Health, and Equity.

What is known about the health effects of exposure to wildfire smoke?

Dr Stowell: Several studies have investigated the health effects of wildfire smoke and have linked smoke exposure to respiratory disease, cardiovascular disease, and birth outcomes such as preterm birth and low birth weight.14 Several gaps remain, including a better understanding of indoor air quality during wildfire events, the risk to outdoor workers, pregnancy complications, and mental health.

Dr Haczku: Wildfire smoke contains particulate matter of varying sizes, usually classified into PM10 and PM2.5 and ozone (O3) and nitrogen-containing toxic gases. All of these are combined with volatile organic chemicals that fuel the flames, the quality and quantity of which depend on whether what is burning comes from wild land, urban areas, or combined areas.

The size of the particulate matter is important because it determines where in the respiratory tract it will end. Particles larger than 10 micrometers in diameter (PM10) are deposited in the nose, mouth, and upper airways, while PM2.5 is sucked directly down to the alveoli, the tiny sacs responsible for our breathing, causing disruption and inflammation.

These particles are also carriers of inflammatory, allergenic, infectious, and toxic molecules causing both acute and chronic illnesses.

The most affected and best-studied organs susceptible to wildfire smoke are the respiratory tract and the cardiovascular system. Most ED visits are related to exacerbations of asthma and COPD and heart conditions such as coronary disease. Respiratory and cardiovascular mortality and hospitalization rates are well-known to be increased during wildfires. Affected adults and children also often suffer from anxiety and other mental health conditions. These conditions and the long-term health effects of wildfires are less studied and poorly understood.

What are the implications of these effects for health care systems?

Dr Stowell: Increasing wildfire activity due to climate change will continue to exacerbate these issues. Wildfire smoke exposure used to be thought of as an issue for the western US. However, as seen in the past several years, smoke from large fires and complex fires can reach across the continental US, exposing many individuals to harmful pollutants. Even with this wider spread of smoke, exposure will continue to have the greatest effect on the health of communities close in proximity to the fires, where smoke density is the heaviest.

Often the communities most affected are rural and face distance barriers to accessing proper health care. Thus, the health care systems in these already underserved areas could face capacity and response issues as wildfire smoke exposure continues to increase in western US states.

Dr Haczku: The effect of wildfire smoke on respiratory, cardiovascular, mental, and general health could be alleviated through specific interventions. As such, wildfire-related disasters provide health care systems with an opportunity to take a proactive role. Health care professionals should strategically and intentionally prepare for wildfire smoke events. Educational material should be prepared using professional society-approved guidelines and toolkits. These also need to be translated into the languages of and distributed to patients and potentially affected communities as well as the general public.

Having an efficient local system in place for timely warnings to reduce time spent outdoors during wildfire smoke events is crucial. Preventive measures in schools and indoor public places such as improved air filtration systems should be installed.

What are recommendations or considerations for clinicians to keep in mind when caring for patients in areas most affected by wildfires?

Dr Stowell: Education of patients is paramount. Some other steps could include considering temporary staff increases during wildfire seasons, ensuring the clinic staff are well-educated regarding wildfire smoke safety measures, and partnering with communities to provide clean air options for their patients.

Dr Haczku: In addition to intensive management of risk factors and chronic diseases, I believe implementing preventive measures are the most important. For example, professionals need to make sure that timely public warnings of smoke events are in place. Clinicians and health care workers should have a database that can be used to identify and reach out to vulnerable populations including pregnant women, children, the elderly, and farm and construction workers. Education of these communities and individuals can prevent emergency situations. Susceptible patients suffering from chronic illnesses and workers who cannot avoid outdoor activities may require help with fitting personal respirators and devices and specific consultation by health care workers.

What broader measures are needed to buffer the effects of wildfire smoke exposure and protect vulnerable populations, such as those with respiratory and cardiovascular diseases?

Dr Stowell: Much more needs to be done to plan for these large fire events. This planning includes focusing efforts in the areas most often affected by smoke through increasing health care system capacity, forming mobile health response teams, proper community education, better guidelines for evacuation (as most evacuations are intended to avoid the flames and not the smoke). Another need is access to clean air options, such as providing clean air centers and affordable access to air purification technology, including air conditioning and HEPA filtration.

Dr Haczku: As a health care educator, administrator, and climate change researcher, I see an urgent unmet need for the education of health care professionals about the effects of wildfires and, more generally, of climate change on human health. Vulnerable subjects, especially patients suffering from chronic health conditions, should be identified and educated. Improving advocacy toolkits and updating evidence-based professional guidelines for disease management and preventive interventions to reduce risk and protect health is imperative.

Research efforts to study and better understand wildfire smoke-induced pathologies as well as research to investigate the effectiveness of novel interventions should be better supported.

References

  1. Fire, Weather, and Avalanche Center. Current wildfires burning in the U.S. Accessed September 11, 2022.
  2. Heaney A, Stowell JD, Liu JC, Basu R, Marlier M, Kinney P. Impacts of fine particulate matter from wildfire smoke on respiratory and cardiovascular health in CaliforniaGeohealth. 2022;6(6):e2021GH000578. doi:10.1029/2021GH000578
  3. Teuber M, Flayer C, Linderholm A, et al. Wildfire smoke exposure activates circulating innate immune cellsJ Allergy Clin Immunol. 2021;147(2);Suppl_AB237. doi:10.1016/j.jaci.2020.12.012
  4. Congressional Research Service. Wildfire Statistics. Updated September 2, 2022. Accessed September 30, 2022.
  5. Grant E, Runkle JD. Long-term health effects of wildfire exposure: A scoping reviewJ Climate Change Health. 2022;6:100110. doi:10.1016/j.joclim.2021.100110.
  6. Aguilera R, Corringham T, Gershunov A, Benmarhnia T. Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California. Nat Commun. 2021;12(1):1493. doi:10.1038/s41467-021-21708-0
  7. Magzamen S, Gan RW, Liu J, et al. Differential cardiopulmonary health impacts of local and long-range transport of wildfire smokeGeohealth. 2021;5(3):e2020GH000330. doi:10.1029/2020GH000330
  8. Hahn MB, Kuiper G, O’Dell K, Fischer EV, Magzamen S. Wildfire smoke is associated with an increased risk of cardiorespiratory emergency department visits in AlaskaGeohealth. 2021;5(5):e2020GH000349. doi:10.1029/2020GH000349
  9. Hutchinson JA, Vargo J, Milet M, et al. The San Diego 2007 wildfires and Medi-Cal emergency department presentations, inpatient hospitalizations, and outpatient visits: An observational study of smoke exposure periods and a bidirectional case-crossover analysis. PLoS Med. 2018;15(7):e1002601. doi:10.1371/journal.pmed.1002601
  10. Gan RW, Liu J, Ford B, et al. The association between wildfire smoke exposure and asthma-specific medical care utilization in Oregon during the 2013 wildfire seasonJ Expo Sci Environ Epidemiol. 2020;30(4):618-628. doi:10.1038/s41370-020-0210-x
  11. Kiser D, Metcalf WJ, Elhanan G, et al. Particulate matter and emergency visits for asthma: a time-series study of their association in the presence and absence of wildfire smoke in Reno, Nevada, 2013-2018. Environ Health. 2020;19(1):92. doi:10.1186/s12940-020-00646-2
  12. Meo SA, Abukhalaf AA, Alomar AA, Alessa OM, Sami W, Klonoff DC. Effect of environmental pollutants PM-2.5, carbon monoxide, and ozone on the incidence and mortality of SARS-COV-2 infection in ten wildfire affected counties in CaliforniaSci Total Environ. 2021;757:143948. doi:10.1016/j.scitotenv.2020.143948
  13. Sanghar GK, Ravindran R, Teuber MJ, et al. Phenotypic evaluation of natural killer (NK) cells in response to BNT162b2 mRNA Covid-19 vaccine during wildfire smoke exposure. Presented at: the American Thoracic Society (ATS) 2022 International Conference; May 13-18, 2022; San Francisco, CA. Abstract A5407. doi:10.1164/ajrccm-conference.2022.205.1_MeetingAbstracts.A5047
  14. Evans J, Bansal A, Schoenaker DAJM, Cherbuin N, Peek MJ, Davis DL. Birth outcomes, health, and health care needs of childbearing women following wildfire disasters: An integrative, state-of-the-science reviewEnviron Health Perspect. 2022;130(8):86001. doi:10.1289/EHP10544