Particulates in Wildfire Smoke Activate Immune Cells to Increase Disease

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, Wildfire Today reports. And studies have shown that healthy individuals as well as people with pre-existing conditions are affected by the very small PM2.5 particles produced by wildfire smoke.

In late October, Wildfire Today published the following excerpts from a post 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 to plan for the effects of smoke as well as the dangers of flames when they’re working on wildfire evacuation guidelines.

With wildfires increasing and the health issues that result, Rodriguez wrote, 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.“For clinicians, education of patients is paramount, especially for those with already compromised health,” said 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,” she explained. “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.”

Research Exposes Burning Issues

The vast majority of recent U.S. 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 seven million acres in the U.S. per year since 2000.

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, and specifically asthma, with the largest effect observed among children with asthma aged 0 to 5 years.

Stratified analyses demonstrated increased visits for all cardiovascular diseases, ischemic heart disease (narrowing of the arteries), 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.

• 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.

• Research published in 2021 showed that an increase in wildfire PM2.5 of 10 micrograms per cubic metre (10 µg/m³) 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 (heart attack).

• Other results reported in 2021 linked wildfire PM.2.5 exposure in Alaska to higher odds of asthma-related emergency department visits among various population.

• A 2018 study analyzed data pertaining to 21,353 inpatient hospitalizations, 25,922 emergency room 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 emergency visits for respiratory diagnoses and a 112% increase for asthma. Even greater increases in emergency room 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).

• 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.

• Findings from multiple studies also point to a potential connection between wildfire smoke exposure and higher rates of COVID-19 infection and associated mortality. In one 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 between the onset of the pandemic and just before the wildfires began

• 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.

Wildfire Today has an interview with Stowell and Haczku and full references for the post.