New research has found that smoke from biomass burning that has gone through a chemical aging process is more harmful to lung cells than the original smoke.
Biomass burning – the burning of living and dead vegetation – includes wildfires, wood burning and the burning of vegetation for crop clearance. Humans are thought to be responsible for about 90% of the total amount of vegetation burned.
Some chemicals or compounds found in the smoke from biomass burning act as markers of that smoke, that is they can be used to identify its presence or track where it has spread. With biomass smoke, one of these is levoglucosan, a sugar-like compound produced when wood burns.
As the smoke lingers in the air and reacts with pollutants like nitrogen oxides (NOx), it can form other chemicals, such as 4-nitrocatechol and recent research suggests that these chemical changes in the smoke may be even more harmful to health than the particles that were originally released.
The researchers worked with two types of lung cells: BEAS-2B cells, which represent healthy cells from the lining of the lungs, and A549 cells, which come from lung cancer tissue and are often used to study respiratory health.
They exposed both types of cells to different amounts of levoglucosan and 4-nitrocatechol for 24 and 48 hours. Afterward, they checked how many cells survived, looked for signs of stress, and examined any damage to the mitochondria — the parts of the cells responsible for producing energy.
The team reported their key findings as:
- 4-nitrocatechol was significantly more toxic to lung cells than levoglucosan. At relatively low doses, 4-nitrocatechol reduced cell survival and caused oxidative stress—an imbalance that damages cells and can lead to lung diseases.
- Exposure to 4-nitrocatechol disrupted the function of mitochondria in lung cells, leading to a process called apoptosis, or programmed cell death. This damage could contribute to long-term lung problems.
- While levoglucosan exposure also led to cellular stress, its effects were much less severe compared to 4-nitrocatechol. Cells exposed to levoglucosan showed signs of mitochondrial stress, but they were able to recover over time.
It was also noted that people exposed to biomass smoke may face an elevated health risk in urban areas, where NOx is more prevalent.
Co-author of the study, Dr. Jason Surratt, a professor in the Department of Chemistry at University of North Carolina at Chapel Hill, said: ‘Our study reinforces concerns that exposure to biomass smoke—especially aged smoke containing 4-nitrocatechol—can have serious health consequences.
‘Long-term exposure to these pollutants has been linked to respiratory diseases such as asthma, chronic obstructive pulmonary disease and lung cancer. People who live in wildfire-prone areas or who frequently burn wood for heating should take extra precautions.’
The full study can be read here.