Besides the enormous environmental damage, it turns out that the smoke from the fires can be a carrier of disease-causing viruses and bacteria
By Omer Yerushalmi, Angle - a news agency for science and the environment
In recent weeks they broke out in Israel Man-made fires - partly due to deliberate arson and throwing Molotov cocktails, and they exacted a heavy price from nature and agricultural areas as well. As we know, fires have consequences in property and in the soul, and they emit smoke that may even reach a distance of thousands of kilometers and cover Whole cities for weeks. However, the risk caused by them does not end there. BNew American review article, recently published in the prestigious scientific journal Science, researchers warn of another risk - diseases that are spread through the smoke of the fire.
Every year in Israel over 30 thousand Fires in open areas. According to An article published in the journal "Ecology and Environment" in 2018, almost all fires in Israel are caused due to negligence or malice by humans (for illustration, only 8 of all the fires recorded in the first decade of the 21st century were caused by lightning - less than 0.05 percent of the fires). The cost of putting out an average fire alone is about NIS 18,400 - and of course many additional costs are added to it, such as the cost of the fire's damage to public health.
In the new review article, the researchers base on Their previous study from 2020, where they tried to examine whether and to what extent fires are a source of emission of bacteria into the atmosphere. The researchers hypothesized that during the burning process, bacteria that were present in the vegetation and soil are released and adhere to the tiny soot particles.
The researchers examined the composition of bacteria carried in the smoke of 8 relatively small fires in natural areas in North Florida. They compared the findings with the composition of bacteria that was in the air in that area before the fire broke out.
The findings of the study were unequivocal: in the smoke samples a concentration of bacteria was found 5 times higher than that found in the air before the fire. A controlled burning of vegetation in the laboratory also produced a similar result.
The relative increase in the amount of bacteria due to the fire raised the amount above the threshold that could endanger healthy people: in a cubic meter of smoke, the researchers found 67 thousand cells of microorganisms (mainly bacteria and fungal spores) - A concentration higher than the minimum concentration which may cause a reduction in respiratory function and the development of diseases in humans, and which amounts to between 10,000 and 100 cells of fungal and mold spores per cubic meter.
Increase in hospitalizations after fires
In the review article, the researchers also draw attention to previous findings that showed an overlap between exposure to smoke after fires and cases of diseases of fungal origin. Thus, bstudy Before 2019, the amount of hospitalizations due to systemic fungal infection (Invasive Fungal Infection) was examined in 22 hospitals in California. The study found that between the years 2018-2014, during the fire season, there was an increase in the number of hospitalizations in hospitals located within a 300 kilometer radius of the fire's epicenter (it should be noted that other seasonal factors, besides the fires, may be involved in the increase in morbidity observed in the study).
The same study also found an increase in the frequency of hospitalizations in the examined hospitals due to diseases caused by exposure to two types of mushrooms found in nature: Aspergillosis (Aspergillosis spp.), which is found on dead leaves and compost and can cause pneumonia and sinus infections (especially in those with a weak immune system), andCoccidioides spp., which is found in the roots in the ground and can cause valley fever, a lung disease with characteristics similar to pneumonia and throat infection. It should be noted that fortunately, these two mushrooms are not common in Israel.
In the review article, the researchers offer several explanations for the presence of the many fungi and bacteria in smoke. One possibility is that the bacteria and fungi that are carried up by the smoke survive in the parts of the fire area that the fire does not reach (a kind of "fire baldness"). Another possibility is that they even come from surfaces that are around the fire. According to the researchers, the fire creates vortices of hot air, and the air is strong enough to detach microorganisms from the vegetation and soil and sweep them upward into the smoke. Likewise, it is also possible that these are pieces of organic matter from the plant or the soil that are covered with bacterial encrustation (biofilm) that were burned from the outside, but in their interior remained temperature and humidity conditions that allowed the bacteria to survive.
Not every fire spreads bacteria
It should be noted that the level of risk posed by the microorganisms in the smoke of the fires depends on the level of sensitivity of the population that is exposed to them. According to the article, sensitive populations are at increased risk due to the bacteria and fungal spores in the smoke, as are firefighters, who are exposed to smoke for a long time. "These fungal infections are usually typical of a population that has previous immunological problems - asthma, allergies, etc., unless there is a very prolonged exposure to very high concentrations," says Dr. Isabella Karkis, director of the Department of Environmental Epidemiology at the Ministry of Health.
An examination of the background conditions for fires in Israel slightly reduces the fear of diseases in the country. "During the fire, water that is in the vegetation evaporates into the air," explains Karkis. According to her, this water joins the water that is naturally in the air in the form of moisture, and together they connect to the organic matter that was burned and that is in the smoke. "Together, they are a source of energy - food - for those microorganisms."
"When there is a lot of water, microorganisms have an infrastructure to live, but except for the coastal plain, the humidity in Israel is not that high relatively - and there are not many forests in the coastal plain," says Karkis. "The amount of trees in the country is also not large enough."
The risk from the fire also depends on its size. Small, local fires do not cause a particularly high risk - while a large fire, which may last for weeks and the smoke emitted from it is transported to a distance of thousands of kilometers and may cover entire cities for a long time, (such as the fires that occur every year in the Amazon and eastern Australia) may endanger those in the risk groups. Fortunately for us, the orders of magnitude of the fires in Israel are much smaller.
An increase in the frequency and intensity of fires
Risks such as the one presented in the new study have additional importance due to the fact that humans are partly responsible for the increase in frequency and intensity of fires. Due to the climate crisis, the frequency and intensity of extreme climate events are increasing, and fires of an intensity previously seen only once a century may occur Almost every year until the end of the 21st century. Therefore, according to the researchers, it is important to fully understand the causes and the epidemiological risks involved in fires.
The diseases that can be caused by the presence of microorganisms in the fire smoke add to the known negative health effects of the fire smoke, which contains fine respirable particles which may damage the respiratory system, as well as dangerous compounds such as carbon monoxide and nitrogen and sulfur oxides.
"It is important to understand the significance of the effects of the bacteria and fungi when they are added to the chemicals in the smoke," concludes Karkis. "There are many conditions that may affect the type of diseases that will be caused, who will get them and with what intensity, and which still need to be investigated. The connection between epidemiology and fires must be considered."
