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Photo Source: Unsplash when we repeatedly emphasize the PM2.5 caused by wildfires, there are more health risks hidden in the smoke.

One early morning in December, Jesse Merrick finally got through to his mother, who burst into tears when their home was torched in 2017 when the Thomas Fire fire in Southern California destroyed more than a thousand acres of land.

Merrick quickly returned to his former home and spent several days in the charcoal-burnt basement, trying to find anything that might survive. Merrick specially wore masks and gloves, but the equipment failed to ward off the lurking danger.

Three weeks later, when Merrick flew back to his home in Alabama to get back to work, there seemed to be something wrong with his health. At first it was just a low fever, cough, aches and pains and a mild rash. But as his condition worsened, bruises began to appear around his joints, "like being beaten with a bat." He also has pneumonia, which makes it painful to breathe.

Soon, Merrick's primary care doctor discovered that his lungs had grown a lump 6 centimeters in diameter. The doctor decided to perform a tissue biopsy and spinal puncture to determine the possibility that Merrick was most worried about-cancer. But on the morning of the day of the operation, a team of infectious disease experts came to the ward and they brought Merrick the diagnosis.

The power of fungi in fact, Merrick's lung lump is not a tumor, but a fungal ball.

Merrick's disease, known as valley fever (valley fever), is caused by a fungus, Coccidioides, that infects people's lungs. Doctors injected him with fluconazole, an antifungal drug, and Merrick soon got better.

There are two kinds of coccidiosis that can cause valley fever, one of which is C. immitis (photo source: wikipedia / Public Domain) Valley fever is not a rare disease. In the southwestern United States, there are at least tens of thousands of cases of valley fever every year. In hot, dry climates, the spores of coccidiosis (germ cells of fungi) in the local soil spread into the air and are inhaled into the lungs. But 60% of the patients have no symptoms, or only mild symptoms such as fatigue, cough and fever, which can easily be mistaken for a cold or flu. However, if the infection continues to worsen, or even spread to other parts of the lungs, it is easy to cause multiple organ failure, resulting in the death of patients.

With climate change, Arizona and California are drier and hotter, and coccidiosporidium spreads more easily. The number of cases in California increased at least eightfold from 2000 to 2018, according to a study.

But some scientists suspect that the increase in the number of cases is related not only to climatic conditions, but also to the increasing frequency of wildfires.

Hidden threat of wildfires in 2019, a team of researchers at the University of California, San Francisco found that some cases of fungal infections seemed to be associated with wildfires. If a wildfire breaks out within about 300 kilometers of a hospital, there appears to be a significant increase in cases of fungal infections such as valley fever in the following months.

Photo Source: Unsplash now, more and more scientists suspect that wildfire smoke carries more disease-causing microorganisms in addition to the air pollution particles (PM2.5) we are familiar with. Not only fungi such as coccidiosporidium, but bacteria, archaea and even viruses can rise into the air with wildfire smoke and spread further away.

Leda Kobziar of the University of Idaho has also established a new discipline, Fire Atmospheric Biology (pyroaerobiology). The focus of their research is microbes in the smoke of wildfires.

Artificial snow to artificial fire sounds strange, but Corbuzier's original research on the atmospheric biology of fire was inspired by artificial snow.

The freezing point of purified water is close to 40 ℃ below zero. Only when there are tiny suspended particles in the water, the freezing point of water will be close to 0 ℃. These particles, called condensation nodules, are the central nuclei of ice crystals.

At present, one of the best clotting nodules is a protein produced by Pseudomonas clove (Pseudomonas syringae). Most snow machines add this bacterial protein to the water to ensure that tiny droplets solidify in front of the contact ground.

Of course, the bacteria died long before the snow began, but the microbes in the smoke may still be alive. "I began to understand smoke in the same way, and I wanted to know if there were living bacteria in the smoke." Kobuziar began to think, "some wildfires produce very unique smoke. could these bacteria be the cause?"

Subsequently, Kobuziar and his colleagues conducted a series of verification experiments. They took some ground samples from the forests of Idaho, including soil and litter, and burned them in the laboratory, and found a large number of traces of microbes in the smoke.

Stronger evidence comes from data obtained at the scene of a wildfire in Florida. This is thanks to Florida's "prescribed burn" policy. In some areas prone to wildfires, relevant government departments will light fires regularly, triggering a small-scale and controllable "artificial wildfire", which is called "controlled incineration". Controlling incineration can not only remove combustibles from the surface, but also contribute to the growth of some tree species and effectively reduce the risk of wildfire.

Such controlled incineration provides an excellent opportunity for the research team to collect local air samples as a control before controlling the incineration. After the hill fire is ignited, samples can be taken continuously at different times and locations, so as to obtain the most intuitive data.

The results of fire atmospheric biology experiments are very consistent with their hypothesis that there are a lot of microbes living in the smoke. Even in this less intense "controlled incineration", the average number of microbial cells in the smoke can reach 67, 000 per cubic meter, about five times that of the air before the fire (13, 000 per cubic meter). Considering that the "control incineration" operation controls the incineration method and scale, and minimizes the pollutants produced by the fire, the number of microbes in the smoke is likely to be higher in a real wildfire.

At the same time, as the sampling site moves away from the smoke source, the microbial abundance is positively correlated with the concentration of particles in the smoke-suggesting that the extra microbes are likely to be sent by the smoke.

A model of microbial concentration change in smoke, in which the color represents the number of cells per kilogram (image source: L. N. Kobziar & G. R. Thompson, 2020) Corbuzier speculates that microbes from soil and litter are released into the air in large quantities during raging wildfires. And even outside the burning zone, wildfires can trigger massive updrafts, allowing fungal spores in the soil to be sucked into the plume and eventually into the smoke.

Like PM2.5, these microbes in smoke form aerosols. Once aerosol is formed, microbes with aerodynamic diameter less than 5 μ m may spread hundreds of kilometers along with the smoke, becoming a health threat that many people do not notice.

Given the higher concentration of microbes in the smoke near the source of the fire, those who are long-term and close to the smoke may be more affected, first and foremost by firefighters on the front lines of the fire. At present, CDC in the United States has listed firefighters as high-risk occupations of Valley Fever.

However, it is worth mentioning that although some data show that the increase in wildfire smoke in the western United States is related to cases of fungal infections, there is still no direct and conclusive evidence that wildfire smoke can lead to infections of diseases such as valley fever-which is what Kobuziar is eager to know.

Image: in Unsplash2021, the University of Florida set up a fire atmospheric biology research program, and many researchers, including Corbuzier, are further exploring the microbial composition of smoke and trying to stack the range of past wildfire smoke with digital medical records to understand the risks it may pose.

This will be the first project in the field of fire atmospheric biology. Two basic questions await the researchers: "how long can these microbes survive" and "how far can they spread?" Starting from these two issues, the team will continue to understand how they will affect humans, animals and plants, and the broader climate.

Reference:

Https://www.science.org/doi/10.1126/science.abe8116

Https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.2507#ecs22507-bib-0009

Https://www.nature.com/articles/s41396-020-00788-8

Https://www.cdc.gov/niosh/topics/valleyfever/risk.html

Https://www.wired.com/story/valley-fever-is-spreading-through-a-hotter-drier-western-us/

Https://www.wired.com/story/wildfire-smoke-may-carry-deadly-fungi-long-distances/

Https://www.popularmechanics.com/science/environment/a30246543/pyroaerobiology-smoke-signals-interview/

Source: science Popularization China-Star Project (creation and cultivation)

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by: 27, revision: Clefable

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