January 21, 2025
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Book review: The threat of small airlifts and human reluctance to face it
Carl Zimmer’s new book delves deep into aerobiology and why humans seem unwilling to confront the threat of airborne transmission

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nonfiction
Air-Borne: The hidden history of the life we breathe
Written by Carl Zimmer.
Dutton, 2025 ($32)
The air around us is more alive than we think. What appears to be a hollow space in between is actually an extensive ecosystem inhabited by life-producing cells and the smallest scale organisms, from fungal spores to plant pollen. We breathe in and exhale a variety of living things, until the devastation of COVID-19 reminded us of the complex intimacy between humanity and our so-called aerobiome. I often did this without even realizing it.
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The difficulty of directly observing life in the air has long shrouded its study in mystery and kept the body of knowledge inert, explains journalist Carl Zimmer in his new book. Air-Borne: The hidden history of the life we breathe. Aerobiologists who think of the atmospheric environment as a habitat often lament that its biodiversity is invisible. However, this field has not always been undervalued.
Air once dominated Western science. Zimmer charts the vagaries of biological and medical knowledge. There, wild dissent can be accepted as scientific fact and then relapse into obscurity. The miasma theory, which dates back to the writings of Hippocrates in the 5th century BC, survived through the conservation labor of Syrian monks and became an explanation for widespread disease in medieval Europe. The “bad air” from putrefaction enters the body and destroys body fluids, causing diseases from cholera to tuberculosis. This theory persisted long into the 19th century, when hygienists including Florence Nightingale tried to prevent disease by changing hospital bedding and opening windows to eliminate putrid odors.
But the germ theory was on the rise. After Antony van Leeuwenhoek invented the microscope in the late 1600s, scientists could more easily observe microorganisms everywhere, including in the air. In the late 1800s, Louis Pasteur became obsessed with showing how far microorganisms travel. He also climbed the Alps to collect air samples. Emerging epidemiologists believed that bacteria, not smoke, caused the disease.
This development has disappointed the medical establishment, which branded epidemiologists as “drinking water believers” and dismissed evidence that comma-shaped bacteria were behind the cholera outbreak. Zimmer describes the long, heated, and ultimately tragic battle between the germ theorist Robert Koch and the miasmalogist Max von Pettenkofer in the 1880s as an example of aerobiology in modern medicine. It was set up as a showdown that led to its decline.
However, the fall from prominence did not mean the end of the activities of scientists interested in airborne objects. Zimmer chronicles the multigenerational resurgence of a nearly lost science in exhaustive detail and impressive breadth. In the early 20th century, when American farmers were suffering disastrous crop losses from wheat rust, the U.S. government became interested in investigating the spore’s aerial range. Plant pathologist Fred Meyer, a former watermelon expert, led the research, sometimes collaborating with Charles Lindbergh and Amelia Earhart, and took air samples in high-flying petri dishes.
Meyer’s leadership would eventually be taken over by William Firth Wells, a former water and health scientist. He developed an air centrifuge to capture pathogens, reusing his attempts to regenerate oyster populations with filtered eggs. It was largely the tireless work of Wells and his wife, physician and epidemiologist Mildred, that propelled the science of airborne organisms throughout the 20th century. The path was not easy for the Wellses, as the medical establishment did not welcome the idea of pathogens traveling long distances through the air in conditions that were not easily controlled.
But, as Zimmer skillfully shows, the world had changed so much that the revival of aerobiology seemed destined. World War II, the Cold War, and the post-9/11 era have fostered the delusion that the enemy is everywhere, and what could be scarier than invisible airborne toxins and viruses? World-wide testing of released biological weapons and the creation of larger and more deadly “infection machines” became possible. Zimmer writes about alarming exposures to deadly pathogens that were not necessarily intentional or spontaneous.
This fear about the proliferation of human-made biological weapons turns out to be less justified than worries about naturally occurring diseases, such as the SARS and H1N1 epidemics of the early 21st century. The era of rapid economic and social globalization and the expansion of dense, densely populated cities have made research into airborne pathogens even more urgent.
But even though DNA sequencing and the use of improved computer models have helped confirm the reality of airborne transmission, authorities have often seemed reluctant to address it. Zimmer discusses the institutional obstacles the Wells faced and the challenges faced by the rebellious scientists, who call themselves Group 36, during the recent coronavirus pandemic. So it combines political pressure with inconsistency and lack of clarity from the World Health Organization. Air transport This shows how difficult it is to coexist harmoniously with a sea of invisible microbes in the air, but a greater threat to our existence may come from our own narrow-minded thinking. Zimmer argues that it can’t be done.
