William Firth Wells and Mildred Weeks Wells

Summary

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Stuff You Missed in History Class

Episode: William Firth Wells and Mildred Weeks Wells
Hosts: Tracy V. Wilson and Holly Fry
Date: September 10, 2025

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Episode Overview

This episode explores the groundbreaking but underrecognized work of William Firth Wells and Mildred Weeks Wells, a husband-and-wife scientific team who conducted pioneering research on airborne disease transmission and indoor air safety in the early to mid-20th century. Their studies—spanning inventions, experiments, and practical interventions—laid foundational concepts for understanding how illnesses like tuberculosis, influenza, measles, and more spread through the air. The hosts examine both the couple’s scientific contributions and the social and institutional factors that hindered the adoption of their ideas—limitations with major implications during pandemics such as COVID-19.

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Key Discussion Points & Insights

1. Setting the Scene: Frustration and Missed Opportunities

• Tracy describes being frustrated while listening to a modern podcast about the history of airborne research, discovering that key ideas dated back to Wells and Weeks in the 1930s/40s (05:14).
• She notes: their research "could have really lessened the impact of the COVID-19 pandemic" had it been more widely accepted early on.

2. Mildred Weeks Wells: Early Life and Education

• Born 1891 in Indian Territory, into a prominent but troubled family dogged by rumor and scandal (06:06).
• Earned her MD in 1915, one of only three women in her class of 34; started career at the U.S. Public Health Service Hygienic Laboratory (08:04).

3. William Firth Wells: Early Life and Career

• Born 1886 or 1887 in Boston, bachelor’s from MIT (08:30).
• Started as a sanitary bacteriologist, focusing on water contamination and safety, with significant contributions to oyster farming and purification (09:37–11:20).

4. The Marriage: Professional and Personal Partnership

• Married in 1916; had a son, Bud, whose later institutionalization is discussed (09:11).

5. Polio Research and Transmission Theories

• Mildred contributed vital work on the epidemiology of polio, questioning the droplet theory of transmission and highlighting the inconsistencies in how polio spread (13:35–17:19).
  • Quote:

    "Certainly poliomyelitis as we ordinarily encounter it in the United States does not behave epidemiologically in accordance with the concepts that have become crystallized as to how a contagious disease should behave." – Tracy V. Wilson, reading Wells (16:16)

• Descriptions of the "droplet" model as dominant, yet lacking explanatory power for certain epidemics (14:01–17:57).

6. Collaboration at Harvard: Innovations and Experiments

• William invents the Wells Air Centrifuge to analyze airborne pathogens, paralleling his previous work with oyster sorting (21:38–23:02).
• Legendary experiment with sneezing powder during a lecture to demonstrate airborne spread and bacteria persistence (23:02–24:02).

7. Key Discoveries on Airborne Disease

• Their research describes droplets vs. "droplet nuclei"—smaller particles that can remain airborne and infectious much longer (24:26–28:21).
  • The “Wells curve” describes the dynamics of particle gravity, evaporation, and airborne longevity.
• Demonstrated, in animal models and real-world school experiments, that UV light could reduce the incidence of disease transmission in some settings (25:45, 37:06).

8. Institutional Pushback and Professional Setbacks

• Harvard colleagues were skeptical; both Welles were dismissed as "crabby and argumentative," possibly compounded by sexism and disputes about intellectual credit (29:37–31:30).
  • Notable moment:

    "Was she really being aggressive, or did people just think she was aggressive because she wasn't being meek?" – Tracy V. Wilson (31:15)

  • Mildred worked at Harvard without pay, while William did not have an advanced degree (24:02, 29:37).

9. Moving to University of Pennsylvania and Expanded Experiments

• Both secure positions at Penn, though Mildred’s salary is far less than William’s despite her higher qualifications (34:47).
• Publish influential papers on UV light applications for air purification and ventilation systems (35:17–37:06).
• Notable school experiments reducing measles transmission with classroom UV (37:49–38:22).

10. Mixed Outcomes, Frustration, and WWII Context

• Not all UV experiments were successful—often results were mixed or dependent on environmental conditions like humidity (38:22–42:36).
• Military slow to adopt their findings except in germ warfare, frustrating William:

  "The military's attention just seemed to be focused elsewhere... especially when he later learned that the army had been focused on airborne disease transmission when it came to the idea of germ warfare." – Tracy V. Wilson (38:57)

• The couple’s professional and personal partnership deteriorated during this period (39:35).

11. Major Later Scientific Contributions

• William and collaborators definitively demonstrated, via guinea pig experiments, that tuberculosis is airborne—a result foundational for the “Wells-Riley Equation,” used to calculate infection risk (40:08–44:18).
• Mildred continued research with community-wide interventions and comparative studies, with nuanced results (41:54–42:36).

12. Legacy, Oversimplification, and Modern Implications

• Their findings on airborne transmission and mitigation were largely ignored or misunderstood by the broader public health field—with adverse consequences for later pandemics, especially COVID-19.
  • Quote:

    "If their work had gotten more favorable attention, we might today be living in a world where illnesses that are spread through the respiratory system are less frequent and less widespread." – Tracy V. Wilson (45:58)

• Ideas got boiled down into over-simplistic dichotomies (e.g., droplet vs. aerosol, 5-micron threshold), hampering pandemic policy (47:37–49:20).
  • Quote:

    "That droplet guidance led to things like the social distancing guideline of 6ft apart... and a very big focus on handwashing and surface sanitizing. It was not until more than a year into the pandemic that [WHO and CDC] acknowledged that COVID could be airborne." – Tracy V. Wilson (47:37–48:49)

• Recent interest in far-UVC technology as a “new” idea, when in reality the Wellses were using similar methods nearly a century ago (50:18).

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Notable Quotes & Memorable Moments

• "People were being exposed to diseases carried through the air... over and over in a cycle that would continue until the whole population was finally immune to whatever the illness was." – Holly Fry (27:30)
• "The atmospheres of our common habitations are even more highly infective." – Quoted from William and Mildred’s publication (28:21)
• Reference to the “trap shooter of the scientific world” moniker for William in the press: “dropping [the flu bug] with an ultraviolet ray.” (29:04)
• On Mildred’s role and recognition: “She was doing work and not getting paid for it. Right, and handing over the credit to men.” – Holly Fry (31:22)

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Timestamps for Important Segments

• Ep. Motivation, COVID Frustration & Research Origins: [05:14–06:06]
• Mildred’s Early Life and Family Troubles: [06:06–08:04]
• William’s Background & Waterborne Disease Work: [08:30–11:46]
• Polio Research and Epidemiology Contradictions: [12:48–17:57]
• Wells Air Centrifuge & Airborne Bacteria Studies: [21:38–23:02]
• Collaboration, Skepticism, and Gender Dynamics: [24:02–31:30]
• Transition to Penn & Detailed UV Light Findings: [34:47–38:22]
• World War II, Military Frustrations, and Marital Rift: [38:57–40:08]
• Guinea Pig Experiments & Wells-Riley Equation: [40:08–44:18]
• Influence on COVID-19 Response & Public Health: [45:58–50:18]

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Episode Conclusion

Holly and Tracy close by reflecting on how William and Mildred Wells’s pioneering work—spanning airborne disease mechanics, experimental interventions, and epidemiological consequences—was largely sidelined due to professional conflicts, sexism, the dominance of older medical paradigms, and eventual over-reliance on vaccines and antibiotics. This oversight had serious ramifications for pandemic response in the 21st century, especially during COVID-19, as vital concepts of airborne spread and environmental control remained misunderstood or ignored.

Their legacy persists through terminology, equations, and a foundational understanding of disease ecology—though recognition came too late to influence the public health practices of their own era.

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Transcript

[Tracy V. Wilson]

This is an iHeart podcast.

[Ryan Seacrest]

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[Holly Fry]

Listen to your elders, honey. You might know them from their viral videos, but now the old gays are pulling back the curtain with their new podcast Silver Linings with the Old Gays. Brought to you in partnership with iHeart's Ruby Studio and Veeve Healthcare. Hosts Robert, Mick, Bill and Jesse serve their lifetime of wisdom when it comes to love, sex, community and whatever else they've got on the gay agenda. So check out Silver Linings with the old gays on the iHeartRadio app or wherever you get your podcasts. Welcome to Stuff youf Missed in History Class, a production of iHeartRadio.

[Tracy V. Wilson]

Hello and welcome to the podcast. I'm Tracy V. Wilson.

[Holly Fry]

And I'm Holly Fry.

[Tracy V. Wilson]

Before we start our episode today, a couple of folks have asked us where they can buy shirts and things because we used to have a T shirt store.

[Holly Fry]

Yeah.

[Tracy V. Wilson]

And then it went away. And the reason for that is just that iheartradio moved. They didn't. They were already with a different T shirt vendor than we had been with when iheart acquired us. And so eventually we needed to all be on the same thing. So our T shirt store now [e-mail] you can either go to cottonburo.com and search for stuff you missed in history class, or you can go to cottonburo.com/people/stuff you missed in history class with each of those words separated by a dash. Personally, it seems easier to me to just go to cottonburo.com and use the search function. But you do you. Right now we have coffee mugs, tote bags, cell phone cases, stickers, and T shirts. Our prior T shirt vendor was the creator of a lot of our previous T shirt designs. So right now what we've got is stuff with our logo on it. But in the future we may have some other designs also kind of working on that behind the scenes. Just wanted to let everybody know in case you either have looked for a shirt recently or have just wondered, do they have T shirts and stuff? Now we do again, cottonburo.com and now we can start the episode. A couple of weeks ago, I was listening to an episode of the podcast 99% invisible. And this episode was called Airborne. It was an interview with Carl Zimmer, who wrote the Hidden History of the Life We Breathe. I have not read this book. I did use it to confirm some details biographically about the people that we are talking about today, but I cannot comment on the book as a whole. What I can comment on is that over the course of this episode, I got progressively more frustrated because they were talking about some research that sounded like, at least in theory, it could have really lessened the impact of the COVID 19 pandemic. But this was not like new research from after the pandemic started. It was from the 1930s and 40s. So as I was listening to this, I jotted down a couple of potential podcast topics for our show as I was listening and getting mad about it. One was 19th century chemist Max von Pettenkofer, who I knew sounded familiar but had forgotten that we already did an episode on. We will have that episode as our next Saturday classic. And the other thing I wrote down was today's topic, which is husband and wife team William Firth Wells and Mildred Weeks Wells. Their research had the potential to make a really big difference in the safety of the indoor air. But that research did not really have that kind of impact on public health. And just to note, this research did involve some experiments on animals.

[Holly Fry]

Mildred Weeks was born in 1891 to William F. Weeks and Mary Alice Denton Weeks. She was born in what's now Oklahoma, then it was called Indian Territory. And she had an older sister named Marian. We don't really know a whole lot about Mildred's early life, but it seems like things may have been difficult for her and her sister, even though they were from a prominent family.

[Tracy V. Wilson]

So that explanation goes back to before her parents, William and Mary Alice, were married. The girl's great grandfather, John B. Denton, was the namesake of the city and county of Denton, Texas, and then his son. Their grandfather, Ashley Newton Denton, was a doctor who was appointed superintendent of the Texas State Lunatic Asylum. The asylum bookkeeper was the girl's future father, Willie William Weeks. Denton and Weeks were both accused of mismanaging the asylum's funds, and Weeks was eventually charged with embezzling somewhere between a thousand and fifteen hundred dollars.

[Holly Fry]

Both men maintained that they had not done anything wrong. One newspaper write up of Weeks's arrest said that, quote, his numerous friends here assert that while he was careless in business matters, he will explain out of it. These allegations don't seem to have affected Denton's opinion of Weeks, though, since he presumably gave his permission for his daughter Mary Alice to marry him in 1888, which was right in the middle of all of this.

[Tracy V. Wilson]

William was exonerated in 1890 and the family went to Indian Territory, which, as we said, is where Mildred was born. But rumors continued to follow William and eventually he seems to have kind of disappeared. Mary Alice died when Mildred was only 10. And Mildred and her sister Marian were raised primarily by their grandmother who lived in Austin, Texas.

[Holly Fry]

Mildred earned a bachelor's degree from the University of Texas medical branch in 1911. She earned her MD from the University of Texas at Austin in 1915, where she was one of only three women in a class of 34. She moved to Washington, D.C. and got a job studying bacteria at the Public Health Service Hygienic Laboratory. While working at the lab, she met William Firth Wells.

[Tracy V. Wilson]

William Firth Wells was born in Boston, Massachusetts on August 25th of either 1886 or 1887. I found both those years. His parents were Obadiah F. Wells and Helen Davis Wells, and he was one of their four children. We don't have a lot of detail about his early life either, but he studied bacteriology at the Massachusetts Institute of Technology. He graduated from there in 1909. After graduating, he eventually made his way to Washington, D.C. to become a sanitary bacteriologist for the Public Health Service a few years before Mildred also started working there.

[Holly Fry]

Mildred Weeks and William Firth Wells got married in 1916, and a year later they had a son, William Jr. They called him Bud. We also don't have a whole lot of detail about Bud, but it seems as though he was disabled or he had some kind of mental illness. He always lived with family until being institutionalized, which happened after Mildred's death. And at that point he was in his 40s.

[Tracy V. Wilson]

During World War I, William Senior was drafted and joined the Sanitary Corps, serving both stateside and in Europe and attaining the rank of captain. His work before, during and after the war was largely focused on water contamination and waterborne illnesses. He studied how diseases could be spread through the water and how Salmonella typhi, which causes typhoid fever, could grow in oysters. He developed filtering techniques to purify river water so that it would be drinkable and chlorination methods to clear bacteria out of oyster beds.

[Holly Fry]

After the end of World War I, the Weekses moved to New York, where William had gotten a job with the state's Conservation Commission. He continued working with oysters, including developing methods to artificially propagate them and repopulate depleted oyster beds. Inspired by machines that separated cream from milk, he developed a centrifuge that could separate oyster larvae from the water so that they could be raised in tanks and then returned to the Long Island Sound. This combined with his earlier sanitation and water quality work to ensure that these oysters would be safe to eat once they were harvested.

[Tracy V. Wilson]

By 1925, Williams work with oysters was being hailed as almost miraculous. The association of Fisheries Commissioners and the national association of Oyster Growers and Dealers held a celebratory dinner on October 1st of that year with artificially propagated oysters on the menu, and this whole thing was praised in newspapers.

[Holly Fry]

Two years later, an Associated Press write up on Williams work described the oysters that he was growing as super oysters. He moved from the New York State Conservation Commission to a higher paying job with an oyster company. But then In October of 1929, the stock market of course crashed, which is marked as the start of the Great Depression, the oyster company was sold and William lost his job.

[Tracy V. Wilson]

William tried to make ends meet by writing and consulting, and Mildred got a job working with the International Committee for the Study of Infantile Paralysis, also known as polio. Polio had been on the rise in parts of the world since the late 19th century, and it was widely feared and not completely understood. Carl Landsteiner and Erwin Popper had confirmed that polio was infectious, and they had concluded that it was caused by a virus. In 1908, doctors also had a sense that polio could be spread asymptomatically. But once they were able to isolate the actual virus, they didn't usually find evidence of it in people who were not experiencing symptoms. So they didn't really understand exactly how the virus was spreading. Outbreaks often happened in large waves, usually in the summer. But the patterns of cases within those outbreaks could seem almost random.

[Holly Fry]

Mildred Wells was part of a project to systematically evaluate all of the research that had been done on polio and to produce a comprehensive work on the subject. That work was published in October of 1932 as poliomyelitis, a survey made possible by a grant from the International Committee for the Study of Infantile Paralysis. This was primarily funded by philanthropist Jeremiah Milbanke. Other than Milbanke's forward and a preface by Dr. William H. Park, this book was written entirely by women. The first chapter, historical summary, was by Elizabeth F. Hutchin, and the remaining chapters were all by women. MDs Helen Harrington, Josephine B. Neal and Mildred Weeks Wells.

[Tracy V. Wilson]

Wells wrote the chapter on epidemiology. Several modes of transmission had been proposed for polio, including direct transmission through respiratory droplets, milk water, insect bites and fomites. When she started working on this project, insect transmission had been generally rejected and the most widely accepted theory was droplets.

[Holly Fry]

Droplets were believed to be able to travel only a short distance, meaning that people had to be in close contact to spread droplet borne diseases. This idea grew from the work of German microbiologist Carl Fluge, who had done research primarily focused on tuberculosis in the late 19th and early 20th centuries. He was building on earlier work which had already demonstrated that coughs and sneezes could carry infectious particles that could settle on things like clothing, bedding and handkerchiefs. Fluge did things like placing microscope slides at varying distances from tuberculosis patients, finding that the slides closest to the patients collected the largest respiratory droplets with the most bacilli, while the ones farther away had much smaller droplets with very few bacilli.

[Tracy V. Wilson]

So Pfluge's findings were way more complex than this, and a lot of them were specific to tuberculosis. He hadn't studied other diseases and whether they worked the same way at all. But a lot of doctors took away from this that diseases were spread through droplets, and droplets didn't travel very far and settled out of the air quickly. So close contact was required for most disease spread, and airborne spread at a much greater distance was not really a big concern.

[Holly Fry]

One such doctor was Charles Chapin, health Officer of Providence, Rhode island, and author of the 1916 Public Health Manual the Sources and Modes of Infection, that was regarded as a landmark text in the field. This work stressed the role of droplets while minimizing the idea that there was much danger from airborne pathogens that could travel longer distances. Under the heading actual danger of infection by air, Chapin wrote, pathogenic bacteria may withstand drying and the pulverization of the dried material, and they may actually be found floating in the air, yet they may not after all be dangerous either because they have holy or partially lost their virulence, or because there are too few in number, or for some other unknown reason.

[Tracy V. Wilson]

Mildred Weeks Wells research into the epidemiology of polio didn't line up with what was known about droplets. She described polio's seasonal recurrence as difficult to reconcile with droplet transmission. At one point she wrote, quote, certainly poliomyelitis as we ordinarily encounter it in the United States, does not behave epidemiologically in accordance with the concepts that have become crystallized as to how a contagious disease should behave.

[Holly Fry]

She then quoted from a 1931 paper by M. Greenwood titled on the Statistical Measure of Infectiousness, quote an illness is held to be catching when it has usually been possible to explain the existence of a case of it by close association with an immediately pre existing case case. The notion of more or less infectiousness depends on some appraisement of the proportion of persons attacked to persons exposed to the risk of attack.

[Tracy V. Wilson]

So polio was weird. It seemed to be catching, and yet it did not fit that description of catching because people who caught it often didn't have a history of close contact with another polio patient. Wells wound up concluding that polio was similar to other airborne or droplet infections, but that people seemed to have a higher innate resistance to it than to diseases like smallpox or measles, possibly because people became immune to polio after being infected but without developing clinical symptoms.

[Holly Fry]

Today, polio is known to be transmitted through droplets and aerosols and through fecal contamination, which the research Mildred was working with really did not think was the case, so she wasn't completely on the right track for thoroughly explaining the epidemiology of polio. But this did lead her to thinking about ways that disease might travel through the air.

[Tracy V. Wilson]

Mildred's and William's work came together after this, which we will get to after a sponsor break.

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[Holly Fry]

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[Tracy V. Wilson]

William Firth Wells work with oysters led him to the use of centrifuges to separate oyster larvae from fluid Mildred Weeks Wells work on polio led her to think about airborne disease spread. Those two things came together in 1930 when William found another full time job working at Harvard doing research and teaching sanitary science. This job paid a lot less than he had been making working for the Oyster company, But the Great Depression was still going on and the Welles really needed the money.

[Holly Fry]

At Harvard, William Wells developed a machine, the Wells Air Centrifuge, that could separate bacteria, dust, and other contaminants from the air the way that he'd separated oyster larvae from seawater. He also developed a nutrient medium to use in the centrifuge's collection tubes so that any bacteria from the air would be able to grow so that he could then analyze it. At the request of the Commonwealth of Massachusetts, he used this centrifuge to study the safety of the air in text mills in towns like Fall River, Lawrence, Lowell, and New Bedford, where the air was full of textile dust and also artificially humidified. Wells eventually brought on assistants for this and other work, and those were brothers Richard and Edward Riley.

[Tracy V. Wilson]

In 1934, William Wells intentionally introduced bacteria into one of the air conditioning systems at Harvard and then used his centrifuge to collect air samples and track where all the bacteria went. That same year, he did an experiment. During one of his lectures, he used the centrifuge to sample the air at the beginning of class, and then he introduced some sneezing powder into the machine's exhaust. As it spread, the student started sneezing and he collected another sample of the air. He collected another sample after some more time had passed, and then a final sample after class was over and the students had left the room. He compared each of these samples, finding the largest number of normally occurring respiratory bacteria in the samples that had been taken. Sometime after the students had started sneezing. But there were also still bacteria in the sample that he took after the class was over.

[Holly Fry]

Mildred was also part of this research, Although she was not officially hired at Harvard until 1935, and even then she wasn't paid a salary. A lot of their work was collaborative, with both of them deeply involved. But Mildred was the one who wrote most of the papers and lectures. Much of their published work was published under both of their names.

[Tracy V. Wilson]

Their research strongly suggested that some bacteria could travel more than just a short distance, like in a droplet, and could stay in the air and stay viable for a long time. Building up in the air of a room the longer people were in there breathing it. But when they took the centrifuge outdoors, their samples yielded few, if any, viable bacteria.

[Holly Fry]

These findings were summed up in a patent application a few years later. Ordinarily, the droplet nuclei are so rapidly dispersed in the outside air that there is but little danger of infection thereby. In crowded or poorly ventilated spaces, however, they constitute a real menace. Even well ventilated buildings are not free from this danger, Particularly where the same air, after conditioning, is recirculated so as to be used over and over again for breathing. For such recirculation merely adds to the bacterial concentration of the recirculated air.

[Tracy V. Wilson]

While a lot of their colleagues were really skeptical of their work, William and Mildred became convinced that diseases could be spread through the air beyond just close contact from droplets. And they started experimenting with ultraviolet light as a way to stop it.

[Holly Fry]

As with Williams work with oysters, this got some media attention. On July 30, 1936, the Decatur Daily Review ran a photo of Wells with his research equipment at the Harvard School of Public Health. And it ran under the headline Scientists Fight Flu Germs with Violet Ray. He was working on an experiment that involved funneling influenza infected air to a ferret enclosure. The vents carrying the air to some of the ferrets were treated with UV light, while the other vents were not. And the ferrets getting the UV treated air stayed healthy while the others got sick.

[Tracy V. Wilson]

In November of 1936, Mildred and Richard published two articles in the Journal of the American Medical Association. One was titled Airborne Infection, and the other was Airborne Sanitary Control. Airborne Infection detailed the Wells conclusion that there were two types of airborne disease transmission. There were droplets as previously described by Carl Fluge. These were larger than 0.1 millimeters in diameter. These quickly fell from the air due to gravity. But droplets smaller than 0.1 millimeters in diameter could stay aloft and as they were aloft, they evaporated, leaving behind only the droplet's infectious nucleus, which could stay in the air even longer and travel much farther than droplets could. A graph of the relationship among gravity, evaporation and how long infectious material can stay in the air is known as the Wells curve.

[Holly Fry]

They also concluded that the number of bacteria in the air, quote, correspond to the degree of contamination by the occupants. And they compared this to waterborne intestinal illnesses. People were being exposed to diseases carried through the air, including influenza, pneumonia, bronchitis, colds and measles, over and over in a cycle that would continue until the whole population was finally immune to whatever the illness was. But if people were experiencing the same number of intestinal infections by repeated exposure to waterborne illnesses, that would condemn a water supply as being highly dangerous. They went on to say, it might be concluded on epidemiologic grounds that the atmospheres of our common habitations are even more highly infective.

[Tracy V. Wilson]

Airborne infection. Sanitary Control reported on experiments conducted in the tunnels under Harvard Business School which tested tested the susceptibility of airborne pathogens to ultraviolet light. The most dramatic reductions of bacteria in the air were within 5ft of a UV light source. But there was still a measurable difference as far as 55ft away. They concluded air purification methods that depend on filtration or sedimentation may be more effective against dust, and ultraviolet rays may be more effective against nuclei, the two being complementary and therefore effectively combined.

[Holly Fry]

In 1937, the Washington, D.C. evening Star noted the Welles's work, although without mentioning Mildred. This write up said in part, quote, Dr. William Firth Wells is the trap shooter of the scientific world. For five years he has been gunning for the flu bug, dropping it with an ultraviolet ray. This write up went on to call the project a scientific cleansing of workaday breathing air, which will vastly lessen casualties from nose and throat diseases.

[Tracy V. Wilson]

That same year, William Firth Wells and Mildred Weeks Wells were fired from Harvard. William had been hired even though he didn't have an advanced degree. And on top of that, he is not described as a very good teacher, giving ponderously boring lectures and caring only about his research, not his classes. But a bigger issue seems to have been that he and Mildred both developed a reputation for being really hard to work with, including being crabby and argumentative. Some frustration is understandable here, given that a lot of their colleagues just seemed really dismissive of their work. But the Welles also apparently argued with people who were on their side and with people whose opinion of them really mattered. Like their boss, Gordon Fair, professor of Sanitary Engineering.

[Holly Fry]

Fair apparently thought he should be credited on the Wells's publications as well as named on the patent application that came from their work. That was US patent 219-8867 Method and Apparatus for Preventing Infection, which we read from earlier. That patent was awarded in 1940, not only with Fair's name on it, but with Fair listed first. William and Mildred both seem to have fought with Fair over this credit issue, and according to some accounts, Mildred was more aggressive about it. But it's also really hard to take that at face value since people's perceptions of her would have been influenced by social expectations for women to be polite and unassertive.

[Tracy V. Wilson]

Yeah, was she really being aggressive or did people just think she was aggressive because she wasn't being meek?

[Holly Fry]

Also, she was doing work and not getting paid for it. Right, and handing over the credit to men.

[Tracy V. Wilson]

It took some effort for them to find a new employer, which we will get to after a sponsor break.

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[Ryan Seacrest]

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[Holly Fry]

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[Tracy V. Wilson]

After being fired from Harvard, the Welles next move was to Philadelphia, where the University of Pennsylvania had established an airborne infection laboratory. This included paid positions for both William and Mildred. While Mildred was being paid about a third of what William made, even though she had an MD and he had a bachelor's degree, their combined salaries were more than William had been making at Harvard.

[Holly Fry]

In 1938, William and Mildred published Measurement of Sanitary Ventilation in the American Journal of Public Health Health that began Ability to modify man's environment is not confined to enhancement of comfort, convenience, or even safety, but extends to the prevention of disease and the promotion of health by supplying pure water and pure food. The sanitary engineer has, in many communities, almost eliminated intestinal infection. Is it unreasonable to hope that when airborne infection is better understood, diseases conveyed through the respiratory tract may likewise be reduced through the provision of pure air supplies?

[Tracy V. Wilson]

This paper presented multiple possible configurations for using UV light to reduce the number of pathogens in the air. One was using UV light to treat the air within a ventilation system before circulating that air back into a room. That could be the most useful in small, crowded spaces like train cars. In large rooms, there was a lot more space and a lot more air, making that kind of ventilation treatment inefficient. The UV lights at the time had the Potential to cause eye damage. So treating the whole room was most easily done in scenarios like operating rooms. Where there was a high need for infection control. And also all the people in the OR could reasonably be expected to wear eye protection. Other possibilities included things like light barriers, Like a curtain of UV light that would separate hospital wards from each other. There were equations for the bacterial reduction. That could be expected with each of these different setups.

[Holly Fry]

From there, the paper expressed a hope that this kind of research could be correlated with epidemiological data. This may lead to a realization of our present hope. Hope that if the sanitary quality of air is controlled, Reduction of respiratory disease will be accomplished.

[Tracy V. Wilson]

William had invented what he called an infection machine, which could be used to expose animals to air that was laden with viruses or bacteria. By 1941, William had used this machine to demonstrate that tuberculosis, influenza, and strep could all be transmitted to animals through the air. And that treating that air with UV light Could prevent those infections.

[Holly Fry]

Meanwhile, Mildred was working on a practical experiment. That had started at Germantown friends School in 1937. UV lamps installed in some of the classrooms. Seemed to reduce the number of measles cases during an outbreak at the school. There were about 10 times fewer measles cases in the classrooms with the light sites Than the ones without them. Mildred published Ventilation in the Spread of Chickenpox and Measles within schoolrooms in 1945, which detailed these findings.

[Tracy V. Wilson]

Not all of their experiments were that effective, though. In 1942, UV lights installed in the town of Swarthmore. Seemed to stop one outbreak of mumps. But it didn't have much of an effect on another one. The Weekses speculated that there might be a seasonal factor to this. The lights seemed to work in the winter when the air was dry, but not in the summer when it was humid. They speculated that this humidity might affect how well the lights worked. And that that might also be connected to the seasonality of some illnesses.

[Holly Fry]

During World War II, William advised the War Department on protections for soldiers living in crowded camps and barracks. He and Mildred were both concerned about something like the 1918 flu pandemic happening again. But while there was some limited use of UV lights at military facilities, the military's attention just seemed to be focused elsewhere. And this really frustrated William, Especially when he later learned that the army had been focused on airborne disease transmission. When it came to the idea of germ warfare, Just not when it came to protecting soldiers from ordinary illnesses.

[Tracy V. Wilson]

William and Mildred's marriage also seems to have fallen apart, at least partially during this Period. Their maid left her job, and it's likely that the maid had been doing some of the caregiving work for Bud. Mildred resigned from the Airborne diseases lab in 1944. Each of them did projects on their own or with other collaborators rather than together after this. That includes Mildred's 1945 paper that we mentioned earlier, which was published with only her name.

[Holly Fry]

William worked with Herbert Ratcliffe on a tuberculosis study which concluded that only very small particles could get deep enough into the lungs to cause that disease. He also worked with his former assistant, Richard Riley, now a researcher in his own right, and a new assistant, Krettle C. Mills, on an experiment at the Baltimore Veterans administration. This involved 300 guinea pigs which were exposed to air from the rooms of tuberculosis patients. Half of the guinea pigs got air that was treated with UV light and the other half got air that was not. All of the guinea pigs getting UV treated air stayed healthy, while about three a month in the other group developed tuberculosis.

[Tracy V. Wilson]

Mildred worked with the New York State Department of Health trying to replicate the results of their earlier research with UV light lights. They started with an experiment in central schools that were located in rural areas. Based on the idea that these students mostly saw each other only at school without a lot of crowd exposure from outside of school, like a student would probably get if they lived in a city.

[Holly Fry]

This experiment had mixed results. The classrooms that had UV lights did seem to have a different pattern of disease spread during a measles outbreak. A few students at a time got sick over many weeks in the UV treated classrooms, while lots of children all got sick almost simultaneously in the untreated classrooms. But the total number of students who got measles was not that different. One possible complicating factor in this experiment was that the children rode buses to school and those buses did not have UV lights lights.

[Tracy V. Wilson]

Mildred also worked with William Halle to install UV lights in as many places as possible in Pleasantville, New York, so that it could be compared to nearby Mount Kisco, which did not have the lights. They published a paper on this in 1950 titled Ventilation in the Flow of Measles and Chickenpox Through a Community. Beyond installing these lights, Weeks and Hala figured out all of the children's susceptibility to measles and chickenpox based on their path past history so that they could factor that into their disease risk calculations. And they did contact tracing for each new case in each of the towns.

[Holly Fry]

The results of this study were also mixed. Pleasantville had a measles outbreak, but it hit during A Rainy Spring. And the Welles had already published that their UV lights were not as effective in high humidity. And it also seemed like even though there were no UV lights installed in Mount Kisco, its whole population was partially protected by the irradiation program that was going on in Pleasantville. It basically cut off one of the possible sources for an illness to be introduced into Mount Kisco.

[Tracy V. Wilson]

Meanwhile, William was writing a book called Airborne Contagion and Air An Ecological Study of Droplet Infections. It was published in 1955 after many years of work. It was more than 450 pages long. And while he had really hoped that it would serve as the definitive work on airborne infections and air sanitation, this book was really not a success. As we have said, Mildred was the better writer. She had written a lot of her stuff before this. She did not work on this book with him.

[Holly Fry]

Mildred Weeks Wells died on February 23, 1957, at the age of 65. William Firth Wells died on September 19, 1963, at the age of 76. Both of them had experienced serious health issues in the last years of their lives. Mildred's sister Marion tried to take over Bud's care after Mildred's death. But she was also in her late 60s by then. And as we mentioned earlier, ultimately Bud was institutionalized.

[Tracy V. Wilson]

William Firth Wells guinea pig study in Baltimore was still going on when he became too sick to work after his death, Mills and Riley finished the work and published it. Mills also contracted tb, but she recovered with treatment. This research definitively demonstrated that tuberculosis could be airborne. And it led to the development of the Wells Reilly Equation, also called the Wells Reilly Model, which is a way to calculate the probability of being infected by an airborne pathogen. William Wells's name was not included on the final publication of this work, though Riley later wrote an article about this in which he described that omission as his eternal shame.

[Holly Fry]

So Mildred Weeks Wells and William Firthwell studied airborne disease transmission for more than 20 years. They showed that a lot of diseases could be spread through aerosolized particles rather than just large droplets, and that some larger droplets had the potential to evaporate into much smaller particles. They also demonstrated that UV light could potentially reduce the number of pathogens in the air and thus the number of illnesses, at least in some scenarios. But while there were some other researchers who did experiments to replicate their work in the 1940s and early 1950s, this didn't lead to a huge rethinking of airborne disease transmission and its prevention, especially in public settings. The Wells work had more influence on studies of the physics of particles spread through the air Than on public health.

[Tracy V. Wilson]

To be clear, the widespread adoption of the kinds of UV lights that the welles were using probably would have caused other issues, including skin cancer, Especially if those lights were shining on people Rather than being used within air circulation systems. But it seems like if their work had gotten more favorable attention, we might today be living in a world where illnesses that are spread through the respiratory system Are less frequent and less widespread than they are today. Like, we might not be living in a world where it's just sort of taken for granted as inevitable that there is is a cold and flu season. And this, of course, also applies to Covid.

[Holly Fry]

There's some speculation around why their work didn't get that kind of attention. One possibility is just William and Mildred's reputation for being hard to work with, which made people just not want to. Another is that when they first started their research, the world of medicine was still trying to distance itself from the idea of miasmas as agents of disease. William and Mildred absolutely were not describing things as miasmas. They were talking about actual pathogens Being spread through the air. But it's possible that there was just some innate resistance to the idea of revisiting the air As a source of contagion. During and after their lifetime, Some of the diseases they studied Became preventable Through vaccines or treatable with antibiotics, which also may have made large scale projects to clear pathogens from indoor air Just kind of seem less urgent.

[Tracy V. Wilson]

Simultaneously, it seems like a conflation or oversimplification of ideas in the wells work May have contributed to standards that did eventually emerge in the field of infectious disease and public health. But standards that have some real limitations. One is an idea that diseases can be spread as droplets or as aerosols, and that there's a 5 micron threshold forming a dividing line between these two things, with most illnesses on the droplet side of that line. That played a huge part in the public health messaging about COVID in 2019 and 2020, when organizations like the world health organization and the centers for disease control really emphasized the idea that Covid was droplet based, not aerosol or airborne. That droplet guidance led to things like the social distancing guideline of 6ft apart or 1 or 2 meters, depending on where you live, and a very big focus on hand washing and surface sanitizing. It was not until more than a year into the pandemic that both of those organizations acknowledged that Covid could be airborne, Meaning aerosolized particles could travel a lot farther and stay in the air longer than droplets could. Washing your hands and cleaning things is still very important. It leads to reducing the spread of other diseases we've talked about on the show, like norovirus. But with COVID a really big thing is just not breathing in virus laden air.

[Holly Fry]

A paper titled How Did We Get Here? What are Droplets and Aerosols and How Far do they Go? A Historical Perspective on the Transmission of Respiratory Infectious Diseases was published in 2021. It looked at gaps in the understanding of airborne disease transmission and how those gaps affected public health policies during the early pandemic in a way that was confusing and ineffective. This paper traces the idea of the 5 micron threshold to multiple concepts from Wells's work that all got kind of mashed together. The idea that droplet and airborne transmission both existed depending on the size of the particle, and that particles measuring between 1 and 5 nanometers could penetrate deep enough into the lungs to cause tuberculosis. Conflating those ideas led to a different idea entirely, which has some parallels to what happened with the work of Carl Flugge, which we mentioned earlier.

[Tracy V. Wilson]

Meanwhile, in the context of COVID 19 specifically far UVC light started making headlines as a kind of new and novel way to possibly fight the pandemic in early 2021, and this has continued to be reported on in more recent months. Some articles on this acknowledge that UV light has been known to kill microorganisms for roughly a century, but FAR UVC has not really been framed as like a refinement of something that the Welles were using sometimes with really promising results back in the first half of the 20th century, I.e. william Firth Wells and Mildred Weeks Wells.

[Holly Fry]

Do you also have a little bit of listener mail?

[Tracy V. Wilson]

I do. This is from Aaron, and Aaron's email is titled Chronolog. Yes, with four S's and two exclamation points. Community Science Advocacy Listener mail, which I love the excitement of that title, Aaron wrote. Are you allowed to write listener mail about another listener mail? I squealed when I heard the listener mail at the end of the July Unearthed Part 2. I work for a land conservancy in northern lower Michigan and we use Chronolog to track restoration sites at our nature preserve. It's an invaluable tool for us and a really easy way to contribute to community science data aggregation. We have a relatively small team for the area we serve 38 people for a service area the size of Delaware, and only 10 of them are land stewards. I cannot stress enough the importance of community science Data from Inaturalist, Ebird Journey North, Nature's Notebook and Chronolog are used in our stewardship plan, restoration site management, invasive species tracking, communication, storytelling and fundraising. Community science is the quickest, easiest, cheapest and in my opinion most fun way to get involved with your local land trust organization. Thanks to you both for the amazing podcast. I love your obvious passion for telling everyone's history from a fair and neutral stance. The infinite fun facts I use to annoy my husband are just a bonus and now some pet adjacent tax for your time at work. We employ two herds of misfit and or retired dairy goats to help us battle an ongoing problem with the invasive shrub Autumn Olive. We also own and manage a farm where we manage a herd of Belted Galloway cattle as a demonstration tool for regenerative agriculture methods. I have attached a few photos of each Stay Weird Erin Man Erin, I love this email. I love these pictures of these cows. So cute. Goats. Also cute using goats for invasive plant management. Also love that by coincidence this weekend I was on a hike in one of my local green spaces and I am not sure if they were using Chronolog or another service because I forgot my phone at home and I I was fine hiking without my phone because my watch can also make a phone call in the event of an emergency. But that meant that when I got to a thing I had never seen before which was about helping them track the spread of an invasive plant which was a similar like put your phone on this stand and take a picture. I could not see whether they were using chronolog or some other service to do that, so I will have to go back by there at some point and find out. Thank you again Erin for this great email and these adorable pictures of delicious, delicious vegetation being munched up by goats. If you would like to send us a note about this or any other podcast, we are at history podcastheartradio.com and you can subscribe to our show on the iHeartRadio app or wherever else you'd like to get your podcasts. Stuff youf Missed in History Class is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts or wherever you listen to your favorite shows.

[Ryan Seacrest]

Stop settling for weak sound. It's time to level up your game and bring the boom. Hit the town with the ultra durable LG X Boom portable speaker and enjoy vibrant sound wherever you go. Elevate your listening experience to new heights because let's be real your music deserves it. The future of sound is now with LG LG x boom and for a limited time save [e-mail] with code fall25. Bring the boom x Boom.

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[Holly Fry]

At T. Rowe Price, their experience helps them see investment potential differently. Instead of quick answers, they know that what really leads to confident investing is true curiosity. And since you're listening to this podcast, we know you value curiosity too. It's what drives them to ask the questions that really matter in our ever changing world, like can healthcare innovations create a healthier world? And how will AI be a part of a new tomorrow? Just like you, their curiosity runs deep and with it comes the power to help you invest more confidently. Better questions, better outcomes. T. Rowe Price Learn more@t price.com Curiosity.

[Tracy V. Wilson]

This is an iHeart podcast.