As we look for clues to better understand the COVID-19 pandemic, valuable insights can be gained from researching both detailed and holistic disease patterns. Lenny Landau, an allegedly retired mechanical engineer who worked with General Electric for more than 40 years and is dubbed “the Data King” by his local community, directed his analytical skills to better understand environmental drivers of the COVID-19 disease. The outcome of Landau’s investigations into publicly available data is revolutionary.

Landau and I began working together to explore national and global data on indoor humidity, SARS-CoV-2 transmission, and COVID-19 disease trends. As the second COVID-19 winter approached, we predicted that cases would increase as outdoor temperatures fell, heating systems were turned on, and indoor relative humidity dropped, following the same timeline as other seasonal respiratory viruses. As we predicted, the daily COVID-19 infection rate increased when cold weather set in, heat was turned on, and indoor humidity levels plummeted. We were startled, however, by a sudden new infection rate trajectory in a subset of U.S. states. While new infections in the southeastern U.S. increased as expected, case numbers in 18 contiguous midsection states dropped dramatically — even though outdoor temperatures and indoor humidity remained consistently very low.

What caused the unexpected drop in COVID-19 cases in some of the coldest states in the country? Since COVID-19 transmission is predominantly indoors, occupant gathering, ventilation, indoor humidity, indoor-generated ozone, indoor radon accumulation, and local public health mandates were investigated for variations. Only indoor radon accumulation varied by regions. Digging into maps of radon levels in homes, Landau found a correlation between regions where COVID-19 cases unexpectedly dropped and higher indoor radon levels existed.

Further investigation revealed that states with the highest indoor radon levels also had snow cover. Snow is known to reduce radon escape from the ground, creating a path of least resistance through building cracks and openings in basement floors and walls. In this way, snow cover acts like a switch concentrating radon indoors. Reduced ventilation from closed doors and windows in the winter, along with radon-enhancing effects of low indoor humidity, leads to higher radon levels.

This theory is not unprecedented. Research has shown that emissions from radon decay include alpha particles, gamma rays, and other progeny that are known to destroy COVID-19 as well as other viruses and bacteria. In other words, there is data that supports the hypothesis that radon decay products could interrupt the transmission of COVID-19.

As the winter progressed, a second puzzling change occurred. On Jan. 12, the COVID-19 daily case rate peaked and started to decline everywhere around the world. The widespread and simultaneous change could not be explained by public health measures or the end of the impact of holiday related activities, so Landau forged ahead into new data exploration.

The investigation revealed an 11-year solar cycle with corresponding cycles of viral respiratory disease epidemics and pandemics. When sun activity, characterized by more frequent sunspots and solar flares, is high, the period of the cycle is referred to as Maxima. Conversely, when the sun activity is calm with few sunspots or solar flares, the period is referred to as Minima. As far as we know, no epidemics or pandemics of viral respiratory diseases occurred during Maximas. Rather, all reported pandemics occurred during Minimas. While the relationship between the solar cycle and airborne diseases is recognized, the reasons are not understood.

We are currently in Minima between the 24th and 25th cycles. On Jan. 2, there were two very unusual Minima solar flares in the Southern Hemisphere of the sun. Solar flares are massive events that emit electromagnetic energy in the form of ultraviolet light, microwaves, x-rays, gamma rays, and electromagnetic fields. The emissions from the Jan. 2 solar event reached the Earth around Jan. 6, and Landau believes they are the reason for the worldwide decrease in COVID-19 cases on Jan. 12.

Furthermore, research on solar flares shows that EME reaching the earth can release radon from subterranean rock. Using the U.S. Centers for Disease Control and Prevention's (CDC’s) radon database allowed Landau to compare average annual radon levels from 2000 through 2019 in 13 states with solar activity. Although the data was limited, correlation between sunspots and average indoor radon levels was apparent. The indoor radon levels increased during solar activity, yet they remained below the U.S. Environmental Protection Agency (EPA) recommended mitigation level of 4 pCi/L. While more work remains to be done, solar activity and indoor radon exposure may explain why there are no pandemics during Maxima and why there was a decrease globally in COVID-19 cases on Jan. 12.

Radon is considered a health hazard above concentrations of 4 pCi/L. Could low concentrations of radon have a beneficial impact on occupant health during viral pandemics through mechanisms of natural germicidal activity? This question is important for engineers since ventilation and HVAC systems impact indoor radon accumulation. 

In summary, public health measures, such as social distancing, mask wearing, hand hygiene, indoor humidity control, and immunization, are essential and must be continued. While changes in regional disease rates can be associated with these interventions, simultaneous global disease changes call for a more holistic understanding. Landau’s data analysis on solar activity, indoor radon exposure, and viral respiratory diseases could facilitate pandemic forecasting and lead to new warning and mitigation technologies. We are not recommending alterations in indoor radon mitigation guidelines; we are simply revealing that physics sheds new light on pandemic patterns. 

Acknowledgements: We thank Bob Bunting, Aaron Kleiner, Susan Landau, Dr. Howard Levine, Tre Michel, and George Spoll, Stephen Suau, Dr. Lawrence Unger, Dr. Norman Weinberg, Phill Younger, and T.A. Zeug for their encouragement and support as well as the Florida Department of Health, NASA, the CDC, and the New York Times for data provided in the public domain.

This column was written in conjunction with Lenny Landau. Contact him at