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.