Multi-year study to determine the causal link between HEPA-filtered/unfiltered indoor air quality in occupied classroom (K-12) settings and human respiratory disease outcomes

Project Overview:

Graphic of project design

There is limited data on the direct impact of air quality engineering interventions on the reduction of viral transmission in congregant settings, especially for K-12 grade children in schools. This study will demonstrate and quantify the impact of high efficiency particulate air HEPA portable air cleaners (PACs) on classroom disease transmission through a coordinated approach in large numbers of schools and classrooms, employing a continuous multi-season sampling campaign in defined settings to have the statistical power and depth to discern changes in exposure patterns and their health impacts.  PACs can supplement existing air handling systems to help improve air circulation while reducing common indoor air pollutants in classrooms. The Colorado School of Public Health/University of Colorado-Denver & Dr. Mark Hernandez’s Aerobiology & Disinfection Lab at the University of Colorado-Boulder will measure the impact of air quality and in-room filtrations systems on respiratory viral pathogen (RVP) illnesses across K-12 classrooms in Colorado.  The study will analyze human disease endpoints of cause specific absenteeism & PCR/ATP desktop swabs as a proxy for infections/exposure.  

In support of this project, the Hernandez Aerobiology & Disinfection laboratory will be evaluating the impact of PACs on classroom hygiene and presence of respiratory pathogens in a sample of Denver Public Schools through desktop sampling and analysis of: 

  • PCR of respiratory viral pathogens (SARS-Cov-2, Flu, & RSV), 
  • ATP as a measure of bioburden on desks.

To establish the relationship between PAC-related IAQ improvements and absenteeism, the following activities were conducted in 4 major school districts across Colorado:

  • Continuously measure air quality parameters (CO2, humidity, temperature, volatile organic compounds (VOCs), and respirable airborne particulate matters (PM) in 2,640 K-12 classrooms across Colorado, including classrooms with and without recently installed PACs, favoring installation in schools with high Social Vulnerability Index (https://www.atsdr.cdc.gov/placeandhealth/svi/index.html)
  • Observe school absenteeism in response to PAC deployment (primary endpoint, weekly average at classroom level). Absenteeism reasons will be distinguished among the following categories: respiratory infections, gastrointestinal issues, and other (e.g., holiday)
  • Measure the occurrence of positive RVP tests through multiple seasons from desktop swabs (secondary endpoints) and conduct genomic sequencing from select positive samples.
  • Establish a causal link between selected air quality parameters (PM and CO2) and human disease endpoints in K-12 classrooms in Colorado; (a) to analyze the association between air quality measures and the primary endpoint, (b) to analyze the association between air quality conditions and the secondary endpoints and (c) to confirm that CO2 patterns (air exchange rate and mixing regimes) and PM levels are the main air quality parameters that are linked to primary as well as secondary human disease endpoints
  • Use the data collected to validate existing mathematical models for probability of infection in an established transmission model, and compare infection prevalence to community measures.
Numbered Desks for Desktop Swabbing
Desktop Swabbing Study Design