Effect Of Ventilation On Chronic Health Risks In Schools And Offices
This study provides a risk assessment for chronic health risks from inhalation exposure to indoor air pollutants in offices and schools with a focus how ventilation impacts exposures to, and risks from, volatile organic compounds (VOCs) and particulate matter (PM2.5). We estimate how much health risks could change with varying ventilation rates under two scenarios: (i) halving the measured ventilation rates and (ii) doubling the measured ventilation rates. For the hazard characterization we draw upon prior papers that identified pollutants potentially affecting health with indoor air concentrations responsive to changes in ventilation rates. For exposure assessment we determine representative concentrations of pollutants using data available in current literature and model changes in exposures with changes in ventilation rates. As a metric of disease burden, we use disability adjusted life years (DALYs) to address both cancer and non-cancer effects. We also compare exposures to guidelines published by regulatory agencies to assess chronic health risks. Chronic health risks are driven primarily by particulate matter exposure, with an estimated baseline disease burden of 150 DALYs per 100,000 people in offices and 140 DALYs per 100,000 people in schools. Study results show that PM2.5-related DALYs are not very sensitive to changes in ventilation rates. Filtration is more effective at controlling PM2.5 concentrations and health effects. Non-cancer health effects contribute only a small fraction of the overall chronic health burden of populations in offices and schools (<1 DALY per 100,000 people). Cancer health effects dominate the disease burden in schools (3 DALYs per 100,000) and offices (5 DALYs per 100,000), with formaldehyde being the primary risk driver. In spite of large uncertainties in toxicological data and dose-response modeling, our results support the finding that ventilation rate changes do not have significant impacts on estimated chronic disease burdens. Median estimates of DALYs are approximately doubled when the ventilation rates are halved and there is little reduction in health risks associated with doubling ventilation rates, but the very low baseline disease burden from the indoor exposures we considered makes this unremarkable. In exploring the full range of exposure concentrations, to find the fraction exceeding the Office of Environmental Health and Hazard Assessment’s (OEHHAs) chronic reference exposure levels (cRELs) and United States Environmental Protection Agency’s (USEPA) chronic reference dose (RfD) we found only minor shifts in exposure safety margins when ventilation was doubled or halved. We combined our exposure estimates with cancer potency factors published by OEHHA and USEPA to determine that the annual excess cancer risk per capita are below 1 in a million under all ventilation rate scenarios for individual pollutants. The results indicate that chronic health risks (cancer and non-cancer) associated with VOC and PM2.5 exposure in offices and schools are low and thus the chronic disease burden or health benefits of ventilation changes are likely to be well below both the level of detection by health surveillance studies and the level of regulatory thresholds.