Association of classroom ventilation with reduced illness absence: a prospective study in California elementary schools

Abstract

Limited evidence associates inadequate classroom ventilation rates (VRs) with increased illness absence (IA). We investigated relationships between VRs and IA in California elementary schools over two school years in 162 3rd-5th-grade classrooms in 28 schools in three school districts: South Coast (SC), Bay Area (BA), and Central Valley (CV). We estimated relationships between daily IA and VR (estimated from two year daily real-time carbon dioxide in each classroom) in zero-inflated negative binomial models. We also compared IA benefits and energy costs of increased VRs. All school districts had median VRs below the 7.1 l/s-person California standard. For each additional 1 l/s-person of VR, IA was reduced significantly (p<0.05) in models for combined districts (À1.6%) and for SC (À1.2%), and nonsignificantly for districts providing less data: BA (À1.5%) and CV (À1.0%). Assuming associations were causal and generalizable, increasing classroom VRs from the California average (4 l/s-person) to the State standard would decrease IA by 3.4%, increase attendance-linked funding to schools by $33 million annually, and increase costs by only $4 million. Further increasing VRs would provide additional benefits. These findings, while requiring confirmation, suggest that increasing classroom VRs above the State standard would substantially decrease illness absence and produce economic benefits. Practical ImplicationsThese findings suggest a potentially large opportunity to improve the attendance and health of elementary school students in California through provision of increased classroom ventilation. The majority of classrooms in this study provided less ventilation than specified in current State guidelines. If the relationships observed here (and in several prior studies) and the costs and benefits estimated here are confirmed, it would be advantageous to students, their families, and school districts, and highly cost-effective, to ensure that ventilation rates in elementary school classrooms not only meet but substantially exceed current ventilation guidelines. Because specific exposures and response mechanisms involved have not been determined, it is possible that more energy-efficient alternatives to increased ventilation, such as filtration and reduced indoor emissions, might provide similar benefits. Nomenclature

CO2 concentration in day care centres is related to wheezing in attending children

“…In fact, in 90 % of the measurements in our sample, the recommended limit of 1,000 ppm (1,800 mg/m 3 ) [2] was exceeded as previously reported in schools [20], reinforcing the importance of the dissemination of better ventilation practices. Improving ventilation rates was recently associated with reduced student absences due to illness at elementary schools [13].…”

“…In the present analysis, CO 2 (ppm) was considered as a major comfort parameter and as a surrogate of IAQ and ventilation flow rate (13).…”

Human responses to carbon dioxide, a follow-up study at recommended exposure limits in non-industrial environments

“…Many studies have used CO 2 as a marker for exposure levels indoors and for ventilation efficiency, and examined the relationship between measured concentrations of CO 2 and subjectively assessed acute health symptoms (e.g., Seppänen et al, 1999;Apte et al, 2000;Erdmann et al, 2002), impairment in cognitive performance (e.g., Myhrvold et al, 1996;Myhrvold and Olesen, 1997;Coley et al, 2004;Bakó-Biró et al, 2008;Haverinen-Shaughnessy et al, 2011;Wargocki and Wyon, 2013) and absence rates (e.g., Milton et al, 2000;Mendell et al, 2013). In all of these studies, none of the observed effects were attributed to CO 2 .…”

Health hazard evaluation report: evaluation of indoor environmental quality and health concerns in a public university.

“…An analysis of the published scientific literature showed that nonspecific symptoms such as headache, fatigue, and mucous membrane irritation increase as ventilation rates decrease [Fisk et al 2009]. Studies in schools and office buildings have found decreased illness absence with increased ventilation rates [Milton et al 2000;Shendell et al 2004;Mendell et al 2013]. Thus, improving heating, ventilating, and air-conditioning operation and maintenance and increasing ventilation rates can improve symptoms without ever identifying any specific cause-effect relationships.…”