Mucous membrane and lower respiratory building related symptoms in relation to indoor carbon dioxide concentrations in the 100-building BASE dataset

Abstract

Indoor air pollutants are a potential cause of building related symptoms and can be reduced by increasing ventilation rates. Indoor carbon dioxide (CO(2)) concentration is an approximate surrogate for concentrations of occupant-generated pollutants and for ventilation rate per occupant. Using the US EPA 100 office-building BASE Study dataset, we conducted multivariate logistic regression analyses to quantify the relationship between indoor CO(2) concentrations (dCO(2)) and mucous membrane (MM) and lower respiratory system (LResp) building related symptoms, adjusting for age, sex, smoking status, presence of carpet in workspace, thermal exposure, relative humidity, and a marker for entrained automobile exhaust. In addition, we tested the hypothesis that certain environmentally mediated health conditions (e.g., allergies and asthma) confer increased susceptibility to building related symptoms. Adjusted odds ratios (ORs) for statistically significant, dose-dependent associations (P < 0.05) for combined mucous membrane, dry eyes, sore throat, nose/sinus congestion, sneeze, and wheeze symptoms with 100 p.p.m. increases in dCO(2) ranged from 1.1 to 1.2. Building occupants with certain environmentally mediated health conditions were more likely to report that they experience building related symptoms than those without these conditions (statistically significant ORs ranged from 1.5 to 11.1, P < 0.05).

Practical implications: These results suggest that provision of sufficient per-person outdoor ventilation air, could significantly decrease prevalence of selected building related symptoms. The observed relationship between indoor minus outdoor CO(2) concentrations and mucous membrane and lower respiratory symptoms suggests that air contaminants are implicated in the etiology of building related symptoms. Levels of indoor air pollutants that are suspected to cause building related symptoms could be reduced by increasing ventilation rates, improving ventilation effectiveness, or reducing sources of indoor air pollutants, if known.