Can we establish relationship between outdoor air ventilation and health based on the published epidemiological data?

Abstract

Appropriate exposure control is prerogative for reducing the burden of disease (BOD) due to inadequate air quality indoors (IAQ). Ventilation with outdoor air is one of the available exposure control methods and is widespread. It is often assumed that this method will bring tangible effects on health. This paper examines whether the available archival epidemiological evidence provides information on the link between outdoor air ventilation and health that can be used for regulative purposes, when ventilation requirements for non-industrial built environments are set. To achieve this goal, multidisciplinary review was carried out of the scientific literature on health and outdoor air ventilation in non-industrial indoor environments (not covered by previous reviews on this topic) and of major reviews on this topic. The results show, that effects on health were seen for wide range of ventilation rates from 6-7 L/s per person, which were the lowest ventilation rates, at which no effects on some health outcomes were observed in field studies, until 25-40 L/s per person, which were in some studies the highest ventilation rates needed so no effects on health outcomes were seen. The actual contaminant exposures at various levels of ventilation were no characterized. It was observed that available data have many limitations, such as insufficient statistical power, incomplete data on the strength of pollution sources, diversity and variability of ventilation rates, at which effects have been seen, no standardized duration of exposures and diversity of the outcomes, as well as different sensibility of populations exposed. The health-ventilation relationship cannot thus competently be established, also because it must be admitted that outdoor air ventilation is only indirectly related to health by modifying exposures affecting health. It is concluded, that currently available epidemiological data do not provide sound basis for outdoor air ventilation requirements that can be universally applicable in different public and residential buildings to protect against health risks. They show minimum rates at which some health outcomes can be avoided, but these may not be generalized for the entire population of buildings, and thus cannot be used for setting minimum standards and/or regulations. Consequently, ventilation should not be advocated as the only solution to modify exposures, and should be implemented together with, and preferably after, other methods of controlling exposures have been fully exploited.