Indoor air quality, largely neglected and in urgent need of a refresh

ABSTRACT

While outdoor air quality is managed under the Resource Management Act 1991, which sets National Environmental Standards for outdoor air, no equivalent legislation exists for indoor air quality. The World Health Organization (WHO) recognises that healthy indoor air is a basic human right, stating that the quality of the air people breathe in buildings is an important determinant of health and wellbeing.3 According to the Environmental Protection Agency (EPA) in the United States (US), indoor air pollutant levels are typically two-to-five times higher than outdoor levels, and in some cases exceed outdoor levels of the same pollutants by a 100 times.4 Globally around 2.6 billion people still use solid fuels and kerosene for cooking, and the United Nations notes that indoor and ambient air pollution are the greatest environmental health risk.3 Time spent indoors combined with higher indoor concentrations of pollutants make the health risks associated with poor air quality usually greater indoors than outdoors. While initial public health efforts focused on measures to reduce fomite transmission, such as hand-washing, it is now well-recognised that airborne exposure is the predominant transmission route of SARS-CoV-2 (the virus that causes COVID-19).6 International consensus on airborne transmission was achieved in part through cutting-edge research conducted by New Zealand experts, but New Zealand health authorities have been slow to apply this key insight beyond border settings.7 It is imperative that national bodies responsible for the control of the pandemic incorporate the importance of airborne transmission to inform an evidence-based strategy and implement a range of highly effective measures that can prevent airborne transmission of the SARS-CoV-2 virus and other respiratory pathogens, including influenza.8-9'1011 The most effective approach to lowering concentrations of indoor air pollutants, including any pathogens that may be in the air, is usually to increase ventilation,12 exchanging polluted indoor air for cleaner outdoor air. Pollutant standards for heating and cooking appliances, particularly for appliances that use unflued gas should also be considered.20 An investment in clean indoor air could bring benefits other than reducing COVID-19 transmission, including reduced sick leave and school absenteeism caused by other respiratory infections, particularly influenza and other allergies.21 Less absenteeism-with associated adverse effect on productivity-could save companies significant costs.22 Furthermore, there is growing evidence that improved ventilation can improve cognitive functioning of workers and students,23 which can improve both wellbeing, sleep and productivity.24 Ventilation can also reduce indoor moisture particularly in homes, which wifi reduce exposure to respiratory allergens and irritants such as dust mites and mould, resulting in reduced incidence of asthma, rhinitis and allergy symptoms.