Evaluating and reducing exposure to indoor pollutants from volatile organic compounds

Abstract

Indoor air pollution now ranks as a top environmental health risk globally. Poor indoor air quality can detrimentally affect human health and the economy. Volatile organic compounds (VOCs) are pervasive indoor air pollutants. The major objectives of this research are to evaluate what is known about indoor VOCs, to understand what the typical VOCs people are exposed to within indoor environments, and to assess ways to reduce exposures and effects of indoor VOCs.

First, this research systematically evaluates 25 years (1991–2016) of investigations of VOCs within indoor environments in Australia. Among 31 papers evaluated, the most frequently studied environment was domestic housing (61%), and the most frequently quantified compound was formaldehyde (81%). Active sampling techniques were used in 82% of studies of benzene, toluene, ethylbenzene, and xylene (BTEX), and in 38% of studies of formaldehyde and other carbonyls. New homes had the highest VOC levels among all studies of domestic housing. For nearly all pollutants, indoor levels were several times higher than outdoor levels. Among the most prevalent compounds indoors were terpenes, such as d-limonene and α-pinene. All studies were conducted at a regional or local level, and no study reported statistically representative indoor VOC data for the Australian population. The evaluation revealed a diversity of sampling approaches and techniques, pointing to the importance of a standard approach for collecting and reporting data.

Second, this research investigates volatile organic compounds (VOCs) at a large Australian university, within locations of campus services, restrooms, renovated offices, a green building, meeting areas, and classrooms. Analysis of 41 VOCs across 20 locations revealed indoor concentrations higher than outdoor concentrations for 97% of all VOC measurements (493 unique comparisons). Hazardous air pollutants (formaldehyde, benzene, toluene, and xylenes) were up to an order of magnitude higher indoors than outdoors, and at the highest combined geometric mean concentrations in classrooms (51.6 µg/m3), renovated offices (42.8 µg/m3), and a green building (23.0 µg/m3). Further, d-limonene, ethanol, hexaldehyde, β-pinene, and isobutane were up to two orders of magnitude higher indoors than outdoors. The most prevalent VOCs (e.g., ethanol, d-limonene, and formaldehyde) have links with building materials, furnishings, and fragranced consumer products such as air fresheners and cleaning supplies. Highest indoor to outdoor concentration (I/O) ratios of formaldehyde (27), toluene (9), p-xylene (12), and m-xylene (11) were in a green building; highest of benzene (6) in renovated offices; and highest of o-xylene (9) in meeting areas. Although indoor concentrations of hazardous air pollutants (i.e., benzene, formaldehyde, toluene, xylenes) were higher indoors than outdoors, the indoor concentrations are nonetheless lower than applicable World Health Organisation guidelines. Results from this study are consistent with findings from similar international studies and suggest that university indoor environments may be important sources of pollutants.

Third, this research investigates volatile emissions from six residential dryer vents, with a focus on d-limonene. It analyses and compares concentrations of d-limonene during use of fragranced and fragrance-free laundry products, as well as changes in switching from fragranced to fragrance-free products. In households using fragranced laundry detergent, the highest concentration of d-limonene from a dryer vent was 118 µg/m3 (mean 33.34 µg/m3). By contrast, in households using only fragrance-free detergent, the highest concentration of d-limonene from a dryer vent was 0.26 µg/m3 (mean 0.25 µg/m3). After households using fragranced detergent switched to using fragrance-free detergent, the concentrations of d-limonene in dryer vent emissions were reduced by up to 99.7% (mean 79.1%). This simple strategy of switching to fragrance-free products significantly and almost completely eliminated d-limonene emissions. Results from this study demonstrate that changing from fragranced to fragrance-free products can be a straightforward and effective approach to reduce ambient air pollution and potential health risks.

In summary, this research identified primary indoor air pollutants and understudied locations. It evaluated indoor air quality at a university and provided evidence that green and renovated buildings may not necessarily guarantee improvements for indoor air quality. It assessed an approach to reduce VOC emissions in residences and demonstrated that significant reductions were possible. In conclusion, this research provides novel scientific findings that can help improve indoor air quality both in Australia and internationally.