Elsevier

Environmental Pollution

Volume 264, September 2020, 114746
Environmental Pollution

Assessment of indoor air exposure among newborns and their mothers: Levels and sources of PM10, PM2.5 and ultrafine particles at 65 home environments

https://doi.org/10.1016/j.envpol.2020.114746Get rights and content

Highlights

  • Indoor UFP were poorly correlated with PM (|rs|<0.552–0.594).

  • Indoor UFP were approximately 30% higher indoors that outdoors (|rs| = 0.456).

  • Indoor UFP mainly originated from indoor sources (mean I/O = 1.59, range 0.27–6.67).

  • Indoor PM2.5 mostly resulted from outdoor emissions infiltrations (mean I/O = 0.88).

  • PM2.5 and PM10 exceeded WHO daily limits in 75% and 41% of homes, respectively.

Abstract

Significant efforts have been directed towards addressing the adverse health effects of atmospheric particles, emphasizing the relevance of indoor exposure. Homes represent an indoor environment where human spend the majority of their time. Thus, the objective of this work was to concurrently assess different matrix of indoor particles considering both mass (PM10, PM2.5) and number (N20-1000) concentrations in indoor and outdoor air of homes (n = 65). Real-time measurements (PM10, PM2.5, UFP) were conducted simultaneously during 48 h in dwellings situated in Oporto, Portugal. In 75% of homes, indoor PM2.5 (mean = 53 μg m−3) exceeded limit of 25 μg m−3, for PM10 (mean = 57 μg m−3) 41% of homes demonstrated average levels higher than 50 μg m−3, thus indicating potential risks. Indoor PM10 was mostly (82–99%) composed of PM2.5, both PM were highly correlated (|rs|>0.9655), thus suggesting the similar origin. Indoor PM originated from infiltrations of outdoor emissions; ∼70% of homes exhibited indoor to outdoor (I/O) ratio < 1. On the contrary, UFP indoors (mean = 13.3 × 103 # cm−3) were higher than outdoors (mean = 10.0 × 103 # cm−3). Indoor UFP spatially varied as follows: kitchens > living rooms > bedrooms. UFP indoors were poorly correlated (|rs| = 0.456) with outdoor concentrations, I/O ratios showed that indoor UFP predominantly originated from indoor emission sources (combustions). Therefore, in order to reduce exposure to UFP and protect public health, the primary concerns should be focused on controlling emissions from indoor sources.

Introduction

The indoor air pollution represents a major health concern both for developing and developed countries. In low and middle-income countries, indoor pollution problems mostly result from the use of solid fuels, such as wood, coal, charcoal and animal dung that are burned in inefficient and highly polluting stoves; annually 3.8 million premature deaths are due to the diseases caused by household air pollution (WHO, 2019). In the western society, the driving force behind the shift to the problematic of indoor air pollution (Sharpe et al., 2018) was the trend to spend more time indoors, where indoor exposures have been associated with poorer health (Kelly and Fussell, 2019; Poowuttikul et al., 2019; Dimitroulopoulou, 2019). The growing evidence on hazardousness of poor indoor air and the respective health outcomes then led to the formulation of various strategies. To control the human exposure, World Health Organization (WHO) identified some of the priority indoor air pollutants (WHO, 2010), including particulate matter (PM).

The vast scientific evidence has demonstrated that exposures to PM10 (aerodynamic diameter <10 μm) and PM2.5 (aerodynamic diameter <2.5 μm) have been linked with increased morbidity (Agay-Shay et al., 2013; Schifano et al., 2013; van den Hooven et al., 2012) and mortality rates, in particular with cardiopulmonary and lung cancer (Fiordelisi et al., 2017; Holgate, 2017). Despite the ongoing efforts to reduce the respective pollution, both by the scientific community (Burns et al., 2019; WHO, 2005) as well as policymakers (European Parliament, 2007; U.S. Environmental Protection Agency (USEPA), 1990), exposure to PM is still among the leading causes of deaths worldwide. The most recent data (Health Effects Institute (HEI), 2018) show that 60% of the global population lives in cities where ambient PM2.5 pollution does not even oblige the least stringent interim target of 35 μg m−3 set by WHO (WHO, 2005). Outdoor PM2.5 ranks as 6th-highest risk factor for premature death (Health Effects Institute (HEI), 2018) and the 2016 estimates showed that PM2.5 contributed to 4.2 million deaths worldwide (Landrigan et al., 2017), clearly indicating the need to mitigate the respective exposure at international level.

Particulate matter contains particles of different sizes (WHO, 2005), including the ultrafine ones. By convention, these are typically designated as those <0.1 μm in aerodynamic diameter, though some authors suggested other cut-points (Kumar et al., 2014). Given their smaller sizes, ultrafine particles (UFP) contribute only little to overall particle mass and dominate the number concentrations. Thus, the commonly used metrics is the number concentrations (# cm−3) as opposed to mass concentrations (μg m−3). In ambient atmosphere, UFP are either formed via secondary formation processes (Hama et al., 2017; Ahlm et al., 2012) or emitted from combustion sources, such motor vehicles (Slezakova et al., 2019b; Ezz et al., 2015). Nevertheless, the indoor concentrations of UFP are affected by various parameters that include occupants related activities (e.g., cooking, smoking, candle burning, cleaning) (Morawska et al., 2013), use of indoor equipment (e.g., stoves, toasters, ovens, hair dryers, printers, fax machines, photocopiers) (Voliotis et al., 2017; Wallace and Ott, 2011), outdoor concentrations (Rivas et al., 2015; Quang et al., 2013; Slezakova et al., 2019a), and air exchange rates (Dimitroulopoulou, 2019; Cavaleiro Rufo et al., 2016). UFP have higher ability to penetrate into the alveolar epithelium and possibly even translocate beyond the lung, which is linked with the unique sizes of these particles (Bakand et al., 2012; Heal et al., 2012). In addition, they can carry various toxic compounds (due to the large surface area), and the possible interactions with tissues and cells (Chen et al., 2016) have led the scientists to believe that UFP may have enhanced toxicity (in comparisons to other particle fractions) (Chen et al., 2016; Heinzerling et al., 2016); nonetheless the current body of evidence is far from comprehensive.

Considering the amount of time that nowadays population spends indoors and depending on the specificity of the built environments (occupants’ density, particle dispersions, presence of emissions sources, etc.), indoor exposure to particles (Isaxon et al., 2015; Wierzbicka et al., 2015; Bekö et al., 2013) could several times exceed the ones of outdoors. Homes represent an indoor environment where human spent the majority (61–69%) (Brasche end Bischof, 2005) of their time. Because of the relevance of this environment, many works addressed concentrations of particles in homes, but only few of them focused on UFP (Jeong et al., 2019; Isaxon et al., 2015; Wierzbicka et al., 2015; Bekö et al., 2013; Lazaridis et al., 2017; Mullen et al., 2011; Wallace and Ott, 2011; Diapouli et al., 2008; Matson, 2005; Morawska et al., 2003, 2001). With exception of two studies (Jeong et al., 2019; Bekö et al., 2013), the number of homes included in these studies were often limited (n = 1–22); and, in addition, the information regarding concurrent assessments of both particle mass and number concentrations was limited (Jeong et al., 2019).

Thus, the objective of this work was to concurrently assess the concentrations of particulate matter (by mass), namely PM10 and PM2.5 and particle number concentrations (N20–1000) in indoor and outdoor air of homes (n = 65). Up to this date, this is the largest study to assess concurrent levels of different PM mass/number size fractions. Moreover, this large work applied the same sampling and analytical methods for data in 65 homes, thus avoiding potential publication bias and different approaches.

Section snippets

Population and sites description

Within NeoGene project, a cross-sectional birth study, healthy pregnant women were recruited during their last prenatal appointment at Centro Hospitalar de São João, Oporto Portugal. Sixty-five subjects (Table 1S of the Supplementary Material) agreed to participate in the air pollution exposure study at their homes (abbreviated as C1–C65). All participants were interviewed using a standardized questionnaire and personal information (such as maternal age and height, pre and post-pregnancy

Indoor PM10 and PM2.5

Overall, the levels of PM reported in this work were comparable to the previous studies. The indoor levels of PM10 and PM2.5 measured in 65 dwellings (C1–C65) demonstrated large variations of the obtained data (Fig. 1a–b), with detailed descriptive statistics summarized in Table 3S. Mean concentrations (obtained for each home) ranged between 14 (at C41) and 194 (C53) μg m−3 for PM10, whereas the corresponding values were 11–87 μg m−3 for PM2.5. The absolute ranges were 4–2610 μg m−3 and

Conclusions

In developed countries people spend major part (more than 2/3) of their time at homes. Thus air quality in these environments is relevant to human health. Across 65 homes indoor UFP (2.41–79.9 × 103 # cm−3; overall mean 13.3 × 103 # cm−3) and outdoor UFP (2.11–74.2 × 103 # cm−3; mean 10.0 × 103 # cm−3) were rather poorly correlated (|rs| = 0.456). In addition, I/O ratio analysis showed that UFP in indoor air predominantly originated from indoor emission sources (namely from cooking and other

CRediT authorship contribution statement

Joana Madureira: Conceptualization, Methodology, Formal analysis, Data curation, Writing - original draft. Klara Slezakova: Conceptualization, Methodology, Data curation, Writing - original draft, Writing - review & editing. Carla Costa: Writing - review & editing. Maria Carmo Pereira: Writing - review & editing. João Paulo Teixeira: Writing - review & editing, Supervision.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by FCT and FAPESP (FAPESP/19914/2014) and by Base Funding – UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy – LEPABE – funded by national funds through the FCT / MCTES (PIDDAC). Joana Madureira and Carla Costa are supported by FCT (SFRH/BPD/115112/2016 and SFRH/BPD/96196/2013 grants, respectively).

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