Elsevier

Environmental Pollution

Volume 251, August 2019, Pages 839-849
Environmental Pollution

Characteristics and health risk assessment of heavy metals in indoor dust from different functional areas in Hefei, China

https://doi.org/10.1016/j.envpol.2019.05.058Get rights and content

Highlights

  • Combining SEM, XRD with element analysis.

  • Three different functional areas were carefully selected.

  • The TRs for carcinogenic effects decreased in the order Cr > Pb > Cd.

  • Comparing this study with previous studies to observe differences in health risks.

Abstract

Metals in indoor dust pose potential health risks to humans. Dust deposition on air conditioner filters can represent the resuspended particulate matter in indoor air. However, few studies have examined this until now. This study investigated the total concentrations and different chemical fractionations of Cd, Cr, Mn, Ni, Pb, Sb, V, and Zn in indoor dust from three different functional zones (the Chief District, Commercial District (CmD), and Industrial District) in Hefei. The mean metal concentrations in indoor dust decreased in the following order: Zn > Mn > Pb > Cr > Ni > V > Cd > Sb. Cd, Pb, and Zn mainly existed in the mobile fraction. Cr and V mainly existed in the residual fraction. The enrichment factor and geo-accumulation index values of heavy metals were all ranked in the order of Cd > Zn > Pb > Sb > Ni > Cr > V, and these values in indoor dust were larger than those in outdoor dust. In addition, the enrichment patterns of these elements were similar in the three functional areas. The orders of non-carcinogenic risk (hazard index; HI) for the different functional areas for children were roughly the same, but there were clear differences for adults. In general, all the HIs were less than 1, which were within the internationally recognized safe range. The total carcinogenic risk (TR) was in the order of Cr > Pb > Cd for both children and adults in the three functional zones. The TRs from Cr exposure were not negligible. The TRs were significantly higher in the CmD.

Introduction

In recent years, more researchers have begun to focus on air pollution. While human exposure to air pollution mainly occurs through indoor dust (Koehler et al., 2018; Habil et al., 2016), indoor air pollution is also receiving much more attention (Guo, 2002). Some scholars and experts believe that indoor air quality is the most important problem for human health (Yu et al., 2009; Massey et al., 2013). Studies have shown that adults now spend about 88% of the day and children spend about 71–79% of the day indoors (USEPA, 1997; Barrio-Parra et al., 2018). Extensive studies should be conducted to determine the chemical and physical features of indoor pollutants (Ruggieri et al., 2018). Indoor pollutants include particulate pollutants and gas pollutants (Yu et al., 2009; Sharma et al., 2018). Sources of particulate matter in indoor air can be divided into two categories, namely outdoor sources, that is, outdoor atmospheric particles that enter through doors, windows, ventilation devices, the activity of residents entering and leaving, etc., and indoor sources, namely smoking, cooking, and other indoor activities (Koehler et al., 2018).

In order to maintain a comfortable indoor temperature year-round, air conditioning systems have been widely used worldwide for a long time. Particulate matter in indoor air passes through the air conditioning filter and finally attaches to the filter (Verdenelli et al., 2003), thereby resulting in the relative improvement in indoor air quality. The air conditioning filter dust is assumed to be less than 100 μm in size, which can be resuspended from settled dust. The resuspended particles, which will adhere onto the surfaces of food, skin, toys, and furniture, can settle on the air conditioning filter (Huang et al., 2014). Thus, dust deposition on the air conditioning filter can to some extent represent the particulate matter in indoor air (Ali et al., 2018).

Heavy metals are difficult to degrade, have long incubation periods, and always lead to compound pollution. Therefore, heavy metals attached to the dust will affect the health of residents when they enter the body. For example, Cd has a half-life of about a few decades (10–30 years) and can have significant effects on the nerves and kidneys (Cheng et al., 2018; Thomas et al., 2008). Many researchers have discovered that the bioavailability and toxicity of metals are determined by their different forms (Li et al., 2015; Schleicher et al., 2011; Feng et al., 2009). Li et al. (2013) reported that trace metals with higher environmental mobility can be absorbed more easily in different environmental media, thereby posing a potential health risk to humans.

There have been many recent studies on indoor dust. Huang et al. (2014) found that compared to road dust, household air conditioner filter dust is more hazardous to human health, especially to children. Cheng et al. (2018) reported that living on a lower residential level (1st to 5th floors) and smoking habits may pose more potential health risks through exposure to heavy metals via household dust. Most of these studies have used comparisons of total metal compositions to determine pollution conditions, and have not considered the metal fractionation. In previous research at our laboratory, Ali et al. (2018) studied indoor dust and residents in Hefei City, but the sampling sites were randomly selected. In this study, samples were taken from families living on lower residential levels (1st to 7th floors) in three different functional areas (the Chief District (ChD), Commercial District (CmD), and Industrial District (InD)). Scanning electron microscopy, X-ray diffraction (XRD), element analysis, and other experiments were conducted to (1) understand the morphological characteristics, size distribution, mineral composition, and heavy metal concentration of indoor dust; (2) analyze the enrichment characteristics of heavy metals in indoor dust and compare them to the outdoors to explore the sources of indoor dust; and (3) evaluate the human health risks posed by heavy metals in indoor dust to assess residents’ health risks from prolonged exposure to them.

Section snippets

Study area and sample collection

This study was conducted in Hefei, which is the capital of Anhui Province. It is located in the upper limits of the Yangtze Delta (117°11”–117°22″E and 32°48”–31°58″N), which is a subtropical humid monsoon climate zone (Chen et al., 2016). Hefei is a light industrial city and one of the regional comprehensive transportation hubs in China, with a total resident population of 7.87 million and built area of 428 km2 in the urban area (Li et al., 2011; Gu et al., 2018). In this study, we randomly

Concentration of heavy metals in indoor dust

The concentrations (mg/kg) of heavy metals (Cd, Cr, Mn, Ni, Pb, Sb, V, and Zn) in indoor dust in different zones are shown in Table 5. The concentration values were ranked in the order of Zn (655.31 ± 323.64)>Mn (176.85 ± 63.47)>Pb (95.39 ± 57.22)>Cr (29.45 ± 12.78)>Ni (26.10 ± 9.37)>V (18.00 ± 7.46)>Cd (4.39 ± 4.38)>Sb (2.00 ± 1.29). The sequence was similar to that of a previous study in Hefei (Ali et al., 2018). The concentrations of heavy metals in indoor dust in these functional areas were

Conclusions

The present study investigated the total concentrations and different chemical fractionations of Cd, Cr, Mn, Ni, Pb, Sb, V, and Zn in indoor dust from three different functional zones in Hefei. The mean metal concentrations in indoor dust decreased in the following order: Zn > Mn > Pb > Cr > Ni > V > Cd > Sb. Cd, Pb, and Zn mainly existed in the mobile fractions (F1, F2, or F3). Among these elements, Cd and Zn existed mainly in the form of F1, while Pb mainly existed in the form of F2. Cr and V

Acknowledgments

The authors acknowledge the support from the National Natural Science Foundation of China (NO. 41173032 and NO. 41373110), the National Postdoctoral Program for Innovative Talents (BX20180287) and the China Postdoctoral Science Foundation (2018M640589). We acknowledge editors and reviewers for polishing the language of the paper and for in-depth discussion.

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