Seasonal Source Identication And Source-Specic Health Risk Assessment of Pollutants On Road Dust In Tianjin

Human exposure to metals on road dust might have potential health risks through 17 touching, ingesting, and inhaling. There were limited studies to link seasonal emission 18 sources to health risks from metals on road dust. In this study, metals on road dust from 19 different functional areas were seasonally monitored. The pollutant sources in study 20 city varied slightly with the seasons, but the major pollutant source in the particular 21 study site were significantly affected by the seasons. By combining the source 22 apportionment model (PMF), line sources model and health risk models (HI: Hazard 23 index and ILCR: Incremental Lifetime Carcinogenic risk), industrial and construction 24 activity was identified as the crucial source of both the pollutants on road dust (29% - 25 47%), and the HI for adults (27% - 45%) and children (41% - 50%) in different seasons. The traffic non-exhaust emission dominated in the carcinogenic risks for children in 27 spring (45%) and summer (36%). Factors such as seasons, particle size, metal 28 bioavailability, human exposure time, and exposure area were all taken into 29 consideration to avoid overestimating or underestimating health risks. The carcinogenic 30 risks for children (1.6 E-06) and adults (2.8 E-06) exposed to Cr both exceed the 31 minimum threshold (10 -6 ). Measured metals mainly posed hazard to human health 32 through ingestion route. Pb and Mn, Fe and Mn were the main harmful elements that 33 induced non-carcinogenic risks for adults and children, respectively. Effectively identifying the source-specific health risks in different seasons will help in the formulation of adaptive strategies to diminish the potential risks.

and metals (Wang et al., 2019b). Obviously, different models have different advantages 69 and disadvantages (Huang et al., 2018c). In order to quantitatively analyze the 70 contribution proportion of pollution sources on metals and human health risks, the PMF 71 model was selected in this study (Men et al., 2019). This model considers the 72 uncertainty of sampling and data analysis, and could quantify the source contribution 73 to meet the research goals. 74 The metals, such as Fe, Mn, Pb, Zn, Cr and Cu, are ubiquitous on road dust and 75 have potential adverse effects on human health, including cell injury, inflammation or 76 heart diseases (Huang et al., 2018b;Men et al., 2020). The Hazard Index (HI) model 77 was selected to assess the potential non-carcinogenic risk of human exposure to metals 78 (Wahab et al., 2020). Adults and children exposed to the road dust made pollutants 79 easier to enter the human body through three pathways: ingestion (exposure of mouth 80 and digestive tract), inhalation and dermal contact (Skrbic et al., 2019). Cr and Pb were 81 not the essential elements for living and showed higher toxic to animals, plants and 82 human beings (Wahab et al., 2020). The Incremental Lifetime Carcinogenic risk (ILCR) 83 model was used to assess the carcinogenic risks of Cr and Pb to human health which 84 has been widely applied in many studies (Liu et al., 2015). However, in previous studies, 85 a common practice in calculating the daily exposure dose (ADD) of road dust through 86 the inhalation route was to classify it as soil using a particulate emission factor (PEF) 87 (Hou et al., 2019). This might underestimate the amount of inhalation or ingestion, 88 because it ignored the impact of particle size and severe traffic disruption.

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Comprehensive and mature models have been developed in air pollution simulation,  Accurate source control is the key to mitigating the health risks of metal exposure.

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Affected by the characteristics of the functional areas and seasons, this study 101 emphasized that the seasonal sources of pollutants in each functional area might be 102 significantly distinctive. In addition, many studies have focused on the source 103 apportionment of pollutants on road dust, but ignored the crucial sources leading to 104 health risks (Men et al., 2020). Due to the different toxic reaction factors of metals, the 105 major sources of metals on road dust might not generate the major risks to human health 106 (Liu et al., 2015). And the crucial sources of health risks might also be affected by the 107 seasons. The combination of the PMF model and the risk assessment model could 108 achieve accurate and effective evaluation of the source apportionment of health risks.

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In order to mitigate hazardous pollutants on road dust effectively, the objectives of  were selected in this study due to the significant differences in the population and traffic 132 volume as shown in Figure S1 and Table S1. There were large construction activities 133 near the traffic area during study period.  Table S1. Thereout, an average of 15 samples  (Table S2) were evaluated for risks through three

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PMF is a multivariate factor analysis tool that decomposes a matrix of speciated 170 sample data into two matrices: factor contributions (G) and factor profiles (F). These 171 factor profiles need to be interpreted by researchers to identify the source types that 172 may be contributing to the samples using measured source profile information, and 173 emissions or discharge inventories. As input files, data set can be viewed as a data  Table S3.

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The signal-to-noise ratio (S/N) of all elements was >1.0. The values of scaled 197 residuals for all the elements were between−3 and +3, and were normally distributed.

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The model Q (robust) and Q (true) values were fitted and compared, and the difference 199 was less than 3% which meant the model run stably and the data fit well. The standard  The potential health effects of metals were described as non-carcinogenic and

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SA is the exposed skin area in cm 2 . AFd is the skin adherence factor in mg·cm -2 ·day -1 .

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BW is the body weight of human and child in kg. AT is the average exposure time in 248 hours (h). ABS is the dermal absorption factor (unitless). The parameters are shown in 249   Table S4a.
Where, ILCR is the incremental lifetime cancer risk. LADD is the lifetime average 276 daily dose exposed by the inhalation pathways (μg/m 3 ). ET is the exposure time (h/d).   Table S4b.  (Table S5). This might be related to the extensive human activities in summer   416 The health risks of road dust were evaluated by summarizing the risks of different 417 groups of people exposed to metals on road dust in various functional areas and seasons.

Seasonal non-carcinogenic risk health assessment
418 Table S8 shows the Hazard Quotient (HQ) and Hazard Index (HI) for adults and 419 children exposed to six metals on road dust through three pathways. The potential health an essential element to human body. There have been many reports on the relationship 439 between excess iron and heart disease (Ghafourian et al., 2020;Wood, 2004).

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In addition, the potential non-carcinogenic risks to children was found to be higher 441 than that of adults. Children might be more vulnerable than adults for ingestion rate, dust were all below the risk threshold. However, it was worth noting that high non-446 cancer risks exposed to six metals were undoubtedly a serious potential peril to children and Cu in the residential area all posed threat to human health through dermal contact.

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Due to the low traffic volume in residential area, the potential health risks exposed to 486 various metals through direct inhalation were relatively low. Timely road sweeping 487 carried out in central commercial street and thus the accumulated particle load was less.

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Therefore, the health risks caused by dermal contact in central commercial street were 489 low, even if the traffic volume was heavy.  Identifying specific contribution sources for risk assessment is of great significance for 544 effectively controlling risk sources and reducing potential risk. respectively. The cancer risks for adults and children exposed to Cr exceeded the 551 minimum threshold. Higher cancer risks for adults and children exposed to Pb were 552 shown in summer and autumn, while shown in winter exposed to Cr. Five major  Not applicable.

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Availability of data and materials 578 The authors declare that all the datasets generated during and/or analysed during 579 the current study are available in the article and its SI Appendix.

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Competing interests 581 The authors declare that they have no competing interests.            Contribution of metals to non-carcinogenic risks of adult through three exposure pathways in different seasons.

Figure 3
Contribution of metals to non-carcinogenic risks of adult through three exposure pathways in different functional areas.

Figure 4
Carcinogenic elements display potential health risks to adults and children in different seasons and functional areas.

Figure 5
Source contributions of metals to Hazard Index (HI) and Incremental Lifetime Cancer Risk (ILCR) for adults and children in different seasons. a) HI for child; b) HI for adult; c) LICR for child; d) LICR for adult.

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