The objective of this study was to investigate the influence of metals bound to airborne particles on pulmonary function of schoolchildren. Morning Peak Expiratory Flow (PEF) was measured daily in 399 schoolchildren, aged between eight and nine, from April to May 2012, and the levels of Ca, Fe, K, Mg, Mn, and Ti (natural metals) and Cd, Cu, Pb, V and Zn (anthropogenic metals) bound to airborne particles were monitored. A linear mixed model was used to estimate the association of PEF with metals bound to airborne particles. Natural and anthropogenic metals (except for Ba, Ni and Na) bound to airborne particles had significant negative associations with PEF. Metals bound to airborne particles may decrease pulmonary function of children.

•    Airborne particles
•    Metals
•    PEF
•    School children

•    Airborne particles
•    Metals
•    PEF
•    School children

The objective of this study was to investigate the influence of metals bound to airborne particles on pulmonary function of schoolchildren. Morning Peak Expiratory Flow (PEF) was measured daily in 399 schoolchildren, aged between eight and nine, from April to May 2012, and the levels of Ca, Fe, K, Mg, Mn, and Ti (natural metals) and Cd, Cu, Pb, V and Zn (anthropogenic metals) bound to airborne particles were monitored. A linear mixed model was used to estimate the association of PEF with metals bound to airborne particles. Natural and anthropogenic metals (except for Ba, Ni and Na) bound to airborne particles had significant negative associations with PEF. Metals bound to airborne particles may decrease pulmonary function of children.

Watanabe M, Kurai J, Noma H, Watanabe T, Minato S, et al. (2015) Exposure to Metals Bound to Particles and Pulmonary Function of School Children in Western Japan. Ann Public Health Res 2(1): 1015.

CIS: Confidence Intervals; IQR: Interquartile Range; LIDAR: Light Detection and Ranging; PEF: Peak Expiratory Flow.

The large scale and long-range transport of aerosols such as sand dust from East Asia to Japan is referred to as an Asian dust storm (ADS) [1-4]. These aerosols include metal components, chemicals, and microorganisms [1-4]. A study in South Korea found that exposure to metals bound to particles during an ADS period reduced pulmonary function in children [5]. In Japan, the effects on the respiratory system of exposure to metals bound to particulate matter have not been evaluated in detail, irrespective of the origin of these particles. Light Detection and Ranging (LIDAR) depolarization measurements performed simultaneously at two wavelengths can be used to identify nonspherical dust particles, which are mineral dust particles, and spherical aerosols such as organic aerosols and inorganic sulfates and nitrates [2,6] LIDAR are made continuously in 23 locations in Japan, South Korea, China, Mongolia and Thailand and monitor the amount of sand dust particles transported from East Asia to Japan. In this study, we investigated the association between exposure to metals bound to airborne particles and pulmonary function of schoolchildren, as the first such study in Japan. We also studied the difference of the effects of metals bound to airborne particles on pulmonary function based on the level of sand dust particles using LIDAR data.

Subjects

A longitudinal study was conducted to monitor daily morning PEF of schoolchildren in April and May 2012. All 401 fourth grade students aged between eight and nine years old from 4 elementary schools in Matsue, Japan were included in the study. Gender, height, weight, and presence of asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, and food allergies were recorded for all subjects in March 2012. The study was approved by the institutional ethics committee (Ethics Committee of the Faculty of Medicine, Tottori University, Approval Number 1764) and by the Parent Teacher Association (PTA) of each elementary school. Children and their parents were informed by teacher and gave written consent.

Monitoring mineral dust particles, non-mineral dust particles, and metals bound to airborne particles

LIDAR is installed in Matsue City and used by the Japanese Ministry of the Environment, and we referred to data of mineral and non-mineral dust particles levels from the Matsue City observatory. From April to May 2012, airborne particles were collected every day at Tottori Prefectural Institute of Health and Environment, Yurihama, Tottori using a high-volume air sampler (HV-1000R; Shibata Co., Ltd., Tokyo, Japan). The daily concentrations of Ba, Ca, Fe, K, Mg, Mn, Na, and Ti in airborne particles were measured as natural elements, and the concentrations of Cd, Cu, Ni, Pb, V, and Zn as anthropogenic elements. Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Ti and Zn were measured by inductively coupled plasma atomic emission spectrometry. Ni, V, and Pb were measured using electrothermal atomic absorption spectrometry.

Statistical analysis

Linear mixed models that accounted for correlations among repeated measurements within a subject were used to estimate the effect of exposure to metals bound to particles on the daily PEF of children. The linear mixed models included a random intercept for subjects in the analysis, individual characteristics, and meteorological variables. Estimates are given as the absolute difference in PEF per interquartile range (IQR) change in exposure with 95% confidence intervals (CIs). The differences in metal elements between heavy dust days and non-heavy dust days were analyzed by t-test. All analyses were performed using R ver. 3.0.3 (R Foundation for Statistical Computing, Vienna, Austria). All quoted P values are two-sided and the significance level was 0.05.

Two subjects were excluded from the study due to failure to keep a daily record of PEF. The characteristics of the remaining 399 children are shown in (Table 1). Using LIDAR data, a heavy dust day was determined by the level of sand dust particles higher than 0.032 km-1, which was the average plus 1 standard deviation from April to May. Six heavy dust days were identified. (Table 2) shows the differences in the levels of metal elements between non-heavy and heavy dust days. There were significant differences in the levels of Ca, Fe, K, Mn, Ti, Cd and V. The results of changes in PEF for IQR increases in exposure to mineral dust particles, air pollution aerosols, and metals bound to particles are presented in (Table 3). The concentrations of mineral dust particles and non-mineral dust particles, and the levels of Ca, Fe, K, Mg, Mn, and Ti (natural elements) and Cd, Cu, Pb, V and Zn (anthropogenic elements) all had significant negative associations with PEF. In contrast, Ba levels had a significant positive association with PEF, and the levels of Na and Ni had no relationship with PEF.

Heavy dust day was determined by the level of sand dust particle of higher than 0.032 km-1, which was average plus 1 standard deviation during study period, and six heavy dust days were identified

Table 1: Characteristics of children.

Data are shown as the mean ±S.D.

Table 2: Differences of the levels of metal elements between non-heavy and heavy dust days.

Data are shown as the mean ±S.D.

The long-range transports of aerosols from East Asia to Japan are able to be classified into several types according to the amount of airborne particles [1]. The quantity of metal is important for composition of aerosols. However, how metals bound to particles exposure influence pulmonary function of children remains unclear. This study shows that increased a lot of metals bound to airborne particles, except for Ba, Ni and Na, caused significant reduce of pulmonary function in schoolchildren irrespective of natural and anthropogenic metals. We also found a significant relationship of PEF with the concentration of mineral dust particles based on LIDAR data. As far as we know, this is the first report to show a clear association between decreased pulmonary function in schoolchildren and metals bound to particulate matter in Japan. Sand dust clearly impairs pulmonary function, [7] and includes chemicals, and microorganisms [1-4] However, the substances bound to particles that play an important role in this effect have remained unclear. Based on previous work, [3-5] we classified metal components into natural and anthropogenic, based on their source. We were unable to find a significant difference in potency for reduction of pulmonary function in children between natural and anthropogenic metals; [5] similarly to Hong et al. Metal elements from natural sources have the potential to deteriorate pulmonary function. However, many studies have shown that human health is susceptible to anthropogenic elements such as Cd, Cu, Pb, V and Zn [8] Metals from anthropogenic sources may augment the effects of those from natural sources. A further study is required to examine this association, with a focus on the metals bound to particulate matter and the roles these metals play in decreasing pulmonary function.

Recently, China has had high levels of air pollution due to rapid industrial expansion and an increased number of cars on the road. Chen and colleagues reported on the “Great Smog of 2013” in Beijing, China, when residents were exposed to the worst air quality on record [9]. China’s industrial expansion has resulted in the long-range transportation of aerosols with higher concentration of anthropogenic elements [10]. It is currently difficult to monitor particulate matter coming from East Asia to Japan in a quantitative manner. LIDAR distinguishes between mineral and non-mineral dust particles by measuring the degree of scattered reflected polarization laser light at <1 km above ground, and can measure long-range transported sand dust particles. The concentration of Pb in aerosols has markedly decreased in Japan, but remained high in East Asia [11,12] Several studies have suggested that monitoring the Pb level is important for evaluating particulate matter moving from East Asia to Japan [11,12]. However, in this study, there was not a significant difference in the level of Pb between normal days and heavy dust days. Monitoring the levels of Cd and V may be more useful than Pb.

Recently, China has had high levels of air pollution due to rapid industrial expansion and an increased number of cars on the road. Chen and colleagues reported on the “Great Smog of 2013” in Beijing, China, when residents were exposed to the worst air quality on record [9]. China’s industrial expansion has resulted in the long-range transportation of aerosols with higher concentration of anthropogenic elements [10]. It is currently difficult to monitor particulate matter coming from East Asia to Japan in a quantitative manner. LIDAR distinguishes between mineral and non-mineral dust particles by measuring the degree of scattered reflected polarization laser light at <1 km above ground, and can measure long-range transported sand dust particles. The concentration of Pb in aerosols has markedly decreased in Japan, but remained high in East Asia [11,12] Several studies have suggested that monitoring the Pb level is important for evaluating particulate matter moving from East Asia to Japan [11,12]. However, in this study, there was not a significant difference in the level of Pb between normal days and heavy dust days. Monitoring the levels of Cd and V may be more useful than Pb.

This study has a limitation that Yurihama is slightly away from Matsue. However, it is the most suitable area closest to Matsue to monitor particulate matter from East Asia because Yurihama is rural and has no source of air pollutants, except for motor vehicles.

Table 3: Associations of PEF with interquartile increases of mineral dust particles, air pollution aerosols, and metals bound to particles in linear mixed-effects models.

IQR: interquartile range; CI: confidence interval; LIDAR: Light Detection and Ranging

The authors declare that there is no conflict of interests regarding the publication of this paper. The study was supported by the Environmental Research and Technology Development Fund (5C-1154 and 5-1453) of the Japanese Ministry of the Environment.

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