Yoshiko Yoda

Effects of airborne particulate matter on respiratory morbidity in asthmatic children.

Background The effects of airborne particulate matter (PM) are a major human health concern. In this panel study, we evaluated the acute effects of exposure to PM on peak expiratory flow (PEF) and wheezing in children. Methods Daily PEF and wheezing were examined in 19 asthmatic children who were hospitalized in a suburban city in Japan for approximately 5 months. The concentrations of PM less than 2.5 µm in diameter (PM2.5) were monitored at a monitoring station proximal to the hospital. Moreover, PM2.5 concentrations inside and outside the hospital were measured using the dust monitor with a laser diode (PM2.5(LD)). The changes in PEF and wheezing associated with PM concentration were analyzed. Results The changes in PEF in the morning and evening were significantly associated with increases in the average concentration of indoor PM2.5(LD) 24 h prior to measurement (-2.86 L/min [95%CI: -4.12, -1.61] and -3.59 L/min [95%CI: -4.99, -2.20] respectively, for 10-µg/m3 increases). The change in PEF was also significantly associated with outdoor PM2.5(LD) concentrations, but the changes were smaller than those observed for indoor PM2.5(LD). Changes in PEF and concentration of stationary-site PM2.5 were not associated. The prevalence of wheezing in the morning and evening were also significantly associated with indoor PM2.5(LD) concentrations (odds ratios = 1.014 [95%CI: 1.006, 1.023] and 1.025 [95%CI: 1.013, 1.038] respectively, for 10-µg/m3 increases). Wheezing in the evening was significantly associated with outdoor PM2.5(LD) concentration. The effects of indoor and outdoor PM2.5(LD) remained significant even after adjusting for ambient nitrogen dioxide concentrations. Conclusion Indoor and outdoor PM2.5(LD) concentrations were associated with PEF and wheezing among asthmatic children. Indoor PM2.5(LD) had a more marked effect than outdoor PM2.5(LD) or stationary-site PM2.5.

Decline of ambient air pollution levels due to measures to control automobile emissions and effects on the prevalence of respiratory and allergic disorders among children in Japan.

BACKGROUND In Japan, air pollution due to nitrogen oxides (NOx) and particulate matter (PM) has been gradually reduced since control measures based on the Automobile NOx/PM law were enforced beginning in 2001. The effects of decrease in air pollutants due to the control measures during the past decade on the prevalence of respiratory and allergic disorders such as asthma in children were evaluated. METHODS Using data of 618,973 children collected in 28 regions of Japan from 1997 to 2009, we evaluated whether reductions in the concentrations of nitrogen dioxide (NO2) and suspended particulate matter (SPM) contribute to the decrease in the prevalence of asthma, wheezing, bronchitis, allergic rhinitis, and atopic dermatitis by multiple linear regression analysis, including adjustments for related factors. RESULTS The annual rates of decrease in air pollution in the PM-law-enforced areas were 2.0 and 2.5 times higher for NO2 and SPM, respectively, compared with those in the non-enforced areas. The prevalence of asthma decreased significantly at -0.073% per year in the areas in which measures based on the Automobile NOx/PM law were taken but not in area where such measures were not applied. Multiple linear regression analysis showed a reduction in the ambient air pollution was significantly associated with a reduction in the prevalence of asthma, with a rate of 0.118% [95% confidence interval (CI): 0.012-0.225] per 1 ppb for NO2, and 0.050% [95% CI: 0.020-0.080] per 1 μg/m(3) for SPM. An increase in the ambient air pollution was associated with an increase in the prevalence of atopic dermatitis of 0.390% [95% CI: 0.107-0.673] per 1 ppb for NO2, 0.141% [95% CI: 0.058-0.224] per 1 μg/m(3) for SPM. The changes in the prevalence of wheezing and allergic rhinitis were not significantly correlated with changes in air pollutant concentrations. CONCLUSIONS The enforcement of measures to control automobile emissions based on the Automobile NOx/PM law was shown to have reduced air pollution and contributed to decreases in the prevalence of respiratory and allergic disorders in 3-year-old children.

Exposure to air pollution and meteorological factors associated with children’s primary care visits at night due to asthma attack: case-crossover design for 3-year pooled patients

Objective We examined the association of outdoor air pollution and meteorological parameters with primary care visits (PCVs) at night due to asthma attack. Setting A case-crossover study was conducted in a primary care clinic in Himeji City, Japan. Participants Participants were 1447 children aged 0–14 years who visited the clinic with an asthma attack from April 2010 until March 2013. Exposure Daily concentrations of air pollutants and meteorological parameters were measured. Primary outcome PCVs at night due to asthma attack. A conditional logistic regression model was used to estimate ORs of PCVs per unit increment of air pollutants or meteorological parameters (the per-unit increments of particulate matter with an aerodynamic diameter ≤2.5 µm (PM2.5) and ozone were 10 μg/m3 and 10 ppb, respectively). Analyses took into consideration the effects of seasonality. Results We noted an association between PCVs and daily ozone levels on the day before a PCV (OR=1.17; 95% CI 1.01 to 1.35; p=0.04), as well as between PCVs and 3-day mean ozone levels before a PCV (OR=1.29; 95% CI 1.00 to 1.46; p=0.04), from April until June. We also observed an association between PCVs and daily PM2.5 levels on the day before a PCV from December until March (OR=1.16; 95% CI 1.01 to 1.33; p=0.05). Meteorological parameters, such as hours of sunshine from September until November, atmospheric pressure from April until June, and temperature from April until August, were also found to be associated with PCVs. Conclusions The findings in the present study supported an association between ozone and PCVs and suggest that certain meteorological items may be associated with PCVs.

Storage conditions for stability of offline measurement of fractional exhaled nitric oxide after collection for epidemiologic research

BackgroundThe measurement of fractional concentration of nitric oxide in exhaled air (FeNO) is valuable for the assessment of airway inflammation. Offline measurement of FeNO has been used in some epidemiologic studies. However, the time course of the changes in FeNO after collection has not been fully clarified. In this study, the effects of storage conditions on the stability of FeNO measurement in exhaled air after collection for epidemiologic research were examined.MethodsExhaled air samples were collected from 48 healthy adults (mean age 43.4 ± 12.1 years) in Mylar bags. FeNO levels in the bags were measured immediately after collection. The bags were then stored at 4°C or room temperature to measure FeNO levels repeatedly for up to 168 hours.ResultsIn the bags stored at room temperature after collection, FeNO levels were stable for 9 hours, but increased starting at 24 hours. FeNO levels remained stable for a long time at 4°C, and they were 99.7% ± 7.7% and 101.3% ± 15.0% relative to the baseline values at 24 and 96 hours, respectively. When the samples were stored at 4°C, FeNO levels gradually decreased with time among the subjects with FeNO ≥ 51 ppb immediately after collection, although there were almost no changes among the other subjects. FeNO levels among current smokers increased even at 4°C, although the values among ex-smokers decreased gradually, and those among nonsmokers remained stable. The rate of increase was significantly higher among current smokers than among nonsmokers and ex-smokers from 9 hours after collection onwards.ConclusionsStorage at 4°C could prolong the stability of FeNO levels after collection. This result suggests that valid measurements can be performed within several days if the samples are stored at 4°C. However, the time course of the changes in FeNO levels differed in relation to initial FeNO values and cigarette smoking.

Airborne endotoxin concentrations in indoor and outdoor particulate matter and their predictors in an urban city

Endotoxins are an important biological component of particulate matter and have been associated with adverse effects on human health. There have been some recent studies on airborne endotoxin concentrations. We collected fine (PM2.5 ) and coarse (PM10-2.5 ) particulate matter twice on weekdays and weekends each for 48 hour, inside and outside 55 homes in an urban city in Japan. Endotoxin concentrations in both fractions were measured using the kinetic Limulus Amebocyte Lysate assay. The relationships between endotoxin concentrations and household characteristics were evaluated for each fraction. Both indoor and outdoor endotoxin concentrations were higher in PM2.5 than in PM10-2.5 . In both PM2.5 and PM10-2.5 , indoor endotoxin concentrations were higher than outdoor concentrations, and the indoor endotoxin concentrations significantly correlated with outdoor concentrations in each fraction (R2 =0.458 and 0.198, respectively). Indoor endotoxin concentrations in PM2.5 were significantly higher in homes with tatami or carpet flooring and in homes with pets, and lower in homes that used air purifiers. Indoor endotoxin concentrations in PM10-2.5 were significantly higher in homes with two or more children and homes with tatami or carpet flooring. These results showed that the indoor endotoxin concentrations were associated with the household characteristics in addition to outdoor endotoxin concentrations.

Acute effects of air pollutants on pulmonary function among students: a panel study in an isolated island

BackgroundMany epidemiological studies on the health effects of air pollutants have been carried out in regions with major sources such as factories and automobiles. However, the health effects of air pollutants in regions without major sources remain unclear. This study investigated the acute effects of ambient air pollution on pulmonary function among healthy students in an isolated island without major artificial sources of air pollutants.MethodsA panel study was conducted of 43 healthy subjects who attended a school in an isolated island in the Seto Inland Sea, Japan. We measured the forced expiratory volume in 1 s (FEV1) and peak expiratory flow (PEF) every morning for about 1 month in May 2014. Ambient concentrations of particulate matter ≤ 2.5 μm in diameter (PM2.5), particulate matter between 2.5 and 10 μm in diameter (PM10-2.5), black carbon (BC), ozone (O3), and nitrogen dioxide (NO2) were measured. The associations between the concentrations of air pollutants and pulmonary function were analyzed using mixed-effects models.ResultsA decrease in FEV1 was significantly associated with BC concentrations (−27.28 mL [95%confidence interval (CI):−54.10,−0.46] for an interquartile range (IQR) increase of 0.23 μg/m3). The decrease in PEF was significantly associated with indoor O3 concentrations (−8.03 L/min [95% CI:−13.02,−3.03] for an IQR increase of 11 ppb). Among subjects with a history of allergy, an increase in PM2.5 concentrations was significantly associated with low FEV1. In subjects with a history of asthma, an inverse association between the indoor O3 concentration and pulmonary function was observed.ConclusionsOur results demonstrate that increases in BC and O3 concentrations have acute effects on the pulmonary function among students in an isolated island without major artificial sources of air pollutants.

Personal and Atmospheric Concentrations of Ozone in Southeastern Hyogo Prefecture, Japan

Twenty-one data sets composed of readings collected by atmospheric ozone monitors worn by individuals on their clothing and installed outside their home or office were collected using Ogawa passive ozone samplers in southeastern Hyogo prefecture, Japan from September 12 to 13, 2011. The concentrations of personal and outdoor ozone ranged from not detectable to 23.2 ppb and from 4.7 to 38.3 ppb, respectively. The mean concentration of personal exposure to ozone was 3.7 ppb and was significantly lower than that of outdoor ozone (18.5 ppb). This suggests that the concentrations of outdoor ozone affect personal ozone exposure. However, in this study, we found no correlation between the concentrations of personal ozone and the total time spent outdoors or the time of day the individual was outside. In contrast, the mean concentrations of outdoor ozone were similar to those of ozone measured at the 12 nearest Ambient Monitoring Stations (AMSs). However, when the AMS was situated near a main road, the regional ozone levels were underestimated.

Physicochemical characterization and size-resolved source apportionment of airborne particles in Himeji City, Japan

As a part of epidemiological study on the effects of the chemical composition of airborne particulate matter (PM) and ozone on asthma attacks, we carried out size-resolved sampling of PM in Himeji City, Japan and elemental and ionic composition analyses of the PM samples. Size-resolved PM was collected using a 3-stage NLAS impactor (Tokyo Dylec Co., Ltd.; particle cut size at sampling stages was 10, 2.5 and 1.0 μm for a flow rate of 3 L/min) with a 1-week sampling interval from November 2009 to May 2012. Concentrations of several elemental and ionic species in the PM samples were determined by PIXE and ion chromatography analysis, respectively. In addition, source apportionment analysis of the PM was performed by positive matrix factorization (PMF) model using the analytical data of size-resolved particles. The research results are important for the physicochemical characterization of PM in the atmosphere, enabling evaluation of various PM emission sources and atmospheric processes. Of particular note is that the PM10 consisted mainly of NO3- and SO42-, and PM2.5 consisted only of SO42-. This is believed to suggest the different formation processes of NO3- and SO42-. Based on the results from the PMF model analysis, the particles larger then PM2.5 were estimated to have been from soil and sea salt particles. On the other hand, the particles smaller than PM2.5 were estimated to have been from soot, smoke and secondary particles. In particular, the majority of particle smaller than PM1.0 were estimated to be secondary sulfate particles.

YEAR-ROUND BEHAVIOR FOR INORGANIC COMPOSITION OF SIZE-RESOLVED AIRBORNE PARTICLES IN HIMEJI CITY, JAPAN

As a part that, an epidemiological study on the effects of physicochemical characterization of airborne particulate matter (PM) and ozone on asthma attacks, we carried out size-resolved sampling of PM in Himeji City, and elemental and ionic composition analyses of the PM sample. Size-resolved PM was collected using a 3-stage NLAS impactor (Tokyo Dylec Co., Ltd.; particle cut size at sampling stages was 10, 2.5 and 1.0 μm for a flow rate of 3 L/min) with a one-week base sampling interval, and the PM sampling was begun in November, 2009. Concentrations of several elemental and ionic species in the PM sample were determined by PIXE and ion chromatography analysis, respectively. The research results are important for the physicochemical characterization of PM in atmosphere, enabling detailed analysis of the year-round behavior. Of particular note, is that the PM10 was mainly NO3- and SO42- and PM2.5 was only SO42-. This is believed to suggest the different formation processes of NO3- and SO42-.