A new methodology for studying dynamics of aerosol particles in sneeze and cough using a digital high-vision, high-speed video system and vector analyses.

Microbial pathogens of respiratory infectious diseases are often transmitted through particles in sneeze and cough. Therefore, understanding the particle movement is important for infection control. Images of a sneeze induced by nasal cavity stimulation by healthy adult volunteers, were taken by a digital high-vision, high-speed video system equipped with a computer system and treated as a research model. The obtained images were enhanced electronically, converted to digital images every 1/300 s, and subjected to vector analysis of the bioparticles contained in the whole sneeze cloud using automatic image processing software. The initial velocity of the particles or their clusters in the sneeze was greater than 6 m/s, but decreased as the particles moved forward; the momentums of the particles seemed to be lost by 0.15-0.20 s and started a diffusion movement. An approximate equation of a function of elapsed time for their velocity was obtained from the vector analysis to represent the dynamics of the front-line particles. This methodology was also applied for a cough. Microclouds contained in a smoke exhaled with a voluntary cough by a volunteer after smoking one breath of cigarette, were traced as the visible, aerodynamic surrogates for invisible bioparticles of cough. The smoke cough microclouds had an initial velocity greater than 5 m/s. The fastest microclouds were located at the forefront of cloud mass that moving forward; however, their velocity clearly decreased after 0.05 s and they began to diffuse in the environmental airflow. The maximum direct reaches of the particles and microclouds driven by sneezing and coughing unaffected by environmental airflows were estimated by calculations using the obtained equations to be about 84 cm and 30 cm from the mouth, respectively, both achieved in about 0.2 s, suggesting that data relating to the dynamics of sneeze and cough became available by calculation.

High-resolution modeling and evaluation of ozone air quality of Osaka using MM5-CMAQ system.

High-resolution modeling approach is increasingly being considered as a necessary step for improving the monitoring and predictions of regional air quality. This is especially true for highly urbanized region with complex terrain and land-use. This study uses Community Multiscale Air Quality (CMAQ) model coupled with MM5 mesoscale model for a comprehensive analysis to assess the suitability of such high-resolution modeling system in predicting ozone air quality in the complex terrains of Osaka, Japan. The 1-km and 3-km grid domains were nested inside a 9-km domain and the domain with 1-km grid covered the Osaka region. High-resolution Grid Point Value-Mesoscale Model (GPV-MSM) data were used after suitable validation. The simulated ozone concentrations were validated and evaluated using statistical metrics using performance criteria set for ozone. Daily maxima of ozone were found better simulated by the 1-km grid domain than the coarser 9-km and 3-km domains, with the maximum improvement in the mean absolute gross error about 3 ppbv. In addition, 1-km grid results fared better than other grids at most of the observation stations that showed noticeable differences in gross error as well as correlation. These results amply justify the use of the integrated high-resolution MMS-CMAQ modeling system in the highly urbanized region, such as the Osaka region, which has complex terrain and land-use.

Biogenic volatile organic compound emission potential of forests and paddy fields in the Kinki region of Japan.

The standard biogenic volatile organic compound (BVOC) emissions from 10 Japanese plant species (Quercus serrata, Quercus crispula, Fagus crenata, Quercus acutissima Carruthers, Quercus glauca, Quercus myrsinaefolia, Cryptomeria japonica, Chamaecyparis obtusa, Pinus densiflora, and rice [Oryza sativa]) were measured. These species were selected due to their abundance in the estimated domain (47,000 km(2)) of the Kinki region. BVOC emission experiments were conducted in a growth chamber where temperature and light intensity can be controlled. Temperature was set at the average summer temperature in Osaka and at 5 degrees C above average. Light intensity was set at 1000, 335, and 0 micromol m(-2)s(-1) during day time. The amount of BVOC emission was high around noon due to the rise of ambient temperature. It was also found that the total emission rates and compositions of BVOC varied significantly among the plant species. Q. serrata, Q. crispula, F. crenata, Q. acutissima Carruthers, Q. glauca, and Q. myrsinaefolia emitted isoprene and showed emission dependence on light intensity and temperature. C. japonica, P. densiflora, C. obtusa, and O. sativa emitted monoterpenes and also showed emission dependence on temperature; however, only C. japonica and P. densiflora showed emission dependence on light intensity. Using BVOC emissions data from 10 plant species and forest data, BVOC emission potential maps were made. The emission of isoprene and monoterpenes from the Kinki region were estimated to be 596 and 54 ton h(-1), respectively. Seasonal and diurnal variations of BVOC emissions potential were also estimated. Of note, though the amount of monoterpenes from O. sativa is small, it contributes approximately 5% to the total monoterpene emissions due to the huge land area covered by paddy fields.

Impacts of converting from leaded to unleaded gasoline on ambient lead concentrations in Jakarta metropolitan area.

Total suspended particulate mater (TSP) concentrations were monitored for one year from July 2000 and for one year from April 2003 in Jakarta City. Thirteen elemental TSP components, aluminum (Al), sodium (Na), iron (Fe), lead (Pb), potassium (K), zinc (Zn), titanium (Ti), manganese (Mn), bromine (Br), copper (Cu), chromium (Cr), nickel (Ni), and vanadium (V) were analyzed by a sequential X-ray fluorescence spectrometer. Al, Na, Fe, K, and Pb were major components at most of the sampling locations in 2000. However, only Pb in 2003 dramatically decreased to one tenth. The phase-out of leaded gasoline began on July 1, 2001 in Jakarta City and lead content in gasoline decreased to one tenth, too. The decrease in Pb concentration was a result of the phase-out of leaded gasoline, as lead emissions mainly are exhaust gas from vehicles.

Investigation of air pollution concentration in Kathmandu valley during winter season.

The monthly concentrations of NO2, NOx, SO2 and O3 measured by a passive sampler from February 2003 to January 2004 showed that the air pollution during the winter season in Kathmandu valley was higher than the summer season. The O3 level was found the highest during April, May and June due to strong radiation. The hourly concentrations of NO2, NOx, O3 and suspended particulate matter (SPM) were also measured by automatic instruments on December 2003. Temperature at the height of 60 m and 400 m at Raniban Mountain in the northwest of Kathmandu valley was measured on February 2001 in the winter season and the average potential temperature gradient was estimated from observed temperature. Wind speed was also measured at the department of hydrology, airport section, from 18 February to 6 March 2001. It was found that the stable layer and the calm condition in the atmosphere strongly affected the appearance of the maximum concentrations of NO2 and SPM in the morning, and that the unstable layer and the windy condition in the atmosphere was considerably relevant to the decrease of air pollution concentrations at daytime. The emission amounts of NOx, HCs and total suspended particle(TSP) from transport sector in 2003 were estimated from the increasing rate of vehicles on the basis of the emission amounts in 1993 to be 3751 t/a, 30570 t/a and 1317 t/a, respectively. The diurnal concentrations in 2003 calculated by the two-layers box model reproduced the characteristics of air pollution in Kathmandu valley such as the maximum value of O3 and its time, the maximum value of NO in the morning, and the decrease of NO and NO2 at daytime. The comparison with the concentrations in 1993 calculated suggested that the main cause of air pollution was the emission from transport sector.