Effects of occupational noise exposure on blood pressure.

We measured 24-hour ambulatory blood pressure and 16-hour noise exposure continuously for 20 automobile workers, and used linear mixed-effects regression models to estimate transient and sustained effects of noise exposure on blood pressure. The occupational noise levels of the high-exposure workers with 85 +/- 8 dBA were significantly higher than those of the low-exposure workers with 59 +/- 4 dBA (P < 0.05). We found a significant difference of 16 +/- 6 mm Hg in sleep-time systolic blood pressure (SBP) existed between 2 exposure groups, and a marginal increase of 1 mm Hg SBP per 1-dBA increase in occupational noise exposure at a 60-minute lag time during work (P = 0.07). Occupational noise exposure had both transient and sustained effects on workers' SBP.

Effect of rise distance on droplets generated from bubble bursting on the surface of chromic acid solutions.

In the processes of chromium electroplating, bursting bubbles are the major sources of chromium droplets that may lead to nasal septum disorders among workers. The gas bubbles form as a result of electrochemical reactions on the surfaces of pieces being plated, rise through the liquid, and then burst into droplets at liquid surfaces. The dimensions of the pieces being plated differ from piece to piece, and therefore the rise distance of the bubbles varies. This study is aimed at evaluating the effect of rise distance on the characteristics of droplets generated from bubbles bursting on the surface of chromic acid solutions by an experimental bubbling system. Two rise distances, 15 and 30 cm, were tested. An aerodynamic particle sizer was used to determine the droplet size distribution over the range of 0.8-30 microm. A Marple personal impactor was employed to collect droplet samples on polyvinyl chloride filters for Cr(VI) analysis. It was found that the Cr(VI) concentrations in droplets increased when the bubble rise distance increased. The result suggests that soluble ions such as Cr(VI) are scavenged by rising bubbles.

An Assessment of Source Contributions to Ambient Aerosols in Central Taiwan.

Ambient aerosols were sampled at three selected sites in the coastal region of central Taiwan to obtain composition data for use in receptor modeling. All the samples were analyzed for 20 elements with an x-ray fluorescence spectrometer. The mass percentage of sulfates in particle samples was determined by ion chromatography, and mass percentages of elemental carbon (EC) and organic carbon (OC) were determined by an elemental analyzer. Because the three sampling sites were located within 25 km of each other, the average chemical compositions were similar for particle samples taken at the three sites on the same day. However, the variation in composition from day to day was significantly influenced by wind direction and change in local sources, such as the burning of agricultural wastes. The abundant species in the coarse fraction (2.5-10 µm) were Al (0.5-4.0 µg/m3), Cl (0.1-4.8 µg/m3), Ca (0.2-3.4 µg/m3), Fe (0.2-2.8 µg/ m3), and K (0.1-1.4 µg/m3), while the abundant species in the fine fraction (<2.5 µm) were S (0.3-3.5 µg/m3), Cl (0.01-1.9 µg/ m3), K (0.04-0.98 µg/m3), organic carbon (0.01-10.5 µg/m3), elemental carbon (0-10.7 µg/m3), and sulfates (1.2-15.7 µg/m3). Calculations for source apportionment were carried out using the CMB7 software developed by the U.S. Environmental Protection Agency (EPA). The main sources for the coarse fraction of ambient aerosols in the region were found to be marine aerosol, coal and fuel oil combustion, burning of agricultural wastes, and paved road dust. The main sources for the fine fraction were burning of agricultural wastes, diesel exhaust, coal and oil combustion, and sulfates. Source apportionment for the fine fraction was relatively sensitive to the types of sources selected for calculations and the compositions of the sources. The problem can be ameliorated by careful examination of possible sources and by use of local source profiles.