ベンゼン等有害揮発性物質の船舶からの排出量低減に関する研究

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International Maritime Organization (IMO) recognized that chronic exposure to very low concentrations of benzene vapors in air of the order of a few parts per million may cause cancer. In order to reduce the health risk of crews to the same level as that of shore-based workers performing comparable tasks, it is necessary to reduce occupational exposure to benzene vapor. To cope with the standard and to prevent the suffering of the people who are engaged in the cargo work and the people who live around the berth, the actual onboard conditions of vapor expelled from the cargo tanks of the chemical tankers were investigated. The purposes of this research are to provide data on the exposure concentration to the marine harmful volatile cargo such as benzene, toluene and xylene, and to find out the effective countermeasures to reduce the health risks caused from that exposure. To achieve these purposes, the onboard measurements on the working environment and the personal exposure concentration of the chemical vapors emitted from the cargo tanks were carried out. The concentration measurements for typical size of 500 tons and 1000 tons cargoes in Japan were conducted during the routine chemical tanker operations composed of loading, unloading, transit and tank cleaning throughout all seasons of the year. The vapor concentration of the emission sources was also measured. The vapor samples were collected in the vapor sample canisters, bottles or bags and VOC (Volatile Organic Compound) gas monitors, and the samples were subsequently analyzed by the gas chromatography. Meanwhile, to make clear the mechanism of diffusion and vaporization in the cargo tanks, a method to estimate the vapor emissions during the loading and the cleaning operations were developed using the 1/10 scale model of a cargo tank. Furthermore, the risk assessment of crews exposed to chemicals was conducted to clarify the effectiveness of several countermeasures. The followings are found.: 1) The effectiveness of the methods employed in this study for measuring the working environment and the personal exposure concentration is confirmed. 2) The data of environment concentrations of the benzene vapor at some onboard points showed that the benzene concentrations vary with the operations. The higher concentration occurs during the tank cleaning operation and in the pump room. 3) The personal exposure levels of the crews to volatile chemicals such as benzene, toluene and xylene vary with the person. 4) The calculation models to estimate the concentrations of the emitted vapor from the vent post during the loading operation and the tank cleaning operation are proposed. The comparison between the experimental data and that of the calculation shows good agreements. 5) The methods to reduce the vapor emissions and to mitigate the exposure levels of crews are investigated and the effectiveness of the methods is assessed quantitatively. 6) The risk of health for crews due to the exposures during marine vessel transfer operations varies with the exposure level, the exposure time, the frequency to engage in the operation and the hazardousness of the cargo.
独立行政法人海上技術安全研究所の論文
2002-01-26

ベンゼン等有害揮発性物質の船舶からの排出量低減に関する研究

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