報告書番号

V01

タイトル（和文）

石炭燃焼に伴う微量物質の挙動と健康リスク評価

タイトル（英文）

Behavior and health risk assessment of trace elements from coal combustion

概要 （図表や脚注は「報告書全文」に掲載しております）

石炭火力発電所から排出される水銀等微量物質を対象に、石炭燃焼プロセスおよび環境中における挙動を解明するとともに健康リスク評価手法を開発した。(1)水銀、セレン、ホウ素の石炭からの放出特性および排ガス温度低下に伴うガスから粒子への移行特性、排煙処理装置における水銀の酸化機構や除去機構を解明した。さらに、石炭火力発電所における微量物質の大気への排出実態を明らかにした。(2)微量物質沈着量の実態調査結果から、湿性沈着量は国外の発生源の影響、乾性沈着量は工場排出ばいじんの影響を強く受けていることが示唆された。また、東京湾内の水銀は、降雨増水時に河川に流入した土壌が主な負荷源と推察された。内湾、河川、湖沼における魚類の水銀濃度には、採取地点間の差異が認められなかった。(3)微量物質の吸入暴露評価手法の開発を行い、全国の石炭火力発電所を対象に吸入リスクを計算した結果、微量物質の発がんリスクは国の目標値を大きく下回った。水銀の経口暴露評価手法の開発を行い、仮想の石炭火力発電所を対象に関東地域をモデルケースとして試算した結果、水銀の経口暴露量はわが国の耐容摂取量に比べてきわめて小さいと推定された。

概要 （英文）

The behavior of trace elements in coal combustion and the environment were clarified, and assessment methods for the health risks of trace elements from a coal-fired power plant were developed. By conducting pulverized coal combustion tests, the release characteristics of mercury, selenium and boron from coal and the changes in the gas-to-particulates ratios of three elements with decreasing temperature were clarified. Moreover, the oxidation and removal mechanism of mercury in flue gas treatment systems were elucidated. The emission factors of trace elements were calculated from the monitoring data of coal-fired power plants in Japan. The measured wet and dry depositions of trace elements over Japan were recognized to be influenced by global circulation, regional transport and local anthropogenic emission sources. An analysis of the mass balance of trace elements in Tokyo Bay showed that the major sources of mercury in the bay were mainly soil discharged into storm water. The mercury concentrations measured in fish from a semiclosed bay, rivers and lakes showed no relationships with the sampling points. An inhalation exposure assessment method for trace elements from a coal-fired power plant was developed, and its use indicated that inhalation cancer risks from power plants in Japan are well below national guidelines or reference levels. A multimedia exposure assessment method for mercury from a point source was developed. A model calculation of mercury emissions from a hypothetical coal-fired power plant in the Kanto region showed an oral exposure level much lower than the national tolerable weekly intake.

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