報告書番号

U92007

タイトル（和文）

ゴールデンハムスターによる石炭灰の低濃度長期暴露影響評価

タイトル（英文）

EFFECTS OF LONG-TERM AND LOW-DASE EXPOSURE TO COAL FLY ASH ON RESPORATORY ORGANS OF GOLDEN HAMSTER

概要 （図表や脚注は「報告書全文」に掲載しております）

高濃度の石炭灰を吸入した実験動物の肺では，石炭灰を貪食した肺胞マクロファージ（ＡＭ）が肺胞内に集積し，この部位では組織学的変化が起こる。このため，本研究は低濃度の長期間暴露によってＡＭが集積し始める濃度を解明するとともに，呼吸器の病理組織学的変化を明らかにする目的で行った。ゴールデンハムスターに０．１，０．２，０．４立方ｍの濃度で１８ヶ月の連続暴露を行った結果，０．４ｍｇ／立方ｍ暴露群では暴露６ヶ月目から，０．２ｍｇ立方ｍ暴露群では暴露１２ヶ月目からＡＭの集積が形成されたが，０．１ｍｇ立方ｍ暴露群では形成されなかった。以上の結果から，集積が形成される閾値は０．２ｍｇ立方ｍと０．１ｍｇ立方ｍの間に存在することが明らかとなった。肺上皮細胞の組織学的変化はどの実験群でも非特異的であり，０．１ｍｇ立方ｍ暴露群ではほとんど認められなかった。また，どの暴露群にも呼吸器系組織以外の

概要 （英文）

FOUR GROUPS OF MALE GOLDEN HAMSTERS WERE EXPOSED TO 0 (FILTERED-AIR ONLY),0.1,0.2 AND 0.4 MG/CUBE M OF COAL FLY ASH(FA) PARTICLES FOR 18 MONTHS (20 H/DAY,7 DAYS/WEEK) TO INVESTIGATE THETHRESHOLD CONCENTRATION OF CLUSTER FORMATION OF PARTICLE-LADEN ALVEOLAR MACROPHAGES (AM). ANIMALS WERE SACRIFICED EVERY THREE MONTHS AND RESPIRATORY ORGANS INCLUDING LUNG-ASSOCIATED LYMPH NODES WERE OBSERVED MORPHOLOGICALLY. GROSS AND LIGHT MICROSCOPIC OBSERVATIONS SHOWED THAT BLACKPIGMENTS (ACCUMULATIONS OF PARTICLE-LADEN AM)IN THE LUNG PARENCHYMA OF0.4 MG/CUBE M EXPOSED ANIMALS APPEARED AT 6 MONTHS OF EXPOSURE AND THENUMBER INCREASED WITH EXPOSURE TIME. IN 0.2 MG/CUBE M-EXPOSED ANIMALS,SMALL AM CLUSTERS APPEARED AT 12 MONTHS OF EXPOSURE. THE NUMBER INCREASED UNTIL 15 MONTHS OF EXPOSURE,BUT SUBSEQUENT INCREASE DID NOT OCCUR. ON THE OTHER HAND,0.1 MG/CUBE M-EXPOSED ANIMALS DID NOT SHOW ANY AM CLUSTERS AT 18 MONTHS OF EXPOSURE. THESE RESULTS SUGGEST THAT THE THRESHOLDCONCENTRATION FOR CLUSTER FORMATION OF PARTICLE-LADEN AMS IS BETWEEN 0.1 MG/CUBE M AND 0.2 MG/CUBE M IN THIS EXPERIMENT. SLIGHT HYPERTROPHY AND HYPERPLASIA OF TYPE-2 EPITHELIAL CELLS WERE OBSERVED IN THE ALVEOLARREGION SURROUNDING THE ACCUMULATIONS OF PHAGOCYTES IN 0.2 AND 0.4 MG/CUBE M-EXPOSED ANIMALS. HOWEVER,SUCH HISTOLOGICAL CHANGES OF THE LUNG EPITHELIAL CELLS WERE NON-SPECIFIC. IN MEDIASTINAL LYMPH NODES (MLN),VERYSMALL AMOUNTS OF FA WERE DEPOSITED IN MACROPHAGES IN THE MEDULLA AT 6 MONTHS OF EXPOSURE IN THE 0.4 MG/CUBE M-EXPOSED GROUP,AND FA DEPOSITIONINCREASED SLIGHTLY WITH EXPOSURE TIME. IN THE 0.2 AND 0.1 MG/CUBE M-EXPOSED GROUPS,FA APPEARED IN MLN AT 9 MONTHS AND 12 MONTHS,RESPECTIVELY.HOWEVER,PARTICLE-LADEN MACROPHAGES DID NOT BECOME CLUSTERS AND HISTO-PATHOLOGICAL CHANGES WERE NOT OBSERVED. FA PARTICLES AND HISTOPATHOLOGICAL CHANGES IN OTHER ORGANS WERE NOT OBSERVED IN ANY EXPOSURE GROUP DURING THE EXPOSURE PERIOD. THESE RESULTS SUGGEST THAT INHALED FA PARTICLESUNDER CURRENT AIRQUALITY REGULAT

報告者

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