歲修工人於不同爐種之結晶型游離二氧化矽暴露調查

Survey on Crystalline Free Silica Exposure of Incinerator Maintenance Workers

為了解結晶型游離二氧化矽對勞工之危害，勞工安全衛生研究所曾針對耐火磚廠進行勞工粉塵暴露調查，結果顯示部份原料、成品、堆積物及可呼吸性粉塵中含有不等量之石英；而部份成品中如腊石磚、黏土磚、高鋁質磚含有鱗矽石、方矽石。而耐火磚成品常被使用於煉鋼鐵爐、垃圾焚化爐等工業窯爐，雖然平日作業之勞工可能不會直接暴露於鱗矽石、方矽石中，但修爐工人則可能暴露於此高危害之作業環境中。本計畫為了解修爐工人於不同爐種下結晶型游離二氧化矽之暴露，於爐體進行歲末維修時進行現場勞工可呼吸性粉塵及其結晶型游離二氧化矽之環境測定，以釐清國內是否存在有鱗矽石、方矽石暴露之作業場所。結果顯示，熱風爐、煉焦爐維修作業之可呼吸性粉塵中皆含有不等量之石英、鱗矽石、方矽石，垃圾焚化爐則含有石英。由修爐工人可呼吸性結晶型游離二氧化矽不同晶相之暴露情形得知，國內確實存在有鱗矽石、方矽石暴露之作業環境。且其大多超過我國勞工作業環境空氣中有害物容許濃度規範之標準值，故該作業環境空氣中之粉塵並不宜以厭惡性粉塵視之，否則易低估勞工結晶型游離二氧化矽之暴露。歲修工人於各不同爐種之維修作業時，結晶型游離二氧化矽暴露差異大；其中以熱風爐拆爐作業之危害最大，因其暴露濃度最高，且含有高比率之鱗矽石、方矽石。而以鋼液分裝器非拆爐作業之危害最小，因其可呼吸性粉塵暴露濃度低，且不含有結晶型游離二氧化矽。另為瞭解焚化爐燃燒過程對耐火材料中結晶型游離二氧化矽含量變化之影響，結果發現，燃燒前後之耐火泥及高鋁質磚，其結晶型游離二氧化矽之含量均有明顯的上升。在預防職業矽肺症方面，建議可選用低效率防護之防塵面罩，而考量其舒適性則面體型式可選用可拋式、單一濾片／四分之一面體型式抑或二片濾片／半面體式之防塵面罩。但是進行爐體拆爐作業及清潔爐架之勞工，因該作業別勞工之粉塵及結晶型游離二氧化矽暴露嚴重，大多超過法令容許濃度值，故在防塵防護上應採更嚴謹之防護。

According to an IOSH study on refractory brick factories, quartz, tridymite and cristobalite are found in the feedstocks, products, sediments and respiratory particulate. Some of the products such as pyrophyllite bricks and clay bricks contain tridymite and cristobalite. These bricks are often used to build incinerators. Although daily workers may not be exposed to tridymite and cristobalite, however, those who are responsible for furnace maintenance work maybe exposed to tridymite and cristobalite. In order to understand the exposure of furnace maintenance workers to crystalline free silica under different incinerator environment, this study proceeded with personal sampling of respiratory particulate and crystalline free silica analysis during annual maintenance. The results show unequal amounts of quartz, tridymite and cristobalite in respiratory particulate in sinter furnace and coke oven maintenance. Quartzes are also found in respiratory particulate in maintenance of municipal waste incinerators. Concentrations of these particles mostly exceeded the threshold limit values of the local regulations. Therefore, one can’t consider the inhaled particulate as nuisance dust and underestimate the risk of exposure to crystalline free silica. Annual maintenance workers have different crystalline free silica exposures from different furnaces. In general, sinter furnace has the highest crystalline free silica exposure concentration and high ratio of tridymite and quartz. Different from other furnaces, the tundish has the lowest risk because it has a low respiratory particulate concentration. It also contains no crystalline free silica. This study also examined the influence on the concentration changes of crystalline free silica during incineration. The results showed the concentration of crystalline free silica increased after the incineration of refractory mud and high alumina bricks. To prevent occupational pneumoconiosis, the use of low-efficiency protection masks is recommended. Workers can also use disposable single filter/quarter facial or double filters/half facial dust protection masks. Due to the severe exposure of particulate and crystalline free silica found in this study, demolition and mantel cleaning workers must be more cautious on dust protection.