蒙古國烏蘭巴托學童重金屬暴露之研究

Abstract

背景：蒙古國首都烏蘭巴托是蒙古國最都市化的城市，在烏蘭巴托市區有許多的 居民居住在傳統的蒙古式建築-蒙古包並聚集形成蒙古包居住區，先前的研 究表示蒙古包和三座火力發電廠使用煤炭和木材燃燒所排放的汙染物質造 成空氣汙染以及在烏蘭巴托採樣PM10 中重金屬濃度有明顯的增加。然而尚 未有在烏蘭巴托進行空氣污染物對人體暴露之研究。因此本研究目的為評 估烏蘭巴托學童重金屬暴露以及辨識潛在的暴露來源。 方法：本研究於烏蘭巴托首都選擇六間學校，以11 至15 歲的320 名學童為研究 對象，並於非燃燒取暖季節(2011 年九月)以及燃燒取暖季節(2011 年12 月和2012 年3 月)進行三次尿液及問卷採樣，收集學童基本資料以及可能和 重金屬暴露有關的因子，並利用感應耦合電漿質譜儀ICP-MS 分析尿中重金 屬濃度(釩、鉻、錳、鎳、銅、砷、鍶、鎘、汞、鉈、鉛)，並以廣義估計式 (Generalized Estimating Equations, GEE)模式校正個人基本資料以及環境因 子來評估季節影響蒙古學童尿中重金屬之濃度情形。 結果：以廣義估計式GEE 模式分析，在控制年齡、性別、季節、居住區、抽菸、 有無使用蚊香或殺蟲劑等干擾因子之後，發現居住於蒙古包的學童，其尿 中鎘和鉛濃度顯著高於居住公寓者1.52 和1.46 倍以及居住於磚造屋的學童 尿中釩及鉻濃度顯著高於居住公寓者1.14 和1.15 倍。居住於蒙古包居住區 的學童尿中鎘及鉛濃度顯著高於居住在非蒙古包居住區1.24 和1.23 倍。另 外，模式結果也發現學童尿中銅、砷在燃燒取暖季節的濃度經校正干擾因 子後顯著高於非燃燒取暖季節1.10 和1.20 倍。而學童尿中鎳及鎘濃度在燃 燒取暖季節的濃度顯著低於非燃燒取暖季節0.75 和0.76 倍。 結論：顯示蒙古學童尿中鎘及鉛濃度於蒙古包居住區以及居住在蒙古包皆有顯著 增加，而蒙古學童暴露重金屬的來源無法僅由空氣汙染單一途徑來解釋。

Background：Ulaanbaatar, the capital city of Mongolia, is the most urbanized city of the country. Many people live in gers, the traditional Mongolian dwellings, in crowded areas called ger areas, in Ulaanbaatar. Previous studies have shown that air quality was polluted by emissions from coals and woods used in gers and three coal-fired power plants and the concentrations of heavy metals in PM10 were elevated in Ulaanbaatar. However, no study on human exposure to air pollutants has been reported in Ulaanbaatar yet. The purpose of this study is to evaluate children’s exposure to heavy metals and identify potential sources of such exposures in Ulaanbaatar. Methods：Our study subjects were 320 students aged from 11 to 15 years old in 6 schools in Ulaanbaatar. Spot urine samples and questionnaires were collected three times for each subject in the non-heating season (September in 2011) and heating season (December in 2011and March in 2012). Personal information and potential heavy metals exposure-related factors were collected by questionnaire. The levels of urinary heavy metals, including vanadium, chromium, manganese, nickel, copper, arsenic, strontium, cadmium, mercury, thallium and lead, were analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). Generalized Estimating Equation (GEE) modes were applied to estimate seasonal effects on urinary heavy metals levels, adjusting for demographic and environmental factors. Results：According to GEE models, we found that the urinary levels of cadmium and lead of the children who live in gers were respectively 1.52 and 1.46 times higher than those of the children living in apartments, after adjusting for age, gender, season, area, smoking and insecticide use. Urinary levels of vanadium and chromium of the children who live in brick houses were respectively 1.14 and 1.15 times higher than those of the children living in apartments. Urine cadmium and lead levels for children living in ger areas were 1.24 and 1.23 times higher than those living in non-ger areas. In addition, we found that urinary levels of copper and arsenic of the children in the heating season were respectively 1.10 and 1.20 times higher than in the non-heating season after adjusting for other exposure-related factors. By contrast, urinary levels of nickel and cadmium of the children in the heating season were respectively 0.75 and 0.76 times lower than in the non-heating season. Conclusions：Mongolian children’s urinary cadmium and lead levels were significantly increased for those living in ger areas or in gers in Ulaanbaatar. Air pollution was not the only source of Mongolian children’s exposures to heavy metals.