Metal Interactions in carcinogenesis†

Mixed exposures to a number of metallic compounds may give rise to a carcinogenic response in humans.

An interaction between occupational exposure to arsenic and cigarette smoking has been documented epidemiologically. A multiplicative effect was indicated concerning the occurrence of lung cancer when both of the exposures were present. Several experimental studies have been reported in the literature concerning interactions between benzo(a)pyrene and Fe₂O₃ as well as some other metallic compounds like Ni₃S₂, PbO, MgO and TiO₂ in relation to respiratory carcinogenicity. There is also limited evidence of a positive interaction between arsenic trioxide and benzo(a)pyrene. Particles containing V and Ni were obtained from the flue gases of power plants burning heavy fuel oil. Such particles were not carcinogenic themselves but enhanced the carcinogenicity of benzo(a)pyrene even more efficiently than Fe₂O₃.

Increased dietary selenium intakes can decrease the carcinogenicity of several organic carcinogens in animals and dietary zinc can effectuate both enhancement and inhibition of carcinogenicity depending on dietary concentration.     

利用多时相陆地卫星TM数据监测山区干燥石南植被在区域尺度上的变化

植被覆盖变化分析需要选择一组合适的变量来测量和描述其变化.卫星传感器,如美国陆地卫星TM,具有提供大范围植被覆盖信息的优势,使对陆地表面过程的监测变得便利.本文讨论利用卫星数据对瑞典耶姆特兰(Jamtland)县山区干燥石南群落进行变化检测.本研究分别用到了1984年、1994年陆地卫星5的TM数据和2000年陆地卫星7的ETM+数据.在对图像进行辐射归一化、几何纠正和地形纠正处理之后,我们比较了不同的变化检测方法.对"变化"和"无变化"两种变化类型的检测,NDⅥ图像差值方法的精度最高,总体精度达到94%(k=0.87).NDVI回归分析方法可以提取更多的变化信息,可以检测到山区干燥石南群落中3种类别的植被变化.通过应用模糊集阈值技术,变化检测的总体精度从65%(k=0.45)提高到74%(k=0.59).这些方法产生的变化结果可以显示脆弱的山区石南群落中植被变化区域的位置,并反映出不同的植被变化程度(植被覆盖减少程度:高、中和无).1984～2000年间,该研究区域内共有17%的干燥和极端干燥石南植被发生了变化.平均起来,4%的被研究石南群落发生了较大程度的变化,也就是说,在该期间这些石南植被经历了"较大程度的植被覆盖减少".研究结果显示:①"大幅度的植被减少"的区域中,研究区南部低的高山带(1ow alpine zone)植被覆盖减少程度最大;②主要的变化发生在1994～2000年期间.     

环境监测策略评价

在环境监测中,监测系统在非预期事件出现时能够发出早期预警是很重要的.这些事件具有突发,或者难以观测到的性质.在设计这类监测系统时,必须在成本和风险之间达到一个适当的平衡.传统意义上有两类和早期预警系统相关联的风险,即没有检测到重要变化的风险和错误预警的风险.本文的目的是阐述一种在考虑了传统类型的风险和成本的情况下来比较不同监测系统性能的方法.这个方法被试用于地衣植被的监测中,并采用预期效应作为性能的度量标准.在估计事件的概率时,应用了空间微观模拟技术(spatial microsimulation)和蒙特卡罗模拟技术.所评估的监测计划基于卫星图像、航空照片、野外采样和土地覆被图.研究的主要结论是,标准化质量度量在环境监测方法可用性的评估中是极为有用的.另外,空间微观模拟技术在效益和成本估计中是可用的.不过要改进算法,还需要应用宏观约束(macroconstraints)来修正模拟模型.     

Monitoring change in mountainous dry-heath vegetation at a regional scale using multitemporal Landsat TM data

Vegetation cover-change analysis requires selection of an appropriate set of variables for measuring and characterizing change. Satellite sensors like Landsat TM offer the advantages of wide spatial coverage while providing land-cover information. This facilitates the monitoring of surface processes. This study discusses change detection in mountainous dry-heath communities in J?mtland County, Sweden, using satellite data. Landsat-5 TM and Landsat-7 ETM+ data from 1984, 1994 and 2000, respectively, were used. Different change detection methods were compared after the images had been radiometrically normalized, georeferenced and corrected for topographic effects. For detection of the classes change--no change the NDVI image differencing method was the most accurate with an overall accuracy of 94% (K = 0.87). Additional change information was extracted from an alternative method called NDVI regression analysis and vegetation change in 3 categories within mountainous dry-heath communities were detected. By applying a fuzzy set thresholding technique the overall accuracy was improved from of 65% (K = 0.45) to 74% (K = 0.59). The methods used generate a change product showing the location of changed areas in sensitive mountainous heath communities, and it also indicates the extent of the change (high, moderate and unchanged vegetation cover decrease). A total of 17% of the dry and extremely dry-heath vegetation within the study area has changed between 1984 and 2000. On average 4% of the studied heath communities have been classified as high change, i.e. have experienced "high vegetation cover decrease" during the period. The results show that the low alpine zone of the southern part of the study area shows the highest amount of "high vegetation cover decrease". The results also show that the main change occurred between 1994 and 2000.     

Low bone density and renal dysfunction following environmental cadmium exposure in China

This paper presents the main findings of a study on health effects of environmental cadmium pollution in China, performed in 1998, i.e. approximately 25 years after the first warnings of such effects were published in Ambio. Forearm bone mineral density (BMD) and renal dysfunction were assessed in population groups exposed to cadmium via rice. Decreased BMD was found in postmenopausal women with elevated urinary cadmium (CdU) or cadmium in blood (CdB) and among men with elevated CdB. Also, clear and statistically significant dose-effect and dose-response relationships were found between CdB or CdU and renal dysfunction (increased excretion of retinol-binding protein). This is the first report of bone effects among Cd-exposed population groups in Asia outside Japan. The report is also of interest since it demonstrates that bone effects, a comparatively severe adverse health effect of Cd, in combination with renal dysfunction, still occurs in environmentally exposed population groups in Asia. Recent reports on bone effects in Cd-exposed population groups in Europe are discussed.     

Evaluation of environmental monitoring strategies

In environmental monitoring, it is important that the monitoring system should emit early warnings when undesired events occur. These events may be sudden or of a more subtle nature. In the design of such monitoring systems, a proper balance between cost and risk must be achieved. There are 2 classic types of risk connected with early warning systems, namely the risk of not detecting significant changes and the risk of false alarms. The purpose of this paper is to describe a method for comparing the performance of different monitoring systems, considering the classic types of risk and cost. The method is applied to the monitoring of the lichen cover as a test case. The expected utility has been used as a measure of performance. When estimating the probabilities of the events, spatial microsimulation and Monte-Carlo simulation techniques have been used. The monitoring programs studied are based on satellite images, aerial photos, field samples, and land-cover maps. The major conclusions of this study are that standardized quality measures are extremely useful for evaluating the usability of environmental monitoring methods. In addition, when estimating gains and costs, spatial microsimulation techniques are useful. To improve the method, however, macroconstraints should also be used for aligning the simulation model.