Half-lives of tetra-, penta-, hexa-, hepta-, and octachlorodibenzo-p-dioxin in rats,monkeys, and humans--a critical review

The elimination half-lives (t1/2) in Sprague-Dawley rats for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2, 3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD) were estimated in long-term studies by Schlatter, Poiger and others. Furthermore, there are some published half-lives of TCDD in adult humans. The average half-life of TCDD in adult humans is approximately 2840 days, while in Sprague-Dawley rats the average t1/2 of TCDD is 19 days. The t1/2 of TCDD in humans is about 150 times that of rats. This factor was used to calculate the t1/2 values of the other polychlorinated dibenzo-p-dioxins (PCDDs) in humans from the rat data. Furthermore, the terminal t1/2 values of PCDDs in adult humans were calculated from the regression equation: logt1/2H = 1.34 logt1/2R + 1.25 which was recently established for 50 xenobiotics (t1/2H = terminal half-lives in days for humans, t1/2R = terminal half-lives in days for rats). The following terminal half-lives in adult humans were obtained: 12.6 years for 1,2,3,7,8-PeCDD, 26-45 years for 1,2,3,4,7,8-HxCDD, 80-102 years for 1,2,3,4,6,7,8-HpCDD and ca. 112-132 years for OCDD. These half-lives of PCDDs are critically compared with measured t1/2 values of PCDDs and other persistent organic pollutants in rats, monkeys and humans.     

Pro-Poor local economic development in South Africa: The role of pro-poor tourism

This paper describes features of the emerging nexus in South Africa between tourism, poverty alleviation and local economic development (LED) interventions. The South African experience of evolving a strong pro-poor focus in LED planning is distinctive in the international context of writings on LED. Pro-poor LED is increasingly the outcome of the application of measures and programmes that are linked to the approach of pro-poor tourism in both rural and urban areas of South Africa. Two studies are presented of Alexandra township, Johannesburg and the Madikwe Game Reserve in North West Province as examples of pro-poor tourism as a form of pro-poor LED. It is argued that the growth of pro-poor tourism initiatives in South Africa suggests that the country is currently a laboratory for the testing and evolution of new approaches towards the planning of LED that potentially will have relevance for other countries in the developing world.     

Effects of new technologies with special regard for the implementation process per se

The aim of this study was to investigate the effects of the implementation process to new technologies [e.g. drawing board/computer-aided design (CAD), microfiche/electronic data processing] on the employees concerned. Since the emphasis of the study lay in the intrinsic relationship of the implementation process with stress reactions, the parameters were measured at the place of work in a longitudinal design. Employees (n = 279) in seven companies (work fields: CAD, clerical work, telephone information desk) were tested three times — two months prior to, during, and 12 months after implementation. Aspects of strain and satisfaction were taken into account at each measurement phase. A special test-instrument was designed to describe the ’style of implementation‘ (manner in which implementation took place) particular to each company. The level of strain was found to increase during the implementation process. The amount of this increase was found to correlate with the company's style of implementation as well as with the type of the individual's work activity. The highest levels were found among those employees little included in the implementation process and those whose work is described as monotonous.     

可持续是每个人的职责

在发达和发展中国家找到改善生活水平及预期增长的一个可持续发展道路的压力正在增加.达到可持续需要有关生产和清楚行为的根本改变.发现使用低能耗和原材料(产生较少的废弃物)提供较好能力的方法能够有助于世界范围生活水平的改善.特别是在过去十年中,许多企业家对于可持续采取了更加负责的态度,例如在经济效益、与利益相关者的社会对话和共同的社会责任领域.公司正在认识到他们必须与广大的合作伙伴和利益相关者合作,在市场中变得更可持续和成功.     

Dibenzo-p-dioxins in the environment from ceramics and pottery produced from ball clay mined in the United States

Processed ball clay samples used in the production of ceramics and samples of the ceramic products were collected and analyzed for the presence and concentration of the 2,3,7,8-Cl substituted polychlorinated dibenzo-p-dioxins and -furans (PCDDs/PCDFs). The processed ball clay had average PCDD concentrations of 3.2 ng/g toxic equivalents, a congener profile, and isomer distribution consistent with those found previously in raw ball clay. The PCDF concentrations were below the average limit of detection (LOD) of 0.5 pg/g. The final fired ceramic products were found to be free of PCDDs/PCDFs at the LODs. A consideration of the conditions involved in the firing process suggests that the PCDDs, if not destroyed, may be released to the atmosphere and could represent an as yet unidentified source of dioxins to the environment. In addition, the PCDDs in clay dust generated during manufacturing operations may represent a potential occupational exposure.     

Community-based natural resources management (CBNRM) in Xinhui, Guangdong Province, China

Using institutional appraisal focused groups (FG) and participatory appraisals with Dillman Total Design Method (TDM), this study examines community interaction with and utilization of wetland resources in Xinhui, Guangdong Province, China. Field results show high commercial activities and corresponding impacts on coastal environment. Other interacting factors identified include: legislation and ecosystem management, stakeholders’ participation, international guidelines criteria, and utilization of mangrove resources in the region. Sensitivity index and community-based natural resources management collaboration comparison percentile showed significant differences between cumulative distributions of respondents (D = 0.2568, P = 0.078). Likert statement of 11 sensitivity optional indexes in EMS of K–S test at 0.05 level of P = 0.078 also show significant differences in interaction between respondent groups and sensitivity factors. This indicates a dysfunction between regional environmental management systems and CBNRM in Xinhui coastal district. Considering the high tourism potential and economic quest of the region, there is the need for coordinated community enlightenment and further studies on the social, ecological and economic value of wetland resources. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.