Cancer risk estimation for mixtures of coal tars and benzo(a)pyrene.

Two-year chronic bioassays were conducted by using B6C3F1 female mice fed several concentrations of two different mixtures of coal tars from manufactured gas waste sites or benzo(a)pyrene (BaP). The purpose of the study was to obtain estimates of cancer potency of coal tar mixtures, by using conventional regulatory methods, for use in manufactured gas waste site remediation. A secondary purpose was to investigate the validity of using the concentration of a single potent carcinogen, in this case benzo(a)pyrene, to estimate the relative risk for a coal tar mixture. The study has shown that BaP dominates the cancer risk when its concentration is greater than 6,300 ppm in the coal tar mixture. In this case the most sensitive tissue site is the forestomach. Using low-dose linear extrapolation, the lifetime cancer risk for humans is estimated to be: Risk < 1.03 x 10(-4) (ppm coal tar in total diet) + 240 x 10(-4) (ppm BaP in total diet), based on forestomach tumors. If the BaP concentration in the coal tar mixture is less than 6,300 ppm, the more likely case, then lung tumors provide the largest estimated upper limit of risk, Risk < 2.55 x 10(-4) (ppm coal tar in total diet), with no contribution of BaP to lung tumors. The upper limit of the cancer potency (slope factor) for lifetime oral exposure to benzo(a)pyrene is 1.2 x 10(-3) per microgram per kg body weight per day from this Good Laboratory Practice (GLP) study compared with the current value of 7.3 x 10(-3) per microgram per kg body weight per day listed in the U.S. EPA Integrated Risk Information System.     

Improving Cancer Dose–Response Characterization by Using Physiologically Based Pharmacokinetic Modeling: An Analysis of Pooled Data for Acrylonitrile-Induced Brain Tumors to Assess Cancer Potency in the Rat

Historically, U.S. regulators have derived cancer slope factors by using applied dose and tumor response data from a single key bioassay or by averaging the cancer slope factors of several key bioassays. Recent changes in U.S. Environmental Protection Agency (EPA) guidelines for cancer risk assessment have acknowledged the value of better use of mechanistic data and better dose–response characterization. However, agency guidelines may benefit from additional considerations presented in this paper. An exploratory study was conducted by using rat brain tumor data for acrylonitrile (AN) to investigate the use of physiologically based pharmacokinetic (PBPK) modeling along with pooling of dose–response data across routes of exposure as a means for improving carcinogen risk assessment methods. In this study, two contrasting assessments were conducted for AN-induced brain tumors in the rat on the basis of (1) the EPA's approach, the dose–response relationship was characterized by using administered dose/concentration for each of the key studies assessed individually; and (2) an analysis of the pooled data, the dose–response relationship was characterized by using PBPK-derived internal dose measures for a combined database of ten bioassays. The cancer potencies predicted for AN by the contrasting assessments are remarkably different (i.e., risk-specific doses differ by as much as two to four orders of magnitude), with the pooled data assessments yielding lower values. This result suggests that current carcinogen risk assessment practices overestimate AN cancer potency. This methodology should be equally applicable to other data-rich chemicals in identifying (1) a useful dose measure, (2) an appropriate dose–response model, (3) an acceptable point of departure, and (4) an appropriate method of extrapolation from the range of observation to the range of prediction when a chemical's mode of action remains uncertain.     

The Net Resource Distribution of Two Parent Low Income Families: A Regional Comparison*†

The purpose of this paper is firstly to investigate the distribution of two parent low income families in England and Wales and Scotland for see to what extent they differ, and secondly to examine the relative importance of certain contributing factors in determining the distributions. From an analysis of Family Expenditure Survey data it is found that although it is difficult to arrive at statistically verifiable conclusions about the nature of the distributions, interesting qualitative observations can be made.     

他们不再是孩子了——关于“新失业群体”现状的社会学报告

近些年来在关于下岗失业问题的研究中形成的一个思维定势是,人们所说的失业下岗往往针对的仅是国有企业的失业下岗人员,至多将原来集体企业的失业下岗人员包括在内。但事实上,在我们的社会中,还存在另外一个数目庞大的失业群体,这个群体至今很少受到人们的关注,他们就是在本文中我们称之为“新失业群体”的这么一批人。对于他们,我们既缺少一个经验层面上的全面描述,更没有在政策层面上对他们进行充分的讨论,至于理论层面的梳理,就更是凤毛麟角了。本研究试图为改变这一现状做一个初步的尝试,不过,首先,我们必须阐明我们所使用的概念及意义…     

Does Privatization Protect Natural Resources? Property Rights and Forests in Guatemala

Objectives . Property rights are central to debates about natural resource policy. Governments traditionally have been seen as the appropriate custodians of natural resources for their citizens. More recently, many argue the privatization of property rights will ensure that users have incentives to manage their resources well. Common property, to the extent it is discussed at all, is seen as leading to the tragedy of the commons. We evaluate these claims by assessing property rights and forest conditions in two private and three communal forests in Guatemala. Methods . Data on biological and social phenomena from five forests (151 plots) and their associated communities were collected using the International Forestry Resources and Institutions Research Program protocols. Ordinary least squares regression was used to analyze four models. We examined t -scores for differences in coefficients for the different models. Results . The models demonstrate that de jure property rights are not a powerful predictor of variations among the sampled forests. Conclusions . We argue that de facto institutions and their enforcement are much more important than de jure property rights to forest management. Communities holding a forest in common can, under certain circumstances, create institutions to manage their resources as successfully as—or more successfully than—private owners.     

Branded: The Economic Geographies of Streets Named in Honor of Reverend Dr. Martin Luther King,Jr.*

Objectives. We investigate the economic geographies of streets named for Reverend Dr. Martin Luther King, Jr. (MLK Streets), which are an increasingly common means by which various community members across the United States are attempting to commemorate the slain civil rights leader. It is our intent to characterize these negatively “branded” spaces in order to challenge some of the common perceptions about them and inform current and future MLK Street naming debates. Methods. We statistically analyze nonresidential establishments located on streets named for King in terms of scale (as measured by annual sales and employment) and industrial classification. To our knowledge, this is the first such analysis conducted at the national level. Results. Establishments located on MLK Streets do not systematically exhibit economic marginality. Establishments located on these streets do systematically exhibit unique local functions and industrial composition. Conclusion. In the absence of empirically‐driven research, the negative stereotypes that surround MLK Streets have gone unchallenged and are proliferating. The research reported here calls into question a number of these stereotypes and should inform the public, city councils, and other local policymakers, who are increasingly being faced with contentious MLK Street naming debates.     

The Proportion of Gaming Revenue Derived from Problem Gamblers: Examining the Issues in a Canadian Context

The legitimacy of government-sponsored gambling and its continued expansion depends in part on the impact that gambling has on society and the extent to which gambling revenue is derived from vulnerable individuals. The purpose of the present article is to try to establish a valid estimate of the proportion of gaming revenue derived from problem gamblers in Canada. Using recent secondary data collected in eight Canadian provinces, we estimate this proportion to be 23.1%, compared to a problem gambling prevalence rate of 4.2%. This estimate must be seen as tentative, however, as self-reported expenditures are 2.1 times higher than actual provincial gaming revenues.