Comparative Potency Method for Cancer Risk Assessment: Application to Diesel Particulate Emissions1

An estimation of the human lung cancer “unit risk” from diesel engine particulate emissions has been made using a comparative potency approach. This approach involves evaluating the tumorigenic and mutagenic potencies of the particulates from four diesel and one gasoline engine in relation to other combustion and pyrolysis products (coke oven, roofing tar, and cigarette smoke) that cause lung cancer in humans. The unit cancer risk is predicated on the linear nonthreshold extrapolation model and is the individual lifetime excess lung cancer risk from continuous exposure to 1 μg carcinogen per m³ inhaled air. The human lung cancer unit risks obtained from the epidemiologic data for coke oven workers, roofing tar applicators, and cigarette smokers were, respectively, 9.3 × 10^?4, 3.6 × 10^?4, and 2.2 × 10^?6 per μg particulate organics per m³ air. The comparative potencies of these three materials and the diesel and gasoline engine exhaust particulates (as organic extracts) were evaluated by in vivo tumorigenicity bioassays involving skin initiation and skin carcinogenicity in SENCAR mice and by the in vitro bioassays that proved suitable for this analysis: Ames Salmonella microsome bioassay, L5178Y mouse lymphoma cell mutagenesis bioassay, and sister chromatid exchange bioassay in Chinese hamster ovary cells. The relative potencies of the coke oven, roofing tar, and cigarette smoke emissions, as determined by the mouse skin initiation assay, were within a factor of 2 of those determined using the epidemiologic data. The relative potencies, from the in vitro bioassays as compared to the human data, were similar for coke oven and roofing tar, but for the cigarette smoke condensate the in vitro tests predicted a higher relative potency. The mouse skin initiation bioassay was used to determine the unit lung cancer risk for the most potent of the diesel emissions. Based on comparisons with coke oven, roofing tar, and cigarette smoke, the unit cancer risk averaged 4.4 × 10^?4. The unit lung cancer risks for the other, less potent motor-vehicle emissions were determined from their comparative potencies relative to the most potent diesel using three in vitro bioassays. There was a high correlation between the in vitro and in vivo bioassays in their responses to the engine exhaust particulate extracts. The unit lung cancer risk per μg particulates per m³ for the automotive diesel and gasoline exhaust particulates ranged from 0.20 × 10^?4 to 0.60 × 10^?4; that for the heavy-duty diesel engine was 0.02 × 10^?4. These unit risks provide the basis for a future assessment of human lung cancer risks when combined with human population exposure to automotive emissions.     

Controlling health care costs: An evaluation of strategies

There has been much discussion about the factors underlying inflation in the health care sector and the means to moderate increases in health expenditures. This paper identifies various costcontainment strategies and synthesizes research findings that may be helpful in evaluating their effectiveness. The review demonstrates the complexity of the issues and relationships that must be confronted and understood in cost containment. The delivery system is shown to be not well-suited to improving efficiency and restraining health care expenditure. Any single strategy, whether it involves restructuring the market or more direct regulation, cannot in itself accomplish the combination of expenditure control and adequacy of services that is socially desirable. A number of mutually reinforcing strategies are required. Finally, more empirical and analytical information on incentives, provider and regulatory decisionmaking, costs of regulation, and the dynamics of negotiation, is essential for the design of an effective costcontainment program.     

An assessment of the quality of developmental day center playgrounds for exceptional children

This study assessed the playgrounds of developmental day care centers and compared them with playgrounds of regular certified day care centers. Twenty playgrounds, randomly selected from the listing of developmental day centers, were compared with a matched sample of 20 playgrounds from certified day care centers in one state. A revision of Frost's Playground Rating System (1978b) was employed to rate the two groups of playgrounds on content, safety, and function. Data were analyzed using an analysis of variance technique. The quality of developmental day center playgrounds for exceptional children was inferior to that of regular day care center playgrounds in terms of playground content. No significant differences were noted on safety or function.     

Gender and racial/ethnic differences in predicting adolescent sexual risk: athletic participation versus exercise

Though often conflated, informal physical exercise and organized athletic participation have very different implications for adolescent sexual risk outcomes. The purpose of this research is to disaggregate strenuous exercise from sports, examine how each is associated with sexual risk, and explain the observed differences using the conceptual lens of cultural resource theory. Using a nationally representative sample of over 16,000 public and private high school students, we employ logistic regression to test hypotheses about the gender-specific and race-specific effects of strenuous exercise and athletic participation on adolescent sexual risk behavior. The results show that both forms of physical activity buffer sexual risk for girls. Strenuous exercise is associated with increased odds of sexual risk for boys. Sports and race interact to influence boys' sexual risk outcomes: Athletic participation is associated with lowered odds of sexual risk for white male adolescents, but heightened odds of sexual risk for black male adolescents.     

Trajectories of gender role orientations in adolescence and early adulthood: a prospective study of the mental health effects of masculinity and femininity

Adolescence is the segment of the life course when gender differences in mental health emerge and gender becomes a more salient factor shaping orientations toward oneself and views of one's place in the social world. This study uses mixture modeling, to identify trajectories of masculinity and femininity between ages 12 and 25, and OLS regression, to examine the effects of those trajectories on mental health in young adulthood (measured as depressive symptoms and alcohol problems at age 25). Four waves of prospective data from the Rutgers Health and Human Development Project are used; respondents (n = 447) are age 12 at Wave 1 (1979-81), 15 at Wave 2 (1982-84), 18 at Wave 3 (1985-87), and 25 at Wave 4 (1992-94). Results indicate that having relatively high and increasing levels of masculinity over adolescence decreases depressive symptoms in early adulthood for both males and females. Reflecting the privileging of males over females, the findings suggest that masculinity, but not femininity, is a central axis on which advantages and disadvantages across some dimensions of mental health accumulate over adolescence.     

Effective targeted and community HIV/STD prevention programs

Community interventions and interventions targeting specific groups at risk of STDs/HIV have demonstrated significant impacts on sexual behavior, particularly condom use and safer sex. The scientific evidence suggests the factors that make these interventions particularly effective include the establishment of community, including business and CBO partnerships; maintainance of the intervention post-research funding; and buy-in by the community or target group. The modification of risky normative beliefs through the use of opinion leaders and role models, and through intervention delivery by peer educators, is an important facet of such interventions. Interventions delivered by health professionals, absent a community base, appear to be unsuccessful. Where cultures or subcultures are targeted, the close involvement of such groups in the design and delivery of messages is critical to their success. Diffusion of interventions through existing social networks further extends the intervention into the community and acts to reinforce and maintain changes in peer norms toward safer sexual behavior. The available data confirm that community or medical infrastructure-based interventions are effective in changing sexual behavior and can reach a wider range of the population than face-to-face programs if they incorporate peer educators as role models in modifying norms, and if diffusion of the intervention is integral to the design.