Issues Related to Time Averaging of Exposure in Modeling Risks Associated with Intermittent Exposures to Lead

Typical exposures to lead often involve a mix of long-term exposures to relatively constant exposure levels (e.g., residential yard soil and indoor dust) and highly intermittent exposures at other locations (e.g., seasonal recreational visits to a park). These types of exposures can be expected to result in blood lead concentrations that vary on a temporal scale with the intermittent exposure pattern. Prediction of short-term (or seasonal) blood lead concentrations arising from highly variable intermittent exposures requires a model that can reliably simulate lead exposures and biokinetics on a temporal scale that matches that of the exposure events of interest. If exposure model averaging times (EMATs) of the model exceed the shortest exposure duration that characterizes the intermittent exposure, uncertainties will be introduced into risk estimates because the exposure concentration used as input to the model must be time averaged to account for the intermittent nature of the exposure. We have used simulation as a means of determining the potential magnitude of these uncertainties. Simulations using models having various EMATs have allowed exploration of the strengths and weaknesses of various approaches to time averaging of exposures and impact on risk estimates associated with intermittent exposures to lead in soil. The International Commission of Radiological Protection (ICRP) model of lead pharmacokinetics in humans simulates lead intakes that can vary in intensity over time spans as small as one day, allowing for the simulation of intermittent exposures to lead as a series of discrete daily exposure events. The ICRP model was used to compare the outcomes (blood lead concentration) of various time-averaging adjustments for approximating the time-averaged intake of lead associated with various intermittent exposure patterns. Results of these analyses suggest that standard approaches to time averaging (e.g., U.S. EPA) that estimate the long-term daily exposure concentration can, in some cases, result in substantial underprediction of short-term variations in blood lead concentrations when used in models that operate with EMATs exceeding the shortest exposure duration that characterizes the intermittent exposure. Alternative time-averaging approaches recommended for use in lead risk assessment more reliably predict short-term periodic (e.g., seasonal) elevations in blood lead concentration that might result from intermittent exposures. In general, risk estimates will be improved by simulation on shorter time scales that more closely approximate the actual temporal dynamics of the exposure.     

Mentors for adolescents in foster care

Significant numbers of adolescents in foster placement plan to live independently following discharge. Mentoring is increasingly being used as a support service to assist older foster youths to make the transition to adult living. A survey of 29 child welfare programs indicate that a variety of mentoring models are in use. The main models are transitional Life Skills Mentors, Cultural-Empowerment Mentors, and Corporate-Business Mentors. Mentoring connects foster wards with a cross-section of community citizens who provide a bridge to higher education and employment, and serve as a resource for transitional problem-solving. Information is needed on the impacts of mentor-mentee matches and efforts to sustain mentor-mentee relationships.Based on a paper presented at the Second National Child Welfare Conference, Division of Child Welfare Research, Arlington, Virginia, 1994. The research is supported by Research Grant #90CW1026 entitled Mentors as Resources for Preparing Foster Youths for Independent Living, from the Department of Health and Human Services, Administration for Children and Families, Washington, D.C.the Principal Investigator, Foster Youth Project and Adolescent Mentor Project.     

Improving Field Instruction: An Evaluation of a Seminar for New Field Instructors

Abstract

The field work component of social work education plays an important role in fusing the knowledge, skills, and values of the profession. Moreover, field instructors must be competent to ensure the success of the educational process. Thus, the training of new field instructors is critical to this success. This article reports the findings of a study evaluating the impact of a training seminar for new field instructors on student perceptions of the field experience. A 10-session seminar in field instruction was offered to new direct practice field instructors as a requirement for continued supervision of students. Students' responses to a questionnaire about their field instruction indicated that seminar attendance was related to the degree of emphasis on teaching students from process recordings and also on discussion of student learning needs. Students with trained field instructors were more satisfied with the faculty field liaison. Overall, trained instructors demonstrated expected supervisory behavior more often than untrained instructors for 75% of the 83 supervisory activities studied, although only a limited number of comparisons reached statistical significance.