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.     

Osteoporosis knowledge and attitudes: a cross-sectional study among college-age students

OBJECTIVE: The authors' purpose in this study was to investigate the influence of knowledge of osteoporosis, attitudes regarding osteoporosis, and knowledge of dietary calcium on dairy product intake in both male and female college-age students. PARTICIPANTS: The authors conducted this cross-sectional study on 911 men and women enrolled in 2 demographically similar universities. METHODS: A modified osteoporosis knowledge questionnaire assessed participant's general osteoporosis knowledge and perceived disease risk. RESULTS: The authors found that knowledge of osteoporosis and calcium did not significantly influence dairy product intake. Attitude regarding osteoporosis was a significant predictor of dairy product intake in men but was not significant for the women. CONCLUSIONS: The authors recommend development and implementation of educational programs designed to increase awareness of calcium-rich food sources as well as other risk factors of this crippling disease.     

When Do First-Year College Students Drink Most During the Academic Year? An Internet-Based Study of Daily and Weekly Drinking

Abstract

Objective: The authors investigated the alcohol consumption trajectories among first-year university students. Participants: A sample of 415 students attending a large university in Southwestern Ontario, Canada, was recruited. Methods: Students completed a baseline questionnaire and 26 weekly brief Internet surveys assessing alcohol consumption from September 2006 to April 2007. Results: Findings indicated that alcohol consumption varies considerably as a function of time of the academic year. Overall trends indicate that students drink more heavily at the beginning of each semester and less during exam periods. Daily patterns indicate that most drinking occurs on weekends. The highest drinking days in the first academic year included Halloween, New Year's Eve, and St. Patrick's Day. Conclusions: The present study provides evidence that periods of high and low alcohol consumption are contingent upon specific events and the time of the year.     

Rebecca Tiessen,Benjamin J. Lough,and Kate E. Grantham (eds.), Insights on International Volunteering: Perspectives from the Global South

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations -     

Know thy self,know thy leader: Contributions of a pattern-oriented approach to examining leader perceptions

This study investigated how patterns of traits in self and ideal leader profiles were related to one another, beyond the individual effects of each trait. Latent profile analysis (LPA) was used to identify and describe profiles of self leader and ideal leader perceptions. Four profiles for self leader perceptions (Prototypical, Laissez-Faire, Narcissistic, Anti-Prototypical) and four profiles for ideal leader perceptions (Prototypical, Laissez-Faire, Autocratic, Anti-Prototypical) were identified. Additional analyses examined the association between self and ideal leader profiles; gender, leadership self efficacy, and narcissism were added to the model as predictors of that association. Prototypical and Laissez-Faire self leaders tended to prefer an ideal leader who was similar to themselves, whereas Narcissistic and Anti-Prototypical self leaders had more diffuse preferences in ideal leaders. Gender, leadership self efficacy, and narcissism were only associated with self leader profiles. Results support, yet contribute beyond, previous findings for the similarity hypothesis.