Methods of exposure assessment: lead-contaminated dust in Philadelphia schools.

This study was conducted to develop a method that would accurately assess children's exposure to lead in schools in Philadelphia, Pennsylvania. We examined three wipe sample protocols: one included accessible surfaces such as desktops and windowsills, the second included inaccessible surfaces such as the top of filing cabinets and light fixtures, and the third included hand wipes of the study participants. Surface wipes were collected at 10 locations from accessible and inaccessible classroom surfaces (n = 11 at each location) and from the palms of student subjects in the same locations (n = 168). We found a significant difference in lead dust concentrations determined by the three protocols (F = 4.619; 2,27 degrees of freedom; p = 0.019). Lead dust concentrations were significantly elevated at the inaccessible surfaces yet they were uniformly low on the accessible surfaces and the children's palms. These findings were consistent with observed changes in blood lead levels of study participants: after 6 months of exposure to the study locations, 156 of 168 children experienced no change in blood lead level, whereas 12 experienced only a minimal change of 1-2 microg/dL. The mere presence of lead in inaccessible dust in the school environment does not automatically constitute a health hazard because there may not be a completed exposure pathway

Haematidrosis: The Rare Phenomenon of Sweating Blood

Objectives: Haematidrosis, also known as haematohidrosis, is a very rare condition where blood is excreted with sweat. As only a few cases have been described in the literature, we present guidelines on management of this rare phenomenon. Case: A 44-year-old man presented with self-limited and spontaneous bleeding episodes from different parts of his body. This had started 2 weeks before admission after an episode of extreme emotional stress. Medical history and laboratory tests were normal. The microscopic examination of a sample of the fluid excreted confirmed all blood elements. Conclusion: The disorder is thought to be related to activation of the sympathetic nervous system. The use of benzodiazepines and beta blockers may be helpful in controlling the bleeding episodes and give some comfort to the patient

Air pollution exposure estimation using dispersion modelling and continuous monitoring data in a prospective birth cohort study in the Netherlands

Previous studies suggest that pregnant women and children are particularly vulnerable to the adverse effects of air pollution. A prospective cohort study in pregnant women and their children enables identification of the specific effects and critical periods. This paper describes the design of air pollution exposure assessment for participants of the Generation R Study, a population-based prospective cohort study from early pregnancy onwards in 9778 women in the Netherlands. Individual exposures to PM10 and NO2 levels at the home address were estimated for mothers and children, using a combination of advanced dispersion modelling and continuous monitoring data, taking into account the spatial and temporal variation in air pollution concentrations. Full residential history was considered. We observed substantial spatial and temporal variation in air pollution exposure levels. The Generation R Study provides unique possibilities to examine effects of short- and long-term air pollution exposure on various maternal and childhood outcomes and to identify potential critical windows of exposure

Essays in Applied Economics

Essay 1 studies physician agency problems, which arise whenever physicians fail to maximize their patients\u27 preferences, given available information. These agency problems are well documented, but the magnitude of their welfare consequences for patients---the losses from suboptimal treatment choice induced by agency---are unclear. I infer patient drug preference from their compliance decisions. I begin by showing that initial prescriptions respond to physician financial incentives to control costs and to pharmaceutical detailing, but compliance does not, pointing to agency problems. I then develop and estimate a model of physician-patient interactions where physician write initial prescriptions, but patients choose whether to comply. Fully eliminating agency problems increases compliance by 6.5 percentage points, and raises patient welfare by 22\% of drug spending. Contracts that better align doctor and patient preferences can improve patient welfare, but attain only half the gains from eliminating agency completely. Although physician agency problems reduce patient welfare, eliminating them is thus likely difficult. Essay 2, co-authored with Alexander M. Gelber and Damon Jones, studies frictions in adjusting earnings to changes in the Social Security Annual Earnings Test (AET) using a panel of Social Security Administration microdata on one percent of the U.S. population from 1961 to 2006. Individuals continue to bunch at the convex kink the AET creates even when they are no longer subject to the AET, consistent with the existence of earnings adjustment frictions in the U.S. We develop a novel estimation framework and estimate in a baseline case that the earnings elasticity with respect to the implicit net-of-tax share is 0.23, and the fixed cost of adjustment is \$152.08. Essay 3 studies the impact of health expenditure risk on annuitization. Theoretical research suggests that such risk can have an ambiguous influence on the annuitization decisions of the elderly. I provide empirical evidence on this linkage, by estimating the impact of supplemental Medicare insurance (Medigap) coverage on the annuity demand of older Americans. Medigap coverage has a strong impact on annuitization: the extensive margin elasticity is 0.39, the overall elasticity of private annuity income with respect to Medigap coverage is 0.56. These results are robust to controls for health, wealth, and preferences, as well as other robustness tests. They suggest that medical expenditure risk has a large impact on underannuitization

On the Automatic Guidance System with Crab-Steering

Among the steering modes of farm tractor, the crab-steering has hardly been taken up in production and also in research. That mode of steering may be unapplicable to manual operating that has made familiar with normal mode of steering for long time, but because the vehicle with that mode can always hold its body in a certine direction, that type has a profitable property for the automatic guidance in field operation, and positional relation of sensor and implement is one-dimensional problem and attaching point of sensor to body is unrestricted. This type vehicle can not turn, but travelling of field operation necessitates no turning in many kinds of operations except at head land. At head land, it may be solved to change steering mode. The authors aspect to the property of crab-steering and aimed to develop the automatic guidance system with this steering mode. In this paper, the stability of relay-control system of automatic guidance was considered with describing-function method, and the results of tracking tests with trial vehicle were discussed and considered by means of time varying Fourier coefficients of tracking pass

Chronic Air Pollution Exposure during Pregnancy and Maternal and Fetal C-Reactive Protein Levels: The Generation R Study

Background: Exposure to air pollution has been associated with higher C-reactive protein (CRP) levels, suggesting an inflammatory response. Not much is known about this association in pregnancy