Measurement error caused by spatial misalignment in environmental epidemiology

Copyright @ 2009 Gryparis et al - Published by Oxford University Press.In many environmental epidemiology studies, the locations and/or times of exposure measurements and health assessments do not match. In such settings, health effects analyses often use the predictions from an exposure model as a covariate in a regression model. Such exposure predictions contain some measurement error as the predicted values do not equal the true exposures. We provide a framework for spatial measurement error modeling, showing that smoothing induces a Berkson-type measurement error with nondiagonal error structure. From this viewpoint, we review the existing approaches to estimation in a linear regression health model, including direct use of the spatial predictions and exposure simulation, and explore some modified approaches, including Bayesian models and out-of-sample regression calibration, motivated by measurement error principles. We then extend this work to the generalized linear model framework for health outcomes. Based on analytical considerations and simulation results, we compare the performance of all these approaches under several spatial models for exposure. Our comparisons underscore several important points. First, exposure simulation can perform very poorly under certain realistic scenarios. Second, the relative performance of the different methods depends on the nature of the underlying exposure surface. Third, traditional measurement error concepts can help to explain the relative practical performance of the different methods. We apply the methods to data on the association between levels of particulate matter and birth weight in the greater Boston area.This research was supported by NIEHS grants ES012044 (AG, BAC), ES009825 (JS, BAC), ES007142 (CJP), and ES000002 (CJP), and EPA grant R-832416 (JS, BAC)

Economic Valuation of Black-faced Spoonbill Conservation in Macao

The general objective of this study is to estimate the economic benefits of black-faced Spoonbill conservation in Macao based on public preferences. The specific objectives are as follows to investigate the public's awareness, attitudes and behaviors regarding black-faced Spoonbill conservation in Macao; to estimate the public's willingness to pay (WTP) for the conservation of black-faced Spoonbills in Macao; to identify the factors that affect the WTP; to determine the cost and benefits of a conservation program for black-faced Spoonbills in Macao, to recommend potential funding mechanisms; to run an experiment on hypothetical and real WTP in Macao to validate the large scale CVM study.economic valuation, Macao

Nitrogen deposition onto the United States and Western Europe: A synthesis of observations and models.

The documented acceleration of NH3 and NOx (NO + NO2) emissions over the last 150 years has accelerated N deposition, compromising air and water quality and altering the functioning of terrestrial and aquatic ecosystems worldwide. To construct continental-scale N budgets, we produced maps of N deposition fluxes from site-network observations for the United States and Western Europe. Increases in the rates of N cycling for these two regions of the world are large, and they have undergone profound modification of biospheric–atmospheric N exchanges, and ecosystem function. The maps are necessarily restricted to the network measured quantities and consist of statistically interpolated fields of aqueous NO3− and NH4+, gaseous HNO3 and NO2 (in Europe), and particulate NO3− and NH4+. There remain a number of gaps in the budgets, including organic N and NH3 deposition. The interpolated spatially continuous fields allow estimation of regionally integrated budget terms. Dry-deposition fluxes were the most problematic because of low station density and uncertainties associated with exchange mechanisms. We estimated dry N deposition fluxes by multiplying interpolated surface-air concentrations for each chemical species by model-calculated, spatially explicit deposition velocities. Deposition of the oxidized N species, by-products of fossil-fuel combustion, dominate the U.S. N deposition budget with 2.5 Tg of NOy-N out of a total of 3.7–4.5 Tg of N deposited annually onto the conterminous United States. Deposition of the reduced species, which are by-products of farming and animal husbandry, dominate the Western European N-deposition budget with a total of 4.3–6.3 Tg N deposited each year out of a total of 8.4–10.8 Tg N. Western Europe receives five times more N in precipitation than does the conterminous United States. Estimated N emissions exceed measured deposition in the United States by 5.3– 7.81 Tg N, suggesting significant N export or under-sampling of urban influence. In Europe, estimated emissions better balance measured deposition, with an imbalance of between −0.63 and 2.88 Tg N, suggesting that much of the N emitted in Europe is deposited there, with possible N import from the United States. The sampling network in Europe includes urban influences because of the greater population density of Western Europe. Our analysis of N deposition for both regions was limited by sampling density. The framework we present for quantification of patterns of N deposition provides a constraint on our understanding of continental biospheric–atmospheric N cycles. These spatially explicit wet and dry N fluxes also provide a tool for verifying regional and global models of atmospheric chemistry and transport, and they represent critical inputs into terrestrial models of biogeochemistry

Ozone Externalities on Crop Production: Insights from UK Farm Level Data

Tropospheric ozone is an air pollutant thought to reduce crop yields across Europe. Much experimental scientific work has been completed or is currently underway to quantify yield effects at ambient ozone levels. In this research, we seek to directly evaluate whether such effects are observed at the farm level. We use both primal (production function) as well as dual (profit function) methods, with ozone as a fixed input, to explore the extent to which output and profits are affected by ozone in the UK. A panel dataset on UK farms is intersected with spatial data on ozone, and panel data production and profit function estimation methods are used. The production function does predict a statistically significant negative effect of ozone on wheat yields at the farm level. However, this elasticity is small, and indicates that ozone is unlikely to result in the imposition of substantial external costs on wheat production. The profit function implications regarding ozone are less clear. Although the estimates indicate that ozone depresses wheat farm profits and wheat supply, the elasticities are statistically insignificant, and few definite conclusions can be drawn. We conclude that the farm-level evidence does not show a substantial ozone effect in the UK, and that it may be wise to interpret economic valuations based upon experimental results with some caution.ozone, wheat, crop production, production function, profit function, Crop Production/Industries, Resource /Energy Economics and Policy, Q4, P2,

Climate Change, Mortality, and Adaptation: Evidence from Annual Fluctuations in Weather in the US

This paper produces the first large-scale estimates of the US health related welfare costs due to climate change. Using the presumably random year-to-year variation in temperature and two state of the art climate models, the analysis suggests that under a "business as usual" scenario climate change will lead to an increase in the overall US annual mortality rate ranging from 0.5% to 1.7% by the end of the 21st century. These overall estimates are statistically indistinguishable from zero, although there is evidence of statistically significant increases in mortality rates for some subpopulations, particularly infants. As the canonical Becker-Grossman health production function model highlights, the full welfare impact will be reflected in health outcomes and increased consumption of goods that preserve individuals' health. Individuals' likely first compensatory response is increased use of air conditioning; the analysis indicates that climate change would increase US annual residential energy consumption by a statistically significant 15% to 30% ($15 to$35 billion in 2006 dollars) at the end of the century. It seems reasonable to assume that the mortality impacts would be larger without the increased energy consumption. Further, the estimated mortality and energy impacts likely overstate the long-run impacts on these outcomes, since individuals can engage in a wider set of adaptations in the longer run to mitigate costs. Overall, the analysis suggests that the health related welfare costs of higher temperatures due to climate change are likely to be quite modest in the US.

Improvement of the Fairbanks Atmospheric Carbon Monoxide Transport Model -- A Program for Calibration, Verification and Implementation

Completion Report Prepared for the Research Section, Alaska Department of Transportation and Public FacilitiesIn the early 70s, state, local and federal officials in Fairbanks, Alaska, became concerned with the rising incidence of high carbon monoxide episodes. Because of that concern, the Alaska Department of Highways (forerunner of the Department of Transportation and Public Facilities) and the Fairbanks North Star Borough requested that the Institute of Water Resources undertake a study to develop a computer model capability for understanding the transport of carbon monoxide and other pollutants within the Fairbanks airshed. The work was completed in June of 1976. Two publications (Carlson and Fox, 1976; Norton and Carlson, 1976) describe the initial development, documentation and implementation of the computer model. The model, ACOSP (Atmospheric Carbon monOxide Simulation Program), describes the two-dimensional behavior of pollutants in the atmosphere via solution of the convection-diffusion equation using the finite element method of numerical analysis