Estimation of relative risk for events on a linear network

Motivated by the study of traffic accidents on a road network, we discuss the estimation of the relative risk, the ratio of rates of occurrence of different types of events occurring on a network of lines. Methods developed for two-dimensional spatial point patterns can be adapted to a linear network, but their requirements and performance are very different on a network. Computation is slow and we introduce new techniques to accelerate it. Intensities (occurrence rates) are estimated by kernel smoothing using the heat kernel on the network. The main methodological problem is bandwidth selection. Binary regression methods, such as likelihood cross-validation and least squares cross-validation, perform tolerably well in our simulation experiments, but the Kelsall–Diggle density-ratio cross-validation method does not. We find a theoretical explanation, and propose a modification of the Kelsall–Diggle method which has better performance. The methods are applied to traffic accidents in a regional city, and to protrusions on the dendritic tree of a neuron

Environmental and reproductive health: A spatial analysis of adverse birth outcomes and environmental contaminants in British Columbia.

Exposure to contaminants during pregnancy is associated with certain adverse birth outcomes that require further investigation. Community reproductive and environmental health risk maps were produced utilizing birth data obtained from the B.C. Perinatal Health Program and environmental contaminant data from the National Pollutant Release inventory and other national and provincial sources. Geographical information systems (GIS) were utilized to spatially relate perinatal and environmental hazard data, and the risk of adverse birth outcomes was tested using watersheds as the ecological aggregation unit adjusting for individual-level risk factors. The perinatal data included birth outcomes (low birth weight, prematurity, inter-uterine growth restriction, congenital anomalies, stillbirths) and numerous maternal and antenatal risk factor data for all singleton births in B.C. from 2001 to 2006. Small but significant increased risks of adverse birth outcomes were found in high and intermediate hazard watersheds compared to low hazard watersheds. This suggests a possible environmental effect on these reproductive outcomes, however, further studies are needed to corroborate these results. --P.ii.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b165168