Prediction and model evaluation for space-time data.

Evaluation metrics for prediction error, model selection and model averaging on space-time data are understudied and poorly understood. The absence of independent replication makes prediction ambiguous as a concept and renders evaluation procedures developed for independent data inappropriate for most space-time prediction problems. Motivated by air pollution data collected during California wildfires in 2008, this manuscript attempts a formalization of the true prediction error associated with spatial interpolation. We investigate a variety of cross-validation (CV) procedures employing both simulations and case studies to provide insight into the nature of the estimand targeted by alternative data partition strategies. Consistent with recent best practice, we find that location-based cross-validation is appropriate for estimating spatial interpolation error as in our analysis of the California wildfire data. Interestingly, commonly held notions of bias-variance trade-off of CV fold size do not trivially apply to dependent data, and we recommend leave-one-location-out (LOLO) CV as the preferred prediction error metric for spatial interpolation.

Effect modification of the association between fine particulate air pollution during a wildfire event and respiratory health by area-level measures of socio-economic status, race/ethnicity, and smoking prevalence.

Fine particulate air pollution (PM2.5) is decreasing in most areas of the United States, except for areas most affected by wildfires, where increasing trends in PM2.5 can be attributed to wildfire smoke. The frequency and duration of large wildfires and the length of the wildfire season have all increased in recent decades, partially due to climate change, and wildfire risk is projected to increase further in many regions including the western United States. Increasingly, empirical evidence suggests differential health effects from air pollution by class and race; however, few studies have investigated such differential health impacts from air pollution during a wildfire event. We investigated differential risk of respiratory health impacts during the 2008 northern California wildfires by a comprehensive list of socio-economic status (SES), race/ethnicity, and smoking prevalence variables. Regardless of SES level across nine measures of SES, we found significant associations between PM2.5 and asthma hospitalizations and emergency department (ED) visits during these wildfires. Differential respiratory health risk was found by SES for ED visits for chronic obstructive pulmonary disease where the highest risks were in ZIP codes with the lowest SES levels. Findings for differential effects by race/ethnicity were less consistent across health outcomes. We found that ZIP codes with higher prevalence of smokers had greater risk of ED visits for asthma and pneumonia. Our study suggests that public health efforts to decrease exposures to high levels of air pollution during wildfires should focus on lower SES communities.

Relating Nanoparticle Properties to Biological Outcomes in Exposure Escalation Experiments.

A fundamental goal in nano-toxicology is that of identifying particle physical and chemical properties, which are likely to explain biological hazard. The first line of screening for potentially adverse outcomes often consists of exposure escalation experiments, involving the exposure of micro-organisms or cell lines to a library of nanomaterials. We discuss a modeling strategy, that relates the outcome of an exposure escalation experiment to nanoparticle properties. Our approach makes use of a hierarchical decision process, where we jointly identify particles that initiate adverse biological outcomes and explain the probability of this event in terms of the particle physicochemical descriptors. The proposed inferential framework results in summaries that are easily interpretable as simple probability statements. We present the application of the proposed method to a data set on 24 metal oxides nanoparticles, characterized in relation to their electrical, crystal and dissolution properties.

The impact of breast cancer knowledge and attitudes on screening and early detection among an immigrant Iranian population in southern California.

Few studies explored factors influencing breast cancer screening and early detection behaviors among immigrant Iranian women residing in the USA. Using a cross-sectional survey, a convenience sample of 319 Iranian American women was selected to investigate the impact of breast cancer knowledge and attitude on screening. A self-administered questionnaire assessed breast cancer screening knowledge, attitude, and mammography use (ever, previous year, and future intention). 79 % of the women in the study reported ever receiving at least one mammogram and 74 % received a mammogram in the past year. Personal attitude had an independent significant effect on: mammography use in the last year, ever use of mammography, and future intention to screen. Knowledge and morality-induced attitude influenced screening behavior but not significantly. Interventions targeting breast cancer screening among immigrant Iranian women in the USA should focus on enhancing personal attitudes in order to influence actual screening behavior.

Organic contaminants in direct coal liquefaction--a preliminary assessment.

Area samples taken at two coal liquefaction facilities were analyzed by either gas chromatography or gas chromatography/mass spectrometry to identify the types of organic contaminants to which workers may be exposed. Results indicate that the contaminants consisted primarily of one or two ring low-molecular weight aromatic compounds.

Coal liquefaction: recent findings in occupational safety and health.

Some coal liquefaction materials are potentially hazardous because of similarities to materials in other related coal processes that have been associated with a high cancer risk. Limited survey data obtained by NIOSH at two coal liquefaction pilot plants have shown that workers were exposed to low concentrations of certain polynuclear aromatic hydrocarbons (PNA's) and aromatic amines, some of which are suspected carcinogens. The degree of risk incurred by such exposures cannot be determined because toxicologic data allowing for the evaluation of effects at low exposure levels are unavailable. These industrial hygiene studies are discussed as well as recent health and process aspects of this technology.