Comparison of quantitative risk assessment procedures based on overdispersed data from developmental toxicity studies.

Quantitative risk assessment of noncarcinogens has been based on the estimation of the no-observed-adverse-effect-level (NOAEL). The NOAEL procedure has been shown to be unsatisfactory by many scientists. The fitting of dose-response models to teratology data involving littermates in order to estimate a teratogenic risk is becoming more popular as a potential alternative to the traditional approach to risk assessment. In this thesis a comparison of the different methods of risk assessment (NOAEL, ED\sb{\alpha} and BMD\sb{\alpha}) are conducted through a simulation study and through real life developmental toxicity data. The estimates ED\sb{\alpha} and BMD\sb{\alpha} are computed with both the Dirichlet-trinomial and beta-binomial variance function, generalized linear model variance function and with the Rao-Scott transformation.Dept. of Mathematics and Statistics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1996 .M375. Source: Masters Abstracts International, Volume: 37-01, page: 0280. Adviser: K. Fung. Thesis (M.Sc.)--University of Windsor (Canada), 1996

Impacts of Subway System Modifications on Air Quality in Subway Platforms and Trains.

Subway PM₂.₅ can be substantially sourced from the operation of the system itself. Improvements in subway air quality may be possible by examining the potential to reduce these emissions. To this end, PM₂.₅ was measured on the trains and station platforms of the Toronto subway system. A comparison with previously published data for this system reveals significant changes in below ground platform PM₂.₅. A reduction of nearly one-third (ratio (95% CI): 0.69 (0.63, 0.75)) in PM₂.₅ from 2011 to 2018 appears to have resulted from a complete modernization of the rolling stock on one subway line. In contrast, below ground platform PM₂.₅ for another line increased by a factor of 1.48 (95% CI; 1.42, 1.56). This increase may be related to an increase in emergency brake applications, the resolution of which coincided with a large decrease in PM₂.₅ concentrations on that line. Finally, platform PM₂.₅ in two newly opened stations attained, within one year of operation, typical concentrations of the neighboring platforms installed in 1963. Combined, these findings suggest that the production of platform PM₂.₅ is localized and hence largely freshly emitted. Further, PM₂.₅ changed across this subway system due to changes in its operation and rolling stock. Thus, similar interventions applied intentionally may prove to be equally effective in reducing PM₂.₅. Moreover, establishing a network of platform PM₂.₅ monitors is recommended to monitor ongoing improvements and identify impacts of future system changes on subway air quality. This would result in a better understanding of the relationship between the operations and air quality of subways

Can changing the timing of outdoor air intake reduce indoor concentrations of traffic-related pollutants in schools?

Traffic emissions have been associated with a wide range of adverse health effects. Many schools are situated close to major roads, and as children spend much of their day in school, methods to reduce traffic-related air pollutant concentrations in the school environment are warranted. One promising method to reduce pollutant concentrations in schools is to alter the timing of the ventilation so that high ventilation time periods do not correspond to rush hour traffic. Health Canada, in collaboration with the Ottawa-Carleton District School Board, tested the effect of this action by collecting traffic-related air pollution data from four schools in Ottawa, Canada, during October and November 2013. A baseline and intervention period was assessed in each school. There were statistically significant (P \u3c 0.05) reductions in concentrations of most of the pollutants measured at the two late-start (9 AM start) schools, after adjusting for outdoor concentrations and the absolute indoor–outdoor temperature difference. The intervention at the early-start (8 AM start) schools did not have significant reductions in pollutant concentrations. Based on these findings, changing the timing of the ventilation may be a cost-effective mechanism of reducing traffic-related pollutants in late-start schools located near major roads. © 2015 Her Majesty the Queen in Right of Canada. Indoor Air published by John Wiley & Sons Ltd. Reproduced with the permission of the Minister of Health Canada

Exposure to wind turbine noise: Perceptual responses and reported health effects

Health Canada, in collaboration with Statistics Canada, and other external experts, conducted the Community Noise and Health Study to better understand the impacts of wind turbine noise (WTN) on health and well-being. A cross-sectional epidemiological study was carried out between May and September 2013 in southwestern Ontario and Prince Edward Island on 1238 randomly selected participants (606 males, 632 females) aged 18-79 years, living between 0.25 and 11.22 km from operational wind turbines. Calculated outdoor WTN levels at the dwelling reached 46 dBA. Response rate was 78.9% and did not significantly differ across sample strata. Self-reported health effects (e.g., migraines, tinnitus, dizziness, etc.), sleep disturbance, sleep disorders, quality of life, and perceived stress were not related to WTN levels. Visual and auditory perception of wind turbines as reported by respondents increased significantly with increasing WTN levels as did high annoyance toward several wind turbine features, including the following: noise, blinking lights, shadow flicker, visual impacts, and vibrations. Concern for physical safety and closing bedroom windows to reduce WTN during sleep also increased with increasing WTN levels. Other sample characteristics are discussed in relation to WTN levels. Beyond annoyance, results do not support an association between exposure to WTN up to 46 dBA and the evaluated health-related endpoints

Variation in the stringency of COVID-19 public health measures on self-reported health, stress, and overall wellbeing in Canada

Abstract Evidence is building regarding the association between government implemented public health measures aimed at combating COVID-19 and their impacts on health. This study investigated the relationship between the stringency of public health measures implemented in Canada and self-reported mental health, physical health, stress, and wellbeing among a random sample of 6647 Canadians 18 years of age and older. The analysis was based on self-reported health data from the Canadian Perspectives on Environmental Noise Survey. This data was combined with the Oxford COVID-19 Government Response Tracker database, which included overall stringency index (SI), and four of its sub-components, i.e., school and business closures, restrictions on gatherings, and stay at home policies. Adjusted multivariate logistic regression models indicated that the magnitude of the overall SI was associated with higher or lower odds of reporting worse physical health, mental health, stress and/or overall wellbeing, depending on the measure evaluated. Similarly, policy directed at the four sub-components had varying impacts on the odds of reporting worse health, depending on the sub-component, the strength of the policy restriction, and the health outcome evaluated. The association between the strength of the public health measures and self-reported health, and how this may inform future policy, is discussed

Validation of the cytokinesis-block micronucleus (CBMN) assay for use as a triage biological dosimetry tool

Traditionally, the dicentric chromosome assay (DCA) has been used to derive biological dose estimates for unknown radiological exposures. While sensitive, this assay requires highly trained evaluators and is extremely time consuming. The cytokinesis-block micronucleus (CBMN) assay has been suggested as an alternative to the DCA, as it is much faster to evaluate samples and requires less technical expertise. In order to validate this assay for triage biodosimetry, dose-response curves were generated for six donors at eight doses of gamma-radiation (0-4.0 Gy). Each sample was evaluated by 12 individuals, among three different laboratories and the incidence of micronuclei was determined after counting 50-500 binucleated cells. This study demonstrated that the CBMN assay was capable of detecting radiation doses ≥1 Gy after scoring only 200 binucleated cells. As such, the CBMN assay may provide a sensitive and reliable technique for deployment as an initial screening tool in a large-scale radiological emergency where large numbers of biological dose estimates are required

Characteristics of naphthalene and its sources in Edmonton, Alberta residences during winter and summer 2010

Residential living room, basement, and attached garage air concentrations of naphthalene were measured in Edmonton, Alberta. Sevenday average measurements were made in 50 nonsmoking homes in winter and summer 2010. Data on relative humidity, indoor and outdoor temperature, air exchange rate, home characteristics and occupants’ activities were collected. Median indoor levels (0.32 g/m3 in winter and 0.29 \u10021dg/m3 in summer) were at the low end of the range from studies reported in scientific literature. Higher attached garage/living room naphthalene concentration ratios observed in summer versus winter suggest that attached garages make a greater contribution to indoor naphthalene levels in summer than in winter. Smoking and use of moth repellents are known sources of indoor naphthalene; however neither were factors in the homes studied. Statistical analysis of data captured in questionnaires did not reveal other established/recognized determinants of indoor naphthalene levels