HealthyPlan.City: A Web Tool to Support Urban Environmental Equity and Public Health in Canadian Communities.

Urban environmental factors such as air quality, heat islands, and access to greenspaces and community amenities impact public health. Some vulnerable populations such as low-income groups, children, older adults, new immigrants, and visible minorities live in areas with fewer beneficial conditions, and therefore, face greater health risks. Planning and advocating for equitable healthy urban environments requires systematic analysis of reliable spatial data to identify where vulnerable populations intersect with positive or negative urban/environmental characteristics. To facilitate this effort in Canada, we developed HealthyPlan.City ( https://healthyplan.city/ ), a freely available web mapping platform for users to visualize the spatial patterns of built environment indicators, vulnerable populations, and environmental inequity within over 125 Canadian cities. This tool helps users identify areas within Canadian cities where relatively higher proportions of vulnerable populations experience lower than average levels of beneficial environmental conditions, which we refer to as Equity priority areas. Using nationally standardized environmental data from satellite imagery and other large geospatial databases and demographic data from the Canadian Census, HealthyPlan.City provides a block-by-block snapshot of environmental inequities in Canadian cities. The tool aims to support urban planners, public health professionals, policy makers, and community organizers to identify neighborhoods where targeted investments and improvements to the local environment would simultaneously help communities address environmental inequities, promote public health, and adapt to climate change. In this paper, we report on the key considerations that informed our approach to developing this tool and describe the current web-based application.

Global, regional and national burdens of non-melanoma skin cancer attributable to occupational exposure to solar ultraviolet radiation for 183 countries, 2000-2019: A systematic analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury.

BACKGROUND: A World Health Organization (WHO) and International Labour Organization (ILO) systematic review reported sufficient evidence for higher risk of non-melanoma skin cancer (NMSC) amongst people occupationally exposed to solar ultraviolet radiation (UVR). This article presents WHO/ILO Joint Estimates of global, regional, national and subnational occupational exposures to UVR for 195 countries/areas and the global, regional and national attributable burdens of NMSC for 183 countries, by sex and age group, for the years 2000, 2010 and 2019. METHODS: We calculated population-attributable fractions (PAFs) from estimates of the population occupationally exposed to UVR and the risk ratio for NMSC from the WHO/ILO systematic review. Occupational exposure to UVR was modelled via proxy of occupation with outdoor work, using 166 million observations from 763 cross-sectional surveys for 96 countries/areas. Attributable NMSC burden was estimated by applying the PAFs to WHO's estimates of the total NMSC burden. Measures of inequality were calculated. RESULTS: Globally in 2019, 1.6 billion workers (95 % uncertainty range [UR] 1.6-1.6) were occupationally exposed to UVR, or 28.4 % (UR 27.9-28.8) of the working-age population. The PAFs were 29.0 % (UR 24.7-35.0) for NMSC deaths and 30.4 % (UR 29.0-31.7) for disability-adjusted life years (DALYs). Attributable NMSC burdens were 18,960 deaths (UR 18,180-19,740) and 0.5 million DALYs (UR 0.4-0.5). Men and older age groups carried larger burden. Over 2000-2019, attributable deaths and DALYs almost doubled. CONCLUSIONS: WHO and the ILO estimate that occupational exposure to UVR is common and causes substantial, inequitable and growing attributable burden of NMSC. Governments must protect outdoor workers from hazardous exposure to UVR and attributable NMSC burden and inequalities.

Association between annual exposure to air pollution and systolic blood pressure among adolescents in Montréal, Canada. / Association entre l'exposition annuelle à la pollution atmosphérique et la pression artérielle systolique chez des adolescents à Montréal (Canada).

INTRODUCTION: In adults, chronic exposure to air pollution is associated with elevated blood pressure, but few studies have examined this relationship in youth. We investigated the association between annual ambient concentrations of air pollutants (fine particulate matter [PM2.5] and nitrogen dioxide [NO2]) and systolic blood pressure (SBP) among adolescents in Montréal, Canada. METHODS: Participants were students aged 15 to 17 years who provided SBP and residential postal code data in 2004/05 through their enrolment in the Nicotine Dependence in Teens study. Annual estimates for 2004 of residential exposure to NO2 and PM2.5 were provided by the Canadian Urban Environmental Health Research Consortium and linked to participants' residential postal code. Elevated SBP was defined as SBP ≥ 90th percentile adjusted for age, sex and height. Logistic regression was used to estimate odds ratios and 95% confidence intervals (CIs) for each pollutant with respect to elevated SBP, adjusted for relevant confounders. RESULTS: The sample consisted of 508 adolescents (mean age: 16.9, 46% male); 4% had elevated SBP. Although estimates were not statistically significant, there were generally modest positive associations between pollutant levels and SBP. The adjusted prevalence odds ratio of elevated SBP was 1.33 (95% CI: 0.64, 3.05) for every interquartile range (IQR) increase in residential PM2.5 levels (2.1µg/m3). Similarly, the adjusted prevalence odds ratio of elevated SBP was 1.17 (95% CI: 0.47, 2.70) for every IQR increase in residential NO2 levels (10.2 ppb). CONCLUSION: Findings support a possible relationship between exposure to air pollutants and increased SBP in adolescents, warranting further investigation for this important public health concern.

Critical windows of exposure to air pollution and gestational diabetes: assessing effect modification by maternal pre-existing conditions and environmental factors.

BACKGROUND: Ambient air pollution has been associated with gestational diabetes (GD), but critical windows of exposure and whether maternal pre-existing conditions and other environmental factors modify the associations remains inconclusive. METHODS: We conducted a retrospective cohort study of all singleton live birth that occurred between April 1st 2006 and March 31st 2018 in Ontario, Canada. Ambient air pollution data (i.e., fine particulate matter with a diameter ≤ 2.5 µm (PM2.5), nitrogen dioxide (NO2) and ozone (O3)) were assigned to the study population in spatial resolution of approximately 1 km × 1 km. The Normalized Difference Vegetation Index (NDVI) and the Green View Index (GVI) were also used to characterize residential exposure to green space as well as the Active Living Environments (ALE) index to represent the active living friendliness. Multivariable Cox proportional hazards regression models were used to evaluate the associations. RESULTS: Among 1,310,807 pregnant individuals, 68,860 incident cases of GD were identified. We found the strongest associations between PM2.5 and GD in gestational weeks 7 to 18 (HR = 1.07 per IQR (2.7 µg/m3); 95% CI: 1.02 - 1.11)). For O3, we found two sensitive windows of exposure, with increased risk in the preconception period (HR = 1.03 per IQR increase (7.0 ppb) (95% CI: 1.01 - 1.06)) as well as gestational weeks 9 to 28 (HR 1.08 per IQR (95% CI: 1.04 -1.12)). We found that women with asthma were more at risk of GD when exposed to increasing levels of O3 (p- value for effect modification = 0.04). Exposure to air pollutants explained 20.1%, 1.4% and 4.6% of the associations between GVI, NDVI and ALE, respectively. CONCLUSION: An increase of PM2.5 exposure in early pregnancy and of O3 exposure during late first trimester and over the second trimester of pregnancy were associated with gestational diabetes whereas exposure to green space may confer a protective effect.

Increased urban greenness associated with improved mental health among middle-aged and older adults of the Canadian Longitudinal Study on Aging (CLSA).

OBJECTIVES: Some studies suggest that residential surrounding greenness is associated with improved mental health. Few of these studies have focussed on middle-aged and older adults, explored the modifying effects of social determinants of health, or accounted for the extent to which individuals interact with their neighbourhood environments. METHODS: We analysed cross-sectional data collected from 26,811 urban participants of the Canadian Longitudinal Study of Aging who were between 45 and 86 years of age. Participants provided details on socioeconomic characteristics, health behaviours, and their frequency of neighbourhood interactions. The Normalized Difference Vegetation Index (NDVI), a measure of greenness, was assigned to participants' residential addresses at a buffer distance of 500 m. Four self-reported measures of mental health were considered: The Center for Epidemiologic Studies Depression Scale (CES-D-10; short scale), past diagnosis of clinical depression, perceptions of mental health, and the Satisfaction with Life Scale (SWLS). Regression models were used to describe associations between greenness and these outcomes, and spline models were fit to characterize the exposure-response function between greenness and CES-D-10 scores. Stratified analyses evaluated whether associations varied by sociodemographic status. RESULTS: In adjusted models, we observed a 5% (Odds Ratio (OR) = 0.95; 95% CI = 0.90, 0.99) reduced odds of depressive symptoms in relation to an interquartile range increase of NDVI (0.06) within a 500 m buffer of the participant's residence. Similarly, we found an inverse association with a self-reported clinical diagnosis of depression (OR = 0.97; 95% CI = 0.92-1.01). Increases in surrounding greenness were associated with improved perceptions of mental health, and the SWLS. Our spline analyses found that beneficial effects between greenness and the CES-D-10 were strongest among those of lower income. CONCLUSIONS: These findings suggest that residential greenness has mental health benefits, and that interventions to increase urban greenness can help reduce social inequalities in mental health.

Estimating the future cancer management costs attributable to modifiable risk factors in Canada.

OBJECTIVES: An estimated 33-37% of incident cancers in Canada are attributable to modifiable risk factors. Interventions targeting these risk factors would minimize the substantial health and economic burdens Canadians face due to cancer. We estimate the future health and economic burden of cancer in Canada by incorporating data from the Canadian Population Attributable Risk of Cancer (ComPARe) study into OncoSim, a web-based microsimulation tool. METHODS: Using the integrated OncoSim population attributable risk and population impact measures, we evaluated risk factor-targeted intervention scenarios implemented in 2020, assuming the targeted risk factor prevalence reduction would be achieved by 2032 with a 12-year latency period. RESULTS: We estimate that smoking will be the largest contributor to cancer-related costs, with a cost of CAD $44.4 billion between 2032 and 2044. An estimated CAD $3.3 billion of the cost could be avoided with a 30% reduction in smoking prevalence by 2022. Following smoking, the next highest cancer management costs are associated with inadequate physical activity and excess body weight, accounting for CAD $10.7 billion ($2.7 billion avoidable) and CAD $9.8 billion ($3.2 billion avoidable), respectively. Avoidable costs for other risk factors range from CAD $90 million to CAD $2.5 billion. CONCLUSION: Interventions targeting modifiable cancer risk factors could prevent a substantial number of incident cancer cases and billions of dollars in cancer management costs. With limited budgets and rising costs in cancer care in Canada, these simulation models and results are valuable for researchers and policymakers to inform decisions and prioritize and evaluate intervention programs.

RéSUMé: OBJECTIFS: Il est estimé que de 33 % à 37 % des cancers incidents au Canada sont imputables à des facteurs de risque modifiables. Des interventions ciblant ces facteurs de risque réduiraient le fardeau sanitaire et économique considérable du cancer dans la population canadienne. Nous avons estimé le futur fardeau sanitaire et économique du cancer au Canada en intégrant les données de l'étude ComPARe (Canadian Population Attributable Risk of Cancer) dans l'outil de microsimulation en ligne OncoSim. MéTHODE: À l'aide des indicateurs d'impact dans la population et du risque attribuable dans la population intégrés dans OncoSim, nous avons évalué des scénarios d'intervention mis en œuvre en 2020 axés sur les facteurs de risque, en partant de l'hypothèse que la réduction de la prévalence des facteurs de risque ciblés serait atteinte d'ici 2032 avec une période de latence de 12 ans. RéSULTATS: Nous estimons que le tabagisme sera le facteur qui contribuera le plus aux coûts du cancer, avec un coût de 44,4 milliards $ CA entre 2032 et 2044. Il est estimé qu'une part de 3,3 milliards $ CA de ce coût pourrait être évitée en réduisant de 30 % la prévalence du tabagisme d'ici 2022. Après le tabagisme, les coûts de prise en charge du cancer les plus élevés sont associés à l'inactivité physique et au surpoids, qui représentent respectivement 10,7 milliard $ CA (dont 2,7 milliards $ évitables) et 9,8 milliards $ CA (dont 3,2 milliards $ évitables). Les coûts évitables pour d'autres facteurs de risque vont de 90 millions $ CA à 2,5 milliards $ CA. CONCLUSION: Des interventions ciblant les facteurs de risque de cancer modifiables pourraient prévenir un nombre considérable de cas de cancers incidents et épargner des milliards de dollars en coûts de prise en charge du cancer. Avec les budgets serrés et la hausse des coûts des soins du cancer au Canada, ces modèles de simulation et leurs résultats permettent aux chercheurs et aux responsables des politiques d'éclairer les décisions et de hiérarchiser et d'évaluer les programmes d'intervention.

Global estimates of mortality associated with long-term exposure to outdoor fine particulate matter.

Exposure to ambient fine particulate matter (PM2.5) is a major global health concern. Quantitative estimates of attributable mortality are based on disease-specific hazard ratio models that incorporate risk information from multiple PM2.5 sources (outdoor and indoor air pollution from use of solid fuels and secondhand and active smoking), requiring assumptions about equivalent exposure and toxicity. We relax these contentious assumptions by constructing a PM2.5-mortality hazard ratio function based only on cohort studies of outdoor air pollution that covers the global exposure range. We modeled the shape of the association between PM2.5 and nonaccidental mortality using data from 41 cohorts from 16 countries-the Global Exposure Mortality Model (GEMM). We then constructed GEMMs for five specific causes of death examined by the global burden of disease (GBD). The GEMM predicts 8.9 million [95% confidence interval (CI): 7.5-10.3] deaths in 2015, a figure 30% larger than that predicted by the sum of deaths among the five specific causes (6.9; 95% CI: 4.9-8.5) and 120% larger than the risk function used in the GBD (4.0; 95% CI: 3.3-4.8). Differences between the GEMM and GBD risk functions are larger for a 20% reduction in concentrations, with the GEMM predicting 220% higher excess deaths. These results suggest that PM2.5 exposure may be related to additional causes of death than the five considered by the GBD and that incorporation of risk information from other, nonoutdoor, particle sources leads to underestimation of disease burden, especially at higher concentrations.

Examining screening mammography participation among women aged 40 to 74.

OBJECTIVE: To examine participation in screening mammography among women aged 40 to 74 and identify which factors are associated with those women who participate in screening. DESIGN: Secondary analysis of the cross-sectional 2012 Canadian Community Health Survey. SETTING: Canada. PARTICIPANTS: A population-based national sample of 18 312 women aged 40 to 74. MAIN OUTCOME MEASURES: Women's participation in screening mammography in the 2 years preceding the 2012 Canadian Community Health Survey; women's preventive health activities (ie, having a regular doctor, a recent physical checkup, and a Papanicolaou test), which were adjusted for sociodemographic factors. RESULTS: Participation in recent screening mammography was highest among women aged 60 to 69 (70.3%), followed by those aged 50 to 59 (63.4%) and those aged 70 to 74 (58.4%). Almost one-third (31.4%) of women aged 40 to 49 had had a screening mammogram in the past 2 years. Having a regular doctor (odds ratio [OR] = 3.30, 95% CI 2.90 to 3.73), a physical checkup in the past year (OR = 3.06, 95% CI 2.30 to 4.08), or a Pap test in the past 3 years (OR = 3.47, 95% CI 3.18 to 3.79) more than tripled the odds that women had had a recent screening mammogram. CONCLUSION: Aside from age being a factor associated with women's participation in screening mammography, factors related to women's health care use (having a regular doctor, a recent physical checkup, and a recent Pap test) demonstrated a stronger association with women aged 40 to 74 having had recent mammograms. The association between women's participation in screening and their preventive health activities implies that the doctor's office is an appropriate venue for conversations regarding the potential benefits and harms of screening mammography.

Assessment of the effect of cold and hot temperatures on mortality in Ontario, Canada: a population-based study.

BACKGROUND: Ambient high temperature is associated with death; however, heat-related risk of death has not been quantified systematically in Ontario, the most populous province in Canada. Less is known about cold-related risk in this population. Our objective was to quantify the health impact from cold and hot temperatures in Ontario. METHODS: The study population consisted of all residents of Ontario who died between Jan. 1, 1996, and Dec. 31, 2010, from any nonaccidental cause. A case-crossover analysis was applied to assess the relation between daily temperature fluctuation and deaths from nonaccidental and selected causes in cold (December-February) and warm (June-August) seasons, respectively, adjusting for various potential confounders. Risk estimates were obtained for each census division, then pooled across Ontario. We examined potential effect modification for selected comorbidities and sociodemographic characteristics. RESULTS: In warm seasons, each 5°C increase in daily mean temperature was associated with a 2.5% increase in nonaccidental deaths (95% confidence interval [CI] = 1.3% to 3.8%) on the day of exposure (lag 0). In cold seasons, each 5°C decrease in daily temperature was associated with a 3.0% (95% CI 1.8% to 4.2%) increase in nonaccidental deaths, which persisted over 7 days (lag 0-6). The cold-related effects (lag 0-6) were stronger for cardiovascular-related deaths (any cardiovascular death: 4.1%, 95% CI 2.3% to 5.9%; ischemic heart disease: 5.8%, 95% CI 3.6% to 8.1%), especially among people less than 65 years of age (8.0%, 95% CI 3.0% to 13.0%). Conversely, heat most strongly increased respiratory-related deaths during admission to hospital (26.0%, 95% CI 0% to 61.4%). Across Ontario, each 5°C change in daily temperature was estimated to induce 7 excess deaths per day in cold seasons and 4 excess deaths in warm seasons. INTERPRETATION: Heat contributed to excess deaths in Ontario, although the effect of cold weather appeared to be greater. Further work is required to better define high-risk subgroups, which might include the homeless and people with inadequately heated housing.

Progression from Asthma to Chronic Obstructive Pulmonary Disease. Is Air Pollution a Risk Factor?

RATIONALE: Individuals with asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS), have more rapid decline in lung function, more frequent exacerbations, and poorer quality of life than those with asthma or COPD alone. Air pollution exposure is a known risk factor for asthma and COPD; however, its role in ACOS is not as well understood. OBJECTIVES: To determine if individuals with asthma exposed to higher levels of air pollution have an increased risk of ACOS. METHODS: Individuals who resided in Ontario, Canada, aged 18 years or older in 1996 with incident asthma between 1996 and 2009 who participated in the Canadian Community Health Survey were identified and followed until 2014 to determine the development of ACOS. Data on exposures to fine particulate matter (PM2.5) and ozone (O3) were obtained from fixed monitoring sites. Associations between air pollutants and ACOS were evaluated using Cox regression models. MEASUREMENTS AND MAIN RESULTS: Of the 6,040 adults with incident asthma who completed the Canadian Community Health Survey, 630 were identified as ACOS cases. Compared with those without ACOS, the ACOS population had later onset of asthma, higher proportion of mortality, and more frequent emergency department visits before COPD diagnosis. The adjusted hazard ratios of ACOS and cumulative exposures to PM2.5 (per 10 µg/m(3)) and O3 (per 10 ppb) were 2.78 (95% confidence interval, 1.62-4.78) and 1.31 (95% confidence interval, 0.71-2.39), respectively. CONCLUSIONS: Individuals exposed to higher levels of air pollution had nearly threefold greater odds of developing ACOS. Minimizing exposure to high levels of air pollution may decrease the risk of ACOS.

Urban greenness and physical activity in a national survey of Canadians.

Recent research suggests that urban greenness has important beneficial effects on health. While some epidemiological studies have investigated associations between measures of greenness and participation in physical activities, the findings have been inconsistent and several have relied on self-reported rather than objectively determined measures of greenness. Further, there have been few national studies. Our aim was to characterize associations between residential measures of greenness and physical activity within a nationally representative sample of Canadians. Moreover, we sought to determine to what extent these associations were modified by age, sex and income. Our analyses are based on data collected from participants of the 2001 Canadian Community Health Survey. Analyses were restricted to 69,910 individuals who were: 20 years of age and older, lived in urban areas, and for whom a residential measure of greenness could be assigned. The Normalised Difference Vegetation Index (NDVI), which is an objectively defined measure of greenness based on satellite imaging, was assigned to the residential addresses of the participants. Our NDVI values were based on 30 m and 500 m buffers from the centroid of the provided postal codes. Logistic regression was used to estimate odds ratios (ORs) and their 95% confidence intervals to describe associations between greenness and several measures of physical activity. The ORs were adjusted for age, sex, smoking status, marital status, and income. We found that participants who resided in the highest quartile of greenness, based on a 500 m buffer, were more likely to participate in leisure-time physical activity (adjusted OR=1.34, 95% CI=1.25-1.44) when compared to those in the lowest quartile. Positive associations were observed between greenness and physical activity in all income groupings. A key finding was the observation of a stronger association between greenness and measures of physical activity among younger adults, especially women. Our findings have important public health implications as they suggest that access to urban green environments contributes to increased participation in leisure-time physical activity which has demonstrable health benefits.

The contribution of neighbourhood material and social deprivation to survival: a 22-year follow-up of more than 500,000 Canadians.

BACKGROUND: We examined the incremental influence on survival of neighbourhood material and social deprivation while accounting for individual level socioeconomic status in a large population-based cohort of Canadians. METHODS: More than 500,000 adults were followed for 22 years between 1982 and 2004. Tax records provided information on sex, income, marital status and postal code while a linkage was used to determine vital status. Cox models were used to estimate hazard ratios (HR) for quintiles of neighbourhood material and social deprivation. RESULTS: There were 180,000 deaths over the follow-up period. In unadjusted analyses, those living in the most materially deprived neighbourhoods had elevated risks of mortality (HR(males) 1.37, 95% CI: 1.33-1.41; HR(females) 1.20, 95% CI: 1.16-1.24) when compared with those living in the least deprived neighbourhoods. Mortality risk was also elevated for those living in socially deprived neighbourhoods (HR(males) 1.15, CI: 1.12-1.18; HR(females) 1.15, CI: 1.12-1.19). Mortality risk associated with material deprivation remained elevated in models that adjusted for individual factors (HR(males) 1.20, CI: 1.17-1.24; HR(females) 1.16, CI: 1.13-1.20) and this was also the case for social deprivation (HR(males) 1.12, CI: 1.09-1.15; HR(females) 1.09, CI: 1.05-1.12). Immigrant neighbourhoods were protective of mortality risk for both sexes. Being poor and living in the most socially advantageous neighbourhoods translated into a survival gap of 10% over those in the most socially deprived neighbourhoods. The gap for material neighbourhood deprivation was 7%. CONCLUSIONS: Living in socially and materially deprived Canadian neighbourhoods was associated with elevated mortality risk while we noted a "healthy immigrant neighbourhood effect". For those with low family incomes, living in socially and materially deprived areas negatively affected survival beyond their individual circumstances.

Determinants of health-related quality of life of opiate users at entry to low-threshold methadone programs.

OBJECTIVE: The aim of this study was to conduct an exploratory analysis of factors associated with poor health-related quality of life (HRQOL) among opiate users at entry to low-threshold methadone treatment. METHODS: The SF-36 questionnaire was administered to 145 opiate users at enrollment into low-threshold methadone maintenance programs. ANOVA and correlational analyses were performed to investigate the determinants of poor physical and mental composite summary scales (PCS and MCS) of the SF-36 among opiate users. Stepwise regression methods were also employed to fit PCS and MCS multivariate models. RESULTS: Age, employment status, chronic medical conditions, hospitalization, emotional abuse, sexual abuse and age at first injection episode were significantly associated with PCS. Mental health problems, sexual abuse, physical abuse, the use of sedatives, the use of cocaine, the number of days of cocaine use, sedative use and multiple substance use in the past month were significantly associated with MCS. The variances in the MCS and PCS were not readily explained by any one factor. CONCLUSION: The multiplicity of factors influencing HRQOL of opiate users suggests the need for a range of services within the context of a methadone program, addressing primary medical care needs as well as treatment for both mental health problems and abuse issues.

A time-series study of air pollution, socioeconomic status, and mortality in Vancouver, Canada.

We evaluated the relationship between daily levels of particulate and gaseous phase pollutants and mortality within a dynamic cohort of approximately 550,000 individuals whose vital status was ascertained between 1986 and 1999. Time-series methods were applied to evaluate whether there were differential pollutant effects on daily aggregated numbers of deaths in the cohort that was stratified into quintiles of income as defined by the 1991 and 1996 Canadian censuses. The percent change in all-cause, cardiovascular, respiratory, and cancer daily mortality was calculated in relation to short-term changes in levels of a number of particulate (PM(2.5), PM(10-2.5), total suspended particle co-efficient of haze PM(10), SO(4)) and gaseous (O(3), CO, SO(2), NO(2)) pollutants. The estimated effects of air pollution on mortality were adjusted for day of week effects, and several meteorologic variables including temperature, change in barometric pressure, and relative humidity. Several gaseous pollutants were associated with an increased risk of mortality. Specifically for an increase equivalent to the difference between the 90th and 10th percentiles, the estimated percent change in daily mortality based on the 3-day average of NO(2), and SO(2) was 4.0% and 1.3%, respectively. The corresponding changes in mortality associated with SO(2) were much higher when analyses were restricted to death from respiratory disease. Specifically, a difference between the 90th and 10th percentiles was associated with a 5.6% (95% CI= -0.7% to 12.3%). The daily mean coarse fraction (PM(10-2.5)) was associated with increased cardiovascular mortality (estimated change=5.9%, 95% CI=1.1-10.8%). PM(2.5) was not found to be an important predictor of mortality. For NO(2), CO, and SO(2), there was some suggestion of increased risk of all-cause and cardiovascular mortality at lower levels of socioeconomic status. However, these results should be interpreted cautiously due to the small number of deaths observed within each stratum of socioeconomic status.

Screening for colorectal cancer using the fecal occult blood test: an actuarial assessment of the impact of a population-based screening program in Canada.

OBJECTIVES: A series of randomized controlled trials have demonstrated that screening for colorectal cancer (CRC) using the fecal occult blood (FOB) test can decrease mortality from this disease. These findings were used to develop an actuarial model to estimate the impact that a FOB screening program for colorectal cancer would have on the Canadian population. METHODS: The mortality experience of the year 2000 cohort of Canadians fifty to seventy-four years of age, with follow-up extending to 2010, was modelled according to three scenarios: no screening, annual screening, biennial screening. The primary screening tool was the FOB test using unrehydrated samples, with follow-up of positive test results using colonoscopy. The framework of the model was developed based on published findings from the relevant randomized controlled trials, available data, and a literature review that yielded parameter values for some model items. RESULTS: During the 10-year follow-up of the cohort, we estimated that 4,444 and 2,827 deaths would be averted with annual and biennial FOB screening, respectively. We estimated that for an annual FOB screening program, approximately 3,400 FOB tests would be required to prevent one death, whereas 2,700 tests would be required within a biennial program. CONCLUSIONS: Our analysis documents the population health impact of using the FOB test to screen for CRC. Additional information on the natural history of the disease, and Canadian pilot data are needed to better model the effectiveness of population-based FOB screening programs.