Inequality in the Distribution of Air Pollution Attributable Mortality Within Canadian Cities.

Recent studies have identified inequality in the distribution of air pollution attributable health impacts, but to our knowledge this has not been examined in Canadian cities. We evaluated the extent and sources of inequality in air pollution attributable mortality at the census tract (CT) level in seven of Canada's largest cities. We first regressed fine particulate matter (PM2.5) and nitrogen dioxide (NO2) attributable mortality against the neighborhood (CT) level prevalence of age 65 and older, low income, low educational attainment, and identification as an Indigenous (First Nations, Métis, Inuit) or Black person, accounting for spatial autocorrelation. We next examined the distribution of baseline mortality rates, PM2.5 and NO2 concentrations, and attributable mortality by neighborhood (CT) level prevalence of these characteristics, calculating the concentration index, Atkinson index, and Gini coefficient. Finally, we conducted a counterfactual analysis of the impact of reducing baseline mortality rates and air pollution concentrations on inequality in air pollution attributable mortality. Regression results indicated that CTs with a higher prevalence of low income and Indigenous identity had significantly higher air pollution attributable mortality. Concentration index, Atkinson index, and Gini coefficient values revealed different degrees of inequality among the cities. Counterfactual analysis indicated that inequality in air pollution attributable mortality tended to be driven more by baseline mortality inequalities than exposure inequalities. Reducing inequality in air pollution attributable mortality requires reducing disparities in both baseline mortality and air pollution exposure.

Health impact analysis of PM2.5 from wildfire smoke in Canada (2013-2015, 2017-2018).

Smoke from wildfires contains many air pollutants of concern and epidemiological studies have identified associations between exposure to wildfire smoke PM2.5 and mortality and respiratory morbidity, and a possible association with cardiovascular morbidity. For this study, a retrospective analysis of air quality modelling was performed to quantify the exposure to wildfire-PM2.5 across the Canadian population. The model included wildfire emissions from across North America for a 5-month period from May to September (i.e. wildfire season), between 2013 and 2015 and 2017-2018. Large variations in wildfire-PM2.5 were noted year-to-year, geospatially, and within fire season. The model results were then used to estimate the national population health impacts attributable to wildfire-PM2.5 and the associated economic valuation. The analysis estimated annual premature mortalities ranging from 54-240 premature mortalities attributable to short-term exposure and 570-2500 premature mortalities attributable to long-term exposure, as well as many non-fatal cardiorespiratory health outcomes. The economic valuation of the population health impacts was estimated per year at $410M-$1.8B for acute health impacts and $4.3B-$19B for chronic health impacts for the study period. The health impacts were greatest in the provinces with populations in close proximity to wildfire activity, though health impacts were also noted across many provinces indicating the long-range transport of wildfire-PM2.5. Understanding the population health impacts of wildfire smoke is important as climate change is anticipated to increase wildfire activity in Canada and abroad.

Reassessment of deferrals for tattooing and piercing.

BACKGROUND: In August 2005, the Canadian Blood Services decreased the deferral period for tattooing and ear or body piercing from 12 to 6 months. This study assessed the impact of this change on blood safety and availability. STUDY DESIGN AND METHODS: The prevalence of these activities was assessed on an anonymous mail-out survey of 40,000 recent donors. Transmissible disease (TD) marker rates were calculated using the National Epidemiology Donor Database. A case-control study was performed comparing risk factors in TD-positive donors with matched controls. Donor deferral rates were assessed before and after the change in deferral period. RESULTS: The prevalence rates of tattoo, ear piercing, and body piercing were 13.7, 53.6, and 10.4 percent in survey respondents, respectively, with up to 0.7 percent of activity likely to represent deferrable risk. TD marker rate was low and stable at 21.6 per 100,000 donations before and 19.2 per 100,000 donations after the change in deferral length. Remote tattoo was associated with hepatitis C virus (HCV) risk (odds ratio, 5.43; 95% confidence interval, 1.82-16.2), but neither recent tattoo nor piercing was a risk factor for HCV or hepatitis B virus. Shortening of the deferral period reduced deferrals by 20 percent for tattoo and 32 percent for piercing. CONCLUSION: There was no measurable adverse effect on safety and a positive but less than expected effect on blood availability after shortening the deferral period for tattoo and piercing. The length of other temporary deferrals should be reassessed, since their current contribution to blood safety may be negligible.

Epidemiology of hepatitis B in Canadian blood donors.

BACKGROUND: The residual risk of hepatitis B is higher than for other markers such as human immunodeficiency virus and hepatitis C virus in nonendemic countries. Evaluating the potential for further risk reduction requires a better understanding of the relationship between donor selection criteria, immigration from endemic countries, and public health vaccination strategies. STUDY DESIGN AND METHODS: Age and sex trends of hepatitis B surface antigen (HBsAg)-positive donors from 1997 to 2006 were analyzed using a Poisson model. All HBsAg-positive donors in 2005/2006 plus four matched control donors for every HBsAg-positive donor who participated were invited to participate in a risk factor interview and predictors of HBsAg positivity identified by logistic regression. A survey of 40,000 donors who did not react for all markers asked about vaccination history and country of birth. RESULTS: Most HBsAg-positive donations were from first-time donors (86%), have been decreasing in donors under the age of 30 (p < 0.01), and were correlated with geographic regions with more donors from higher-prevalence countries (p < 0001). Birth in a higher-prevalence country predicted HBsAg positivity (p < 0.01). Fifty-six percent of donors reported being vaccinated for hepatitis including approximately 80 percent of donors under age 30 who reported being vaccinated as part of regular school programs. CONCLUSION: HBsAg-positive donations are decreasing in donors under age 30, those most frequently vaccinated through provincial vaccination programs. HBsAg-positive donations largely reflect immigration from high-prevalence countries without other deferrable risk factors, mainly chronic cases that will be detected by current testing. Furthermore, risk of incident infections should decrease with increasing vaccination rates in donors, especially the younger cohort now receiving universal vaccination.

Declining hepatitis C rates in first-time blood donors: insight from surveillance and case-control risk factor studies.

BACKGROUND: Hepatitis C virus (HCV) rates have decreased steadily in first-time donors in Canada since testing was implemented but reasons are unclear. A description of factors that may have played a role in this decline is reported. STUDY DESIGN AND METHODS: Descriptive analysis of first-time blood donors by HCV positivity status and year (1993--2006), sex, and age was carried out. HCV-positive first-time donors and matched controls participated in a confidential scripted telephone interview about risk factors in 1993 through 1994 and in 2005 through 2006, and risk factors independently predicting HCV positivity were determined with multiple logistic regression. RESULTS: HCV-positive donations occurred most frequently in donors born between 1945 and 1964 and decreased in this birth cohort over time (p < 0.01). At present, most first-time donors (74%) are born after 1964. History of intravenous drug use, sex with an intravenous drug user, blood transfusion, and tattoo independently predicted (p < 0.01) HCV positivity in both periods (1993--1994 and 2005--2006). CONCLUSION: Most HCV-positive donors were born between 1945 and 1964, and the decline in HCV rates is associated primarily with this birth cohort. The key risk factors predicting HCV positivity did not change over the 13 years of the study. With approximately two-thirds of HCV-positive Canadians in the general population having been tested for HCV, potential donors may be aware of their HCV status and be likely to self-defer. This, and an increasing proportion of first-time donors born after 1964, may contribute to declining HCV rates in first-time donors.

Assessment of a travel question to identify donors with risk of Trypanosoma cruzi: operational validity and field testing.

BACKGROUND: Because Trypanosoma cruzi (T. cruzi) infection in Canada and the United States is largely contracted in endemic countries, targeted testing of blood donors with risk travel may improve safety. The operational validity of a travel question suitable for donor screening was tested, and it was field-tested. STUDY DESIGN AND METHODS: After 1331 donors completed a short travel question, operational validity was assessed by detailed travel histories in face-to-face interviews. Two nationwide donor surveys were carried out assessing donor responses to similar travel questions in 2001 (13,623 donors) and in 2006 (20,037 donors). All donors in Toronto, Ontario, answered a travel question in 1997 and those born in or who spent 6 months or more in Mexico, Central America, or South America were tested for antibody to T. cruzi. RESULTS: There was 97.3 percent agreement between the travel question and detailed interviews, with 15 donors (1.1%) failing to acknowledge risk travel (false-negative questioning responses). Of these, 6 donors were born there and 7 others had less than 1 year of cumulative travel. In 2001 and 2006, there were 2.1 and 2.0 percent of donors with risk travel, respectively, but 16.5 and 11.2 percent of these donors were identified only because they were born there (travel not acknowledge). There were 1337 (1.6%) donors in Toronto in 1997 with risk travel and none were positive for the presence of T. cruzi antibody. CONCLUSION: Donors can answer a short question about cumulative time in Latin America with similar accuracy to detailed questioning, but screening questions should also include country of birth.

Mapping the connections between education and dementia.

Explanations for the association between educational attainment and the risk of dementia fall into three main categories. It may arise as an artefact of study methods; education may predict broader socioeconomic circumstances and exposures, or education may reflect brain reserve or cognitive capacity that protect against dementia. Data from the Canadian Study of Health and Aging (N=6646, giving 44,676 person-years of follow-up) are analyzed to test a series of hypotheses reflecting these explanations. Years of education showed a strong association with the risk of dementia (relative risk [RR] 2.1 for those with less than 6 years of education compared to those with 13 or more years; RR=2.9 among survivors). Possible artefactual factors were detected, but were insufficient to invalidate the association. Adjustments for a range of other socioeconomic indicators, health problems and lifestyle factors reduced, but did not remove, the association. Adjustments for intelligence and for an indicator of lifetime mental activity also appeared to account for some but not all of the association. The conclusion is that there appears to be a real association between educational attainment and the risk of dementia 50 to 60 years later; this influence appears to run through a number of different, and sometimes complementary, pathways.

Income inequality and health in Ontario: a multilevel analysis.

OBJECTIVE: To examine the association of income inequality at the public health unit level with individual health status in Ontario. METHODS: Cross-sectional multilevel study carried out among subjects aged 25 years or older residing in 42 public health units in Ontario. Individual-level data drawn from 30,939 respondents in 1996-97 Ontario Health Survey. Median area income and income inequality (Gini coefficient) calculated from 1996 census. Self-rated health status (SRH) and Health Utilities Index (HUI-3) scores were used as main outcomes. RESULTS: Controlling for individual-level factors including income, respondents living in public health units in the highest tercile of income inequality had odds ratios of 1.20 (95% CI 1.04 - 1.38) for fair/poor self-rated health, and 1.11 (95% CI 1.01 - 1.22) for HUI score below the median, compared with people living in public health units in the lowest tercile. Controlling further for median area income had little effect on the association. CONCLUSION: Income inequality was significantly associated with individual self-reported health status at public health unit level in Ontario, independent of individual income.