Future temperature-related excess mortality under climate change and population aging scenarios in Canada.

OBJECTIVE: Climate change is expected to increase global temperatures. How temperature-related mortality risk will change is not completely understood, and how future demographic changes will affect temperature-related mortality needs to be clarified. We evaluate temperature-related mortality across Canada until 2099, accounting for age groups and scenarios of population growth. METHODS: We used daily counts of non-accidental mortality for 2000 to 2015 for all 111 health regions across Canada, incorporating in the study both urban and rural areas. A two-part time series analysis was used to estimate associations between mean daily temperatures and mortality. First, current and future daily mean temperature time series simulations were developed from Coupled Model Inter-Comparison Project 6 (CMIP6) climate model ensembles from past and projected climate change scenarios under Shared Socioeconomic Pathways (SSPs). Next, excess mortality due to heat and cold and the net difference were projected to 2099, also accounting for different regional and population aging scenarios. RESULTS: For 2000 to 2015, we identified 3,343,311 non-accidental deaths. On average, a net increase of 17.31% (95% eCI: 13.99, 20.62) in temperature-related excess mortality under a higher greenhouse gas emission scenario is expected for Canada in 2090-2099, which represents a greater burden than a scenario that assumed strong levels of greenhouse gas mitigation policies (net increase of 3.29%; 95% eCI: 1.41, 5.17). The highest net increase was observed among people aged 65 and over, and the largest increases in both net and heat- and cold-related mortality were observed in population scenarios that incorporated the highest rates of aging. CONCLUSION: Canada may expect net increases in temperature-related mortality under a higher emissions climate change scenario, compared to one assuming sustainable development. Urgent action is needed to mitigate future climate change impacts.

RéSUMé: OBJECTIF: Les changements climatiques devraient accroître les températures mondiales. La façon dont le risque de mortalité lié à la température évoluera n'est pas entièrement comprise, et la façon dont les changements démographiques futurs influeront sur la mortalité liée à la température doit être clarifiée. Nous étudions la mortalité liée à la température au Canada jusqu'en 2099, en tenant compte des groupes d'âge et des scénarios de croissance démographique. MéTHODES: Nous avons utilisé les nombres quotidiens de mortalité non accidentelle pour 2000 à 2015 pour toutes les 111 régions socio sanitaires du Canada, en intégrant dans l'étude des régions urbaines et rurales. Une analyse en séries chronologiques en deux parties a été utilisée pour estimer les associations entre les températures quotidiennes moyennes et la mortalité. Premièrement, des simulations de séries chronologiques de températures moyennes quotidiennes actuelles et futures ont été élaborées à partir d'ensembles de modèles climatiques du Projet de comparaison croisée 6 (CMIP6) du modèle couplé à partir de scénarios de changements climatiques passés et projetés dans le cadre de voies socioéconomiques partagées (SSP). Ensuite, la surmortalité due à la chaleur et au froid et la différence nette ont été projetées jusqu'en 2099, ce qui tient également compte de différents scénarios régionaux et de vieillissement de la population. RéSULTATS: De 2000 à 2015, nous avons recensé 3 343 311 décès non accidentels. En moyenne, une augmentation nette de 17,31% (eCI à 95%: 13,99, 20,62) de la mortalité excessive liée à la température dans le cadre d'un scénario d'émissions de gaz à effet de serre plus élevées est prévue pour le Canada en 2090­2099, ce qui représente un fardeau plus lourd qu'un scénario qui suppose des niveaux élevés de politiques d'atténuation des émissions de gaz (augmentation nette de 3,29%; eCI à 95%: 1,41, 5,17). La plus forte augmentation nette a été observée chez les personnes de 65 ans ou plus, et les plus fortes augmentations de la mortalité nette, de mortalité liée à la chaleur et au froid ont été observées dans les scénarios de population qui comprenaient les taux de vieillissement les plus élevés. CONCLUSION: Le Canada pourrait s'attendre à des augmentations nettes de la mortalité liée à la température dans le cadre d'un scénario de changement climatique à émissions plus élevées, comparativement à un scénario de développement durable. Des mesures urgentes sont nécessaires pour atténuer les répercussions futures des changements climatiques.

The effect modification of extreme temperatures on mental and behavior disorders by environmental factors and individual-level characteristics in Canada.

OBJECTIVE: Ambient extreme temperatures have been associated with mental and behavior disorders (MBDs). However, few studies have assesed whether vulnerability factors such as ambient air pollution, pre-existing mental health conditions and residential environmental factors increase susceptibility. This study aims to evaluate the associations between short-term variations in outdoor ambient extreme temperatures and MBD-related emergency department (ED) visits and how these associations are modified by vulnerability factors. METHODS: We conducted a case-crossover study of 9,958,759 MBD ED visits in Alberta and Ontario, Canada made between March 1st, 2004 and December 31st, 2020. Daily average temperature was assigned to individual cases with ED visits for MBD using gridded data at a 1 km × 1 km spatial resolution. Conditional logistic regression was used to estimate associations between extreme temperatures (i.e., risk of ED visit at the 2.5th percentile temperature for cold and 97.5th percentile temperature for heat for each health region compared to the minimal temperature risk) and MBD ED visits. Age, sex, pre-existing mental health conditions, ambient air pollution (i.e. PM2.5, NO2 and O3) and residential environmental factors (neighborhood deprivation, residential green space exposure and urbanization) were evaluated as potential effect modifiers. RESULTS: Cumulative exposure to extreme heat over 0-5 days (odds ratio [OR] = 1.145; 95% CI: 1.121-1.171) was associated with ED visits for any MBD. However, cumulative exposure to extreme cold was associated with lower risk of ED visits for any MBD (OR = 0.981; 95% CI: 0.976-0.987). We also found heat to be associated with ED visits for specific MBDs such as substance use disorders, dementia, neurotic disorders, schizophrenia and personality behavior disorder. Individuals with pre-existing mental health conditions, those exposed to higher daily concentrations of NO2 and O3 and those residing in neighborhoods with greater material and social deprivation were at higher risk of heat-related MBD ED visits. Increasing tree canopy coverage appeared to mitigate risks of the effect of heat on MBD ED visits. CONCLUSIONS: Findings provide evidence that the impacts of heat on MBD ED visits may vary across different vulnerability factors.

The modifying effect of socioeconomic status on the relationship between traffic, air pollution and respiratory health in elementary schoolchildren.

The volume and type of traffic and exposure to air pollution have been found to be associated with respiratory health, but few studies have considered the interaction with socioeconomic status at the household level. We investigated the relationships of respiratory health related to traffic type, traffic volume, and air pollution, stratifying by socioeconomic status, based on household income and education, in 3591 schoolchildren in Windsor, Canada. Interquartile range changes in traffic exposure and pollutant levels were linked to respiratory symptoms and objective measures of lung function using generalised linear models for three levels of income and education. In 95% of the relationships among all cases, the odds ratios for reported respiratory symptoms (a decrease in measured lung function), based on an interquartile range change in traffic exposure or pollutant, were greater in the lower income/education groups than the higher, although the odds ratios were in most cases not significant. However, in up to 62% of the cases, the differences between high and low socioeconomic groups were statistically significant, thus indicating socioeconomic status (SES) as a significant effect modifier. Our findings indicate that children from lower socioeconomic households have a higher risk of specific respiratory health problems (chest congestion, wheezing) due to traffic volume and air pollution exposure.

Synoptic weather types and aeroallergens modify the effect of air pollution on hospitalisations for asthma hospitalisations in Canadian cities.

Pollution levels and the effect of air pollution on human health can be modified by synoptic weather type and aeroallergens. We investigated the effect modification of aeroallergens on the association between CO, O3, NO2, SO2, PM10, PM2.5 and asthma hospitalisation rates in seven synoptic weather types. We developed single air pollutant models, adjusted for the effect of aeroallergens and stratified by synoptic weather type, and pooled relative risk estimates for asthma hospitalisation in ten Canadian cities. Aeroallergens significantly modified the relative risk in 19 pollutant-weather type combinations, reducing the size and variance for each single pollutant model. However, aeroallergens did not significantly modify relative risk for any pollutant in the DT or MT weather types, or for PM10 in any weather type. Thus, there is a modifying effect of aeroallergens on the association between CO, O3, NO2, SO2, PM2.5 and asthma hospitalisations that differs under specific synoptic weather types.

Residential exposure to volatile organic compounds and lung function: results from a population-based cross-sectional survey.

Exposure to residential volatile organic compounds (VOCs) is ubiquitous in homes, and may influence respiratory health with important public health implications. To investigate the association between VOCs measured in residential indoor air and lung function in the Canadian population Cycle 2 of the Canadian Health Measures Survey - a population based cross-sectional survey designed to be representative of the Canadian population - was carried out between 2009 and 2011. Of the 84 VOCs measured, 47 were detectable in at least 50% of homes and ten were negatively associated with lung function: decanal, 2-furancarboxaldehyde, hexanal, nonanal, octanal, benzene, styrene, α-pinene, 2-methyl-1,2-butadiene and naphthalene. Differences were observed between males and females, as well as by age, and significant associations were most frequent in those under 17 years. These results provide evidence that some VOCs measured indoors are negatively associated with lung function in the Canadian population.

Risk assessment for cardiovascular and respiratory mortality due to air pollution and synoptic meteorology in 10 Canadian cities.

Synoptic weather and ambient air quality synergistically influence human health. We report the relative risk of mortality from all non-accidental, respiratory-, and cardiovascular-related causes, associated with exposure to four air pollutants, by weather type and season, in 10 major Canadian cities for 1981 through 1999. We conducted this multi-city time-series study using Poisson generalized linear models stratified by season and each of six distinctive synoptic weather types. Statistically significant relationships of mortality due to short-term exposure to carbon monoxide, nitrogen dioxide, sulphur dioxide, and ozone were found, with significant modifications of risk by weather type, season, and mortality cause. In total, 61% of the respiratory-related mortality relative risk estimates were significantly higher than for cardiovascular-related mortality. The combined effect of weather and air pollution is greatest when tropical-type weather is present in the spring or summer.

Climate change and future temperature-related mortality in 15 Canadian cities.

The environmental changes caused by climate change represent a significant challenge to human societies. One part of this challenge will be greater heat-related mortality. Populations in the northern hemisphere will experience temperature increases exceeding the global average, but whether this will increase or decrease total temperature-related mortality burdens is debated. Here, we use distributed lag modeling to characterize temperature-mortality relationships in 15 Canadian cities. Further, we examine historical trends in temperature variation across Canada. We then develop city-specific general linear models to estimate change in high- and low-temperature-related mortality using dynamically downscaled climate projections for four future periods centred on 2040, 2060 and 2080. We find that the minimum mortality temperature is frequently located at approximately the 75th percentile of the city's temperature distribution, and that Canadians currently experience greater and longer lasting risk from cold-related than heat-related mortality. Additionally, we find no evidence that temperature variation is increasing in Canada. However, the projected increased temperatures are sufficient to change the relative levels of heat- and cold-related mortality in some cities. While most temperature-related mortality will continue to be cold-related, our models predict that higher temperatures will increase the burden of annual temperature-related mortality in Hamilton, London, Montreal and Regina, but result in slight to moderate decreases in the burden of mortality in the other 11 cities investigated.

Manganese deficiency leads to genotype-specific changes in fluorescence induction kinetics and state transitions.

Barley (Hordeum vulgare) genotypes display a marked difference in their ability to tolerate growth at low manganese (Mn) concentrations, a phenomenon designated as differential Mn efficiency. Induction of Mn deficiency in two genotypes differing in Mn efficiency led to a decline in the quantum yield efficiency for both, although faster in the Mn-inefficient genotype. Leaf tissue and thylakoid Mn concentrations were reduced under Mn deficiency, but no difference between genotypes was observed and no visual Mn deficiency symptoms were developed. Analysis of the fluorescence induction kinetics revealed that in addition to the usual O-J-I-P steps, clear K and D steps were developed in the Mn-inefficient genotype under Mn deficiency. These marked changes indicated damages to photosystem II (PSII). This was further substantiated by state transition measurements, indicating that the ability of plants to redistribute excitation energy was reduced. The percentage change in state transitions for control plants with normal Mn supply of both genotypes was 9% to 11%. However, in Mn-deficient leaves of the Mn-inefficient genotypes, state transitions were reduced to less than 1%, whereas no change was observed for the Mn-efficient genotypes. Immunoblotting and the chlorophyll a/b ratio confirmed that Mn deficiency in general resulted in a significant reduction in abundance of PSII reaction centers relative to the peripheral antenna. In addition, PSII appeared to be significantly more affected by Mn limitation than PSI. However, the striking genotypic differences observed in Mn-deficient plants, when analyzing state transitions and fluorescence induction kinetics, could not be correlated with specific changes in photosystem proteins. Thus, there is no simple linkage between protein expression and the differential reduction in state transition and fluorescence induction kinetics observed for the genotypes under Mn deficiency.

Latent manganese deficiency increases transpiration in barley (Hordeum vulgare).

To investigate if latent manganese (Mn) deficiency leads to increased transpiration, barley plants were grown for 10 weeks in hydroponics with daily additions of Mn in the low nM range. The Mn-starved plants did not exhibit visual leaf symptoms of Mn deficiency, but Chl a fluorescence measurements revealed that the quantum yield efficiency of PSII (F(v)/F(m)) was reduced from 0.83 in Mn-sufficient control plants to below 0.5 in Mn-starved plants. Leaf Mn concentrations declined from 30 to 7 microg Mn g(-1) dry weight in control and Mn-starved plants, respectively. Mn-starved plants had up to four-fold higher transpiration than control plants. Stomatal closure and opening upon light/dark transitions took place at the same rate in both Mn treatments, but the nocturnal leaf conductance for water vapour was still twice as high in Mn-starved plants compared with the control. The observed increase in transpiration was substantiated by (13)C-isotope discrimination analysis and gravimetric measurement of the water consumption, showing significantly lower water use efficiency in Mn-starved plants. The extractable wax content of leaves of Mn-starved plants was approximately 40% lower than that in control plants, and it is concluded that the increased leaf conductance and higher transpirational water loss are correlated with a reduction in the epicuticular wax layer under Mn deficiency.

Differential capacity for high-affinity manganese uptake contributes to differences between barley genotypes in tolerance to low manganese availability.

There is considerable variability among barley (Hordeum vulgare) genotypes in their ability to grow in soils containing a low level of plant available manganese (Mn). The physiological basis for the tolerance to low Mn availability is unknown. In this work, Mn2+ influx and compartmentation in roots of the Mn-efficient genotype Vanessa and the Mn-inefficient genotype Antonia were investigated. Two separate Mn transport systems, mediating high-affinity Mn2+ influx at concentrations up to 130 nm and low-affinity Mn2+ influx at higher concentrations, were identified in both genotypes. The two genotypes differed only in high-affinity kinetics with the Mn-efficient genotype Vanessa having almost 4 times higher V(max) than the inefficient Antonia, but similar K(m) values. Online inductively coupled plasma-mass spectrometry measurements verified that the observed differences in high-affinity influx resulted in a higher Mn net uptake of Vanessa compared to Antonia. Further evidence for the importance of the differences in high-affinity uptake kinetics for Mn acquisition was obtained in a hydroponic system with mixed cultivation of the two genotypes at a continuously low Mn concentration (10-50 nm) similar to that occurring in soil solution. Under these conditions, Vanessa had a competitive advantage and contained 55% to 75% more Mn in the shoots than did Antonia. Subcellular compartmentation analysis of roots based on 54Mn2+ efflux established that up to 93% and 83% of all Mn was present in the vacuole in Vanessa and Antonia, respectively. It is concluded that differential capacity for high-affinity Mn influx contributes to differences between barley genotypes in Mn efficiency.