Associations between air pollution and cardio-respiratory physiological measures in older adults exercising outdoors

We examined whether exercising indoors vs. outdoors reduced the cardio-respiratory effects of outdoor air pollution. Adults ≥55 were randomly assigned to exercise indoors when the Air Quality Health Index was ≥5 and outdoors on other days (intervention group, n = 37), or outdoors everyday (control group, n = 35). Both groups completed cardio-respiratory measurements before and after exercise for up to 10 weeks. Data were analyzed using linear mixed effect regression models. In the control group, an interquartile range increase in fine particulate matter (PM_2.5) was associated with increases of 1.4% in heart rate (standard error (SE) = 0.7%) and 5.6% (SE = 2.6%) in malondialdehyde, and decreases of 5.6% (SE = 2.5%) to 16.5% (SE = 7.5%) in heart rate variability measures. While the hypothesized benefit of indoor vs. outdoor exercise could not be demonstrated due to an insufficient number of intervention days (n = 2), the study provides evidence of short-term effects of air pollution in older adults. ISRCTN #26552763.

Accuracy of quantification of risk using a single-pollutant Air Quality Index

Health risks associated with short-term exposure to ambient air pollution are communicated to the public by the US EPA through the Air Quality Index (AQI), but it remains unclear whether the current regulatory-based, single-pollutant AQI fully represents the actual risks of air pollution-related illness. The objective of this study is to quantify cardiovascular hospital admissions attributable to PM_2.5 at each AQI category. Based on National Ambient Air Quality Standards (NAAQS), the highest AQI value among criteria pollutants (driver pollutant) is reported daily. We investigated excess cardiovascular hospital admissions attributable to fine particulate matter (PM_2.5) exposure from 2000 to 2010 in Bronx, Erie, Queens, and Suffolk counties of New York. Daily total, unscheduled cardiovascular hospital admissions (principal diagnosis) for individuals aged 20-99 years, concentration-response functions for PM_2.5, and estimated quarterly effective daily concentrations were used to calculate excess cardiovascular hospital admissions when PM_2.5 was reported as the driver pollutant and when PM_2.5 was not reported as the driver pollutant at each AQI category. A higher proportion of excess hospital admissions attributable to PM_2.5 occurred when PM_2.5 was the driver pollutant (i.e., ~70% in Bronx County). The majority of excess hospital admissions (i.e., >90% in Bronx County) occurred when the AQI was <100 ("good" or "moderate" level of health concern) regardless of whether PM_2.5 was the driver pollutant. During the warm season (April-September), greater excess admissions in Suffolk County occurred when PM_2.5 was not the AQI driver pollutant. These results indicate that a single-pollutant index may inadequately communicate the adverse health risks associated with air pollution.

A class of non-linear exposure-response models suitable for health impact assessment applicable to large cohort studies of ambient air pollution

The effectiveness of regulatory actions designed to improve air quality is often assessed by predicting changes in public health resulting from their implementation. Risk of premature mortality from long-term exposure to ambient air pollution is the single most important contributor to such assessments and is estimated from observational studies generally assuming a log-linear, no-threshold association between ambient concentrations and death. There has been only limited assessment of this assumption in part because of a lack of methods to estimate the shape of the exposure-response function in very large study populations. In this paper, we propose a new class of variable coefficient risk functions capable of capturing a variety of potentially non-linear associations which are suitable for health impact assessment. We construct the class by defining transformations of concentration as the product of either a linear or log-linear function of concentration multiplied by a logistic weighting function. These risk functions can be estimated using hazard regression survival models with currently available computer software and can accommodate large population-based cohorts which are increasingly being used for this purpose. We illustrate our modeling approach with two large cohort studies of long-term concentrations of ambient air pollution and mortality: the American Cancer Society Cancer Prevention Study II (CPS II) cohort and the Canadian Census Health and Environment Cohort (CanCHEC). We then estimate the number of deaths attributable to changes in fine particulate matter concentrations over the 2000 to 2010 time period in both Canada and the USA using both linear and non-linear hazard function models.

Spatial analysis of exposure to traffic-related air pollution at birth and childhood atopic asthma in Toronto, Ontario

Findings from the Toronto Child Health Evaluation Questionnaire (TCHEQ) study indicate that early childhood exposure to traffic-related air pollution (TRAP) is related to the onset of atopic childhood asthma. To test this hypothesis further, we investigated whether spatial patterns in the birth neighbourhood of TCHEQ subjects with atopic asthma (136 of 909 schoolchildren in grades 1-2) could be explained by TRAP and other risk factors. If a causal relationship exists between early childhood residential exposure to TRAP and the development of atopic asthma, we hypothesise that (1) clusters of current asthma should exist around the place of residence at birth, and (2) accounting for residential concentrations of TRAP at birth should explain some of the autocorrelation. Several high asthma clusters were observed. Adjusting for TRAP completely explained one cluster; elsewhere, clusters were only partially explained by TRAP. Findings suggest that exposure during early childhood to TRAP in Toronto is an important contributor to the development of the atopic asthma phenotype and reveal the likely importance of other risk factors not measured in the fixed effects of the model.

Risk of nonaccidental and cardiovascular mortality in relation to long-term exposure to low concentrations of fine particulate matter: a Canadian national-level cohort study

BACKGROUND

Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM(2.5))]. This is the first national-level cohort study to investigate these risks in Canada.

OBJECTIVE

We investigated the association between long-term exposure to ambient PM(2.5) and cardiovascular mortality in nonimmigrant Canadian adults.

METHODS

We assigned estimates of exposure to ambient PM(2.5) derived from satellite observations to a cohort of 2.1 million Canadian adults who in 1991 were among the 20% of the population mandated to provide detailed census data. We identified deaths occurring between 1991 and 2001 through record linkage. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for available individual-level and contextual covariates using both standard Cox proportional survival models and nested, spatial random-effects survival models.

RESULTS

Using standard Cox models, we calculated HRs of 1.15 (95% CI: 1.13, 1.16) from nonaccidental causes and 1.31 (95% CI: 1.27, 1.35) from ischemic heart disease for each 10-μg/m(3) increase in concentrations of PM(2.5). Using spatial random-effects models controlling for the same variables, we calculated HRs of 1.10 (95% CI: 1.05, 1.15) and 1.30 (95% CI: 1.18, 1.43), respectively. We found similar associations between nonaccidental mortality and PM2.5 based on satellite-derived estimates and ground-based measurements in a subanalysis of subjects in 11 cities.

CONCLUSIONS

In this large national cohort of nonimmigrant Canadians, mortality was associated with long-term exposure to PM(2.5). Associations were observed with exposures to PM(2.5) at concentrations that were predominantly lower (mean, 8.7 μg/m(3); interquartile range, 6.2 μg/m(3)) than those reported previously.

The association between chronic exposure to traffic-related air pollution and ischemic heart disease

Increasing evidence links air pollution to the risk of cardiovascular disease. This study investigated the association between ischemic heart disease (IHD) prevalence and exposure to traffic-related air pollution (nitrogen dioxide [NO₂], fine particulate matter [PM₂.₅], and ozone [O₃]) in a population of susceptible subjects in Toronto. Local (NO₂) exposures were modeled using land use regression based on extensive field monitoring. Regional exposures (PM₂.₅, O₃) were modeled as confounders using inverse distance weighted interpolation based on government monitoring data. The study sample consisted of 2360 patients referred during 1992 to 1999 to a pulmonary clinic at the Toronto Western Hospital in Toronto, Ontario, Canada, to diagnose or manage a respiratory complaint. IHD status was determined by clinical database linkages (ICD-9-CM 412-414). The association between IHD and air pollutants was assessed with a modified Poisson regression resulting in relative risk estimates. Confounding was controlled with individual and neighborhood-level covariates. After adjusting for multiple covariates, NO₂ was significantly associated with increased IHD risk, relative risk (RR) = 1.33 (95% confidence interval [CI]: 1.2, 1.47). Subjects living near major roads and highways had a trend toward an elevated risk of IHD, RR = 1.08 (95% CI: 0.99, 1.18). Regional PM₂.₅ and O₃ were not associated with risk of IHD.

Is outdoor air pollution associated with physician visits for allergic rhinitis among the elderly in Toronto, Canada?

BACKGROUND

While a number of studies suggest that air pollution is associated with allergic rhinitis in children, findings among adults have been equivocal. The aim of this study was to examine the relationship between outdoor air pollution and physician visits for allergic rhinitis among individuals>or=65 years of age in Toronto, Canada.

METHODS

Physician visits were identified by using data from the Ontario provincial health insurance plan that is made available to all residents. Our analyses are based on 52,691 physician visits for allergic rhinitis among individuals>or=65 years of age in the Toronto metropolitan area between 1995 and 2000. Generalized linear models were used to regress daily counts of physician visits against daily measures of gaseous and particulate components of air pollution after controlling for seasonality, potential confounders (temperature, relative humidity, aeroallergens), overdispersion and serial correlation.

RESULTS

A large number of comparisons were undertaken, with most showing no statistically significant associations between daily levels of air pollution and the number of physician visits for rhinitis. In contrast, an interquartile increase in the 10-day average of ragweed particles increased the mean number of daily rhinitis consultations by 6.4% (95% CI=0.7-12.4%).

CONCLUSIONS

Our findings suggest that outdoor air pollution is a poor predictor of physician visits for allergic rhinitis among the elderly.

Weather and emergency room visits for migraine headaches in Ottawa, Canada

BACKGROUND

Self-reported surveys have indicated that weather can trigger migraine headaches. However, to date, we know of no previous study that has examined the relationship between weather and emergency room (ER) visits for this condition.

OBJECTIVE

To examine associations between ER visits for migraines and selected meteorological conditions within the 24 hours preceding the visit.

DESIGN AND METHODS

A case-crossover design was used to study 4039 visits for migraines (ICD-9: 346) that occurred at an Ottawa hospital between 1993 and 2000. Meteorological conditions were defined using hourly readings from a fixed-site monitoring station. Conditional logistic regression was used to compare the occurrence of meteorological conditions during the 24 hours leading up to the time of the visit to control periods occurring 1 week before and after.

RESULTS

Precipitation-related weather events (fog, snow, rain, thunder) were not associated with migraine visits. Similarly, no associations were observed with changes in atmospheric pressure, wind speed, and relative humidity during the 24 hours preceding presentation. No statistically significant differences in the frequency distribution of clusters defined by relative humidity, atmospheric pressure, and temperature were found between case and control intervals. Conversely, a mean wind speed in excess of 19 km per hour was associated with a reduction in ER visits 8 to 12 hours later.

CONCLUSIONS

Our findings provide little support for the hypothesis that ER visits for migraines are related to weather conditions occurring within the 24 hours preceding presentation. These results should be interpreted cautiously as some comparisons are based on a small number of cases, and ER visits for migraine may represent a highly selective group of patients who suffer from this condition.

The association between low level exposures to ambient air pollution and term low birth weight: a retrospective cohort study

BACKGROUND

Studies in areas with relatively high levels of air pollution have found some positive associations between exposures to ambient levels of air pollution and several birth outcomes including low birth weight (LBW). The purpose of this study was to examine the association between LBW among term infants and ambient air pollution, by trimester of exposure, in a region of lower level exposures.

METHODS

The relationship between LBW and ambient levels of particulate matter up to 10 um in diameter (PM10), sulfur dioxide (SO2) and ground-level ozone (O3) was evaluated using the Nova Scotia Atlee Perinatal Database and ambient air monitoring data from the Environment Canada National Air Pollution Surveillance Network and the Nova Scotia Department of Environment. The cohort consisted of live singleton births (> or =37 weeks of gestation) between January 1, 1988 and December 31, 2000. Maternal exposures to air pollution were assigned to women living within 25 km of a monitoring station at the time of birth. Air pollution was evaluated as a continuous and categorical variable (using quartile exposures) for each trimester and relative risks were estimated from logistic regression, adjusted for confounding variables.

RESULTS

There were 74,284 women with a term, singleton birth during the study period and with exposure data. In the analyses unadjusted for year of birth, first trimester exposures in the highest quartile for SO2 and PM10 suggested an increased risk of delivering a LBW infant (relative risk = 1.36, 95% confidence interval = 1.04 to 1.78 for SO2 exposure and relative risk = 1.33, 95% confidence interval = 1.02 to 1.74 for PM10). After adjustment for birth year, the relative risks were attenuated somewhat and not statistically significant. A dose-response relationship for SO2 was noted with increasing levels of exposure. No statistically significant effects were noted for ozone.

CONCLUSION

Our results suggest that exposure during the first trimester to relatively low levels of some air pollutants may be associated with a reduction in birth weight in term-born infants. These findings have implications for the development of effective risk management strategies to minimize the public health impacts for pregnant women.

A review of time-series studies used to evaluate the short-term effects of air pollution on human health

We review the methodology used in the analysis of time-series studies of ambient air pollution. Our focus is on mortality studies, in which daily counts of death are correlated with changes in air pollution. We first illustrate the methods by showing data from the 1950s, during which the effects of air pollution were much more pronounced, and then describe current methods that were developed to identify associations when the signal-to-noise ratio is much lower. We describe basic data sources, details of statistical methods, and current state of the art, especially as it refers to problems found recently with the fitting algorithm used in the generalized additive models. A summary of the findings from mortality studies is presented and the pre-eminent issues regarding methods, interpretation, and identification of susceptible populations are discussed. We conclude by describing possible biological mechanisms and suggesting other designs that will aid in the interpretation of data from studies of acute health effects.

Identifying and managing adverse environmental health effects: 2. Outdoor air pollution

Air pollution contributes to preventable illness and death. Subgroups of patients who appear to be more sensitive to the effects of air pollution include young children, the elderly and people with existing chronic cardiac and respiratory disease such as chronic obstructive pulmonary disease and asthma. It is unclear whether air pollution contributes to the development of asthma, but it does trigger asthma episodes. Physicians are in a position to identify patients at particular risk of health effects from air pollution exposure and to suggest timely and appropriate actions that these patients can take to protect themselves. A simple tool that uses the CH2OPD2 mnemonic (Community, Home, Hobbies, Occupation, Personal habits, Diet and Drugs) can help physicians take patients' environmental exposure histories to assess those who may be at risk. As public health advocates, physicians contribute to the primary prevention of illness and death related to air pollution in the population. In this article we review the origins of air pollutants, the pathophysiology of health effects, the burden of illness and the clinical implications of smog exposure using the illustrative case of an adolescent patient with asthma.

Association between ozone and hospitalization for acute respiratory diseases in children less than 2 years of age

To clarify the health effects of ozone exposure in young children, the authors studied the association between air pollution and hospital admissions for acute respiratory problems in children less than 2 years of age during the 15-year period from 1980 to 1994 in Toronto, Canada. The daily time series of admissions was adjusted for the influences of day of the week, season, and weather. A 35% (95% confidence interval: 19%, 52%) increase in the daily hospitalization rate for respiratory problems was associated with a 5-day moving average of the daily 1-hour maximum ozone concentration of 45 parts per billion, the May-August average value. The ozone effect persisted after adjustment for other ambient air pollutants or weather variables. Ozone was not associated with hospital admissions during the September-April period. Ambient ozone levels in the summertime should be considered a risk factor for respiratory problems in children less than 2 years of age.

The costs of cardiorespiratory disease episodes in a study of emergency department use

OBJECTIVE

The average per person direct cost of illness of cardiorespiratory disease episodes was estimated based on a prospective study of emergency department visits.

METHODS

Economic modelling of health care costs using prospectively collected resource utilization data (9/1/94 to 8/31/95) from hospital emergency department visitors assigned a diagnosis of asthma, chronic obstructive pulmonary disease (COPD), respiratory infections or cardiac conditions.

RESULTS

The total direct costs (1997 CDN$) [95% C.I.] per patient were $1,043.55 [$922.65, $1,164.47] for asthma, $1,690.11 [$1,276.92, $2,103.30] for COPD, $676.50 [$574.46, $778.54] for respiratory infections, and $3,318.74 [$2,937.72, $3,699.76] for cardiac conditions.

CONCLUSIONS

This study showed that on average, patients diagnosed with a cardiac condition had the highest total direct cost. Hospitalization cost was the largest component of costs for all diagnoses except asthma, for which medications were the single largest component of direct costs.

The costs of cardiorespiratory disease episodes in a study of emergency department use

OBJECTIVE

The average per person direct cost of illness of cardiorespiratory disease episodes was estimated based on a prospective study of emergency department visits.

METHODS

Economic modelling of health care costs using prospectively collected resource utilization data (9/1/94 to 8/31/95) from hospital emergency department visitors assigned a diagnosis of asthma, chronic obstructive pulmonary disease (COPD), respiratory infections or cardiac conditions.

RESULTS

The total direct costs (1997 CDN$) [95% C.I.] per patient were $1,043.55 [$922.65, $1,164.47] for asthma, $1,690.11 [$1,276.92, $2,103.30] for COPD, $676.50 [$574.46, $778.54] for respiratory infections, and $3,318.74 [$2,937.72, $3,699.76] for cardiac conditions.

CONCLUSIONS

This study showed that on average, patients diagnosed with a cardiac condition had the highest total direct cost. Hospitalization cost was the largest component of costs for all diagnoses except asthma, for which medications were the single largest component of direct costs.

Effects of particulate and gaseous air pollution on cardiorespiratory hospitalizations

We obtained data on daily numbers of admissions to hospital in Toronto, Canada, from 1980 to 1994 for respiratory, cardiac, cerebral vascular, and peripheral vascular diseases. We then linked the data to daily measures of particulate mass less than 10 microns in aerodynamic diameter (PM10), particulate mass less than 2.5 microns in aerodynamic diameter (PM2.5), and particulate mass between 2.5 and 10 microns in aerodynamic diameter (PM10-2.5), ozone, carbon monoxide, nitrogen dioxide, and sulfur dioxide. Air pollution was only associated weakly with hospitalization for cerebral vascular and peripheral vascular diseases. We controlled for temporal trends and climatic factors, and we found that increases of 10 microg/m3 in PM10, PM2.5, and PM10-2.5 were associated with 1.9%, 3.3%, and 2.9% respective increase in respiratory and cardiac hospital admissions. We further controlled for gaseous pollutants, and the percentages were reduced to 0.50%, 0.75%, and 0.77%, respectively. Of the 7.72 excess daily hospital admissions in Toronto attributable to the atmospheric pollution mix, 11.8% resulted from PM2.5, 8.2% to PM10-2.5, 17% to carbon monoxide, 40.4% to nitrogen dioxide, 2.8% to sulfur dioxide, and 19.8% to ozone.

The association between ambient carbon monoxide levels and daily mortality in Toronto, Canada

The role of ambient levels of carbon monoxide (CO) in the exacerbation of heart problems in individuals with both cardiac and other diseases was examined by comparing daily variations in CO levels and daily fluctuations in nonaccidental mortality in metropolitan Toronto for the 15-year period 1980-1994. After adjusting the mortality time series for day-of-the-week effects, nonparametic smoothed functions of day of study and weather variables, statistically significant positive associations were observed between daily fluctuations in mortality and ambient levels of carbon monoxide, nitrogen dioxide, sulfur dioxide, coefficient of haze, total suspended particulate matter, sulfates, and estimated PM2.5 and PM10. However, the effects of this complex mixture of air pollutants could be almost completely explained by the levels of CO and total suspended particulates (TSP). Of the 40 daily nonaccidental deaths in metropolitan Toronto, 4.7% (95% confidence interval of 3.4%-6.1%) could be attributable to CO while TSP contributed an additional 1.0% (95% confidence interval of 0.2-1.9%), based on changes in CO and TSP equivalent to their average concentrations. Statistically significant positive associations were observed between CO and mortality in all seasons, age, and disease groupings examined. Carbon monoxide should be considered as a potential public health risk to urban populations at current ambient exposure levels.

Eliciting stated health preferences: an application to willingness to pay for longevity

The economic analysis of many health policies requires evaluation of the benefits of programs that may prolong human lives. This article contributes to the development of credible values for longevity, demonstrating the feasibility of applying stated-preference market-research techniques to a new area of preference revelation and framing the problem as extending longevity under realistic health states associated with advanced age. Respondents to the authors' stated-preference survey clearly indicated that quality of life affects the value of quantity of life. The results demonstrate the sensitivity of life-extension values to specific health and activity-limitation conditions. The article also discusses problems that remain to be solved before valid and reliable longevity values can be obtained.

Health and development in the Hudson Bay/James Bay region

This paper reviews the literature on the health status of native people in the Hudson Bay/James Bay region of Canada, and explores the role of development in explaining discrepancies between observed and expected demographic and health trends. Relevant scientific literature was identified using computerised searches of bibliographic databases, as well as manual searches of selected journals and contact with experts. Although there was evidence that native people in Hudson Bay/James Bay have experienced significant improvements in health status, overall health status remains much worse than that of other Canadians. In many native communities, the prevalence and incidence of formerly infrequent chronic diseases have now surpassed those observed in non-native populations, and injuries, poisonings and violence are at epidemic levels. While these trends may be attributable to a variety of factors, environmental contamination and accompanying social, economic and cultural changes appear to play an important role.

Modelling psychosocial effects of exposure to solid waste facilities

A parallel case study design was used to investigate psychosocial effects in populations exposed to solid waste facilities. Psychosocial effects were defined as a complex of distress, dysfunction and disability, manifested in a range of psychological, social and behavioural outcomes, as a consequence of actual or perceived environmental contamination. This paper presents the results of logistic regression analyses designed to identify determinants of psychosocial effects of exposure. The data come from an epidemiologic survey of residents (N = 696) living within a prescribed radius from each of three solid waste facilities in southern Ontario. The analytical model has three main components: external variables (e.g. individual and exposure-related variables); mediating variables (e.g. social network membership and involvement, general health status measures); and outcome variables (e.g. concern, effects and actions). Results for a series of site specific analyses show that outcome measures can be successfully explained by a combination of external and mediating factors. In general, variables from each of the three main components enter the concern-related models while the action models are clearly dominated by social network variables. Analyses using data from all three sites indicate the explanatory power of site-related characteristics. However, given the number and diversity of variables in the models, there is no support for a simple cause and effect relationship. The implication is that strategies aimed to address and alleviate psychosocial effects need to be specific to the characteristics of the populations in particular settings.

Fatal occupational accidents in Ontario, 1986-1989

We examined 470 fatal occupational accidents in Ontario, 1986-1989, that met eligibility criteria. Homicides and most accidents on public roads were excluded. Information was obtained from coroners' files and records of the provincial Ministry of Labour. Levels of alcohol likely to produce impairment were found in six subjects (2% of the two-thirds of fatalities tested). Cannabis was detected in 3.9% of cases (17% of those tested), but other illegal drugs were not found. Recommendations of coroner's juries showed that organizational factors were considered relevant on many occasions, although language and literacy were rarely mentioned. The incidence rate rose steadily with age. Other data items were examined, although, because of missing information and/or lack of denominator data for many of them, the conclusions that can be drawn are limited. Among these tentative findings was that more fatal accidents occurred in the first half of the shift than in the second half.