Examination of effect modification of the relationship between PM2.5 and cardiovascular mortality by particle oxidative potential within two Canadian cities
Bibliographic record
Abstract
BACKGROUND AND AIM There is evidence that particle oxidative potential modifies effects of fine particulate matter air pollution (PM2.5) on health outcomes in between-cities studies in Canada. Additionally, previous work shows that oxidative potential of PM2.5 varies considerably at the within-city spatial scale. The aim of the present study was to determine if differences in the oxidative potential of PM2.5 at the within-city spatial scale modify the relationship between PM2.5 and cardiovascular mortality. METHODS We conducted a cohort study in the Canadian Census Health and Environment Cohort, a population-based cohort based on the Canadian longform Census. We followed participants who lived in the cities of Toronto or Montreal, Canada, at least 2 years in the period 2001-2016 (approximately 12 271 100 person-years in 1 101 000 individuals, rounded for confidentiality). Annual estimates of PM2.5 exposures were assigned from satellite data calibrated with ground-based observations, and oxidative potential was measured on samples of PM2.5 taken at 234 sites across the study area. We used time-varying Cox proportional hazards models to estimate hazard ratios for the effect of PM2.5 on cardiovascular mortality within strata of PM2.5 oxidative potential. Additionally, we estimated hazard ratios for oxidative burden (the product of oxidative potential and PM2.5 exposures). RESULTS We did not find evidence that oxidative potential modifies the effect of PM2.5 on mortality from cardiovascular causes (N = approximately 6100 events). The overall relationship between PM2.5 exposures and cardiovascular mortality was not significantly different from the null, and the same was true for oxidative burden measures. CONCLUSIONS Spatial variability in PM2.5 and the oxidative potential of PM2.5 may be insufficient for OP to act as a modifier of the effect of PM2.5 on cardiovascular mortality within the cities of Toronto and Montreal. KEYWORDS : fine particulate matter, oxidative potential, outdoor air pollution, cardiovascular disease
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.009 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.003 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".