Association of Sulfur, Transition Metals, and the Oxidative Potential of Outdoor PM2.5 with Acute Cardiovascular Events: A Case-Crossover Study of Canadian Adults

Abstract

Background: We do not currently understand how spatiotemporal variations in the composition of fine particulate air pollution [fine particulate matter with aerodynamic diameter ( )] affects population health risks. However, recent evidence suggests that joint concentrations of transition metals and sulfate may influence the oxidative potential (OP) of and associated health impacts. Objectives: The purpose of the study was to evaluate how combinations of transition metals/OP and sulfur content in outdoor influence associations with acute cardiovascular events. Methods: We conducted a national case-crossover study of outdoor and acute cardiovascular events in Canada between 2016 and 2017 (93,344 adult cases). Monthly mean transition metal and sulfur (S) concentrations in were determined prospectively along with estimates of OP using acellular assays for glutathione ( ), ascorbate ( ), and dithiothreitol depletion ( ). Conditional logistic regression models were used to estimate odds ratios (OR) [95% confidence intervals (CI)] for across strata of transition metals/OP and sulfur. Results: Among men, the magnitudes of observed associations were strongest when both transition metal and sulfur content were elevated. For example, an OR of 1.078 (95% CI: 1.049, 1.108) (per ) was observed for cardiovascular events in men when both copper and S were above the median, whereas a weaker association was observed when both elements were below median values ( , 95% CI: 1.007, 1.031). A similar pattern was observed for OP metrics. was not associated with acute cardiovascular events in women. Discussion: The combined transition metal and sulfur content of outdoor influences the strength of association with acute cardiovascular events in men. Regions with elevated concentrations of both sulfur and transition metals in should be examined as priority areas for regulatory interventions. https://doi.org/10.1289/EHP9449

Long-term Exposure to Oxidant Gases and Mortality: Effect Modification by PM2.5 Transition Metals and Oxidative Potential

“…If the observed health impacts of O x are attributable the combined oxidative nature of the gases themselves, our results have important implications for future regulatory interventions aimed at reducing emissions of individual PM 2.5 components/sources. Specifically, our results suggest that there could be substantial cobenefits to further reductions in transition metals and sulfur in PM 2.5 as these reductions could reduce the health impacts of outdoor PM 2.5 8 as well as the long-term health effects of O x . Of the specific components examined, differences across strata were greatest for Ni and S. Fuel oil combustion is an important source of Ni in PM 2.5 29 and both transportation and industrial sources contribute to sulfur (i.e., sulfate) in PM 2.5 (although sulfur emissions have decreased over time).…”

“… 1 , 2 , 18 , 19 Sulfur was included in our PM 2.5 component analyses as we recently reported that the acute cardiovascular health impacts of PM 2.5 mass concentrations were stronger in men when both S and transition metals were elevated (S makes the particles more acidic and is thought to make the metals more biologically available). 8 , 20 Therefore, we wanted to examine how combinations of these components may modify the health impacts of O x .…”

“…This hypothesis is supported by existing evidence suggesting that outdoor PM 2.5 with higher oxidative potential is more strongly associated with adverse health outcomes. 1,2,[4][5][6][7][8] However, this paradigm should not only apply to outdoor PM 2.5 , but all air pollutants capable of contributing to oxidative damage in human systems. Therefore, if oxidant gases are harmful to human health Submitted March 31, 2022; accepted July 27, 2022 a primarily through their ability to cause oxidative stress, the health impacts of oxidant gases may be greater in populations coexposed to PM 2.5 that is more capable of causing oxidative stress because the combined oxidative impacts of PM 2.5 and oxidant gases may be greater in these locations.…”

A Review of Road Traffic-Derived Non-Exhaust Particles: Emissions, Physicochemical Characteristics, Health Risks, and Mitigation Measures

“…A study of Canadian hospital admissions found increased cardiovascular events in men associated with Cu, Fe, and Zn exposures when increased sulfur concentrations were also present (e.g., Cu OR = 1.08, 95% CI 1.05–1.11 per 10 μg/m 3 ). 163 …”

“…It also reported significant heterogeneity in cardiovascular morbidity with PM 2.5 Fe and Zn (Cochran’s I 2 = 52% and 62%, respectively). A study of Canadian hospital admissions found increased cardiovascular events in men associated with Cu, Fe, and Zn exposures when increased sulfur concentrations were also present (e.g., Cu OR = 1.08, 95% CI 1.05–1.11 per 10 μg/m 3 ) …”