Long-Term Exposure to PM2.5 Constituents and Coronary Heart Disease Risk in China: A Comprehensive Review

Highlights

• Long-term exposure to specific PM2.5 constituents (elemental carbon, organic carbon, nitrate) significantly elevates coronary heart disease (CHD) and acute myocardial infarction (AMI) risk in China.
• Constituent-specific risk profiles differ from those reported in high-income countries, implicating compositional variations in PM2.5 as critical determinants of health impact.
• Evidence from large national cohorts employing advanced exposure assessment (satellite-based machine learning) enhances precision in risk estimation.
• Findings advocate for air quality regulations that target harmful constituents beyond total PM2.5 mass to mitigate cardiovascular disease burden.

Background

Coronary heart disease (CHD) remains a leading cause of morbidity and mortality globally, with ambient air pollution recognized as a pivotal environmental risk factor. Fine particulate matter (PM2.5)—particles ≤2.5 μm in aerodynamic diameter—penetrate deep into the respiratory tract and systemic circulation, promoting inflammation, oxidative stress, and atherogenesis. While numerous studies from high-income countries have established associations between PM2.5 mass and cardiovascular outcomes, emerging evidence from China suggests these relationships may differ, potentially due to distinct PM2.5 composition shaped by regional emissions sources and industrial activities. Detailed constituent-specific data from large prospective cohorts are essential to inform tailored public health interventions.

Key Content

1. Epidemiological Evidence from China-PAR Cohort

The large-scale, nationwide China-PAR (Prediction for Atherosclerotic Cardiovascular Disease Risk in China) Project undertaken by Wang et al. (2026) provides seminal insights into PM2.5 constituent-specific cardiovascular risks. The cohort included 101,906 cardiovascular-disease-free adults followed from 2003 to 2019. Residential annual exposures to elemental carbon (EC), organic carbon (OC), nitrate, and sulfate were modeled via validated satellite-based machine learning algorithms, achieving spatial and temporal resolution superior to traditional ground monitoring alone.

Over a median 11.1 years and 1.23 million person-years of follow-up, the study recorded 3,500 incident CHD cases (including 1,771 AMI events) and 1,321 CHD deaths (with 808 AMI deaths). Adjusted Cox proportional hazards models revealed that per interquartile range (IQR) increase, EC, OC, and nitrate exposures were significantly associated with elevated CHD incidence (HRs 1.10, 1.60, and 1.43 respectively) and mortality, including for AMI outcomes. Sulfate exposure exhibited a weaker, inconsistent risk pattern.

Concentration-response analyses delineated nonlinear risk trends, with generally increasing CHD risk for OC, EC, and nitrate but plateauing at higher exposures for EC and OC. Sulfate demonstrated a nonlinear association with no sustained elevated risk, suggesting differential pathogenic roles and dose-response relationships among constituents.

2. Corroborative International Studies

Supporting evidence from other populations further contextualizes these findings. A Danish nationwide cohort by Lo et al. (2026) involving over 900,000 individuals aged 35–50 observed exposure-response associations for PM2.5, nitrogen dioxide (NO2), elemental carbon, and primary organic aerosols with incident AMI, confirming constituent-specific cardiovascular risks at younger ages.

In the UK Biobank cohort (Chen et al., 2022), associations between PM2.5 and cardiovascular mortality were robust, with interactions suggesting protective effects of high vegetable intake—highlighting lifestyle factors modulating ambient pollution risks. Mechanistic insights come from Canadian cohorts (Zhao et al., 2021) where PM2.5 metal components, particularly iron and copper, correlate with reactive oxygen species generation in pulmonary fluids, linking translocated particles/metals to oxidative stress—a key driver in atherosclerosis.

The Heinz Nixdorf Recall study (Backes et al., 2020) in Germany has illuminated source-specific effects, showing traffic-related PM2.5 exerting stronger stroke risk than industrial PM, with variable impact of constituents such as sulfate and ammonium, though sulfate’s cardiovascular risk remains equivocal, echoing the China-PAR findings on sulfate’s weaker effects.

3. Mechanisms Underlying PM2.5 Constituent-Specific Cardiovascular Effects

PM2.5 constituents differ in their physicochemical properties influencing toxicity. Elemental and organic carbons, often derived from combustion processes, are potent pro-inflammatory agents capable of eliciting endothelial dysfunction, systemic inflammation, and autonomic imbalance. Nitrate, linked to secondary atmospheric reactions, contributes to oxidative stress pathways.

Sulfate, although abundant, primarily originates from industrial SO2 emissions and may have less direct cardiovascular toxicity or could exert complex effects modulated by co-pollutants. The varied concentration-response relationships and inconsistent sulfate risks highlight the importance of differentiating constituents for targeted regulatory policies.

4. Methodological Advances in Exposure Assessment

The China-PAR study and recent cohorts employ satellite-based machine learning models enabling fine-scale spatiotemporal exposure estimation to multiple PM2.5 constituents, overcoming limitations of sparse ground monitors. Integration of residential history with dynamic exposure metrics and comprehensive adjustment for sociodemographic, behavioral, and clinical confounders strengthens causal inference.

Expert Commentary

The collective evidence establishes PM2.5 constituents—especially EC, OC, and nitrate—as significant, independent cardiovascular risk factors beyond aggregated PM2.5 mass. Given China’s unique emission profiles characterized by heavy reliance on coal combustion and rising vehicular traffic, the distinct constituent-risk patterns likely reflect regional pollution sources and chemical transformations.

The public health implication is that regulatory frameworks focused solely on total PM2.5 reduction may inadequately protect cardiovascular health. Instead, incorporating constituent-specific targets, such as limiting carbonaceous particles and nitrates, could yield more substantial cardiovascular benefits.

Challenges persist in disentangling the interplay of multiple pollutants, potential residual confounding, and the need for mechanistic corroboration via biomarker and experimental studies. Moreover, lifestyle interactions (e.g., dietary antioxidants) and genetic susceptibility factors merit further exploration to personalize risk mitigation.

The attenuation of risks at high exposures for some constituents suggests possible saturation effects or cohort-specific resilience, warranting investigation of nonlinear dose-response mechanisms.

Conclusion

Long-term exposure to specific PM2.5 constituents, notably elemental carbon, organic carbon, and nitrate, is robustly associated with increased risks of coronary heart disease and acute myocardial infarction in China. These findings underscore the critical need for air pollution control strategies informed by particle composition rather than PM mass alone. Future research should focus on elucidating biological pathways, refining exposure estimation methods, and integrating lifestyle and genetic factors to comprehensively address the cardiovascular burden of ambient pollution.

References

• Wang W, Liu H, Li Q, et al. Long-Term Exposure to PM2.5 Constituents and Coronary Heart Disease Risk in China. Journal of the American College of Cardiology. 2026; PMID: 42455100. https://pubmed.ncbi.nlm.nih.gov/42455100/
• Lo FC, et al. Long-term exposure to ambient air pollution and risk of incident acute myocardial infarction in a nationwide register-based cohort study. Int Arch Occup Environ Health. 2026;99(2):9. PMID: 41543751. https://pubmed.ncbi.nlm.nih.gov/41543751/
• Chen H, et al. Ambient air pollution, healthy diet and vegetable intakes, and mortality: a prospective UK Biobank study. Int J Epidemiol. 2022;51(4):1243-1253. PMID: 35179602. https://pubmed.ncbi.nlm.nih.gov/35179602/
• Zhao X, et al. Long-term exposure to iron and copper in fine particulate air pollution and their combined impact on reactive oxygen species concentration in lung fluid: a population-based cohort study of cardiovascular disease incidence and mortality in Toronto, Canada. Int J Epidemiol. 2021;50(2):589-601. PMID: 33367589. https://pubmed.ncbi.nlm.nih.gov/33367589/
• Backes C, et al. Long-term exposure to ambient source-specific particulate matter and its components and incidence of cardiovascular events – The Heinz Nixdorf Recall study. Environ Int. 2020;142:105854. PMID: 32590280. https://pubmed.ncbi.nlm.nih.gov/32590280/