Air pollution can greatly increase the risk of cardiovascular disease and mortality in patients with cancer and can contribute to health disparities related to both conditions, according to a state-of-the-art review published in a JACC: CardioOncology focus issue on social and environmental determinants of health and health disparities.

Previous research has linked exposure to air pollution with both cardiovascular disease and cancer. Based on their examination of the results of eight studies published between 2000 and 2023 conducted in cohorts of patients with cancer and cohorts with cardiovascular disease, Wenqiang Zhu, MD, PhD, found that the interaction may be due to effects of air pollution on risk factors common to both, including inflammation and oxidative stress pathways.

Results from the eight studies reveal that exposure to fine particulates ≤2.5 µm (PM_2.5) in the air is significantly associated with a higher risk of cardiovascular disease and mortality among patients who also have cancer, and a higher risk of cancer among patents with cardiovascular disease. Notably, even short-term exposure to high pollution levels rapidly impacted the cardiovascular health of patients with cancer. Overall, they found an increased risk for hypertension, atherosclerosis, myocardial infarction and stroke in relation to exposure to PM_2.5.

Researchers found that not only did PM_2.5 exposure elevate the risk of cardiovascular disease mortality and cardiopulmonary mortality, with hazard ratios (HR) ranging from 1.17 to 1.44 per 10-µg/m³ increase in PM_2.5, but that chemotherapy and/or radiation therapy enhanced the risk of air-pollution-associated cardiopulmonary death in patients with cancer. Furthermore, an increase in nitrogen oxides (NOx), a proxy measure for traffic-related air pollution (TRAP), was associated with an increase in cancer incidence or mortality (HR, 1.16) in patients with different forms of cardiovascular disease, and was especially notable for breast cancer (HR, 1.43). Even when persistent heavy smokers were excluded from the analysis, the association remained between TRAP-related exposure and cancer incidence.

Compared with patients without coronary heart disease (CHD), those with CHD exposed to air pollution had a higher incidence of all cancers (HR, 1.19) and increased all-cause mortality (HR, 1.13).

The authors also highlight the current gaps in knowledge. "More research is needed, including clinical studies, to understand the impacts of air pollution on cardiovascular disease and cancer in greater detail," said senior author Xiaoquan Rao, MD, PhD. Rao added that a better understanding of the risks of air pollution on vulnerable populations is "crucial for developing tailored air pollution exposure control measures and individualized patient management strategies aimed at mitigating cardiovascular disease risks among cancer patients."

Additionally, the researchers discuss the interaction between social determinants of health (SDoH) and the contribution of air pollution on health in the U.S. and around the world. PM_2.5 exposure disproportionately affects vulnerable individuals in low- and medium-income countries. Within the U.S., disadvantaged populations, including individuals living in poverty, Black individuals, and non-White groups experience higher exposure to PM_2.5. Researchers attribute this partially to communities living in high-traffic areas with limited access to green space, two important factors in air pollution.

"This review underscores the critical need to consider environmental factors, especially air pollution, in cardio-oncology risk assessment and patient management," says Rao. "By highlighting the significant role of air pollution in the cardiovascular health of cancer patients, our work aims to catalyze further research in this field and inform clinical practices and public health policies.

Other articles in the focus issue include calls to action to foster community engagement in vulnerable populations to advance equitable care and to increase diversity in cardio-oncology clinical trials; SDoH and racial disparities in cardiovascular disease in men with prostate cancer, in Black breast cancer survivors, and patients with transthyretin cardiac amyloidosis; racial disparities in submaximal exercise capacity reductions in breast cancer survivors; a viewpoint on the importance of cardio-oncology training at both the academic and community level; and the editor's page where Editor-in-Chief Bonnie Ky, MD, MSCE, FACC, discusses the need to ensure equitable, inclusive and high-quality care for all. Read the full issue here.

The ACC is committed to working with its members and cardiovascular care teams across the globe to create a culture of health equity, prioritize health equity in all ACC activities and eliminate disparities by ensuring equitable cardiovascular care for all. Part of this involves providing actionable data and tools that empower professionals to address health disparities and social determinants of health. For more information on its initiatives, visit the ACC Health Equity Resource Center.