Analysis reveals increased black carbon in particulate matter raises risk of acute myocardial infarction

It has been pointed out that particulate matter with an aerodynamic diameter of ≤2.5µm (PM_2.5) may be involved in the development of respiratory diseases, cardiovascular diseases, and even cancer. However, it is not well understood which particles contained within PM_2.5 are associated with which diseases.

A research group led by Vice Director Sunao Kojima of Sakura-jyuji Yatsushiro Rehabilitation Hospital (Visiting Professor, Kumamoto University); Associate Professor Takehiro Michikawa at Toho University Faculty of Medicine; and Fellow Akinori Takami and Senior Researcher Ayako Yoshino at the National Institute for Environmental Studies, analyzed observation data from seven prefectures and data from the Japanese Registry of all Cardiac and Vascular Diseases (JROAD) of the Japanese Cardiovascular Society. The research group revealed that an increase of black carbon, which makes up approximately 3% of PM_2.5, raises the risk of developing acute myocardial infarction.

Kojima stated: "It has been said that PM_2.5 is harmful to health, but the question was what, specifically, is harmful? In this study, we found that black carbon, which comprises only 3% of the components, increases the incidence rate of acute myocardial infarction. We hope that the knowledge gained will be utilized in policy formulation and other areas by continuing to verify the health effects of PM_2.5 by component." The study was published in Communications Medicine.

For PM_2.5 and its components, observation data was used from seven prefectures (Hokkaido, Niigata, Tokyo, Aichi, Osaka, Hyogo, Fukuoka) from the Aerosol Chemical Speciation Analysers deployed by the Ministry of the Environment at 10 locations nationwide, excluding remote islands and areas with small populations. Additionally, from 102,233 patients registered in JROAD who were hospitalized for acute myocardial infarction at 828 domestic hospitals from April 1, 2017, to December 31, 2019, 44,232 patients were selected for analysis after screening based on conditions such as being 40 years or older, residing in target areas, and excluding emergency admissions.

Statistical analysis results showed that when the total PM_2.5 concentration on the day of and the day before hospitalization for acute myocardial infarction increased by 7.9 micrograms per cubic meter, the risk of acute myocardial infarction increased by 2.4%. The results were substantially similar even after adjusting for other air pollutants (nitrogen dioxide, sulfur dioxide, photochemical oxidants).

Furthermore, when analyzing by individual components, acute myocardial infarction risk increased by 2.75% for every 0.3 microgram increase in black carbon concentration on the day before and day of hospitalization, and the significant association persisted even after adjusting for other components. On the other hand, no clear associations were observed for water-soluble organic compounds, nitrate ions, or sulfate ions. Michikawa stated: "We know that when black carbon concentration increases to about 1 microgram, the risk increases at the same rate, but since the baseline amount is small, we don't know what happens when it increases extremely, such as tenfold."

The environmental standards for PM_2.5 are an annual average of 15 micrograms and daily average of 35 micrograms, which have been maintained below these levels since 2015. Yoshino stated: "The impact of reduced emissions from China is significant, but since black carbon does not reach Japan, we need to consider domestic emission sources." Takami said: "The environmental standards are supposed to be reviewed as necessary when they are established. We will request the Ministry of the Environment to examine this issue, including the data we compiled in this research."

Journal Information
Publication: Communications Medicine
Title: Components of particulate matter as potential risk factors for acute myocardial infarction
DOI: 10.1038/s43856-025-01095-z