{
  "abstract": "Ambient air pollution is a major risk factor for morbidity and mortality worldwide. Among the pollutants, fine particulate matter (PM2.5)—particles ≤2.5 µm in aerodynamic diameter—is recognised to cause the largest health impacts. Indeed, in 2021, ambient PM2.5 was estimated to be responsible for 4.7 million deaths and 120 million disability-adjusted life years lost worldwide.1 PM2.5 adversely affects health as it penetrates deep into the lungs and can enter the bloodstream, leading to the development or exacerbation of respiratory and cardiovascular diseases.2 Studies have also linked ambient PM2.5 exposure to other health conditions such as the development of diabetes mellitus and adverse birth outcomes.2 In many cities, ambient PM2.5 can frequently exceed 35 µg/m³, a level considered unhealthy for sensitive groups by the World Health Organization.3 Indeed, 41% of cities with a minimum population of 50 000 experienced population-weighted annual average PM2.5 concentrations above 35 µg/m³ in 2019.4",
  "authors": [
    {
      "affiliations": [
        "Division of Pulmonary and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA",
        "Center for Global Non-Communicable Disease Research and Training, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA",
        "Department of Environmental Health and Engineering, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA"
      ],
      "name": "Laura Nicolaou"
    },
    {
      "affiliations": [
        "Division of Pulmonary and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA",
        "Center for Global Non-Communicable Disease Research and Training, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA",
        "Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA"
      ],
      "name": "William Checkley"
    }
  ],
  "title": "Ultrafine particles and health: the next frontier in understanding air pollution hazards",
  "uid": "015781bd-d8e8-525a-bc20-211fa41cc92e"
}