Particulate Matter: Its Impact On Human Health And Wellbeing

Particulate matter is a mix of tiny solid and liquid particles in the air we breathe. These particles are so small that they are often invisible, but when their levels are high, the air becomes hazy and thick.

The size of the particles is directly linked to their potential for causing health problems. Smaller particles, less than 10 micrometres in diameter, pose the greatest problems as they can get deep into your lungs and some may even get into your bloodstream.

Exposure to such particles can affect both your lungs and your heart. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including:

- Premature death in people with heart or lung disease

- Nonfatal heart attacks

- Decreased lung function

- Increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing

Particulate matter can enter the bloodstream and cause systemic inflammation

Particulate matter is a mixture of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid coatings. It includes acids (such as nitrates and sulfates), organic chemicals, metals, soil or dust particles, and allergens (such as fragments of pollen or mould spores).

The size of particles is directly linked to their potential for causing health problems. Particles smaller than 10 micrometres in diameter pose the greatest problems because they can get deep into the lungs, and some may even get into the bloodstream. Larger particles can irritate the eyes, nose, and throat, but are less concerning for health impacts.

Particulate matter has been linked to a variety of health problems, including premature death in people with heart or lung disease, non-fatal heart attacks, decreased lung function, and increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.

People with heart or lung diseases, children, older adults, minority populations, and low socioeconomic status populations are the most likely to be affected by particle pollution exposure, either because they are more sensitive or may have higher exposures.

Particulate matter can cause lung inflammation and lung disease

PM2.5 is defined as particles that are 2.5 micrometers or less in diameter. These particles are more likely to travel into and deposit on the surface of the deeper parts of the lung. In contrast, PM10 particles are more likely to deposit on the surfaces of the larger airways of the upper region of the lung.

Both PM2.5 and PM10 can induce adverse health effects. Short-term exposure to PM2.5 has been associated with premature mortality, increased hospital admissions for heart or lung causes, acute and chronic bronchitis, asthma attacks, emergency room visits, respiratory symptoms, and restricted activity days. Long-term exposure to PM2.5 has been linked to premature death, particularly in people with chronic heart or lung diseases, and reduced lung function growth in children.

Short-term exposure to PM10 has been associated with the worsening of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), leading to hospitalization and emergency department visits. The effects of long-term exposure to PM10 are less clear, although several studies suggest a link between long-term PM10 exposure and respiratory mortality.

Particulate matter can cause oxidative stress and DNA damage

Oxidative stress is an imbalance of free radicals and antioxidants in the body, which can lead to cell and tissue damage. Particulate matter can induce oxidative stress by generating reactive oxygen species (ROS) and inducing oxidative stress responses. ROS are highly reactive molecules that can damage DNA, proteins, and lipids in cells.

Particulate matter can also cause DNA damage by inducing ferroptosis, an iron-dependent form of cell death, and activating cell death signalling pathways. In addition, particulate matter can compromise the integrity of the nasal epithelium and reduce trans-epithelial resistance, allowing particles to enter the bloodstream.

Particulate matter can cause cardiovascular disease

Particulate matter is a mixture of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid coatings. The size of the particles is directly linked to their potential for causing health problems. Particles smaller than 10 micrometres in diameter pose the greatest problems, as they can get deep into the lungs and even enter the bloodstream.

• Systemic inflammation
• Translocation into the blood
• Direct and indirect effects on the autonomic nervous system

The pathways by which inhaled particle pollution affects cardiovascular health are detailed below:

• Inhaled particle pollution reaches the alveoli, where it can increase the formation of reactive oxygen species and initiate an inflammatory response. Alveolar macrophages are likely to release pro-inflammatory cytokines with secondary effects on vascular control, heart rate variability, contractility, and rhythm.
• Following deposition, small amounts (1%) of ultrafine insoluble particles, or more soluble components of any size particles (e.g., metals), may translocate from the lung directly into the circulation where the particle might have direct impact on cardiovascular function and/or have direct effects on the central nervous system with secondary effects on the heart and blood vessels via the autonomic nervous system.
• Alternatively, particles might activate pulmonary sensory receptors and modulate the autonomic nervous system. Oxidative stress could play a role in exacerbating the stages of each pathway, as well as promoting interactions between pathways (e.g., in conjunction with inflammation).

Particulate matter can cause neurological disease

Particulate matter (PM) is a component of air pollution that has been linked to a range of adverse health effects, including neurological issues. The impact of PM on the central nervous system (CNS) is a growing area of concern, with evidence suggesting that it may contribute to the development of neurological disorders.

Impact on the CNS

Air pollution, particularly fine particulate matter, can enter the brain through various routes, including the olfactory system, the blood-brain barrier, and the trigeminal nerve. Once in the brain, PM can induce neurotoxicity, neuroinflammation, oxidative stress, and damage to the blood-brain barrier and neurovascular units. These effects may contribute to an increased risk of neurodegeneration and the development of neurological disorders.

Neurological Disorders

A growing body of research links exposure to air pollutants with poor brain health and an increased incidence of neurological and psychiatric disorders. These include cognitive decline, dementia, Alzheimer's disease, Parkinson's disease, anxiety, depression, schizophrenia, attention deficit hyperactivity disorder (ADHD), and multiple sclerosis.

Mechanisms

The precise mechanisms by which PM affects neurodegeneration are still unclear, but several studies have provided insights. Oxidative stress and inflammation have been identified as key processes through which PM exerts its toxic effects on the CNS. Additionally, PM exposure has been linked to metabolic abnormalities and mitochondrial dysfunction in the brain, which can further contribute to neurodegeneration.

Interventions

While minimizing exposure to air pollutants is the most effective way to reduce the risk of neurological diseases, there is ongoing research into potential interventions. Some studies suggest that dietary supplementation with antioxidants, such as vitamins C and E, may help reduce the harmful effects of PM exposure. Additionally, B vitamins have been found to mitigate the effects of PM on the cardiovascular system and reduce the methylation of genes related to energy metabolism in mitochondria.

Further research is needed to fully understand the relationship between PM exposure and neurological diseases and to develop effective interventions to reduce the impact of air pollution on brain health.

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