Long-term exposure to certain particulate matter components, such as PM2.5, including sulphate, ammonium, elemental carbon, and soil dust, has been associated with a higher risk of mental health issues like depression, particularly in older adults with existing conditions. A study of 23,696,223 older adults published in the JAMA Network Open highlighted the need for targeted regulation of harmful PM2.5 components to safeguard vulnerable populations. Researchers from Emory University in the US emphasized that soil dust, sulphate, and elemental carbon were the primary contributors to the elevated depression risk associated with PM2.5 mixtures.
Individuals with comorbidities like hypertension, cardiovascular diseases, neurodegenerative diseases, and respiratory diseases face a significantly increased risk of depression when exposed to total PM2.5 mass and its major components. Sulphate, a byproduct of fossil fuel combustion, can potentially induce depression by impacting the central nervous system through mitochondrial dysfunction and oxidative stress. Elemental carbon, mainly emitted from traffic and biomass burning, may trigger neurotoxic effects via oxidative stress and inflammation, with its small particles capable of crossing the blood-brain barrier.
Soil dust, containing silica and metals like iron and calcium from natural and human sources, poses neurotoxic risks due to its heavy metal content, which can accumulate in the body and cause nervous system damage. While nitrate and organic carbon showed weaker or opposite associations in the study, their impact was considerably lower compared to the positive associations of soil dust, elemental carbon, and sulphate. The research team highlighted that comorbidities could interact synergistically with PM2.5 exposure to accelerate the onset of depression.
