New Delhi, Dec 25 (NationPress) Prolonged exposure to certain components of particulate matter, particularly PM2.5, which includes sulphate, ammonium, elemental carbon, and soil dust, has been linked to a heightened risk of mental health disorders such as depression, as revealed by a recent study.

The research, published in JAMA Network Open, indicated that this risk is significantly more pronounced in older individuals, especially those already suffering from conditions like cardiometabolic and neurologic comorbidities.

The analysis involved over 23 million older adults, emphasizing the need for specific regulations targeting harmful PM2.5 components to safeguard at-risk populations.

“Our findings confirmed that the combined association of PM2.5 mixtures with depression risk was substantially greater than that of PM2.5 alone, pinpointing soil dust, sulphate, and elemental carbon as the primary culprits,” stated researchers from Emory University, US.

The study revealed that individuals with various comorbidities, particularly those with hypertension, cardiovascular diseases (including stroke and congestive heart failure), and neurodegenerative diseases (such as Alzheimer's disease and dementia), faced a significantly higher likelihood of depression when exposed to the overall PM2.5 mass and its major components.

Sulphate, primarily generated from fossil fuel combustion, typically exists in forms such as (NH4)2SO4, NH4HSO4, or sulphuric acid. It may contribute to depression by inducing mitochondrial dysfunction and oxidative stress affecting the central nervous system.

Elemental carbon, mainly emitted from traffic and biomass burning, has been shown to have neurotoxic effects through oxidative stress and systemic inflammation.

Particles of elemental carbon from traffic are small (about 50 nm) and can easily penetrate the blood-brain barrier, resulting in neurotoxicity.

Soil dust, which is rich in silica and metals such as iron and calcium, can originate from both natural and human-induced sources. Its neurotoxic effects may be linked to heavy metals, which can accumulate in the bloodstream and bones, damaging the nervous system.

While nitrate and organic carbon demonstrated smaller or even inverse associations in the study, their links were significantly weaker compared to the positive associations of soil dust, elemental carbon, and sulphate.

“Our findings suggest that comorbidities might synergistically interact with PM2.5 mass and its components, further exacerbating the onset of depression,” the research team concluded.