Non-methane hydrocarbons (NMHCs)

Why in News?

Researchers from Aryabhatta Research Institute of Observational Sciences (ARIES), spent a year (2022–2023) measuring non-methane hydrocarbons (NMHCs) in Munsyari, a high-altitude Himalayan tourist destination.

• NMHC – They are a highly reactive group of volatile organic compounds (VOCs) that contain only carbon and hydrogen, with methane explicitly excluded.
• Primary sources – They are primarily emitted by fossil fuel combustion, vehicular exhaust, industrial processes, and biomass burning.
• Gases included – Common atmospheric gases like ethane, ethene, propane, and benzene.
• Concentration variability – Parts per billion in remote areas to much higher levels in dense, industrialized, or urban locations.

Volatile Organic Compounds (VOCs) are carbon-based chemicals that easily vaporize into the air at room temperature.

Impacts

• Ozone Precursors – In the presence of sunlight and nitrogen oxides, NMHCs undergo complex photochemical reactions that form ground-level (tropospheric) ozone and harmful secondary pollutants like photochemical smog.
• Health Risks – While many light alkanes act largely as irritants or ozone precursors, heavier aromatic hydrocarbons such as benzene are highly toxic and well-documented carcinogens.
• Climate Influence – By reacting with atmospheric radicals (like hydroxyl radicals), NMHCs directly influence the lifetime of other greenhouse gases.

Reference

PIB| NMHC