Context: A recent study shows that in urban environments, ultrafine particles of 1 to 100 nanometers, can contribute up to 90% to the total particle number concentration. Largely originating from vehicle emissions, the Nanoparticles can move from the respiratory system to other parts of the human body which has the potential to cause more chronic and acute illnesses. 

Origin of nanoparticles

• Nanoparticles occur naturally in the environment but the major nanoparticle pollutants arise due to Anthropogenic emissions.
  • Natural pollutants: 
    • Sea emits aerosol of salt that ends up floating around in the atmosphere.
    • Smoke from volcanoes and fires contains a huge variety of nanoparticles.
    • Dust from deserts.
    • Trees emit nanoparticles of hydrocarbon compounds such as terpenes (which produce blue haze seen in forests).
  • Anthropogenic pollutants: 
    • Majorly emitted by large industrial processes, power stations, jet aircraft, vehicles (powered by internal combustion engines) and household fuels. 
    • Types of nanoparticles emitted include– partially burned hydrocarbons (in soot), ceria (cerium oxide; from vehicle exhaust catalysts), metallic dust (from brake linings), calcium carbonate (in engine lubricating oils), and silica (from car tires). 
• Concentration of NPs can be influenced by Meteorology and other factors.
  • With the rise in relative humidity, coagulation of these particles results in their concentration becoming high.
  • Higher wind speed can result in the dispersion of these particles.

General facts about Nanoparticles:

• Nanoparticles are extremely small particles that are sized between 1 and 100 nanometers.
• Size: A nanometer is one billionth of a metre. The small size allows nanoparticles to have unique properties compared to larger particles.
• Properties: Nanoparticles have unique optical, electrical, magnetic, chemical, mechanical, thermal, and quantum properties compared to bulk materials. Their high surface area-to-volume ratio also results in enhanced reactivity, solubility, and heat transfer. 

Key examples include:

• Iron oxide nanoparticles are superparamagnetic for data storage, while cobalt has high coercivity.
• Nanoparticles make good catalysts due to their high surface reactivity.
• Mechanical strength increases for nanoparticles of metals like Aluminium.
• Ceramic nanoparticles strengthen composites.
• Quantum effects dominate at the nanoscale.
• Metal nanoparticles like gold and silver have vivid colours due to localised surface plasmon resonance.
• Semiconductor quantum dots have tunable conductivity and fluorescence.

Application of Nanoparticles:

• Medicine & Healthcare – Drug delivery, bioimaging, diagnostics, dental care, sunscreens, antimicrobial coatings.
• Electronics – Nanoelectronics, sensors, data storage devices, quantum dot displays.
• Energy – Solar cells, lithium-ion batteries, fuel additives, hydrogen generation and storage.
• Environment – Pollutant degradation, water treatment, nano-filtration, catalytic converters.
• Agriculture – Pesticides, fertilizers, pathogen detection, encapsulated agrochemicals.
• Food & Packaging – Antimicrobial films, improved barrier properties, moisture control, and thermal stability.
• Cosmetics – UV protection in sunscreens, long-lasting colour pigments, anti-ageing creams.
• Textiles – Stain and wrinkle-resistant fabrics, lightweight protective clothing, moisture wicking.
• Paints & Coatings – Anti-corrosive coatings, thermal barrier coatings, anti-fouling paints.
• Automotive – Fuel cells, lighter and stronger materials, advanced lubricants.
• Aerospace – Lighter and stronger composites, structural health monitoring.
• Defence – Lightweight soldier armour, surveillance, sensors, nanocoatings for equipment.

Concerns are associated with Nanoparticles:

• Respiratory effects – Inhaled nanoparticles can deposit in lungs, causing inflammation, fibrosis, asthma, and lesions. Links to lung cancer have also been reported.
• Cardiovascular toxicity – Nanoparticles like PM2.5 can enter bloodstream and damage blood vessels and heart tissue, leading to thrombosis, arrhythmia and myo-cardiac cell death.
• Skin penetration – Nanoparticles in cosmetics and sunscreens may be absorbed through skin, entering bloodstream. Titanium dioxide nanoparticles caused DNA damage in mice’s skin.
• Bioaccumulation up food chain – Nanoparticles concentrate in algae/plankton, get absorbed by fish/animals which are later consumed by humans, leading to biomagnification.
• Water contamination – Release of nanoparticles into rivers, lakes and groundwater from product waste. Can be toxic to aquatic life. Difficult to filter out nanoparticles.
• Soil pollution – Accumulation in sewage sludge applied as fertilizer. Runoff from landfills. Alters microbial communities in soil.
• Air pollution – Nanoparticle emissions into the air, leading to reduced air quality.