Why in the News?

Delhi government has announced a feasibility study to test photocatalytic coatings on roads, pavements, and public spaces to bring visible improvements in air quality.

About Smog:

• Overview: Combination of smoke and fog, forming smoky fog with soot, gases, and moisture.
• Components: Includes soot particulates, sulphur dioxide (SO₂), nitrogen dioxide (NO₂), hydrocarbons, carbon monoxide (CO), and ozone (O₃).

• Types:

  1. Sulfurous Smog (London Smog) – Caused by burning coal and sulphur-bearing fuels; worsened by dampness and particulates.
  2. Photochemical Smog (Los Angeles Smog) – Produced when NOₓ and hydrocarbons react under sunlight, forming ozone; appears as a brownish haze with respiratory effects.

• Pollutants:

  1. Primary pollutants: Directly emitted (NO₂, SO₂, hydrocarbons).
  2. Secondary pollutants:  Formed via reactions (ozone, acid rain).
• Haze vs. Smog: Haze = dry particles reducing visibility; Smog = pollutants with condensation.
• Effects: Respiratory distress, eye irritation, plant damage, reduced visibility, carcinogenic risk, worsened by inversion layers and low rainfall.

What are “Smog-Eating” Coatings?

• Technology: Photocatalytic coatings using titanium dioxide (TiO₂) on roads, pavements, and public surfaces.
• Function: Under sunlight, TiO₂ breaks down pollutants like NO₂ and hydrocarbons into less harmful compounds.
• Advantages: Low-cost, stable, compatible with traditional materials, effective in depollution and creating self-cleaning surfaces.

Delhi Government Plan

• Plan: If viable, Cabinet proposal for citywide rollout at busy corridors, markets, and public spaces.
• Evaluation: Study to assess cost-effectiveness, safety, and sustainability while shortlisting suppliers.
• Strategic Context: Part of a 24×7, year-round environmental action plan using technology-driven interventions.

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