Discuss in detail the photochemical smog emphasizing its formation, effects and mitigation. Explain the 1999 Gothenburg Protocol.
Approach · directive: “discuss / explain”
What it asks · Explain how photochemical smog forms, what harm it causes and how to curb it, and state what the 1999 Gothenburg Protocol requires.
It asks 2 things — answer each
- Discuss photochemical smog in detail: its formation, its effects and its mitigation
- Explain the 1999 Gothenburg Protocol: what it is and what it requires
Open with · Unlike classical smog of smoke and fog, photochemical smog is a brown, oxidising haze of ground-level ozone formed when sunlight acts on exhaust; its control and the Gothenburg Protocol both target precursors.
Cover
- Formation: nitrogen oxides and volatile organic compounds react in strong sunlight to form ozone, peroxyacetyl nitrate (PAN) and aldehydes; stagnant air and temperature inversion trap the haze.
- Effects: eye irritation, cough, asthma and lung damage, worst for children and the elderly; damaged crops and forests, cracked rubber, poor visibility, and ozone as a greenhouse gas.
- Mitigation: cleaner fuels and tighter vehicle norms, catalytic converters, solvent and petrol-vapour controls, public transport and electric vehicles, smog alerts; the National Clean Air Programme (2019) targets up to 40% lower PM10 in 131 cities by 2025-26.
- Gothenburg Protocol, 1999: under the 1979 UNECE Convention on Long-range Transboundary Air Pollution, the Protocol to Abate Acidification, Eutrophication and Ground-level Ozone set national emission ceilings for sulphur dioxide, nitrogen oxides, ammonia and VOCs from 2010.
- First multi-pollutant, multi-effect protocol; the 2012 amendment, in force since 2019, added emission-reduction commitments for 2020 and beyond and brought in fine particulate matter (PM2.5).
Close with · Smog forms in the air from precursors; coordinated control of nitrogen oxides and VOCs, Gothenburg's multi-pollutant logic that NCAP applies to 131 cities, is the surest cure.
Add value (verified)
- The 1999 Gothenburg Protocol is the Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution to Abate Acidification, Eutrophication and Ground-Level Ozone.EUR-Lex: Council Decision (EU) 2017/1757 on the acceptance of the Amendment to the 1999 Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution to Abate Acidification, Eutrophication and Ground-level Ozone ↗“The Union is a party to the 1999 Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution to Abate Acidification, Eutrophication and Ground-Level Ozone (‘the Gothenburg Protocol’)”
- The Gothenburg Protocol was amended by Decisions 2012/1/EC and 2012/2/EC adopted at the 30th session of the Executive Body of the Convention.EUR-Lex: Council Decision (EU) 2017/1757, recital 4 ↗“The parties present at the 30th session of the Executive Body of the Convention adopted by consensus Decisions 2012/1/EC and 2012/2/EC amending the Gothenburg Protocol.”
- The National Clean Air Programme, launched in January 2019, covers 131 cities in 24 States and aims at reductions of up to 40% in PM10, or attainment of national standards, by 2025-26.PIB (6 April 2023): NCAP targets to achieve reductions up to 40% of PM10 concentrations by 2025-26 (Rajya Sabha reply, MoEFCC) ↗“Ministry of Environment, Forest and Climate Change (MoEFCC) launched National Clean Air Programme (NCAP) in January, 2019 with an aim to improve air quality in 131 cities (non-attainment cities and Million Plus Cities in 24 States by engaging all stakeholders.”
- Annex II, Table 1 of the Gothenburg Protocol holds national emission ceilings for sulphur dioxide, nitrogen oxides, ammonia and VOCs for 2010 up to 2020.EUR-Lex: Council Decision (EU) 2017/1757, text of the amended Gothenburg Protocol, Annex II ↗“Table 1 includes the emission ceilings for sulphur dioxide (SO 2 ), nitrogen oxides (NO x ), ammonia (NH 3 ) and volatile organic compounds (VOCs) for 2010 up to 2020 expressed in thousands of metric tons (tonnes)”
- The amended Protocol's Tables 2 to 6 set emission-reduction commitments for SO2, NOx, NH3, VOCs and PM2.5 for 2020 and beyond, bringing fine particulate matter into the regime.EUR-Lex: Council Decision (EU) 2017/1757, text of the amended Gothenburg Protocol, Annex II ↗“Tables 2–6 include emission reduction commitments for SO 2 , NO x , NH 3 , VOCs and PM 2,5 for 2020 and beyond.”
Question: UPSC's CS (Main) 2022, GS Paper III — paper ↗. Approach: Minimalist IAS, checked 3 Oct 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer· 230words · Minimalist IAS
Unlike classical smog of smoke and fog, photochemical smog is a brown, oxidising haze of ground-level ozone formed when sunlight acts on exhaust; its control and the Gothenburg Protocol both target precursors.
Formation of photochemical smog
- Precursors: nitrogen oxides and volatile organic compounds (VOCs) from vehicles, refineries, solvents and petrol vapour.
- NOx and VOCs
- Strong sunlight
- Ozone, peroxyacetyl nitrate (PAN) and aldehydes
- Trapped by temperature inversion
Effects
- Health: eye irritation, cough, asthma and lung damage, worst for children and elderly.
- Environment: damaged crops and forests, cracked rubber, poor visibility; ozone also warms the climate.
Mitigation
- Cut precursors: cleaner fuels, tighter vehicle norms, catalytic converters, solvent and petrol-vapour controls.
- Shift and plan: public transport, electric vehicles, smog alerts; the National Clean Air Programme (2019) set a target of up to 40% lower PM10 in 131 cities by 2025-26, a deadline now past.
The 1999 Gothenburg Protocol
- What it is: a protocol under the 1979 UNECE Convention on Long-range Transboundary Air Pollution against acidification, eutrophication and ozone.
- What it requires: national emission ceilings from 2010 for sulphur dioxide, nitrogen oxides, ammonia and VOCs, the first multi-pollutant, multi-effect protocol.
- Amended: the 2012 amendment, in force since 2019, added commitments for 2020 onwards and fine particulate matter (PM2.5).
Smog forms in the air from precursors; coordinated control of nitrogen oxides and VOCs, Gothenburg's multi-pollutant logic, which NCAP's city plans need, is the surest cure.
Prepared by Minimalist IAS to the answer standard of Shivam Singh (mentor, 7 years) · facts checked against official sources (how we verify) · updated 3 Oct 2026. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.
