Environmental Chemistry for NEET: Air & Water Pollution Notes

Most questions are memory-based, such as definitions, causes, and pollutant sources. NEET frequently lifts lines directly from NCERT, including box information and summary points.

While conceptual understanding helps, this chapter is more about smart revision, NCERT familiarity, and keyword recall. Focus on tables, chemical reactions, and pollutant effects to improve retention.

Air Pollution: Key Topics for NEET

Major Air Pollutants

Air pollution refers to the contamination of the atmosphere by harmful gases, particulates, and chemicals.

Key air pollutants to remember for NEET:

• Nitrogen Oxides (NO, NO₂): Cause acid rain and photochemical smog.
• Sulphur Dioxide (SO₂): Causes respiratory issues and acid rain.
• Carbon Monoxide (CO): A poisonous gas that binds to hemoglobin.
• Particulate Matter (PM10, PM2.5): Tiny particles that affect lung function.
• Greenhouse Gases: CO₂, CH₄, CFCs, and water vapor contribute to global warming and climate change.

NEET often asks about the source, effect, or type of these pollutants.

Acid Rain & Smog

Acid Rain is caused by the dissolution of acidic oxides in rainwater:

It damages vegetation, buildings, and aquatic life. NEET may ask for chemical equations or effects.

Smog is of two types:

• Classical Smog (London Smog): Sulphur-based, occurs in cold/humid climates.
• Photochemical Smog (Los Angeles Smog): Formed by sunlight acting on NOx and hydrocarbons; produces PAN, ozone, and aldehydes.

PAN (Peroxyacetyl nitrate) is a powerful eye irritant and plant toxin. Ozone (O₃) formed in lower atmosphere acts as a pollutant, though it’s protective in the upper atmosphere.

Control Measures

NEET also tests simple control strategies:

• Catalytic Converters: Convert CO, NOx, and unburnt hydrocarbons into less harmful substances.
• CNG (Compressed Natural Gas): Cleaner fuel that reduces particulate and CO emissions.
• Switching to alternate energy sources like electricity or biofuels to reduce dependence on fossil fuels.

These are common one-liner questions in NEET papers, especially from the NCERT summary.

Water Pollution: Must-Know Concepts

Common Pollutants

Water pollution occurs due to the addition of harmful substances into water bodies. NEET commonly asks about the types of pollutants and their health/environmental impact.

• Heavy Metals ():
  Toxic to the nervous system, cause kidney damage and developmental disorders.
  Mercury pollution can result in Minamata disease.
• Detergents:
  Non-biodegradable detergents create foam, reduce oxygen content, and harm aquatic life.
• Pesticides and Fertilizers (DDT, nitrates, phosphates):
  Cause bioaccumulation, disrupt aquatic ecosystems, and may lead to eutrophication.

Biochemical Oxygen Demand (BOD) & Chemical Oxygen Demand (COD)

BOD (Biochemical Oxygen Demand):

The amount of oxygen required by aerobic bacteria to decompose organic matter in water.

COD (Chemical Oxygen Demand):

The total oxygen needed to oxidize both organic and inorganic matter chemically.

NEET Focus:

• High BOD/COD values = high pollution levels.
• BOD is a better indicator of water pollution from biological waste.

NEET often asks for definitions, comparisons, or their use as pollution indicators.

Control of Water Pollution

Key treatment methods often asked in NEET:

• Sewage Treatment:
  Involves primary (physical), secondary (biological), and tertiary (chemical) treatment.
• Oxidation Ponds:
  Natural method using algae and bacteria to treat sewage.
• Activated Sludge Process:
  Uses aerated tanks to break down organic pollutants.

These are directly covered in NCERT, and NEET questions often test recognition or matching.

Important Terms & NCERT Line Facts

Here are high-frequency NEET terms and definitions directly derived from NCERT lines:

• Eutrophication:
  Nutrient overload (especially nitrates & phosphates) causes excessive algal bloom, leading to oxygen depletion in water bodies.
• Greenhouse Effect:
  Warming of Earth’s surface due to gases like, , water vapor, and trapping infrared radiation.
• Ozone Hole:
  Depletion of ozone in the stratosphere, mainly over Antarctica.

Ozone Depletion:

Role of CFCs:
CFCs release chlorine radicals in the upper atmosphere:

This reaction breaks down ozone, allowing more UV rays to reach the Earth, leading to skin cancer, cataracts, and reduced crop yield.

NEET Tip: Memorize these reactions. They appear frequently in assertion-reason or one-liner questions.

Quick Revision Table: Pollution Summary for NEET

Flash Facts:

• BOD > COD? Never. COD is always higher or equal.
• Photochemical smog forms in sunlight, not foggy weather.
• Ozone good up high, bad nearby.
• Eutrophication → Algal bloom → Oxygen drop → Fish die.

Previous Year NEET Questions (PYQs)

NEET 2024

Q1. The correct statement about photochemical smog is:
A) It occurs in cold humid climate
B) It is rich in SO₂
C) It causes eye irritation
D) It occurs at night

Answer: C
Explanation: Photochemical smog contains PAN and ozone, causing eye irritation and respiratory problems.

NEET 2023

Q2. The BOD value of water is an indicator of:
A) Industrial pollution
B) Thermal pollution
C) Biological oxygen demand
D) Heavy metal content

Answer: C
Explanation: BOD reflects biodegradable organic matter content in water. Higher BOD = more pollution.

NEET 2022

Q3. Which of the following causes depletion of ozone?
A) CO
B) SO₂
C) NO
D) CFCs

Answer: D
Explanation: CFCs release chlorine free radicals that break ozone into oxygen.

NEET 2021

Q4. Greenhouse gases include all except:
A) CO₂
B) Methane
C) Nitrogen
D) Water vapor

Answer: C
Explanation: Nitrogen is not a greenhouse gas; others trap heat in the atmosphere.

Practice Questions for Students

Air Pollution MCQs

Q1. Which of the following is a greenhouse gas?
A) SO₂
B) CO
C) CH₄
D) HCl

Q2. Photochemical smog contains:
A) SO₂ and fog
B) NOx and PAN
C) CO and soot
D) Ammonia and chlorine

Q3. Which pollutant binds with hemoglobin to form carboxyhemoglobin?
A) NO
B) SO₂
C) CO
D) O₃

Water Pollution MCQs

Q4. A high value of BOD indicates:
A) Clean water
B) More oxygen available
C) Low microbial activity
D) High organic pollution

Q5. Which of the following is non-biodegradable?
A) Sewage
B) Dead plants
C) Detergents
D) Animal waste

Answers

A1. C
Explanation: CH₄ (methane) is a key greenhouse gas responsible for trapping heat.

A2. B
Explanation: Photochemical smog contains NOx, hydrocarbons, PAN, and ozone — all formed under sunlight.

A3. C
Explanation: CO binds with hemoglobin to form carboxyhemoglobin, reducing oxygen transport.

A4. D
Explanation: High BOD means more biodegradable organic matter → more oxygen consumed → polluted water.

A5. C
Explanation: Detergents are synthetic and often non-biodegradable, causing long-term water pollution.

Common NEET Mistakes in Environmental Chemistry

Mixing Up Smog Types

• Classical smog: Sulphur-based, cold climate, moist air.
• Photochemical smog: Sunlight-driven, NOx + hydrocarbons → PAN + O₃. NEET Tip: Photochemical smog needs photos (sunlight).

Confusing BOD with COD

• BOD: Oxygen used by microorganisms (biological waste).
• COD: Oxygen used to oxidize total matter (both organic and inorganic). NEET Tip: BOD is biological; COD is chemical.

Skipping NCERT Box Facts

• Questions on eutrophication, ozone-depleting substances, and specific pollutants are lifted directly from NCERT boxes or summary lines. NEET Tip: Revise boxed text and last-page summaries from the NCERT book.

FAQs on Environmental Chemistry for NEET

How many questions come from this chapter?

Typically, 1–2 direct MCQs from Environmental Chemistry are asked every year in NEET. These are usually factual and picked straight from NCERT.

What is the best way to memorize environmental chemistry?

• Make flashcards for pollutants and their effects.
• Use tables and summary notes.
• Revise NCERT definitions word-for-word.
• Practice PYQs to identify recurring patterns.

Are numerical problems asked in this chapter?

No. Environmental Chemistry is completely theory-based. NEET does not ask calculations here. Questions are factual — like pollutant names, causes of smog, or definitions of BOD/COD.

Conclusion

Environmental Chemistry is a low-effort, high-reward chapter in the NEET Chemistry syllabus. With just a few NCERT pages to cover, it offers students a chance to secure 4–8 marks quickly.

Since all questions are direct, factual, and based on real-world scenarios, this chapter is ideal for last-minute revision. By focusing on key terms, pollution control methods, and water/air quality indicators, aspirants can easily tackle NEET-level MCQs.

Final Tip: Stick to NCERT language, revise with tables and flowcharts, and solve at least 5 years of PYQs — and you’ll be ready to score full marks in this section.