Introduction
Pollution is the introduction of contaminants into the natural environment that cause adverse change. For a BPSC aspirant, the subtopic “Pollution — air, water, soil, plastic” is not merely a static list of definitions; it is a dynamic field that connects public health, economic development, law, and geography. The Bihar Public Service Commission (BPSC) has consistently tested this area, with eight questions appearing in the available previous year papers. These questions range from straightforward factual recall (e.g., the annual average limit for PM2.5) to applied understanding (e.g., the primary cause of soil degradation in North Bihar). The difficulty level is moderate—neither overly technical nor purely rote—requiring aspirants to grasp core concepts and relate them to real-world contexts, especially those relevant to Bihar and India.
This chapter will equip you with everything you need to ace this subtopic. We will start from first principles, defining every key term before using it. We will then dive deep into each pollution type—air, water, soil, and plastic—with a focus on the parameters, standards, causes, and effects that BPSC has historically tested. You will learn how to interpret National Air Quality Index (AQI) parameters, why Biological Oxygen Demand (BOD) is the gold standard for organic pollution, how eutrophication works, and why polyethylene is a persistent threat to soil health. We will walk through actual PYQs step by step, analyse testing patterns, and forecast what could appear next. By the end, you will have a structured, exam-ready understanding of pollution that goes beyond memorisation to genuine comprehension.
Core Concepts & Foundations
Before we examine specific pollution types, we must establish a common vocabulary. Every term below is foundational and has appeared directly or indirectly in BPSC questions.
Pollution: The introduction of substances or energy into the environment at a rate faster than the environment can naturally disperse, dilute, decompose, recycle, or store them in a harmless form. Pollution can be classified by the medium affected (air, water, soil) or by the type of contaminant (chemical, biological, physical, plastic).
Particulate Matter (PM): A mixture of solid particles and liquid droplets suspended in air. PM is classified by aerodynamic diameter. PM10 (coarse particles, ≤10 µm) can reach the upper respiratory tract. PM2.5 (fine particles, ≤2.5 µm) can penetrate deep into the lungs and enter the bloodstream, making it the most hazardous to human health. Tested in BPSC.
Biological Oxygen Demand (BOD): The amount of dissolved oxygen required by aerobic microorganisms to decompose organic matter in a water sample over a specified time (usually 5 days at 20°C). Higher BOD indicates higher organic pollution. It is the primary parameter for measuring organic pollution in water bodies. Tested in BPSC.
Eutrophication: The process by which a water body becomes enriched with nutrients (primarily nitrogen and phosphorus), leading to excessive growth of algae and aquatic plants. When algae die, their decomposition consumes oxygen, creating hypoxic or anoxic conditions that kill fish and other aquatic life. The primary cause is agricultural runoff containing fertilisers. Tested in BPSC.
National Air Quality Index (AQI): A public reporting tool that converts concentrations of eight pollutants into a single index value (0–500) with colour-coded health advisories. The eight monitored parameters are: PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃, and Lead (Pb). Methane (CH₄) is not included. Tested in BPSC.
National Ambient Air Quality Standards (NAAQS): Legally enforceable limits for ambient air pollutants set by the Central Pollution Control Board (CPCB) under the Air (Prevention and Control of Pollution) Act, 1981. The 2009 NAAQS revised earlier standards. For PM2.5, the annual average limit is 40 µg/m³ and the 24-hour average limit is 60 µg/m³. Tested in BPSC.
Non-biodegradable material: A substance that cannot be broken down by natural biological processes (e.g., bacteria, fungi) into simpler, harmless compounds within a reasonable time. Plastics, especially polyethylene, are classic examples. They persist in the environment for centuries, causing soil and water pollution. Tested in BPSC.
Chemical fertiliser overuse: The excessive application of synthetic nitrogen, phosphorus, and potassium (NPK) fertilisers beyond what crops can absorb. This leads to soil acidification, nutrient imbalance, reduced microbial diversity, and runoff that causes eutrophication. In North Bihar, intensive agriculture has made this the primary driver of soil degradation. Tested in BPSC.
Industrial effluents and untreated sewage: The two largest sources of water pollution in Indian rivers. Industrial effluents contain heavy metals, toxic chemicals, and organic compounds. Untreated domestic sewage introduces pathogens, organic matter, and nutrients. Together, they are the major cause of pollution in the Ganga river basin. Tested in BPSC.
These core concepts form the backbone of the subtopic. Every subsequent section will build on them, so ensure you can define each term in your own words before moving on.