Environmental Pollution and EIA

Air and air pollution

Clean dry air is about 78% nitrogen, 21% oxygen, 0.93% argon, about 0.04% carbon dioxide and traces of other gases, plus variable water vapour.

Air pollution is the presence in the atmosphere of substances in concentrations and durations that cause harm to human health, living organisms, materials or the environment. In India it is legally defined under the Air (Prevention and Control of Pollution) Act, 1981.

Sources and classification

Particulate matter terms: dust (solid particles from mechanical processes), fumes (fine solids from condensation of vapours, e.g. metal fumes), smoke (fine particles from incomplete combustion), mist (liquid droplets), fly ash (fine ash from combustion), PM₁₀ (aerodynamic diameter ≤ 10 µm — inhalable) and PM₂.₅ (≤ 2.5 µm — fine, penetrates deep into the lungs).

Major pollutants and their effects

Indoor air pollution — from cooking with biomass and kerosene, tobacco smoke, radon, formaldehyde and VOCs — is a major health risk, especially for women and children in rural households.

Bhopal gas tragedy (1984) — leak of methyl isocyanate (MIC) from a pesticide plant; one of the worst industrial disasters, which led to stronger environmental and liability laws in India.

Global and regional issues

Acid rain

SO₂ and NOx oxidise to sulphuric and nitric acids that fall with rain (pH below about 5.6). Effects: acidification of lakes and fish kills, forest damage, leaching of soil nutrients, corrosion of buildings and monuments (e.g. marble cancer concerns for the Taj Mahal).

Greenhouse effect and global warming

Greenhouse gases — CO₂, CH₄, N₂O, CFCs/HFCs, water vapour, tropospheric ozone — absorb outgoing infrared radiation and warm the earth. Increasing concentrations cause global warming, sea-level rise, changing rainfall patterns and extreme events. Gases differ in global warming potential (GWP) relative to CO₂.

Ozone layer depletion

Stratospheric ozone absorbs harmful UV-B radiation. CFCs, halons, carbon tetrachloride, methyl chloroform release chlorine and bromine that destroy ozone (the Antarctic ozone hole). Controlled under the Montreal Protocol (1987); the Kigali Amendment (2016) phases down HFCs (potent greenhouse gases). Ozone thickness is measured in Dobson units.

Smog

National Ambient Air Quality Standards (NAAQS, 2009)

Notified by CPCB for 12 pollutants (values for industrial, residential, rural and other areas):

(Stricter annual limits apply to SO₂ and NO₂ in ecologically sensitive areas.)

Air Quality Index (AQI)

India's National AQI (launched 2014) combines up to eight pollutants (PM₁₀, PM₂.₅, NO₂, SO₂, CO, O₃, NH₃, Pb) into one number; the overall AQI is the highest sub-index.

National Clean Air Programme (NCAP) — launched in January 2019 to reduce particulate pollution in non-attainment cities through city action plans (targets have been revised over time; check current MoEFCC documents).

Air pollution meteorology

Lapse rates and stability

• Environmental lapse rate (ELR) — actual rate of temperature decrease with height.
• Dry adiabatic lapse rate (DALR) — cooling of a rising dry air parcel ≈ 9.8 °C per km (about 1 °C per 100 m).
• Wet adiabatic lapse rate — lower (about 6 °C per km) due to latent heat release.

Inversions: radiation inversion (clear calm nights — ground cools rapidly; common in winter mornings), subsidence inversion (sinking air in high-pressure systems; persistent, at elevation).

Maximum mixing depth (height) — the height up to which convective mixing occurs; low mixing heights (winter nights and mornings) cause high pollution levels.

Plume behaviour

Dispersion and stack height

Plume rise $\Delta h$ increases with exit velocity and gas temperature (buoyancy) — e.g. Holland's and Briggs' formulas.

What is EIA?

Environmental Impact Assessment (EIA) is a systematic process to identify, predict, evaluate and mitigate the likely environmental, social and other relevant effects of a proposed project before decisions are taken and commitments made.

Objectives

1. Integrate environmental considerations into project planning and decision-making.
2. Identify adverse impacts early and propose mitigation measures.
3. Examine alternatives — sites, technologies, designs, including the "no project" option.
4. Involve the public and affected communities.
5. Provide a basis for environmental management and monitoring during construction and operation.

Benefits

Avoids costly mistakes and later remedial expenditure; reduces environmental damage and conflicts; improves project design; ensures compliance with laws; promotes sustainable development and transparency.

Evolution

• USA — National Environmental Policy Act (NEPA), 1969 — first to require environmental impact statements for federal actions.
• India: environmental appraisal of river valley projects began in the late 1970s; the EIA Notification of 1994 under the Environment (Protection) Act, 1986 made environmental clearance mandatory for listed projects; it was replaced by the EIA Notification, 2006 (amended many times since). A draft EIA Notification, 2020 was published for comments.

EIA Notification, 2006

Categorisation of projects

Category B projects are treated as Category A if located (fully or partly) within specified distances of protected areas, critically polluted areas, eco-sensitive areas or inter-state/international boundaries (the general condition).

The schedule lists sectors such as mining, thermal power, river valley and hydroelectric projects, nuclear projects, industries (cement, metallurgical, chemical, refineries, pesticides, etc.), infrastructure (highways, ports, airports, industrial estates), and building and construction projects above specified thresholds.

Stages of environmental clearance (for new projects)

1. Screening — (Category B) deciding whether B1 or B2.
2. Scoping — the EAC/SEAC determines detailed and comprehensive Terms of Reference (ToR) for the EIA study (standard ToRs also exist for many sectors).
3. Public consultation — (a) public hearing at or near the project site conducted by the State Pollution Control Board, and (b) written responses from concerned persons; certain projects (e.g. B2, expansion of roads within limits, building projects, projects in notified industrial estates) are exempt.
4. Appraisal — detailed scrutiny of the final EIA/EMP report and public consultation outcomes by the EAC/SEAC, which recommends grant (with conditions) or rejection.

The regulatory authority then decides on Environmental Clearance (EC) with specific and general conditions. The notification prescribes time limits for scoping, appraisal and communication of decisions.

Post-clearance monitoring

• Project proponents submit half-yearly compliance reports on EC conditions.
• Regional offices of MoEFCC and SPCBs monitor compliance; violations can lead to penalties or revocation.
• EC is valid for a specified period within which construction/operations must begin; expansion or modernisation needs fresh or amended clearance.

The EIA process

1. Project description — objectives, location, layout, technology, raw materials, resource use, waste generation.
2. Baseline environmental status — existing conditions of the study area (typically a 10 km radius for many industrial projects) — generally based on primary data for one season other than monsoon plus secondary data.
3. Impact identification — which environmental components will be affected and how (direct, indirect, cumulative; short-term, long-term; reversible, irreversible; beneficial, adverse).
4. Impact prediction — magnitude and extent using models (air dispersion, noise propagation, water quality, groundwater, traffic), analogues and expert judgement.
5. Impact evaluation — significance of impacts against standards, carrying capacity and public concern.
6. Mitigation measures — avoid, minimise, rectify, reduce or compensate adverse impacts.
7. Analysis of alternatives — sites, technologies, "no project".
8. Environmental Management Plan (EMP) — mitigation actions, institutional set-up, budget, and environmental monitoring programme.
9. Risk assessment and disaster management plan — for hazardous industries.
10. Public consultation and documentation — the EIA report (Environmental Impact Statement) with an executive summary.
11. Decision-making and post-project monitoring and audit.

Environmental components studied