Describe air pollution with its health effects and control.

Sources, Pollutants and Health Effects

• The sources divide into outdoor (ambient) and indoor (household), and the second is the one most often neglected and the one that matters most in rural India
• Outdoor sources — vehicles; industry and thermal power stations; construction and road dust; crop residue (stubble) burning, a major seasonal contributor in north India; waste burning; brick kilns and diesel generators; and natural sources such as dust storms and forest fires
• Indoor sources — biomass fuel — wood, dung cake, crop residue and coal — burnt on inefficient stoves in unventilated kitchens; tobacco smoke; mosquito coils and incense; kerosene; building materials and radon; and damp and mould
• The major pollutants and their effects:
• Particulate matter — PM10 (coarse, deposited in the upper airway) and PM2.5 (fine, reaching the alveoli and entering the bloodstream)
• PM2.5 is the pollutant most closely linked to mortality, and its ability to cross into the circulation is why air pollution causes cardiovascular disease and not merely respiratory disease — a point that surprises students and is central to the modern understanding
• Sulphur dioxide — from coal and fuel oil, causing bronchoconstriction and mucosal irritation, and contributing to acid rain
• Oxides of nitrogen — chiefly from vehicles, causing airway inflammation and forming ozone
• Ozone — a secondary pollutant formed by sunlight acting on nitrogen oxides and volatile organic compounds, causing airway inflammation and reduced lung function; it peaks in the afternoon on sunny days
• Carbon monoxide — binding haemoglobin with far greater affinity than oxygen to form carboxyhaemoglobin, causing tissue hypoxia, headache and, at high concentration, death
• Lead, now much reduced by the removal of lead from petrol, which was one of the clearest public health successes of environmental regulation
• Others — volatile organic compounds, benzene, polycyclic aromatic hydrocarbons and asbestos
• The health effects, grouped by system:
• Respiratory — acute respiratory infection in children; asthma exacerbation; chronic obstructive pulmonary disease; reduced lung growth in children; and lung cancer, air pollution being classified as a Group 1 human carcinogen
• Cardiovascular — myocardial infarction, stroke, arrhythmia, hypertension and heart failure; and more deaths are attributable to the cardiovascular effects than to the respiratory ones
• Perinatal and paediatric — low birth weight, preterm birth and stillbirth
• Other — diabetes, cognitive decline and dementia, and adverse effects on mental health
• The indoor air pollution problem is specifically Indian and rural — a woman cooking on a biomass stove in an unventilated kitchen may be exposed to concentrations far exceeding any outdoor standard, for hours daily, with young children carried alongside her
• It is the reason for COPD in Indian women who have never smoked, and for a substantial share of childhood pneumonia

Monitoring, Control and Programmes

• Monitoring and standards — the national ambient air quality standards prescribe limits for PM10, PM2.5, sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide, lead, ammonia, benzene and others
• The air quality index (AQI) converts several pollutants into a single number with colour-coded categories from Good to Severe, which is intended for public communication rather than for scientific use
• Its value is that it tells an ordinary person what to DO on a given day, which a table of micrograms per cubic metre does not
• The control measures, which should be organised by source rather than listed:
• For vehicles — emission standards (India has moved to BS-VI); cleaner fuels, including the removal of lead and the reduction of sulphur, and the promotion of CNG; electric vehicles; public transport and non-motorised transport; fitness certification and pollution-under-control checks; and traffic management
• For industry — siting away from residential areas and with regard to prevailing winds; tall stacks, which disperse rather than remove the pollutant and therefore export the problem; control equipment such as cyclones, bag filters, electrostatic precipitators and scrubbers; cleaner processes and fuel substitution; and continuous emission monitoring
• For indoor air, which is where the greatest health gain lies for India — clean cooking fuel, chiefly LPG, which is the rationale for the pradhan MANTRI ujjwala YOJANA providing free connections to poor households
• A caution about Ujjwala should be given — providing the connection is not the same as sustaining refills, and many households revert to biomass because the recurring cost of a cylinder is unaffordable, which is the same "construction is not use" lesson in a different programme
• Also — improved chulhas with chimneys; kitchen ventilation and separation of the kitchen from the living area; keeping small children away from the cooking area; electric induction cooking; and smoke-free homes free of tobacco
• For agriculture and waste — alternatives to stubble burning, including mechanical residue management and crop diversification; and prohibition of open waste burning with proper waste management instead
• General measures — urban planning and zoning; green belts and tree planting; dust suppression at construction sites; and public awareness and advisories on high-pollution days
• The legal and programme framework in India — the air (Prevention and Control of Pollution) act, 1981; the environment (Protection) act, 1986; the central and state pollution control boards; the national green tribunal; and the national clean air programme (NCAP), which sets city-specific reduction targets for non-attainment cities
• The advice to an individual on a high-pollution day — avoid outdoor exercise, particularly near busy roads and in the afternoon when ozone peaks; keep windows closed at peak times; use an N95-type mask if outdoor exposure is unavoidable, noting that a cloth or surgical mask does not filter PM2.5; and protect children, the elderly and those with heart or lung disease particularly
• The honest conclusion — individual protective measures are marginal; air pollution is a problem of energy, transport, agriculture and urban policy, and can only be solved there
• It kills more through the heart than the lungs, since PM2.5 crosses into the bloodstream from the alveoli
• The biggest Indian gain lies indoors, where biomass cooking exceeds any outdoor concentration for hours daily
• COPD occurs in women who never smoked, which is the clearest sign that the Western model does not fit here
• A cloth or surgical mask does not filter PM2.5, which is worth saying plainly when advising patients
• Tall stacks disperse rather than remove, exporting the pollutant rather than eliminating it
• A connection is not a refill; Ujjwala households revert to biomass when the recurring cylinder cost bites
• Ozone is secondary and peaks in the afternoon, formed by sunlight acting on nitrogen oxides and hydrocarbons
• Avoid outdoor exercise near busy roads, particularly in the afternoon when ozone is highest
• Air pollution is a Group 1 carcinogen, which places it alongside tobacco and asbestos in the classification
• Stubble burning is a major seasonal source in north India, and needs an agricultural rather than a health solution
• Removing lead from petrol worked, and is among the clearest successes of environmental regulation anywhere
• Carbon monoxide binds haemoglobin avidly, causing tissue hypoxia without any respiratory distress
• Air pollution causes low birth weight and preterm birth, which links it to the maternal and child programme
• Keep small children away from the cooking area, which is a free measure with a measurable effect on pneumonia
• The AQI exists to tell people what to do, which a table of micrograms per cubic metre does not
• NCAP sets targets for non-attainment cities, which makes the problem city-specific rather than national
• Individual protection is marginal; this is a problem of energy, transport and agriculture policy
• Electrostatic precipitators and scrubbers are the industrial control devices worth naming alongside bag filters
• Site industry with regard to prevailing winds, which is a planning decision that cannot be corrected later
• Improved chulhas with chimneys help where LPG is unaffordable, though they are second best
• Sulphur dioxide contributes to acid rain as well as causing bronchoconstriction directly
• PM10 lodges in the upper airway while PM2.5 reaches the alveoli, which is the whole basis of the distinction