By Rowland Benjamin

Air pollution is primarily the result of burning fossil fuels such as oil, gas and coal for energy. Power stations create a large proportion of the air pollution when they burn fossil fuels to produce electricity for industrial plants, machinery, homes and other requirements. Transport also creates a great deal of air pollution when it burns petrol, diesel, oil and gas. Other sources of air pollution include solvent evaporation, volcanic eruption, forest fires and agriculture.

The main pollutants are sulphur dioxide, nitrogen dioxides, carbon dioxide, carbon monoxide, hydrocarbons and volatile organic compounds (VOCs). These gases and vapours may cause serious environmental problems and health problems in humans. They may act alone or combined or they may react with the environment to produce other substances such as acid rain and ground level ozone.

For most of the twentieth century the industrial countries of Europe, Russia, Great Britain and the United States were the main polluters. But over the past twenty years they have exported a lot of their industrial production to India and China, set stricter emission limits on their manufacturing industry and used improvements in technology to cut emissions, particularly of sulphur dioxide from power stations. China and India are now the world’s largest polluters because they are the greatest consumers of coal. And as coal typically contains up to 3 percent sulphur they are the largest emitters of sulphur dioxide into the atmosphere. China were the biggest polluters, but since 2007 China has set stricter emission limits on industry and installed flue gas desulphurisation on its power plants. As a consequence, sulphur dioxide emissions in China fell by about 75 percent. In contrast, India’s emissions over this period (2007 to 2018) increased over by 50 percent and so India has overtaken China as the world’s top sulphur dioxide emitter.

Oxides of nitrogen are in vehicle emissions and in domestic and industrial emissions. The hydrocarbons and VOCs are given off as vapours from petrol, and industrial and household products containing solvents, such as paints. Road traffic is responsible for a third of hydrocarbon emissions and half of nitrogen dioxide emissions. Devices fitted to cars such as catalytic converters remove a large portion of the carbon monoxide, hydrocarbons, volatile organic compounds and nitrogen oxides from car exhausts, but they do not remove carbon dioxide - a greenhouse gas responsible for global climatic change.

The severity of air pollution depends upon the type and amount of pollutants emitted, their rate of dissipation by wind patterns, their interactions and how rapidly they break down.

Acid Rain

Acid rain is created when a mixture of gases - primarily sulphur and nitrogen oxides and hydrocarbons - react with sunlight, ozone and cloud water vapour in the atmosphere, and form sulphuric and nitric acid. These pollutants can be carried over long distances by wind, and be released in rain, mist or snow. Taller chimneys solved the problem of intense localised ground-level pollution only to create other problems many miles from the source. The pollution was transferred to other parts of the country, or to neighbouring countries. For years pollutants from Britain, Russia and former East Germany frequently ended up in Scandinavia. Pollution from the United States may end up in Canada.

Acid rain results in the destruction of forests and other plant life. It acts by washing vital nutrients out of the soil thus weakening the trees and limiting their growth. Even slight damage to a mature tree can be enough to kill it, because it reduces its resistance to extremes of weather, and also to fungi and pests. Damaged trees are usually too weak to ever recover.

During the past twenty-five years, there has been a marked deterioration in trees and a reduction in foliage. In addition, large areas of lichens, mosses and heather are also disappearing.

Over one million square kilometres of forests in Europe have suffered from the effects of acid rain. Millions of trees are dead, or dying. Similarly, forests in Canada are affected by acid rain created from air pollution produced in the United States of America.

Wildlife is also suffering from the effects of acidification. Acid rain reacts with the soil releasing aluminium and other metals. These are washed into rivers and lakes where they increase to levels that are toxic to fish and other freshwater life. A lake may reach an acid level of pH 5 or less if the local soil has inadequate buffering capacity (its ability to neutralise acid rain). At pH 5 fish life and frogs begin to disappear. By pH 4.5 almost all aquatic life has disappeared.

An increase in water acidity may cripple or kill one species, and through its loss in the food chain may eradicate an entire series of species. Complete cycles of nature are being broken – for example, a decrease in insect larva in streams results in less insects and fewer insect-eating birds, amphibians and fish, such as salmon and trout. Rare species of insects and soil micro-organisms are being eradicated by acid rain.

In many countries including Norway, Sweden, Scotland, Canada and the USA, large numbers of fish have died from aluminium which has been released into the water by acid rain. In Sweden there are lakes with hardly any fish remaining in them. This in turn has affected fish-eating birds such as the osprey, black or red throated diver, common tern and goosander. It has delayed recovery of rare animals such as the otter.

Aluminium also causes song birds such as the blue-throat, reed bunting and willow warbler to lay eggs with thin shells, reducing their breeding success year after year. Dead spawn in surface waters show that frogs and toads are also being eradicated.

Acid rain and air pollution damages human health, irritates eyes and aggravates conditions such as asthma and bronchitis.

Acid rain damages the stonework of buildings and monuments, many of which have great historical value. The Acropolis in Greece has suffered more damage from air pollution in the past 20 years than in the previous 2000 years. In India, the Taj Mahal is crumbling.

Ozone

Ground level or tropospheric ozone is an air pollutant which is found in the troposphere - the lowest layer of the atmosphere. This ozone - often termed "bad" ozone - is man-made and should not be confused with the ozone layer or stratospheric ozone which is naturally occurring, high up in the stratosphere.

Ground level ozone is formed by the action of sunlight on the oxides of nitrogen, hydrocarbons or volatile organic compounds (VOC). They combine with oxygen to form ozone during hot sunny days, and during cooler nights the ozone usually dissipates.

Ozone also originates from electrical discharges from printers and photocopiers. Electricians, electronic technicians and film projectionists are most at risk from its effects. Ozone is utilised in the chemical industry as an oxidising agent for the bleaching of paper, flour and sugar, the processing of some perfumes, drying printing inks, deodorising of feathers, treatment of industrial wastes drinking water and as a food disinfectant.

Ozone exposure may exacerbate existing respiratory conditions, reduce your lung function and capacity for exercise and cause chest pains, eye irritation and coughing. Young children and the elderly are most susceptible to the high levels of ozone encountered during the summer.

The corrosive nature of ozone may damage plants, and high levels of ozone may destroy agricultural crops and forest vegetation.

Carbon monoxide from vehicle emissions of and incomplete combustion causes headaches, nausea, drowsiness and poor mental alertness. When inhaled it combines with haemoglobin in the blood, preventing absorption of oxygen and resulting in asphyxiation, unconsciousness and death. Because it is odourless, the person may be unaware of it acting.

Throughout the world, millions of children have high levels of lead in their blood. Lead is present in paints, cosmetics and industrial emissions and is still used in petrol in many developing countries. Lead prevents young brains from developing, lowers intelligence and causes behaviour problems.

What you can do

Use public transport, walk or use a bicycle.

Keep your car tuned and use unleaded petrol.

Plant more trees to reduce carbon dioxide.

Join a direct action group such as Earth First! or Reclaim the Streets.

Buy water-based or low-solvent paints, glues, varnishes and wood preservatives. If you must use solvent-based paints, keep the lid on the tin as much as possible to prevent evaporation of hydrocarbons. Use a brush or roller rather than a spray. Avoid household products, which contain hydrocarbons. These include cleaning agents, furniture polish, fabric softeners, hairspray, nail varnish, shaving cream, car waxes and lubricants. Do not buy aerosol spray cans.

Try not to burn off waste, particularly during certain seasons. These will vary from country to country. Ask your local government, council or regulatory body.

Action on acid rain is most effective when undertaken in an international context. Lobby your politicians for better laws.

Links:

Kids page: Green Sowers Solutions for this problem

Bibliography

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