Pollution is the introduction of harmful substances or contaminants into the environment. It can come from human activity, such as industry, transport and farming, or from natural sources, such as volcanoes and wildfires. Pollution is one of the biggest environmental threats to human health, and air pollution alone is linked to millions of early deaths around the world every year.
Types of Pollution
The main types of pollution include air pollution, water pollution, land or soil pollution, noise pollution and light pollution. Each can harm people, wildlife and ecosystems in different ways.
Air Pollution
Air pollution comes mainly from burning fossil fuels in vehicles, power stations, industry and homes. Pollutants such as fine particulate matter and nitrogen dioxide can damage our lungs and heart. Burning fossil fuels also releases carbon dioxide, the main greenhouse gas driving climate change.
Acid Rain
Acid rain is caused mainly by sulphur dioxide and nitrogen oxides released when fossil fuels are burned. These gases react with water in the atmosphere to form acids, which fall as rain and can damage forests, lakes, wildlife and buildings.
Land and Water Pollution
Land and water can be polluted by industrial waste, landfill, spills and the run-off of fertilisers and pesticides from farmland. Contaminated land may need specialist clean-up before it can be safely used again. For more details on Remediation Contractors, visit a site like Soilfix
Why It Matters
Because pollution can build up in soil, water and the food chain, reducing it is important for the health of people and the planet. Scientists around the world agree that cutting pollution and greenhouse gas emissions is one of the biggest challenges we face.
Related: What are the effects of groundwater pollution?
Indoor air and cutting your own exposure
Air that looks clean is not necessarily healthy. The finest particles, often called PM2.5, are far too small to see, and they can get past the body’s natural defences, travelling deep into the lungs and even into the bloodstream, where they are linked to heart, lung and brain problems. Children, older people and anyone with a heart or lung condition are especially vulnerable. Pollution is also not only an outdoor problem. Cooking, wood burners, candles and some cleaning products all affect the air indoors, and the two mix as air moves in and out of buildings.
There are simple ways to reduce your own exposure. Avoid walking along busy roads at rush hour where you can, and choose quieter back streets or green spaces for exercise. Using the car less helps both you and everyone around you. Never burn household or garden waste, as the smoke is harmful, and ventilate well when cooking or using a stove.
How acid pollution damages buildings
Acid rain does not only harm forests and lakes; it has also left its mark on our towns and cities. Sulphur dioxide and nitrogen oxides from burning coal and oil react with water to form dilute acids that attack building materials. Limestone and marble are particularly vulnerable, as are zinc, carbon steel, paint and some plastics. On older buildings, the damage shows as carvings that have lost their sharp detail and as black crusts in sheltered corners where rain does not wash the stone.
Pollution reaches buildings in two ways. Wet deposition is acid carried in rain, snow or mist, which can fall far from the source. Dry deposition is when gases and particles settle directly on surfaces, which mainly affects buildings near busy roads and industry. Even though sulphur pollution has fallen a long way, the problem has not gone away: stone that absorbed sulphur over many years has a chemically changed surface, and as rain washes that layer off, the stone beneath continues to wear away.
How pollution damages historic stonework
Air pollution affects buildings as well as people. As early as 1660, observers noted that London’s air was discolouring and degrading its buildings. Carbon dioxide combines with water in the atmosphere to form carbonic acid, while sulphur dioxide and nitrogen oxides produce sulphurous and nitric acids, which fall as acid rain and slowly attack masonry. Vehicle exhaust has also left residue on city stonework over many decades.
Until the 1950s, burning coal at home created London’s great smogs, a dense blanket of smoke and sulphur dioxide. On limestone, sulphur dioxide reacts with the stone to form a black crust, a process called sulphating, which can make the surface peel away. Rain-washed surfaces tend to roughen instead, and marble can take on a sugary texture.
Not all damage is man-made. Coastal air carries more salt, and salt crystals forming inside the tiny pores of stone exert enough pressure to cause flaking, blistering and honeycomb weathering.