Pollution, also called environmental pollution, the addition of any substance (solid, liquid, or gas) or any form of energy (such as heat, sound, or radioactivity) to the environment at a rate faster than it can be dispersed, diluted, decomposed, recycled, or stored in some harmless form.

The major kinds of pollution, usually classified by environment, are

1. Air pollution.
2. Water pollution.
3. Land pollution.

Modern society is also concerned about specific types of pollutants, such as noise pollution, light pollution, and plastic pollution.

Pollution of all kinds can have negative effects on the environment and wildlife and often impacts human health and well-being.

Air pollution results from the introduction of a range of substances into the atmosphere from a wide variety of sources. It can cause both short term and long term effects on human health, wildlife, but also on the wider environment. Pollution is the process of making land, water, air or other parts of the environment dirty and not safe or suitable to use. This can be done through the introduction of a contaminant into a natural environment, but the contaminant doesn't need to be real. Things as simple as light, sound and temperature can be considered pollutants when introduced artificially into an environment.

Land can become polluted by household garbage and by industrial waste. Organic material was the largest component of the garbage generated. Commercial or industrial waste is a significant portion of solid waste. Water pollution happens when chemicals or dangerous foreign substances are introduced to water, including chemicals, sewage, pesticides and fertilizers from agricultural runoff, or metals like lead or mercury.

Air pollution occurs when things that aren't normally there are added to the air. A common type of air pollution happens when people release particles into the air from burning fuels. This pollution looks like soot, containing millions of tiny particles, floating in the air. 

Another common type of air pollution is dangerous gases, such as sulfur dioxide, carbon monoxide, nitrogen oxides and chemical vapors. These can take part in further chemical reactions once they are in the atmosphere, creating acid rain and smog. Other sources of air pollution can come from within buildings, such as secondhand smoke. 

Finally, air pollution can take the form of greenhouse gases, such as carbon dioxide or sulfur dioxide, which are warming the planet through the greenhouse effect.

There are many different effects of air pollution within a city such as ArRiyadh; from those affecting people’s health to those that affect the environment or buildings that people work and live in. The type of pollutant will have different effects, however in the majority of cases, the pollutant being either a gas or a small particulate can travel from the source, and thus is not restricted to those next to or within the vicinity of the source of the pollution, though they may be subject to higher concentrations.

Short-term moderate air pollution tends to have a lesser effect on those who are young or healthy, and is unlikely to have any long-term effects. However, children, the old and those with an over-riding health condition can be effected by these moderate levels of air pollution, such as shortness of breath, increased susceptibility to infection and irritation to the lungs (seen as coughing for example).

Longer-term elevated pollution levels (even at moderate concentrations) can have more serious effects, potentially leading to respiratory illnesses such as asthma, or more serious conditions including heart disease, strokes or even cancer. It was estimated by the World Health Organisation (WHO, 2014) that there was 3.7 million premature deaths in 2012 caused by elevated particulate levels, and that of these deaths: “80%... were due to ischaemic heart disease and strokes, 14% of deaths were due to chronic obstructive pulmonary disease or acute lower respiratory infections; and 6% of deaths were due to lung cancer.”
Air pollution can also cause damage to plants and animals, affecting biodiversity and crop yields. Additionally it can be detrimental to buildings; particulates can cause the blackening of buildings, acidic gases can contribute to damage to both buildings and crops, ozone effects plant yields and some animals. Air pollution is also known to have had a seriously detrimental effect to the planet’s health with global warming being largely caused of burning of fossil fuels and thus the production of CO2.
 

Short-term increases in PM levels -associated with acute health effects:

• increased use of medication (e.g. asthma inhalers),
• days off work and days with restricted activity,
• hospital admission for lung and heart diseases,
• risk of death from asthma, COPD, heart disease,
• Impacts identified at progressively lower PM concentrations.
• Probably no lower threshold limit for adverse effects.

Long term exposure to particulates –PM

• increased deaths from all causes, heart attack, chronic lung disease, stroke and lung cancer.
• Estimated reduction in average life expectancy of 3-4 months in Scotland (COMEAP 2010)
• Estimated (statistically) as equivalent to approx. “excess” deaths levels of anthropogenic PM _2.5 (assumes PM _2.5 is the sole cause of death –but it isn’t!)
• NB-interpret estimates of “excess deaths caused by AP” with caution –not actual deaths (cf. RTA deaths).

Additional effects of long term PM exposure -emerging evidence

• less strong but associations also identified with:
• adverse birth outcomes, low birth weight,
• childhood asthma,
• cognitive dysfunction –dementia,
• chronic metabolic disease eg diabetes