Contemporary Urban Environments 6


Particulates are tiny pieces of solids and tiny droplets of liquids floating in the air.

More particulates are found in urban areas than in rural areas. The concentration of particulates in urban areas is around 10-40 pg/m^3, compared to less than 10 pg/m^3 in rural area.

Sources of particulates include:

  • Vehicle exhausts - they produce very fine particulates. About 80% of fine particulates in urban areas are from vehicle exhausts.
  • Burning of refuse, cigarettes and fuel, e.g. coal - this produces both fine and coarse particulates.
  • Construction, mining and quarrying - these activities produce coarse particulates.
  • Plants and moulds - also generate coarse particulates.

Particulates can cause health problems. Coarser particulates are usually filtered out by the nose and throat, but finer particulates less than 10 pm in diameter can enter the lungs. PM10 could cause or make worse problems like asthma, bronchitis, lung cancer and heart disease.

Pollutants, such as nitrogen oxides, sulfur oxides and hydrocarbons, come from burning fossil fuels.

When these pollutants come into contact with sunlight, the UV light causes them to break down into harmful chemicals which form photochemical smog.

Photochemical smog is a problem in many cities, e.g. Los Angeles, Beijing, Mexico City and Barcelona. It's more common in places with hot and sunny climates because there's more sunlight.

These locations often have a temperature inversion, which keeps the pollutants at ground level.

Photchemical smog is linked to health problems, such as breathing difficulties, respiratory disorders and headaches.

Lots of cities have tried to reduce pollution by reducing traffic. There are various ways that this can be done:

Congestion charging:

  • People are charged if they use their vehicles in certain places at certain times.
  • This reduces pollution by reducing road traffic. In Central London, congestion charging reduced traffic and emissions in the congestion zone by around 15% in its first year…


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