Answer: man-made surfaces
Step-by-step explanation:
The urban heat island effect is as a result of the modification of land surfaces. The urban heat island effect results in a reduction in the air quality as there'll be an increase in pollutants.
The urban heat island effect occurs from the fast heating and slow cooling of man made surfaces. When natural land cover is being replaced with dense concentrations of buildings, pavement, etc which retain heat, the results in a rise in the cost of energy and air pollution.