Urban problems are issues that arise in cities due to population growth, industrialization, and other factors. Common urban problems include SPRAWL, SMOG, slums, CRIME, and NOISE. SPRAWL is the uncontrolled expansion of urban areas, often resulting in a lack of infrastructure and services. SMOG is a type of air pollution caused by the burning of fossil fuels. Slums are areas of poverty characterized by overcrowding, inadequate housing, and poor sanitation. CRIME is any illegal activity that threatens the safety of citizens. NOISE is unwanted sound that can be disruptive to daily life. All of these issues can have a negative impact on the quality of life in cities.