How does urbanisation pose a threat to environment?

Urbanisation always takes place at the cost of ecology and environment.
(i) Growing demand for space required for factories, houses and institutions, are provided only by clearingforests,cuttingtreesandflatteningground. This spoils the natural environment and habitat.
(ii) Large quantities of waste products polluted air and water while excessive noise caused noise pollution both in London as well as Bombay.
(iii) Widespread use of coal in homes and industries, smoke from chimneys of factories and homes throw black smoke into the atmosphere causing breathing problems and diseases. Tuberculosis was common disease among factory workers in big industrial cities in 19th century.
(iv) Increase in population leads to further pollution. Slums pose great threat to public health - Lack of sanitation leads to air and water pollution.