Urbanization = pollution

Air Pollution Urban air pollution is considered one of the most visible impacts of urbanization on the environment (Fang et al. 2019). Due to various anthropogenic activities in urban areas, the air of the metropolitan regions gets polluted, i.e., large number of auto- mobiles and industries emitted various air pollutants such as carbon dioxide, hydro- carbons, oxides of sulfur and nitrogen, vapor of organic chemicals, particulate matter and toxic chemicals, etc. (Haque and Talukder 2021). Photochemical smog in Los Angeles is one famous example of urban air pollution, it occurs due to the reaction of sunlight with exhaust from power plant and automobiles (Goodsite et al. 2021). The main component of these smokes includes ozone, oxides of nitrogen, and VOCs. These pollutants also affect the health of humans (Manisalidis et al. 2020). Further- more, more than 80% of people living in these urban areas are exposed to air quality levels that exceed the World Health Organization (WHO) guideline limits, where the low- and middle-income countries were suffering from the highest exposures of outdoor air pollution (WHO 2021). 9.3.1.2 Noise Pollution Unwanted and excessive sound in any area is called as noise pollution. In urban areas, noise pollution sources include vehicles, industries, social function, and automobiles (Bello et al. 2019). Among these sources, vehicle traffic in urban areas is considered the primary source of noise pollution. An ancient city of India, Kolhapur, is now rapidly industrialized and urbanized, and it is suffering from severe noise pollution problems. A study has been carried out in Kolhapur to assess the daytime noise quality in five critical zones: (1) Education, (2) Industrial-cum- residential, (3) Commercial-cum-residential, (4) Recreational, and (5) Silence zone. For all zones, study computed L10, L50, and L90 noise pollution indices, noise climate (NC), equivalent continuous noise level (Leq), noise pollution level (Lnp), and noise exposure index (NEI). Results of the study indicate that the highest Leq of 72.25 dBA was found in industrial-cum-residential zone followed by 64.47 dBA in commercial-cum-residential zone, in educational zone observed was 63.71 dBA, 53.66 dBA in recreational zone and silence zone found 42.84 dBA. Leq observed that educational zones were above the statutory limits, while others were marginally below. According to the noise assessment study, Kolhapur is experienc- ing alarming levels of noise pollution (Hunashal and Patil 2012). Furthermore, noise pollution in urban areas causes significant risk to human health and affects the life of other organisms, i.e., wildlife organisms mainly depend on sound for their commu- nication and behavior, but excessive noise breaks their contact and affects their behavior (Yuan et al. 2019). 9 Urbanization Trends, Climate Change, and Environmental Sustainability 157 9.3.1.3 Water Pollution There will be an 80% increase in urban water demand by 2050. In India and China, nearly half of the 4 billion people facing severe water scarcity do so for at least 6 months out of the year. The Chennai (India) drinking water system ran dry earlier this year (Mekonnen and Hoekstra 2016; Vanham et al. 2018; Flörke et al. 2018) and Cape Town (Africa) ran out of drinking water in 2018 (Mekonnen and Hoekstra 2016; Vanham et al. 2018). Worldwide, over 80% of wastewater is not treated appropriately before being released into the environment (Connor et al. 2017). Due to rapid industrialization and urbanization, many waste disposal occurs in the river and lakes. Besides this, the discharge of untreated sewage waste from mega cities and towns into the water bodies causes water pollution (Jayaswal et al. 2018). As per the CPCB data, about 38,254 million L/day sewage is generated from class I and class II cities of the country. Treatment capacity found only for 11,787 million L/day sewage (Olds et al. 2018). So, the untreated sewage dump into water bodies increases the river’s pollution load and other water bodies (Xu et al. 2019). Water pollution caused by urbanization also affects the aquatic ecosystem. Unplanned urbanization also leads to the scarcity of fresh water by destructing the path of natural water flow and also causes the hydrological changes (Mishra et al. 2020a). The dumping of solid waste on land without treatment causes leaching of harmful material to the river water and groundwater which cause water pollution (Nai et al. 2021). A case study of city Hyderabad, one of India’s fastest growing megacities with a significant impact on the environment. A city’s uncontrolled growth and densifica- tion severely affect its surface and groundwater resources. A better understanding of urban growth’s impact on the environment is necessary to prevent future deteriora- tion of these essential resources and recover them. A study found that rapid urban- ization of Hyderabad has led to an increase in the need for fresh water for domestic and industrial use. The use of groundwater was increased as a result of this increase in demand. Furthermore, a quality analysis found that the groundwater samples did not meet the BIS and WHO drinking water standards. In addition, heavy metals like zinc, lead, chromium, iron, etc. were found in the water samples, indicating that industrial effluent had percolated into the aquifer. This study also proven that the sewage water and residential area had also contributed in recharging grown water. The study concluded that the urban growth had made the groundwater resources more vulner- able and in many cases it had been affecting it very severely (Wakode et al. 2014),