smog – n. cloudy air caused by air pollution
emission – n. the act of producing or sending out something from a source
capacity – n. the ability to hold or contain people or things
resident – n. someone who lives in a particular place
alert – n. a public warning or notice
translator – n. a person who changes words in one language to another
hydroelectric – adj. of or relating to the production of electricity by using machines powered by moving water
cheap – adj. least costly