The city and surrounding areas suffer from various environmental problems such as water pollution from factories, air pollution from factories and vehicles, dust from mines, litter, and noise pollution from overcrowding. Soweto has poor air quality due to coal burning and high water pollution levels. The Dutch established the first European colony in 1652 which grew to about 15,000 people by the late 1700s. Johannesburg is the largest city and economic center of South Africa with a population of around 4 million people, including many illegal immigrants. Gold mining is a key industry.