Final answer:
Nineteenth-century industrial cities were dirty due to waste, poor sanitation, and air pollution caused by industrial activities.
Step-by-step explanation:
In the nineteenth century, industrial cities were dirty due to several factors. One major source of dirt was waste, including factory waste, human waste, and animal waste such as horse manure. With the growth of cities, public transportation became necessary, leading to the use of horse-drawn streetcars and omnibuses, which added to the amount of waste in the streets.
Poor urban planning and lack of regulation contributed to the dirty conditions. Open sewers ran through the streets, spreading unchecked human, animal, and industrial waste. This lack of sanitation led to the spread of diseases like cholera, tuberculosis, and typhoid. Additionally, coal burning for steam power and electricity generated air pollution, covering surfaces with soot.
In conclusion, the reasons nineteenth-century industrial cities were so dirty included the presence of waste, poor sanitation, and air pollution resulting from industrial activities.