Answer:
Regulations make it more difficult to produce
Natural environment has the ability to gather some pollutants yet if too much then the environment could no longer handle it. A leaky sewage can pollute an aquifer with I. arsenic as the contaminant. Arsenic is a metalloid existing in the Earth's crush. Exposure is natural yet can be aggravated by the human activities.
The body is divided into several different systems. Do you need examples of the systems?
Two problems would be overcrowding which could potentially result in rapid disease outbreak and lack of resources to go around to everyone that inhabits the urban area
two opportunities would be an opportunity for job specialization and an opportunity for fleeing of racial persecution as their is lots of diversity in urban areas
