In the study of urban ecology in Baltimore and Phoenix, how do the two cities differ in their citizens' exposure to toxic chemicals? In the study of urban ecology in Baltimore and Phoenix, how do the two cities differ in their citizens' exposure to toxic chemicals? Baltimore has taken a zero-tolerance approach to polluters, so its citizens are much less exposed to toxic chemicals than the citizens of Phoenix. Phoenix has largely eliminated exposure to toxic chemicals, whereas the citizens of Baltimore suffer from extreme exposure to such hazards. Minorities in both cities are more likely to be exposed to such hazards than white citizens, but minorities in Phoenix are provided with better health care to offset the costs related to exposure. In Phoenix, ethnic minorities are more likely to be exposed to such hazards, whereas in Baltimore, those living in working-class white neighborhoods are more likely to be exposed. Baltimore was built before building codes and zoning laws prohibited building homes on contaminated sites, so all of the citizens of Baltimore are exposed to high levels of toxic chemicals, whereas Phoenix has been built more recently and so