We know a lot more about how kids' nervous systems, immune systems, et cetera actually develop, and that has raised concerns about vulnerabilities. Third, some kinds of ailments are on the increase, and the environment MAY be a factor. Yes, to the extent it has been measured, more kids ARE getting asthma. One problem is that, as a nation, we keep no national statistics on how many kids have asthma. But some states do collect it and that, with emergency room surveys, shows a huge increase, perhaps doubling over the past 15 years.
Some evidence seems to point to environmental factors, however.
For example, hospitalizations for asthma spike around bad air quality days. Inner city kids have much higher rates of asthma. You mentioned inner city kids having higher asthma rates and minority groups living in polluted areas. But there are some problems that are worse in pretty remote areas. For example, Inuit populations that eat lots of fish, even in remote locations, often have high mercury levels and problems with kids' health because we've dumped mercury all over the oceans.