First, right out of the gate, take the core of this story with a grain of salt, (or perhaps half a shaker full), because it was reported on Fox News.
According to Fox news, quoting the director of the Radiation and Public Heath Project, Philadelphia is experiencing dangerously elevated levels of both radioactivity and iodine in its drinking water. At the same time, there has been a "spike" in infant mortality in Philadelphia.
I place the word "spike" in quotes for a good reason. The infant mortality per week "has increased by 48%", Fox breathlessly reports. Well, OK, 48% is an alarming increase. Then we discover that this translates to an increase from 5 per week to 7.5 per week. We'll pass over the obvious half-a-baby gags and references to the Wisdom of Solomon.
The question is, does this constitute a large enough statistical sample to be valid? I don't know, do you? If you have some professional competence in any applicable field, by all means please comment.
I do know that the subject of infant mortality is a shamefully embarrassing one for the USA, and I definitely intend to visit the topic in full very soon.