Brain cancer is now the leading cause of children deaths in the US? Is it the water they are drinking?

No. It is now the leading type of cancer to cause death in children, not the leading cause of death of children.  That is due primarily to a continuing downward trend since the 70s of fatal childhood cancers.  The number dropped 20% between 1999 and 2014, and while brain cancer deaths increased slightly during that time, lukemia, which had been the most common fatal childhood cancer, dropped significantly.  There were 534 children that died of brain cancer in 2014.  

http://reuters.com/article/idUSKCN11M09I

@Bozette, thanks for this article. I was getting my news from the radio. This is how they reported it, which prompted my surprise on this question. I also like fact-checking the news.

Perhaps modified food has contributed or something they spray on the food, and bad water. 

Very scary report for sure.