Here's an article describing a new study that describes how BPA a chemical that is present in the urine of about 90% of the adults in the US can cause changes in the body. Actually the chemical having the effect is bisphenol A diglycidyl ether (BADGE). BPA can get into our bodies when BADGE breaks down.
The study found BADGE can induce stem cells to become fat cells, effect was noted at levels as low as 3 parts per billion. Although it has not been extensively studied one study found it in humans at a level of around 15 parts per billion, 5 times more than the level that triggered the proliferation of fat cells in the study.
The study makes no mention of T2 diabetes but with the correlation between obesity and insulin resistance in some people, perhaps this angle needs further study.