I would suggest if you are interested in learning more about the issue of chemical load, you
google and read the recent studies that are being done to evaluate the number of chemicals present in breast milk.
In a broad stroke, the problem is, for example, we are finding hundreds of chemicals in breast milk, many with suspected or known carcinogenic properties. The problem is for the vast majority, the "level" at which a chemical is considered "safe" or "acceptable" or "unsafe"...has not been determined for adults, let alone infants.
A class of chemicals, very much in the headlines recently are fire retardants, which are now one of the most common chemicals found in breast milk. The U.K. requires fire retandants on almost everything.
Another chemical in the hotseat and being actively investigated as we speak is "BPA" or Bisphosphonal A, a "plasticizer" that is suspected of causing hormonal disruptions. This is potentially especially worrisome for boys. If you eat canned food or use clear, hard polycarbonate plastic (#7 recycling symbol) for example many baby bottles, then you are being exposed to BPA.
Lastly I will say most would probably be surprised to know the numbers of unregulated chemicals they are being exposed to through their beauty and make-up products (shampoos, soaps, perfume, etc) In the U.S. these products are not under regulation and the E.U. is only slightly better. Two chemicals, of many, under scruitiny right now are pthalates and parabens
Two sites I highly recommend to learn more about these issues are...the Environmental Working Group and Not Too Pretty (which looks at chemicals in beauty products)
http://www.ewg.org/http://www.cosmeticsdatabase.com/splash.php?URI=%2Findex.php