Here is a very nice document put together by Purdue describing how substances such as insecticides are developed and regulated as well as principles of toxicology. It might make all involved feel a little better about the amount of research that goes into the products before they hit the market. WARNING:There is a frank description of animal studies;if you feel like you might be offended, do not open the link.
http://www.btny.purdue.edu/Pubs/PPP/PPP-40.pdf
http://www.btny.purdue.edu/Pubs/PPP/PPP-40.pdf