Refusal to refund money or replace defective product

I purchased several Nalgene bottles on two separate occasions because: 1)they were advertised as a solution to my concerns about the environmental impact of using disposable water bottles; and 2) they are touted as the safest bottles to use, made from polycarbonate, safe from leaching chemicals. Sure enough, these "safe" Nalgene bottles were found to leach a cetain chemical called Bisphenol-A (BPA)and therefore they are now producing a whole new line of bottles which are BPA free. I asked the company to give me a refund or to replace the bottles but they only offered me a discount on future purchases. Now I have all of these "safe" bottles which I can no longer let my family use. I think this is a total lack of corporate responsibility to the retail consumer which the company clearly targets as the customer for Nalgene water bottles.