Bisphenol A (BPA) is a plastic compound that has been found to lower levels of testosterone and cause testicular shrinkage in rats.
A potentially more potent form of BPA called BPAF has also been shown to lower testosterone levels.
BPA is found in many plastic food and drink containers, see this previous post for more information on the potential sources of BPA, and its links to infertility and cancer: http://vitatalks.com/2011/01/12/toxic-plastic-compound-bisphenol-a-damages-fertility-and-increases-cancer-risk/
Look for plastic containers that say they are BPA free
El-Beshbishy HA, Aly HA, El-Shafey M (2012). Lipoic acid mitigates bisphenol A-induced testicular mitochondrial toxicity in rats. Toxicol Ind Health. 2012 May 23.
Feng Y, Yin J, Jiao Z, Shi J, Li M, Shao B (2012). Bisphenol AF may cause testosterone reduction by directly affecting testis. Toxicol Lett. 2012 Jun 1;211(2):201-9.