This topic has been circulating since 2007. According to the story, a woman was told by her doctor that her breast cancer was a result of drinking water from plastic bottles left in her car. Supposedly the heat facilitated the leaching of the plastic chemicals into the water and these chemicals led to breast cancer. This story was labeled a myth.
New research by Wagner and Oehlman (2009) found that mineral water packaged in plastic bottles (PET) did contain xenoestrogens which in part, did originate from the plastic packaging. However, the bottles were not heated so the effect of higher temperatures on the packaging was not a part of the study. According to the findings of this research, plastic bottles contain more chemicals that mimic estrogen than glass bottles. This still does not mean the levels are high enough to cause breast cancer.
Source: Environmental Science and Pollution Research May, 2009.