However careful you are about your health, your body is almost certainly home to troubling chemicals called phthalates. These are ubiquitous in modern life, found in plastic bottles, cosmetics, some toys, hair conditioners, and fragrances - and many scientists have linked them to everything from sexual deformities in babies to obesity and diabetes. The problem is that phthalates suppress male hormones and sometimes mimic female hormones. Chemicals called endocrine disruptors are believed to explain the proliferation of intersex fish" - male fish that produce eggs - as well as sexual deformities in animals and humans. Phthalates ... are among the most common endocrine disruptors, and among the most difficult to avoid. They're even in tap water, and levels soar in certain plastic water bottles. In girls, some research suggests that phthalates may cause early onset puberty. Most vulnerable of all, it seems, are male fetuses in the first trimester of pregnancy, just as they are differentiating their sex. At that stage, scholars believe, phthalates may "feminize" these boys. "Commonly used phthalates may undervirilize humans," concluded a study by the University of Rochester. There has also been a flurry of scientific articles questioning whether endocrine disruptors are tied to obesity, autism and allergies, although the evidence there is less firm than with genital abnormalities and depressed sperm count. Dr. Theo Colborn, the founder of the Endocrine Disruption Exchange, ... tells researchers working with her to toss out plastic water bottles and use stainless steel instead. "I don't have plastic food containers in my house," she added. "I use glass."