In the United States, the onset of puberty has been occurring earlier and earlier. Today, about 10 percent of children ages 6 or 7 begin developing signs of puberty, a condition known as precocious puberty. In the early 1900s, girls typically began menstruating at age 17. Today, girls typically begin around age 12. This trend has been attributed to the growing number of overweight children and a greater exposure to pollutants. Exposure to phthalates, artificial chemicals found in plastics, has also been cited as a cause. These chemicals disrupt the endocrine system by mimicking hormones in the body.

Early puberty can have many negative side effects, including an increased risk of certain types of cancer, such as breast cancer. Children are often emotionally unprepared for the physical changes taking place in their bodies. As a result, behavioral and psychological problems may increase.

According to the text, what are the likely causes of precocious puberty? Check all that apply.

exposure to pollutants
exposure to phthalates
certain types of cancers
unhealthy weight gain
disruptions to the endocrine system
emotional and psychological problems