About 15 percent of American girls now begin puberty by age 7, according to a study of 1,239 girls published last year in the journal Pediatrics. One in 10 white girls begin developing breasts by that age - twice the rate seen in a 1997 study. Among black girls, 23 percent hit puberty by age 7.
On "The Early Show" CBS News Medical Correspondent Dr. Jennifer Ashton, an OB-GYN who specializes in adolescent care, said "early puberty," also known as "precocious puberty," has risks for girls.
"Body fat generates the hormone estrogen, partially," Ashton said. "Estrogen is part of the hormones that triggers puberty. A lot more children are overweight and obese. Environmental exposures, things like BPA (Bisphenol A) that are ubiquitous in our environment can have hormone-like activity and research is ongoing as to whether that plays a role. And your family history - if your mother went through early puberty, you have a greater chance of going through early puberty, as well."
Early puberty could affect girls as they get older, Ashton said. They have an increased risk of breast cancer and uterine cancer, she said, because these girls have more time to be exposed to the estrogen hormone
Another study links Pesticides to increased risk of ADHD
The study on pesticides and health reports, however, that there is no evidence that organophosphate pesticide exposure can actually cause ADHD .
Pesticide Effect on Health
Pesticides effects on humans are damage to the nervous system, reproductive system and other organs, disruption of hormone function, immune dysfunction and developmental and behavioral abnormalities.
Organophosphates Widely Used
"Organophosphates are one of the most widely used pesticides in agriculture to protect crops and fruits and vegetables," according to lead author Maryse Bouchard, Ph.D., adjunct researcher, department of environmental and occupational health, University of Montreal and Sainte-Justine University Hospital Centre, Canada. "For children, the major source of exposure would be the diet -- fruits and vegetables in particular."
Organophosphate pesticides account for approximately half the insecticide use in the U.S. and are applied to many conventionally grown foods important in children’s diets.
In 2008, the USDA conducted tests that found malathion (one of the 40 organophosphate pesticides) residues in 28% of frozen blueberries, 25% of strawberries, and 19% of celery.
Previous Pesticide Exposure Research Links Pesticide Exposure During Pregnacy to Developmental Problems in Offspring
Previous research has shown an association between both prenatal and postnatal organophosphate exposure and developmental problems in young children. But most prior studies have focused on excessive rather than average exposure to organophosphates.
Pesticide – ADHD Study
The researchers analyzed data on pesticide exposure and ADHD in more than 1,100 American children aged 8 to 15.
Children with higher pesticide levels in their urine were more likely to have ADHD , according to the researchers.
"The analysis showed that the higher the level of exposure [as measured by metabolites in the urine], the higher the odds of having ADHD," said Bouchard.
Just how might pesticides harm brain development? According to the authors, high doses of organophosphates pesticides may inhibit acetylcholinesterase, a nervous system enzyme. Lower doses of organophosphates pesticides may affect different growth factors and neurotransmitters.
The findings, if replicated, may provide another clue into the causes of ADHD, a condition which affects three to seven percent of school-aged children, according to the U.S. Centers for Disease Control and Prevention.
Bouchard MF, Bellinger DC, Wright RO, et al. Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides. Pediatrics 2010;125:e1270–e1277
Maryse Bouchard, Ph.D., adjunct researcher, department of environmental and occupational health, University of Montreal and Sainte-Justine University Hospital Centre, Canada;