Boys exposed in the womb to chemicals called phthalates are less likely to engage in masculine play during childhood. So says a study soon to be published in the International Journal of Andrology. Masculine play was defined as playing with guns, cars, trucks and other toys typically favored by boys. The greater the exposure during pregnancy, the more dramatic was the behavioral effect later. Girls’ play was not affected.
Hormones program the fetal brain
According to Heather Patisaul, a neuroendocrinologist at NC State, male sex hormones program fetal brain development, and this programming explains why boys like trucks and girls tend to prefer dolls. Anything that interferes with this hormonal influence can subtly reduce masculinization of a male’s brain.
Phthalates have previously been reported to affect male hormones, but it was not known how this affected behavior. The current study began several years ago when researchers measured phthalates during mid-pregnancy in a group of women across four states. Three to six years later, the researchers asked the mothers to rate their children’s play using the Pre-school Activities Inventory. Each mother recorded how often in the past month her child had engaged in activities such as playing house, playing with dolls, dressing up in girls’ clothes, playing with toy cars and trucks or guns, or play-fighting. The study included 71 girls and 74 boys.
Less masculine play; more gender-neutral play
The behavioral assessment revealed that boys with the highest exposure to phthalates in the womb had the lowest incidence of typically male play and a higher incidence of gender-neutral play. The phthalate-exposed boys did not have higher scores for typically female play. The lead researcher, Shanna Swan of the University of Rochester School of Medicine & Dentistry, said “We’d describe their play as less masculine,” but not more feminine.
These findings are thought to be particularly significant because exposure to phthalates is so widespread and includes virtually everyone in the U.S. Phthalates are industrial chemicals widely used as solvents, including use in cosmetics such as nail polish and hair spray. They are also widely used in plastic tubing involved in food processing.
The summary I read of the study, in Science News, did not offer any suggestions about how to avoid ingesting phthalates. If I do find any information about that, I’ll post it on http://veggierevolution.blogspot.com and on http://sallykneidel.com. I’ll keep an eye out for the report of the study that will soon be published in the academic journal mentioned above.
by Sally Kneidel, PhD
Janet Raloff. “Chemicals from plastics show effects in boys: Fetal exposure to phthalates linked to less masculine play.” Science News. December 19, 2009.