Male fetuses exposed to high levels of a chemical from the phthalate family commonly used in consumer products may be born with slightly altered genital development, according to a study published online last week.
The study of 200 Swedish babies is the first to link the chemical diisononyl phthalate (DINP) to abnormalities in the development of the human male reproductive system.
Previous studies of male infants in three countries found that a closely related chemical, DEHP, was associated with the same type of malformations in their genitalia.
The reproductive risks of DINP, which has been increasingly used as alternative to DEHP in products such as flooring, vinyl toys, and packaging are not as well documented as those in DEHP. According to the study, in mice high levels of DEHP exposure blocks testosterone and alters testicular development.
Lead researcher Carl-Gustaf Bornehag at Sweden’s Karlstad University, said the data suggests that DINP may not be safer than the chemical it is replacing, in the study published in Environmental Health Perspectives.
The researchers noted DINP levels detected in U.S. adults and children have more than doubled since 2004.
The metabolites of five phthalates in the urine of pregnant women in the first trimester was tested by the Swedish researchers. According to author Shanna Swan, a professor of reproductive science at Mount Sinai Hospital in New York, the development of male reproductive organs begins during this period.
The researchers later measured the distance between the anus and the genitals in 21 month old males, finding those who had been exposed to the highest levels of DINP in the womb averaged a distance that was slightly shorter than the boys with the lowest exposures.
Shortened anogenital distance in men is associated with abnormal testicular development and reduced semen quality and fertility. However, it’s unknown whether a slightly shorter distance in infants results in fertility problems later in life.
“The $64,000 question” is whether baby boys with a shorter anogenital distance maintain that characteristic throughout life, Swann said.
The study found some evidence of shorter anogenital distance in males exposed to higher concentrations of other phthalates, but the results were not statistically significant.
The Swedish women in Swann’s new study had comparable phthalate levels to American women in studies previously published by in 2005 and 2008.
An industry spokesman from the American Chemistry Council (ACC), a trade association representing chemical manufacturers, said the new study “reports small changes that are associated with exposure to DINP” but does not prove that the chemical caused the changes. The ACC spokesman also criticized the study because it was based on a single urine sample, adding that the study scores low for important factors necessary to show causal associations in an epidemiological study.
In 2008, the U.S. Consumer Product Safety Commission (CPSC) temporarily banned use of DiNP and two other phthalates in toys and other children’s products. The agency recommended in July to make the ban permanent and urged that “U.S. agencies responsible for dealing with DINP exposures from food and other products conduct the necessary risk assessments.”
DINP was listed last December as a carcinogen by CalEPA’s Carcinogen Identification Committee. Products containing the chemical will be subject to Proposition 65 enforcement beginning December 20.
In June, ACC filed a writ of mandate to reverse the California Office of Environmental Health Hazard Assessment’s listing of DINP.