Although hypospadias may not be increasing now, several reports previously noted a doubling of rates in the 1970s and 1980s.
Traces of many phthalates have been found in the urine of nearly every human tested. One study, conducted in Germany, found that some of the compounds have increased in people over the past 20 years, while others have decreased, and that exposure varies greatly from place to place. Some people exceed the daily levels that the U.S. Environmental Protection Agency or European Food Safety Authority consider safe.
But whether the chemicals are harming people, particularly boys, has become quite controversial in the past couple years.
Chemical industry representatives have pointed to the hypospadias study as evidence that phthalates, which have been used as a plasticizer in vinyl for about 50 years, are not causing male reproductive abnormalities. In addition, while some studies have found that men’s sperm counts have declined substantially, others have reported no decline, which also casts doubt on the human effects of endocrine disruptors.
But Hauser said the hypospadias study does not invalidate the testicular dysgenesis theory because no data was collected on the boys’ exposure to phthalates or other chemicals.
Researchers would need to collect exposure information on a large number of pregnant women, and then see if the rate of hypospadias among the highly exposed boys is different than those with low exposure, Hauser and Harley said.
The findings are useful for exploring trends in hypospadias over time, not exploring potential causes, they said.
“Over-interpretation should be avoided, especially using them to try to prove a negative,” Hauser said.
In addition to animal studies, other research has linked phthalates to reproductive effects.
Hauser and his colleagues reported in 2006 that men with higher levels of one common phthalate had lower sperm concentrations and quality. And a study of 176 male infants by University of Rochester scientists found that babies exposed to higher amounts of phthalates had a shorter anogenital index (the length of the perineum), which is a sign of feminized hormones.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.