Boys exposed in the womb to high levels of a chemical found in vinyl products are born with slightly altered genital development, according to research published today. The study of nearly 200 Swedish babies is the first to link the chemical di-isononyl phthalate (DiNP) to changes in the development of the human male reproductive tract.
Phthalates are used as plasticizers in soft polyvinyl chloride (PVC) and in a large number of consumer products. Due to reported health risks, di-isononyl phthalate (DiNP) has been introduced as a replacement for diethyl hexyl phthalate (DEHP) in soft PVC. This raises concerns since animal data suggest that DiNP may have anti-androgenic properties similar to DEHP. The anogenital distance (AGD) – the distance from the anus to the genitals – has been used to assess reproductive toxicity.
The objective of this study was to examine the associations between prenatal phthalate exposure and AGD in Swedish infants.
AGD was measured in 196 boys at age 21 months and first trimester urine was analyzed for ten phthalate metabolites of DEP, DBP, DEHP, BBzP as well as DiNP and creatinine. Data on covariates were collected by questionnaires.
The most significant associations were found between the shorter of two AGD measures (anoscrotal distance, AGDas) and DiNP metabolites and strongest for oh-MMeOP and oxo-MMeOP. However, the AGDas reduction was small (4%) in relation to more than an interquartile increase in DiNP exposure.
These findings call into question the safety of substituting DiNP for DEHP in soft PVC, particularly since a shorter male AGD has been shown to relate to male genital birth defects in children and impaired reproductive function in adult males and the fact that human levels of DiNP are increasing globally.