The Phthalates chemical family is commonly used in a variety of personal care products, including shampoos, nail varnish, hair spray and perfumes. In Europe regulation has dictated that two of the most toxic phthalates - DEHP and DBP - have both been banned, but in the US there is no specific regulation in place.
The study, conducted by a team at the University of Rochester in New York, found that exposure to a range of the phthalates was linked to a higher risk of baby boys having undescended testes and smaller penises. This is the first study of its kind that indicates a proven link to defects in human beings.
In 2002 a report by environmental and health groups, entitled Not Too Pretty, said that independent lab tests on rats had found phthalates in 72 per cent of beauty products. Since phthalates are not listed as ingredients on product labels, they can only be detected through laboratory analysis.
Although international cosmetics manufacturers claim that phthalate levels are at a safe level in their products, lobby groups say the abundance of the chemical in a variety of cosmetics products - as well as household products such as inks, paint and clingfilm - can mean a build up of the chemical in the body which leads to dangerous levels.
The University of Rochester team examined 134 baby boys, between the ages of 2 and 36 months. The study found that women with higher levels of phthalates in their body were more likely to give birth to baby boys with irregular genitals.
Further more the scientists say that it did not take particularly high levels of phthalates to produce the abnormalities. Exposure to the chemical led to a 'demasculinization' of the male reproductive tract that was significantly related to phthalate exposure, the study said.
The boys' measurements were calculated according to an anogenital index (AGI), which accounted for the size of the boys genitals in proportion to their body weight. According to the study babies with a high exposure to phthalates were 90 times more likely to have a short AGI measurement - a result the scientists termed 'an extraordinarily large ratio.'
Of the nine phthalates metabolites considered in the study, four were said to show significant inverse correlations to the AGI index. DBP - found in perfume oils and nail varnish was a risk, as well as DEP - also found in nail varnish as well as perfumes, cosmetics oils, eye shadows and dental treatments - were both earmarked as particularly high risk.
Shanna Swan, the lead scientist for the University of Rochester study said: "We were able to show, even with our relatively small sample, that exposed boys were more likely to display a cluster of genital changes."
Swan further highlighted the gravity of the findings by pointing out that the abnormalities discovered in the group of baby boys appeared in women exposed to levels below those commonly found in a quarter of all US females tested for the chemical.
The results of the study could prove valuable ammunition to lobby groups and politicians in California who are currently trying to ban the use of certain phthalates for use in cosmetics. Bill 908 aims to stamp out the DEHP and DBP phthalate compounds, often used in fragrances, hair sprays and nail varnish - focusing on the fact that they caused health-related concerns, particularly among women of child bearing age.
Submitted by Californian state senator Carole Midgen, the senate is expected to vote on the bill this week. A yes vote could have serious implications and repurcussions for the regulation of a host of chemicals used in cosmetics products in the US as a whole.