The findings bring fresh evidence against the chemical family, which is commonly found in both plastics packaging and a number of personal care products.
New research carried out by Danish medical experts again points to potential problems for newborn babies whose mothers have been exposed to high levels of phthalates during and after the pregnancy.
Professor Niels Skakkebæk and a team of pediatric endocrinologist at the Rigshospitalet in Copenhagen conducted the study on newborn baby boys, which has subsequently been reported in the journal Environmental Health Perspectives.
According to the team, phthalate chemicals found in a variety of commonly-used household products, including plastics packaging and cosmetics, can subtly reduce testosterone production in newborn boys.
Skakkebæk told ABC Science Online that the teams findings, "Gives a small piece of information that the newborn testis may be fragile to such toxins. Whether the effects will persist we can't tell but we were quite surprised at all to find such an association."
According to the team, exposure to phthalates caused baby boys to show slight signs of demasculisation, which falls in line with several scientifically-backed theories that phthalates can cause disruption to the endocrine, eventually disrupting the natural formation of reproduction organs.
The research centred on babies of three months old, a key period in the development of the reproductive systems. The study found that there was a direct correlation between the baby boys' testosterone levels compared to the levels of six different types of phthalates contained in the mothers' breast milk.
The team said that the higher levels of phthalates in the breast milk did lead to a small but discernable reduction in testosterone levels, in turn affecting the development of the reproductive systems.
However, Skakkebæk and his team have also stressed that nursing mother's should not stop breast feeding as a result of the findings. It was also emphasised that the reduction in the babies' testosterone levels could also be attributable to exposure to phthalates while still in the womb.
Although industry bodies such as the CTFA in the US have gone to great lengths to stress that no scientific study has categorically proven the correlation between phthalate exposure and the development of baby boys' reproductive systems, this report now adds to a catalogue of medical evidence suggesting that phthalates can be harmful.
Phthalates are industrial chemicals used in various consumer products, including shampoos, deodorants and hair sprays. In animal tests, some phthalates have damaged the developing testes of offspring and caused malformation of the penis and o the r parts of the reproductive tract.
Several top cosmetics companies, including L'Oréal, Revlon and Unilever, have said they will voluntarily remove DBP and DEHP from products sold in the United States, where the use of phthalates has until recently been completely unregulated.
However, last month a Bill was passed by the California state legislature banning the use of cosmetics ingredients said to induce harmful effects in pregnant women or to be carcinogens.
The bill focuses on the use of potentially dangerous phthalates, similarly stressing that the substances are banned by the European Union for use in cosmetics formulations.