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Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Professor Ian Rae is an expert on chemicals in the environment from the School of Chemistry at the University of Melbourne. He was also an advisor to the United Nations Environment Programme on chemicals in the environment and is former President of the Royal Australian Chemical Institute
The doses used in these experiments with mice are very high and so it is not surprising that developmental effects are evident. The relevance of the work to human exposures is hard to assess. Regulators, relying on a large number of experimental findings, have generally taken the view that humans are not affected by the low doses of phthalates to which we have all been exposed.
The toxicity of phthalates is recognized but only young children and other vulnerable groups are thought to be at-risk. Consequently phthalates have been banned from products that such individuals are likely to contact. The present results are unlikely to bring about any prompt review of the regulatory regime, but will be among those included in the database for future assessments.
Dr Ian Musgrave is a Senior Lecturer in the Faculty of Medicine, School of Medicine Sciences, within the Discipline of Pharmacology at the University of Adelaide.
Dibutyl phthalate (DBP) is a chemical used for a variety of industrial purposes, from adhesives to plastics. It has been shown to have effects on the reproductive system, and its use is limited.
This latest paper shows that exposure to DBP may have effects on bone density when pre-pubertal mice are exposed to DBP for 17 days then followed to adulthood.
Twelve measures of bone formation were assessed and three of these, including bone marrow volume and femur length, were significantly reduced in mice fed 100 and 500 mg DBP per kilogram of body weight per day. Bone mineral density was lower when mice were exposed to 10 mg DBP per kilogram of body weight per day, but not at higher exposures to DBP.
This is an interesting result, and will require further investigation to determine the mechanism behind these changes and why mineral density is not affected by higher doses. However, in terms of human exposure the maximum human exposure limit is 0.01 mg per Kg body weight per day, a level that is 1000 times lower than the doses that produced reduce mineral density. In the 24th Australian diet study, only two of 48 surveyed foods had detectable DBP, and it would require eating over 10 Kg of the food every day to reach the levels of DBP that reduced bone mineral density in mice.
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