Study links hairspray to male birth defect

New research suggests mothers’ exposure to hairspray and phthalates increases the risk of a common birth defect in sons. The results highlight the lack of a human biomonitoring programme in the UK that could help quantify the risks posed by the chemicals.

Mothers’ exposure to endocrine-disrupting chemicals may increase the risk of the congenital abnormality hypospadias in sons, a UK study has revealed.1

Occupational exposure to hairspray and phthalates during pregnancy more than doubled the risk of the disease in male babies, but folate supplements seemed to reduce the risk.

Hypospadias, a deformity in which the urethral opening is located on the underside of the penis, affects up to 24 out of every 10,000 male babies. The causes are little understood, but animal studies suggest endocrine-disrupting chemicals, which interfere with male sexual development, may play a role. Two earlier studies also linked the condition to vegetarian mothers.

To probe potential risk factors Professor Paul Elliot of the Small Area Health Statistics Unit and colleagues in Ireland and Spain investigated 471 cases of hypospadias diagnosed during 1997 and 1998 in south-east England. Mothers of affected boys and 490 control subjects were interviewed between 2000 and 2003. Exposure to a range of chemicals was estimated depending on the mothers’ occupation.

Workplace exposure to hairspray or phthalates was associated with increased risk of hypospadias. Hairspray exposure increased the probability of hypospadias by a factor of 2.39. For phthalates, the probability increased further by 3.12 times but this association was based on just 14 cases and four controls.

Taking folate supplements during the first three months of pregnancy appeared to lower the probability of hypospadias occurring by 0.64. The authors found no significant link between the disorder and vegetarianism.

Professor Elliot said the work was preliminary and the study "had not demonstrated cause". It did not look at mothers’ actual chemical exposure, for instance by measuring phthalate metabolites in blood. Neither was the chemical composition of hairsprays investigated, although phthalates are likely to have been present during the study. Professor Elliot noted that phthalates were removed from these products in 2005.

There is little data on typical phthalate exposure in the UK. In the US the National Health and Nutrition Examination Survey carries out systematic human biomonitoring every two years for an expanding list of chemicals, including seven phthalates (ENDS Report 374, p 29 ). No comparable project exists at a UK or EU level, although there is interest in this type of research.

Professor Elliot said there is a gap on human biomonitoring of environmental exposure. The Medical Research Council currently funds little in this area.

An attempt was made to set up an EU human biomonitoring project in 2006 (ENDS Report 374, p 26 ). The project organised a Consortium to Perform Human Biomonitoring on a European Scale (COPHES) and applied for funding from the European Commission. However, the application was rejected.

COPHES was to have two phases: biomonitoring for heavy metals and a biomarker for nicotine; then a wider range of chemicals including polycyclic aromatic hydrocarbons, brominated flame retardants, phthalates and organotins.

Even if COPHES is supported under a future funding round, it’s biomonitoring work is unlikely to start before 2010.

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