Phthalates entering the bloodstream of fetuses could cause a greater risk of asthma in children exposed to the chemical, according to a new report from the National Institutes of Health. The two most common substances in this class are butylbenzyl phthalate (BBzP) and di-n-butyl phthalate (DnBP). They are commonly used to soften plastics.

Babies can be exposed to the class of chemicals from home exposure, as the substances are found in a variety of plastic items, including vinyl floors, plastic food containers, insect repellent and shower curtains. Commonly used in the manufacture of automobiles, this class of chemicals contributes to that "new car smell." They have already been banned for use in children's toys and in cosmetics since 2009, partly because of the effect they have on the onset of asthma. They are rarely listed in lists of materials which are used in products.

"The fetus is extremely vulnerable during pregnancy. While it is incumbent on mothers to do everything they can to protect their child, they are virtually helpless when it comes to phthalates like BBzP and DnBP... If we want to protect children, we have to protect pregnant women," Rachel Miller, professor of pediatric medicine and environmental health sciences, said.

Researchers studied more than 300 pregnant women to determine the effect of phthalates on developing fetuses. Concentrations of the chemicals in bodies of mothers and children were measured through urine samples. Investigators found exposure to the chemicals in the womb raised the risk of asthma by as much as 72 percent to 78 percent compared with children of mothers with lower levels of exposure. Most of these asthma cases onset in the children when they were between the ages of 5 and 11.

"Our goal is to try and uncover causes of this epidemic so we can better protect young children from this debilitating condition. Our study presents evidence that these two phthalates are among a range of known risk factors for asthma," Robin Whyatt, professor of Environmental Health Sciences at Columbia University, stated in a press release.

In addition to an increased risk of asthma, researchers found BBzP also contributed to the incidence of eczema, a skin rash. Researchers also looked at two other phthalates in their study, di-2-ethylhexyl phthalate (DEHP) and diethyl phthalate (DEP), which were not found to contribute to asthma or related conditions.

Researchers on the study are uncertain why some women and children have higher concentration of the chemicals than others.

Investigation of the connection between exposure to phthalates in the womb and increased risk of asthma was published in the journal Environmental Health Perspectives.

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