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Environmental Factor, November 2012

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Household contaminants associated with childhood respiratory problems

By Nancy Lamontagne

Rachel Miller, M.D.

Shown above during a grantee meeting at NIEHS, Miller said her latest study found that prenatal exposure to PBO increased the odds of noninfectious childhood cough. Cough is a common reason for doctor visits in children younger than 5 years old. (Photo courtesy of Steve McCaw)

Matthew Perzanowski, Ph.D.

By using fractional exhaled nitric oxide as a biological marker of airway inflammation, Perzanowski’s research team could discern short-term associations between environmental measures and airway inflammation. Making these connections is important, because airway inflammation is associated with subsequent worsening of asthma. (Photo courtesy of Columbia University)

Two NIEHS-funded studies from the Columbia Center for Children’s Environmental Health (CCCEH) at the Columbia University Mailman School of Public Health report new findings that link exposures to chemicals found in the home with childhood respiratory problems.

Rachel Miller, M.D., led the study showing that children exposed to piperonyl butoxide (PBO) in the womb had an increased risk of noninfectious cough at ages 5 and 6. PBO is used to bolster the effects of pyrethroid pesticides, the most commonly used pesticides for professional pest control and in-home application. The findings provide evidence that children’s respiratory systems are susceptible to damage from contaminates during the prenatal period.

The researchers studied 224 mother-child pairs who lived in upper Manhattan and the south Bronx for at least one year. They examined levels of PBO and permethrin — a pyrethroid insecticide — by having mothers wear personal air monitors during pregnancy. They also collected air samples from the home when children were between 5 and 6 years old.

The researchers found that children with higher prenatal exposure to PBO were more likely to have a cough, unrelated to a cold or the flu, when they were between 5 and 6 years old. Exposures to PBO at ages 5 and 6 were not a factor, and the study results did not indicate that PBO or permethrin exposures were associated with other respiratory outcomes, such as wheeze or asthma. The researchers also did not find any association between prenatal or childhood permethrin exposure and cough, perhaps because PBO is much easier to measure in air samples than permethrin.

"While it is unclear whether the effect is due mainly to PBO itself or residential pyrethroids, of which PBO is an indicator, it is important to remember that cough is a very common complaint for which children and adults seek medical attention,” said Miller. “The results suggest that avoidance of exposure to PBO may be most important during pregnancy."

Phthalates and airway inflammation

In another study from CCCEH, researchers report that children exposed to diethyl phthalate (DEP) and butylbenzyl phthalate (BBzP) have a greater risk of asthma-related airway inflammation. Phthalates are used widely in consumer products, including plastics, vinyl flooring, and personal care products. Phthalate exposure can occur through ingestion, inhalation, and absorption through the skin.

The researchers led by Matthew Perzanowski, Ph.D., studied children ages 5 to 9 who were part of the same Manhattan-Bronx cohort used in Miller’s study. Urine tests revealed detectable, although varied, levels of phthalates in all 244 study participants. To quantify airway inflammation, the researchers measured the nitric oxide in the child’s exhaled breath. Nitric oxide is a biological marker of airway inflammation and was previously shown to increase in response to known asthma triggers, such as vehicle emission. The study is the first to use this biomarker to investigate airway responses to phthalate exposure in children.

The team found that higher levels of both DEP and BBzP were associated with higher levels of nitric oxide in exhaled breath. “We found that exposure to two phthalates, believed to have substantial inhalational exposure, was associated with greater airway inflammation and that this association was strongest among the children with recent asthma symptoms,” Perzanowski said. “Increases in airway inflammation, especially among these children with recent symptoms, could increase the likelihood of future asthma exacerbations.”

In addition to the NIEHS funding, Miller’s study received support from the Thrasher Research Fund and the U.S. Environmental Protection Agency (EPA). Perzanowski’s research also received funding from the U.S. EPA, the John and Wendy Neu Family Foundation, Blanchette Hooker Rockefeller Fund, New York Community Trust, Educational Foundation of America, and Millstream Fund.

Citations: Liu B, Jung KH, Horton MK, Camann DE, Liu X, Reardon AM, Perzanowski MS, Zhang H, Perera FP, Whyatt RM, Miller RL. 2012. Prenatal exposure to pesticide ingredient piperonyl butoxide and childhood cough in an urban cohort. Environ Int 48:156-161.

Just AC, Whyatt RM, Miller RL, Rundle AG, Chen Q, Calafat AM, Divjan A, Rosa MJ, Zhang H, Perera FP, Goldstein IF, Perzanowski MS. 2012. Children's urinary phthalate metabolites and fractional exhaled nitric oxide in an urban cohort. Am J Respir Crit Care Med; doi:10.1164/rccm.201203-0398OC [Online 23 August 2012].

(Nancy Lamontagne is a science writer with MDB, Inc., a contractor for the NIEHS Division of Extramural Research and Training, Superfund Research Program, and Worker Education and Training Program.)

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