Maternal Exposure to Ambient Levels of Benzene

Research studies on wood smoke and other air pollution.

Maternal Exposure to Ambient Levels of Benzene

Postby Wilberforce » Tue Oct 26, 2010 7:44 pm

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Maternal Exposure to Ambient Levels of Benzene and Neural Tube Defects among Offspring, Texas, 1999-2004
Philip J. Lupo, Elaine Symanski, D. Kim Waller, Wenyaw Chan, Peter H. Langlois, Mark A. Canfield, Laura E. Mitchell
http://www.ncbi.nlm.nih.gov/pmc/?term=1 ... hp.1002212
Background: Previous studies have reported positive associations between maternal exposure to air pollutants and several adverse birth outcomes. However, there have been no studies assessing the association between environmental levels of hazardous air pollutants (HAPs), such as benzene, and neural tube defects (NTDs), a common and serious group of congenital malformations.

Objective: Our goal was to conduct a case-control study assessing the association between ambient air levels of benzene, toluene, ethylbenzene, and xylene (BTEX) and the prevalence of NTDs among offspring.

Methods: The Texas Birth Defects Registry provided data on NTD cases (spina bifida and anencephaly) delivered between 1999 and 2004. The control group was a random sample of unaffected live births, frequency matched to cases on year of birth. Census tract-level estimates of annual BTEX levels were obtained from the U.S. EPA’s 1999 Assessment System for Population Exposure Nationwide (ASPEN). Restricted cubic splines were used in mixed-effects logistic regression models to determine associations between each pollutant and NTD phenotype. Results: Mothers living in census tracts with the highest benzene levels were more likely to have offspring with spina bifida compared to women living in census tracts with the lowest levels (OR = 2.30; 95% CI: 1.22, 4.33). No significant associations were observed between anencephaly and benzene, or between any of the NTD phenotypes and toluene, ethylbenzene, or xylene.

Conclusion: In the first study to assess the relationship between environmental levels of BTEX and NTDs, we found an association between benzene and spina bifida. Our results contribute to the growing body of evidence regarding air pollutant exposure and adverse birth outcomes.
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Postby Wilberforce » Tue Mar 01, 2011 7:08 pm

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Not Just for Workers: Maternal Exposure to Ambient Benzene Linked to Spina Bifida in Infants
Julia R. Barrett, MS, ELS, a Madison
http://www.ncbi.nlm.nih.gov/pmc/?term=1 ... .119-a133a
Occupational exposure to hazardous air pollutants such as benzene has been linked in some studies to neural tube defects (NTDs), yet to date no one had studied whether exposure to ambient levels of benzene may similarly lead to adverse outcomes. A new study now reveals a positive association between exposure to ambient benzene in outdoor air and increased prevalence of spina bifida [EHP 119(3):397–402; Lupo et al.].

NTDs are a common type of birth defect. They arise when the neural tube fails to close during fetal development, leading to spina bifida (incomplete spinal column formation) or anencephaly (incomplete brain and skull formation). Both genetic and environmental factors, particularly inadequate folic acid intake, appear to play a role in NTDs.

The Texas Birth Defects Registry provided data from 1 January 1999 to 31 December 2004 on 1,108 newborn infants, stillborn infants, and electively terminated fetuses with NTDs. A random set of 4,132 unaffected infants born during the same period served as a control group. Ambient air levels of benzene, toluene, ethylbenzene, and xylene were estimated at the census-tract level using the U.S. Environmental Protection Agency’s 1999 Assessment System for Population Exposure Nationwide (ASPEN) paired with mothers’ residential addresses at the time they gave birth. After exclusions for missing data and known chromosomal abnormalities or syndromes, 533 spina bifida cases, 303 anencephaly cases, and 3,695 control cases remained for analysis.

Mothers with the highest estimated benzene exposure (=3 µg/m3 in ambient air) were 2.3 times as likely as mothers in the reference group to bear children with spina bifida. The relationship between benzene exposure and spina bifida was statistically significant for most levels of exposure above the reference value, but the dose–response relationship was not monotonic (that is, the odds of risk did not increase consistently with each increase in exposure level). Associations between other solvents and spina bifida and between individual solvents and anencephaly also were observed but were not statistically significant.

The study has several potential limitations including possible exposure misclassification, the availability of pollutant data for only 1 year of the study period, and limited information on potential confounders, such as maternal folic acid intake. However, these limitations are at least partially offset by ASPEN’s high-quality exposure estimates, the likelihood that pollutant levels were stable during the study years, and mandatory folic acid fortification of foods.

This study is the first to suggest spina bifida prevalence is associated with maternal exposure to ambient air benzene levels. Further study of exposure, genotypes, and maternal nutrient status are needed to confirm this finding.
• The Surgeon General has determined that there is no safe level of exposure to ambient smoke!

• If you smell even a subtle odor of smoke, you are being exposed to poisonous and carcinogenic chemical compounds!

• Even a brief exposure to smoke raises blood pressure, (no matter what your state of health) and can cause blood clotting, stroke, or heart attack in vulnerable people. Even children experience elevated blood pressure when exposed to smoke!

• Since smoke drastically weakens the lungs' immune system, avoiding smoke is one of the best ways to prevent colds, flu, bronchitis, or risk of an even more serious respiratory illness, such as pneumonia or tuberculosis! Does your child have the flu? Chances are they have been exposed to ambient smoke!
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