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Environmental Factor

January 2011

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Extramural papers of the month

By Jerry Phelps
January 2011

SRP logo Research Brief

BPA exposure and oocyte quality

A small study conducted by NIEHS-supported researchers at the University of California, San Francisco has determined that as blood bisphenol A (BPA) levels rise, the quality of oocytes from women undergoing in vitro fertilization declines. As blood levels of BPA doubled, the percentage of eggs that fertilized normally declined by 50 percent.

BPA levels and fertilization rates were analyzed for 26 women undergoing in vitro fertilization during 2007 and 2008. The women were a subgroup of a larger study evaluating the effects of trace exposures to toxic metals on reproductive health.

Though the size of the study is small, the results indicate a negative effect of BPA on reproduction and fertility that may carry over to the general population. Further research on a much larger cohort of participants is necessary to confirm these findings in the general population, but given the widespread nature of BPA exposure in the U.S., even a modest effect on reproduction demonstrates a substantial concern according the researchers.

Citation: Fujimoto VY, Kim D, Vom Saal FS, Lamb JD, Taylor JA, Bloom MS.( Exit NIEHS 2010. Serum unconjugated bisphenol A concentrations in women may adversely influence oocyte quality during in vitro fertilization. Fertil Steril; doi:10.1016/j.fertnstert.2010.11.008( Exit NIEHS [online 4 December 2010]

Freeway proximity and autism

New research findings from a study sponsored by NIEHS suggest that babies born to mothers who live close to freeways have double the risk of developing autism compared to other children. The study examined almost 600 children ages 2-5 from Los Angeles, San Francisco, and Sacramento, Calif. About half the children had autism. Those whose homes were less than 1,000 feet from a freeway were about twice as likely to have autism.

Little is known about environmental contributions to autism, but oxidative stress and inflammation have been linked to the disorder. Previous basic research has demonstrated that traffic-related air pollution causes oxidative damage and increases inflammatory signaling pathways.

In the current study, 304 children who had autism were compared to 259 typically developing children. The study participants were enrolled in the Childhood Autism Risks from Genetics and the Environment (CHARGE) study. After adjusting for socioeconomic and demographic factors, the mother's address, taken from the birth record, was more likely to be near a freeway (less than 309 meters) for cases as compared to controls. Autism was also associated with residential proximity to a freeway during the third trimester; however, living near other major roads was not associated with autism.

Citation: Volk HE, Hertz-Picciotto I, Delwiche L, Lurmann F, McConnell R.( Exit NIEHS 2010. Residential Proximity to Freeways and Autism in the CHARGE study. Environ Health Perspect; doi:10.1289/ehp.1002835 [Online 13 December 2010]

A simple sensor for explosive chemicals

University of Illinois chemists have developed a simple device to detect an explosive like those used in several recent unsuccessful attempts to bring down airliners. The device could lead to an inexpensive and easy-to-use detector for luggage and passenger screening in airports.

The explosive, triacetone triperoxide (TATP), is easily prepared from products readily available, but it is very difficult to detect with standard detection methods. The researchers developed a colorimetric sensor assay that can detect very low levels of TATP vapor, as low as 2 parts per billion, in a matter of seconds. The sensor array consists of 16 colored dots on an inert plastic film. An acid catalyst breaks down TATP into detectable components that cause the pigments to change color.

The array is uniquely sensitive to TATP and is unaffected by temperature, humidity, or exposure to other chemicals, such as those found in detergents or personal care products. The chemists made a hand-held prototype that is just as effective as their laboratory model. The hand-held sensor is now being commercialized by iSense, a sensor manufacturer based in Palo Alto, Calif.

Citation: Lin H, Suslick KS.( Exit NIEHS 2010. A colorimetric sensor array for detection of triacetone triperoxide vapor. J Am Chem Soc 132(44):15519-15521.

Blood DNA methylation related to heart disease and stroke

NIEHS-supported epidemiologists at Harvard University found that blood DNA methylation is linked to the risk of ischemic heart disease and stroke in a population of 712 elderly subjects in the Boston-area Normative Aging Study.

The team measured blood cell DNA methylation of Long Interspersed Nucleotide Element-1 (LINE-1) repetitive elements by polymerase chain reaction pyrosequencing. They estimated relative risks for ischemic heart disease and stroke at baseline and again five years later, and also for mortality from ischemic heart disease.

LINE-1 hypomethylation was associated with baseline heart disease and stroke (relative risk = 2.1 and 2.5 respectively). In participants free of disease, hypomethylation was associated with higher risk for developing ischemic heart disease (relative risk = 4.1) or stroke (relative risk = 5.7). In the entire cohort, subjects with hypomethylation were about three times more likely to die of ischemic heart disease or stroke.

The researchers conclude that as standardized assays become more readily available, DNA methylation analysis may contribute to better cardiovascular risk estimation. These results add to the importance of ongoing endeavors in developing interventions and treatments that act through epigenetic mechanisms.

Citation: Baccarelli A, Wright R, Bollati V, Litonjua A, Zanobetti A, Tarantini L, Sparrow D, Vokonas P, Schwartz J( Exit NIEHS. 2010. Ischemic heart disease and stroke in relation to blood DNA methylation. Epidemiology 21(6):819-828.

(Jerry Phelps is a program analyst in the NIEHS Division of Extramural Research and Training.)

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