Relationship between vapor intrusion and human exposure to trichloroethylene.

Trichloroethylene (TCE) in groundwater has the potential to volatilize through soil into indoor air where it can be inhaled. The purpose of this study was to determine whether individuals living above TCE-contaminated groundwater are exposed to TCE through vapor intrusion. We examined associations between TCE concentrations in various environmental media and TCE concentrations in residents. For this assessment, indoor air, outdoor air, soil gas, and tap water samples were collected in and around 36 randomly selected homes; blood samples were collected from 63 residents of these homes. Additionally, a completed exposure survey was collected from each participant. Environmental and blood samples were analyzed for TCE. Mixed model multiple linear regression analyses were performed to determine associations between TCE in residents' blood and TCE in indoor air, outdoor air, and soil gas. Blood TCE concentrations were above the limit of quantitation (LOQ; ≥ 0.012 µg L(-1)) in 17.5% of the blood samples. Of the 36 homes, 54.3%, 47.2%, and >84% had detectable concentrations of TCE in indoor air, outdoor air, and soil gas, respectively. Both indoor air and soil gas concentrations were statistically significantly positively associated with participants' blood concentrations (P = 0.0002 and P = 0.04, respectively). Geometric mean blood concentrations of residents from homes with indoor air concentrations of >1.6 µg m(-3) were approximately 50 times higher than geometric mean blood TCE concentrations in participants from homes with no detectable TCE in indoor air (P < .0001; 95% CI 10.4-236.4). This study confirms the occurrence of vapor intrusion and demonstrates the magnitude of exposure from vapor intrusion of TCE in a residential setting.

Relationship between prenatal lead exposure and infant blood lead levels.

Recent literature has shown that analyzing newborn dried blood spots (DBS) may be effective in assessing some prenatal environmental exposures, such as exposure to lead. The purpose of this study was to evaluate the relationship between prenatal exposure to lead (as measured by newborn DBS results) and blood lead levels (BLLs) in infants 6 months of age or younger, using public health registry data for infants born in Texas from July 2002 through July 2006. The Texas Child Lead Registry (TCLR) was used to identify infants with documented elevated BLLs of 10 µg/dL or higher as well as infants with documented low BLLs. BLLs for these children were compared to their corresponding newborn DBS results using Pearson correlation coefficients and exact logistic regression models. Overall, a significant but weak positive correlation was found between infant BLLs and corresponding newborn DBS lead levels (r = 0.48). However, the odds of an infant with an elevated newborn DBS lead level having an elevated BLL at 6 months of age or younger were much greater than for an infant with a low newborn DBS lead level of <5 µg/dL (adjusted odds ratio 27.95, 95% CI: 5.52-277.28). Although an association was observed between newborn DBS lead levels and BLLs in infants tested between 0 to 6 months of age, our findings suggest that prenatal exposure may not be the only significant source of lead exposure for infants ≤6 months of age.

Survey of mosquito fauna in Lubbock County, Texas.

Records of mosquito species occurring in Lubbock County, TX, have not been reported since 1970. An updated mosquito survey was conducted as part of the West Nile virus surveillance program conducted throughout Lubbock County, TX from July 2002 through December 2004. A large number of species not previously recorded occurring in this area were collected, whereas several species historically occurring in the area were not collected during this survey. Based upon the data from this study, dominant species in Lubbock County include Aedes sollicitans, Aedes vexans, and Culex tarsalis.

Uptake, elimination, and relative distribution of perchlorate in various tissues of channel catfish.

This study was undertaken to determine the kinetics of uptake and elimination of perchlorate in channel catfish, Ictalurus punctatus. Perchlorate--an oxidizer used in solid fuel rockets, fireworks, and illuminating munitions--has been shown to effect thyroid function, causing hormone disruption and potential perturbations of metabolic activities. For the uptake study, catfish were exposed to 100 mg/L sodium perchlorate for 12 h to 5 d in the laboratory. Perchlorate in tissues was analyzed using ion chromatography. The highest perchlorate concentrations were found in the head and fillet, indicating that these tissues are the most important tissues to analyze when determining perchlorate uptake into large fish. To calculate uptake and elimination rate constants for fillet, gills, G-I tract, liver, and head, fish were exposed to 100 ppm sodium perchlorate for 5 days, and allowed to depurate in clean water for up to 20 days. The animals rapidly eliminated the perchlorate accumulated showing the highest elimination in fillet (Ke = 1.67 day(-1)) and lowest elimination in liver (Ke = 0.79 day(-1)).

Uptake and elimination of perchlorate in eastern mosquitofish.

The purpose of this study was to investigate the uptake and elimination of perchlorate in eastern mosquitofish (Gambusia holbrooki). Fish were exposed to 0.1-1000 mg/l sodium perchlorate for 12h, 1, 2, 5, 10, and 30 days, and perchlorate was determined in whole body extracts. Perchlorate was not detected in mosquitofish exposed to the low concentrations of perchlorate (0, 0.1, and 1mg/l sodium perchlorate), regardless of the exposure time, whereas it was detected when fish were exposed to 10, 100, and 1000 mg/l. The tissue concentrations were approximately 10 times less than that in the water. There was no difference in the uptake of perchlorate depending upon the exposure time, however, a difference in perchlorate uptake depending upon the concentration of the exposure dose (P<0.001) was observed. Uptake (K(u)) and elimination (K(e)) rate constants were 0.09 l/mg day and 0.70 day(-1), respectively. The half-life (T1/2) of perchlorate was 0.99 day. Thus, it appears that perchlorate is rapidly taken up and eliminated in eastern mosquitofish. These results are critical and may be used to develop models of fate, effects, and transport of perchlorate in natural systems, as well as to assess ecological risk in affected ecosystems.

Perchlorate affects thyroid function in eastern mosquitofish (Gambusia holbrooki) at environmentally relevant concentrations.

The purpose of this study was to determine the effects of perchlorate on thyroid function in mosquitofish. Adult mosquitofish were exposed to 0, 0.1, 1, 10, 100, and 1000 mg/L sodium perchlorate for 2, 10, and 30 d. Whole body thyroxin (T4) content and histological assessment of thyroid follicles (e.g., follicular epithelial height, hyperplasia, hypertrophy, and colloid depletion) were used to gauge alterations in thyroid function. Follicular epithelial cell height, hyperplasia, and hypertrophy increased with increasing perchlorate concentration, especially in fish exposed for 30 d, and these effects were statistically significantly different from control at concentrations as low as 0.1 mg/L (nominal concentration). The percent occurrence of follicles with depleted colloid decreased with increasing perchlorate concentration, which is contrary to what is expected with thyroid inhibition. There also was a decrease in whole body T4 concentration in fish exposed to perchlorate for 30 d, but clear dose-response relationships were less evident for whole body T4 than for histopathological endpoints. In conclusion, thyroid histopathology provides a sensitive biomarker for thyroid endocrine disruption at environmentally relevant concentrations of sodium perchlorate, and whole body T4 is a less sensitive indicator of perchlorate exposure than is histopathology.

First report of West Nile virus in mosquitoes from Lubbock County, Texas.

Since July 2002, ongoing surveillance efforts have been conducted to determine potential vectors of West Nile virus (WNV) and Saint Louis encephalitis virus (SLEV) in the mosquito population occurring in Lubbock County, Texas. Adult mosquitoes collected in Lubbock County during 2002 and 2003 represented 7 genera, with Culex tarsalis and Ochlerotatus sollicitans being the predominant species collected. Mosquitoes were initially screened for WNV and SLEV by using the VecTest antigen panel assay. Positive VecTest results were confirmed by reverse transcriptase-polymerase chain reaction. West Nile virus-positive pools of mosquitoes were detected in 2002 and 2003, with the majority of the positive pools consisting of Cx. tarsalis. None of the mosquito pools tested positive for SLEV.