Mary Kay O'Rourke

Residential environmental measurements in the national human exposure assessment survey (NHEXAS) pilot study in Arizona: preliminary results for pesticides and VOCs.

A major objective of the National Human Exposure Assessment Survey (NHEXAS) performed in Arizona was to conduct residential environmental and biomarker measurements of selected pesticides (chlorpyrifos, diazinon), volatile organic compounds (VOCs; benzene, toluene, trichloroethene, formaldehyde, 1,3-butadiene), and metals for total human exposure assessments. Both personal (e.g., blood, urine, dermal wipes, 24 h duplicate diet) and microenvironmental (e.g., indoor and outdoor air, house dust, foundation soil) samples were collected in each home in order to describe individual exposure via ingestion, inhalation, and dermal pathways, and to extrapolate trends to larger populations. This paper is a preliminary report of only the microenvironmental and dermal wipe data obtained for the target pesticides and VOCs, and provides comparisons with results from similar studies. Evaluations of total exposure from all sources and pathways will be addressed in future papers. The pesticides and VOCs all showed log-normal distributions of concentrations in the Arizona population sampled, and in most cases were detected with sufficient frequency to allow unequivocal description of the concentration by media at the 90th, 75th, and 50th (median) percentiles. Those combinations of pollutant and media, in which a large fraction of the measurements were below the detection limit of the analysis method used, included trichloroethene, 1,3-butadiene, and formaldehyde in outdoor air; chlorpyrifos and diazinon in outdoor air; and diazinon in dermal and window sill wipes. In general, indoor air concentrations were higher than outdoor air concentrations for all VOCs and pesticides investigated, and VOC levels were in good agreement with levels reported in other studies. In addition, the agreement obtained between co-located VOC samplers indicated that the low-cost diffusional badges used to measure concentrations are probably adequate for use in future monitoring studies. For the pesticides, the median levels found in indoor samples agreed well with other studies, although the levels corresponding to the upper 0.1–1% of the population were considerably higher than levels reported elsewhere, with indoor air levels as high as 3.3 and 20.5 µg/m3 for chlorpyrifos and diazinon, respectively. These data showed excellent correlation (Pearson and Spearman correlation coefficients of 0.998 and 0.998, respectively) between chlorpyrifos in indoor air and in the corresponding dermal wipes, and relatively poor correlation between chlorpyrifos in dust (µg/g or µg/m2) and dermal wipes (Pearson=0.055 µg/g and 0.015 µg/m2; Spearman=0.644 µg/g and 0.578 µg/m2). These data suggest the importance of dermal penetration of semi-volatiles as a route of residential human exposure.

Pesticide exposure and creatinine variation among young children.

Pesticide exposure may differentially impact young children; they live closer to the ground and take in greater amounts of food relative to body mass than older children or adults. We are using an organophosphate (OP) urinary biomarker screen (gas chromatography with flame photometric detection, GC/FPD) to evaluate pesticide exposure among 154 children ≤6 years of age living in a heavily farmed border (US–Mexico) community. The screen detects diethylphosphates (DEPs) and dimethylphosphates (DMPs) above a reference range of 1000 non-occupationally exposed individuals (DL=25 µg/g creatinine, Cr). At least one metabolite was detected for 28% of the subjects; many samples contained multiple biomarkers. DEP was detected in 4% of the subjects. DMP and DMTP were frequently measured (20% and 23%, respectively). Biomarker concentrations are adjusted by the bodys metabolism of Cr as an indicator of urine dilution. Cr concentrations were examined separately to evaluate their effect on internal dose measures. Cr concentrations were significantly different by season (K–W=0.83, P=0.022). Significant differences exist between the autumn:spring (P=0.038) Cr concentrations and between summer:autumn (P=0.041) Cr concentrations based on Mann–Whitney U=1070.5, z=−2.041, (P=0.041). Our analysis of NHANES III data did not reflect seasonal Cr differences for 6 year olds. No younger children were included. Absorbed daily dose (ADD) estimates were calculated for children with the highest concentrations of metabolite. Calculations are theoretical values assuming that the entirety of a given metabolite was metabolized from a single pesticide. Several class-appropriate pesticides were evaluated. For the children with the highest levels, almost all estimated ADDs exceeded the RfD. Although the actual metabolite concentrations dropped appreciably, ADD RfDs were still exceeded at the 95th percentile. The urinary OP screen was effective in identifying subjects with atypical internal doses. Daily Cr yield is a critical component in ADD calculations. Cr variability produces differences in internal dose measurement and estimates of ADD independent of exposure. Cr variability among young children needs to be examined, and caution should be applied when evaluating Cr adjusted internal doses for children.

Palynological evidence for early Holocene aridity in the southern Sierra Nevada, California

Sediments of Balsam Meadow have produced a 11,000-yr pollen record from the southern Sierra Nevada of California. The Balsam Meadow diagram is divided into three zones. (1) The Artemisia zone (11,000–7000 yr B.P.) is characterized by percentages of sagebrush (Artemisia) and other nonarboreal pollen higher than can be found in the modern local vegetation. Vegetation during this interval was probably similar to the modern vegetation on the east slope of the Sierra Nevada and the climate was drier than that of today. (2) Pinus pollen exceeded 80% from 7000 to 3000 yr B.P. in the Pinus zone. The climate was moister than during the Artemisia zone. (3) Fir (Abies, Cupressaceae, and oak (Quercus) percentages increased after 3000 yr B.P. in the Abies zone as the modern vegetation at the site developed and the present cool-moist climatic regime was established. Decreased fire frequency after 1200 yr B.P. is reflected in decreased abundance of macroscopic charcoal and increased concentration of Abies magnifica and Pinus murrayana needles.

Association between body mass index and arsenic methylation efficiency in adult women from southwest U.S. and northwest Mexico

Human arsenic methylation efficiency has been consistently associated with arsenic-induced disease risk. Interindividual variation in arsenic methylation profiles is commonly observed in exposed populations, and great effort has been put into the study of potential determinants of this variability. Among the factors that have been evaluated, body mass index (BMI) has not been consistently associated with arsenic methylation efficiency; however, an underrepresentation of the upper BMI distribution was commonly observed in these studies. This study investigated potential factors contributing to variations in the metabolism of arsenic, with specific interest in the effect of BMI where more than half of the population was overweight or obese. We studied 624 adult women exposed to arsenic in drinking water from three independent populations. Multivariate regression models showed that higher BMI, arsenic (+3 oxidation state) methyltransferase (AS3MT) genetic variant 7388, and higher total urinary arsenic were significantly associated with low percentage of urinary arsenic excreted as monomethylarsonic acid (%uMMA) or high ratio between urinary dimethylarsinic acid and uMMA (uDMA/uMMA), while AS3MT genetic variant M287T was associated with high %uMMA and low uDMA/uMMA. The association between BMI and arsenic methylation efficiency was also evident in each of the three populations when studied separately. This strong association observed between high BMI and low %uMMA and high uDMA/uMMA underscores the importance of BMI as a potential arsenic-associated disease risk factor, and should be carefully considered in future studies associating human arsenic metabolism and toxicity.

Recognition of pollen and other particulate aeroantigens by immunoblot microscopy

Most grass-pollen types appear identical by normal light microscopy. Restricted antigenic cross-reactivity of Cynodon dactylon (Bermuda grass) pollen allowed development of a new method to identify antigens associated with grass-pollen grains. Pollen applied to the surface of an adhesive tape was blotted onto nitrocellulose, and the blots were identified by anti-Bermuda-grass antibodies, second antibody, and fluorescence microscopy. Of the 44 species of grass pollen studied for specificity of the method, the only species to demonstrate uniformly bright staining were Cynodon dactylon, Elymus triticoides, Elymus cinereus, and Koeleria cristata. Thirty-one species were negative, and nine other species demonstrated occasional brightly fluorescent spots, suggesting contamination. The immunoblotting method was used to study Tucson air collected continuously by a Burkard pollen and spore trap throughout April 1986. Each 2-hour transect of the adhesive tape from the trap was examined by immunoblotting and by normal light microscopy to compare antigen particle counts with grass-pollen counts. The mean antigen-particle concentration, 52.8/m3 of air, was higher than the mean grass-pollen concentration, 21.9/m3 of air, suggesting presence of amorphous Bermuda-grass antigens in air samples. Antigen-particle concentration, not grass-pollen concentration, correlated significantly with wind velocity, temperature, and time of day.

Exposure apportionment: ranking food items by their contribution to dietary exposure.

This paper identifies and ranks food items by estimating their contribution to the dietary exposure of the US population and 19 subpopulation groups. Contributions to dietary exposures to arsenic, cadmium, chromium, lead, nickel, benzene, chlorpyrifos, and diazinon are estimated using either the Dietary Exposure Potential Model (DEPM) approach, the National Human Exposure Assessment Survey Arizona (NHEXAS-AZ) approach or the combination of the two. The DEPM is a computer model that uses several national databases of food consumption and residue concentrations for estimating dietary. The DEPM approach ranks the contribution of food items to the total dietary exposure using two methods, the direct method that ranks contributions by population exposure magnitude and the weighted method that ranks by subpopulation exposure magnitude. The DEPM approach identifies highly exposed subpopulations and a relatively small number of food items contributing the most to dietary exposure. The NHEXAS-AZ approach uses the NHEXAS-AZ database containing food consumption data for each subject and chemical residues of a composite of food items consumed by each subject in 1 day during the sampling week. These data are then modeled to obtain estimates of dietary exposure to chemical residues. The third approach uses the NHEXAS-AZ consumption data with residue values from the national residue database. This approach also estimates percent contributions to exposure of each ranked food item for the Arizona population. Dietary exposures estimated using the three approaches are compared. The DEPM results indicate groups with highest dietary exposures include Nonnursing Infants, Children 1–6, Hispanic, Non-Hispanic White, Western, Northeast and Poverty 0–130%. The use of the Combined National Residue Database (CNRD) identifies 43 food items as primary contributors to total dietary exposure; they contribute a minimum of 68% of the total dietary exposure to each of the eight chemical residues. The percent contribution of ranked food items estimated using the NHEXAS samples is smaller than those obtained from the western US population via the DEPM. This indicates differences in consumption characteristics of the two groups with respect to the ranked food items. Six of 15 food items consumed by the NHEXAS-AZ subjects per day are ranked food items contributing between 56% and 70% of the estimated NHEXAS-AZ dietary exposure to each of the eight chemical residues. The difference between total dietary exposure estimates from the DEPM and NHEXAS-AZ approaches varies by chemical residue and is attributable to differences in sampling and analytical methods, and geographic areas represented by the data. Most metal exposures estimated using the NHEXAS consumption data with the CNRD have lower values than those estimated via the other approaches, possibly because the NHEXAS-AZ residue values are higher than the CNRD values. In addition, exposure estimates are seemingly affected by the difference in demographic characteristics and factors that affect types and amounts of food consumed. Efficient control strategies for reducing dietary exposure to chemical residues may be designed by focusing on the relatively small number of food items having similar ingredients that contribute substantively to the total ingestion exposure.

The National Human Exposure Assessment Survey (NHEXAS) study in Arizona—introduction and preliminary results

The objective of the National Human Exposure Assessment Survey (NHEXAS) in Arizona is to determine the multimedia distribution of total human exposure to environmental pollutants in the classes of metals, pesticides, and volatile organic compounds (VOCs) for the population of Arizona. This was accomplished by studying a probability-based sample of the total population in Arizona with a nested design for the different stages of sampling (954 Stage I, 505 Stage II, and 179 Stage III participants). This report compares the study population demographics with those from the U.S. Census and provides preliminary data on the distributions of the example pollutant for each class, lead for metals, chlorpyrifos for pesticides, and benzene for metals. The probability-based sample age and gender demographics compare reasonably well with the Census data (1990 Census and 1996 Census Estimate). The race/ethnicity compared less well with 21% Hispanics in the 1996 Census Estimate and 42% Hispanics in the entire NHEXAS-Arizona sample and 30% Hispanics as Stage III participants for this study. The chemical analyses of the various media (yard soil, foundation soil, house dust, indoor air, outdoor air, drinking water, food, and beverage) show generally low levels of the representative pollutants. The 50th percentiles of the distributions are generally near or below the analytical detection limits, and applicable Federal action limits were rarely exceeded.

Evaluations of primary metals from NHEXAS Arizona: Distributions and preliminary exposures

NHEXAS AZ is a multimedia, multipathway exposure assessment survey designed to evaluate metals and other analytes. This paper reports the analyte-specific concentration distributions in each of the media examined (air, soil, house dust, food, beverage, and water), for various methodologies used (inductively coupled plasma-atomic emission spectroscopy and hydride generation-atomic absorption spectroscopy). Results are reported for the five primary metals (Pb, As, Cd, Cr, and Ni). Ingestion was the most important pathway of exposure. Metal concentrations in air were very low (ng/m3) and found only above the 90th percentile. Metals were commonly found in house dust and soil. Exposure transfer coefficients minimize the importance of this component for those over the age of 6 years. When ranked by exposure, food, beverage, and water appeared to be the primary contributors of metal exposure in NHEXAS AZ. For instance, at the 90th percentile, Pb was undetected in air, found at 131 and 118 µg/m3 in floor dust and soil, respectively, and measured at 16 µg/kg in food, 7.1 µg/kg in beverage, and 2.0 and 1.3 µg/l in drinking and tap water, respectively. We calculated preliminary estimates of total exposure (µg/day) for each participant and examined them independently by age, gender, and ethnicity as reported by the subjects in the NHEXAS questionnaire. At the 90th percentile for Pb, total exposures were 64 µg/day across all subjects (n=176); adult men (n=55) had the greatest exposure (73 µg/day) and children (n=35) the least (37 µg/day). Hispanics (n=54) had greater exposure to Pb (68 µg/day) than non-Hispanics (n=119; 50 µg/day), whereas non-Hispanics had greater exposure for all other metals reported. These results have implications related to environmental justice. The NHEXAS project provides information to make informed decisions for protecting and promoting appropriate public health policy.

Evidence for mutualism between a flower-piercing carpenter bee and ocotillo: use of pollen and nectar by nesting bees

Abstract. 1 Carpenter bees (Xylocopa californica arizonensis) in west Texas, U.S.A., gather pollen and ‘rob’ nectar from flowers of ocotillo (Fouquieria splendens). When common, carpenter bees are an effective pollen vector for ocotillo. We examined ocotillos importance as a food source for carpenter bees. 2 The visitation rate of carpenter bees to ocotillo flowers in 1988 averaged 0.51 visits/flower/h and was 4 times greater than that of queen bumble bees (Bombus pennsylvanicus sonorus), the next most common visitor. Nectar was harvested thoroughly and pollen was removed from the majority of flowers. Hummingbird visits were rare. 3 Pollen grains from larval food provisions were identified from sixteen carpenter bee nests. On average, 53% of pollen grains sampled were ocotillo, 39% were mesquite (Prosopis glandulosa), and 8% were Zygophyllaceae (Larrea tridentata or Guaiacum angustifolium). Carpenter bee brood size averaged 5.8 per nest. 4 We measured the number of flowers, and production of pollen and nectar per flower by mature ocotillo plants, as well as the quantity of pollen and sugar in larval provisions. An average plant produced enough pollen and nectar sugar to support the growth of eight to thirteen bee larvae. Ocotillo thus has the potential to contribute significantly to population growth of one of its key pollinators. 5 Although this carpenter bee species, like others, is a nectar parasite of many plant species, it appears to be engaged in a strong mutualism with a plant that serves as both a pollen and as a nectar source during carpenter bee breeding periods.

A comparison of regional atmospheric pollen with pollen collected at and near homes

Abstract Three sampling techniques were used to determine how pollen concentrations obtained from atmospheric sampling devices compare to pollen concentrations in the home environment. Burkard pollen samplers were placed on rooftops at 4 locations in Tucson, Az. (USA) to sample regional atmospheric pollen; nearby, Rotorod® (rotorod) samplers collected atmospheric pollen in the home environment at 55 locations for 3 consecutive days during each season. Pollen concentrations from rotorod and Burkard traps show that pollen is rare inside homes and only occurs when pollen production is high. No differences in pollen concentration were found between rooms of any home, and frontyards generally had higher pollen concentrations than backyards. Pollen concentrations near homes were generally lower than regional pollen concentrations. Correlations were low even though pollen taxa were similar. Floor sweepings from homes contained pollen concentrations as high as 5.5 million pollen grains/g house dust. We conclude t...