Paloma I. Beamer

Migration of contaminated soil and airborne particulates to indoor dust.

We have developed a modeling and measurement framework for assessing transport of contaminated soils and airborne particulates into a residence, their subsequent distribution indoors via resuspension and deposition processes, and removal by cleaning and building exhalation of suspended particles. The model explicitly accounts for the formation of house dust as a mixture of organic matter (OM) such as shed skin cells and organic fibers, soil tracked-in on footwear, and particulate matter (PM) derived from the infiltration of outdoor air. We derived formulas for use with measurements of inorganic contaminants, crustal tracers, OM, and PM to quantify selected transport parameters. Application of the model to residences in the U.S. Midwest indicates that As in ambient air can account for nearly 60% of the As input to floor dust, with soil track-in representing the remainder. Historic data on Pb contamination in Sacramento, CA, were used to reconstruct sources of Pb in indoor dust, showing that airborne Pb was likely the dominant source in the early 1980s. However, as airborne Pb levels declined due to the phase-out of leaded gasoline, soil resuspension and track-in eventually became the primary sources of Pb in house dust.

Quantified activity pattern data from 6 to 27-month-old farmworker children for use in exposure assessment

This study was conducted to describe exposure prone behaviors of infants and toddlers in the farmworker community. Analysis of hand and mouth contact frequencies and durations aids understanding of how children interact with their environment and are exposed via contact with surfaces. All 23 participating children (8 female infants, 5 male infants, 5 female toddlers and 5 male toddlers) lived with at least one farmworker. Children were videotaped at home for 2-6 h. Video footage was translated into micro-level activity time series (MLATS) for both hands and the mouth. MLATS were processed to calculate hourly duration in microenvironments, contact frequency, hourly contact duration and median contact duration. The median hourly duration spent indoors was 53 min/h. The median hand-to-mouth frequency was 15.2 events/h and the median object-to-mouth frequency was 27.2 events/h. The hourly mouthing duration was 1.2 and 2.2 min/h with the hands and objects, respectively. The median mouthing duration with hands and objects was 2 s. The median contact frequency for both hands combined was 689.4 events/h with an hourly contact duration of 100.5 min/h and a median contact duration of 3s. Infants had higher mouthing frequencies with non-dietary objects while toddlers had higher mouthing frequencies with objects associated with pica (i.e., paper). Boys had higher contact frequencies while girls had longer contact durations. These sub-group differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. Contact frequencies in this study are higher than current US EPA recommendations, questioning their protective value for infants and toddlers.

Home gardening near a mining site in an arsenic-endemic region of Arizona: Assessing arsenic exposure dose and risk via ingestion of home garden vegetables, soils, and water

The human-health risk posed by gardening near a legacy mine and smelter in an arsenic-endemic region of Arizona was characterized in this study. Residential soils were used in a greenhouse study to grow common vegetables, and local residents, after training, collected soil, water, and vegetables samples from their home gardens. Concentrations of arsenic measured in water, soil, and vegetable samples were used in conjunction with reported US intake rates to calculate the daily dose, Incremental Excess Lifetime Cancer Risk (IELCR), and Hazard Quotient for arsenic. Relative arsenic intake dose decreased in order: water>garden soils>homegrown vegetables, and on average, each accounted for 77, 16, and 7% of a residential gardeners daily arsenic intake dose. The IELCR ranges for vegetables, garden soils, and water were 10(-8) to 10(-4), 10(-6) to 10(-4), and 10(-5) to 10(-2), respectively. All vegetables (greenhouse and home garden) were grouped by scientific family, and the risk posed decreased as: Asteraceae≫Fabaceae>Amaranthaceae>Liliaceae>Brassicaceae>Solanaceae≫Cucurbitaceae. Correlations observed between concentrations of arsenic in vegetables and soils were used to estimate a maximum allowable level of arsenic in soil to limit the excess cancer risk to 10(-6). The estimated values are 1.56 mg kg(-1), 5.39 mg kg(-1), 11.6 mg kg(-1) and 12.4 mg kg(-1) for the Asteraceae, Brassicaceae, Fabaceae, and Amaranthaceae families, respectively. It is recommended that home gardeners: sample their private wells annually, test their soils prior to gardening, and, if necessary, modify their gardening behavior to reduce incidental soil ingestion. This study highlights the importance of site-specific risk assessment, and the need for species-specific planting guidelines for communities.

Video methods in the quantification of children's exposures

In 1994, Stanford Universitys Exposure Research Group (ERG) conducted its first pilot study to collect micro-level activity time series (MLATS) data for young children. The pilot study involved videotaping four children of farm workers in the Salinas Valley of California and converting their videotaped activities to valuable text files of contact behavior using video-translation techniques. These MLATS are especially useful for describing intermittent dermal (i.e., second-by-second account of surfaces and objects contacted) and non-dietary ingestion (second-by-second account of objects or hands placed in the mouth) contact behavior. Second-by-second records of children contact behavior are amenable to quantitative and statistical analysis and allow for more accurate model estimates of human exposure and dose to environmental contaminants. Activity patterns data for modeling inhalation exposure (i.e., accounts of microenvironments visited) can also be extracted from the MLATS data. Since the pilot study, ERG has collected an immense MLATS data set for 92 children using more developed and refined videotaping and video-translation methodologies. This paper describes all aspects required for the collection of MLATS including: subject recruitment techniques, videotaping and video-translation processes, and potential data analysis. This paper also describes the quality assurance steps employed for these new MLATS projects, including: training, data management, and the application of interobserver and intraobserver agreement during video translation. The discussion of these issues and ERGs experiences in dealing with them can assist other groups in the conduct of research that employs these more quantitative techniques.

A meta-analysis of children's object-to-mouth frequency data for estimating non-dietary ingestion exposure.

To improve estimates of non-dietary ingestion in probabilistic exposure modeling, a meta-analysis of childrens object-to-mouth frequency was conducted using data from seven available studies representing 438 participants and ∼1500 h of behavior observation. The analysis represents the first comprehensive effort to fit object-to-mouth frequency variability and uncertainty distributions by indoor/outdoor location and by age groups recommended by the US Environmental Protection Agency for assessing childhood exposures. Weibull distributions best fit the observed data from studies with no statistical differences, and are presented by study, age group, and location. As age increases, both indoor and outdoor object-to-mouth frequencies decrease. Object-to-mouth frequency is significantly greater indoors (2–32 contacts/h) than outdoors (average 1–9 contacts/h). This paper compares results to a similar hand-to-mouth frequency meta-analysis. Children who tend to mouth hands indoors also tend to mouth hands outdoors; children who tend to mouth objects indoors tend to mouth objects outdoors. However, children who tend to mouth objects do not necessarily have a tendency to mouth hands. Unlike for hand-to-mouth frequency, a statistical difference was found among the various studies for object-to-mouth frequency. This could be due to different definitions for object mouthing across the studies considered. The analysis highlights the need for additional object-to-mouth data (indoors and especially outdoors) for various age groups using standardized collection and analysis.

Hazard-Ranking of Agricultural Pesticides for Chronic Health Effects in Yuma County, Arizona

With thousands of pesticides registered by the United States Environmental Protection Agency, it not feasible to sample for all pesticides applied in agricultural communities. Hazard-ranking pesticides based on use, toxicity, and exposure potential can help prioritize community-specific pesticide hazards. This study applied hazard-ranking schemes for cancer, endocrine disruption, and reproductive/developmental toxicity in Yuma County, Arizona. An existing cancer hazard-ranking scheme was modified, and novel schemes for endocrine disruption and reproductive/developmental toxicity were developed to rank pesticide hazards. The hazard-ranking schemes accounted for pesticide use, toxicity, and exposure potential based on chemical properties of each pesticide. Pesticides were ranked as hazards with respect to each health effect, as well as overall chronic health effects. The highest hazard-ranked pesticides for overall chronic health effects were maneb, metam-sodium, trifluralin, pronamide, and bifenthrin. The relative pesticide rankings were unique for each health effect. The highest hazard-ranked pesticides differed from those most heavily applied, as well as from those previously detected in Yuma homes over a decade ago. The most hazardous pesticides for cancer in Yuma County, Arizona were also different from a previous hazard-ranking applied in California. Hazard-ranking schemes that take into account pesticide use, toxicity, and exposure potential can help prioritize pesticides of greatest health risk in agricultural communities. This study is the first to provide pesticide hazard-rankings for endocrine disruption and reproductive/developmental toxicity based on use, toxicity, and exposure potential. These hazard-ranking schemes can be applied to other agricultural communities for prioritizing community-specific pesticide hazards to target decreasing health risk.

Young children's hand contact activities: An observational study via videotaping in primarily outdoor residential settings

Microlevel activity time series (MLATS) data were gathered on hand contact activities of 38 children (1–6 years old) by videotaping in primarily outdoor residential environments. The videotape recordings were then translated into text files using a specialized software called VirtualTimingDevice™. Contact frequency (contacts/h), duration per contact (s/contact), and hourly contact duration (min/h) were summarized for outdoor hand contacts with 15 distinct object/surface categories (“Animal”, “Body”, “Clothes/Towels”, “Fabric”, “Floor”, “Food”, “Footwear”, “Metal”, “Non-dietary Water”, “Paper/Wrapper”, “Plastic”, “Rock/Brick”, “Toys”, “Vegetation/Grass”, and “Wood”) and two aggregate object/surface categories (“Non-dietary objects/surfaces” and “Total objects/surfaces”). For outdoor both hand contacts with “Total objects/surfaces”, contact frequencies ranged from 229.9 to 1517.7 contacts/h, median durations/contact ranged from <1 to 5 s, and hourly contact durations ranged from 42.6 to 102.2 m/h.The data were analyzed for significant differences in hand contact activities as a function of (1) age, (2) location, (3) gender, and (4) hand. Significant differences (P⩽0.05) were found for all four factors analyzed. Hourly contact durations with “Non-dietary objects/surfaces” and “Total objects/surfaces” increased with age (P=0.01, rs=0.42 and P=0.005, rs=0.46, respectively), while contact frequencies and hourly contact durations with “Wood” decreased with age (P=0.02, rs=−0.38 and P=0.05, rs=−0.32, respectively). Location was found to affect contact frequencies and hourly contact durations with certain objects/surfaces. For example, contact frequencies and hourly contact durations with “Fabric” were higher indoors (P=0.02 for both), while contact frequencies and hourly contact durations with “Vegetation/Grass” were higher outdoors (P=0.02 and P=0.04, respectively). Girls had longer hourly contact durations with “Footwear” (P=0.02), “Non-dietary objects/surfaces” (P=0.03), and “Total objects/surfaces” (P=0.01) than boys. The right hand had longer hourly contact durations with objects that are often manipulated with the hand (e.g., “Toys” (P=0.0002)), while the left hand had longer hourly contact durations with passively touched objects/surfaces (e.g., “Clothes/Towels” (P=0.003) and “Floor” (P=0.04)).

Young Children's Mouthing Behavior: An Observational Study via Videotaping in a Primarily Outdoor Residential Setting

ABSTRACTDetailed information on childrens mouthing activities helps researchers assess childrens exposure to toxicants via the non-dietary ingestion route (i.e., exposure resulting from contacts between the mouth and non-dietary objects such as fingers, toys, and dirt). For the analyses presented in this article, 38 children (20 female and 18 male) aged 1 to 6 years were videotaped for 2 hours each during natural play primarily in the outdoor residential environment.The data were analyzed separately by location (i.e., indoor or outdoor). For each location, mouthing frequency, contact duration, and hourly duration data were analyzed along gender and ≤ 24 months > 24 months age groupings. Several significant differences were found for mouthing activities occurring outdoors. Children ≤ 24 months of age were found to have significantly longer contact durations with the hands than children > 24 months of age (p = 0.04). Furthermore, for all ages, frequencies of mouthing contacts with the hands and non-dietar...

Differences in Metal Concentration by Particle Size in House Dust and Soil

The majority of particles that adhere to hands are <63 μm in diameter yet risk assessments for soil remediation are typically based on soil samples sieved to <250 μm. The objective of our study was to determine if there is a significant difference in metal concentration by particle size in both house dust and soil. We obtained indoor dust and yard soil samples from 10 houses in Tucson, Arizona. All samples were sieved to <63 μm and 63 to <150 μm and analyzed for 30 elements via ICP-MS following nitric acid digestion. We conducted t-tests of the log-transformed data to assess for significant differences that were adjusted with a Bonferroni correction to account for multiple comparisons. In house dust, significant differences in concentration were observed for Be, Al, and Mo between particles sizes, with a higher concentration observed in the smaller particle sizes. Significant differences were also determined for Mg, Ca, Cr, Co, Cu, Ge, Zr, Ag, Ba, and Pb concentration in yard soil samples, with the higher concentration observed in the smaller particles size for each element. The results of this exploratory study indicate that current risk assessment practices for soil remediation may under estimate non-dietary ingestion exposure. This is of particular concern for young children who are more vulnerable to this exposure route due to their high hand mouthing frequencies. Additional studies with a greater number of samples and wider geographic distribution with different climates and soil types should be completed to determine the most relevant sampling practices for risk assessment.

Relative Pesticide and Exposure Route Contribution to Aggregate and Cumulative Dose in Young Farmworker Children

The Child-Specific Aggregate Cumulative Human Exposure and Dose (CACHED) framework integrates micro-level activity time series with mechanistic exposure equations, environmental concentration distributions, and physiologically-based pharmacokinetic components to estimate exposure for multiple routes and chemicals. CACHED was utilized to quantify cumulative and aggregate exposure and dose estimates for a population of young farmworker children and to evaluate the model for chlorpyrifos and diazinon. Micro-activities of farmworker children collected concurrently with residential measurements of pesticides were used in the CACHED framework to simulate 115,000 exposure scenarios and quantify cumulative and aggregate exposure and dose estimates. Modeled metabolite urine concentrations were not statistically different than concentrations measured in the urine of children, indicating that CACHED can provide realistic biomarker estimates. Analysis of the relative contribution of exposure route and pesticide indicates that in general, chlorpyrifos non-dietary ingestion exposure accounts for the largest dose, confirming the importance of the micro-activity approach. The risk metrics computed from the 115,000 simulations, indicate that greater than 95% of these scenarios might pose a risk to children’s health from aggregate chlorpyrifos exposure. The variability observed in the route and pesticide contributions to urine biomarker levels demonstrate the importance of accounting for aggregate and cumulative exposure in establishing pesticide residue tolerances in food.