Alesia Ferguson

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.

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.

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...

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.

Soil-skin adherence from carpet: Use of a mechanical chamber to control contact parameters

A computer-controlled mechanical chamber was used to control the contact between carpet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. Mass soil transfers were converted to adherence factors (mg/cm2) for use in models that estimate dermal exposure to contaminants found in soil media. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 sec) were varied for 369 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 μm and ≥139.7 < 381) were used. Chamber probes were used to record temperature and humidity. Log transformation of the sand/soil transfers was performed to normalize the distribution. Estimated adjusted means for experimental conditions were exponentiated in order to express them in the original units. Mean soil mass transfer to cadaver skin (0.74 mg/cm2) was higher than to cotton sheets (0.21 mg/cm2). Higher pressure (p < 0.0001), and larger particle size (p < 0.0001) were also all associated with larger amounts of soil transfer. The original model was simplified into two by adherence material type (i.e., cadaver skin and cotton sheets) in order to investigate the differential effects of pressure, time, soil size, and soil type on transfer. This research can be used to improve estimates of dermal exposure to contaminants found in home carpets.

Comparisons of computer-controlled chamber measurements for soil–skin adherence from aluminum and carpet surfaces, ☆ ☆☆

A computer-controlled mechanical chamber was used to control the contact between carpet and aluminum sheet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. The contact parameters of pressure (10-50 kPa) and time (10-50s) were varied for 768 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil particle sizes (<139.7 and 139.7<381 microm) were used. Mean soil mass transfer to cadaver skin was higher than mean transfer to cotton sheets for both carpet and aluminum transfers, and also generally higher pressure was associated with larger amounts of soil transfer for all contact scenarios. The mean soil adherence from carpet was 0.37+/-0.4 mg/cm(2), while the mean soil adherence from aluminum was 0.42+/-0.6 mg/cm(2). For aluminum, smaller soil particle size was associated with more transfer (p=0.0349), while for carpet, larger soil size was associated with more transfer (p<0.0001). Soil type was significant but only for aluminum surface, where sand was associated with higher adherence (p<0.0001). This data set can be used to improve estimates of dermal exposure to contaminants found in soils and dust present in indoor environments.

Computer Controlled Chamber Measurements for Multiple Contacts for Soil-Skin Adherence from Aluminum and Carpet Surfaces

ABSTRACT A computer-controlled mechanical chamber was used to perform multiple contacts between human cadaver skin or cotton sheet samples and soil-laden carpet or aluminum foil to measure mass soil transfer. The amount transferred was measured with an analytical balance. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 s) were varied for 760 separate multiple contact experiments, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 and ≥ 139.7 < 381 μm) were used. Through parametric and non-parametric tests, this article specifically looks at the influence and interaction of these experimental parameters on the transfer of soil or sand to human skin during multiple contacts. The relationships between the amount of soil or sand that transfers for a first contact, for a second contact, and overall are also presented. On average, a second contact added an additional 8% of soil or sand to the adherence material (i.e., cloth, skin). The experimental variables of pressure, time, soil size, and soil type had less influence on the magnitude of transfer for the second contact as compared to the first contact.

Arkansas people participating in lead education (APPLE): Results of a lead-safe training program

Lead is still seen as one of the most harmful environmental toxins for young children, with the predominant source being deteriorating lead-based paint. Those at continued risk include those living in homes built before 1978, renovators and remodelers, and especially those with limited access to proper healthcare and diets. Proper training on lead-safe work practices focused on preventing and reducing the spread of lead dust can help reduce lead exposure. Presented in this paper are experiences in delivering lead-safe work practices training in six Arkansas cities, and results from pre- and post- surveys delivered before and immediately after the training. Pre- and post-surveys assess strong and weak areas of training. Participants demonstrated positive shifts in attitude and behavior towards lead-safe work practices following training. However, our research found that more emphasis should be focused on clarifying current lead exposure sources and routes for children.

A Review of the Field on Children’s Exposure to Environmental Contaminants: A Risk Assessment Approach

Background: Children must be recognized as a sensitive population based on having biological systems and organs in various stages of development. The processes of absorption, distribution, metabolism and elimination of environmental contaminants within a child’s body are considered less advanced than those of adults, making them more susceptible to disease outcomes following even small doses. Children’s unique activities of crawling and practicing increased hand-to-mouth ingestion also make them vulnerable to greater exposures by certain contaminants within specific environments. Approach: There is a need to review the field of children’s environmental exposures in order to understand trends and identify gaps in research, which may lead to better protection of this vulnerable and sensitive population. Therefore, explored here are previously published contemporary works in the broad area of children’s environmental exposures and potential impact on health from around the world. A discussion of children’s exposure to environmental contaminants is best organized under the last four steps of a risk assessment approach: hazard identification, dose-response assessment, exposure assessment (including children’s activity patterns) and risk characterization. We first consider the many exposure hazards that exist in the indoor and outdoor environments, and emerging contaminants of concern that may help guide the risk assessment process in identifying focus areas for children. A section on special diseases of concern is also included. Conclusions: The field of children’s exposures to environmental contaminants is broad. Although there are some well-studied areas offering much insight into children exposures, research is still needed to further our understanding of exposures to newer compounds, growing disease trends and the role of gene-environment interactions that modify adverse health outcomes. It is clear that behaviors of adults and children play a role in reducing or increasing a child’s exposure, where strategies to better communicate and implement risk modifying behaviors are needed, and can be more effective than implementing changes in the physical environment.