Review of methods to determine hand surface area of children less than six years old: a case study

Mass and particle size distribution of household dust on children's hands

BACKGROUND

Children are vulnerable to household dust exposure; however, to date, a handful of studies simultaneously report both the mass and particle size of household dust found on children's hands after natural indoor play activities.

OBJECTIVE

Evaluate a new approach to measure dust loading and characterize particle size on a child's hands using a Coulter Counter.

METHODS

The volume of particles rinsed off children's hands was measured through counting and sizing particles (using a Coulter Counter), followed by multiplying the particle volume by the density of dust collected from the home. This mass was then normalized per total hand surface area to obtain dust loading on children's hands. Results were compared by region (North Carolina, Florida, Arizona), age groups (6 months to 6 years), and social demographics (gender, race, ethnicity) for 101 children.

RESULTS

The estimated median density for household dust was 1.54 g/cm3, with an average of 1.58 g/cm3 (SD = 0.43). The overall median dust loading on children's hands was 11.13 μg/cm2 (per total hand surface area), with a range of 0.004-167.6 μg/cm2. No statistical difference was observed by region, age, nor social demographics (p > 0.05). The majority of particles (90%) from children's hand rinses had a diameter (D90,v) <35 μm; however, these small particles represent a fraction of the total mass. This new approach succeeded at obtaining dust loadings and particle size simultaneously from the same sample, in contrast to current methods that would have required multiple methods and sample types.

IMPACT STATEMENT

Children are vulnerable to household dust due to their play behavior; however, to date, limited measurements are available for the mass and particle size of dust on children's hands after natural indoor play activities. We propose a new approach to facilitate dust loading measurements, while also obtaining the particle size of dust, through the usage of a Coulter Counter. Results showed that 90% of particles were <35 μm, which is four times smaller than the current guidelines threshold (150 μm) for risk assessments that utilize estimates for particles found on hands.

Methodologies for the collection of parameters to estimate dust/soil ingestion for young children

Background

Heavy metals, pesticides and a host of contaminants found in dust and soil pose a health risk to young children through ingestion. Dust/soil ingestion rates for young children can be estimated using micro-level activity time series (MLATS) as model inputs. MLATS allow for the generation of frequency and duration of children's contact activities, along with sequential contact patterns. Models using MLATS consider contact types, and transfer dynamics to assign mechanisms of contact and appropriate exposure factors for cumulative estimates of ingestion rates.

Objective

The objective of this study is to describe field implementation, data needs, advanced field collection, laboratory methodologies, and challenges for integrating into and updating a previously validated physical-stochastic MLATS-based model framework called the Child-Specific Aggregate Cumulative Human Exposure and Dose (CACHED) model. The manuscript focuses on describing the methods implemented in the current study.

Methods

This current multidisciplinary study (Dust Ingestion childRen sTudy [DIRT]) was implemented across three US regions: Tucson, Arizona; Miami, Florida and Greensboro, North Carolina. Four hundred and fifty participants were recruited between August 2021 to June 2023 to complete a 4-part household survey, of which 100 also participated in a field study.

Discussion

The field study focused on videotaping children's natural play using advanced unattended 360° cameras mounted for participants' tracking and ultimately conversion to MLATS. Additionally, children's hand rinses were collected before and after recording, along with indoor dust and outdoor soil, followed by advanced mass analysis. The gathered data will be used to quantify dust/soil ingestion by region, sociodemographic variables, age groups (from 6 months to 6 years), and other variables for indoor/outdoor settings within an adapted version of the CACHED model framework.

Significance

New innovative approaches for the estimation of dust/soil ingestion rates can potentially improve modeling and quantification of children's risks to contaminants from dust exposure.

Quantified Activity Patterns for Young Children in Beach Environments Relevant for Exposure to Contaminants

In a study to evaluate beach play activities, 120 children were videotaped to observe and quantify factors that could influence their exposure to contaminants in the beach environment. Children aged 1 to 6 years were followed by researchers with video cameras at beaches (two in Miami, Florida and two in Galveston, Texas) for approximately one hour each. Factors evaluated included time spent in various beach locations, various activities engaged in, and various surfaces contacted (including contacts by hand and mouth). Activities recorded in the videos were transcribed to text files to allow for quantitative analyses. Across all sexes, age groups, and beaches, Wading was the most common activity and Seawater was the most common location where children played. The left hand was found to not be in contact with objects most of the time, while the right hand, considered the most dominant hand in most cases, contacted Plastic-Toys the most. Although activity patterns collection through videotaping and videotranslation can be labor-intensive, once collected, they can be widely useful for estimates of exposures to all contaminants in the beach environment (e.g., microorganisms and chemicals) as well as UV exposure, with considerations for whether the contaminants are found in water, sand or both. These activity patterns were collected to potentially look at exposures following the Deepwater Horizon 2010 Spill.

Soil-skin adherence measures from hand press trials in a Gulf study of exposures

Marine oil spills and the resulting environmental contamination is common along coastal areas; however, information is lacking about the safety of impacted beaches for public use, especially for the most vulnerable population: children. One route of exposure for children at oil impacted beaches is through contact with sands. The purpose of this study was to evaluate beach sand skin adherence for children under the age of seven. Each of 122 children participated in a hand press trial conducted at one of four different U.S. beaches (two in Miami, FL, and two in Galveston, TX USA). During the hand press trials, hand conditions of the children were randomized (dry, wet, or with sunscreen), and soil adherence (mass of sand per palmar surface area of the hand) and the maximum pressure applied (force applied per area of hand) was measured and calculated. Each child was instructed to press their hands on a soil laden tray for 5 s and pressure of contact was measured using a scale. Results (n = 98) showed that the average soil adherence for both palmar hands across the four beaches ranged from 0.200 to 234 mg/cm² with an average of 35.7 mg/cm², with boys (40.4 mg/cm²) showing slightly higher means than girls (31.7 mg/cm²), but these differences were not significant even after adjusting for age. Among the three conditions evaluated, the highest loading was measured for children with wet hands (mean 65.3 mg/cm²), followed by dry hands (mean 24.5 mg/cm²). Sunscreen hands (mean 23.2 mg/cm²) had the lowest loadings. The pressure of contact ranged from 0.180 to 1.69 psi and varied by age groups and by height and weight, where pressure of contact did not have a significant influence on soil adherence. The average adhered sand grain size and average ambient sand grain size both had a statistically significant impact on hand soil adherence. Overall results from this study can be utilized in exposure and risk assessment models to evaluate the possible health impacts from contaminants found in beach sands.

Estimating Health Risks to Children Associated with Recreational Play on Oil Spill-Contaminated Beaches

The human health impact from exposure to contaminated shorelines following an oil spill event has been investigated to some extent. However, the health risks to children have largely been characterized through the use of surveys and extrapolation from adult health outcomes. There is limited information on children's behaviors during beach play requiring assumptions made based on observations from play activities in home settings. The Beach Exposure and Child Health Study (BEACHES) quantified specific beach activities that can be used to inform human health risk assessments of children playing on beaches impacted by oil spills. The results of this study characterize children's risk of cancer from exposure to oil spill chemicals by incorporating exposure-related information collected from the BEACHES study and by assuming oral, dermal, and inhalation exposure routes. Point risk estimates are compared with a previous, similar study that applied default exposure parameter values obtained from the published literature. The point risk estimates informed by BEACHES data are one order of magnitude lower compared with the previous risk assessment, with dermal exposures the overall risk driver in both. Additional Monte Carlo simulations evaluating the BEACHES data provide ranges of health risks with the highest estimates associated with dermal and oral exposure routes.