Child dermal sediment loads following play in a tide flat

Abstract

Dermal contact with sediment is sometimes identified as a pathway of concern in risk assessments. Dermal exposure to sediment is poorly characterized and exposure assessors may rely on default soil adherence values. The purpose of this study was to obtain sediment adherence data for a genuine exposure scenario, child play in a tide flat. This study reports direct measurements of sediment loadings on five body parts (face, forearms, hands, lower legs and feet) after play in a tide flat. Each of nine subjects participated in two timed sessions and pre-and post-activity sediment loading data were collected. Geometric mean (geometric standard deviation) dermal loadings (mg/cm 2 ) on the face, forearm, hands, lower legs and feet for the combined sessions were 0.04 (2.9), 0.17 (3.1), 0.49 (8.2), 0.70 (3.6) and 21 (1.9), respectively. Participants' parents completed questionnaires regarding their child's typical activity patterns during tide flat play, exposure frequency and duration, clothing choices, bathing practices and clothes laundering. Data presented in this paper supplement very limited prior adherence data for sediment contact scenarios. Results will be useful to risk assessors considering exposure scenarios involving child activities at a coastal shoreline or tide flat.

Exposure to contaminated sediments during recreational activities at a public bathing place

“…Data on soil intake (assumed similar for sediment), sediment adherence and absorption factors were taken from the literature: the US EPA's Exposure Factors Handbook, Child-Specific Exposure Factors Handbook, Risk Assessment Guidance for the Superfund, and a Swedish draft guideline on contaminated soil [16][17][18][19][20][21]. However, the uncertainty is substantial and the reviewed literature seems to suggest that the absorption factors for PAH are overestimated [22][23][24][25][26].…”

Estimation of Sediment Ingestion Rates Based on Hand-to-Mouth Contact and Incidental Surface Water Ingestion

“…These estimates were based on professional judgment and were considered by TCEQ (2007) to be upper end estimates based on high frequency use. In the small study of sediment adherence factors for children playing at tidal flats immediately adjacent to a Rhode Island town, Shoaf et al (2005a) informally surveyed parents on their children's time spent at the area and provided a median estimate of 12 h per week playing in sediments during the warmer months of the year. In the case of teens and adults, Richardson and Stantec (2013) reported that on a typical day less than 2% of Canadians engage in "other outdoor activities" based on a Statistics Canada dataset collected in 2010 as part of the General Social Survey, Cycle 24 (Statistics Canada 2011).…”

“…Although the values provided in Shoaf et al (2005b) were developed using adults (as compared to Shoaf et al [2005a] developed for children playing in a tidal flat), there is no obvious reason as to why the Shoaf et al (2005b) adherence factors measured in adults could not also occur with children. In addition, the sediments were finer in the adult study which could also contribute to the higher adherence factors.…”

“…Shoaf et al (2005b) measured sediment adherence to the hands of 18 adults before and after digging for clams at a tidal flat. Although not specifically measured, it is considered likely that these sediments and those studied in Shoaf et al (2005a) were probably moist and possibly quite wet since tidal flats seldom dry out. Shoaf et al (2005b) reported a sediment adherence factor of 0.88 mg/cm 2 for the hands (as a geometric mean with a 95% confidence range of 0.35 to 2.2 mg/cm 2 ).…”

“…Shoaf et al (2005a) measured sediment adherence to skin with nine children playing at a tidal flat. The geometric mean sediment loading onto the hands was 0.49 mg/cm 2 (with 95% confidence interval of 0.14 to 1.4 mg/cm 2 ).…”