Child environmental exposures to water and sand at the beach: Findings from studies of over 68,000 subjects at 12 beaches

Swimming and recreating in lakes, oceans, and rivers is common, yet the literature suggests children may be at greater risk of illness following such exposures. These effects might be due to differences in immunity or differing behavioral factors such as poorer hygiene, longer exposures to, and greater ingestion of potentially contaminated water and sand. We pooled data from 12 prospective cohorts (n=68,685) to examine exposures to potentially contaminated media such as beach water and sand, among children compared to adults, and conducted a simulation using self-reported time spent in the water and volume of water swallowed per minute by age, to estimate the total volume of water swallowed per swimming event by age category. Children 4–7 and 8–12 had the highest exposures to water, sand, and algae compared to other age groups. Based on our simulation, we found that children (6–12) swallow a median of 36mL (90(th) percentile= 150 mL), while adults 35 and over swallow 9 mL (90(th) percentile=64 mL) per swimming event, with male children swallowing a greater amount of water compared to females. These estimates may help to reduce uncertainty surrounding routes and durations of recreational exposures and can support the development of chemical and microbial risk assessments.