Human Environment Exposure Parameters
2.1.1. Drinking Water
Khan and Stralka (2009) analyzed combined data sets from the Continuing Survey of Food Intakes by Individuals (CSFII) from 1994-1996 and 1998 as well as Supplemental Data (Kahn, 2008) to examine ingestion rates per capita of both children and persons of adult age. The study survey for both direct water ingestion (directly from a beverage) and indirect water ingestion (water added to foods and beverages during preparation), however, commercial and intrinsic water ingestion (water from soda or beer) was not included in the survey.
The study surveyed the ingestion rates of more than 20,000 individuals, with 10,000 under the age of 11, and 9,000 under the age of 9. Each person surveyed was assigned a sample weight, which was then taken into account when mean and percentile water injection rates were calculated.
The study is especially important in terms of water ingestion recommendations as the sample size is considered large enough to be representative of the U.S. population, spans across economic status, and for children less than three years of age the sample size is larger than any of the most up-to-date studies conducted.
a Direct water: water ingested directly as a beverage.
b Indirect water: water added in preparation of food or beverages.
c 90% CI: 90% confidence interval about the estimated means.
d 90% BI: 90% bootstrap interval about the estimated percentiles.
Source of data: 1994-1996 and 1998 USDA Continuing Survey of Food Intakes by Individuals (CSFII).
(Kahn H.D. and Stralka K., 2009)
2.1.2. Recreational Water
Chloroisocyanurates are added to outdoor pools to stabilize chlorine disinfectants used in cleaning, as they decompose slowly into chlorine and cyanuric acid. Studies have shown that cyanuric acid may not be toxic to swimmers as it appears to pass through the body without being metabolized.
In this study, fifty-three recreational swimmers were observed in a community pool that was disinfected with cyanuric acid stabilized chlorine. Participants were asked to swim for at least 45 minutes, and not to swim the day before or the day after the study. Urine samples were collected for 24 hours following their swim and were analyzed to determine water ingestion in adults and non-adults.
Original survey data can be obtained by this link.
a: Non-parametric Wilcoxon Rank Sum test was applied for statistical analysis.
b: The comparison between adults and non-adults are significantly different at 5% level. The comparison between different gender groups was evaluated and not significant.
(Dufour et al, 2006)
References Dufour A, Evans O, Behymer T and Cantu R. (2006) Water ingestion during swimming activities in a pool: A pilot study. Journal of Water Health. 04.4: 425-430. Full text
(Mark Nicas, University of California Berkeley)