Estimate the chronic daily intake of 1,1,1-trichloroethane from exposure to
city water supply that contains a 1,1,1-trichloroethane concentration equal to the
drinking water standard of 0.2 mg/L. Assume the exposed individual is a child who
consumes water at the child rate for 5 years, that she swims once a week for 30
minutes, and that she takes a short (10 minute) bath every day. Assume her average
age over the exposure period is 8. Assume that the average air concentration of 1,1,1-
trichloroethane during the bath is 2 µg/L. Assume the dermal uptake form water (PC) is
0.0060 m/h and that direct dermal absorption during bathing is no more than 50 percent
of the available 1,1,1-trichloroethane because she is not completely submerged.
To estimate the chronic daily intake of 1,1,1-trichloroethane from exposure to the city water supply, we need to consider the different exposure pathways and calculate the intake for each pathway separately. Then, we can sum up the contributions to get the total chronic daily intake.
Here's how we can calculate it step by step:
1. Calculate the intake from drinking water:
- The concentration of 1,1,1-trichloroethane in the city water supply is 0.2 mg/L.
- Convert this concentration to µg/L by multiplying by 1000: 0.2 mg/L = 200 µg/L.
- The child consumes water at the child rate for 5 years.
- Calculate the daily intake from drinking water: 200 µg/L * daily water consumption rate for a child * 365 days * 5 years.
Note: The daily water consumption rate for a child may vary, but for estimation purposes, you can assume it to be around 1 liter/day or 1000 mL/day.
2. Calculate the intake from swimming:
- The average air concentration of 1,1,1-trichloroethane during the bath is 2 µg/L (micrograms per liter).
- The child swims once a week for 30 minutes.
- Calculate the intake from swimming: 2 µg/L * average water ingestion rate during swimming * 52 weeks * 30 minutes.
Note: The average water ingestion rate during swimming can vary depending on the activity level, but for estimation purposes, assume 30 mL/minute.
3. Calculate the intake from bathing:
- The child takes a short (10 minute) bath every day.
- The dermal uptake factor (PC) is 0.0060 mL/h (milliliters per hour).
- The direct dermal absorption during bathing is assumed to be no more than 50% (0.5) of the available 1,1,1-trichloroethane because the child is not completely submerged.
- Calculate the intake from bathing: 0.5 * dermal uptake factor (PC) * bath duration * bathing frequency.
Once you have calculated the intake from each pathway separately, you can sum them up to obtain the total chronic daily intake of 1,1,1-trichloroethane from exposure to the city water supply.
Please note that these calculations are based on the assumptions and data provided. If you have more specific information or data, you may need to modify the calculations accordingly.