The Water Model mainly represents a special case of the Dietary Model. The NHANES database contains the consumption data of three water types, namely:
- Water, direct, tap
- Water, direct, bottled
- Water, indirect, all sources
The three water types are listed in the Food table, as shown below.
They differentiate from the other foods listed in the Food table because
- they can be matched with a peculiar type of residue concentration data, the Time Series;
- they cannot be matched with the Field data.
The Time Series residue data are stored in a specific table type, the Time Series one; please refer to the Table types page for more information on this table. This table enables the user to use residue data obtained from the PRZM/EXAMS model into the dietary assessment. This model estimates the pesticide concentrations in aquatic environments over several years.
How the time series data are used in the dietary assessments
The time series values will be accepted as such only in the multi-day and within-day assessments because these are the only calendar-based analyses. The time series residue data will be matched with the 365-day water consumption diary of a subject under analysis as per the following process:
- One year randomly selected from the years included in the input is randomly selected
- If the selected year is a leap year, the extra day (29th of February) will be discarded
- The entire 365-day residue distribution is matched with the 365-day consumption days of the diary; day 1 residue will be matched with day 1 of the diary, day 2 residue with day 2 of the diary and so on.
The same year will be applied to all the water types consumed by the subject which are matched with the same time-series residue data.
CARES NG® will not make any change to the residue data contained in the time series provided by the user; it will be a user’s responsibility to check the correctness of the data. The software will only check that each year included in the time series has 365 residue values or 366 for the leap years.
In the acute assessment, the time series will be treated as monitoring data. A residue value will be randomly selected from this distribution and assigned to each consumption event or to each consumption day, as per user’s choice.
In the chronic and cancer assessments, the time series data shouldn’t be allowed; in the current version, CARES NG® can allow the use of monitoring data and it will calculate the average of the entire distribution.
Incorporating modification factors
As per the other foods, the user can provide up to three modification factors for each water type. Each residue value contained in the Time Series distribution is multiplied by the three modification factors.