Temporal variability of microenvironmental time budgets in Maryland

Area of Science:

• Environmental health
• Exposure science
• Epidemiology

Background:

• Accurate interpretation of environmental exposure data requires understanding human time-activity patterns.
• While short-term (1-day) time-activity data are available, their reliability for chronic exposure assessments is unclear.
• Chronic health risk evaluations necessitate reliable long-term exposure data.

Purpose of the Study:

• To assess the reliability of short-term time-activity data for chronic exposure assessments.
• To characterize long-term average microenvironmental time budgets and identify influencing factors.
• To determine if 1-day time budget measurements adequately represent long-term patterns.

Main Methods:

• Collected daily time budget data for 80 individuals across seven microenvironments over a 12-month period (NHEXAS-Maryland study).
• Analyzed data by sampling cycle, day of week, and individual to identify determinants of time budgets.
• Statistically examined variations in time spent across different microenvironments.

Main Results:

• Median times in microenvironments varied significantly by time of year, day of week, and individual.
• Time budgets showed significant variability based on gender, age, education, income, and work status.
• Short-term (1-day) measures were found to be unlikely representative of long-term individual time-activity patterns.

Conclusions:

• Short-term time-activity data are insufficient for accurate chronic exposure assessments at the individual level.
• Health risk assessments may be insensitive to the timing of data collection if based on short-term patterns.
• Collecting time budget data over numerous points in time significantly improves the accuracy of individual health risk assessments.