Time-activity patterns

A constraint for using the indirect method is that the residence time of the person (termed time-activity pattern) needs to be known together with the pollution concentrations in each of the microenvironment at the time the person is present. 

Schulz, C., Becker, K., Friedrich, C., Helm, D., Hoffmann, K., Krause, C. and Seifert, B. (1999) The German Environmental Survey 1990/92 (GERES II) time-activity patterns of the general population in Germany. Epidemiology, 10, 200P. 

Leech JA, Wilby K, McMullen E (1999) Environmental tobacco smoke exposure patterns A subanalysis of the Canadian Human Time-Activity Pattern Survey. Can J Public Health, 90 244-249. 

Measurements of exposure parameters—for example, the indoor air concentrations of chemicals, time-activity patterns and the chemical composition of consumer products—will as a rule be subject to errors inherent in the methodology used, such as errors in the analytical methods used to measure chemical concentrations or inaccuracies in the survey data due to incorrect reporting by the participants. These errors may be categorized as random or systematic (biased) errors ... 

Although there is large inter-individual variation in frequency, duration and amount of product used, consumers tend to follow certain routines [128]. The United States (US) National Human Activity Pattern Survey has been gathering important information for determining exposure to environmental pollutants by collecting data on time-activity patterns for various exposure scenarios [129]. In 2005, a similar project began in the EU that focusses on types of product use according to exposure scenario [130]. 

EXPOSURE FREQUENCY, DURATION AND HUMAN TIME-ACTIVITY PATTERNS... 

Accurate exposure and biological monitoring data are crucial to the evaluation of residential exposure and risk estimates since the potential health risks associated with a pesticide depend on the amount of exposure to the pesticide, its toxicity and the susceptibility of the exposed population. Prediction of whether adverse health effects will occur in humans can be made by comparing the exposure estimate to the No Observed Adverse Effect Level (NOAEL) derived from the animal toxicity data. Uncertainty arises from the input data used in an assessment, e.g. variability in time-activity patterns, contact with exposure media, bioavailability, exposure duration, frequency of product use and differences in the route of exposure in humans from that in the animal studies (since absorption, distribution, metabolism and elimination kinetics may differ substantially by exposure route). 

At the beginning of this paper, an indirect exposure assessment method was described that utilizes microenvironment UFP concentrations and time-activity patterns to assess population exposure. Although this approach is known to underestimate the extreme exposures that may exist within a population, it may... 

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