Table 1.

Comparison between a population survey and a microenvironmental measurement campaign.

	Population survey	Microenvironmental measurement study
Unit of observation	Individual	microenvironment*
Requirement for the study sample	representative for the population of interest	representative in terms of exposure-relevant behaviours for the population of interest
Selection of participants	random and representative sample needed	convenient sample is sufficient oversampling of rare exposure-relevant behaviours
Motivation of participants	part of the random sample will not be motivated	convenient sample is more motivated on average
diary	basic and simple, if any at all	compulsory
Measurement duration	as long as reasonable for the participants	not crucial
Sample size	many individuals	many measurements from numerous microenvironments of the same type

* For the purpose of estimating exposure, a microenvironment is considered a spatial compartment where an individual spends time and exposure can be characterized during that time.