Table 2. Checklist for Exposure Assessment Protocols in Environmental Epidemiology Studies.

From: Advancing systematic-review methodology in exposure science for environmental health decision making

Study component	Critical questions
Study hypothesis	•What is the time and/or duration of the exposure being assessed? •Is the exposure assessment time frame consistent with the biologically relevant time frame of the outcome? •What is the specific hypothesis/objective of the study?
Study population	•Are the population characteristics reported (e.g., age, gender, race, and health status)? •How was the population recruited, selected, and followed? •How representative is the sample population compared with the general population? •Could recruitment strategies, eligibility criteria, or participation rates be differential with respect to exposure or outcome?
Exposure assessment approach	•Is the exposure assessment prospective or retrospective? •Were direct or indirect exposure assessment approaches employed? •Were environmental measurements used? •Were biomarkers of exposure used? •Were exposure models used?
Environmental measurements	•What specific stressors were measured? •Were all environments represented in the sampling protocol? •Were all media in which the stressors exist sampled or accounted for? •Were all potential routes of exposure considered? •What methods were used to collect and analyze samples? •How frequently were samples collected and analyzed? •What is the sensitivity, accuracy, and precision of the method used? •Is the time frame of the measurement consistent with the biologically relevant time frame of the outcome under study? •Was the spatial and temporal variability of the stressor assessed?
Questionnaire tools	•How were the questionnaires administered (e.g., in person, via phone, mail, and online)? •Were standardized questionnaires from other sources used? •Was historical data collected and if so from what source? •Did questionnaires account for varying sources, routes, and media of exposure? •Did questionnaires cover all relevant variables in both space and time? •Were the questionnaires validated? •Would knowledge of outcome be likely to influence reporting about exposures?
Biomarkers of exposure	•What biomarkers of exposure were measured? •Is the relation between exposure and biomarker concentration known and consistent with the outcome under study? •What is the sensitivity, accuracy, and precision of the method used? •When were the samples collected and analyzed and is the uncertainty known? •Were methods validated? •What is the intraindividual variability of the measurement? •Could the biomarker measurement have been affected by the outcome (i.e., reverse causality)?
Exposure models	•Were mechanistic models of chemical, physical, or biological processes used to assess exposure? •Were statistical models used to assess exposure? •Do the models capture space and time of exposure? •Are the models validated? •Is the associated uncertainty discussed? •Are the models applicable to other populations and locations?
Data analysis and reporting	•Does the exposure metric capture variability in exposures across the population in relation to frequency, duration, and intensity? •Are the exposures represented appropriately as continuous or categorical variables? •If categorical variables are used how are they justified? •How are zeros or measurements below the detection limit used? •Do exposures match the time frame of the outcome and is the time frame biologically relevant? •Are relevant covariates considered (e.g., confounders and modifiers)? •Are the strengths and weaknesses of the exposure approach detailed and discussed?