The PECO Framework
The cornerstone of systematic reviews in environmental health and toxicology
Anatomy of a Research Question
PECO is a specialised framework designed to translate broad scientific uncertainties into structured, answerable questions. Unlike PICO (Population, Intervention, Comparator, Outcome) used in clinical medicine, PECO replaces ‘Intervention’ with Exposure to reflect environmental and occupational realities.
Population
Specific human groups, sensitive life stages (e.g. prenatal), or ecological species.
Exposure
Chemical agents, physical stressors (noise, radiation), or social determinants.
Comparator
Control groups with no exposure, or background/reference levels.
Outcome
Health effects, clinical diagnoses, biomarkers, or adverse outcome pathways.
Why PECO is Essential
Protocol Development
PECO defines the inclusion/exclusion criteria before the review starts, reducing bias.
Systematic Search
Keywords derived from each component ensure a sensitive and specific search strategy.
Synthesising Evidence
PECO provides a logical structure for grouping heterogeneous studies for meta-analysis.
Transparency
Stakeholders can clearly see exactly what the review is (and isn’t) addressing.
Implementation Examples
Select a research domain to see how PECO translates to real-world review statements.
Select an example above
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Visualising Evidence
PECO allows researchers to perform “Evidence Mapping”—identifying which health outcomes have the most robust literature versus research gaps.
Interactive Annotation Challenge
Practise identifying PECO components. Select a “Brush” and click on the corresponding text segments. Elements may appear in any order!