What is the role of epidemiological studies in human risk assessment and what limitations do they have?

• A. Epidemiology links exposures to health outcomes in humans; limitations include confounding, bias, exposure misclassification, and limitations in establishing causality.
• B. Epidemiology provides direct proof of causation without uncertainty.
• C. Epidemiology is not used in risk assessment.
• D. Epidemiology studies are always experimental.

Answer: (A)

Epidemiology provides human data by studying associations between exposures and health outcomes in populations, which is essential for risk assessment because it shows how a substance affects people under real-world conditions. It helps identify potential hazards, characterize patterns of risk, and inform dose–response and exposure assessments in humans. However, this approach has limitations. Confounding occurs when an extra factor is linked to both the exposure and the outcome, potentially creating or exaggerating an association. Bias can creep in through study design or data collection, such as selection bias or recall bias, which can skew results. Exposure misclassification happens when the level or timing of exposure is measured inaccurately, reducing the study’s ability to detect true relationships. Importantly, most epidemiological studies are observational and cannot by themselves prove causality; random assignment is not used, so alternative explanations must be ruled out. Causality is typically inferred through consistency across studies, temporal sequence, strength and dose–response of associations, biological plausibility, and triangulation with other evidence. Despite these limitations, epidemiology remains indispensable for informing human risk assessment, especially when paired with mechanistic data and results from other study designs to build a weight-of-evidence picture.