ABSTRACT
It is not by accident that a chapter on epidemiology has been included in a text on toxicology (Figure 11.1).
An important role of toxicology is to provide a basis from which to infer causation of an association of exposure
to a chemical agent with adverse health outcomes as may be observed in epidemiological studies. The limitations of epidemiological studies include such factors as uncertainty in exposure classi•cation, numerous factors that may confound interpretation, and potential exposures to multiple agents. Although toxicological studies can be carried out in a
Introduction ............................................................................................................................................................................... 527 REACH Guidance on Epidemiology Data ........................................................................................................................... 528 OSHA Guidance on Epidemiology Data ............................................................................................................................. 529 Search for Scienti•c Truth Regarding Human Disease Etiology ......................................................................................... 529 Primary Objective of Chapter .............................................................................................................................................. 530
Measures of Disease Frequency .................................................................................................................................................531 Prevalence and Incidence ......................................................................................................................................................531 Rates ..................................................................................................................................................................................... 532
Measures of Effect and Association .......................................................................................................................................... 533 Absolute Risk ....................................................................................................................................................................... 533 Relative Risk ........................................................................................................................................................................ 533 Standardized Mortality Ratio ............................................................................................................................................... 534 Proportional Mortality Ratio ................................................................................................................................................ 535 Attributable Fraction ............................................................................................................................................................ 535
Methods ..................................................................................................................................................................................... 536 Cohort ................................................................................................................................................................................... 536 Case-Control ........................................................................................................................................................................ 537 Cross-Sectional .................................................................................................................................................................... 539 Ecologic................................................................................................................................................................................ 540 Case Studies or Case Series ................................................................................................................................................. 540
Issues ......................................................................................................................................................................................... 541 Selection ............................................................................................................................................................................... 541 Information Bias................................................................................................................................................................... 543 Sensitivity and Speci•city .................................................................................................................................................... 544 Predictive Value Positive and Predictive Value Negative ..................................................................................................... 545 Confounding ......................................................................................................................................................................... 547 Chance .................................................................................................................................................................................. 548
p Values, Con•dence Intervals, and p-Value Functions .................................................................................................. 549 Exploratory Data Analysis and Multiple Comparisons ................................................................................................... 550
Meta-Analysis .......................................................................................................................................................................551 Causation ...............................................................................................................................................................................551
