211095 Potential sources of bias in studies of drinking water exposures

Monday, November 9, 2009: 1:11 PM

Penelope Howards, PhD , Epidemiology Department, Emory University, Atlanta, GA
Although some drinking water contaminates are rare or only present in specific geographic regions, exposure to other impurities, such as disinfection byproducts, is pervasive. As a result, even small effects of such exposures could have important public health implications. However, there are a number of potential sources of bias in studies of water exposures that if unaddressed, could create the appearance of small effects or mask true effects. Information bias due to misclassification of exposure is an area of particular concern because individual level exposure is difficult to assess. In addition, recall bias with respect to the outcome may occur in studies where the participants know that they have been exposed to contaminated water. While differential misclassification of the exposure or the outcome could introduce substantial bias, even non-differential misclassification is important when considering exposures that may have small effects. In addition, residual confounding is of concern in any study, but some water studies may be particularly subject to confounding depending on the study design. When the contaminant of interest is limited to a specific geographic area, a different region may be used to represent the unexposed population. This can result in confounding that cannot be removed analytically if there are risk factors for the outcome that are only present in one location. Therefore, a careful consideration of potential sources of bias is critical when designing studies of water exposures and when interpreting published results.

Learning Objectives:
1) Identify potential sources of bias in studies of drinking water exposures

Keywords: Water, Methodology

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I have a PhD in epidemiolgy from the University of North Carolina. One of my dissertation papers was on methodological issues in a study of spontaneous abortion, and the example used data from a study with a drinking water exposure. I also worked on a research project called Right from the Start, which was designed to evaluate the effect of disinfection byproducts on spontaneous abortion, and I have written an invited commentary on the topic for the American Journal of Epidemiology.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.