BREAKING NEWS: Higher Chemical Exposure
Associated With Lower Occurrence of Diabetes

Steven Hentges, Ph.D
Monday, March 2, 2020 SAFETY
You haven’t seen this actual headline published, but it would be an accurate description ofthe results from a new study sponsored by the U.S. National Institutes of Health. As statedin the conclusion of the study: “Higher concentrations of triclosan, BP-3, and propyl, butyl,ethyl, and methyl parabens were associated with lower odds of diabetes.”
Almost certainly you’ve used consumer products containing these common chemicals. The
conclusion of the study might lead you to believe that you should increase your exposure tothese chemicals in order to reduce your risk of diabetes.
But before jumping to that conclusion, there are two very important words to understand.
What exactly does the term “associated with” mean? It doesn’t mean what you may think itmeans.
The conclusion came from what is known as a cross-sectional epidemiology study. In thisnew study, exposure to the chemicals was determined by measuring chemical
concentration levels in urine samples provided by the study participants. The reason for
urinary measurements is that the chemicals are all short-lived in the body and are quickly
eliminated in urine after exposure. Recent exposure is easily measured by analysis ofurine.
At the same time, health information was collected from the participants; in this caseinformation relevant to diabetes. Studies of this type are described as cross-sectional
because all of the exposure and health data is collected at a single point in time.

1 / 2

Cross-sectional studies are fairly common because the necessary data is often collectedalready for other purposes. In this case, all of the data came from the National Health andNutrition Examination Survey (NHANES), which is an ongoing study conducted by the U.S.
Centers for Disease Control and Prevention (CDC). The survey collects a wide range ofdata that is aimed at assessing the health and nutritional status of adults and children in theU.S.
The data were analyzed to determine if there are any statistical associations between
chemical exposures and diabetes. Indeed, the analysis revealed that higher exposurelevels were statistically associated with lower occurrence of diabetes. The term “associatedwith” simply refers to these statistical associations.
But as noted by the study authors, “our study can only demonstrate [statistical] associations
and not prove causality.” This is intuitively understandable because “diabetes develops overthe course of many years.”
In comparison, because of the short half-lives of these chemicals in the body, the measured
urinary concentrations only reflect short-term exposure. As a result, the authors note that
“we therefore cannot …rule out that diabetes diagnosis occurred before the paraben/phenolexposure.”
Numerous similar cross-sectional studies have been conducted on bisphenol A (BPA) using
NHANES data or other readily available datasets. The researchers involved with this new
study also examined BPA, but determined there were no statistical associations between
BPA levels and higher or lower occurrence of diabetes.
Regardless of whether statistical associations were found, the authors stress that “causalinterpretation of our findings is not possible given the cross-sectional nature ofNHANES.” Additional research would be needed to determine if the statistical associations
have any clinical significance.
Although this particular study has not received media attention, the results of crosssectional studies are frequently highlighted in the news with sensational headlines such as
the one noted above. The results may sound important, but the casual reader should
always be aware of the limitations of cross-sectional studies. Statistical associations are
just that – statistics.
2 / 2