Occupational exposure to glycol ethers and human congenital malformations

Abstract

The current evidence is insufficient for one to determine whether occupational exposure to glycol ethers causes human congenital malformations. We suggest that future studies quantify the effect of methodological problems on study results, using methods such as validation studies and sensitivity analysis.

What is the Minimum Risk that can be Estimated from an Epidemiology Study?

“…Summary of potential error factors (EF) due to bias and confounding in three studies of occupational exposure to glycol ethers and congenital malformations. Based on plausible scenarios (Maldonado, Delzell et al 2003) These combined biases are quite large and indicate a MRRR in these studies is far from 1.0. Reproductive studies of this type tend to have large error factors, and the minimal interpretable RRs for these 3 studies should be at least >3, <0.2 and > 3.6 before assessing associations of glycol ether and congenital malformations in these studies.…”

“…As an example of this point, Maldonado et al (2003) conducted sensitivity analyses on four studies investigating relationships between occupational exposures to glycol ether and congenital malformations. They specifically examined methodological errors that produced biased results that could have incorrectly increased RRs from 24% to 300%.…”

“…Unfortunately, "without information that can be used to judge the plausibility of different error-producing scenarios, we cannot know the true impact of error on study results….currently available evidence does not refute the [alternative hypothesis] conjecture that elevated OR estimates are due to error." (Maldonado, et al 2003) Study Example 1: (Cordier, Bergeret et al 1997) This is a case-control study of glycol ether and congenital malformations with multiple positive associations that were substantively modified by adjustments for potential biases. They reported  Overall OR = 1.4 (1.1-1.9) for all malformations combined.…”

“… Potential information bias due to exposure measurement error was inadequately presented so the magnitude of the error factor could not be reliably estimated. Maldonado et al (2003) suggested information bias might produce error factors ranging from 1.4 to 2.3 for exposure misclassification effects related to cleft lip.  Potential biases in combination are estimated by multiplication of the error factors, which in this case was an error factor of 2.47 (= 1.1 x 1.03 x1.09 x 2).…”

“…Cordier et al (1997) adjusted for other biases and estimated an error factor of 1.24 (which changed the crude OR of 2.51 to 2.03). Combining the error factors of Maldonado et al (2003) and Cordier et al (1997) Table 2. Summary of potential error factors (EF) due to bias and confounding in three studies of occupational exposure to glycol ethers and congenital malformations.…”