Drinking Water Contamination With 1,4-dioxane on Long Island

Environmental Risk Assessment 656. Homework #1 (of 3). Due 2/16/22.
View the PBS news segment on drinking water contamination with 1,4-dioxane on Long Island. Kociba (1974) is an important study in the body of literature on the toxicity of 1,4-dioxane. The study is described in a fairly clear, straightforward manner. Please read the study critically and answer the following questions. For background only, I am also providing a copy of Argus (1973), which is referenced in Kociba (1974). Include any thoughtful questions about parts of the study that are not clear to you. We can also discuss any clarifications you need when in class on 2/9/22. Your answers will be due by 2/16/22.
The goal of the homework in this course is to go beyond facts and basic concepts and reach for some of the higher levels of “Bloom’s Taxonomy”: “apply,” “analyze,” and “evaluate.”
1 PURPOSE/RATIONALE
Why was this study done? What were the questions the investigators were trying to answer?
Since 1,4-dioxane is highly soluble, it is hard to treat water to remove it. Its properties also make it hard to detect because it is colorless. Furthermore, it can be present in drinking water in very small (though significant) amounts, which makes it even harder to detect via conventional methods (i.e. if you are not looking for it, you cannot find it immediately). Because of this, the EPA has declared 1,4-dioxane to be a potential cause of cancer (Weber & Fong, 2017). Ongoing research are present for looking for possible chemicals such as the 1,4-dioxane that may contaminate drinking water. Essentially, Kociba et al.’s study was done to assess the toxicity of 1,4-dioxane, to settle ongoing debates on whether or not it poses a significant risk to consumers. Specifically, the authors aimed to identify the levels at which 1,4-dioxane becomes toxic to rats before moving on to or supporting research assessing the same on humans.
2 METHODOLOGY
a. What type of study was this? Briefly describe the basic study design (agent(s); types and numbers of animals; route, frequency and length of dosing; and toxicological endpoints studied).
The study by Kociba et al. (1974) was an experimental study involving 60 male and 60 female rats as subjects (per treatment level), with varying treatment levels of 1,4-dioxane introduced through the rats’ drinking water. The experimental treatment levels were 1.0%, 0.1%, and 0.01% 1,4-dioxane in drinking water, while the control group received 0% of 1,4-dioxane in their drinking water. The rats were subjected to their respective assigned treatments for up to 716 days.
b. What were the doses of 1,4-dioxane used in the study, expressed as 1) concentration in water
(volume/volume), and as 2) daily dose of 1,4-dioxane mg/kg/day?
1 1%= 1mL/100mL solution ; 0.1%= 0.1mL/100mL solution ; 0.01%= 0.01mL/100mL solution
2 1%= 1015 mg/kg/day for males ; 1599 mg/kg/day for females
0.1%= 94 mg/kg/day for males ; 148 mg/kg/day for females
0.01%= 9.6 mg/kg/day for males ; 19 mg/kg/day for females
c. Was the dosing (route, magnitude, frequency, duration) appropriate to the purpose of the study? Why or why not?
Yes, it was appropriate because the ...