Risk Is Negligible in Contaminated Water

Risk is negligible in contaminated water

Present plans for dealing with groundwater contaminated with 1,4-di-oxane from the Gelman Sciences site call for a combination of treatment and the discharge of water containing up to 100 parts per billion to the Allen Storm Sewer. One of the concerns with that discharge is the potential risk.

Basically, any potential risk is a product of the exposure and the toxicity of a substance. 1,4-Dioxane is not a particularly potent compound with respect to its toxicity. The major issue of concern is that it has been shown to increase the incidence of cancers in the liver and the nose in laboratory mice and rats, when they consume drinking water containing 0.5 to 1 percent of 1,4-dioxane for their entire life. The total number of tumors found at all sites in these studies was similar to that found in unexposed animals. There is no evidence that 1,4-dioxane is a carcinogen in humans, and permissible occupational exposures can result in the inhalation of up to 900 milligrams of 1,4-dioxane per day. In contrast, at 100 parts per billion one liter of water would contain 0.1 milligram of 1,4-dioxane.

Risk assessments for drinking water depend heavily upon a series of conservative assumptions, and the acceptable levels that have been suggested for drinking water range from 2 parts per billion to 3 parts per million, depending upon the specific assumptions that are selected. In all cases, a risk assessment applicable to drinking water assumes a daily consumption of 2 liters for 72 years.

The water in the Allen Storm Sewer is not meant to be consumed. If it were to be accidentally consumed, then my major concern would be focused on the potential risks posed by bacterial and viral pathogens. The absorption of 1,4-dioxane through the skin is slow, and as an aside, much more 1,4-dioxane would be absorbed during the use of shampoos and cosmetics in which 1,4-dioxane is a common impurity. In my opinion, the risks attributable to 100 parts per billion of 1,4-dioxane in a storm drain are negligible and most likely non-existent.

Rolf Hartung
Ann Arbor