# Presentation: 420337

## Volatile Organic Compounds in the Nation’s Ground Water and Drinking-Water Supply Wells

**by **
**John S. Zogorski**

**U.S. Department of the Interior**
**U.S. Geological Survey**
**National Water-Quality Assessment (NAWQA) Program**

**The Quality of Our Nation’s Waters**

## Products containing VOCs have many uses  in industry, commerce and households

**Products containing VOCs have many uses **** in industry, commerce and households**

- slide 2

**Engine fueling**

**Automotive painting**

## Purpose of assessment

**To characterize the occurrence and distribution of VOCs in ambient ground water and drinking-water supply wells across the Nation**

**slide 3**

**Notes:**
55 VOCs were selected for assessment:
 Presence in ground water
 large production and use
 persistence in ground water
Toxicity to human health
 potential for large-scale use

## Scope of assessment

**55 VOCs were selected **
**for assessment**

**This assessment represents **
** ****an evaluation of VOC data collected or compiled during NAWQA’s first decade**

**slide 4**

**Notes:**
55 VOCs were selected for assessment:
 Presence in ground water
 large production and use
 persistence in ground water
Toxicity to human health
 potential for large-scale use

## Water-supply system

***Treatment***

**slide 5**

**Ambient **
**ground **
**water**

**Drinking **
**water**

## No VOC Detection

**Hawaii**

**Oahu**

**Alaska**

**No VOC Detection**

**VOC Detection**

**Notes:**
Findings: VOCs were detected in aquifers throughout the Nation.

Conclusions: Many of the Nation’s aquifers are vulnerable to VOC contamination.

## VOC concentrations in aquifers

**Not **
**detected**

**       ****Detected, **
**below 1 ppb**

**slide 7**

**    ****Detected, **
**above 1 ppb**

**Notes:**
Finding: Most aquifer samples had no VOCs detected or the concentration was below 1 part-per-billion (ppb)

Conclusion: Few aquifer samples have VOC concentrations that may affect the potability of ground water for drinking water

## Chloroform was the most frequently detected VOC in aquifer samples

**slide 8**

**DETECTION FREQUENCY, IN PERCENT**

**Toluene**

**TCE**

**PCE**

**Chloroform**

**MTBE**

**Notes:**
Assessment level of 0.2 micrograms per liter

Conclusion: Recycled water with a history of chlorination is an important source of chloroform (and other THMs) for aquifers.

## TCE

**slide 9**

**DETECTION FREQUENCY, IN PERCENT**

**Toluene**

**TCE**

**PCE**

**Chloroform**

**MTBE**

## MTBE

**slide 10**

**DETECTION FREQUENCY, IN PERCENT**

**Toluene**

**TCE**

**PCE**

**Chloroform**

**MTBE**

## Domestic wells

**Domestic wells**

**slide 11**

**Public wells**

**and**

## Public

**Public**
** ****wells**

**Domestic**
**       ****wells**

**DETECTION FREQUENCY, IN PERCENT**

**concentrations below MCLs and HBSLs**

**concentrations greater than MCLs**

**Slide 12**

## VOCs with concentrations greater than MCLs

**slide 13**

**DBCP****	****	****	****	****X**
**1,2-Dichloropropane****	****X****	****	**
**EDB****	****	****	****	****X****	****	****	****	**

**1,1-Dichloroethene****	****X****	****	****X****	****    ****	****	**
**Vinyl chloride****	****	****	****	****X**

**TCE****	****	****	****	****X****	****	****X**
**PCE****	****	****	****	****X****	****	****X**
**Methylene chloride****	****	****	****X**

**Domestic**

**Compound**

**Public**

**Well type**

**Fumigants**

**                            ****Chemical**
**production**

**Solvents**

**Group**

**Notes:**
VOCs found at concentration(s) of potential human-health concern (compounds listed by decreasing number of concentrations of potential concern).

Finding: Only 8 compounds had concentrations of potential human-health concern.

Conclusion: Most VOC concentrations are not anticipated to cause adverse human-health effects.

## Summary comments

**Widespread occurrence of VOCs**
**Concentrations seldom of **
**      ****potential concern**
**Large number of vulnerable ****	****aquifers**

**slide 14**

## Additional ongoing activities

**Water quality of domestic wells**
**Source water of large**
**     ****community water systems**
**Movement of contaminants to **
**     ****public wells**
**Trends of gasoline oxygenates**

**slide 15**