That’s Cool! I Get My Water From the Sink Though…<br />About ½ of the U.S. population gets its drinking water from groundwater sources, including almost entire population of rural areas.<br />USGS estimates domestic wells provide water to about 43.5 million people representing 15% of the total U.S. population.<br /><ul><li>Estimated withdrawals from domestic wells increased by 60% between 1965 and 2000.
Estimates by the National Groundwater Association indicate that more than 400,000 new wells are drilled every year to provide people with drinking water in the United States.</li></li></ul><li>Volatile Organic Compounds Oh My!<br />Organic chemicals with high vapor pressure.<br />The higher the vapor pressure, the greater then tendency of the compound to shift from liquid (or solid) to gaseous form.<br />The chemicals and properties allow VOCs to move easily between atmosphere, soil, surface water, and groundwater.<br />Once in the environment, VOCs can be mobilized, dispersed, diluted, volatilized, absorbed and/or degraded<br />Lifespan of VOCs is highly variable-ranging from relatively short.<br />Production of some synthetic organic chemicals (many of which are VOCs) has increased more than an order of magnitude between 1945 and 1985.<br />Once introduced into groundwater VOCs my persist and contaminate drinking water supplies.<br />Some VOCs are carcinogens and/or may adversely affect the liver, kidneys, and stomach, as well as the nervous circulatory, reproductive, immune, cardiovascular, and respiratory systems. Some VOCs affect cognitive abilities, balance, and coordination, and some are eye, skin, and throat irritants.<br />
Assessment of VOCs<br />According to EPA reports, a high presence of VOCs in drinking water may be a human-health concern.<br />USGS National Water-Quality Assessment Program recently completed an assessment of 55 VOCs in groundwater throughout the United States.<br />Screening Level Assessments were conducted on 2,401 samples from domestic wells and compared with human-health benchmarks when available, including US EPA MCLs for regulated contaminants, as well as health-based screening levels for unregulated contaminants. <br />HBSLs as well as MCLs, are maximum concentrations of contaminants that are not expected to cause adverse health effects over a lifetime of exposure.<br />Purpose of Screening Level Assessments is to assess the need, if required, the level of effort necessary to conduct a detailed or baseline ecological risk assessment at a particular site.<br />Health-based Screening Levels –HBSLs-Not enforceable drinking water standards or clean-up levels.<br />
Methods<br />VOC YOU!<br />VOCs were selected based on many criteria, including:<br /><ul><li> Potential human-health cancer risks
Trihalomethanes</li></li></ul><li>Equipment Used<br />For VOCing<br /><ul><li> Samples were analyzed using purge and trap gas chromatography/mass spectrometry</li></ul>Tekmar Velocity Concentrator<br />Tekmar 3000 Concentrator<br />Agilent 6890 GC<br />(Confused kittens were not harmed in this process)<br />Agilent 5973 MSD<br />
Analysis<br /><ul><li> Non-parametric statistical tests were used to analyze occurrence data
Multivariate logistic regression analyses were used to determine relations between probability of VOC occurrence relative to hydrogeologic and anthropogenic variables.</li></li></ul><li>Results<br />VOC-ML<br /><ul><li> Of the 55 VOCs that were tested for, 42 were detected.
One or more VOCs were detected in 65% of the samples.
As many as 24 VOCs were detected in one sample.
VOCs were detected all throughout the contiguous United States and also Alaska.
Of the well samples, 31% contained only one VOC and 34% contained mixtures of two or more VOCs.
The VOCs of highest health concern often occurred together in mixtures in samples (23 out of 32).
Samples with VOC concentrations greater than their MCLs often occurred in highly populated areas.
VOC concentrations were higher in wells with a closer proximity to Resource Conservation and Recovery Act sites.
Seven VOCs that do not have established MCLs or HBSLs were detected in samples.
Concentrations of six VOCs in 1.2% of the samples were of potential human-health concern because their concentrations were greater than MCLs.</li></li></ul><li>Discussion<br />We’re VOCed<br /><ul><li> A new, more effective low level analysis method was developed in 1996.
As analytical reporting levels decreased, detection frequency of VOCs increases.
Previous research has focused on individual chemicals rather than mixtures.