HR: 0800h
AN: H21C-1027    [Abstracts]
TI: Aquifer Vulnerability to Arsenic contamination in the Conterminous United States: Health Risks and Economic Implications
AU: * Twarakavi, N C
EM: twarak@cc.usu.edu
AF: Utah Water Research Laboratory, 1600 Canyon Road, Logan, UT 84321 United States
AU: Kaluarachchi, J J
EM: jkalu@cc.usu.edu
AF: Utah Water Research Laboratory, 1600 Canyon Road, Logan, UT 84321 United States
AB: Arsenic is historically known be toxic to human health. Drinking water contaminated with unsafe levels of arsenic may cause cancer. The toxicity of arsenic is suggested by a MCLG of zero and a low MCL of 10 ęg/L, that has been a subject of constant scrutiny. The US Environmental Protection Agency (US EPA), based on the recommendations of the National Academy of Sciences revised the MCL from 1974 value of 50 ęg/L to 10 ęg/L. The decision was based on a national-level analysis of arsenic concentration data collected by the National Analysis of Water Quality Assessment (NAWQA). Another factor that makes arsenic in drinking water a major issue is the widespread occurrence and a variety of sources. Arsenic occurs naturally in mineral deposits and is also contributed through anthropogenic sources. A methodology using the ordinal logistic regression (LR) method is proposed to predict the probability of occurrence of arsenic in shallow ground waters of the conterminous United States (CONUS) subject to a set of influencing variables. The analysis considered the maximum contaminant level (MCL) options of 3, 5, 10, 20, and 50 ęg/L as threshold values to estimate the probabilities of arsenic occurrence in ranges defined by a given MCL and a detection limit of 1 ęg/L. The fit between the observed and predicted probability of occurrence was around 83% for all MCL options. The estimated probabilities were used to estimate the median background concentration of arsenic for different aquifer types in the CONUS. The shallow ground water of the western US is more vulnerable to arsenic contamination than the eastern US. Arizona, Utah, Nevada, and California in particular are hotspots for arsenic contamination. The model results were extended for estimating the health risks and costs posed by arsenic occurrence in the ground water of the United States. The risk assessment showed that counties in southern California, Arizona, Florida, Washington States and a few others scattered throughout the CONUS face a high risk from arsenic exposure through untreated ground water consumption. The risk analysis also showed the trade-offs in using different risk estimates as decision-making tools. A simple cost effectiveness analysis was performed to understand the household costs for MCL compliance in using arsenic-contaminated ground water. The results showed that the current MCL of 10 ęg/L is a good compromise based on existing treatment technologies
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting