Exploring the Link between Low-Rank Coal Derived Organic Compounds in the Carrizo-Wilcox Aquifer and Incidence of Kidney Disease in East Texas

Low-rank coal contains a myriad of organic compounds but little is known about the impact of these toxic compounds on human health when they are mobilized into groundwater and consumed. Ingestion of coal-tainted water has been previously linked to widespread kidney disease and urinary tract cancers including idiopathic Balkan Endemic Nephropathy (BEN). One example of a low-rank coal-bearing aquifer is the Carrizo-Wilcox, which provides groundwater supply to nearly sixty counties in rural east Texas. Five coal samples collected from active mines along the aquifer trend were also analyzed for structural and functional characteristics at the molecular level through Soxhlet leaching experiments. Forty-eight groundwater samples from rural public drinking water supplies along the aquifer trend were collected from nine rural counties and analyzed for the presence of organic compounds. The purpose is to determine whether there exists any similarity between the suites of compounds identified in the water wells to the compounds leached out from coal samples in the laboratory leaching experiments. The coal samples exhibited the presence of nitrogen, sulphur and oxygen (NSO) heterocyclic compounds along with the presence of phenols and benzene derivatives. Most well water samples also revealed the presence of similar suite of compounds with an estimated concentration ranging from 0.1 to 3.9 μg/L. Geostatistical analysis using kriging interpolation technique revealed spatial variation in the nature and concentration of coal-derived organics along the aquifer trend. The percentage of aliphatic compounds were higher in water wells located in the northern and southern parts of the regional aquifer compared to higher percentage of aromatics in the central part of the aquifer. The concentration of aliphatic compounds was higher in the wells located in the eastern and central parts of the aquifer. This geospatial variation along the aquifer trend can be attributed to the presence of fewer and thinner lignite seams in the southern part of the aquifer, thick coal beds in the eastern part of the aquifer and higher rank subbituminous coal in the central area. Non-parametric test for multiple groups (Kruskal-Wallis) coupled with post hoc t-test (Conover-Iman) indicated that there exists a significant statistical difference between the concentration of organic compounds detected in the wells intersected by coal either in boring hole or screened interval and the wells devoid of coal. Spearman correlation showed a significant (p < 0.05) to highly significant (p < 0.01) correlation exists between the incidence rates of kidney disease (end stage renal disease and kidney cancer) and the concentration of both aliphatic and aromatic compounds. In addition, an increase in concentration of the organic compounds (proposed threshold limit above 0.1 μg/L) showed an increase in the incidence rates of kidney diseases.