Evaluation of Cancer from Exposure to Cyanotoxins in Drinking Water at Grand Lake Saint Marys

Background: The Celina Water Department treats and supplies surface water contaminated by cyanotoxins from Grand Lake Saint Marys (GLSM) to approximately 12,000 customers in Celina, Ohio. Cyanotoxins are a biochemically and bioactively diverse group of extremely potent natural toxins in water. A common cyanotoxin called microcystin-LR found in GLSM has been associated with acute liver damage and potentially liver and colorectal cancer. Methods: In this observational study, the city of Celina (Mercer County) Ohio that had a contaminated surface water supply, the cancer incidence was compared with two control cities, St. Marys, and Wapakoneta (Auglaize County) in Ohio, both served by ground water. Cases were identified through the Ohio Cancer Incidence Surveillance System (OCISS) registry from1996-2008. Cumulative age adjusted incidence rates (IRs) for hepatocellular carcinoma (HCC) and colorectal cancer (CRC) were calculated. The cumulative IR, and 95% confidence interval (95% CI) of CRC and HCC were also compared with the IR in Ohio and the Surveillance, Epidemiology and End Results database. Results: Celina had the lowest cumulative IR of HCC 2.4/100,000 compared to Wapakoneta 5.3/100,000 and Saint Marys 4.0/100,000 people. The IR for HCC was not significantly different than the Ohio or SEER rates (P> 0.05). CRC rates in Celina were 78.4/100,000 which was lower than Wapakoneta 82.9/100,000. However, the CRC IR and 95% CI were significantly higher (P< 0.05) for all 3 cities when compared to either Ohio or national SEER rates. Conclusion: There is inconclusive evidence to support that cyanotoxins from GLSM are associated with excess risk of cancer from drinking water. 2 EVALUATION OF CANCER FROM EXPOSURE TO CYANOTOXINS Introduction Surface water (SW) is often used for drinking water supplies. The water quality varies widely depending upon many environmental and anthropogenic factors. Toxic cyanobacteria or blue-green algae are often part of the normal phytoplankton population in surface waters. These cyanobacteria show incredible morphological diversity (Pearson, Mihali, Moffitt, Kellmann, & Neilan, 2010). In relatively clean water with limited nutrients (oligotrophic), the distribution of cyanobacteria is relatively low (Falconer, 2005). When water becomes polluted (eutrophic) from nutrient enrichment, cyanobacteria populations can proliferate exuberantly and often a single or a few species predominate (Falconer, 2005). Like algae, cyanobacteria are photosynthetic but the individual cells lack an organized nucleus and do not contain chloroplasts thus making them more like bacteria. Individual organisms are too small to be seen with the naked eye, however, in eutrophic conditions the cyanobacteria can form algal blooms which can often be seen on the surface of water. The blooms may be several inches thick, particularly near the shoreline or may be suspended in the water column at various depths. The underlying reasons that promote these blooms are not completely understood, but it is thought that it may be related to nutrients added naturally and through man-made sources such as fertilizer runoff (Carmichael & Falconer, 1993; Rapala, Sivonen, Lyra, & Niemela, 1997). According to Falconer (2005), one factor that may contribute to dominance of a single species of cyanobacteria is the ability to produce toxins. The production of natural toxins by a particular strain of cyanobacteria may be a form of natural selection through suppressing consumption by other organisms. Cyanotoxins can either be water soluble or lipid-soluble. There are currently about 40 known species of cyanobacteria capable of producing toxins, however, at 3 EVALUATION OF CANCER FROM EXPOSURE TO CYANOTOXINS any particular time, cyanobacteria may or may not be producing toxin (Westrick, Szlag, Southwell, & Sinclair, 2010). By comparison, according to a literature review in 1994, only 12 different species of cyanobacteria had been shown to produce toxins (Carmichael, 1994). Water-soluble cyanotoxins are of particular concern to drinking water because they can pass through a conventional water treatment plant utilizing coagulation, flocculation, sedimentation and filtration processes (Falconer, 2005). Certain cyanotoxins are resistant to boiling and chemical disinfection, so they could be present in the distribution system and ultimately at the consumer’s tap water if proper treatment strategies are not employed. Typically, public water systems do not monitor or treat for cyanotoxins either in source or finished water because cyanotoxins are not regulated in the United States (U.S.) under any National Primary Drinking Water Regulation (NPDWR). According to the Ohio Environmental Protection Agency (OEPA), GLSM covers approximately 13,500 acres. It is roughly 9 miles long, 3 miles wide and average about 7 feet deep with a soft bottom of silt. GLSM was constructed around 1850 as part of the Miami-Erie Canal and was at one time the world’s largest man-made lake before Lake Mead was formed as a result of construction of the Hoover Dam in 1935. GLSM is enriched with phosphorous as a result of runoff from years of fertilizer and manure application to fields. This has decreased the water quality by increasing turbidity, decreasing dissolved oxygen and increasing concentrations of nitrogen and phosphorous. According to the OEPA, approximately 90% of the land in the GLSM watershed is utilized for crop and livestock production. The Ohio Department of Natural Resources (ODNR) estimated that currently between 150,000 and 200,000 tons of phosphorous-laden silt enters GLSM every year.