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Cyanobacteria in a drinking water source and human health
Citation:
Lin, C., E. Hilborn, D. Richardson, AND T. Wade. Cyanobacteria in a drinking water source and human health. UNC Water Microbiology Conference, Chapel Hill, North Carolina, May 14 - 16, 2019.
Impact/Purpose:
We observed an association between low levels of cyanobacteria in the drinking water source and emergency department visits for acute symptoms of gastrointestinal, respiratory, and dermal illnesses. The health effects of cyanobacteria at low levels in drinking water sources should be further examined.
Description:
KEY LEARNING OBJECTIVES: - We observed an association between low levels of cyanobacteria in the drinking water source and emergency department visits for acute symptoms of gastrointestinal, respiratory, and dermal illnesses. - The health effects of cyanobacteria at low levels in drinking water sources should be further examined. ABSTRACT: Drinking water systems that use surface water sources are susceptible to cyanobacterial blooms which can produce cyanotoxins. Drinking water exposure to cyanotoxins have been associated with a range of acute symptoms of illness (e.g., gastroenteritis, muscle pain, dermatitis). Even in the absence of a bloom, cyanotoxins can be present and pose a health threat. While exposures to high levels of cyanotoxin have been linked to disease outbreaks, the effect of chronic low levels is not well-documented or understood. The Massachusetts Water Resources Authority (MWRA) uses an unfiltered treatment process to provide drinking water from the Wachusett Reservoir to metropolitan Boston communities. Our study objective was to estimate the association between measured cyanobacteria levels in the Wachusett Reservoir and the rate of emergency department (ED) visits for acute gastrointestinal (GI), respiratory, and dermal symptoms of illness. We included 22 metropolitan Boston communities receiving MWRA water services over a 7-year period (July 27, 2005 – September 30, 2012). Daily cyanobacteria levels were estimated based on measurements in water samples collected from the Wachusett Reservoir. Acute GI, respiratory, and dermal symptoms of illness were defined using ED visit diagnosis codes. Poisson regression models using a 2-4 day lag period estimated incidence rate ratios (IRR) to describe the relative rate of ED visits by quartile of cyanobacteria concentration. During the study period, there were 60,826 visits for GI illness, 48,802 for respiratory, and 1,161 for dermal. Total cyanobacteria levels in the Wachusett Reservoir ranged from 0 - 532.5 Areal Standard Units (ASU)/mL. Compared to the lowest quartile of total cyanobacteria (≤5.0 ASU/mL), the rate of ED visits for respiratory illness increased by 6% (IRR=1.06; 95% CI: 1.02-1.11) in the highest quartile (≥80.2 ASU/mL) and 7% (IRR=1.07; 95% CI: 1.04-1.11) in the second highest quartile (24.4-80.2 ASU/mL). For GI illness, the rate of ED visits increased by 6% (IRR=1.06; 95% CI: 1.03-1.10) in the highest quartile and 5% in the second highest quartile during the 2-4 day lag period. For dermal symptoms, the second lowest quartile (5.0-24.4 ASU/mL) was associated with a 21% increase (IRR=1.21; 95% CI: 1.01-1.46); however, there was no association in the higher quartiles. In stratified analyses, the younger (≤18 years) and older (≥65 years) age groups appeared to be more strongly affected by cyanobacteria for certain outcomes. Due to generally low baseline rates of ED visits for the outcomes of interest, the absolute increases in daily ED visits due to cyanobacteria was minimal. This abstract does not reflect EPA policy.