| Many factors within a water system can influence drinking water quality. One example is the presence of cyanobacteria, which can naturally occur in surface water sources of drinking water and produce toxins associated with harmful algal blooms. Another example is the deterioration of drinking water distribution systems, which can lead to pipe breaks. This study assessed how such factors within a large drinking water system serving metropolitan Boston communities may influence human health.;In Aim 1, Poisson regression models were used to estimate the associations between daily measures of cyanobacteria concentration in the water source and emergency department (ED) visits for acute gastrointestinal illness (AGI), respiratory illness, and dermal illness over a 7-year period (7/27/2005 -- 9/30/2012). Considering both 2--4 and 5--7 day lag periods, small relative increases in daily ED visits were observed for AGI and respiratory illness when comparing upper quartile levels of cyanobacteria concentrations with the lowest quartile (≤5.0 Areal Standard Units/mL).;In Aim 2, case-crossover methods were used to examine the associations between water pipe breaks and ED visits for AGI. The first part (Aim 2a) examined 385 water main breaks in the City of Boston over a 10-year period (10/1/2002 -- 9/30/2012). The second part (Aim 2b) examined a major water pipe break in 2010 that resulted in a boil water order affecting 30 metropolitan Boston communities. Conditional fixed-effects logistic regression models estimated the risk of ED visits for AGI during 0--3 and 4--7 day hazard periods. When restricted to zip codes served primarily by a single water service network, the association between main breaks and ED visits for AGI was slightly elevated during the 0--3 days after a break (OR=1.15; 95% CI: 0.99-1.34). Furthermore, there was an increased risk of ED visits for AGI during the 0-3 days after the major water pipe break in 2010 (OR=1.32; 95% CI: 1.07-1.61), particularly among children (≤5 years) and adolescents (6-18 years).;This dissertation identified potential health risks related to cyanobacteria in the water source and water pipe breaks in the distribution system. These associations are important to consider given the consequences of a changing climate and aging infrastructure. |
