Gunther F. Craun

Drinking Water Source and Chlorination Byproducts I. Risk of Bladder Cancer

We conducted a population-based case-control study of bladder cancer in Iowa in 1986–1989 to evaluate the risk posed by tapwater containing chlorination byproducts. We combined information about residential history, drinking water source, beverage intake, and other factors with historical data from water utilities and measured contaminant levels to create indices of past exposure to chlorination byproducts. The study comprised 1,123 cases and 1,983 controls who had data relating to at least 70% of their lifetime drinking water source. After we adjusted for potential confounders, we calculated odds ratios for duration of chlorinated surface water of 1.0 (referent), 1.0, 1.1, 1.2, and 1.5 for 0, 1–19, 20–39, 40–59, and ≥60 years of use. We also found associations with total and average lifetime byproduct intake, as represented by trihalomethane estimates. Positive findings were restricted to men and to ever-smokers. Among men, odds ratios were 1.0 (referent), 1.1, 1.3, 1.5, and 1.9, and among ever-smokers, 1.0, 1.1, 1.3, 1.8, and 2.2, after adjustment for intensity and timing of smoking. Among nonsmoking men and women, regardless of smoking habit, there was no association. Among men, smoking and exposure to chlorinated surface water mutually enhanced the risk of bladder cancer. The overall association of bladder cancer risk with duration of chlorinated surface water use that we found is consistent with the findings of other investigations, but the differences in risk between men and women, and between smokers and nonsmokers, have not been widely observed.

Causes of Outbreaks Associated with Drinking Water in the United States from 1971 to 2006

SUMMARY Since 1971, the CDC, EPA, and Council of State and Territorial Epidemiologists (CSTE) have maintained the collaborative national Waterborne Disease and Outbreak Surveillance System (WBDOSS) to document waterborne disease outbreaks (WBDOs) reported by local, state, and territorial health departments. WBDOs were recently reclassified to better characterize water system deficiencies and risk factors; data were analyzed for trends in outbreak occurrence, etiologies, and deficiencies during 1971 to 2006. A total of 833 WBDOs, 577,991 cases of illness, and 106 deaths were reported during 1971 to 2006. Trends of public health significance include (i) a decrease in the number of reported outbreaks over time and in the annual proportion of outbreaks reported in public water systems, (ii) an increase in the annual proportion of outbreaks reported in individual water systems and in the proportion of outbreaks associated with premise plumbing deficiencies in public water systems, (iii) no change in the annual proportion of outbreaks associated with distribution system deficiencies or the use of untreated and improperly treated groundwater in public water systems, and (iv) the increasing importance of Legionella since its inclusion in WBDOSS in 2001. Data from WBDOSS have helped inform public health and regulatory responses. Additional resources for waterborne disease surveillance and outbreak detection are essential to improve our ability to monitor, detect, and prevent waterborne disease in the United States.

Outbreaks associated with recreational water in the United States.

In this article, we review the causes of outbreaks associated with recreational water during 1971 – 2000. A bacterial or protozoan etiology was identified in three-quarters of the outbreaks; 23% of the outbreaks were of undetermined etiology. The most frequently identified agents were Cryptosporidium (15%), Pseudomonas (14%), Shigella (13%), Naegleria (11%), Giardia (6%), and toxigenic E. coli (6%). Outbreaks attributed to Shigella, E. coli O157:H7, and Naegleria were primarily associated with swimming in fresh waters such as lakes, ponds, and rivers. In contrast, outbreaks caused by Cryptosporidium and Giardia were primarily associated with treated water in swimming and wading pools. Important sources of contamination for both treated and untreated recreational waters were the bathers themselves. Contamination from sewage discharges and wild or domestic animals were also important sources for untreated waters. Contributing factors in swimming-pool outbreaks were inadequate attention to maintenance, operation, disinfection, and filtration. Although not all waterborne outbreaks are recognized nor reported, the national surveillance of these outbreaks has helped identify important sources of contamination of recreational waters and the etiologic agents. This information can affect prevention recommendations and research priorities that may lead to improved water quality guidelines.

Drinking water source and chlorination byproducts. II. Risk of colon and rectal cancers

We evaluated the association between chlorination byproducts and colon and rectal cancer risk in a population-based case-control study conducted in Iowa in 1986–1989. Data were gathered from 685 colon cancer cases, 655 rectal cancer cases, and 2,434 controls. We calculated odds ratios for the 560 colon cancer cases, 537 rectal cancer cases, and 1,983 controls for whom water exposure information was available for at least 70% of their lifetime. We estimated exposure to chlorination byproducts with two types of measures: duration of lifetime at residences served by chlorinated water and estimated lifetime trihalomethane exposure. For rectal cancer, we observed an association with duration of chlorinated surface water use, with adjusted odds ratios of 1.1, 1.6, 1.6, and 2.6 for 1–19, 20–39, 40–59, and ≥60 years of exposure, compared with no exposure. Rectal cancer risk was also associated with several different measures of estimated lifetime trihalomethane exposure. For colon cancer and subsites, we detected no important increase in risk associated with duration of chlorinated surface water, nor with trihalomethane estimates. When we evaluated chlorination byproducts jointly with other factors, we found larger relative risk estimates for rectal cancer among subjects with low dietary fiber intake. The risk related to ≥40 years of exposure to a chlorinated surface water source was 2.4 (95% confidence interval = 1.5–4.0) for persons with low fiber intake and 0.9 (95% confidence interval = 0.4–1.8) for persons with high fiber intake, relative to the risk of persons with high-fiber diets and no exposure to chlorinated surface water. We observed a similar risk differential for low and high levels of physical activity.

Waterborne disease outbreaks, 1986-1988.

From 1986 to 1988, 24 states and Puerto Rico reported 50 outbreaks of illness due to water that people intended to drink, affecting 25,846 persons. The protozoal parasite Giardia lamblia was the agent most commonly implicated in outbreaks, as it has been for the last 10 years; many of these outbreaks were associated with ingestion of chlorinated but unfiltered surface water. Shigella sonnei was the most commonly implicated bacterial pathogen; in outbreaks caused by this pathogen, water supplies were found to be contaminated with human waste. Cryptosporidium contamination of a chlorinated, filtered public water supply caused the largest outbreak during this period, affecting an estimated 13,000 persons. A large multistate outbreak caused by commercially produced ice made from contaminated well water caused illness with Norwalk-like virus among an estimated 5,000 persons. The first reported outbreak of chronic diarrhea of unknown cause associated with drinking untreated well water occurred in 1987. Twenty-six outbreaks due to recreational water use were also reported, including outbreaks of Pseudomonas dermatitis associated with the use of hot tubs or whirlpools, and swimming-associated shigellosis, giardiasis, and viral illness. Although the total number of reported water-related outbreaks has been declining in recent years, the few large outbreaks due to Cryptosporidium, Norwalk-like agent, Shigella sonnei, and Giardia lamblia caused more cases of illness in 1987 than have been reported to the Water-Related Disease Outbreak Surveillance System for any other year since CDC and the Environmental Protection Agency began tabulating these data in 1971.From 1986 to 1988, 24 states and Puerto Rico reported 50 outbreaks of illness due to water that people intended to drink, affecting 25,846 persons. The protozoal parasite Giardia lamblia was the agent most commonly implicated in outbreaks, as it has been for the last 10 years; many of these outbreaks were associated with ingestion of chlorinated but unfiltered surface water. Shigella sonnei was the most commonly implicated bacterial pathogen; in outbreaks caused by this pathogen, water supplies were found to be contaminated with human waste. Cryptosporidium contamination of a chlorinated, filtered public water supply caused the largest outbreak during this period, affecting an estimated 13,000 persons. A large multistate outbreak caused by commercially produced ice made from contaminated well water caused illness with Norwalk-like virus among an estimated 5,000 persons. The first reported outbreak of chronic diarrhea of unknown cause associated with drinking untreated well water occurred in 1987. Twenty-six outbreaks due to recreational water use were also reported, including outbreaks of Pseudomonas dermatitis , associated with the use of hot tubs or whirlpools, and swimming-associated shigellosis, giardiasis, and viral illness. Although the total number of reported water-related outbreaks has been declining in recent years, the few large outbreaks due to Cryptosporidium , Norwalk-like agent, S. sonnei , and G. lamblia caused more cases of illness in 1987 than have been reported to the Water-Related Disease Outbreak Surveillance System for any other year since CDC and the Environmental Protection Agency began tabulating these data in 1971.

How clean must our drinking water be: the importance of protective immunity.

BACKGROUND Cryptosporidium parvum is an important cause of epidemic diarrhea. Few studies have assessed whether serological evidence of prior infection in adults is related to a reduced occurrence of enteric illness. METHODS Serum samples and enteric illness event data were obtained in 2000 and 2001 from 326 people served by 1 of 2 unfiltered surface sources or 1 groundwater source. In 2001, filtration was initiated at 1 of the surface sources. Poisson regression related illness episodes with serological responses to the 15/17- and 27-kDa Cryptosporidium antigen groups. RESULTS Subjects with moderately strong responses to the 15/17-kDa antigen had <65% of the risk of all 1-3-day episodes of diarrheal or gastrointestinal illness and <40% of the risk of all >/=4-day episodes, compared with subjects without a moderately strong response. Water source, change in water treatment, and very weak responses were unrelated to illness events. CONCLUSIONS Endemic Cryptosporidium infections are a common cause of diarrheal and gastrointestinal illness in persons without a moderately strong response to the 15/17-kDa antigen group. Users of surface-derived drinking water are more likely to have strong serological responses to this antigen group and may be at a lower risk of endemic gastrointestinal illness caused by Cryptosporidium infection.

Review of epidemiological studies on drinking water hardness and cardiovascular diseases

Background Major risk factors do not entirely explain the worldwide variability of morbidity and mortality due to cardiovascular disease. Environmental exposures, including drinking water minerals may affect cardiovascular disease risks. Method We conducted a qualitative review of the epidemiological studies of cardiovascular disease and drinking water hardness and calcium and magnesium levels. Results Many but not all ecological studies found an inverse (i.e., protective) association between cardiovascular disease mortality and water hardness, calcium, or magnesium levels; but results are not consistent. Some case-control studies and one cohort study found either a reduced cardiovascular disease mortality risk with increased drinking water magnesium levels or an increased risk with low magnesium levels. However, the analytical studies provide little evidence that cardiovascular risks are associated with drinking water hardness or calcium levels. Conclusion Information from epidemiological and other studies supports the hypothesis that a low intake of magnesium may increase the risk of dying from, and possibly developing, cardiovascular disease or stroke. Thus, not removing magnesium from drinking water, or in certain situations increasing the magnesium intake from water, may be beneficial, especially for populations with an insufficient dietary intake of the mineral.

Waterborne Outbreaks of Giardiasis

Giardiasis is endemic in many countries of the world including the United States, and in recent years, Giardia lamblia has been identified as the etiologic agent in numerous common-source outbreaks. The waterborne transmission of G. lamblia was suggested as early as 1946 by an epidemiologic investigation of an outbreak of amebiasis attributed to sewage contamination of a water supply in a Tokyo apartment building (Davis and Ritchie, 1948). Entamoeba histolytica and G. lamblia were recovered from 96 (64%) and 116 (77%) occupants, respectively; G. lamblia was isolated from 86% of the occupants who experienced diarrhea with abdominal discomfort and had stools that were negative for E. histolytica.

Serological evidence of endemic waterborne cryptosporidium infections.

PURPOSE Cryptosporidium oocysts are commonly detected in surface-derived drinking water, however, the public health significance of these findings is unclear. This study compared the evidence of prior Cryptosporidium infection for people drinking water derived from surface versus ground water sources. METHODS This study measured serological responses to two Cryptosporidium antigen groups for blood donors from two midwestern United States cities with different drinking water sources: filtered and chlorinated river water receiving agricultural and domestic sewage upstream versus chlorinated water from an underground aquifer. Initial and nine-month paired serological responses to two Cryptosporidium antigen groups were compared. RESULTS Initially, donors from the surface water city had a higher relative prevalence (RP) of a serological response (54% vs. 38%, RP = 1.39 (1.21,1.60)). Donors with a detectable baseline response who resided in the surface water city had a higher relative risk (RR) of an increased intensity of response on the follow-up blood draw (15/17-kDa, 40/100 vs. 11/100, RR = 3.78 (1.89,7.58)), (27-kDa 38/100 vs. 18/100, RR = 2.07 (1.31,3.25)). Donors with no baseline response to the 15/17-kDa marker who resided in the surface water city also had a higher risk of serconversion (38/100 vs. 14/100, RR = 2.63 (1.78,3.91)). CONCLUSIONS These rates of both background and drinking water related Cryptosporidium infections are substantially higher than previously estimated, however, the risk of illness from infection may be lower.

Protective Immunity Associated with a Strong Serological Response to a Cryptosporidium-Specific Antigen Group, in HIV-Infected Individuals

This study assessed whether serological responses to Cryptosporidium antigens are associated with a reduced risk of diarrheal illness in cases of infection with human immunodeficiency virus (HIV). The association between serological responses to the Cryptosporidium 15/17-kDa and 27-kDa antigen groups and reported diarrheal illness was examined by use of data from a previously published study of cases of HIV infection. In immunosuppressed individuals, a strong serological response to the 27-kDa antigen group was associated with a reduced risk of diarrhea without weight loss. This finding suggests that acquired protective immunity to cryptosporidiosis may be important in controlling the burden of cryptosporidiosis in immunosuppressed individuals.