HIV incidence estimates and HIV/AIDS concurrent diagnosis in Houston/Harris County

The purpose of this dissertation was to estimate HIV incidence among the individuals who had HIV tests performed at the Houston Department of Health and Human Services (HDHHS) public health laboratory, and to examine the prevalence of HIV and AIDS concurrent diagnoses among HIV cases reported between 2000 and 2007 in Houston/Harris County. ^ The first study in this dissertation estimated the cumulative HIV incidence among the individuals testing at Houston public health laboratory using Serologic Testing Algorithms for Recent HIV Seroconversion (STARHS) during the two year study period (June 1, 2005 to May 31, 2007). The HIV incidence was estimated using two independently developed statistical imputation methods, one developed by the Centers for Disease Control and Prevention (CDC), and the other developed by HDHHS. Among the 54,394 persons who tested for HIV during the study period, 942 tested HIV positive (positivity rate=1.7%). Of these HIV positives, 448 (48%) were newly reported to the Houston HIV/AIDS Reporting System (HARS) and 417 of these 448 blood specimens (93%) were available for STARHS testing. The STARHS results showed 139 (33%) out of the 417 specimens were newly infected with HIV. Using both the CDC and HDHHS methods, the estimated cumulative HIV incidences over the two-year study period were similar: 862 per 100,000 persons (95% CI: 655-1,070) by CDC method, and 925 per 100,000 persons (95% CI: 908-943) by HDHHS method. Consistent with the national finding, this study found African Americans, and men who have sex with men (MSM) accounted for most of the new HIV infections among the individuals testing at Houston public health laboratory. Using CDC statistical method, this study also found the highest cumulative HIV incidence (2,176 per 100,000 persons [95%CI: 1,536-2,798]) was among those who tested in the HIV counseling and testing sites, compared to the sexually transmitted disease clinics (1,242 per 100,000 persons [95%CI: 871-1,608]) and city health clinics (215 per 100,000 persons [95%CI: 80-353]. This finding suggested the HIV counseling and testing sites in Houston were successful in reaching high risk populations and testing them early for HIV. In addition, older age groups had higher cumulative HIV incidence, but accounted for smaller proportions of new HIV infections. The incidence in the 30-39 age group (994 per 100,000 persons [95%CI: 625-1,363]) was 1.5 times the incidence in 13-29 age group (645 per 100,000 persons [95%CI: 447-840]); the incidences in 40-49 age group (1,371 per 100,000 persons [95%CI: 765-1,977]) and 50 or above age groups (1,369 per 100,000 persons [95%CI: 318-2,415]) were 2.1 times compared to the youngest 13-29 age group. The increased HIV incidence in older age groups suggested that persons 40 or above were still at risk to contract HIV infections. HIV prevention programs should encourage more people who are age 40 and above to test for HIV. ^ The second study investigated concurrent diagnoses of HIV and AIDS in Houston. Concurrent HIV/AIDS diagnosis is defined as AIDS diagnosis within three months of HIV diagnosis. This study found about one-third of the HIV cases were diagnosed with HIV and AIDS concurrently (within three months) in Houston/Harris County. Using multivariable logistic regression analysis, this study found being male, Hispanic, older, and diagnosed in the private sector of care were positively associated with concurrent HIV and AIDS diagnoses. By contrast, men who had sex with men and also used injection drugs (MSM/IDU) were 0.64 times (95% CI: 0.44-0.93) less likely to have concurrent HIV and AIDS diagnoses. A sensitivity analysis comparing difference durations of elapsed time for concurrent HIV and AIDS diagnosis definitions (1-month, 3-month, and 12-month cut-offs) affected the effect size of the odds ratios, but not the direction. ^ The results of these two studies, one describing characteristics of the individuals who were newly infected with HIV, and the other study describing persons who were diagnosed with HIV and AIDS concurrently, can be used as a reference for HIV prevention program planning in Houston/Harris County. ^

Antibody response to Panton-Valentine Leukocidin, a Staphylococcus aureus virulence factor, in pediatric patients from Texas Children's Hospital in Houston, Texas

Staphylococcus aureus is an important human pathogen of global health significance, whose frequency is increasing and whose persistence and versatility allow it to remain established in communities worldwide. An observed significant increase in infections, particularly in children with no predisposing risk factors or medical conditions, led to an investigation into pediatric humoral immune response to Panton-Valentine Leukocidin (PVL) and to other antigens expressed by S. aureus that represent the important classes of virulence activities. Patients who were diagnosed with staphylococcal infections were enrolled (n=60), and serum samples collected at the time of admission were analyzed using ELISA and Western blot to screen for immune response to the panel of recombinant proteins. The dominant circulating immunoglobulin titers in this pediatric population were primarily IgG, were specific, and were directed against LukF and LukS, while suppression of other important virulence factors in the presence of PVL was suggested. Patients with invasive infections (osteomyelitis, pneumonia or myositis) had higher titers against LukF and LukS compared to patients with non-invasive infections (abscesses, cellulitis or lymphadenitis). In patients with osteomyelitis, antibody responses to LukF and LukS were higher than antibody responses to any other virulence factor examined. This description of immune response to selected virulence factors of S. aureus caused by isolates of the USA300 lineage in children is novel. Antibody titers also correlated with markers of inflammation. The significance of these correlations remains to be understood.^

Industrial benzene emissions in Houston: Legal barriers to reducing a public health threat

Decades of research show that environmental exposure to the chemical benzene is associated with severe carcinogenic, hematoxic and genotoxic effects on the human body. As such, the Environmental Protection Agency (EPA) has designated the chemical as a Hazardous Air Pollutant and prescribed benzene air concentration guidelines that provide cities with an ideal ambient level to protect human health. However, in Houston, Texas, a city home to the top industrial benzene emitters in the US who undoubtedly contribute greatly to the potentially unsafe levels of ambient benzene, regulations beyond the EPA’s unenforceable guidelines are critical to protecting public health. Despite this, the EPA has failed to establish National Ambient Air Quality Standards (NAAQS) for benzene. States are thus left to regulate air benzene levels on their own; in the case of Texas, the Texas Commission on Environmental Quality (TCEQ) and state legislature have failed to proactively develop legally enforceable policies to reduce major source benzene emissions. This inaction continues to exacerbate a public health problem, which may only be solved through a legal framework that restricts preventable benzene emissions to protect human health and holds industrial companies accountable for violations of such regulations and standards. This analysis explores legal barriers that the City of Houston and other relevant agencies currently face in their attempt to demand and bring about such change. ^

Risk factors for encephalitis and death from West Nile virus infection: An analysis of hospitalized cases in Houston, Texas from 2002--2008

We conducted a nested case-control study to determine the significant risk factors for developing encephalitis from West Nile virus (WNV) infection. The purpose of this research project was to expand the previously published Houston study of 2002–2004 patients to include data on Houston patients from four additional years (2005–2008) to determine if there were any differences in risk factors shown to be associated with developing the more severe outcomes of WNV infection, encephalitis and death, by having this larger sample size. A re-analysis of the risk factors for encephalitis and death was conducted on all of the patients from 2002–2008 and was the focus of this proposed research. This analysis allowed for the determination to be made that there are differences in the outcome in the risk factors for encephalitis and death with an increased sample size. Retrospective medical chart reviews were completed for the 265 confirmed WNV hospitalized patients; 153 patients had encephalitis (WNE), 112 had either viral syndrome with fever (WNF) or meningitis (WNM); a total of 22 patients died. Univariate logistic regression analyses on demographic, comorbidities, and social risk factors was conducted in a similar manner as in the previously conducted study to determine the risk factors for developing encephalitis from WNV. A multivariate model was developed by using model building strategies for the multivariate logistic regression analysis. The hypothesis of this study was that there would be additional risk factors shown to be significant with the increase in sample size of the dataset. This analysis with a greater sample size and increased power supports the hypothesis in that there were additional risk factors shown to be statistically associated with the more severe outcomes of WNV infection (WNE or death). Based on univariate logistic regression results, these data showed that even though age of 20–44 years was statistically significant as a protecting effect for developing WNE in the original study, the expanded sample lacked significance. This study showed a significant WNE risk factor to be chronic alcohol abuse, when it was not significant in the original analysis. Other WNE risk factors identified in this analysis that showed to be significant but were not significant in the original analysis were cancer not in remission > 5 years, history of stroke, and chronic renal disease. When comparing the two analyses with death as an outcome, two risk factors that were shown to be significant in the original analysis but not in the expanded dataset analysis were diabetes mellitus and immunosuppression. Three risk factors shown to be significant in this expanded analysis but were not significant in the original study were illicit drug use, heroin or opiate use, and injection drug use. However, with the multiple logistic regression models, the same independent risk factors for developing encephalitis of age and history of hypertension including drug induced hypertension were consistent in both studies.^

Suspected outbreak of dengue fever in Houston: Clinical characteristics and determination of autochthonous transmission between 2003 and 2005

Houston, Texas maintains the appropriate climate and mosquito populations to support the circulation of dengue viruses. The city is susceptible to the introduction and subsequent local transmission of dengue virus with its proximity to dengue-endemic Mexico and the high degree of international travel routed through its airports. In 2008, a study at the University of Texas School of Public Health identified 58 suspected dengue fever cases that presented at hospitals and clinics in the Houston area. Serum or CSF samples of the 58 samples tested positive or equivocal for the presence of anti-dengue IgM antibodies (Rodriguez, 2008). Here, we present the results of an investigation aimed to describe the clinical characteristics of the 58 suspected dengue fever cases and to determine if local transmission had occurred. Data from medical record abstractions and personal telephone interviews were used to describe clinical characteristics and travel history of the suspected cases. Our analysis classified six probable dengue fever cases based on the case definition from the World Health Organization. Three of the probable cases for which we were able to obtain travel history had not recently traveled to an endemic area prior to onset of symptoms suggesting the illnesses were locally acquired in Houston. Further analysis led us to hypothesize that additional cases of dengue fever are present in our study population. Fifty-one percent of the study population was diagnosed with meningitis and/or encephalitis. Sixty percent of the individuals who received a lumbar puncture had abnormal CSF. Together these findings indicate viral infection with neurological involvement, which has been reported to occur with dengue fever. Among the individuals who received liver enzyme analysis, 54% had evidence of abnormal liver enzyme levels, a clinical sign commonly observed with dengue. Our results indicate that a suspected outbreak of dengue fever with autochthonous transmission occurred in the Houston area between 2003 and 2005. ^

An analysis of the RightCare policy at Ben Taub General Hospital, Houston, Texas

Introduction. This study is a two-part evaluation of the RightCare policy, a policy implemented to reduce crowding at the Emergency Center (EC) at Ben Taub General Hospital in Houston, Harris County, Texas. This research includes an evaluation of the policy's impact on specific hospital measures, along with a description of the policy's demise from the point of view of hospital staff. Objective. The purpose of this study is two-fold: (1) To determine whether RightCare policy affected the level of crowding in the Emergency Center and (2) to identify the conditions that may have led to the policy's demise. Methods. For the policy impact portion of this research, hospital measures were collected from existing databases. Analysis included a pre-post comparative design in which the 12 months preceding the policy's implementation were compared with the 12 months following the policy's implementation. For the policy perception portion, employees were surveyed using an on-line questionnaire. Results. The results of the study are mixed. Some measures improved, including time spent on ambulance diversion and the proportion of those who left without being seen, while others did not, such as return visits and total length of stay. Employees generally supported the policy, but expressed concerns over insufficient training and funding. Conclusion. The RightCare policy was a good initial attempt to improve crowded conditions in the EC. The study showed that a clearer policy design, improved training, adequate staffing levels, and better communication would improve operational outcomes in the future.^

Understanding causes of hospitalization and access to care among newly diagnosed HIV patients in Houston, TX

More than a quarter of patients with HIV in the United States are diagnosed in hospital settings most often with advanced HIV related conditions.(1) There has been little research done on the causes of hospitalization when the patients are first diagnosed with HIV. The aim of this study was to determine if the patients are hospitalized due to an HIV related cause or due to some other co-morbidity. Reduced access to care could be one possible reason why patients are diagnosed late in the course of the disease. This study compared the access to care of patients diagnosed with HIV in hospital and outpatient setting. The data used for the study was a part of the ongoing study “Attitudes and Beliefs and Steps of HIV Care”. The participants in the study were newly diagnosed with HIV and recruited from both inpatient and outpatient settings. The primary and the secondary diagnoses from hospital discharge reports were extracted and a primary reason for hospitalization was ascertained. These were classified as HIV-related, other infectious causes, non–infectious causes, other systemic causes, and miscellaneous causes. Access to care was determined by a score based on responses to a set of questions derived from the HIV Cost and Services Utilization Study (HCSUS) on a 6 point scale. The mean score of the hospitalized patients and mean score of the patients diagnosed in an outpatient setting was compared. We used multiple linear regressions to compare mean differences in the two groups after adjusting for age, sex, race, household income educational level and health insurance at the time of diagnosis. There were 185 participants in the study, including 78 who were diagnosed in hospital settings and 107 who were diagnosed in outpatient settings. We found that HIV-related conditions were the leading cause of hospitalization, accounting for 60% of admissions, followed by non-infectious causes (20%) and then other infectious causes (17%). The inpatient diagnosed group did not have greater perceived access-to-care as compared to the outpatient group. Regression analysis demonstrated a statistically significant improvement in access-to-care with advancing education level (p=0.04) and with better health insurance (p=0.004). HIV-related causes account for many hospitalizations when patients are first diagnosed with HIV. Many of these HIV-related hospitalizations could have been prevented if patients were diagnosed early and linked to medical care. Programs to increase HIV awareness need to be an integral part of activities aimed at control of spread of HIV in the community. Routine testing for HIV infection to promote early HIV diagnosis can prevent significant morbidity and mortality.^

Evaluation of a solid phase microextraction method for community-based monitoring of 1,3-butadiene and benzene in Houston, Texas

The Houston region is home to arguably the largest petrochemical and refining complex anywhere. The effluent of this complex includes many potentially hazardous compounds. Study of some of these compounds has led to recognition that a number of known and probable carcinogens are at elevated levels in ambient air. Two of these, benzene and 1,3-butadiene, have been found in concentrations which may pose health risk for residents of Houston.^ Recent popular journalism and publications by local research institutions has increased the interest of the public in Houston's air quality. Much of the literature has been critical of local regulatory agencies' oversight of industrial pollution. A number of citizens in the region have begun to volunteer with air quality advocacy groups in the testing of community air. Inexpensive methods exist for monitoring of ozone, particulate matter and airborne toxic ambient concentrations. This study is an evaluation of a technique that has been successfully applied to airborne toxics.^ This technique, solid phase microextraction (SPME), has been used to measure airborne volatile organic hydrocarbons at community-level concentrations. It is has yielded accurate and rapid concentration estimates at a relatively low cost per sample. Examples of its application to measurement of airborne benzene exist in the literature. None have been found for airborne 1,3-butadiene. These compounds were selected for an evaluation of SPME as a community-deployed technique, to replicate previous application to benzene, to expand application to 1,3-butadiene and due to the salience of these compounds in this community. ^ This study demonstrates that SPME is a useful technique for quantification of 1,3-butadiene at concentrations observed in Houston. Laboratory background levels precluded recommendation of the technique for benzene. One type of SPME fiber, 85 μm Carboxen/PDMS, was found to be a sensitive sampling device for 1,3-butadiene under temperature and humidity conditions common in Houston. This study indicates that these variables affect instrument response. This suggests the necessity of calibration within specific conditions of these variables. While deployment of this technique was less expensive than other methods of quantification of 1,3-butadiene, the complexity of calibration may exclude an SPME method from broad deployment by community groups.^

HIV disclosure decisions and social support among African-American women in Houston, Texas

African Americans make up 12.3% of the population but account for over half of the new HIV cases and 39% of the AIDS cases in 2003 (Centers for Disease Control and Prevention [CDC], 2003). African American women in particular accounted for 64% of these cases of HIV and 60% of the AIDS cases (Leigh & Huff, 2003). This study contributed to the knowledge about the disclosure process of women living with HIV/AIDS by documenting the relationship between social support and the disclosure process in the African American HIV/AIDS population.^ The study aims were to: (1) discuss the participants' self concept of support; (2) describe the common characteristics of the disclosure process; and (3) evaluate the common characteristics of support sought in a potential disclosure source. The ethnographic qualitative methodology was utilized to elicit participant narratives of HIV disclosure and social support. The researcher utilized a key informant interview methodology building on existing social and organizational relationships (Krueger, 1994) to gain access to the population. ^ Semi-structured interviews are a widely used and accepted qualitative research method for use with hard to reach populations and sensitive topics. Ten participants completed a 45 to 60 minute, one on one semi-structured interview covering social support and disclosure variables. Inclusion and exclusion criteria included: (1) self identified as a person living with HIV/AIDS; (2) African American); (3) female; (4) age 18-64 years old, (5) residence in Houston or surrounding counties.^ Themes generated from the interviews were (1) nondisclosure, (2) experiences with disclosure, (3) timing, (4) disclosure sources, and (5) coping. The themes suggest African American women living with HIV/AIDS come from different lifestyles but share similar experiences. Women utilize different strategies such as deciphering whom to trust and determining how much information to divulge in order to protect themselves or others.^ Although the sample group was small for this study, the results inform us about the various experiences each woman goes through as it relates to social support and disclosure and that each woman has to customize her response to the type of support she is receiving and her personal attitude about her disease.^

An evaluation of the Cypress Creek watershed for inorganic chemical load as it flows into Lake Houston

Background. The Cypress Creek is one of the main tributaries of Lake Houston, which provides drinking water to 21.4 million customers. Furthermore, the watershed is being utilized for contact and non-contact recreation, such as canoeing, swimming, hiking trail, and picnics. Water along the creek is impacted by numerous wastewater outfalls from both point and non-point sources. As the creek flows into Lake Houston, it carries both organic and inorganic contaminants that may affect the drinking water quality of this important water source reservoir. Objective. This study was carried out to evaluate the inorganic chemical load of the water in Cypress Creek along its entire length, from the headwaters in Waller County and up to the drainage into Lake Houston. The purpose was to determine whether there are hazardous concentrations of metals in the water and what would be the likely sources. Method. Samples were collected at 29 sites along the creek and analyzed for 29 metals, 17 of which were on the Environmental Protection Agency priority pollution list. Public access sites primarily at bridges were used for sample collection. Samples were transported on ice to the University Of Texas School Of Public Health laboratory, spiked with 2 ml HNO3 kept overnight in the refrigerator, and the following day transported to the EPA laboratory for analysis. Analysis was done by EPA Method 200.7-ICP, Method 200.8ICP/MS and Method 245.1-CVAAS. Results. Metals were present above the detection limits at 65% of sites. Concentrations of aluminum, iron, sodium, potassium, magnesium, and calcium, were particularly high at all sites. Aluminum, sodium, and iron concentrations greatly exceeded the EPA secondary drinking water standards at all sites. ^ Conclusion. The recreational water along Cypress Creek is impacted by wastewater from both permitted and non-permitted outfalls, which deposit inorganic substances into the water. Although a number of inorganic contaminants were present in the water, toxic metals regulated by the EPA were mostly below the recommended limits. However, high concentrations of aluminum, sodium, and iron in the Cypress Creek bring forward the issue of unauthorized discharges of salt water from mining, as well as industrial and domestic wastewater.^

Sex, drugs, and STIs: Syphilis infection and hepatitis B vaccine compliance among illicit drug users in Houston

Although the association between syphilis infection status and compliance with the hepatitis B virus vaccine has been the focus of investigation, there is a lack of data regarding the association between syphilis infection and HBV vaccine compliance. The author investigated the association between the exposure of syphilis infection and the outcome of HBV vaccine completion, defined as degree of constancy and accuracy with which a patient follows a prescribed regimen. A cohort design was employed using interview and serological data from the Drugs, AIDS, STDs, Hepatitis (DASH) Research Project; analysis was restricted to HIV and HBV seronegative (at baseline), illicit drug users residing in Harris County. Syphilis negative and syphilis positive infection status was determined from the serological data while covariates and outcome information were determined from the DASH Project Questionnaire; enrolled subjects (n=1160) were selected from the data. Association between exposure and outcome was assessed with logistic regression adjusted for data-based confounders. ^ A prevalence of 7% and 71% was found for syphilis and HBV vaccine compliance, respectively. When measuring the actual association between syphilis infection status and HBV vaccine compliance, an odds ratio of 1.49 (95% CI: 0.86, 2.72) was obtained. There was a non-significant association between these two variables. 78% of the study population was syphilis positive and completed the vaccine series compared to 70% of the population that was syphilis negative and received all three doses. This finding confirms that there is a difference between syphilis positive and negative drug users with respect to HBV vaccine compliance. The fact that differences were found in these drug users with respect to vaccine schedule supports the idea that sub-group differences may exist and thus merits further investigation. If these differences are confirmed, it is recommended that STI interventions identify community characteristics of their samples and target populations based on practices specific to that community. ^

Epidemiology of tuberculosis and nontuberculous mycobacterial infections in Houston children

Background. Nontuberculous mycobacteria (NTM) are environmentally ubiquitous organisms whose epidemiology is poorly understood. Species differ with respect to disease presentation, prognosis, and antimicrobial susceptibility. We reviewed one Texas pediatric hospital's experience with NTM and tuberculosis (TB) disease.^ Methods. This was a retrospective case series of children with culture-confirmed mycobacterial infections seen at a children's hospital from 2003-2008.^ Results. One hundred sixty-two isolates were identified from 150 children; 132 (81.5%) had NTM species isolated, and 30 (18.5%) had M. tuberculosis isolated; 2 children had both NTM and M. tuberculosis isolated. The most common species were Mycobacterium avium complex (MAC) (29%), M. tuberculosis (18.5%), M. abscessus (13%), M. fortuitum (11.7%), and M. chelonae-abscessus (9.9%). TB was the most common organism isolated from respiratory specimens. MAC and M. simiae were significantly more likely to be associated with lymphadenopathy than other NTM species (p < 0.001). Mycobacterium fortuitum was significantly more likely to be associated with soft tissue infections than other NTM species (p < 0.001). Seventy-five children met criteria for NTM disease (30 lymphadenopathy, 17 pulmonary, 17 soft tissue infections, 11 bacteremia). Children with NTM lymphadenopathy were more likely to be Hispanic (OR 24, CI 2.8-1063), younger (3.3 years vs. 10.6 years, p < 0.001), and previously healthy (OR 0.004, CI 0-0.06) than children with NTM pulmonary disease. Children with NTM disease were less likely to be previously healthy (OR 0.30, 95% CI 0.09-0.88) and foreign-born (OR 0.09, CI 0.03-0.29) than children with TB.^ Conclusions. Children with NTM lymphadenopathy were younger and more likely to be healthy than children with NTM pulmonary disease. Tuberculosis comprised a large proportion of mycobacterial disease in this series. Children with NTM pulmonary disease were less likely to be previously healthy and born abroad when compared to children with TB. There was wide variation in antimicrobial susceptibility patterns among NTM species. This, together with the large percentage of disease caused by TB, emphasizes the importance of securing a specific microbiologic diagnosis in children with pulmonary or lymph node disease caused by mycobacteria.^

Characterization of the East Houston particulate matter <2.5 atmosphere; a novel method for desorbing organic constituents from airborne particulates

I have developed a novel approach to test for toxic organic substances adsorbed onto ultra fine particulate particles present in the ambient air in Northeast Houston, Texas. These particles are predominantly carbon soot with an aerodynamic diameter (AD) of <2.5 μm. If present in the ambient air, many of the organic substances will be absorbed to the surface of the particles (which act just like a charcoal air filter), and may be adducted into the respiratory system. Once imbedded into the lungs these particles may release the adsorbed toxic organic substances with serious health consequences. I used a Airmetrics portable Minivol air sampler time drawing the ambient air through collection filters samples from 6 separate sites in Northeast Houston, an area known for high ambient PM 2.5 released from chemical plants and other sources (e.g. vehicle emissions).(1) In practice, the mass of the collected particles were much less than the mass of the filters. My technique was designed to release the adsorbed organic substances on the fine carbon particles by heating the filter samples that included the PM 2.5 particles prior to identification by gas chromatography/mass spectrometry (GCMS). The results showed negligible amounts of target chemicals from the collection filters. However, the filters alone released organic substances and GCMS could not distinguish between the organic substances released from the soot particles from those released from the heated filter fabric. However, an efficacy tests of my method using two wax burning candles that released soot revealed high levels of benzene. This suggests that my method has the potential to reveal the organic substances adsorbed onto the PM 2.5 for analysis. In order to achieve this goal, I must refine the particle collection process which would be independent of the filters; the filters upon heating also release organic substances obscuring the contribution from the soot particles. To obtain pure soot particles I will have to filter more air so that the soot particles can be shaken off the filters and then analyzed by my new technique. ^

Health significance of chlorination byproducts in drinking water: The Houston experience: A continuation study

Background. Houston, Texas, once obtained all its drinking water from underground sources. However, in 1853, the city began supplementing its water from the surface source Lake Houston. This created differences in the exposure to disinfection byproducts (DBPs) in different parts of Houston. Trihalomethanes (THMs) are the most common DBP and are useful indicators of DBPs in treated drinking water. This study examines the relationship between THMs in chlorinated drinking water and the incidence of bladder cancer in Houston. ^ Methods. Individual bladder cancer deaths, from 1975 to 2004, were assigned to four surface water exposure areas in Houston utilizing census tracts—area A used groundwater the longest, area B used treated lake water the longest, area C used treated lake water the second longest, and area D used a combination of groundwater and treated lake water. Within each surface water exposure area mortality rates were calculated in 5 year intervals by four race-gender categories. Linear regression models were fitted to the bladder cancer mortality rates over the entire period of available data (1990–2004). ^ Results. A decrease in bladder cancer mortality was observed amongst white males in area B (p = 0.030), white females in area A (p = 0.008), non-white males in area D (p = 0.003), and non-white females in areas A and B (p = 0.002 & 0.001). Bladder cancer mortality differed by race-gender and time (p ≤ 0.001 & p ≤ 0.001), but not by surface water exposure area (p = 0.876). ^ Conclusion. The relationship between bladder cancer mortality and the four surface water exposure areas (signifying THM exposure) was insignificant. This result could be attributable to Houston controlling for THMs starting in the early 1980’s by using chloramine as a secondary disinfectant in the drinking water purification process.^

An evaluation of a Lake Houston tributary, Cypress Creek, for contamination and water quality

Introduction. Lake Houston serves as a reservoir for both recreational and drinking water for residents of Houston, Texas, and the metropolitan area. The Texas Commission on Environmental Quality (TCEQ) expressed concerns about the water quality and increasing amounts of pathogenic bacteria in Lake Houston (3). The objective of this investigation is to evaluate water quality for the presence of bacteria, nitrates, nitrites, carbon, phosphorus, dissolved oxygen, pH, turbidity, suspended solids, dissolved solids, and chlorine in Cypress Creek. The aims of this project are to analyze samples of water from Cypress Creek and to render a quantitative and graphical representation of the results. The collected information will allow for a better understanding of the aqueous environment in Cypress Creek.^ Methods. Water samples were collected in August 2009 and analyzed in the field and at UTSPH laboratory by spectrophotometry and other methods. Mapping software was utilized to develop novel maps of the sample sites using coordinates attained with the Global Positioning System (GPS). Sample sites and concentrations were mapped using Geographic Information System (GIS) software and correlated with permitted outfalls and other land use characteristic.^ Results. All areas sampled were positive for the presence of total coliform and Escherichia coli (E. coli). The presences of other water contaminants varied at each location in Cypress Creek but were under the maximum allowable limits designated by the Texas Commission on Environmental Quality. However, dissolved oxygen concentrations were elevated above the TCEQ limit of 5.0 mg/L at majority of the sites. One site had near-limit concentration of nitrates at 9.8 mg/L. Land use above this site included farm land, agricultural land, golf course, parks, residential neighborhoods, and nine permitted TCEQ effluent discharge sites within 0.5 miles upstream.^ Significance. Lake Houston and its tributary, Cypress Creek, are used as recreational waters where individuals may become exposed to microbial contamination. Lake Houston also is the source of drinking water for much of Houston/Harris and Galveston Counties. This research identified the presence of microbial contaminates in Cypress Creek above TCEQ regulatory requirements. Other water quality variables measured were in line with TCEQ regulations except for near-limit for nitrate at sample site #10, at Jarvis and Timberlake in Cypress Texas.^