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Biomedical subjects

I Cech

Publications and source records attributed to I Cech.

12 recordsLinked to original sources
PubMed1992

Water sanitation practices on the Texas-Mexico border: implications for physicians on both sides.

With the epidemic of cholera in South and Central America and reports of cholera in the Northern Hemisphere in Mexico, increasing concern focuses on sanitation problems along the border between the United States and Mexico. It is feared that binationally shared water supplies are threatened or contaminated by sewage and other wastes. Although much anecdotal information exists, surprisingly few hard data are available in the United States (or in Mexico, for that matter) regarding water quality on the Mexican side of the border. This shortage of data is felt most acutely in the semiarid portions of the border, where water is extraordinarily scarce. In 1987, researchers at the University of Texas School of Public Health (UTSPH) began gathering data on the availability, accessibility, and bacteriologic and chemical safety of raw and finished drinking water in Mexico at its border with Texas. In view of their timely significance, we wish to share pertinent data. This particular study was carried out in Ciudad Juarez, a city of more than 1 million people, situated just across the Rio Grande from the Texas city of El Paso. The investigation was conducted at the invitation and with the assistance of municipal authorities of Cd. Juarez. As far as we know, this was the first time the water in Cd. Juarez had been tested for indicator fecal bacteria and other selected contaminants.

Enterobacteriaceae↗
PubMed1987

Health significance of chlorination byproducts in drinking water: the Houston experience.

In 1954, following the construction of Lake Houston, a change from lightly chlorinated ground sources to a heavily chlorinated surface source of drinking water took place for a sizable part of the population in the city of Houston, Texas. This has provided the opportunity to compare the incidence of urinary tract cancer mortality in populations exposed to heavily chlorinated and lightly chlorinated drinking water. The spatial, diurnal, and seasonal concentrations of chlorination byproducts (trihalomethanes) in Houston water were assessed. The range of concentrations varied from below the limits of detection in treated ground water, to more than 200 mg/l (twice the level allowed by US drinking water standards) in treated lake water. The mortality experience by gender, by race, and by age cohorts for the period 1940 to 1970 from urinary tract cancers and three comparison causes was determined for 56 of Houston's census tracts classified by the duration of exposure to the surface water. By the 1970's 20 years following the switch to surface water, an increase was detected in urinary cancer mortality rates for white females without a corresponding increase observed for white males. No clear-cut trends were found for the non-white population. On balance, a detrimental urinary cancer effect associated with a switch to chlorinated surface water has not been demonstrated yet.

Adolescent↗
PubMed1984

Selenium availability in Texas: possible clinical significance.

In light of recent reports that have indicated that selenium is an essential micronutrient and possible natural cancer inhibitor, data on the geographic distributions of selenium in Texas were gathered and compared with the distribution of age-adjusted cancer mortality rates. We considered concentrations of selenium measured in ground and surface water to be indicators of its presence in rocks, soil, and locally grown crops. Texas water sources were found to be poor in selenium, except for the Panhandle and the West Texas regions, where soil consists of erosion products from the selenium-rich Rocky Mountains. In general, lower cancer mortality was observed for the selenium-rich regions of Texas compared with cancer mortality for the selenium-poor regions. Even though the risks from cancer-provoking factors also differed geographically, the observed pattern was sufficiently suggestive to warrant further attention to selenium.

Female↗
PubMed1980

Relationships between environmental factors, bacterial indicators, and the occurrence of enteric viruses in estuarine sediments.

Current standards for evaluation of the public health safety of recreational and shellfish-harvesting waters are based upon bacteriological analysis, but do not include an evaluation of the number of viruses. The objective of this study was to determine the occurrence of enteric viruses in estuarine sediments and to find a relationship, if any, between the presence of viruses in seawater or sediment or both and various biological and physicochemical characteristics of the environment. Viruses were found in greater numbers in sediment than in overlying seawater on a volume basis. Several types of enteroviruses were isolated: coxsackievirus types A16, B1, and B5, echovirus type 1, and poliovirus type 2. On several occasions, viruses were isolated from sediments when overlying seawaters met bacteriological water quality standards for recreational use. Statistical analysis of the relationship between viruses in seawater or in sediment and other variables measured yielded only one significant association: the number of viruses in sediment was found to be positively correlated with the number of fecal coliforms in sediment. No other physical, chemical, or biological characteristic of seawater or sediment that was measured showed statistically significant association with viral numbers. No correlation was found between bacterial indicators and virus in the overlying waters. The data indicated that evaluation of the presence of bacteria and viruses in sediment may provide additional insight into long-term water quality conditions and that indicator bacteria in water are not reflective of the concentration of enteric viruses in marine waters.

Clostridium↗
PubMed1980

Effects of environmental variables and soil characteristics on virus survival in soil.

Because of the increasing emphasis placed upon land application as a means of wastewater disposal, it is important to evaluate the influences of different factors upon virus survival in soil. The objective of this study was to measure the effects of various environmental variables on virus persistence. Test samples of soil were placed in vials, and the soil was wetted with suspensions of virus in either distilled water, unchlorinated secondary sewage effluent, or mixtures of effluent and water. The viruses used were coxsackieviruses A9 and B3, echovirus 1, poliovirus 2, rotavirus SA11, and bacteriophages T2 and MS2. The rate of virus inactivation was evaluated statistically with regard to conditions under which the vials were incubated and to the soil characteristics. The factors that were found to influence virus survival were temperature, soil moisture content, presence of aerobic microorganisms, degree of virus adsorption to the soil, soil levels of resin-extractable phosphorus, exchangeable aluminium, and soil pH. Overall, temperature and virus adsorption to soil appeared to be the most important factors affecting virus survival.

Adsorption↗
PubMed1979

Failure of indicator bacteria to reflect the occurrence of enteroviruses in marine waters.

The results of several studies conducted along the upper Texas Gulf coast, where a substantial amount of quantitative virological data were collected, are compared to bacteriological indicators and other environmental factors on a statistical basis. Variables common to all these studies were anlayzed by multivariate regression. Although multivariate analysis indicated that the number of viruses detected in water was related to rainfall, salinity, and total coliforms in the water, the amount of variation in the number of viruses accounted for by these factors was not large enough to make them good predictors. Enteroviruses were detected 43 per cent of the time in recreational waters considered acceptable as judged by coliform standards, and 44 per cent of the time when judged by fecal coliform standards. Enteroviruses were detected 35 per cent of the time in waters which met acceptable standards for shellfish-harvesting. Our failure to correlate the occurrence of enteroviruses in marine waters with indicator bacteria, and the frequent occurrence of enteroviruses in water which met current bacteriological standards, indicates that these standards do not reflect the occurrence of enteroviruses, and perhaps other human pathogenic viruses, in marine waters.

Animals↗
PubMed1977

Meteorologic factors and temporal variations of cardiac mortality in an urban setting in a desert climatic zone.

The aim of this investigation was to study, by use of the unbiased and rigorous techniques of lagged cross-covariance and spectral analyses, the associations between daily cardiac mortality and weather conditions in Beersheba, an urban center situated in a hot and dry climatic zone. The results of the analyses point to the existence of seasonal differences in mortality, with a peak in winter. Of greater interest is the statistical documentation of temporal associations between short-term increases in daily mortality and certain weather situations corresponding to the transitional periods of turbulent atmosphere with below normal air temperatures, strong gusty winds and a drop in relative humidity, i.e., conditions accompanying the intrusion of a winter cold wave. The crests in short-term mortality occurred most often within a week of the intrusion of the cold air masses. No consistent cross association was found between high summer temperatures and mortality. The results of this investigation are discussed in the light of those previously reported for Tel Aviv (a coastal city) and Jerusalem (a city situated at a high altitude).

Atmospheric Pressure↗