Biomedical subjects

Howard S Weinberg

Publications and source records attributed to Howard S Weinberg.

7 recordsLinked to original sources

PubMed2006

Occurrence of a new generation of disinfection byproducts.

A survey of disinfection byproduct (DBP) occurrence in the United States was conducted at 12 drinking water treatment plants. In addition to currently regulated DBPs, more than 50 DBPs that rated a high priority for potential toxicity were studied. These priority DBPs included iodinated trihalomethanes (THMs), other halomethanes, a nonregulated haloacid, haloacetonitriles, haloketones, halonitromethanes, haloaldehydes, halogenated furanones, haloamides, and nonhalogenated carbonyls. The purpose of this study was to obtain quantitative occurrence information for new DBPs (beyond those currently regulated and/or studied) for prioritizing future health effects studies. An effort was made to select plants treating water that was high in total organic carbon and/or bromide to enable the detection of priority DBPs that contained bromine and/or iodine. THMs and haloacetic acids (HAAs) represented the two major classes of halogenated DBPs formed on a weight basis. Haloacetaldehydes represented the third major class formed in many of the waters. In addition to obtaining quantitative occurrence data, important new information was discovered or confirmed at full-scale plants on the formation and control of DBPs with alternative disinfectants to chlorine. Although the use of alternative disinfectants (ozone, chlorine dioxide, and chloramines) minimized the formation of the four regulated THMs, trihalogenated HAAs, and total organic halogen (TOX), several priority DBPs were formed at higher levels with the alternative disinfectants as compared with chlorine. For example, the highest levels of iodinated THMs-which are not part of the four regulated THMs-were found at a plant that used chloramination with no prechlorination. The highest concentration of dichloroacetaldehyde was at a plant that used chloramines and ozone; however, this disinfection scheme reduced the formation of trichloroacetaldehyde. Preozonation was found to increase the formation of trihalonitromethanes. In addition to the chlorinated furanones that have been measured previously, brominated furanones-which have seldom been analyzed-were detected, especially in high-bromide waters. The presence of bromide resulted in a shift to the formation of other bromine-containing DBPs not normally measured (e.g., brominated ketones, acetaldehydes, nitromethanes, acetamides). Collectively, -30 and 39% of the TOX and total organic bromine, respectively, were accounted for (on a median basis) bythe sum of the measured halogenated DBPs. In addition, 28 new, previously unidentified DBPs were detected. These included brominated and iodinated haloacids, a brominated ketone, and chlorinated and iodinated aldehydes.

Chromatography, Gas↗

PubMed2006

Exposure to drinking water disinfection by-products and pregnancy loss.

Previous research has suggested that exposure to elevated levels of drinking water disinfection by-products (DBPs) may cause pregnancy loss. In 2000-2004, the authors conducted a study in three US locations of varying DBP levels and evaluated 2,409 women in early pregnancy to assess their tap water DBP concentrations, water use, other risk factors, and pregnancy outcome. Tap water concentrations were measured in the distribution system weekly or biweekly. The authors considered DBP concentration and ingested amount and, for trihalomethanes only, bathing/showering and integrated exposure that included ingestion. On the basis of 258 pregnancy losses, they did not find an increased risk of pregnancy loss in relation to trihalomethane, haloacetic acid, or total organic halide concentrations; ingested amounts; or total exposure. In contrast to a previous study, pregnancy loss was not associated with high personal trihalomethane exposure (> or =75 micro g/liter and > or =5 glasses of water/day) (odds ratio = 1.1, 95% confidence interval: 0.7, 1.7). Sporadic elevations in risk were found across DBPs, most notably for ingested total organic halide (odds ratio = 1.5, 95% confidence interval: 1.0, 2.2 for the highest exposure quintile). These results provide some assurance that drinking water DBPs in the range commonly encountered in the United States do not affect fetal survival.

Abortion, Spontaneous↗

PubMed2006

Aqueous-phase aminolysis: approach for the analysis of epoxides in water.

Trace concentrations of small soluble epoxides are suspected byproducts of drinking water ozonation. However, adequate characterization of epoxide formation is currently limited by the lack of suitable analytical methods to target these chemicals in dilute, but complex aqueous solutions. One potential approach is presented here based on aqueous-phase aminolysis. The method also employs solid-phase extraction, silylation of the solvent extract, and analysis by gas chromatography-mass spectrometry. This approach is demonstrated to be effective for the selective analysis of the epoxides 1,2-epoxybutane, epichlorohydrin, and epifluorohydrin in water with optimized method detection limits of 5-10 ng/L.

Amines↗

PubMed2006

Considerations for improving the accuracy of exposure to disinfection by-products by ingestion in epidemiologic studies.

Disinfection by-product (DBP) exposure characterization studies are often based on the analysis of a limited number of samples collected from a distribution system (DS) in which DBP levels are variable over time and space. A compositing technique was developed to simplify the sample collection procedures for integrating over temporal variations in DBPs measured in terms of trihalomethanes (THMs), haloacetic acids (HAAs), and total organic halogen (TOX). Over the course of 5 days analysis, the single composited sample was within 94-100% of the average THM concentration in all grab samples, 92-105% of HAAs, and 130% of the TOX concentration. Additionally, temporal variability factors such as timing of sample collection and the handling of tap water prior to consumption were found to influence DBP levels in consumers' drinking water. Included in our study of home water use are the effects of boiling which removed up to 98% of THMs and point of use (POU) devices which all showed DBP removal but differed depending on the device used. These factors should be taken into consideration in DBP exposure characterization for epidemiologic studies.

Acetates↗

PubMed2003

Bromate in chlorinated drinking waters: occurrence and implications for future regulation.

Bromate is a contaminant of commercially produced solutions of sodium hypochlorite used for disinfection of drinking water. However, no methodical approach has been carried out in U.S. drinking waters to determine the impact of such contamination on drinking water quality. This study utilized a recently developed method for quantitation of bromate down to 0.05 microg/L to determine the concentration of bromate present in finished waters that had been chlorinated using hypochlorite. Forty treatment plants throughout the United States using hypochlorite in the disinfection step were selected and the levels of bromate in the water both prior to and following the addition of hypochlorite were measured. The levels of bromate in the hypochlorite feedstock were also measured and together with the dosage information provided by the plants and the amount of free chlorine in the feedstock, it was possible to calculate the theoretical level of bromate that would be imparted to the water. A mass balance was performed to compare the level of bromate in finished drinking water samples to that found in the corresponding hypochlorite solution used for treatment. Additional confirmation of the source of elevated bromate levels was provided by monitoring for an increase in the level of chlorate, a co-contaminant of hypochlorite, atthe same point in the treatment plant where bromate was elevated. This study showed that bromate in hypochlorite-treated finished waters varies across the United States based on the source of the chemical feedstock, which can add as much as 3 microg/L bromate into drinking water. Although this is within the current negotiated industry standard that allows up to 50% of the maximum contaminant level (MCL) for bromate in drinking water to be contributed by hypochlorite, it would be a challenge to meet a tighter standard. Given that distribution costs encourage utilities to purchase chemical feedstocks from local suppliers, utilities in certain regions of the United States may be put at a distinct disadvantage if future lower regulations on bromate levels in finished drinking water are put into place. Moreover, with these contaminant levels it would be almost impossible to lower the maximum permissible contribution to bromate in finished water from hypochlorite to 10% of the MCL, which is the norm for other treatment chemicals. Until this issue is resolved, it will be difficult to justify a lowering of the bromate MCL from its current level of 10 to 5 microg/L or lower.

Bromates↗

PubMed2002

Segmented flow injection, UV digestion, and amperometric detection for the determination of total cyanide in wastewater treatment plant effluents.

The currently approved method for the analysis of total cyanide (TCN) in wastewaters has remained virtually unchanged in the 25 years since its initial use; this despite its subjection to a number of interferences, many of which provide a positive bias in cyanide measurements, including the formation of TCN during sample processing and some of which remain undocumented to this day. In particular, many municipal wastewater treatment plant chlorinated effluents throughout North America have often been cited for permit violations on the levels of total cyanide in their effluents measured using this methodology. A recently developed procedure for the analysis of TCN in various matrixes that utilizes segmented flow injection for sample transport and reaction, on-line acidic UV digestion for conversion of complexed cyanide to HCN, and amperometric detection achieved within 4 min of sample injection is demonstrated on chlorinated effluents discharged from municipal wastewater treatment plants. Through a systematic evaluation of the chemistry of the processes involved in this method and an understanding of the complexity of the wastewater matrix, an application was developed that showed consistent reproducibility in measuring TCN in a variety of effluents. The method was employed initially on synthetic solutions containing controlled levels of constituents identified in the literature as interfering with the measurement of TCN through the traditional distillation/colorimetric approach. In its application to the analysis of TCN in chlorinated wastewaters, an approach was evolved that ensured that dechlorination carried out during sample processing did not bias the results of analysis.

Chlorine↗

PubMedDate not supplied

Insights to false positive total cyanide measurements in wastewater plant effluents.

Many publicly owned treatment works in North America are exceeding permitted limits for total cyanide in their wastewater treatment effluents. A recently introduced rapid, segmented, flow-injection analysis procedure using UV digestion and amperometric detection of the membrane-separated cyanide was used to investigate the various scenarios by which elevated cyanide levels might be present in wastewater treatment plant effluent. A number of significant interferences can produce false positive bias during sample analysis with the traditional acid distillation technique, but are minimized or absent with the new analytical method. However, increased levels of cyanide were found in some chlorinated wastewaters compared to the levels before chlorination, suggesting a fast reaction mechanism associated with the disinfectant and some precursor in the wastewater. In particular, the contact of chlorine with nitrite in the presence of a carbon precursor appears to contribute to cyanide formation during wastewater treatment and sample handling. This paper explores the scenarios under which cyanide can form during wastewater treatment as well as those in which a false bias for total cyanide can be obtained during sample processing and provides guidance for appropriate sample handling, screening, and processing to ensure valid analytical results.

Chemistry Techniques, Analytical↗