An Optimized Analytical Method for the Simultaneous Detection of Iodoform,Iodoacetic Acid,and Other Trihalomethanes and Haloacetic Acids in Drinking Water

An optimized method is presented using liquid-liquid extraction and derivatization for the extraction of iodoacetic acid (IAA) and other haloacetic acids (HAA₉) and direct extraction of iodoform (IF) and other trihalomethanes (THM₄) from drinking water, followed by detection by gas chromatography with electron capture detection (GC-ECD). A Doehlert experimental design was performed to determine the optimum conditions for the five most significant factors in the derivatization step: namely, the volume and concentration of acidic methanol (optimized values  = 15%, 1 mL), the volume and concentration of Na₂SO₄ solution (129 g/L, 8.5 mL), and the volume of saturated NaHCO₃ solution (1 mL). Also, derivatization time and temperature were optimized by a two-variable Doehlert design, resulting in the following optimized parameters: an extraction time of 11 minutes for IF and THM₄ and 14 minutes for IAA and HAA₉; mass of anhydrous Na₂SO₄ of 4 g for IF and THM₄ and 16 g for IAA and HAA₉; derivatization time of 160 min and temperature at 40°C. Under optimal conditions, the optimized procedure achieves excellent linearity (R² ranges 0.9990–0.9998), low detection limits (0.0008–0.2 µg/L), low quantification limits (0.008–0.4 µg/L), and good recovery (86.6%–106.3%). Intra- and inter-day precision were less than 8.9% and 8.8%, respectively. The method was validated by applying it to the analysis of raw, flocculated, settled, and finished waters collected from a water treatment plant in China.     

Comparison of DNA damage in human-derived hepatoma line (HepG2) exposed to the fifteen drinking water disinfection byproducts using the single cell gel electrophoresis assay

Disinfection of drinking water reduces pathogenic infection, but generates disinfection by-products (DBPs) in drinking water. In this study, the effect of fifteen DBPs on DNA damage in human-derived hepatoma line (HepG2) was investigated by the single cell gel electrophoresis (SCGE) assay. These fifteen DBPs are: four trihalomethanes (THMs), six haloacetic acides (HAAs), three haloacetonitriles (HANs), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), and chloral hydrate (CH). Based on the minimal effective concentration (MEC) at which DBPs induced significant increase in olive tail moment (OTM), the rank order of DNA-damaging potency is: bromodichloromethane (BDCM)>dibromochloromethane (DBCM)>tribromomethane (TBM)>trichloromethane (TCM) of the four THMs; iodoacetic acid (IA)>bromoacetic acid (BA)>dibromoacetic acid (DBA)>dichloracetic acid (DCA)>trichloroacetic acid (TCA) of the five HAAs; dibromoacetonitrile (DBN)approximately dichloroacetonitrile (DCN)>trichloroacetonitrile (TCN) of the three HANs. The DNA damaging potency of MX and CH is similar to TCA and DCA, respectively. IA is the most genotoxic DBP in the fifteen DBPs, followed by BA. Chloroacetic acid (CA) is not genotoxic in this assay. Our findings indicated that HepG2/SCGE is a sensitive tool to evaluate the genotoxicity of DBPs and iodinated DBPs are more genotoxic than brominated DBPs, but chlorinated DBPs are less genotoxic than brominated DBPs.     

Predicting chlorine decay and THM formation in water supply systems

In 1976, the US Environmental Protection Agency (USEPA) published the results of a national survey that showed that chloroform and other trihalomethanes (THMs) were ubiquitous in chlorinated drinking water. Also in 1976, the US National Cancer Institute published results linking chloroform to cancer in laboratory animals, thus giving rise to an important public health issue. Although numerous disinfection by-products (DBPs) have been reported in the literature since that time, with more than 700 confirmed species to date, only a small number have been addressed in either quantitative or health effects studies. The DBPs that have been quantified in drinking water are generally present at low to mid μg/l levels or below. Approximately 50% of the total organic halide (TOX) formed during the chlorination of drinking water and more than 50% of the assimilable organic carbon (AOC) formed during ozonation of drinking water is still not accounted for and little is known about the potential toxicity of many of the vast number of DBPs present in drinking water. The presence of free chlorine is a prerequisite to THM formation. Therefore, a robust understanding of the mechanisms of both chlorine decay and THM formation are fundamental to the management of THMs in water supply systems. This paper presents a review of work undertaken to improve our understanding of these key phenomena and highlights areas of vulnerability in our knowledge and so recommends areas of future research.     

DNA methylation levels and long-term trihalomethane exposure in drinking water: an epigenome-wide association study

Trihalomethanes (THM) are undesired disinfection byproducts (DBPs) formed during water treatment. Mice exposed to DBPs showed global DNA hypomethylation and c-myc and c-jun gene-specific hypomethylation, while evidence of epigenetic effects in humans is scarce. We explored the association between lifetime THM exposure and DNA methylation through an epigenome-wide association study. We selected 138 population-based controls from a case-control study of colorectal cancer conducted in Barcelona, Spain, exposed to average lifetime THM levels ≤85 μg/L vs. >85 μg/L (N = 68 and N = 70, respectively). Mean age of participants was 70 years, and 54% were male. Average lifetime THM level in the exposure groups was 64 and 130 µg/L, respectively. DNA was extracted from whole blood and was bisulphite converted to measure DNA methylation levels using the Illumina HumanMethylation450 BeadChip. Data preprocessing was performed using RnBeads. Methylation was compared between exposure groups using empirical Bayes moderated linear regression for CpG sites and Gaussian kernel for CpG regions. ConsensusPathDB was used for gene set enrichment. Statistically significant differences in methylation between exposure groups was found in 140 CpG sites and 30 gene-related regions, after false discovery rate <0.05 and adjustment for age, sex, methylation first principal component, and blood cell proportion. The annotated genes were localized to several cancer pathways. Among them, 29 CpGs had methylation levels associated with THM levels (|Δβ|≥0.05) located in 11 genes associated with cancer in other studies. Our results suggest that THM exposure may affect DNA methylation in genes related to tumors, including colorectal and bladder cancers. Future confirmation studies are required.     

Comparative genotoxicity of nitrosamine drinking water disinfection byproducts in Salmonella and mammalian cells

Nitrosamine water disinfection byproducts (DBPs) are an emerging class of non-halogenated, nitrogen-containing water contaminants. Five nitrosamine DBPs were analyzed for genotoxicity (N-nitrosodimethylamine (NDMA), N-nitrosopiperidine (NPIP), N-nitrosopyrrolidine (NPYR), N-nitrosomorpholine (NMOR) and N-nitrosodiphenylamine (NDPhA). Using Salmonella typhimurium strain YG7108 the descending rank order of mutagenicity was NDMA>NPIP>NMOR>NPYR; NDPhA was not mutagenic. We developed and calibrated an exogenous S9 mix that was highly effective in activating NDMA in Chinese hamster ovary (CHO) cells using the SCGE (Comet) assay. The descending rank order for genotoxicity was NDMA>NPIP>NMOR. NDPhA was genotoxic only at one concentration and NPYR was not genotoxic. The genotoxic potencies in S. typhimurium and CHO cells were highly correlated. Based on their comparative genotoxicity attention should be focused on the generation and occurrence of NDMA, NPIP and NMOR. Current drinking water disinfection processes may need to be modified such that the generation of nitrosamine DBPs is effectively limited in order to protect the environment and the public health.     

Risk of stillbirth in the relation to water disinfection by-products: a population-based case-control study in Taiwan

Background

Few epidemiological studies that have assessed the relation between water disinfection by-products (DBPs) and the risk of stillbirth provide inconsistent results. The objective was to assess the relation between exposure to water disinfection by-products and the risk of stillbirth.

Methods

We conducted a population-based case-control study of 3,289 cases of stillbirth and a random sample of 32,890 control subjects from 396,049 Taiwanese newborns in 2001–2003 using information from the Birth Registry and Waterworks Registry in Taiwan. We compared the risk of stillbirth in four disinfection by-product exposure categories based on the levels of total trihalomethanes (TTHMs) representing high (TTHMs 20+ µg/L), medium (TTHMs 10–19 µg/L), low exposure (TTHMs 5–9 µg/L), and 0–4 µg/L as the reference category. In addition, we conducted a meta-analysis of the results from the present and 5 previous studies focusing on stillbirth.

Findings

In logistic regression analysis adjusting for gender, maternal age, plurality, conception of season and population density of the municipality where the mother lived during pregnancy, the odds ratio (OR) for stillbirth was 1.10 (95% CI 1.00–1.21) for medium exposure and 1.06 (95% 0.96–1.17) for high exposure compared to reference category. In the meta-analysis, the summary odds ratio for stillbirth (1.11, 95% CI: 1.03, 1.19) was consistently elevated.

Conclusions

The present study is consistent with the hypothesis that the risk of stillbirth is related to prenatal exposure to disinfection by-products. This finding on stillbirth is consistent with previous epidemiologic studies, which strengthens the weight of evidence.     

Comparison of Barium and Arsenic Concentrations in Well Drinking Water and in Human Body Samples and a Novel Remediation System for These Elements in Well Drinking Water

Health risk for well drinking water is a worldwide problem. Our recent studies showed increased toxicity by exposure to barium alone (≤700 µg/L) and coexposure to barium (137 µg/L) and arsenic (225 µg/L). The present edition of WHO health-based guidelines for drinking water revised in 2011 has maintained the values of arsenic (10 µg/L) and barium (700 µg/L), but not elements such as manganese, iron and zinc. Nevertheless, there have been very few studies on barium in drinking water and human samples. This study showed significant correlations between levels of arsenic and barium, but not its homologous elements (magnesium, calcium and strontium), in urine, toenail and hair samples obtained from residents of Jessore, Bangladesh. Significant correlation between levels of arsenic and barium in well drinking water and levels in human urine, toenail and hair samples were also observed. Based on these results, a high-performance and low-cost adsorbent composed of a hydrotalcite-like compound for barium and arsenic was developed. The adsorbent reduced levels of barium and arsenic from well water in Bangladesh and Vietnam to <7 µg/L within 1 min. Thus, we have showed levels of arsenic and barium in humans and propose a novel remediation system.     

Artificial Sweeteners in a Large Canadian River Reflect Human Consumption in the Watershed

Artificial sweeteners have been widely incorporated in human food products for aid in weight loss regimes, dental health protection and dietary control of diabetes. Some of these widely used compounds can pass non-degraded through wastewater treatment systems and are subsequently discharged to groundwater and surface waters. Measurements of artificial sweeteners in rivers used for drinking water production are scarce. In order to determine the riverine concentrations of artificial sweeteners and their usefulness as a tracer of wastewater at the scale of an entire watershed, we analyzed samples from 23 sites along the entire length of the Grand River, a large river in Southern Ontario, Canada, that is impacted by agricultural activities and urban centres. Municipal water from household taps was also sampled from several cities within the Grand River Watershed. Cyclamate, saccharin, sucralose, and acesulfame were found in elevated concentrations despite high rates of biological activity, large daily cycles in dissolved oxygen and shallow river depth. The maximum concentrations that we measured for sucralose (21 µg/L), cyclamate (0.88 µg/L), and saccharin (7.2 µg/L) are the highest reported concentrations of these compounds in surface waters to date anywhere in the world. Acesulfame persists at concentrations that are up to several orders of magnitude above the detection limit over a distance of 300 km and it behaves conservatively in the river, recording the wastewater contribution from the cumulative population in the basin. Acesulfame is a reliable wastewater effluent tracer in rivers. Furthermore, it can be used to assess rates of nutrient assimilation, track wastewater plume dilution, separate human and animal waste contributions and determine the relative persistence of emerging contaminants in impacted watersheds where multiple sources confound the usefulness of other tracers. The effects of artificial sweeteners on aquatic biota in rivers and in the downstream Great Lakes are largely unknown.     

Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: a review and roadmap for research

Disinfection by-products (DBPs) are formed when disinfectants (chlorine, ozone, chlorine dioxide, or chloramines) react with naturally occurring organic matter, anthropogenic contaminants, bromide, and iodide during the production of drinking water. Here we review 30 years of research on the occurrence, genotoxicity, and carcinogenicity of 85 DBPs, 11 of which are currently regulated by the U.S., and 74 of which are considered emerging DBPs due to their moderate occurrence levels and/or toxicological properties. These 74 include halonitromethanes, iodo-acids and other unregulated halo-acids, iodo-trihalomethanes (THMs), and other unregulated halomethanes, halofuranones (MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] and brominated MX DBPs), haloamides, haloacetonitriles, tribromopyrrole, aldehydes, and N-nitrosodimethylamine (NDMA) and other nitrosamines. Alternative disinfection practices result in drinking water from which extracted organic material is less mutagenic than extracts of chlorinated water. However, the levels of many emerging DBPs are increased by alternative disinfectants (primarily ozone or chloramines) compared to chlorination, and many emerging DBPs are more genotoxic than some of the regulated DBPs. Our analysis identified three categories of DBPs of particular interest. Category 1 contains eight DBPs with some or all of the toxicologic characteristics of human carcinogens: four regulated (bromodichloromethane, dichloroacetic acid, dibromoacetic acid, and bromate) and four unregulated DBPs (formaldehyde, acetaldehyde, MX, and NDMA). Categories 2 and 3 contain 43 emerging DBPs that are present at moderate levels (sub- to low-mug/L): category 2 contains 29 of these that are genotoxic (including chloral hydrate and chloroacetaldehyde, which are also a rodent carcinogens); category 3 contains the remaining 14 for which little or no toxicological data are available. In general, the brominated DBPs are both more genotoxic and carcinogenic than are chlorinated compounds, and iodinated DBPs were the most genotoxic of all but have not been tested for carcinogenicity. There were toxicological data gaps for even some of the 11 regulated DBPs, as well as for most of the 74 emerging DBPs. A systematic assessment of DBPs for genotoxicity has been performed for approximately 60 DBPs for DNA damage in mammalian cells and 16 for mutagenicity in Salmonella. A recent epidemiologic study found that much of the risk for bladder cancer associated with drinking water was associated with three factors: THM levels, showering/bathing/swimming (i.e., dermal/inhalation exposure), and genotype (having the GSTT1-1 gene). This finding, along with mechanistic studies, highlights the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer. More than 50% of the total organic halogen (TOX) formed by chlorination and more than 50% of the assimilable organic carbon (AOC) formed by ozonation has not been identified chemically. The potential interactions among the 600 identified DBPs in the complex mixture of drinking water to which we are exposed by various routes is not reflected in any of the toxicology studies of individual DBPs. The categories of DBPs described here, the identified data gaps, and the emerging role of dermal/inhalation exposure provide guidance for drinking water and public health research.     

Respiratory Function and Changes in Lung Epithelium Biomarkers after a Short-Training Intervention in Chlorinated vs. Ozone Indoor Pools

Background

Swimming in indoor pools treated with combined chemical treatments (e.g. ozone) may reduce direct exposure to disinfection byproducts and thus have less negative effects on respiratory function compared to chlorinated pools. The aim of this study is to analyze the effects of a short-term training intervention on respiratory function and lung epithelial damage in adults exercising in indoor swimming pool waters treated with different disinfection methods (chlorine vs. ozone with bromine).

Methods

Lung permeability biomakers [surfactant protein D (SP-D) and Clara cell secretory protein (CC16) in plasma] and forced expiratory volumes and flow (FEV1, FVC and FEF_25–75) were measured in 39 healthy adults. Thirteen participants swam during 20 sessions in a chlorinated pool (CP), 13 performed and equivolumic intervention in an ozone pool (OP) and 13 were included in a control group (CG) without exposition.

Results

Median plasma CC16 levels increased in CP swimmers (4.27±3.29 and 6.62±5.51 µg/L, p = 0.01, pre and post intervention respectively) while no significant changes in OP and CG participants were found. No significant changes in median plasma SP-D levels were found in any of the groups after the training period. FVC increased in OP (4.26±0.86 and 4.43±0.92 L, p<0.01) and CP swimmers (4.25±0.86 and 4.35±0.85 L, p<0.01). FEV1 only increased in OP swimmers (3.50±0.65 and 3.59±0.67, p = 0.02) and FEF_25–75 decreased in CP swimmers (3.70±0.87 and 3.37±0.67, p = 0.02).

Conclusion

Despite lung function being similar in both groups, a higher lung permeability in CP compared to OP swimmers was found after a short-term swimming program. Combined chemical treatments for swimming pools such as ozone seem to have less impact on lung epithelial of swimmers compared to chlorinated treated pools.     

Establishment of an efficient and rapid method of multiple shoot regeneration and a comparative phenolics profile in in vitro and greenhouse-grown plants of psophocarpus tetragonolobus (L.) DC

An in vitro method of multiple shoot induction and plant regeneration in Psophocarpus tetragonolobus (L.) DC was developed. Cotyledons, hypocotyls, epicotyls, internodal and young seedling leaves were used as explants. MS media supplemented with various concentrations of either thidiazuron (TDZ) or N6-benzylaminopurine (BAP) along with NAA or IAA combinations were used to determine their influence on multiple shoot induction. MS media supplemented with TDZ induced direct shoot regeneration when epicotyls and internodal segments were used as explants. TDZ at 3 mg L⁻¹ induced highest rate (89.2 ± 3.28%) of regeneration with (13.4 ± 2.04) shoots per explant. MS media supplemented with BAP in combination with NAA or IAA induced callus mediated regeneration when cotyledons and hypocotyls were used as explants. BAP (2.5 mg L⁻¹) and IAA (0.2 mg L⁻¹) induced highest rate (100 ± 2.66%) of regeneration with (23.2 ± 2.66) shoots per explant. Mature plants produced from regenerated shoots were transferred successfully to the greenhouse. In a comparative study, the phenolics contents of various parts of greenhouse-grown plants with that of in vitro-raised plants showed significant variations.     

Effects of Source Water Quality on Chlorine Inactivation of Adenovirus,Coxsackievirus, Echovirus,and Murine Norovirus

More information is needed on the disinfection efficacy of chlorine for viruses in source water. In this study, chlorine disinfection efficacy was investigated for USEPA Contaminant Candidate List viruses coxsackievirus B5 (CVB5), echovirus 1 (E1), murine norovirus (MNV), and human adenovirus 2 (HAdV2) in one untreated groundwater source and two partially treated surface waters. Disinfection experiments using pH 7 and 8 source water were carried out in duplicate, using 0.2 and 1 mg/liter free chlorine at 5 and 15°C. The efficiency factor Hom (EFH) model was used to calculate disinfectant concentration × contact time (CT) values (mg·min/liter) required to achieve 2-, 3-, and 4-log₁₀ reductions in viral titers. In all water types, chlorine disinfection was most effective for MNV, with 3-log₁₀ CT values at 5°C ranging from ≤0.020 to 0.034. Chlorine disinfection was least effective for CVB5 in all water types, with 3-log₁₀ CT values at 5°C ranging from 2.3 to 7.9. Overall, disinfection proceeded faster at 15°C and pH 7 for all water types. Inactivation of the study viruses was significantly different between water types, but no single source water had consistently different inactivation rates than another. CT values for CVB5 in one type of source water exceeded the recommended CT values set forth by USEPA''s Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems using Surface Water Sources. The results of this study demonstrate that water quality plays a substantial role in the inactivation of viruses and should be considered when developing chlorination plans.Disinfection processes are critical for the reduction of infectious virus concentrations in source water, because viruses are less efficiently removed by primary treatment of drinking water (e.g., coagulation and filtration) than are other pathogen types of concern (e.g., bacteria and protozoa). Over the years, many disinfection studies have focused on the inactivation of viruses in purified and buffered, demand-free, reagent-grade water (RGW). However, relatively few investigators have examined the impact of water quality during the disinfection process, even though water quality has been found to be a significant factor for inactivation of viruses.Several researchers found that the inactivation rate of poliovirus by free chlorine increased as the ionic concentration of water increased. In one study, poliovirus 1 was inactivated three times faster in boric acid buffer than in purified water (3). In addition, several investigators found that when the ionic content of buffered water was raised by the addition of NaCl or KCl, poliovirus 1 was inactivated two to four times faster than in the buffered water alone (2, 16, 17). In another study, poliovirus 1 was inactivated 10 times more rapidly in drinking water than in purified water (4).Studies conducted with natural waters have demonstrated both increased and decreased disinfection efficacy of chlorine in these waters compared to purified or buffered waters. In a study comparing chlorine disinfection in purified water and Potomac estuarine water, coxsackievirus A9 was inactivated more rapidly in the source water. The remaining study viruses (coxsackievirus B1, echovirus 7, adenovirus 3, poliovirus 1, and reovirus 3) were all inactivated more slowly in the source water (13). Bacteriophage MS2 was inactivated more slowly by free chlorine in two types of surface water than in buffered, demand-free water. However, there was no difference between the inactivation rates of this virus in the buffered water and groundwater (10). In another study, both feline calicivirus and adenovirus 40 were inactivated more slowly in treated groundwater than in buffered, demand-free water (21).The United States Environmental Protection Agency''s (USEPA) Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems using Surface Water Sources (Guidance Manual) recommends disinfectant concentration × contact time (CT) values of 4, 6, and 8 to achieve 2-, 3-, and 4-log₁₀ inactivation, respectively, with chlorine at 5°C and pH 6 to 9 (23). These CT values, which incorporate a safety factor of 3, were obtained from inactivation experiments conducted with monodispersed hepatitis A virus (HAV) in buffered, demand-free water. As water quality can significantly affect the disinfection efficacy of chlorine, it is unclear whether these CT value recommendations are sufficient for inactivation of viruses in source water. More information is needed to systematically examine the role of water quality in chlorine disinfection of viruses.The objective of the present study was to examine the disinfection efficacy of free chlorine on selected viruses from USEPA''s Contaminant Candidate List (CCL) (22) in one untreated and two partially treated source waters from distinct geographical regions. By comparing the efficacy of chlorine disinfection in the source water types to disinfection in buffered, chlorine-demand-free RGW (7), the impact of water quality could be examined. The four representative CCL viruses selected for this study included human adenovirus 2 (HAdV2), echovirus 1 (E1), coxsackievirus B5 (CVB5), and murine norovirus (MNV), a surrogate for human norovirus (22). The viruses were selected because they were previously found to be the least effectively inactivated viruses of their type in RGW (6). Disinfection experiments were carried out in duplicate in pH 7 and 8 source water at 5 and 15°C using 0.2 and 1 mg/liter free chlorine. Inactivation curves were plotted using Microsoft Excel, and CT values were calculated using the efficiency factor Hom (EFH) model (9).     

Determination of haloacetic acids in human urine by headspace gas chromatography–mass spectrometry

Haloacetic acids (HAAs) are water disinfection byproducts (DBPs) formed by the reaction of chlorine oxidizing compounds with natural organic matter in water containing bromine. HAAs are second to trihalomethanes as the most commonly detected DBPs in surface drinking water and swimming pools. After oral exposure (drinking, showering, bathing and swimming), HAAs are rapidly absorbed from the gastrointestinal tract and excreted in urine. Typical methods used to determine these compounds in urine (mainly from rodents) only deal with one or two HAAs and their sensitivity is inadequate to determine HAA levels in human urine, even those manual sample preparation protocols which are complex, costly, and neither handy nor amenable to automation. In the present communication, we report on a sensitive and straightforward method to determine the nine HAAs in human urine using static headspace (HS) coupled with GC–MS. Important parameters controlling derivatisation and HS extraction were optimised to obtain the highest sensitivity: 120 μl of dimethylsulphate and 100 μl of tetrabutylammonium hydrogen sulphate (derivatisation regents) were selected, along with an excess of Na₂SO₄ (6 g per 12 ml of urine), an oven temperature of 70 °C and an equilibration time of 20 min. The method developed renders an efficient tool for the precise and sensitive determination of the nine HAAs in human urine (RSDs ranging from 6 to 11%, whereas LODs ranged from 0.01 to 0.1 μg/l). The method was applied in the determination of HAAs in urine from swimmers in an indoor swimming pool, as well as in that of non-swimmers. HAAs were not detected in the urine samples from non-swimmers and those of volunteers before their swims; therefore, the concentrations found after exposure were directly related to the swimming activity. The amounts of MCAA, DCAA and TCAA excreted from all swimmers are related to the highest levels in the swimming pool water.     

Solar Disinfection of Viruses in Polyethylene Terephthalate Bottles

Solar disinfection (SODIS) of drinking water in polyethylene terephthalate (PET) bottles is a simple, efficient point-of-use technique for the inactivation of many bacterial pathogens. In contrast, the efficiency of SODIS against viruses is not well known. In this work, we studied the inactivation of bacteriophages (MS2 and ϕX174) and human viruses (echovirus 11 and adenovirus type 2) by SODIS. We conducted experiments in PET bottles exposed to (simulated) sunlight at different temperatures (15, 22, 26, and 40°C) and in water sources of diverse compositions and origins (India and Switzerland). Good inactivation of MS2 (>6-log inactivation after exposure to a total fluence of 1.34 kJ/cm²) was achieved in Swiss tap water at 22°C, while less-efficient inactivation was observed in Indian waters and for echovirus (1.5-log inactivation at the same fluence). The DNA viruses studied, ϕX174 and adenovirus, were resistant to SODIS, and the inactivation observed was equivalent to that occurring in the dark. High temperatures enhanced MS2 inactivation substantially; at 40°C, 3-log inactivation was achieved in Swiss tap water after exposure to a fluence of only 0.18 kJ/cm². Overall, our findings demonstrate that SODIS may reduce the load of single-stranded RNA (ssRNA) viruses, such as echoviruses, particularly at high temperatures and in photoreactive matrices. In contrast, complementary measures may be needed to ensure efficient inactivation during SODIS of DNA viruses resistant to oxidation.     

Physiology of Hormone Autonomous Tissue Lines Derived From Radiation-Induced Tumors of Arabidopsis thaliana

γ-Radiation-induced tumors of Arabidopsis thaliana L. have been produced as a novel approach to isolation of genes that regulate plant development. Tumors excised from irradiated plants are hormone autonomous in culture and have been maintained on hormone-free medium for up to 4 years. Five tumor tissue lines having different morphologies and growth rates were analyzed for auxin, cytokinin, and 1-aminocyclopropane-1-carboxylic acid (ACC) content, ethylene production, and response to exogenous growth regulators. Normal tissues and two crown gall tissue lines were analyzed for comparison. Rosettes and whole seedlings each contained approximately 30 nanograms· (gram fresh weight)⁻¹ free indoleacetic acid (IAA), 150 nanograms· (gram fresh weight)⁻¹ ester-conjugated IAA, and 10 to 20 micrograms· (gram fresh weight)⁻¹ amide-conjugated IAA. The crown gall lines contained similar amounts of free and ester-conjugated IAA but less amide conjugates. Whereas three of the radiation-induced tumor lines had IAA profiles similar to normal tissues, one line had 10- to 100-fold more free IAA and three- to 10-fold less amide-conjugated IAA. The fifth line had normal free IAA levels but more conjugated IAA than control tissues. Whole seedlings contained approximately 2 nanograms· (gram fresh weight)⁻¹ of both zeatin riboside and isopentenyladenosine. The crown gall lines had 100- to 1000-fold higher levels of each cytokinin. In contrast, the three radiation-induced tumor lines analyzed contained cytokinin levels similar to the control tissue. The radiation-induced tumor tissues produced very little ethylene, although each contained relatively high levels of ACC. Normal callus contained similar amounts of ACC but produced several times more ethylene than the radiation-induced tumor lines. Each of the radiation-induced tumor tissues displayed a unique set of responses to exogenously supplied growth regulators. Only one tumor line showed the same response as normal callus to both auxin and cytokinin feeding. In some cases, one or more tumor lines showed increased sensitivity to certain growth substances. In other cases, growth regulator feeding had no significant effect on tumor tissue growth. Morphology of the radiation-induced tumor tissues generally did not correlate with auxin to cytokinin ratio in the expected manner. The results suggest that a different primary genetic event led to the formation of each tumor and that growth and differentiation in the tumor tissue lines are uncoupled from the normal hormonal controls.     

Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions

Ozone is widely used to disinfect drinking water and wastewater due to its strong biocidal oxidizing properties. Recently, it was reported that hydroxyl radicals (^·OH), resulting from ozone decomposition, play a significant role in microbial inactivation when Bacillus subtilis endospores were used as the test microorganisms in pH controlled distilled water. However, it is not yet known how natural organic matter (NOM), which is ubiquitous in sources of drinking water, affects this process of disinfection by ozone-initiated radical reactions. Two types of water matrix were considered for this study. One is water containing humic acid, which is commercially available. The other is water from the Han River. This study reported that hydroxyl radicals, initiated by the ozone chain reaction, were significantly effective at B. subtilis endospore inactivation in water containing NOM, as well as in pH-controlled distilled water. The type of NOM and the pH have a considerable effect on the percentage of disinfection by hydroxyl radicals, which ranged from 20 to 50%. In addition, the theoretical T value of hydroxyl radicals for 2-log B. subtilis removal was estimated to be about 2.4 × 10⁴ times smaller than that of ozone, assuming that there is no synergistic activity between ozone and hydroxyl radicals.     

Levels of Endogenous Indole-3-acetic Acid in Achenes of Rosa rugosa during Dormancy Release and Germination

Indole-3-acetic acid (IAA) in highly purified extracts of rose achenes (Rosa rugosa var rubra) was quantified by means of ion-pair reversephase high performance liquid chromatography with spectrofluorimetric detection. Changes in IAA content were determined during a 14-week 4°C stratification, which leads to dormancy breakage, and during subsequent germination at 17°C. IAA was also determined in achenes stratified in parallel at 17°C, which does not induce release from dormancy. IAA decreased during the first 2 weeks of stratification both at 4°C and at 17°C. IAA remained low during the remaining 12 weeks of stratification at 4°C, whereas it continued to decrease in achenes kept at 17°C. An immediate increase in IAA during germination was followed by transients in the IAA level. The results suggest that IAA is without a regulating role in dormancy release although it seems to be involved in the germination process.     

Implications of Using Steady-State Conditions in Estimating Dermal Uptake of Volatile Compounds in Municipal Drinking Water: An Example of THMs

Dermal exposure to volatile compounds (VC) in municipal water while showering is typically estimated using a steady-state condition between VC in water impacting on skin and skin exposed to water. The lag times to achieve steady-state between VC and skin can vary in the range of 7.5–218.3 min, while shower duration is often less than these values. Estimates of dermal exposure to VC using steady-state while showering may misinterpret exposure. This study developed models and estimated exposure to some disinfection byproducts (DBPs) through dermal pathway by considering lag times while showering. Dermal uptakes of VC were compared using different approaches. In the proposed approach, uptakes of trihalomethanes were estimated between 9.55 × 10^?10–1.43 × 10^?8 mg/cm² of skin during the lag times from exposure to water with trihalomethanes of 50 μg/L. These values were higher than the steady-state estimates (1.37 × 10^?10–4.34 × 10^?9 mg/cm²), and lower than the average exposure analysis (4.12 × 10^-8–1.93 × 10^?6 mg/cm²). Using the Drinking Water Surveillance Program data in Ontario, chronic daily intakes of trihalomethanes were estimated to be 9.40 × 10^?7 (1.85 × 10^?7–1.65 × 10^?6), 3.89 × 10^?6 (7.11 × 10^?7–2.33 × 10^?5), and 1.40 × 10^?6 (4.0 × 10^?7–1.77 × 10^?6) mg/kg/day in Toronto, Ottawa, and Hamilton, respectively. The findings can be useful in understanding THMs exposure and risk through dermal pathway.     

Ethylene-induced leaf abscission in cotton seedlings : the physiological bases for age-dependent differences in sensitivity

The speed of ethylene-induced leaf abscission in cotton (Gossypium hirsutum L. cv LG-102) seedlings is dependent on leaf position (i.e. physiological age). Fumigation of intact seedlings for 18 hours with 10 microliters per liter of ethylene resulted in 40% abscission of the still-expanding third true (3°) leaves but had no effect on the fully expanded first true (1°) leaves. After 42 hours of fumigation with 50 microliters per liter of ethylene, total abscission of the 3° leaves occurred while <50% abscission of the 1° leaves was observed. On a leaf basis, endogenous levels of free IAA in 1° leaves were approximately twice those of 3° leaves. Free IAA levels were reduced equally (approximately 55%) in both leaf types after 18 hours of ethylene (10 microliters per liter) treatment. Ethylene treatment of intact seedlings inhibited the basipetal movement of [¹⁴C]IAA in petiole segments isolated from both leaf types in a dose-dependent manner. The auxin transport inhibitor N-1-naphthylphthalamic acid increased the rate and extent of ethylene-induced leaf abscission at both leaf positions but did not alter the relative pattern of abscission. Abscission-zone explants prepared from 3° leaves abscised faster than 1° leaf explants when exposed to ethylene. Ethyleneinduced abscission of 3° explants was not appreciably inhibited by exogenous IAA while 1° explants exhibited a pronounced and protracted inhibition. The synthetic auxins 2,4-D and 1-naphthaleneacetic acid completely inhibited ethylene-induced abscission of both 1° and 3° explants for 40 hours. It is proposed that the differential abscission response of cotton seedling leaves is primarily a result of the limited abscission-inhibiting effects of IAA in the abscission zone of the younger leaves.     

Long-Term Inactivation Study of Three Enteroviruses in Artificial Surface and Groundwaters, Using PCR and Cell Culture

Since the transmission of pathogenic viruses via water is indistinguishable from the transmission via other routes and since the levels in drinking water, although significant for health, may be too low for detection, quantitative viral risk assessment is a useful tool for assessing disease risk due to consumption of drinking water. Quantitative viral risk assessment requires information concerning the ability of viruses detected in drinking water to infect their host. To obtain insight into the infectivity of viruses in relation to the presence of virus genomes, inactivation of three different enteroviruses in artificial ground and surface waters under different controlled pH, temperature, and salt conditions was studied by using both PCR and cell culture over time. In salt-peptone medium, the estimated ratio of RNA genomes to infectious poliovirus 1 in freshly prepared suspensions was about 10⁰. At 4°C this ratio was 10³ after 600 days, and at 22°C it was 10⁴ after 200 days. For poliovirus 1 and 2 the RNA/infectious virus ratio was higher in artificial groundwater than in artificial surface water, but this was not the case for coxsackievirus B4. When molecular detection is used for virus enumeration, it is important that the fraction of infectious virus (based on all virus genomes detected) decays with time, especially at temperatures near 22°C.