Soil self-cleaning capacity: Removal of organic compounds during sub-surface irrigation with sewage effluent.

Globally, the reuse of treated sewage effluent for irrigation purposes is increasingly encouraged as a practical solution against the mismatch between the demand for and availability of freshwater resources. The reuse of sewage effluent for sub-surface irrigation (SSI) in agriculture serves the dual purpose of supplying water to crops and diminishing emissions of contaminants of emerging concern (CoECs) into surface water. To investigate such reuse, in a real scale cropland with SSI using sewage effluent, from September 2017 to March 2019 including the extremely dry year 2018, residues were followed of 133 CoECs as related to their physicochemical properties and quantified by liquid chromatography coupled to high-resolution mass spectrometry. Of the 133 target CoECs, 89 were retrieved in the field, most non-detect CoECs have low persistency. During the growing season with sub-surface irrigation, CoECs spread to the shallow groundwater and rhizosphere. Significantly lower concentrations are found between infiltration pipes as compared to directly next to the pipes in shallow groundwater for all persistency-mobility classes. CoECs belonging to the class pm (low persistency and low mobility) or class PM (high persistency and high mobility) class show no change amongst their removal in the rhizosphere and groundwater in a dry versus normal year. CoECs belonging to the class pM (low persistency and high mobility) show high seasonal dynamics in the rhizosphere and shallow groundwater, indicating that these CoECs break down. CoECs of the class Pm (high persistency and low mobility) only significantly build up in the rhizosphere next to infiltration pipes. Climatic conditions with dry summers and precipitation surplus and drainage in winter strongly affect the fate of CoECs. During the dry summer of 2018 infiltrated effluent is hardly diluted, resulting in significantly higher concentrations for the CoECs belonging to the classes pM and Pm. After the extremely dry year of 2018, cumulative concentrations are still significantly higher, while after a normal year during winter precipitation surplus removes CoECs. For all persistency-mobility classes in the shallow groundwater between the pipes, we find significant removal efficiencies. For the rhizosphere between the pipes, we find the same except for Pm. Next to the pipes however we find no significant removal for all classes in both the rhizosphere and shallow groundwater and even significant accumulation for Pm. For this group of persistent moderately hydrophobic CoECs risk characterization ratio's were calculated for the period of time with the highest normalized concentration. None of the single-chemical RCRs are above one and the ΣRCR is also far below one, implying sufficiently safe ambient exposures. Overall the deeper groundwater (7.0-11.8 m below soil surface) has the lowest response to the sub-surface irrigation for all persistency-mobility. When adopting a SSI STP effluent reuse system care must be taken to monitor the CoECs that are (moderately) hydrophobic as these can build up in the SSI system. For the deeper groundwater and for the discharge to the surface water, we find significant removal for the pM and the PM class but not for other classes. In conclusion, relatively high removal efficiencies are shown benefiting the surface waters that would otherwise receive the STP effluent directly.

A systems approach to understand microplastic occurrence and variability in Dutch riverine surface waters.

Assessment methods on data quality and environmental variability are lacking for microplastics (MP). Here we assess occurrence and variability of MP number concentrations in two Dutch rivers. Strict QA/QC procedures were applied to identify MP using Fourier-transform infrared (FTIR) microscopy followed by state of the art automated image analysis. For a series of randomly selected, yet ever smaller subareas of filters, we assessed how accurately MP numbers and polymer types are represented during partial filter analysis. Levels of uncertainty were acceptable when analysing 50% of a filter during chemical mapping, and when identifying at least a subset of 50 individual particles with attenuated total reflection (ATR)-FTIR. Applying these guidelines, MP number concentrations between 67 and 11532 MP m-3 were detected in Dutch riverine surface waters. Spatial differences caused MP number concentrations to vary by two orders of magnitude. Temporal differences were lower and induced a maximum variation of one order of magnitude. In total, 26 polymer types were identified, the most common were polyethylene (23%), polypropylene (19.7%) and ethylene propylene diene monomer rubber (18.3%). The highest diversity of polymer types was found for small MPs, whereas MP larger than 1 mm was scarce and almost exclusively made of polyethylene or polypropylene. Virtually all sampling locations revealed MP number concentrations that are considerably below known effect thresholds for anticipated adverse ecological effects.

Advancing environmental toxicology through chemical dosimetry: external exposures versus tissue residues.

The tissue residue dose concept has been used, although in a limited manner, in environmental toxicology for more than 100 y. This review outlines the history of this approach and the technical background for organic chemicals and metals. Although the toxicity of both can be explained in tissue residue terms, the relationship between external exposure concentration, body and/or tissues dose surrogates, and the effective internal dose at the sites of toxic action tends to be more complex for metals. Various issues and current limitations related to research and regulatory applications are also examined. It is clear that the tissue residue approach (TRA) should be an integral component in future efforts to enhance the generation, understanding, and utility of toxicity testing data, both in the laboratory and in the field. To accomplish these goals, several key areas need to be addressed: 1) development of a risk-based interpretive framework linking toxicology and ecology at multiple levels of biological organization and incorporating organism-based dose metrics; 2) a broadly applicable, generally accepted classification scheme for modes/mechanisms of toxic action with explicit consideration of residue information to improve both single chemical and mixture toxicity data interpretation and regulatory risk assessment; 3) toxicity testing protocols updated to ensure collection of adequate residue information, along with toxicokinetics and toxicodynamics information, based on explicitly defined toxicological models accompanied by toxicological model validation; 4) continued development of residue-effect databases is needed ensure their ongoing utility; and 5) regulatory guidance incorporating residue-based testing and interpretation approaches, essential in various jurisdictions.

Distribution, speciation, and bioavailability of lanthanides in the Rhine-Meuse estuary, The Netherlands.

Changing environmental conditions may influence the fate and bioavailability of lanthanides (part of the rare earth elements [Ln]) in estuaries. The aim of this study was to quantify the variation in estuarine lanthanide solid/water distribution, speciation, and bioaccumulation. The latter was studied in the amphipod Corophium volutator under field and laboratory conditions. Calculations with the chemical equilibrium model MINEQL+ indicate that dissolved lanthanides are complexed mainly to carbonates and dissolved organic matter. In the water phase, the relative abundance of the free ion, LnCO3, and humic complexes decreases from lanthanum to lutetium, whereas the relative abundance of Ln(CO3)2 increases. Cerium and europium anomalies were found in the water. Europium anomalies were also found in some biota. The biota sediment accumulation factors (BSAFs) decreased across the series from lanthanum to lutetium. Regression analysis revealed that alkalinity correlated negatively with lanthanide uptake. This suggests that increasing complexation reduced bioavailability under the prevailing conditions. The BSAFs did not depend on salinity or pH, which may simplify sediment-quality criteria for fresh versus saline waters. Field BSAFs were significantly lower than laboratory values for the same sediments, which is explained by adaptation of the organisms to lanthanides.

Environmental risk limits for two phthalates, with special emphasis on endocrine disruptive properties.

Environmental risk limits (ERLs) are derived for di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP). The ERLs are derived using data on (eco)toxicology and environmental chemistry. Endpoints used are survival, growth, and reproduction. The resulting ERLs in water are 10 and 0.19 microg/L for DBP and DEHP, respectively; in fresh soil and sediment with 10% organic matter the derived ERLs are respectively 0.7 and 1 mg/kg fresh wt. In The Netherlands, measured concentrations of DBP are seldom above the ERLs, while reported concentrations for DEHP are 3 to 20 times higher than the ERL. As phthalates as a group are commonly mentioned as chemicals with possible endocrine disruptive effects, in vivo and in vitro tests for a series of phthalates with endpoints related to endocrine disruption are reviewed. In vitro and in vivo tests give a similar distinction between phthalates that can or cannot act as endocrine disrupters. The significance of these tests for the derivation of ERLs is discussed. It is concluded that the ERLs derived will give sufficient protection against endocrine disruptive effects. There is no need to include additional data for DBP and DEHP, related to endpoints other than survival, growth, or reproduction, in the derivation of ERLs.

Lipid content and time-to-death-dependent lethal body burdens of naphthalene and 1,2,4-trichlorobenzene in fathead minnow (Pimephales promelas).

For naphthalene (NAPH) and 1,2,4-trichlorobenzene (TCBz), lethal body burdens (LBB) of 8 +/- 3.1 mmol/kg wet wt (ww) and 14 +/- 4.5 mmol/kg (ww), respectively, were determined in fathead minnow (Pimephales promelas). LBBs of both compounds were found to increase with increasing lipid content and time-to-death of fish within the same aquarium. The correlation with time-to-death suggests that besides lipid content at least one other factor causes intraspecies variation in LBBs. When intraspecies variation is excluded by comparing mean LBBs from different aquaria and exposure regimes, LBBs still vary with time-to-death. In contrast to the situation within one aquarium, between different aquaria and exposure regimes often a decrease in LBB with time-to-death is found. The present study and others indicate that LBBs can vary with time-to-death. Therefore, a time-independent LBB cannot be assumed.

Use of the lethal body burden in the evaluation of mixture toxicity.

In many mixtures of xenobiotics in the field situation, narcosis is the predominant mechanism of toxic action. Earlier studies have found that narcotic chemicals are additive based on exposure concentration. In this study it is revealed that the narcotic chemicals 1,2- and 1,4-dichlorobenzene are additive on a lethal body burden level. This applicability of the lethal body burden in risk assessment of mixtures of unknown chemicals is discussed, and it is compared with other methods of managing mixtures of unknown chemical composition.

Use of lethal body burdens to indicate species differences in susceptibility to narcotic toxicants.

Lethal body burdens (LBB) for 1,2- and 1,4-dihalogenated benzenes (F, Cl or Br) are determined in rainbow trout of two age-classes. LBBs range from 0.3 to 2.4 mmol/kg. There are no significant differences between the two tested age-classes of rainbow trout. The rainbow trout data are compared to LBBs for 1,2- and 1,4-difluorobenzene in fathead minnow which range from 2.7 to 3.0 mmol/kg, and to LBBs of dichloro- and dibromobenzenes in guppy and fathead minnow [Sijm et al. 1993] which range from 2.7 to 8.0 mmol/kg. Rainbow trout are more susceptible to dihalogenated benzenes than fathead minnow. The LBB can be used as an instrument to examine the intrinsic toxicity of a chemical to a species, and to indicate the susceptibility of a species. Possible reasons for differences in susceptibility among species are discussed.

Narcosis due to environmental pollutants in aquatic organisms: residue-based toxicity, mechanisms, and membrane burdens.

The well-known correlation between the hydrophobicity of narcotic chemicals and the exposure concentration needed to produce an effect indicates that a lipid phase in the aquatic organism is the most likely target. The molar concentration in aquatic organisms at death is found to be approximately constant for different narcotic chemicals, varying from 2 to 8 mmol/kg organism. Because the proportion of lipid is known, the lethal in vivo membrane burden can be calculated to be 40 to 160 mmol/kg lipid. The exact mechanism underlying narcosis is still unknown. However, disturbance by narcotic chemicals in model membrane systems has been investigated, attention having been paid to disturbance of phospholipids and proteins, and of the interaction between the two groups. Model membrane burdens of different chemicals have been shown to be approximately constant for a particular effect. Different effects are found at different membrane concentrations. In the present review, the toxicity of narcotic chemicals to aquatic organisms is discussed, the possible mechanisms underlying narcosis are reviewed, and a comparison is made between membrane burdens that are lethal in vivo and membrane burdens that cause an effect in in vitro systems.

The toxicokinetic behavior of chlorobenzenes in earthworms (Eisenia andrei): experiments in water.

The toxicokinetic behavior of five chlorobenzenes in earthworms (Eisenia andrei) was studied. Because exposure in soil is difficult to control, worms were kept in water. Bioconcentration factors (BCF) were studied in a static test system. The results show that a steady-state concentration in worms is reached within 5 days. BCF values increased with increasing octanol-water partition coefficient (Kow). To determine elimination rate constants (k2), worms were exposed to a mixture of chlorobenzenes for 6 days followed by a depuration period of 21 days. The data of the elimination process are described by one-compartment first order kinetics. Hexachlorobenzene was not eliminated within the observed period. Bioconcentration factors increase and elimination rate constants (k2 values) decrease with increasing log Kow. The resulting BCF and k2 values are comparable with those found in fish studies.

Serological and virological assessment of oral and inactivated poliovirus vaccines in a rural population in Kenya.

A study was carried out in a rural community in Kenya to compare the humoral and intestinal immunity provided by three doses of oral poliovirus vaccine (OPV) and two or three doses of enhanced-potency inactivated poliovirus vaccine (IPV). The immunization series was started at 8-12 weeks of age and the interval between doses was 2 months. In children with low levels of maternal antibodies (i.e., those most at risk), the first dose of either vaccine stimulated antibody response. Children with high levels of maternal antibodies responded to the first dose of OPV, but not to that of IPV. Subsequent doses led to increases in the mean antibody titres with both vaccines. After three doses of OPV, the proportion of children with antibody titres of greater than or equal to 1:8 was 92% for type 1 virus, 98% for type 2, and 90% for type 3. After two doses of IPV the proportion of children with antibody titres of greater than or equal to 1:8 was 94%, 88%, and 97% for type 1, type 2, and type 3, respectively; after three doses of IPV, 100% of children had antibodies greater than or equal to 1:8 for types 1 and 3, and 98% for type 2. Intestinal immunity was tested with a challenge dose of type 1 OPV, but the dose used was too small to detect a significant difference between the vaccines.

Comparison of serum and salivary antibodies in children vaccinated with oral live or parenteral inactivated poliovirus vaccines of different antigen concentrations.

A new antigen-rich inactivated poliovirus vaccine (IPV) in ordinary (IPV1), double (IPV2) and quadruple (IPV4) antigen concentrations was given in 2 doses to 6 and 18 week old Pakistani infants. The immune responses to poliovirus types 1 and 3 were compared to those in infants given three doses of oral poliovirus vaccine (OPV) at 6, 12 and 18 weeks of age. Enzyme-linked immunosorbent assay, ELISA, was used to estimate IgG and IgA in serum and secretory IgA (SIgA) in saliva. Two to three years later, a follow-up of the serum antibody response was carried out in the same infants using a microneutralization test. Serum IgG antibody responses to poliovirus type 1 antigen after two doses of IPV1, IPV2 and IPV4 were not significantly higher than the response after three doses of OPV at 21 weeks of age (p greater than 0.05). The serum IgG responses to poliovirus type 3 were similar to those against type 1 in all the groups. Mean neutralizing antibody titres to poliovirus type 1 was significantly higher in the IPV2 group than the rest of the groups (p less than 0.01). For type 3, these titres were highest but not significantly, in the IPV4 group (p greater than 0.05). This study shows that two doses of a new antigen-rich IPV can give similar immediate serum antibody responses as OPV but higher late responses. SIgA antibodies in saliva were more efficiently induced by OPV after three doses than after 2 doses of IPV (p less than 0.05).

Immunologic memory induced at birth by immunization with inactivated polio vaccine in a reduced schedule.

One hundred forty-one healthy newborns were immunized 24 hours after birth with one dose of inactivated polio vaccine (IPV) of enhanced potency. Following the administration of a second vaccine dose six months later, a considerable proportion of babies responded with neutralizing antibody (NA) to the three poliovirus types. The very rapid occurrence and high antibody titer were indicative of an anamnestic response. Twenty-one infants who still had NA less than 1:4 to one-more poliovirus types after the second vaccine dose responded with very high NA values 7-10 days after a supplementary dose of IPV. It appears that IPV of enhanced potency administered at birth is apt to induce immunologic memory, which should provide the basis for protection against paralytic poliomyelitis in case of exposure to wild poliovirus later in life.

Measles virus fusion protein presented in an immune-stimulating complex (iscom) induces haemolysis-inhibiting and fusion-inhibiting antibodies, virus-specific T cells and protection in mice.

Immune-stimulating complexes (iscoms), which have recently been shown to be highly effective for the antigenic presentation of membrane proteins of viruses, were prepared with affinity-purified fusion (F) protein of measles virus (MV), using an adaptation of the standard method for iscom preparation. Immunization of monkeys with the F iscom preparation induced biologically active anti-F protein antibodies as was shown in haemolysis inhibition and cell-cell fusion inhibition tests. A whole MV iscom preparation, which also contained the haemagglutinin protein, induced not only also haemolysis-inhibiting antibodies, but, in contrast to the F iscom preparation, also haemagglutination-inhibiting and virus-neutralizing antibodies. In addition the F iscom preparation was shown to activate measles virus-specific T cells in mice. This was demonstrated by the generation of an MV-specific delayed type hypersensitivity response in F iscom-immunized animals and by the isolation of T cell clones specific for MV F protein with the T helper phenotype. Vaccination of mice with MV iscom or F iscom protected them from MV-induced fatal encephalopathy. The data concerning the immunogenicity of MV proteins presented in iscoms are discussed in relation to their potential for the development of an inactivated measles vaccine.

Poliomielitis paralitica en Guatemala / Paralytic poliomielytis in Guatemala

Durante la epidemia de poliomielitis paralítica que afectó a Guatemala entre 1982 y 1983, se llevó a cabo un estudio longitudinal de las características clínicas y virológicas de 133 niños con este diagnóstico ingresados en un hospital de la capital. La edad de los pacientes fluctuó entre los cuatro meses y los cinco años. El 68% no habían recibido ninguna dosis de la vacuna oral de poliovirus, mientras que al 6% se les habían administrado tres dosis. En 102 niños se aislaron poliovirus; en 92 de estos casos los virus excretados eran solo del tipo 1; en siete, del tipo 2; en uno, del tipo 3, y en dos niños, de los tipos 1 y 2. Se tomaron 66 cepas círicas para establecer la diferenciación intratípica y se halló que 55 de los 56 virus aislados del tipo 1 y el único del tipo 3 eran virus no análogos al de Sabin, mientras que las nueve cepas del tipo 2 eran análogas al virus de Sabin. Estas observaciones confirman la necesidad de la vacunación durante el primer semestre de vida y que el establecimiento de medidas adecuadas para controlar la transmisión de poliovirus del tipo salvaje produciría una notable disminución de la morbilidad causada por la poliomielitis

Inhibition of measles virus-induced cell-cell fusion with a monoclonal antibody directed against the haemagglutinin.

A neutralizing monoclonal antibody (C26-15) against the haemagglutinin (H protein) of measles virus was generated which caused cell-cell fusion inhibition in cultures of measles virus-infected cells. It was shown that this phenomenon coincided with a down-regulation of the expression of both the H protein and the fusion (F) protein. We also showed cell-cell fusion inhibition with a polyclonal rabbit serum directed against Tween-ether inactivated measles virus, which did not contain biologically active antibodies against the F protein. Cell-cell fusion inhibition caused by anti-H antibodies is distinct from cell-cell fusion inhibition induced by a direct interaction of anti-F antibody with the F protein in the membrane of infected cells. Since both mechanisms may also be involved in the in vivo situation, the exclusive role for the generation of anti-F antibody to prevent virus spread by cell-cell fusion in vivo is questioned. It is speculated that the observed down-regulation of both glycoproteins may lead to a less efficient killing of infected cells by cytotoxic T-lymphocytes, which may constitute an alternative explanation for the insufficient protection after vaccination with an inactivated measles vaccine.

Characterization and fibrin-binding properties of different molecular forms of pro-urokinase from a monkey kidney cell culture.

Culture fluid of a monkey kidney cell culture was harvested every two days, for a two week period, in order to obtain urokinase in the zymogen form. Pro-urokinase was isolated by immunoadsorption chromatography and gel filtered on Sephadex G-150, which resulted in three peaks with pro-urokinase activity. SDS-polyacrylamide gel electrophoresis showed that the first peak contained 55 kd pro-urokinase, aggregated with high molecular weight contaminants, whereas the second and third peaks consisted of almost pure 55 kd and 30 kd pro-urokinase, respectively. The latter form represented a relatively unknown and inactive precursor of low molecular weight urokinase, which was, like 55 kd pro-urokinase, activatable with plasmin. In comparison with tissue-type plasminogen activator, 55 kd and 30 kd pro-urokinase only bound weakly to purified fibrin clots and fibrin-sepharose columns. The extent of binding of the two pro-urokinases and their plasmin-activated forms to fibrin-sepharose decreased in the following order: 55 kd pro-urokinase 30 kd pro-urokinase 55 kd urokinase 30 kd urokinase. These results indicate that the two precursors exhibited stronger binding to fibrin-sepharose than the corresponding active enzymes, and the two 55 kd forms exhibited stronger binding than the corresponding 30 kd forms. This indicates the importance of both the zymogen nature and an intact NH2-terminal part of the molecules for binding to fibrin.