Estimating human toxicity potential of land application of sewage sludge: the effect of modelling choices

Purpose

Many municipalities are facing increasing pressure to adapt solid waste and wastewater management infrastructures in order to better close nutrient cycles. The focus of this study is on the estimation of the human toxicity potential associated with chemical contaminants released upon the application of sewage sludge to agricultural land. More specifically, this study investigated the effect of modelling choices regarding fate and exposure assessment.

Methods

Monitoring data were collected for contaminants present in the sewage sludge from the wastewater treatment plant in Gothenburg and from other municipal wastewater treatment plants in Sweden. Based on these monitoring data, an overall burden of disease was estimated using characterisation factors taken from the USEtox models (versions 1.01 and 2.0). For the exposure through vegetables, an alternative life cycle impact assessment (LCIA) model was developed. The intake fractions thus obtained were used in combination with human health effect factors taken from the USEtox 2.0 database. The model results were compared with the USEtox models, and whether these two versions of the USEtox model provide significantly different results was also examined. The potential relevance of accidental ingestion of sludge was also considered.

Results and discussion

The different LCIA models provided burden of disease estimates that differed from one another for individual contaminants (up to five orders of magnitude). The aggregated burdens of disease (i.e. sum for all contaminants considered in this study) estimated through different model variants, however, were of the same order of magnitude. For both metals and organic contaminants, only a small set of contaminants was found to make significant contributions to the aggregate burden of disease. However, it is uncertain whether the 15 metals and 106 organic contaminants covered by this study are those of greatest health significance of all contaminants potentially present in sewage sludge.

Conclusions and recommendations

The results of this study indicate that the technical information provided by the various approaches to modelling human toxicity in life cycle assessment (LCA) in the context of land application of sewage sludge management is consistent on the whole. However, given the uncertainties associated with the assessment of human toxicity in LCA, it is important to also contemplate the extent to which LCA in general is capable of informing the sewage sludge debate when it comes to human toxicity and possibly also other indicators. Future research could focus on identifying which types of questions of interest in the context of sewage management can be answered by LCA and which cannot.

     

Hemidesmosomal Molecular Changes in Dermatitis Herpetiformis; Decreased Expression of BP230 and Plectin/HD1 in Uninvolved Skin

Recent BP230-knockout experiments with subsequent blistering and recently identified plectin/HD1 mutations in epidermolysis bullosa simplex patients suggest that defective expression of BP230 and plectin/HD1 may predispose to blister formation in human skin. We have studied the expression of the epithelial adhesion complex as well as the basement membrane and anchoring fibril antigens in uninvolved dermatitis herpetiformis skin to find out if alterations can be detected in these structures predisposing to the blister formation typical of the disease. Ten uninvolved dermatitis herpetiformis skin specimens, which all showed clear granular deposits of IgA under the basement membrane in direct immunofluorescence and five normal skin specimens, were studied by indirect immunofluorescence technique. Six uninvolved dermatitis herpetiformis skin specimens showed distinctly decreased immunoreaction for BP230 and four uninvolved dermatitis herpetiformis skin specimens showed distinctly decreased immunoreaction for plectin/HD1. All five skin controls showed strong immunoreactions for BP230 and plectin/HD1. Other hemidesmosomal proteins including BP180 and integrin 64, as well as basement membrane proteins laminin-5, laminin-1, nidogen and type IV collagen, and the anchoring fibril protein type VII collagen showed a normal strong expression. Our results suggest that alterations in BP230 and plectin/HD1 may contribute or predispose to blister formation in dermatitis herpetiformis skin.     

Fast and sensitive determination of urinary 1-hydroxypyrene by packed capillary column switching liquid chromatography coupled to micro-electrospray time-of-flight mass spectrometry

The present work reports capillary liquid chromatographic column switching methodology tailored for fast, sensitive and selective determination of 1-hydroxypyrene (1-OHP) in human urine using micro-electrospray ionization time-of-flight mass spectrometric detection. Samples (100 microl) of deconjugated, water diluted and filtered urine samples were loaded onto a 150 microm I.D.x 30 mm 10 microm Kromasil C(18) pre-column, providing on-line sample clean-up and analyte enrichment, prior to back flushed elution onto a 150 microm I.D.x 100 mm 3.5 microm Kromasil C(18) analytical column. Loading flow rates up to 100 microl/min in addition to the use of isocratic elution by a mobile phase composition of acetonitrile/water (70/30, v/v) containing 5 mM ammonium acetate provided elution of 1-OHP within 5.5 min and a total analysis time of less than 15 min with manual operation. Ionization was performed in the negative mode and 1-OHP was observed as [M-H](-) at m/z 217.08. The method was validated over the concentration range 0.2-40 ng/ml 1-OHP in pre-treated urine, yielding a coefficient of correlation of 0.997. The within-assay (n=6) and between-assay (n=6) precisions were in the range 6.4-7.3 and 7.0-8.1%, respectively, and the recoveries were in the range 96.2-97.5 within the investigated concentration range. The method mass limit of detection was 2 pg, corresponding to a 1-OHP concentration limit of detection of 20 pg/ml (0.09 nmol/l) diluted urine or 0.3 ng/ml (1.35 nmol/l) urine.     

A search for H/ACA snoRNAs in yeast using MFE secondary structure prediction

MOTIVATION: Noncoding RNA genes produce functional RNA molecules rather than coding for proteins. One such family is the H/ACA snoRNAs. Unlike the related C/D snoRNAs these have resisted automated detection to date. RESULTS: We develop an algorithm to screen the yeast genome for novel H/ACA snoRNAs. To achieve this, we introduce some new methods for facilitating the search for noncoding RNAs in genomic sequences which are based on properties of predicted minimum free-energy (MFE) secondary structures. The algorithm has been implemented and can be generalized to enable screening of other eukaryote genomes. We find that use of primary sequence alone is insufficient for identifying novel H/ACA snoRNAs. Only the use of secondary structure filters reduces the number of candidates to a manageable size. From genomic context, we identify three strong H/ACA snoRNA candidates. These together with a further 47 candidates obtained by our analysis are being experimentally screened.     

Endonuclease Specificity and Sequence Dependence of Type IIS Restriction Enzymes

Restriction enzymes that recognize specific sequences but cleave unknown sequence outside the recognition site are extensively utilized tools in molecular biology. Despite this, systematic functional categorization of cleavage performance has largely been lacking. We established a simple and automatable model system to assay cleavage distance variation (termed slippage) and the sequence dependence thereof. We coupled this to massively parallel sequencing in order to provide sensitive and accurate measurement. With this system 14 enzymes were assayed (AcuI, BbvI, BpmI, BpuEI, BseRI, BsgI, Eco57I, Eco57MI, EcoP15I, FauI, FokI, GsuI, MmeI and SmuI). We report significant variation of slippage ranging from 1–54%, variations in sequence context dependence, as well as variation between isoschizomers. We believe this largely overlooked property of enzymes with shifted cleavage would benefit from further large scale classification and engineering efforts seeking to improve performance. The gained insights of in-vitro performance may also aid the in-vivo understanding of these enzymes.     

A Probabilistic Model for Hydrokinetic Turbine Collision Risks: Exploring Impacts on Fish

A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m), bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.     

Lipase-Catalyzed Synthesis and Hydrolysis of Cholesterol Oleate in Aot/Isooctane Microemulsions

We have examined a lipase-catalyzed bidirectional ester synthesis/hydrolysis reaction in a water-in-oil microemulsion system. The reactants were cholesterol (alcohol), oleic acid (acid) and cholesterol oleate (ester), and the solvent system consisted of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water. The reactions were assayed by using [³H]oleic acid, [³H]cholesterol, or [³H]cholesterol oleate for the synthesis and hydrolysis reactions, respectively (separate incubations). The lipase that we used derived from Candida cylindracea, and was used at a concentration of 0.1mg/ml microemulsion. The reactions were performed at 22°C as the reactions proceeded more slowly at higher temperatures. With the initial reactant concentrations set to 10 mM cholesterol, 1 min oleic acid, and 1 mM cholesterol oleate, it was observed that the optimal [H₂O]/[AOT] ratio was at about 9 both for the esterification reaction and for the hydrolysis reaction (after 24 h). The hydrolysis reaction was slower than the synthesis reaction at all [H₂O]/[AOT] ratios studied (0-20), but the difference in reaction yield for the synthesis and the hydrolysis reactions became smaller as the reaction time increased (up to 11 days). When the reaction yield was followed as a time function, it was observed that about 80% of the oleic acid was esterified within 3 days of reaction ([H₂O]/[AOT] ratio of 6), whereas the corresponding value of 80% hydrolysis of cholesterol oleate was reached within 11 days. The results of the present study indicate that by choosing optimal reactant concentrations and reaction conditions, it is at least in part possible to determine the direction of the lipase-catalyzed synthesis/hydrolysis reaction.     

Hydrokinetic Turbine Effects on Fish Swimming Behaviour

Hydrokinetic turbines, targeting the kinetic energy of fast-flowing currents, are under development with some turbines already deployed at ocean sites around the world. It remains virtually unknown as to how these technologies affect fish, and rotor collisions have been postulated as a major concern. In this study the effects of a vertical axis hydrokinetic rotor with rotational speeds up to 70 rpm were tested on the swimming patterns of naturally occurring fish in a subtropical tidal channel. Fish movements were recorded with and without the rotor in place. Results showed that no fish collided with the rotor and only a few specimens passed through rotor blades. Overall, fish reduced their movements through the area when the rotor was present. This deterrent effect on fish increased with current speed. Fish that passed the rotor avoided the near-field, about 0.3 m from the rotor for benthic reef fish. Large predatory fish were particularly cautious of the rotor and never moved closer than 1.7 m in current speeds above 0.6 ms^-1. The effects of the rotor differed among taxa and feeding guilds and it is suggested that fish boldness and body shape influenced responses. In conclusion, the tested hydrokinetic turbine rotor proved non-hazardous to fish during the investigated conditions. However, the results indicate that arrays comprising multiple turbines may restrict fish movements, particularly for large species, with possible effects on habitat connectivity if migration routes are exploited. Arrays of the investigated turbine type and comparable systems should therefore be designed with gaps of several metres width to allow large fish to pass through. In combination with further research the insights from this study can be used for guiding the design of hydrokinetic turbine arrays where needed, so preventing ecological impacts.     

Flows of Chemical Risk Information in the Consumer Paint Product Chain

In this study the flows of chemical risk information for paint as a consumer product were investigated from a product chain perspective. The main method of research involved semi‐structured interviews with Swedish manufacturers of paint and chemicals. In addition, retailers and consumers were interviewed. The flows of chemical risk information between actors within (e.g., manufacturers, retailers, and consumers) and outside (e.g., industry associations and regulators) the paint product chain are described. Because the European chemical legislation REACH (Registration, Evaluation, Authorization and restriction of CHemicals) plays a large role in the management of chemical risk information at companies, some consequences of REACH on actors in the paint product chain are described. Examples of such consequences are that importing of chemicals from non–European Union (EU) countries may be discouraged and that some low‐volume chemicals may no longer be produced. However, manufacturers do not yet see these consequences as impediments to innovation. The results of this work show that chemical risk information is most comprehensive during the manufacturing steps of the product chain. This is due not only to tradition and industry initiatives, but also to REACH and other legislation. The results also illustrate the need for evaluation of how chemical risk information is used in different contexts and the importance of directing the right information at the right target group. Following legislative development, more specialized information is required in the safety data sheet (SDS), and because of this many manufacturers find it necessary to create simplified safety sheets that make the most pertinent safety and hazard information easily accessible to individuals that handle the chemicals in their factories. The study found that in creating the simplified safety sheets, the content and use of chemical risk information is evaluated and adjusted for presentation to this particular target group. It is evident that the Swedish Paint and Printing Ink Makers Association plays an important role in the interpretation of legal requirements and even in agreements for providing information that exceeds legal requirements.