Decades of experience support the inclusion of odours in the list of contaminant types that must be regulated by government. In many jurisdictions, odour impacts are regulated under the nuisance ...provisions of common law. However, the explicit conditions that establish whether a nuisance condition exists are not easily defined. Due to this shortcoming, there is a need to introduce objectivity into odour impact assessments and odour limits. While individual responses to odours are highly variable and can result in a variety of effects, generally the impacts of odours arise from a variety of interacting factors, collectively known as FIDOL: frequency, intensity, duration, offensiveness, and location. In view of the need to prevent or mitigate such impacts, an approach to odour regulation is proposed in which the protection of the public from odour impacts is accomplished based on the FIDOL approach. This involves the introduction of an objective odour limit, as follows: “
Facilities that are identified as sources of potentially offensive odours shall ensure that the 10-min average concentration of odour resulting from all sources at the facility and determined in accordance with accepted procedures, shall be less than 1 odour unit 99.5% of the time at the most impacted sensitive receptor”. It is argued that the proposed limit would provide the public with an understanding of the degree of protection from odours that is to be provided through regulations and would provide industries with a basis for designing their facilities to minimize impact at the design stage. Such limits would also provide industries with benchmarks against which they can gauge their success at preventing or mitigating odour impacts and for evaluating the effectiveness of odour control technologies.
Di(2-ethylhexyl)phthalate (DEHP) is a widely used plasticizer to render poly(vinyl chloride) (PVC) soft and malleable. Plasticized PVC is used in hospital equipment, food wrapping, and numerous other ...commercial and industrial products. Unfortunately, plasticizers can migrate within the material and leach out of it over time, ending up in the environment and, frequently, the human body. DEHP has come under increased scrutiny as its breakdown products are believed to be endocrine disruptors and more toxic than DEHP itself. DEHP and its breakdown products have been identified as ubiquitous environmental contaminants, and daily human exposure is estimated to be in the microgram per kilogram level. The objective of this review is to summarize and comment on published sources of DEHP exposure and to give an overview of its environmental fate. Exposure through bottled water was examined specifically, as this concern is raised frequently, yet only little exposure to DEHP occurs through bottled water, and DEHP exposure is unlikely to stem from the packaging material itself. Packaged food was also examined and showed higher levels of DEHP contamination compared to bottled water. Exposure to DEHP also occurs in hospital environments, where DEHP leaches directly into liquids that passed through PVC/DEHP tubing and equipment. The latter exposure is at considerably higher levels compared to food and bottled water, specifically putting patients with chronic illnesses at risk. Overall, levels of DEHP in food and bottled water were below current tolerable daily intake (TDI) values. However, our understanding of the risks of DEHP exposure is still evolving. Given the prevalence of DEHP in our atmosphere and environment, and the uncertainty revolving around it, the precautionary principle would suggest its phaseout and replacement. Increased efforts to develop viable replacement compounds, which necessarily includes rigorous leaching, toxicity, and impact assessment studies, are needed before alternative plasticizers can be adopted as viable replacements.
Phthalate plasticizers are incorporated into plastics to make them soft and malleable, but are known to leach out of the final product into their surroundings with potential detrimental effects to ...human and ecological health. The replacement of widely-used phthalate plasticizers, such as di-ethylhexyl phthalate (DEHP), that are of known toxicity, by the commercially-available alternative Tris(2-ethylhexyl) tri-mellitate (TOTM) is increasing. Additionally, several newly designed "green" plasticizers, including di-heptyl succinate (DHPS) and di-octyl succinate (DOS) have been identified as potential replacements. However, the impact of plasticizer exposure from medical devices on patient recovery is unknown and, moreover, the safety of TOTM, DHPS, and DOS is not well established in the context of patient recovery. To study the direct effect of clinically based chemical exposures, we exposed C57bl/6 N male and female mice to DEHP, TOTM, DOS, and DHPS during recovery from cardiac surgery and assessed survival, cardiac structure and function, immune cell infiltration into the cardiac wound and activation of the NLRP3 inflammasome. Male, but not female, mice treated in vivo with DEHP and TOTM had greater cardiac dilation, reduced cardiac function, increased infiltration of neutrophils, monocytes, and macrophages and increased expression of inflammasome receptors and effectors, thereby suggesting impaired recovery in exposed mice. In contrast, no impact was detected in female mice and male mice exposed to DOS and DHPS. To examine the direct effects in cells involved in wound healing, we treated human THP-1 macrophages with the plasticizers in vitro and found DEHP induced greater NLRP3 expression and activation. These results suggest that replacing current plasticizers with non-phthalate-based plasticizers may improve patient recovery, especially in the male population. In our assessment, DHPS is a promising possibility for a non-toxic biocompatible plasticizer.
The influence of central structure and side chain length on plasticizer effectiveness of succinate and maleate diesters blended into poly(vinyl chloride) (PVC) was assessed by tensile testing, DMTA, ...and surface hardness measurements. While no significant differences between central structures with similar side chain lengths were found, the length of the side chain played an important role, and maximum effectiveness was found for the linear dihexyl esters. In comparison to commercial plasticizers such as DEHP and Hexamoll® DINCH®, succinates and maleates with linear side chains of four to eight carbons performed as well or better in several of the mechanical tests. Earlier work had established that the proposed succinate and maleate compounds exhibited higher biodegradation rates than DEHP, and pending toxicity studies, they seem to be viable replacement compounds for DEHP.
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•Development of green plasticizers to replace phthalates.•Evaluation of mechanical properties of linear succinate and maleate diesters.•Highest plasticizer effectiveness for dihexyl succinate and maleate.•No added benefit of ethyl branch in di (2-ethylhexyl) compounds.•Several compounds of both series performed as good or better than DEHP and DINCH®.
The detection of illicit drugs in environmental matrices may be a cause for concern, both from the perspective of their potential environmental impacts and the fact that their presence in detectable ...concentrations would be an indicator of significant drug use. The primary goal behind recent studies on this subject has been to use measured influent concentrations of selected illicit drugs or their
in vivo metabolites in the environment as a means of estimating the abuse level of these drugs and patterns of consumption. Thus-far, such calculations have hinged on the use of solitary excretion estimates from single studies of limited scope and/or studies of limited applicability. Therefore, the need exists to conduct a comprehensive meta-analysis of metabolic disposition studies to construct excretions profiles for the various illicit drugs and their
in vivo metabolites. The constructed excretory profiles should not only provide mean excretion values but also indicate the expected variations in excreted fractions that arise due to differences not only in the metabolic capacity of users but also in the efficiencies of various routes of administration for a given illicit drug. Therefore, the primary goal of the research presented here was to refine sewer epidemiology extrapolation mass balances for various illicit drugs of interest by constructing their excretory profiles segregated by route-of-administration. After conducting such a study with a multi-national scope on illicit drugs including cocaine, heroin and ecstasy, the results obtained clearly indicate that extrapolation factors currently being used in literature for these drugs to enumerate prevalence of abuse required significant refinement to increase their reliability.
► Generalized sewer epidemiology extrapolation mass balances were developed for illicit drugs. ► The proposed methodology was demonstrated for cocaine, heroin and ecstasy. ► Extrapolation factors were refined to increase their reliability.
In sewer epidemiology, mass balances are used to back-extrapolate measurements of wastewater influent concentrations of appropriate drug residues to assess the parent illicit drug's level of use in ...upstream populations. This study focussed on developing and refining mass balances for the use of illicit methamphetamine, amphetamine and tetrahydrocannabinol. As a first step, a multi-criteria evaluation was used to select unchanged methamphetamine, unchanged amphetamine and 11-nor-9-carboxy-tetrahydrocannabinol as the most appropriate drug residues to track a selected population's use of illicit methamphetamine, amphetamine and tetrahydrocannabinol, respectively. For each of these selected drug residues, mass balances were developed by utilizing all disposition data available for their release from all their respective sources, incorporating route-of-administration considerations where relevant, and accounting for variations in the metabolic capacity of users of the various relevant licit and illicit sources. Further, since the selected drug residues for the use of methamphetamine and amphetamine cannot only result from their use but numerous other licit and illicit sources, comprehensive general source models were developed for their enantiomeric-specific release to sewers. The relative importance of the sources identified in the general source model was evaluated by performing national substance flow analyses for a number of countries. Results suggested that licit sources of methamphetamine are expected to be only of significance in populations where its illicit use is minor. Similarly, in populations where the use of illicitly produced amphetamine is currently of relevance, licit contributions to the sewer loads of amphetamine are likely to be of negligible importance. Lastly, the study of tetrahydrocannabinol back-extrapolation mass balances suggested that further research is required to assess the importance of fecal elimination of 11-nor-9-carboxy-tetrahydrocannabinol.
► Amphetamine, methamphetamine and THC were selected for study. ► Sewer epidemiology mass balances were developed for the three illicit drugs. ► Source models were developed to describe the release of selected metabolic markers. ► Importance of illicit and licit sources was assessed using substance flow analyses.
This work explores the relationships between a user's choice of a given contraceptive option and the load of steroidal estrogens that can be associated with that choice. Family planning data for the ...USA served as a basis for the analysis. The results showed that collectively the use of contraception in the USA conservatively averts the release of approximately 4.8 tonnes of estradiol equivalents to the environment. 35% of the estrogenic load released over the course of all experienced pregnancies events and 34% the estrogenic load represented by all resultant legacies are a result of contraception failure and the non-use of contraception. A scenario analysis conducted to explore the impacts of discontinuing the use of ethinylestradiol-based oral contraceptives revealed that this would not only result in a 1.7-fold increase in the estrogenic loading of the users, but the users would also be expected to experience undesired family planning outcomes at a rate that is 3.3 times higher. Additional scenario analyses in which ethinylestradiol-based oral contraceptive users were modeled as having switched entirely to the use of male condoms, diaphragms or copper IUDs suggested that whether a higher or lower estrogenic load can be associated with the switching population depends on the typical failure rates of the options adopted following discontinuation. And, finally, it was estimated that, in the USA, at most 13% of the annual estrogenic load can be averted by fully meeting the contraceptive needs of the population. Therefore, while the issue of estrogen impacts on the environment cannot be addressed solely by meeting the population's contraceptive needs, a significant fraction of the estrogenic mass released to environment can be averted by improving the level with which their contraceptive needs are met.
•A model describing the laccase-catalyzed oxidation of phenols at low concentrations is presented.•Losses in enzyme activity were accounted for during the catalytic reaction.•The model was validated ...for the substrates estradiol, cumylphenol, triclosan and phenol.•Predictions were accurate over orders of magnitude of substrate and enzyme concentrations.•The feasibility of targeting substrates at low concentrations for oxidation was explored.
Laccase catalyzes the oxidation of aqueous phenolic substrates by oxygen. To assess the feasibility of using this enzyme to oxidize aqueous phenols at low concentrations, a five-parameter kinetic model was developed based on previous work to predict the transient kinetics of reactions catalyzed by laccase from Trametes versicolor. The model was calibrated against data collected at pH 5.0 and 25 °C for batch reactions of triclosan, cumylphenol, and estradiol. Phenol data arising from an earlier study was used for comparison. The kinetic model, which incorporated a term for enzyme inactivation, accurately simulated the time course of reactions of all four compounds for ranges of substrate and laccase concentrations that spanned up to 5 orders of magnitude. Furthermore, it was demonstrated that the model made accurate predictions far outside of the range of its calibration. The utility of the model for assessing the feasibility of using laccase to catalyze the oxidation of substrates over a range of reactant concentrations was demonstrated. Modelling and experimental results showed that estradiol, cumylphenol and triclosan can be oxidized through the catalytic action of laccase at aqueous substrate concentrations in the micromolar to nanomolar concentration range, while using substantially less enzyme than required for phenol.
A series of glycerol‐based compounds were investigated for their application as plasticizers for flexible poly(vinyl chloride) (PVC) blends. The effect of plasticizer chemical structure on the ...performance, migration behavior, and blend morphology were evaluated and compared to blends produced using the commercial plasticizer dioctyl terephthalate (DOTP). Blends containing 40 phr (parts per hundred rubber) of glycerol‐based plasticizer showed a considerable reduction (between 54 to 86°C) in glass transition temperature (Tg) relative to neat PVC (Tg ~ 80°C). Tensile testing of samples prepared with the glycerol analogs demonstrated higher ductility (elongation at break values of up to 97%) than DOTP (elongation at break value of 75%) at identical plasticizer loadings. The surface morphologies showed excellent incorporation of the glycerol plasticizers functionalized with alkyl chains longer than four carbons in length into the PVC matrix, whereas droplet formation was observed in blends with shorter chain glycerol derivatives. Leaching behavior of the plasticized samples were evaluated into different media and showed that plasticizers comprised of branched, or longer alkyl chains produced 2‐ to 4‐fold lower migration rates compared to those with shorter alkyl chains into polar solutions.
Bio‐based glycerol plasticizers can be used to produce highly‐flexible poly(vinyl chloride) (PVC) materials with equal, or superior, tensile properties to commercial plasticizer dioctyl terephthalate (DOTP).
•The transient kinetics of the laccase-catalyzed oxidation of aqueous phenol was modeled.•Phenol concentrations were in the micromolar to sub-micromolar range.•Inactivation of the enzyme during the ...oxidation reaction was insignificant.•The 4-parameter model was validated over wide ranges of phenol and enzyme concentrations.•The model could be simplified to a 3 parameter model with only minor loss in accuracy.
Oxidoreductase enzymes have the potential to be used to catalyze the oxidation of aromatic trace contaminants in wastewaters. The feasibility of this approach can be explored by modeling transient kinetics, particularly in the low substrate concentration range, where the model may be used to predict the quantity of enzyme and time required to achieve a particular level of conversion of a target compound. Laccase from Trametes versicolor was selected as a candidate enzyme due to its wide substrate specificity and its use of molecular oxygen as an oxidant. Phenol was selected as a target substrate. A four-parameter kinetic model was developed based on the known reactions of laccase. The model was applied to 30 sets of data collected from batch reactions conducted at pH 5 and 25°C over a three hour period. Initial phenol concentrations ranged from 0.5 to 50μM and applied enzyme concentrations ranged from 0.12 to 2.5μM. The model demonstrated its utility for predicting the quantities of enzyme and reaction times required to achieve desired levels of oxidation of phenol for varying initial concentrations. A three-parameter simplified version of the kinetic model was also developed to facilitate calibration and mathematical solution of its equations.
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