Increasing applications of nano materials in medicine, construction, textiles, computers, and other consumer goods have lead to increasing concerns of their effect on human health and ecology during synthesis, manufacturing, use, and disposal of nano-materials. Though much scientific progress has been made in nano material synthesis, manufacturing, and application in consumer goods and other sectors such as medicine, textiles and more, not much progress has been made in understanding the adverse effects of nano materials on human health and the environment. Physical, chemical, toxicological characteristics of these nano materials and their fate in the environment are important in understanding their adverse effects on the environmental and human health. This study is aimed at developing a preliminary framework for risk assessment (RA) and risk management (RM) of nano materials based on fundamental principles of chemistry, physics, toxicology, and other related disciplines.

PURPOSE: To investigate the plausibility of clinically significant oxygen toxicity in patients with retinal disorders being treated with hyperoxia therapy. Supplemental oxygen therapy is a promising form of treatment that may help reduce ischemia and the subsequent symptoms in patients suffering from diabetic retinopathy (DR), retinal vein occlusions (RVOs), and age-related macular degeneration (AMD). Currently, few studies perform ongoing assessments of current hyperoxia trials in patient populations. By investigating a current cohort of patients using supplemental oxygen to mitigate symptoms in their ocular conditions, we hope to demonstrate the extremely low likelihood of oxygen toxicity in patients utilizing hyperoxia therapy. Through these results, we hope to demonstrate that supplemental oxygen therapy is a viable, safe method of treatment for patients with ocular disorders. METHODS: A cohort of 16 patients was analyzed for changes in their C Reactive Protein (CRP), white blood cell count (WBC), hematocrit (Hct), and hemoglobin (Hb) levels after continuous use of hyperoxia therapy as part of treatment for varying retinal disorders. All study patients were diagnosed and under treatment at Beth Israel Deaconess Medical Center in Boston, MA. Patients diagnosed with diabetic retinopathy, retinal vein occlusions, or age-related macular degeneration were included in the study. Each of these patients must have also been prescribed 5 L/min of nocturnal hyperoxia therapy. Patients with insufficient data either before or after beginning the hyperoxia therapy were excluded. Primary outcome variables were arranged as pre- and post- hyperoxia therapy data points for CRP, WBC, Hb, and Hct. P-values below 0.05 would indicate statistically significant risk of oxygen toxicity in these variables under the current hyperoxia treatment. RESULTS: The mean age of the sample population was 64, with 6 of the 16 patients diagnosed with diabetes (37.5%). Patient groups were divided into diabetic vs. non-diabetic to assess whether or not one group was affected differently by the hyperoxia therapy. Results showed p-values well over 0.05 for both groups, indicating that oxygen toxicity is not a major risk factor when using supplemental oxygen under the study’s conditions. CONCLUSION: A large number of patients with diabetes suffer from retinal problems, especially with the onset of old age. These problems eventually require treatment via eye injections, laser, and even surgery in order to preserve vision and mitigate edema and ischemia. Given the high cost and invasive nature of these procedures, hyperoxia therapy provides a safe and potentially beneficial alternative to mitigate the symptoms of these disorders. This study hoped to demonstrate the plausibility of widespread clinical application for supplemental oxygen therapy in retina patients, while concluding that oxygen toxicity is not a significant risk factor in this type of treatment. The outcomes of this study support this hypothesis, and lay the groundwork for future studies that may assess the risks of oxygen toxicity on a larger scale. More research is required to gauge the true risks of oxygen toxicity in patients using supplemental oxygen. A case-controlled longitudinal study would also prove useful in providing data on changes in visual acuity and other experimental factors of interest, while accounting for several limitations present in this study. / 2021-06-17T00:00:00Z

INTRODUCTION According to ILO (2000), in developing countries about 59 per cent of labour force belongs to the agriculture sector. This is a particularly serious concern from the viewpoint of promoting the health of a population and reduction of social vulnerability in a country like Mozambique where more than half of the population depends on agriculture as their means of survival and wage earning. The current study attempts to address the agriculture mineral dust as occupational hygiene and health risk factors among agriculture workers, taking into account that dust that is breathed in may contain quartz, known as a carcinogenic and pathogenic agent. OBJECTIVE OF THE STUDY The study aims to pinpoint risk potential to health that may be caused by mineral dust through assessing occupational exposure doses to respirable dust and quartz during plowing, and primary and secondary tilling operations identified in the study, as the major dust risk operations; and the more prevailing operations in maize and root plant on medium sized farms‟ production cycle. MATERIALS AND METHODS Sampling of dust was conducted on 2 medium sized farms selected by convenience in the district of Boane (study setting) based on geological map soil characterisation of the study area. Full-time period dust samples were collected from 4 different tractor operators. The tractor operators were identified as the risky group. In total were taken seventy valid samples; thirty-nine from maize and thirty-one from root plant. Three tractor operators were fully engaged in maize cultivation and 1 was engaged in root plant during the period of the study data collection. In all occasions, the „open-cabbed‟ tractor machines were observed and used by tractor operators. The involved sampling subjects‟ operators were informed in advance about the study purpose and they accepted participation in the research. Nineteen dust samples were randomly selected for determination of the quartz fraction using the MDHS 101 Infrared Spectrophotometer Method. Active dust sampling MDHS 14/3 HD-cyclone method was applied with GLA 5000 filter type. All quality control procedures applied in active dust sampling method and gravimetric determination of concentration were checked in order to accept or reject samples for further analysis and determination of exposure concentration. RESULTS Standard statistical procedures and sampling strategy data analysis and interpretation procedures, including the SPSS software version 11.5 were used to produce valid results and findings. In the specific case of the agriculture sector, workers are found in changeable conditions and working time, therefore the effective working time distribution was estimated varying at a level of 311.6 min., 95 per cent CI (294-329.7). The observed minimal and maximal values were 179 and 500 min., respectively. The filter medium potential contamination was checked out through determination of the mass variation of the blank samples. The filter contamination was assumed possible through absorption and/or adsorption of humidity at level of minus 0.00407 mg with lower limit of minus 0.01 and upper limit of 0.00183 mg. The results on exposure indicate high exposure dose in maize crop cultivation in contrast to root plant crop cultivation. The findings show that in medium-sized farming, the average exposure to respirable dust is 0.702 (SD 0.571) and the average exposure for respirable quartz is 0.074 (SD 0.06). About 96 per cent of respirable dust exposure measurements were found in compliance with the South Africa standard for respirable dust; and for respirable quartz 74 per cent, 45 per cent and 17 per cent of exposure measurements were in compliance with the SA, NIOSH and ACGIH occupational exposure limits respectively. Each tractor operator‟s measurements showed a significant variation of the exposure concentration, probably due to the intraday and interday variation. The exposure measurements geometric standard deviation (GSD) was found equal or above 2.0 for both maize and root plant measurements and this indicates the influence of environmental factors in the exposure profile variation. CONCLUSION The research is supportive of some international published studies in which respirable quartz exposure in agriculture sector, although highly variable, has potential significance for over-exposure. The measurements of exposure to respirable quartz have shown over-exposure scenarios. However some were found below the permitted exposure limits.

Grassy arable field margins provide important permanent habitats for arthropods in agroecosystems and due to their proximity to high input areas, are exposed to pesticide drift. The aims of this thesis are to determine the likely effects of glyphosate drift in arable field margins by examining patterns of a medium quality spray drift intercepted by plant species in buffer strips and the effects of glyphosate on non-target field margin arthropods. Levels of mediumquality spray drift, analogous to herbicide drift, intercepted by field margin plant species in field boundaries were significantly reduced by inclusions of 2m and 6m wide buffer strips. Levels of spray drift interception varied between plant species and were related to plant height and leaf area. Dose-response testing of glyphosate against field margin plant species was done to establish inherent susceptibilities to the herbicide. Many species appeared to be unaffected by high levels of glyphosate (1800g ha^-1), while others had relatively high ED₅₀s that were unlikely to be exceeded by UK recommended rates of glyphosate. It was noted that lack of exposure to interspecific competition may have enhanced the plant species tolerance to high levels of glyphosate. Different rates of glyphosate were screened against the non-target arthropods Lepthyphantes tenuis (Araneae) and Leptopterna dolabrata (Heteroptera) to assess toxicity. Glyphosate was found to be non-toxic, however, applications of glyphosate to food plants increased mortality in L. dolahrata. In a field experiment, glyphosate applications of more than 360g ha^-1 to a grassy arable field margin reduced Araneae, Heteroptera and Carabidae abundance. Community analyses (DCA) indicated that communities in the field margins exposed to more than 360g ha^-1 glyphosate were distinct from unsprayed field margins. It is predicted that drift of field applied glyphosate at rates greater than 1440g ha^-1 would reduce phytophagous Heteroptera and Gonalium rubens (Araneae) abundance.

A large range of polymers are used in building and mass transport interiors which released more toxic products during combustion. This work explores the cytotoxicity of selected chemicals and smoke derived from materials combustion. A selection of polymers and fiberglass reinforced polymer (FRP) composites used in building and railway carriage interiors including: polyethylene (PE), polypropylene (PP), polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), melamine plywood, and two FRPs were studied. A small scale laboratory fire test using a vertical tube furnace was designed for the generation of combustion products. The volatile organic compounds were identified using ATD-GCMS (Automatic Thermal Desorption-Gas Chromatography Mass Spectrometry). The in vitro techniques were developed for human cells exposure to fire effluents including the indirect (impinger) and direct (air/liquid interface using Harvard Navicyte Chamber) exposure. Cytotoxic effects were assessed based on cell viability using a range of in vitro assays. Human skin tissue was also used as preliminary study to assess the toxic effects at the tissue level. A minor change in the cellular function of the skin from the exposure of PMMA combustion products was observed. The combustion study was conducted under different burning stage of fire: non-flaming and flaming combustion. Results suggested that PVC was the most toxic material for both non-flaming (IC50 1.24 mg/L) and flaming combustion (IC50 1.99 mg/L). The degree of toxicity generated depends on the fire stage: non-flaming or flaming combustion. Some materials revealed to be more toxic under flaming combustion (PP, PC, FRPs), whilst others (PVC, PMMA, PE, and melamine plywood) appear to be more toxic under non-flaming combustion. A strong correlation was shown between the change in toxicity as measured by IC50 and TLC and the change in concentration of volatile organic compounds (VOCs) and particulates. A comparison between in vitro data versus published in vivo combustion data indicated the in vitro results to be more sensitive than animal toxicity data. The outcome of this study has the potential for an alternative method to current fire toxicity standard, whilst providing more accurate toxicity information for fire safety professionals, materials manufacturer, building designers and consumer safety data.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

The use of chemicals to disperse oil spills raises concerns for organisms living below the surface of the water. While decreasing the surface area of the slick, chemical dispersants increase the amount of oil in the water column, the surface-to-volume ratio of droplets, the partitioning to water of the toxic constituents of oil, and the bioavailability of oil to pelagic and benthic organisms. Chemical dispersion can increase the exposure to polycyclic aromatic hydrocarbons (PAH) by 100-fold. As a model for a full-scale spill at sea, a wave tank was used to simulate chemical and natural dispersion of spilled oil to determine if the concentrations of chemically dispersed oil were sufficient to cause toxicity to embryos of Atlantic herring (Clupea harengus). While the hydrocarbon concentrations of dispersed oil from the wave tank were not large, the exposure response relationship was consistent with that of laboratory-prepared dispersed oil. Additionally, the toxicities of chemically dispersed oil prepared in the lab to Pacific (Clupea pallasi) and Atlantic herring were compared to ensure that the wealth of literature available on Pacific herring could be used for assessing the risk of oil exposure to Atlantic herring. Exposures to low concentrations of dispersed oil for short periods (2.4 to 24 h) consistently increased the incidence of blue sac disease, and decreased the percentage of normal embryos at hatch, indicating that even brief exposures to oil could be detrimental to the survival and recruitment of herring. / Thesis (Master, Biology) -- Queen's University, 2011-05-06 16:59:51.507