The Bear Brook Watershed in Maine (BBWM), USA is a paired watershed study with chemical manipulation of one watershed (West Bear = WB) while the other watershed (East Bear = EB) serves as a ...reference. Characterization of hydrology and chemical fluxes occurred in 1987-1989 and demonstrated the similarity of the ca. 10 ha adjacent forested watersheds. From 1989-2010, we have added 1,800 eq (NH₄)₂SO₄ ha ⁻ ¹ y ⁻ ¹ to WB. EB runoff has slowly acidified even as atmospheric deposition of SO graphic removed has declined. EB acidification included decreasing pH, base cation concentrations, and alkalinity, and increasing inorganic Al concentration, as SO graphic removed declined. Organic Al increased. WB has acidified more rapidly, including a 6-year period of increasing leaching of base cations, followed by a long-term decline of base cations, although still elevated over pretreatment values, as base saturation declined in the soils. Sulfate in WB has not increased to a new steady state because of increased anion adsorption accompanying soil acidification. Dissolved Al has increased dramatically in WB; increased export of particulate Al and P has accompanied the acidification in both watersheds, WB more than EB. Nitrogen retention in EB increased after 3 years of study, as did many watersheds in the northeastern USA. Nitrogen retention in WB still remains at over 80%, in spite of 20+ years of N addition. The 20-year chemical treatment with continuous measurements of critical variables in both watersheds has enabled the identification of decadal-scale processes, including ecosystem response to declining SO graphic removed in ambient precipitation in EB and evolving mechanisms of treatment response in WB. The study has demonstrated soil mechanisms buffering pH, declines in soil base saturation, altered P biogeochemistry, unexpected mechanisms of storage of S, and continuous high retention of treatment N.
Objectives A wide range of low-molecular-weight agents can cause occupational asthma. The chemical industry is an environment in which numerous hazardous substances are used. Lasamide ...(2,4-dichloro-5-sulfamoylbenzoic acid) is one of them (along with its precursors). Methods Five patients from a lasamide production line with suspected occupational asthma and rhinitis were examined. During the first visit, skin prick tests, total immunoglobulin E (IgE), a nonspecific bronchoprovocation test, and specific bronchoprovocation tests using occupational agents were performed to confirm the diagnosis of allergic diseases. During the follow-up visit (1-3 years after removal from exposure), all of the tests (except the specific bronchoprovocation test) were performed again. Results At the first hospitalization, the total IgE levels were increased in three patients. In addition, skin prick tests and the nonspecific bronchoprovocation test were positive for three patients. After the specific bronchoprovocation test, serious bronchoconstriction occurred in three patients; symptoms of rhinitis were present in all five patients. Several years after removal from exposure to the occupational agents, normalization (with respect to the parameters followed) was not yet complete for all of the patients. Conclusions The process of lasamide production seems to be hazardous and is likely to cause allergic respiratory disease. The prognosis of allergic diseases caused by these products is not very favorable. Allergic symptoms (despite the removal from occupational allergen exposure) persisted even after several years.
Newly developed dental composite materials contain increased concentrations of filler particles of the nanometer size to produce materials with high mechanical and wear resistance, improved ...polishability, and long-lasting gloss. With nanocomposites, however, a question arises on possible health risk caused by filler nanoparticles released during finishing and polishing nanocomposite restorations in dental cabinets. As data in the current literature are conflicting, our study was focused on detailed characterization of aerosol particles released during grinding nanocomposites Filtek Ultimate and Estelite Sigma Quick by diamond and tungsten carbide bladed burs. The results were compared with the aerosol particle size obtained from a composite Charisma reinforced with micrometer-size filler particles and an unfilled resin. Using a scanning mobility particle sizer and aerodynamic particle sizer, the release of nano- and micro-sized particles generated during high-speed grinding was detected. The mode of nanoparticle size distribution ranged not only from less than 16.0 to 51.6 nm for both nanocomposites, but also for the microhybrid composite and the unfilled resin. However, the amount of nanoparticles in the aerosol (5.0–68) × 10
3
cm
−3
was not high exceeding 1–8.5 times their background concentration. The release of nanoparticles independently on the filler particle size and their content might suggest that the aerosol nanoparticles may originate from thermal decomposition of composite polymeric matrix due to friction heat rather than from filler nanoparticles. Due to the potential adverse health effects of nanoparticles, more detailed research is needed to investigate the effect of finishing conditions on the nanoparticle generation and their chemical composition to avoid any potential risk to dental staff. A study of the aerosol formed during grinding with water cooling to avoid heating will also be carried out.
Graphical abstract
This work presents a new method for generating a BrCl solution, starting from the commercially available dibromodimethylhydantoin (DBDMH). This method is notable due to the straightforward, safe and ...clean performance, being based on a simple addition of DBDMH into aqueous HCl. The whole procedure is finished in about 20 min. An advantage of the proposed method is avoiding of tedious reagents pre-cleaning by prolonged thermal treatment, spontaneous overheating and excessive vapor evolution. The resulting BrCl stabilization reagent is low enough in mercury content to be directly used in trace mercury analysis. A thorough study of the BrCl solutions prepared by this method showed that they conform in all respects to US EPA 1631e/2002 requirements.
Novel method for the determination of a tumor marker homovanillic acid (HVA) in human urine was developed. Combination of hollow fiber – based liquid-phase microextraction (HF-LPME) and differential ...pulse voltammetry (DPV) at a cathodically pre-treated boron doped diamond electrode (BDDE) was applied for these purposes. Optimum conditions were: butyl benzoate as supported liquid membrane (SLM) formed on polypropylene HF, 0.1 mol L−1 HCl as donor phase, 0.1 mol L−1 sodium phosphate buffer of pH 6 as acceptor phase, and 30 min extraction time. HF-LPME-DPV concentration dependence was linear in the range from 1.2 to 100 μmol L−1. Limits of quantification (LOQ) and detection (LOD) were 1.2 and 0.4 μmol L−1, respectively. The applicability of the developed method was verified by analysis of human urine. Standard addition method was used, found HVA concentration was 13.5 ± 1.3 μmol L−1, RSD = 9.3% (n=5).
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•New hollow-fiber microextraction determination of homovanillic acid.•Microextraction coupled with differential pulse voltammetry.•Cathodically pre-treated boron doped diamond working electrode.•Green solvent butyl benzoate as supported liquid membrane.•Method verified using real human urine sample.
To study the dynamics and clinical determinants of chronic retinal nerve fiber layer thickness (RNFL) loss after methanol-induced optic neuropathy.
Prospective cohort study.
All patients underwent ...complete ophthalmic evaluation including spectral-domain optical coherence tomography 3 times during 4 years of observation: 4.9 (±0.6), 25.0 (±0.6), and 49.9 (±0.5) months after discharge. Participants: Eighty-four eyes of 42 survivors of methanol poisoning, mean age (standard deviation) of 45.7 (±4.4) years; and 82 eyes of 41 controls, mean age 44.0 (±4.2) years. Main Outcome Measures: Global and temporal RNFL loss.
Abnormal RNFL thickness was registered in 13 of 42 (31%) survivors of methanol poisoning and chronic axonal loss in 10 of 42 (24%) patients. Significant decrease of global/temporal RNFL thickness during the observation period was found in the study population compared to the controls (P < .001). The risk estimate of chronic global RNFL loss for arterial blood pH < 7.3 at admission was 11.65 (95% confidence interval 1.91–71.12) after adjusting for age and sex. The patients with chronic axonal degeneration demonstrated progressive visual loss in 7 of 10 cases. The patients with abnormal RNFL thickness had magnetic resonance signs of brain damage in 10 of 13 vs 8 of 29 cases with normal RNFL thickness (P = .003). Signs of brain hemorrhages were present in 7 of 13 patients with abnormal RNFL thickness vs 5 of 29 cases with normal RNFL thickness (P = .015).
Methanol-induced optic neuropathy may lead to chronic retinal axonal loss during the following years. Arterial blood pH on admission is the strongest predictor of chronic RNFL thickness decrease. Chronic retinal neurodegeneration is associated with the progressive loss of visual functions and necrotic brain lesions.
To find a practical biomonitoring method for researchers exposed to nanoparticles causing oxidative stress.
In a continuation of a study in 2016-2018, biological samples (plasma, urine and exhaled ...breath condensate EBC) were collected in 2019-2020 from 43 researchers (13.8 ± 3.0 years of exposure) and 45 controls. Antioxidant status was assessed using glutathione (GSH) and ferric-reducing antioxidant power, while oxidative stress was measured as thiobarbituric acid reactive substances, all using spectrophotometric methods. Researchers' personal nanoparticle exposure was monitored.
Plasma GSH was elevated in researchers both before and after exposure (p < 0.01); postexposure plasma GSH correlated with nanoparticle exposure, and GSH in EBC increased.
The results suggest adaptation to chronic exposure to nanoparticles, as monitored by plasma and EBC GSH.
Abstract
Objectives. Methanol poisonings occur frequently globally, but reports of larger outbreaks where complete clinical and laboratory data are reported remain scarce. The objective of the ...present study was to report the data from the mass methanol poisoning in the Czech Republic in 2012 addressing the general epidemiology, treatment, and outcomes, and to present a protocol for the use of fomepizole ensuring that the antidote was provided to the most severely poisoned patients in the critical phase. Methods. A combined prospective and retrospective case series study of 121 patients with confirmed methanol poisoning. Results. From a total of 121 intoxicated subjects, 20 died outside the hospital and 101 were hospitalized. Among them, 60 survived without, and 20 with visual/CNS sequelae, whereas 21 patients died. The total and hospital mortality rates were 34% and 21%, respectively. Multivariate regression analysis found pH < 7.0 (OR 0.04 (0.01-0.16), p < 0.001), negative serum ethanol (OR 0.08 (0.02-0.37), p < 0.001), and coma on admission (OR 29.4 (10.2-84.6), p < 0.001) to be the only independent parameters predicting death. Continuous hemodialysis was used more often than intermittent hemodialysis, but there was no significant difference in mortality rate between the two 29% (n = 45) vs 17% (n = 30), p = 0.23. Due to limited stockpiles of fomepizole, ethanol was administered more often; no difference in mortality rate was found between the two 16% (n = 70) vs. 24% (n = 21), p = 0.39. The effect of folate administration both on the mortality rate and on the probability of visual sequelae was not significant (both p > 0.05). Conclusions. Severity of metabolic acidosis, state of consciousness, and serum ethanol on admission were the only significant parameters associated with mortality. The type of dialysis or antidote did not appear to affect mortality. Recommendations that were issued for hospital triage of fomepizole administration allowed conservation of valuable antidote in this massive poisoning outbreak for those patients most in need.
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