Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Threshold Limit Values”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources
PubMed1981

Occupational exposure to dust containing free silica in a ceramics factory.

In a ceramics plant employing 225 workers, respirable dust was collected into personal samplers worn by exposed workers. Analysis by X-ray diffraction documented exposures to free silica greater than 50 micrograms/m3-the permissible exposure level or threshold limit value-time weighted average proposed by the U.S. National Institute of Occupational Safety and Health-in 15 of 25 determinations. Excessive exposures were produced by dust with quartz content less than or equal to 8% by weight. If there had been such exposures to free silica-containing dust in the past, X-ray findings compatible with silicosis, described in a group of workers employed for 5 to 23 years prior to this study could be accounted for. The exposures appeared to be due to failure to incorporate established principles for prevention of dust exposure when the plant was designed. Routine determination of free silica content, even at trace and low levels, is necessary to assess the potential hazard for silicosis in dusty workplaces.

Air Pollutants↗
PubMed1993

Occupational asthma due to zinc.

We describe a subject who developed asthma symptoms 2 yrs after being employed at a plant where metals were galvanized in heated zinc. The subject was not atopic. Baseline spirometry was normal three months after he left work but there was mild bronchial hyperresponsiveness to methacholine. Monitoring of forced expiratory volume in one second (FEV1) during a day at work showed a maximum fall in FEV1 of 24% at the end of the day and an increase in bronchial responsiveness on the following day. Environmental monitoring revealed that zinc and iron were present in the working environment at concentrations that were lower than the "threshold limit value-short term exposure level" (TLV-STEL) standards. Positive immediate skin tests to zinc sulphate at concentrations of 1 and 10 mg.ml-1 were obtained, although no specific immunoglobulin E (IgE) antibodies to zinc could be found. Skin tests with copper, chromium and cobalt were negative. Specific inhalation challenges were performed, having the subject inhale a solution of zinc sulphate at a 10 mg.ml-1 concentration for 6 min. An immediate reaction was elicited (maximum fall in FEV1 of 23%). We conclude that zinc can cause occupational asthma.

Asthma↗
PubMedDate not supplied

Serum prolactin in subjects occupationally exposed to manganese.

To evaluate whether or not occupational exposure to manganese (Mn) affects basal levels of serum prolactin (PRL), a cross-sectional study was carried out in 31 occupationally-exposed workers, aged 39.2 years (DS 7.9) exposed to manganese (Mn) dusts for 14.5 years (range: 5 to 29 years) in a ferroalloy producing plant. Thirty-four industrial workers not exposed to neurotoxic chemicals and of comparable age composed the control group. Airborne Mn concentrations in dusts of the furnace area ranged 210 to 980 micrograms/m3, which is below the current American Conference of Governmental Industrial Hygienists (ACGIH)-recommended threshold limit value-time weighted average (TLV-TWA) of 1 mg/m3. Manganese concentrations in blood Mn (MnB) and in urine (MnU) were significantly higher in Mn-exposed workers as compared to control workers. The Mn-exposed workers showed significantly higher serum prolactin (PRL) levels with the geometric mean (GM) being 9.77 ng/ml with a geometric standard deviation (GSD) of 1.69 as compared to controls (GM 4.65 ng/ml, GSD 1.78, p < 0.001). Serum PRL was negatively related to age and positively correlated with both MnB and MnU. Dose-effect relationships were still significant in partial correlation analysis after control for age. The prevalence of abnormally high PRL values was consistent with a dose-response relationship. The observed increase in serum PRL among Mn-exposed workers suggests an impairment of tonic inhibition by tubero-infundibular dopaminergic neurons. The correlation between PRL and both MnB and MnU in samples collected at least 48 h from the last exposure suggests that such indices provide an estimation of the target dose.

Adult↗
PubMed2005

Leaching of diethylhexyl phthalate from multilayer tubing into etoposide infusion solutions.

PURPOSE: The extent of leaching of diethylhexyl phthalate (DEHP) from various polyvinyl chloride (PVC), polyethylene (PE), coextruded (PVC and PE), and triple-layered (PVC, ethyl vinyl acetate, and PE) i.v. extension tubing into etoposide infusion solutions was studied. METHODS: Different lengths of tubing (25, 50, and 80 cm) were tested in two types of experiments: (1) static, in which the etoposide solution was left in contact inside the tubing for various times and then removed, and chromatography was used to quantify the DEHP content of the effluate, and (2) dynamic, in which infusion was simulated using syringe reservoirs, and three flow rates were tested to assess the effect of flow rate on the quantities of DEHP leached. RESULTS: The static study showed that large quantities of DEHP were leached from all tubing types except the PE tubing. The dynamic study confirmed that leaching occurred, although the values were below the threshold limit of 5 microg/mL. The values varied depending on flow rate, tubing length, and etoposide concentration. The coextruded and triple-layered i.v. tubing did not provide the inertness and safety they are intended to have, as DEHP not only leached out but did so in quantities almost equivalent to those found with tubing made of PVC only. CONCLUSION: DEHP leached rapidly from PVC, coextruded, and triple-layered i.v. tubing into etoposide infusion solution. The quantity of DEHP found in the infusion solution was influenced by the length of the tubing and concentration of etoposide.

Chromatography, High Pressure Liquid↗
PubMed2002

Threshold disorder as a source of diverse and complex behavior in random nets.

We study the diversity of complex spatio-temporal patterns in the behavior of random synchronous asymmetric neural networks (RSANNs). Special attention is given to the impact of disordered threshold values on limit-cycle diversity and limit-cycle complexity in RSANNs which have 'normal' thresholds by default. Surprisingly, RSANNs exhibit only a small repertoire of rather complex limit-cycle patterns when all parameters are fixed. This repertoire of complex patterns is also rather stable with respect to small parameter changes. These two unexpected results may generalize to the study of other complex systems. In order to reach beyond this seemingly disabling 'stable and small' aspect of the limit-cycle repertoire of RSANNs, we have found that if an RSANN has threshold disorder above a critical level, then there is a rapid increase of the size of the repertoire of patterns. The repertoire size initially follows a power-law function of the magnitude of the threshold disorder. As the disorder increases further, the limit-cycle patterns themselves become simpler until at a second critical level most of the limit cycles become simple fixed points. Nonetheless, for moderate changes in the threshold parameters, RSANNs are found to display specific features of behavior desired for rapidly responding processing systems: accessibility to a large set of complex patterns.

Algorithms↗
PubMed2005

Synthesis, structure, and large optical limiting effect of the first coordination polymeric cluster based on an {I@[AgI(inh)]6} hexagram block.

In this paper, treatment of N-(isonicotinoyl)-N'-nicotinoylhydrazine (inh) and AgI with excess KI afforded a unique coordination polymeric cluster {[AgI(inh)]6(KI)}n (1) with the hexagram cluster units centered by mu6-I. In the polymer these hexagram units are parallel to the ab plane and are linked by separated K+ centers through inh. Polymer 1 represents the first example of coinstantaneous cation-anion-induced supramolecular self-assembly with nanoscale inner cavities. The polymer's third-order nonlinear optical (NLO) properties were determined by the Z-scan technique in DMF solution. The results show that the polymer has strong third-order optical nonlinearities. The nonlinear absorptive index a2 and refractive index n2 are calculated to be 1.044 x 10(-9) mW(-1) and 2.827 x 10(-11) esu, respectively. The values are comparable to those of the reported cluster polymers. The optical limiting experiments show that the present cluster exhibits a large optical limiting capacity. The value of the limiting threshold was measured as 0.53 J cm(-2) from the optical limiting experimental data. This value is three times better than 1.6 J cm(-2) of C60. This paper also gives a summary and comparison on the optical limiting properties of oligomeric and polymeric clusters.

Journal Article↗
PubMed1996

[Occupational exposure in the operating room by isoflurane when using the laryngeal mask].

Success of intraocular surgery depends in part on low intraocular pressure, sufficient muscle relaxation during the operative period, and avoidance of coughing during emergence from anaesthesia. Isoflurane (ISO) guarantees deep anaesthesia and Laryngeal Mask Airway (LM) makes emergence smoother than when using conventional endotracheal intubation. Occupational exposure to isoflurane appears unavoidable near the potential main source of leakage, the "patient's mouth". Due to the short distance between the patient's mouth and the working area, the risk of exposure for the surgeon could be high. Traces of anesthetic gases may cause various negative effects on the health of the personnel. Higher abortion rates are reported on in recent literature. The aim of this study was to quantify trace amounts of ISO and then to compare these values with international threshold limits. In this study, trace concentrations of ISO were measured directly by means of a high sensitive photoacoustic infrared spectrometry analyser. Measurements were done continuously every 120 seconds at the working places of the surgeon, anaesthetist and the assisting nurse. One possible leakage source, the patient's mouth, was also analysed. 10 cataract operations under general anaesthesia were included in the study. All the measured values were low, the majority under 2 ppm isoflurane. The national threshold values (10 ppm) were not exceeded. We conclude that the use of the LMA in ventilated patients is not associated with high concentrations of isoflurane in the working environment of the operating theatre personnel during eye surgery. Trace concentrations of isoflurane using the LMA are comparable with those using ET under these working conditions. Under other working conditions, higher concentrations may be expected should therefore be controlled.

Air Pollutants, Occupational↗
PubMed2004

Can you be large and not obese? The distinction between body weight, body fat, and abdominal fat in occupational standards.

Weight control is an important early intervention in diabetes, but the nature of the association between weight and disordered metabolism has been confused because fat mass and its distribution are only partly associated with increasing body size. Weight, fat, and regional fat placement, specifically in the abdominal site, may each have distinctly different associations with diabetes risk. Abdominal circumference may be the common marker of poor fitness habits and of increased risk for metabolic diseases such as diabetes. This is an important question for public health policy as well as for occupational standards such as those of the military, which are intended to promote fitness for military missions and include strength and aerobic capacity, as well as military appearance considerations. U.S. soldiers are heavier than ever before, reflecting both increased muscle and fat components. They also have better health care than ever before and are required to exercise regularly, and even the oldest soldiers are required to remain below body fat limits that are more stringent than the current median values of the U.S. population over age 40. The body fat standards assessed by circumference-based equations are 20-26% and 30-36%, for various age groups of men and women, respectively, and the upper limits align with threshold values of waist circumference recommended in national health goals. The basis and effects of the Army standards are presented in this paper. U.S. Army body fat standards may offer practical and reasonable health guidelines suitable for all active Americans that might help stem the increasing prevalence of obesity that is predicted to increase the prevalence of Type 2 diabetes.

Abdomen↗
PubMed2006

[Possibilities and limitations of statistical regression models for the calculation of threshold values for minimum provider volumes].

Inadequate statistical procedures are often applied for the derivation of threshold values in various medical research areas. The frequently applied method to establish threshold values on the basis of simple comparisons between arbitrarily defined low-volume and high-volume groups may be misleading because the result depends on the preceding classification. In this paper, the possibilities and limitations of statistical regression models for the calculation of threshold values are described. The features of these models for the selection of minimum volumes for hospitals or physicians are discussed. Simulated data examples are used to demonstrate that the definition of a useful minimum provider volume should not be based upon a calculated value of purely mathematical meaning without clinically assessing the risk curve. In the application of statistical regression models to retrospective observational data it should be noticed that calculated threshold values are only of a hypothesis-generating character. In order to verify that a minimum provider volume leads to the expected quality improvement, a prospective intervention study is required.

Data Interpretation, Statistical↗
PubMed2003

[Clinical evaluation of a new thyroglobulin immunoradiometric assay in the follow-up of differentiated thyroid carcinoma].

AIM: Formal and clinical comparison of a new 3 (rd) -generation-Tg-IRMA (3-G-IRMA; Dynotest Tg-plus) with a conventional Tg-IRMA (3-G-IRMA; SELco Tg-assay) for patients with differentiated thyroid carcinoma. In addition we evaluated, if thyroglobulin (Tg) levels above a specific threshold concentration indicate the need for further investigations for residual disease. PATIENTS, METHODS: Tg concentration of 105 sera of 93 consecutive patients with a differentiated thyroid cancer was determined with both assays and compared at different cut-off values (Dynotest Tg-plus: 0.2, 1, 2 ng/ml; SELco Tg-assay: 0.5, 1, 2 ng/ml) with the clinical results in respect to the corresponding TSH concentration. RESULTS: Tg concentration did not show any significant difference (SELco Tg-assay 0.5 ng/ml, Dynotest Tg-plus 0.2 ng/ml). The Tg-values of both assays correlated with 97%. However, correlation of recovery in both assays was small (40%). The sensitivities and specificities of both assays at different cut-offs and TSH values did not reveal significant differences. In patients with TSH concentration > 30 micro U/ml the functional assay sensitivity was superior to arbitrary cut-offs in the decision to start further evaluations. CONCLUSIONS: In our study neither formal nor clinical significant differences between two Tg-assays were found. In a hypothyroid patient (TSH > 30 micro U/ml, Tg concentration exceeding the functional assay sensitivity) further investigations for residual disease are warranted. Higher thresholds are of limited value, due to an unacceptably high rate of false negative results.

Carcinoma↗
PubMed2002

Predicting recovery in patients suffering from traumatic brain injury by using admission variables and physiological data: a comparison between decision tree analysis and logistic regression.

OBJECT: Decision tree analysis highlights patient subgroups and critical values in variables assessed. Importantly, the results are visually informative and often present clear clinical interpretation about risk factors faced by patients in these subgroups. The aim of this prospective study was to compare results of logistic regression with those of decision tree analysis of an observational, head-injury data set, including a wide range of secondary insults and 12-month outcomes. METHODS: One hundred twenty-four adult head-injured patients were studied during their stay in an intensive care unit by using a computerized data collection system. Verified values falling outside threshold limits were analyzed according to insult grade and duration with the aid of logistic regression. A decision tree was automatically produced from root node to target classes (Glasgow Outcome Scale [GOS] score). Among 69 patients, in whom eight insult categories could be assessed, outcome at 12 months was analyzed using logistic regression to determine the relative influence of patient age, admission Glasgow Coma Scale score, Injury Severity Score (ISS), pupillary response on admission, and insult duration. The most significant predictors of mortality in this patient set were duration of hypotensive, pyrexic, and hypoxemic insults. When good and poor outcomes were compared, hypotensive insults and pupillary response on admission were significant. Using decision tree analysis, the authors found that hypotension and low cerebral perfusion pressure (CPP) are the best predictors of death, with a 9.2% improvement in predictive accuracy (PA) over that obtained by simply predicting the largest outcome category as the outcome for each patient. Hypotension was a significant predictor of poor outcome (GOS Score 1-3). Low CPP, patient age, hypocarbia, and pupillary response were also good predictors of outcome (good/poor), with a 5.1% improvement in PA. In certain subgroups of patients pyrexia was a predictor of good outcome. CONCLUSIONS: Decision tree analysis confirmed some of the results of logistic regression and challenged others. This investigation shows that there is knowledge to be gained from analyzing observational data with the aid of decision tree analysis.

Adult↗
PubMed1998

Assessment of subacute mammary inflammation by soluble biomarkers in comparison to somatic cell counts in quarter milk samples from dairy cows.

The usefulness of soluble markers in indirectly differentiating inflamed quarters from healthy quarters of 30 Holstein Friesian cows was tested over a follow-up period of 20 weeks. In comparison to N-acetyl-beta-D-glucosaminidase (NAGase), lactate dehydrogenase (LDH), Na+, K+ and Cl- the somatic cell counts (SCC) were determined in foremilk samples. The soluble parameters were measured by means of an autoanalyzer system (Beckman CX5CE) equipped with solid state ion electrodes. Due to different types of inflammatory reactions it is considered to be advantageous to perform two tests in parallel for assessing the mammary gland status. Cell-damaging processes should best be detected by measuring elevated LDH activity, whereas the impairment of the blood-udder barrier is recorded by the respective elevation of the indicators Na+ and Cl-. Among all variables, SCC included, the soluble parameters showed the least dispersions, whereas those of SCC were the most unfavourable in this respect. Moreover, NAGase/LDH and Na+/Cl- among all variables had the highest correlation coefficients of 0.85 and 0.86, respectively. Threshold values as decision limits are proposed. Additionally, an inter-quarter comparison and evaluation improved the diagnostic value of each indirect mastitis parameter analyzed. By means of discriminant analysis, it is shown that the distribution of inflammation within the udders of this herd was unequal.

Acetylglucosaminidase↗
PubMed2025

Viral viability markers of SARS-CoV-2: a comparison of cell culture, genomic RNA RT-PCR, and subgenomic RNA RT-PCR.

UNLABELLED: Accurate methods to assess viral viability are crucial for determining isolation duration and antiviral therapy in immunocompromised patients. Although cell culture (CC) is the gold standard, it has limitations. Cycle threshold (Ct) values from genomic RNA (gRNA) RT-PCR and subgenomic RNA (sgRNA) RT-PCR have been proposed as markers of active viral replication. This study evaluated the correlation between CC, gRNA Ct values, and sgRNA to identify the best viral viability marker. This study aimed to evaluate the correlation between CC, gRNA Ct values, and sgRNA to identify the best viral viability marker. We conducted a prospective study on immunocompromised patients with suspected SARS-CoV-2 infection at a tertiary hospital (May 2021 to May 2023). Nasopharyngeal swabs were inoculated into Vero E6 cells and tested for gRNA using RT-PCR (Cobas 6800, Roche) and for sgRNA (non-commercial RT-PCR). The sensitivity (S), specificity (SP), positive (PPV) and negative predictive value (NPV), and accuracy were calculated using CC as the gold standard. Among 285 samples from 108 patients, gRNA RT-PCR had high S and NPV (1.0) but low SP (0.24) and moderate PPV (0.63). Ct analysis improved performance in extreme but not intermediate values. A Ct &#x2264; 30 maximized S but had low SP; Ct &#x2264; 25 yielded S (0.88), SP (0.89), PPV (0.92), NPV (0.84), and accuracy (0.88); sgRNA showed the highest S (0.99), SP (0.96), PPV (0.97), NPV (0.99), and accuracy (0.98). sgRNA detection is the best marker for identifying viable SARS-CoV-2, aiding decisions on isolation, antiviral treatment, or delaying chemotherapy in immunocompromised patients. IMPORTANCE: Identifying whether a patient still has contagious SARS-CoV-2 is essential for managing isolation, antiviral treatment, and other clinical decisions-especially in immunocompromised individuals. While viral culture is the gold standard for confirming viral viability, it is slow, expensive, and not widely available. Many hospitals rely on RT-PCR tests, but these detect viral genetic material whether or not the virus is still active. This study shows that detecting subgenomic RNA (sgRNA), a molecule only present when the virus is actively replicating, is a highly accurate way, a molecule only present when the virus is actively replicating, is a highly accurate way to determine whether the virus is still viable. Compared to standard PCR or viral culture, sgRNA testing better predicts who is truly infectious. These findings support sgRNA as a useful tool to guide clinical management and infection control in vulnerable patients.

Humans↗
PubMed1998

Comparison of three-dimensional virtual endoscopy with bronchoscopy in patients with oesophageal carcinoma infiltrating the tracheobronchial tree.

Virtual endoscopy (VE) is a technique for performing simulated bronchoscopy using helical CT data of the tracheobronchial tree. In order to evaluate a virtual three-dimensional (3D) endoluminal procedure for the tracheobronchial tree, comparison was made between bronchoscopy, axial CT images and minimal intensity projections (MIP). 21 patients were referred for helical CT because of oesophageal carcinoma shown by bronchoscopy to infiltrate into the trachea or bronchi. Axial CT images obtained on a helical scanner were transferred to a Sparc20 workstation. VE was compared with the axial CT images and the MIP concerning additional information on the location and degree of stenosis gained after 3D reconstruction of the inner surface of the tracheobronchial tree. The accuracy of this VE system was compared with bronchoscopy. Follow-up was performed in two patients to evaluate the tracheobronchial system after stent implantation. All stenoses were identified by VE with no statistically significant difference in detection of location or grading of the stenosis to real time bronchoscopy. Passage of subtotal stenosis was only possible with VE. VE is suitable for following up stent implantation. Submucosal lesions of the tracheobronchial tree could not be detected by VE. There was no statistically significant difference regarding the location of the stenoses between VE, axial CT slices, MIP and bronchoscopy. The VE showed only a statistically significant difference with regard to the degree of stenosis which was underrated on axial CT slices and MIPs. Pitfalls including mucus plugs and wall defects due to the wrong threshold value were a limitation of VE. VE is presently too time-consuming to use in every patient with an infiltrating tumour into the tracheobronchial tree. In conclusion, while VE cannot replace endoscopy of the tracheobronchial tree or the oesophagus, it is an accurate and non-invasive method for identifying endoluminal tumours, grading stenoses and visualizing the tracheobronchial tree beyond stenoses in a small number of patients who are not amenable to endoscopy.

Aged↗
PubMedDate not supplied

Air pollution by odour--sources, identification and control.

Although odour pollution of air is not directly harmful to the health of man, it can affect mental attitudes and enjoyment of the environment. The present article reviews the sources of odours in gases and vapours, their effects, methods for their sensory and instrumental detection, their characterisation, threshold values and maximum limits. Industrial sources for offensive odours, such as meat, fish and other food processing plants, leather tanneries, sewage and domestic refuse processing plants, oil refineries, paper pulp, paint and plastic manufacturers, are outlined. Physical, chemical and biological methods for odour control are discussed and criteria for selection of a control method, depending upon available conditions and possibilities, are listed.

Air Pollutants↗
PubMed1994

Measuring the burden of secondary insults in head-injured patients during intensive care.

Primary traumatic brain damage may be compounded by secondary pathophysiological insults that can occur soon after trauma, during transfer to hospital or subsequent treatment of the head-injured patient. The aim of this prospective study was to quantify the burden of a wide range of secondary insults occurring after head injury and to relate these to 12-month outcome. In 124 adult head-injured patients studied during intensive care using a computerized data collection system, < or = 14 clinically indicated physiological variables were measured minute-by-minute. Verified values falling outside threshold limits for > or = 5 min, as defined by the Edinburgh University Secondary Insult Grading scheme, were analysed by insult grade and duration. A greater incidence of secondary insults was detected than previous studies have indicated. Insults were found in 91% of patients and occurred in all severities of head trauma, at all ages, and at every level of Injury Severity Score (ISS). The cumulative durations were much greater than previously recorded although 85% of the total time was at the least severe grade. Short duration insults were common. In 71 patients, in whom 8 insults could be assessed (intracranial pressure, arterial hypo- and hypertension, cerebral perfusion pressure, hypoxemia, pyrexia, brady- and tachycardia), outcome at 12 months was analysed using logistic regression to determine the relative influence of age, admission Glasgow Coma Sumscore, ISS, pupil response on admission, and insult duration on both mortality and morbidity. The most significant predictors of mortality in this patient set were durations of hypotensive (p = .0064), pyrexic (p = .0137), and hypoxemic (p = .0244) insults. When good versus poor outcome was considered, hypotensive insults (p = .0118) and pupil response on admission (p = .0226) were significant.

Adult↗
PubMed1989

Retinal damage thresholds from single-pulse laser exposures in the visible spectrum.

The risks of using lasers, particularly ocular hazards, have called for the definition of exposure limits. Our investigations involved the retinal effects of the laser beam in the visible spectrum and were directed toward verifying the limit values by defining the thresholds of retinal damage in experiments carried out on the rabbit and the monkey. The wavelengths emitted by the experimental set-ups were 593 and 532 nm, the pulse durations were 600 and 40 ns, and the retinal image diameter varied from approximately 30 to 570 microns. A direct ophthalmoscopic observation and a method using fluorescein angiography were employed to detect a pathologic change in the retina. The energy correlates of retinal lesions were statistically analyzed by a method of probit analysis. The results showed that determining funduscopic thresholds is chiefly a function of the investigation technique used and the delay in observation after the exposure. Our results obtained with fluorescein angiography extrapolated to the human eye support the exposure limit established for intrabeam viewing, but not for an extended source laser which corresponds to a probability of damage increasing with the retinal image diameter. The exposure limit related to the experimental retinal spot size of 285 and 570 microns corresponds to damage probabilities of 7% and 32%, respectively.

Animals↗