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 1,045 records · Page 58Linked to original sources
PubMedDate not supplied

[Tunneling of autowaves through unexcitable parts of active media].

The mechanisms of propagation of autowaves through local heterogeneities in active media were studied by computer simulation. The model proposed by Zel'dovich and Frank-Kamenetsky and that of FitzHugh-Nagumo were used for studying autowave tunneling. It was shown that the underbarrier passage of an autowave through a nonexcitable area is limited by threshold values. It was shown that, for every fixed parameter value corresponding to the degree of nonexcitability of a local area, there exists a critical value for nonexcitable zone latitude. An autowave overcomes the barrier and continues to propagate when the value of zone latitude is less than the critical. Critical conditions for the origination of sources of secondary periodical sequences of impulses in excitable medium were found. It was shown that the properties of sources of secondary autowaves can be modified by regulating the size of the nonexcitable zone and the zone of increased excitability. In particular, the conditions were explored under which spatial irregularity behaves as a source of a unidirectional and/or an asynchronous sequence of impulses.

Biophysical Phenomena↗
PubMedDate not supplied

[Ventilatory functions in subjects exposed to hydrogen peroxide at levels below the TLV: longitudinal study].

In the bottling departments of a beverage processing plant, exposure to hydrogen peroxide was below TLV from 1995 to 2001. Forced vital capacity (FVC), forced expiratory volume 1st second (FEV1), and FEV1/FVC were compared between exposed and unexposed workers. Using sparse data collected from 1993 to 2002, changes over time (slope) were calculated for each functional index in each subject. The slope was the dependent variable at multiple regression analysis with exposure and smoking as predictive variables. Using complete data collected from 2000 to 2002 in fewer subjects, the longitudinal changes were assessed by repeated measures analysis of variance. Both methods provide same results: with respect to unexposed, in exposed workers FVC increased, FEV1/was unchanged and FEV1/FVC decreased; the latter difference was no more significant when FVC slope was added as covariate to the model. In conclusion, the findings seem to support the current TLV for hydrogen peroxide. There were no similar studies in the literature.

Forced Expiratory Volume↗
PubMedDate not supplied

[Airborne asbestos fibers: law references, TLV, considerations].

The ACGIH proposal of 0.1 fibers/liter as TLV for airborne asbestos fibers isn't a properly parameter, because it is applicable in work environments and the Italian legislation has forbidden every work which employs asbestos from 1993 [Law 257/92 and Min.Dec. 6/9/94]. Actually in Italy the application of a TLV is only referred to two analytical results: A) 20 ff/liter by CPOM analysis, B) 2 ff/liter by SEM analysis. We think that a CPOM 4-5 ff/liter is a no trespassing limit and over this concentration alarm may be notified. Waste disposal of asbestos materials must be properly disposed in a restricted area.

Air Pollutants, Occupational↗
PubMed2003

Antioxidant vitamins levels--nutrition and smoking.

The plasma levels of antioxidant vitamins express the risk rate of free radical disease. Limit values (risk threshold) were determined in long-term epidemiological and clinical studies. Over-threshold (optimal) values mean an effective protection and a reduced risk of the disease. Values below threshold (deficient) from antioxidant point of view increase this risk. Optimal levels of each antioxidant at different age are required for the maintenance of optimal health. Vitamin C and beta-carotene are derived from fruits and vegetables. The decrease of antioxidant vitamins in smokers caused by free radical presence in tobacco smoke is known. The levels of vitamins C, E and beta-carotene were estimated in two ethnic groups of young adult population of Western Slovakia (n = 122--Gipsy minority; n = 137--majority population). Vitamins levels are correlated to nutrition, smoking and education. Vitamin E levels are similar in both groups; frequency of values with optimal antioxidant effect is equal (21%). In Gipsy group are significantly reduced the vitamin C and beta-carotene levels with only 28% over-threshold values of vitamin C and 7% over-threshold values of beta-carotene vs 46% and 25% in the majority group. The reduced levels of antioxidant vitamins in Gipsy minority group are a consequence of inadequate nutrition (lower and infrequent consumption of fruit and vegetables, low knowledge about optimal nutrition affected by low education--85% of Gipsy subjects have elementary and apprentice education vs 27% of majority subjects) and smoking (smokers--55% of Gipsy persons vs 25% in majority group subjects; 42 and 50% reduced vitamin levels in smokers). (Tab. 1, Fig. 1, Ref. 17.).

Adolescent↗
PubMed2004

Toxicology primer: understanding workplace hazards and protecting worker health.

Hazardous substances are ubiquitous in the environment and common in industrialized societies. Serious harm can occur with sufficient exposures under certain conditions. However, much harm can be avoided if hazardous substances are handled with respect and appreciation for their use and potential. Occupational health nurses must be aware of potential hazards to employees in the work environment and apply scientific principles to their practice of promoting worker safety and health.

Adult↗
PubMed2004

New EMF safety limits for occupational and public exposure in Poland.

On July 23, 2001, new safety limits for occupational exposure to electromagnetic fields (EMF) were introduced in Poland. The limits have been based on the analysis of international recommendations, e.g., ICNIRP (1998), WHO (1998), IEEE standard (1999), drafts of European standards (ENV 1995), and a critical review of the world literature on the biological effects of EMF and health effects of exposure to EMF. Derived from safety limits for occupational exposure, new safety exposure limits for general population were introduced on November 28, 2003. In this paper mandatory procedures for setting limits of exposure to agents harmful to health in the workplace and natural environment are presented. The most essential provisions of two regulations, one issued by the Minister of Labour and Social Policy and the other by the Minister of the Environment, forming the basis of the modern system of EMF exposure control in Poland, are also discussed.

Electromagnetic Fields↗
PubMed2004

The gender gap.

Explore the source record for details and available documents.

Adult↗
PubMed2006

[Maximum acceptable weight of lift for manual lifting tasks].

OBJECTIVE: To explore the maximum acceptable weight of lift (MAWL) in different lifting conditions and the suitable lifting equation for the stipulation of occupational health standard of manual lifting tasks in China. METHODS: The MAWL was investigated among the thirteen male and ten female students using psychophysical methodology and the recommended weight of limit (RWL) was compared. RESULTS: The MAWL of male and female subjects was decreased gradually with the increase of lifting height. Once the height of lifting was over shoulder, the MAWL was decreased dramatically. The RWL was greater than the MAWL at 25 cm horizontal distance in male subjects, but the RWL was smaller than the MAWL at the distance of 45 cm and 63 cm. The average MAWL of male subjects was 30.8% greater than that of female subjects. The MAWL was decreased gradually with increase of the horizontal distance at the same height of lifting. The result of the male subjects was consistent with that of the female subjects. For the asymmetric lifting tasks of the male subjects, the bigger the angle of rotation was, the less the MAWL became. The angle of rotation had negative correlation with the capability of lifting (r = -0.996 6, P < 0.01). When the subjects performed asymmetric lifting tasks, the RWL was smaller than the MAWL and the difference was significant. CONCLUSION: The revision is sufficient for the horizontal distance and asymmetric lifting in the NIOSH lifting equation, but it is not suitable for height, especially for the task of lifting over shoulder. The RWL for the task of lifting over shoulder should be lowered. The factor of gender should be taken into account in the lifting equation and the constant of gender S can be added. Then S = 1 for male while S = 0.692 for female.

Adult↗
PubMed2006

Development of carcinogenicity classifications and evaluations: the case of formaldehyde.

In this paper carcinogenicity classification and evaluations case of formaldehyde made by national and international agencies and organizations (such as European Union, International Agency for Research on Cancer, World Health Organization) both in occupational (such as American Conference of Government Industrial Hygienists, National Institute of Occupational Safety and Health and Occupational Health and Safety Administration) and non occupational environment (such as United States Environmental Protection Agency) are proposed. The differences in the database and consequently in the conclusion are described in a short historical review since formaldehyde was considered for the first time as regard as health effects.

Carcinogens↗
PubMed1999

Autoantibodies to neurofilaments (NF), glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) in workers exposed to lead.

An expanded follow-up assessment of the autoantibody response to neuronal and astroglial autoantigens (NF68; NF160; NF200; MBP; GFAP) as early markers of neurotoxicity was performed in male workers exposed to lead (Pb) of a battery factory (n=50) and a matched reference group (R) of workers at a food packing plant (n=39). Mean age, years of exposure and blood lead (PbB ug/dl) (+/-SD) for lead and R, respectively, were: Age:39 +/- 6; 41 +/- 7; Yrs. Exposed: 14 +/- 6:0; PbB: 32 +/- 11: 16 +/- 5 percent with detectable titers to nervous system proteins in the Pb and R populations, respectively, were: Anti-NF68: 59; 17; Anti-NF160: 28; 15; Anti-NF200: 25; 0; Anti-GFAP: 90; 20; Anti-MBP: 16; 4. Autoantibodies to nervous system proteins predominated in workers occupationally exposed to Pb compared to R. Anti-NF68 and GFAP titers were the most frequently encountered. Anti-NF68 titers were significantly correlated with years of exposure (r = 0.538, p < 0.0001) and with PbB (r=0.325, p < 0.05). Furthermore, the number of detectable autoantibody types correlated with clinical scores of sensorimotor deficits (r = 0.459, p < 0.0001). This study suggests that autoantibodies provide a promising biomarker of neurotoxicity while providing information on subcellular targets. It also raises concerns of toxicant-induced autoimmune neuropathy.

Adult↗
PubMed1999

Chromium induced contact dermatitis and indices for diagnosis.

Chromium exposure plays an important role in development of contact dermatitis. The prevalence of contact dermatitis among tannery workers and cement-exposed workers is high. This study was designed to determine the prevalence of contact dermatitis among some Egyptian workers exposed to chromium and to investigate the role of patch test and IgE immunoassay in diagnosis of contact dermatitis. Eighty-three male workers who were exposed to chromium were selected after application of certain exclusion criteria to be the target population of this study. Forty male workers away from exposure to chromium were taken to be the controls. All the exposed and non exposed workers were investigated through an interview questionnaire, clinical examination, patch test and determination of blood and urine chromium levels, absolute eosinophilic count and total IgE level. The results showed that there was no significant difference between exposed workers with clinically diagnosed contact dermatitis and the clinically free exposed workers regarding age and work duration. 7.7% of exposed workers with positive patch test suffered from contact dermatitis while 31.6% of exposed workers with negative patch test suffered from contact dermatitis. There was no statistically significant difference between clinically diagnosed contact dermatitis workers and clinically free workers regarding blood and urine chromium levels. IgE level and absolute eosinophilic count were statistically higher among exposed workers with contact dermatitis than among clinically free exposed workers. According to the results of this study, it is concluded that the diagnosis of skin hypersensitivity to chromium should depend upon the history of chromium exposure, clinical examination and a battery of investigations including IgE level, eosinophilic count and patch test.

Air Pollutants, Occupational↗
PubMed1989

[An epidemiological survey of goiter caused by excessive iodine in potable water in Cangzhou region].

This article describes a relationship between iodine and function and shape of thyroid gland. There was positive correlation between the prevalence rate of goiter and iodine content in drinking water [ln (10x)] and urine [ln (5x)]. Their curve fitting regression equations were y = 36.36 - 10.94 x + 0.83x2 and y = 22.39 - 6.36 x + 0.48x2 respectively. Use 3 per cent as criterion of disease area, threshold upper limit value of water and urinary iodine content should be 400 micrograms/L and 890 micrograms/gCr respectively.

Adolescent↗
PubMed1989

New methodology for specific inhalation challenges with occupational agents in powder form.

Numerous agents in powder form (wood dust, flour, antibiotics, drugs, etc.) can cause occupational asthma. The diagnosis is generally confirmed by specific inhalation challenges in a special challenge room. There are several pitfalls to the procedure: 1) subjects may be exposed to high concentrations of particles; the concentrations of particles may be higher than the threshold limit value-short term exposure level (TLV-STEL), possibly resulting in severe or irritant reactions; 2) the exposure is erratic. To overcome these problems, a new device for aerosolization of powders has been developed. This apparatus consists of three parts: a particles generator, an aerosol delivery system connected to an orofacial mask, and monitors - a photometer and a cascade impactor. Information on the concentration and size distribution of inhaled particles can therefore be obtained. We performed specific inhalation challenges with this apparatus on 20 subjects suspected of having occupational asthma. The concentration of particles was generally below or close to the TLV-STEL and information was obtained on the proportion of particles with a diameter less than 10 mu. Falls in forced expiratory volume in one second (FEV1) were progressive with each increase in the duration of exposure. The five subjects who had negative reactions to exposure were asked to tip the relevant product from one tray to another in the traditional realistic way. All had negative responses. We conclude that this new procedure offers advantages over the traditional method as it gives information on the concentration and size distribution of inhaled particles and makes the drawing of a dose-response curve possible, both of which may improve the safety and accuracy of the test.

Adult↗
PubMed1988

Acute exposure to sawdust does not alter airway calibre and responsiveness to histamine in asthmatic subjects.

We investigated the effects of particles of sawdust delivered through a special device at known concentrations (close to the threshold limit value-short term exposure limit (TLV-STEL) of 10 mg.m-3) on FEV1 and PC20 in 12 asthmatic subjects free of clinical sensitization to this product. Subjects were studied over two days (day 1: exposure to sawdust; day 2: sham exposure) in random order with a maximum interval of 1 week. On each day, after the assessment of spirometry and PC20, subjects underwent exposure to sawdust or sham exposure. Sawdust was inhaled for a total of 30 min at average concentrations varying from 8.0 to 19.3 mg.m-3 (mean = 11.5 mg.m-3). Twenty-five to 39.7% (mean = 34.6%) of inhaled particles had a diameter less than 10 mu (diameter allowing deposition in the trachea and lower respiratory tract). At the end of each period of exposure, FEV1 was assessed. After recovery, the second PC20 was obtained. Serial measurements of FEV1 were carried out every hour for up to 6 h after the end of exposure. At that time, PC20 was reassessed. Only one subject showed an acute bronchoconstriction immediately after exposure to sawdust (maximum fall of 14% in FEV1) with complete recovery 10 min later. Overall, inhalation of sawdust did not modify PC20 by comparing the mean result of the first test with the second and the third assessments. Also, the mean changes in PC20 at each interval after exposure to sawdust were not significantly different from the variations in PC20 on the sham day.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗