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At least 487 records · Page 27Linked to original sources
PubMed1989

[Intermodal vestibulo-optical transformation of sensory perception].

There is no objective correlate for a reduction of the absolute threshold of excitability of the vestibular organ during subliminal rotation by the exposition of transient light stimuli, i.e. an intermodal vestibulo-optical transformation, which is supposed to be possible in aesthesiophysiology. Only on rotation at a speed near the limit threshold value, pseudomotions of the exposed lighting point will occur. However, these are the consequences of an eye movement reflex, of fixation or cervical reflexes, i.e. a phenomenal event, and not an exteroceptive measure for the identification of subliminar vestibular stimuli.

Acceleration↗
PubMed2002

Platinum concentrations in sera of catalyst production workers are not predictive of platinum salt allergy.

Platinum (Pt) salts are potent occupational allergens in precious metal refineries and catalyst productions. The threshold limit value of 2000 ng soluble Pt/m3 enforced in many countries has been questioned because there is still a high incidence of Pt salt allergy. The objective of the present case series is to define the predictive value of biological monitoring by relating Pt in the serum of catalyst production workers and control subjects to sensitization to Pt salts as assessed by skin prick testing. A total of 38 Pt measurements were taken from sera of six workers investigated several times during a 5-year cohort study. Three subjects showed a conversion of skin prick test (SPT) with Pt salts from negative to positive during the cohort study (all considered highly exposed to Pt), and three did not show SPT conversion. Previous therapy with Pt-containing anti-cancer drugs and metallic dental alloys were considered as confounders. Only one of the three workers sensitized to Pt salt had clearly elevated serum Pt concentrations, but this elevation was not observed in each examination. Elevated Pt concentrations were also found in two subjects with low or no exposure to Pt. Both had metallic dental alloys. One control subject without metallic dental alloys showed low Pt concentrations in the serum in four examinations, but a single unexplained high concentration in his initial examination. In this small case series, serum Pt concentrations were neither sensitive nor specific for the prediction of Pt salt sensitization. Low specificity may be explained by Pt-containing metallic dental alloys, but additional unknown confounders may be of importance.

Adult↗
PubMed1975

Biological monitoring for industrial exposure to tetraalkyl lead.

An evaluation of the Chamber Works control program was made relative to the 1967 Threshold Limit Value (ACGIH) for tetraalkyl lead compounds. Results from fixed station samplers throughout the manufacturing areas had not correlated well with routine medical examinations and urinary excretion levels for lead. Similarly there was no correlation of fixed station results with urinary excretion rates. This suggested that personnel monitoring procedures would be necessary to obtain a valid evaluation of the highly variable ambient work atmosphere. No correlation could be established between personnel and fixed station monitor results; however, the mobile units gave significantly higher values. An approximately linear relationship between breathing zone lead levels and urinary excretion was found when the sum of the weekly average organic and inorganic lead TLV coefficients were related to the corresponding average urine excretion.

Air Pollution↗
PubMed1975

Occupational exposure limits for novel work schedules.

Work schedules other than 7 to 8 hr/day and 40 hr/week are being introduced in many industrial operations. Novel work schedules, such as four 10-hour workdays per week or three 12-hour workdays per week for three weeks followed by four 12-hour workdays for three weeks and several other plans are presently being used. The Threshold Limit Values (TLV) do not apply to such novel schedules. Modified occupational limits, which are calculable from the methods suggested in this report, estimate the needed reduction in the TLV to provide protection for exposed workers. A simple system is suggested, but should be cautiously applied with good medical surveillance. Industrial hygiene experience with novel work schedules will ultimately provide the real requirements for acceptable exposures under such work conditions.

Environmental Exposure↗
PubMed1975

Formaldehyde and paraformaldehyde study in funeral homes.

Formaldehyde is a toxic gas and classed as an upper respiratory irritant. The gas possesses distinctive physiological properties causing symptoms familiar to many formaldehyde workers, such as: burning of the eyes, lacrimation, and general irritation of the upper respiratory passages. To demonstrate this toxic action of formaldehyde a study was conducted in embalming rooms of funeral homes to determine the concentration and its effect on the embalmers at this level. The control measures in these establishments were also evaluated and found to be inadequate in some respects. Paraformaldehyde powders were sized and found to contain a respirable fraction. The results of the study show that these workers verified the fact that formaldehyde is an irritant at levels that are below the present Threshold Limit Value.

Air Pollutants, Occupational↗
PubMed1978

Quest for a gasoline TLV.

The major components in gasoline vapor generated during tank truck loading operations are identified. By analyzing 95 separate gasoline vapor samples, a mean Threshold Limit Value (TLV) for mixtures of about 300 ppm is calculated using 1976 TLV's for the individual hydrocarbons, if available. For compounds without an assigned TLV, a safe exposure value is estimated. Maximum levels of leaded gasoline additives tetraethyl/tetramethyllead, ethylene dibromide and ethylene dichloride are also estimated.

Benzene↗
PubMed1978

Analysis of formic acid in air samples.

The method reported here is for formic acid in air. Air containing formic acid is drawn through a midget impinger containing 15 ml of 0.1 N NaOH at a rate of one liter per minute for 42 minutes. An aliquot from the impinger is treated with an equal volume of ethanol-sulfuric acid mixture in a gastight reaction vial to produce ethyl formate. Because ethyl formate is volatile, an analysis of its vapor contained in the vial (headspace analysis) can be performed. The ethyl formate is analyzed by gas chromatography and its quantity is proportional to the quantity of formic acid contained in the reaction vial. With a relative standard deviation of 11 percent the method is precise enough for evaluating airborne formic acid at 0.1 of Threshold Limit Value of 9 mg/m3.

Air↗
PubMed1978

Phosphorus vapor exposure in phosphorus using plants.

Operator exposure to phosphorus in five areas in the five FMC using plants was documented primarily with area samplers. However, where significant levels of phosphorus vapors were found, personal sampling was also performed. Eight-hour time-weighted-average phosphorus exposure levels were estimated for operators in the phosphorus burning plants from the area measurements. Maintenance worker exposure was also studied. No worker was exposed to phosphorus concentrations above the current 0.1 mg/M3 threshold limit value (TLV).

Air Pollutants↗
PubMedDate not supplied

Measurement of benzene in the workplace and its evolution process, Part I: Overview, history, and past methods.

Benzene and its measurement continues to be important in the field of industrial hygiene. This two-part article reviews the history of occupational and environmental sampling and analysis of benzene from the early 1900s to the present. Part I provides an overview and details of the methods used in the past; history of the American Conference of Governmental Industrial Hygienists' threshold limit values for benzene; and reviews portable, grab, and integrated sampling methods as well as the various analytical methods. It is important to review and understand the past in order to predict future trends.

Air Pollutants, Occupational↗
PubMedDate not supplied

Measurement of benzene in the workplace and its evolution process, Part II: Present methods and future trends.

This article (the second of a two-part series) provides a discussion of currently accepted methodology and possible future happenings regarding measurement of benzene in workplaces. The gap between occupational and environmental monitoring is becoming narrow. Environmental levels will always be lower than the occupational, but as the push for lower threshold limit values continues, the focus should be on the environmental aspect as the ultimate limiting factor with respect to measurement. The charcoal tube/carbon disulfide desorption procedure is slowly being stretched to its limit with respect to benzene. It may be time for serious consideration in North America regarding adoption of the proven European procedure of thermal desorption using a porous polymer tube for analysis of benzene.

Air Pollutants, Occupational↗
PubMedDate not supplied

Biological monitoring of tetrahydrofuran: contribution of a physiologically based pharmacokinetic model.

A seven-compartment physiologically based pharmacokinetic (PBPK) model was developed to predict biological levels of tetrahydrofuran under various exposure scenarios. Affinities for the tissue were estimated from measurements of liquid-gas partition coefficients for water, olive oil, and blood. Metabolism was assumed to follow a rapid first order reaction. urinary excretion was simulated considering passive reabsorption of tetrahydrofuran in the tubules. The validity of the model was tested by comparison with available experimental and field data. Agreement was satisfactory with all studies available except one, which showed much higher results than expected. The source of this difference could not be identified, but cannot be explained by different exposure conditions, such as duration, concentration, or physical work load. However, it is recommended that this particular study not be used in the establishment of a biological exposure index. Simulation of repeated occupational exposure with the PBPK model allowed the prediction of biological levels that would be reached after repeated exposure at the American Conference of Governmental Industrial Hygienists' threshold limit value, time-weighted average of 200 ppm. For samples taken at the end of the shift, the PBPK model predicts 5.1 ppm for breath, 57 mumol/L (4.1 mg/L) for venous blood, and 100 mumol/L (7.2 mg/L) for urine.

Environmental Monitoring↗
PubMedDate not supplied

New PBPK model applied to old occupational exposure to benzene.

An intensive program of benzene monitoring using new techniques was undertaken in Western Europe in the late 1960s and early 1970s. Significant exposure was found in the transport of benzene and gasoline, particularly during the loading of barges, and during the loading and operation of sea-going vessels. The ceiling threshold limit value of 25 ppm recommended at that time generated problems in assessing exposure, so alternative criteria were proposed. During that period some shore-based exposures were reported, and their significance was discussed in several articles. The information gained at that time is reexamined by physiologically based pharmacokinetic (PBPK) modeling and is used to help validate an improved PBPK model, which is described and tested on results from experimental exposure in a companion article. The old field data, comprising five specific studies, confirm the relevance of modeling to assessment of occupational exposure, and demonstrate its value for interpretation of field data, which is seldom as complete, systematic, or accurate as that obtained in experimental work. The model suggests that metabolism of benzene in humans may not be restricted to the liver. Sites and processes of metabolism merit further investigation.

Air Pollutants, Occupational↗
PubMedDate not supplied

Employee exposure to diesel exhaust in the electric utility industry.

The purpose of this study was to assess diesel exhaust exposures in the electric utility industry and to compare these findings with worker exposures reported in other industries and to proposed and established occupational exposure limits. Two sampling approaches were used: particulates were analyzed for elemental (EC) and organic (OC) carbon via the thermal-optical method; and gaseous components (NO2, SO2, NO, and CO) were determined using a direct reading instrument, the Metrosonics pm-7400. Concentrations of the gases were all well within established occupational exposure levels. The EC percentage of the total carbon was generally lower than results reported from other studies resulting in OC levels representing a higher percentage of the total carbon concentrations. Smokers had higher average OC exposure (79 micrograms/m3) than nonsmokers (57 micrograms/m3), but cigarette smoke did not contribute to EC levels in this study (smokers and nonsmokers = 3 micrograms/m3). Two of 120 individual personal exposure levels were found to exceed the proposed threshold limit value of 150 micrograms/m3 for total particulate, but geometric mean levels were found to be significantly less than the proposed value. Questions are raised concerning the use of EC as the sole surrogate for estimating diesel content for comparison with an exposure standard.

Analysis of Variance↗
PubMedDate not supplied

Studies of respiratory morbidity in rubber workers. Part IV. Respiratory morbidity in talc workers.

Pulmonary function tests, chest x-rays, and respiratory questionnaires were administered to eighty talc workers and 189 non-exposed rubber workers from three rubber tire manufacturing plants. The talc workers, who were exposed to talc at levels below the current threshold limit value (TLV) of 20 mppcf for nonfibrous talc, had a statistically significantly greater prevalence of productive cough and of positive criteria for chronic obstructive lung disease (COLD) than did the control workers. The talc workers with more than 10 years of exposure had significantly decreased residual FEV 1.0. Multiple regression analysis of FEV 1.0 in the talc workers estimated that each year of exposure to talc dust reduced the FEV 1.0 by 26 ml. Talc workers had a clear increase in respiratory morbidity, despite the absence of chest roentgenographic changes. Based on this study, a safe exposure level for talc appears to be 25 mg/m3 as a time-weighted average.

Bronchitis↗
PubMedDate not supplied

Evaluation of outdoor air quality in rural and urban communities.

A year-round air monitoring program for sulfur dioxide, sulfates, nitrogen dioxide, nitrates, ozone, and total suspended particulates was conducted in three towns with population densities ranging from 29/km2 to 1178/km2. The results showed significant differences in concentrations of several pollutants between the urban town and the two rural towns. However, site-to-site variation over distances of 1 mile or less within the urban area was considerable. To express pollutant loads in each town in a single number, we calculated a combined pollutant index on premises similar to those used for combined occupational exposures, but with U.S. primary air quality standards rather than threshold limit values as indices of minimal health effects. The combined index exceeded unity in all three towns, suggesting either that total pollutant loads may be excessive even in the sparsely populated town of Lebanon, Connecticut, or, more likely, that the U.S. primary air quality standards have been set at low levels without due regard for additive effects.

Air Pollutants↗
PubMedDate not supplied

Comparison of the sensory irritation response in mice to chlorine and hydrogen chloride.

Groups of male Swiss-Webster mice were exposed to concentrations of chlorine varying from 0.7 to 38.4 ppm and to concentrations of hydrogen chloride varying from 40 to 943 ppm. The total exposure time to both gases was 10 minutes. Dose-response curves were plotted for both chlorine and hydrogen chloride, using the percentage decrease in respiratory rate during each exposure as the response reflecting sensory irritation of the upper respiratory tract. The results showed chlorine to be 33.0 times more irritating than hydrogen chloride, with 95% confidence limits of 18.6 and 57.1. Guidelines for obtaining a range of acceptable threshold limit values (TLV) based on sensory irritation of the upper respiratory tract are discussed. It was concluded that the current TLV of 1 ppm for chlorine is the upper acceptable limit, and that the established TLV of 5 ppm for hydrogen chloride lies at the lower limit of the predicted range. The mechanism of chlorine's and hydrogen chloride's sensory irritation may be explained by their reaction with various functional groups in the membranes of the trigeminal nerve endings lining the nasal mucosa.

Animals↗
PubMedDate not supplied

Induced rhinovirus infection under controlled exposure to sulfur dioxide.

The interaction between short-term sulfur dioxide (SO2) exposure and experimentally induced rhinovirus infection was studied in thirty-two volunteers divided into two groups balanced with respect to age, antibody levels, and nasal mucus flow rates. One group was exposed to SO2 exposure at the threshold limit value (TLV) of 5 ppm during 4 hours; the other group served as controls exposed to pollution-free air under the same conditions. The SO2 exposure caused a 50% decrease in nasal mucus flow rate in the anterior parts of the nose, but there was no difference in the number of colds which developed in the two groups. The group exposed to SO2 had fewer symptoms and a possibly shorter incubation period (P = .06), and virus shedding was at a lower level but more persistent than in the control group. No differences were found in antibody response. The rhinovirus infection in the control group caused a gradual decrease in nasal mucus flow rate starting 2 days after the virus instillation, and after 5 days the rate was less than half its initial value. For future experiments on the interaction between airborne pollutants and rhinovirus infections, a virus challenge by aerosol inhalation is recommended. Our study supports an earlier observation that growth of influenza virus in the nasal cavity of mice was inhibited by exposure to SO2 concentrations of 6 or 20 ppm.

Adolescent↗
PubMedDate not supplied

Effect of TLV levels of SO2 and H2 SO4 on bronchial clearance in exercising man.

Pulmonary mucociliary function was assessed following exposure to industrial threshold limit values (TLV) of sulfur dioxide (5 ppm) SO2) and sulphuric acid mist (1 mg/m3 H2SO4). Bronchial clearance was measured in two sets of ten healthy exercising non-smoking adults under control and exposure conditions. A 99mTc-albumen saline aerosol (MMD 3 micrometer) was inhaled as a bolus in late inspiration under controlled conditions to produce reproducible deposition in large airways. Lung retention of radioactivity was quantified using a gamma camera and computer analysis. Clearance was significantly faster (P less than .05) on exposure to both SO2 and H2SO4 compared to control values. Maximum mid-expiratory flow rates (MMFR) were significantly reduced (P less than .01) on exposure to SO2 (mean decrease 8.5%), but only slightly reduced for H2SO4 (1.4%). The speeding in clearance was probably an irritant response in both cases. For SO2 the response appeared predominantly reflex, while H2SO4 showed evidence of a direct effect.

Adult↗