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PubMed1980

Exposure to mercury and silver during removal of amalgam restorations.

The content of particulate matter and mercury vapor in dentist breathing air during removal of amalgam restorations was assessed. Mercury and silver were quantitatively assayed by nuclear chemical analysis, and the mercury vapor concentration was measured with a sniffer. When the water spray was not used, the short time threshold limit values for exposure to mercury and silver were exceeded about 10 times. With water spray the mercury content was reduced to a level considerably lower than the threshold limit value, whereas the silver concentration slightly exceeded the corresponding limit.

Dental Amalgam↗
PubMed2003

[Follow-up examination of Danish stainless steel welders previously examined in 1987].

INTRODUCTION: A Danish cohort from 1987 consisting of 226 stainless steel welders and reference persons is part of the European Study Group on Cytogenetic Biomarkers and Health (ESCH). In ESCH increased cancer morbidity and mortality was significantly associated with high levels of chromosomal aberrations, measured in blood samples several years prior to cancer registration. The positive association was found in two cohorts from the Nordic countries and from Italy. MATERIAL AND METHODS: ESCH followed all registered cancer cases and control persons by questionnaires and interviews to obtain information about exposures in the period from the time of blood sampling for chromosomal aberration analysis to the time of cancer diagnosis. In Denmark the total cohort was included in the inquiry and the ESCH questions were supplemented with questions from the Danish National Work Environment Cohort Study 1990-95. RESULTS: Responses from one hundred and forty-four persons showed that seventy-four were employed at the same workplace place as in 1987. Differences in occupational exposures, such as more noise, heat and insufficient lighting and no differences in the self-rated health were found in comparison with the Danish National Work Environment Cohort Study as such and with the sample of metal workers. Only very few of the study persons knew the threshold limit value of welding fumes but a majority found that the working environment had improved during the past ten years. DISCUSSION: This study confirms hazardous exposures in stainless steel welding. The threshold limit value, however, has been lowered since 1987 suggesting there is less cancer risk today from stainless steel welding.

Air Pollutants, Occupational↗
PubMed1981

Dust in workroom air of dental laboratories.

The general workroom air of eleven dental laboratories has been surveyed with respect to dust levels arising from cutting, grinding or polishing various dental materials like chromium-cobalt-, nickel- or gold alloys, amalgam and gypsum models, porcelain or denture base material. The materials were processed with cut or lathe wheels and various stones. The levels of the elements aluminium, calcium, cobalt, copper, chromium, gold, iron, lead, magnesium, manganese, nickel, silicon, silver, tin or titanium present in the collected dust samples did not exceed the respective threshold limit values. The dust was collected in workrooms with good general ventilation as well as in rooms with no use of ventilation systems. However, in breathing air close to workpiece, i.e. at distances of about 30 cm, threshold limit values for several elements or compounds could be considerably exceeded. The chemical analysis was accomplished by means of optical emission spectrography.

Air Pollutants↗
PubMed1981

Levels of methylmethacrylate, formaldehyde, and asbestos in dental workroom air.

The levels of methylmethacrylate and formaldehyde in workroom air of a dental laboratory following finishing and polishing a pour type denture base resin have been measured. The levels of these compounds did not exceed the respective hygienic threshold limit values in the general workroom air or in breathing air close to workpiece. The content of asbestos fibers in breathing air released during dismantling molds from gold casting was measured. During the dismantling procedure the fiber content in the air could exceed threshold limit values by up to about 12 times. However, about 10 min after terminating this process the fiber content had declined to a level below the establish requirements.

Air Pollutants↗
PubMed2005

Evaluation of occupational hazards in foundries.

The working environment of foundries is hazardous and characterized by multiple simultaneous chemical, physical and mechanical hazards exposure, which would lead to injuries of foundry workers. The aim of the present work is to evaluate occupational hazards in four foundries, two in Alexandria: El Nasr and Ramsis, and two in Behira: Misr Spinning and Weaving and Misr Rayon companies. Levels of total and respirable dust, free silica % in total dust and lead concentration in total and respirable dust; NO2, SO2 and CO concentrations; noise and heat stress levels have been determined in the present work. Occupational injuries data were analyzed in a three years period from 1998 to 2000. The results of the present work revealed; 1. The levels of total dust and respirable dust exceeded the threshold limit values at knockout and cleaning operations at El Nasr Company. 2. Free silica percentage exceeded permissible levels in all operations except pouring in El Nasr Company. 3. CO levels in Misr Spinning and Weaving Company were higher than threshold levels. 4. Noise levels in knockout and cleaning operations at the four companies were exceeding the threshold limit values. 5. Heat stress levels in melting and pouring operations in El Nasr and in pouring operation in Ramsis Company were higher than the maximum permissible levels. 6. The age group 31-40 years has recorded the highest average incidence rate of injuries of age groups (P<0.01). 7. Lower extremities and higher extremities have recorded the highest average incidence rate in the four companies (P<0.001-P<0.01 respectively). 8. Transportation and lifting was the main cause of injury in the four companies (P<0.05). 9. Faulty action and striking against was the main mean of injury in the four companies (P<0.01). 10. Ramsis Company has the highest average incidence rate in almost all injuries parameters and indices (frequency rate and severity rate) (P<0.05-P<0.001). The present work is a massive survey, which highlights the occupational hazards in Egyptian foundries.

Accidents, Occupational↗
PubMed2003

The beryllium "double standard" standard.

Brush Wellman, the world's leading producer and supplier of beryllium products, has systematically hidden cases of beryllium disease that occurred below the threshold limit value (TLV) and lied about the efficacy of the TLV in published papers, lectures, reports to government agencies, and instructional materials prepared for customers and workers. Hypocritically, Brush Wellman instituted a zero exposure standard for corporate executives while workers and customers were told the 2 microgram standard was "safe." Brush intentionally used its workers as "canaries for the plant," and referred to them as such. Internal documents and corporate depositions indicate that these actions were intentional and that the motive was money. Despite knowledge of the inadequacy of the TLV, Brush has successfully used it as a defense against lawsuits brought by injured workers and as a sales device to provide reassurance to customers. Brush's policy has reaped an untold number of victims and resulted in mass distribution of beryllium in consumer products. Such corporate malfeasance is perpetuated by the current market system, which is controlled by an organized oligopoly that creates an incentive for the neglect of worker health and safety in favor of externalizing costs to victimized workers, their families, and society at large.

Air Pollutants, Occupational↗
PubMed1981

Occupational asthma in a factory making flux-cored solder containing colophony.

The prevalence of work-related wheeze and breathlessness was measured in factory employees manufacturing flux-cored solder. The flux contained colophony which was heated in the production process, exposing the workers to colophony fumes. Measurement of colophony in the breathing zone defined three grades of exposure with median levels of 1.92 mg/m3 (six subjects), 0.02 mg/m3 (14 subjects), and less than 0.01 mg/m3 (68 subjects). All but two workers in the first two groups, and 90% of a random sample of the last group, were studied. Occupational asthma was present in 21% of the higher two exposure groups and 4% of the lowest exposure group. Mean values of FEV1 and FVC fell with increasing exposure. The prevalence of upper and lower respiratory symptoms was only one-third to a half that found in a previous study of shop floor electronics workers, whose work raised the flux to a higher temperature and produced higher concentrations of colophony fume. Total IgM levels were higher in the solder manufacturers than in unexposed controls, and were higher still in the electronics workers. The solder manufacturers were exposed to colophony fumes at 140 degrees C, below the temperature at which the resin acids decompose, supporting the hypothesis that it is the whole resin acids rather than decomposition products which cause occupational asthma. The threshold limit value should be based on the resin acid content of the fume, and not the aldehyde content as at present. The survey suggests that sensitisation will not be prevented unless exposure is kept well below the present threshold limit value.

Adult↗
PubMed1993

n-hexane polyneuropathy in Japan: a review of n-hexane poisoning and its preventive measures.

n-Hexane is used in industry as a solvent for adhesive, dry cleaning, and vegetable oil extraction. In 1963, the first case of severe polyneuropathy suspected to be caused by n-hexane was referred to us. Case studies, animal experiments, and field surveys on n-hexane poisoning were conducted, and preventive measures like threshold limit value revision and biological monitoring were also studied. I review a brief history of our investigations on n-hexane poisoning and its preventive measures in Japan. n-Hexane could cause overt polyneuropathy in workers exposed to more than 100 ppm time-weighted average concentrations [TWA]. The present threshold limit value of 40 ppm in Japan is considered low enough to prevent subclinical impairment of peripheral nerve caused by n-hexane. Urinary 2,5-hexanedione could be a good indicator for biological monitoring of n-hexane exposure. About 2.2 mg/liter of 2,5-hexanedione measured by our improved method corresponds to exposure of 40 ppm (TWA) of n-hexane.

Animals↗
PubMed1998

Exposure-response relationships of occupational inhalative allergens.

Only a few threshold limit values exist at present for allergens in the workplace known to cause bronchial asthma. This contrasts with the great number of occupational asthma cases observed in industrialized countries. Recently published studies provide clear evidence for exposure intensity response relationships of occupational allergens of plant, microbiological, animal or man-made origin. If allergen exposure levels fall short of determined limit values, they are not associated with an increased risk of occupational asthma. Corresponding data are available for wheat flour (1-2.4 mg/m3), fungal alpha-amylase (0.25 ng/m3), natural rubber latex (0.6 ng/m3), western red cedar (0.4 mg/m3) and rat allergens (0.7 microg/m3). It is suggested to stipulate legally binding threshold limit values (TLV/TWA) on this basis in order to induce more effective primary preventive measures. If no reliable data on the health risk of an occupational airborne noxa exist, the lowest reasonably practicable exposure level has to be achieved. Appropriate secondary preventive measures have to be initiated in all workplaces contaminated with airborne allergens. Verified exposure-response relationships provide the basis for risk assessment and for targeted interventions to reduce the incidence of occupational asthma also in consideration of cost benefit aspects. 'Occupational asthma is a disease characterized by variable airflow limitation and/or airway hyperresponsiveness due to causes in a working environment. These causes can give rise to asthma through immunological or non-immunological mechanisms. Up to 15% of all asthma cases are of occupational origin or have at least a significant causal occupational factor. According to the New Zealand part of the European Respiratory Health Survey, an increased risk of asthma prevalence was found for several occupations such as laboratory technicians, food producers, chemical workers, plastic and rubber workers. The Spain part of this study comprising 2646 Spanish subjects showed an asthma risk to be attributed to occupational exposures between 5 and 6.7%. Main asthma-inducing agents in the workplace are flour, grain and feed dust, animal dander/urinary proteins and isocyanates. Further, several inhalative irritants such as chlorine, acid or alkaline aerosols play a pivotal role. Many low molecular weight chemicals have irritative as well as allergenic effects on the airways, e. g. isocyanates and acid anhydrides. In addition to chronic or repetitive exposures, also singular accidental exposure to high concentrations of irritative or toxic airborne substances can cause occupational asthma. This condition is frequently called reactive airways dysfunction.

Allergens↗
PubMed1980

Dust in dental laboratories. Part III: Efficiency of ventilation systems and face masks.

The efficiency of local and electrostatic ventilation systems installed in dental laboratories has been measured. With local exhaust systems, dust amounts could be reduced in breathing air close to the emission source to levels lower than threshold limit values for various elements or compounds in dust produced through cutting, grinding, or polishing various dental materials such as chromium-cobalt, nickel, or gold alloys, porcelain, gypsum models, or denture base material. However, the local exhaust system did not enable a dust reduction from handling amalgam dies consistent with criteria of threshold limit values for mercury and silver. The efficiency of electrostatic filters installed in dental laboratories for general ventilation purposes was found to range from 37% to 73% based on weight reduction. Various ventilation systems with bag filters possessing a high efficiency based on weight reductions allowed small, respirable particles less than 5 micrometers to recirculate within the working environment. The efficiency of face masks for the reduction of inhaled dust revealed efficiencies for two commercial masks ranging from 70% to 95% based on weight reduction. However, such masks only partly retained the respirable dust.

Air Movements↗
PubMed1999

Neuropsychological function in solvent-exposed South African paint makers.

Neuropsychological and neurological function were investigated in 228 organic solvent exposed paint manufacturing workers in two factories. Solvent exposure was expressed as both American Conference of Governmental Industrial Hygienists 1990 Threshold Limit Value equivalents and total hydrocarbon parts per million. The World Health Organization (WHO) neurobehavioral core test battery, the Neurobehavioural Evaluation System--2 (NES-2), and the UNISA Neuropsychological Assessment Procedure (UNAP) were used to measure outcomes, and a Vibratron II was used to measure peripheral vibration sensation. Exposures were generally below the Threshold Limit Value, and no exposure effect was found. Possible explanations for this finding are discussed, including low exposure, exposure, and outcome misclassification, together with inappropriateness, nonvalidity, and relative insensitivity of neuropsychological tests. Only age predicted Vibratron score. Some tests were clearly inappropriate for use in developing countries. Neuropsychological tests were sensitive to educational level, age, alcohol consumption, and cultural indicators. The WHO tests in particular showed good construct validity for neuropsychological functions and should be more formally validated for use in developing countries. Nevertheless, a major problem of cultural dependence is evident for all neuropsychological tests used in this study, and methods for bypassing this problem in less developed settings are discussed.

Adult↗
PubMed1979

Biomonitoring of industrial styrene exposures.

Worker exposure to styrene in two fiberglass boat plants was evaluated using conventional sampling techniques. The use of expired air and urine metabolite concentrations as indicators of styrene exposure is evaluated. The concentration of mandelic acid, a styrene metabolite in urine, is quantitated for workers without and with intermittent personal respiratory protection. A urinary Biological Limit Value is determined for exposures to the Threshold Limit Value of styrene.

Adult↗
PubMed1995

The dentist's exposure to elemental mercury vapor during clinical work with amalgam.

Continuous measurements of mercury vapor in the breathing zone of the dentist were made under ordinary clinical conditions. Fifty old amalgam fillings were removed and replaced by new ones. The mercury vapor measurements were performed by means of atomic absorption spectrophotometry. On the basis of the type of suction device used, the measurements were divided into seven groups, each of which consisted of a series of measurements. During the cutting, filling, and polishing operations the mean mercury vapor levels in the breathing zone of the dentist were in the range of 1-2 micrograms Hg m-3 air when proper mercury hygiene measures were taken. This is far below the currently valid threshold limit value (30 micrograms Hg m-3 air) in Sweden. The saliva extractor and the dental mirror-evacuator did not influence the mercury vapor levels when used together with the high-volume evacuator. However, when only a saliva extractor was used, the cutting of amalgam fillings caused highly fluctuating mercury vapor levels, which were 2-15 times higher than the threshold limit value.

Air Pollution, Indoor↗
PubMed1995

Decline in annual lung function in workers exposed to asbestos with and without pre-existing fibrotic changes on chest radiography.

OBJECTIVES: To examine whether or not workers with pre-existing mild pulmonary fibrosis have accelerated decline in forced expiratory volume in one second (FEV1) or forced vital capacity (FVC), under low level exposure to chrysotile asbestos. METHODS: All male workers in two asbestos manufacturing factories were followed up annually for six years to compare their declines in FEV1 and FVC. The values of FEV1 and FVC were divided by the square of the person's height to adjust for body size differences (FEV1/Ht2 and FVC/Ht2, respectively). Annual change was calculated for each subject as a slope of the simple linear regression with FEV1/Ht2 or FVC/Ht2 regressed according to age. Analysis was conducted on 242 middle aged workers who had normal routine spirometry values, normal chest radiographs or mild pneumoconiosis up to 1/2 grade, without changes either in smoking habit or severity of pneumoconiosis during the study period, and with acceptable spirograms in three or more surveys. The occupational environment, in terms of chrysotile asbestos, had been well controlled below the threshold limit value of Japan at that time--namely, 2 fibres/micromilligrams. RESULTS-There was no significant effect from the interaction between pre-existing mild pulmonary fibrosis and low level of exposure to chrysotile asbestos on the accelerated annual decline of FEV1/Ht2, or FVC/Ht2. Fibrosis significantly contributed to annual changes in FEV1/Ht2, even after adjustment for mean FEV1 and smoking. The point estimate of the contribution was - 4.9 ml/m2/y. No significant independent contribution of exposure was found in decline of either FEV1/Ht2 or FVC/Ht2. CONCLUSIONS: Pre-existing pulmonary fibrosis is an independent risk factor for accelerated annual decline of FEV1, even when mild and stable. Additional decline due to exposure to chrysotile asbestos is less probable if it is well controlled under the current threshold limit value.

Adult↗
PubMedDate not supplied

Occupational exposure to ethylene oxide: effects and control.

Ethylene oxide (EO) is widely used in the health care industry as a gas sterilant for medical products that cannot withstand the high temperature and humidity associated with conventional steam sterilization. As a consequence, approximately 100,000 health care workers are exposed to residual EO each year. The acute toxicity of exposure to EO has been well documented, and recent concern about the mutagenic potential of occupational exposure to EO has resulted in an effort to further reduce workplace exposure levels to EO. The Environmental Protection Agency has issued a rebuttal presumption against registration of EO as a pesticide and the American Conference of Governmental Industrial Hygienists (ACGIH) has proposed a sharp reduction in the threshold limit value permitted for EO. Recognizing the need for environmental health personnel to become more familiar with this workplace hazard, it is appropriate to briefly review the toxic effects of acute and chronic exposure to EO residuals. The authors describe a gas sterilization system successfully utilized at the U.S. Public Health Service Hospital in New Orleans, La., which has demonstrated exposure concentrations well below the EO threshold limit value recently proposed by the ACGIH, while preserving the principal goal of assuring the sterility of reusable medical products which cannot be subjected to steam sterilization.

Central Supply, Hospital↗
PubMed1992

Concentrations of tetrachloroethene in blood and trichloroacetic acid in urine in workers and neighbours of dry-cleaning shops.

Tetrachloroethene concentrations in blood and trichloroacetic acid concentrations in urine were determined--primarily over the course of a week--for 29 persons living in the vicinity of dry-cleaning shops. The mean levels of tetrachloroethene increased during the week. In some neighbours concentrations were exceeding the German biological threshold limit value for tetrachloroethene (1000 micrograms/l blood), persisting over the whole week in one case. The concentrations of tetrachloroethene in blood depended on the floor and the construction type of the building where these people were living, but not of the type of system used in the dry-cleaning shops. 5 of 12 dry-cleaners were found to have tetrachloroethene levels exceeding the German biological threshold limit value, some of them by a considerable amount.

Environmental Exposure↗
PubMed1998

Comprehensive evaluation of long-term trends in occupational exposure: Part 1. Description of the database.

OBJECTIVES: To conduct a comprehensive evaluation of long term changes in occupational exposure among a broad cross section of industries worldwide. METHODS: A review of the scientific literature identified studies that reported historical changes in exposure. About 700 sets of data from 119 published and several unpublished sources were compiled. Data were published over a 30 year period in 25 journals that spanned a range of disciplines. For each data set, the average exposure level was compiled for each period and details on the contaminant, the industry and location, changes in the threshold limit value (TLV), as well as the type of sampling method were recorded. Spearman rank correlation coefficients were used to identify monotonic changes in exposure over time and simple linear regression analyses were used to characterise trends in exposure. RESULTS: About 78% of the natural log transformed data showed linear trends towards lower exposure levels whereas 22% indicated increasing trends. (The Spearman rank correlation analyses produced a similar breakdown between exposures monotonically increasing or decreasing over time.) Although the rates of reduction for the data showing downward trends ranged from -1% to -62% per year, most exposures declined at rates between -4% and -14% per year (the interquartile range), with a median value of -8% per year. Exposures seemed to increase at rates that were slightly lower than those of exposures which have declined over time. Data sets that showed downward (versus upward) trends were influenced by several factors including type and carcinogenicity of the contaminant, type of monitoring, historical changes in the threshold limit values (TLVs), and period of sampling. CONCLUSIONS: This review supports the notion that occupational exposures are generally lower today than they were years or decades ago. However, such trends seem to have been affected by factors related to the contaminant, as well as to the period and type of sampling.

Databases, Bibliographic↗
PubMedDate not supplied

Combined effects of noise and styrene on hearing: comparison between active and sedentary rats.

In this study, two investigations were carried out with adult Long-Evans rats exposed to increasing concentrations of styrene. In the first experiment, the hearing of rats, which were forced to walk in a special wheel during the exposure, was compared to that of rats which were sleepy in their cage. The active rats were exposed to styrene concentrations ranging from 300 to 600 ppm, whereas the sedentary rats were exposed from 500 to 1000 ppm for 4 weeks, 5 days per week, 6 hours per day. In the second experiment, designed to evaluate the hearing risks at threshold limit values, active rats were exposed either to a noise having a Leq8h of 85 dB (equivalent level of a continuous noise for a typical 8-h workday), or to 400-ppm styrene or to a simultaneous exposure to noise and styrene. In both experiments, auditory function was tested by auditory-evoked potentials from the inferior colliculus and completed by morphological analyses of the organ of Corti. The results of the first experiment showed that the same amount of styrene-induced hearing loss can be obtained by using concentrations approximately 200 ppm lower in active rats than in sedentary rats. The second investigation showed that, in spite of the low-intensity noise and the low-concentration of styrene, there is a clear risk of potentiation of styrene-induced hearing loss by noise. These findings and exposure conditions were discussed and extrapolated with regard to the risk assessment for human beings. The authors propose to decrease the French threshold limit value of styrene for ensuring a high level of protection for human hearing.

Animals↗