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At least 667 records · Page 37Linked to original sources
PubMed1985

Reduction in levels of volatile N-nitrosamines in rubber nipples for babies' bottles.

Levels of volatile N-nitrosamines were determined in 189 samples of rubber nipples for babies' bottles. Domestic (US-manufactured) and imported rubber nipples for consumer and hospital use were analysed to determine compliance with the US Food and Drug Administration's action level of 60 ppb (b = 10(9] for total volatile N-nitrosamines. Only one sample was found to be in violation of the action level; it contained a total of 137 ppb N-nitrosamines.

Bottle Feeding↗
PubMed1992

Nitrosamines in rubber bands used for orthodontic purposes.

Fourteen samples from eight brands of elastic-rubber bands used in orthodontics were tested for their nitrosamine content. The presence of N-nitrosodibutylamine and N-nitrosopiperidine was confirmed. The potential for nitrosamine formation from accelerating agents used for vulcanization and from other nitrosatable amines, which may be present in rubber exposed to salivary nitrite, justifies further investigations.

Nitrosamines↗
PubMed1996

Leukemia and cumulative exposure to butadiene, styrene and benzene among workers in the synthetic rubber industry.

Retrospective, quantitative estimates of exposure to 1,3-butadiene, styrene and benzene were developed for a follow-up study of leukemia mortality among 16610 subjects employed at six North American styrene-butadiene rubber manufacturing plants (418846 person-years, 58 leukemia deaths). The estimation procedure entailed identifying work areas within each manufacturing process, historical changes in exposure potential and specific tasks involving exposure, and using mathematical models to calculate job- and time-period-specific average exposures. The resulting estimates were linked with the subjects' work histories to obtain cumulative exposure estimates, which were employed in stratified and Poisson regression analyses of mortality rates. Mantel-Haenszel rate ratios adjusted by race, age, and cumulative styrene exposure increase with cumulative butadiene exposure from 1 in the nonexposed category to 4.5 in the category of 80 ppm-years or more (P = 0.01). The risk pattern is less clear and statistically nonsignificant for styrene exposure. A trend of increasing risk with butadiene exposure is still present after exclusion of the nonexposed category (P = 0.03). A parsimonious interpretation of the findings presented here, in light of previous epidemiologic studies, is that exposure to butadiene in the synthetic rubber industry produces a dose-related increase in the occurrence of leukemia.

Benzene↗
PubMed2005

Structural analysis of the glycoprotein allergen Hev b 4 from natural rubber latex by mass spectrometry.

The lecithinase homolog (Hev b 4) from Hevea brasiliensis (Q6T4P0_HEVBR) is an important natural rubber latex allergen. Hev b 4 is a highly glycosylated protein and its carbohydrate moiety has been implicated in the binding of IgE from natural rubber latex allergic patients. The cDNA for Hev b 4 has recently been cloned and sequenced. Here, we have analyzed the post-translational modifications of natural Hev b 4 by liquid chromatography/electrospray ionization-mass spectrometry of tryptic peptides. Seven of the eight potential glycosylation sites were found to be occupied. One site, however, was only partially glycosylated. Asn224 was substituted by complex type N-glycans with fucose and xylose, whereas all other sites carried either oligomannose glycans or a mixture of oligomannose and complex N-glycans. Glycosylation site Asn308, the most C-terminal one of the eight sites, was only found in the non-glycosylated form. The complex type N-glycans apparently form the molecular basis for the immune reaction with patients' sera. A large fraction of Hev b 4 molecules contains two or more complex N-glycans and thus a physiological reaction against these polyvalent allergens on the basis of the carbohydrate is in theory possible. Aside from allowing glycosylation analysis, the mass spectrometric data defined the N-terminal cleavage site of Hev b 4. This study once more demonstrates the outstanding analytical potential of electrospray ionization-mass spectrometry coupled with liquid chromatographic separation.

Allergens↗
PubMed2006

Validation of 1,3-butadiene exposure estimates for workers at a synthetic rubber plant.

PURPOSE: This investigation assessed the validity of estimates of exposure to 1,3-butadiene (BD) developed for a plant included in a study of mortality among synthetic rubber industry workers. The estimates were developed without using historical measurement data and have not been validated previously. METHODS: Personal BD measurements came from an exposure-monitoring program initiated in 1977. For each job, we computed the year-specific difference between the BD estimate and the mean of BD measurements. We also computed rank correlation coefficients and calculated the mean, across all measurements, of the difference between the estimate and the measurement. RESULTS: The mean BD concentration was 5.2 ppm for 4978 measurements and 4.7 ppm for the corresponding estimates. The mean difference between estimates and measurements was -0.50 ppm (standard deviation, 26.5 ppm) overall and ranged from -227.9 to +27.0 ppm among all 306 job/year combinations. Estimates were correlated with measurements for all 306 combinations (rank correlation coefficient, r=0.45, p<0.0001), for 82 combinations pertaining to jobs that were well-defined by a specific set of tasks and typically found in styrene-BD rubber (SBR) plants (r=0.81, p<0.0001), for 70 combinations pertaining to jobs that were well-defined but not typical (r=0.29, p=0.01) and for 92 combinations pertaining to poorly-defined jobs typically found in SBR plants (r=0.56, <0.0001). Estimates were not correlated with measurements for poorly defined jobs not typically found in SBR plants (r=0.01, p=0.93). For well-defined typical SBR jobs with measurement means that were over 7.0 ppm, estimates were consistently lower than measurements. CONCLUSIONS: Possible reasons for differences between estimates and measurements included faulty assumptions used in developing BD estimates, unstable or nonrepresentive measurements and errors in linking measurement data to the job-exposure matrix. Exposure misclassification may have been more severe for subjects from the validation study plant than for subjects from other plants in the mortality study. BD estimates for typical SBR jobs, which comprise most operations at all but one of the plants in the mortality study, appeared to be useful for ranking workers by cumulative exposure. Uncertainty analyses would enhance the utility of the BD exposure estimates for quantitative risk assessment.

Butadienes↗
PubMed1990

Comparison of single rubber-nylon balloon and double polyethylene balloon valvuloplasty in 94 patients with rheumatic mitral stenosis.

To compare the single rubber-nylon balloon and double polyethylene balloon techniques, 94 patients with rheumatic mitral stenosis underwent percutaneous transseptal balloon mitral valvuloplasty between November 1985 and September 1988. The single balloon technique was used in 73 patients and the double balloon technique was used in 21. The two groups were similar in age, weight, severity of the lesion, and cardiac functional status. The mean mitral valve diastolic gradient decreased from 17.9 +/- 6.5 to 2.9 +/- 3.1 mm Hg (p less than 0.001), 18.5 +/- 6.7 to 5.8 +/- 3.1 mm Hg (p less than 0.001), and 18.1 +/- 5.9 to 3.2 +/- 3.7 mm Hg (p less than 0.001) in the single balloon group, double balloon group, and the entire series, respectively. The final mitral diastolic gradient in the single balloon group was lower than in the double balloon group (p less than 0.05). Complications in the single balloon group were lower than in the double balloon group. Additional advantages of single over double balloon technique were easier maneuverability and higher success rate. The initial and long-term follow-up results confirmed the earlier impressions that percutaneous transseptal balloon mitral valvuloplasty is an effective and safe nonsurgical method of treatment for rheumatic mitral stenosis, and the single rubber-nylon balloon technique is at least as effective as, if not superior to, the double polyethylene balloon technique.

Adolescent↗
PubMed2001

Assessment of butadiene exposure in synthetic rubber manufacturing workers in Texas using frequencies of hprt mutant lymphocytes as a biomarker.

1,3-Butadiene (BD), which is used to manufacture synthetic rubber, is a mutagen and carcinogen. Because past occupational exposures have been associated with an increased risk of leukemia, there has been a dramatic reduction in workplace exposure standards. The health benefits of these reduced levels of occupational exposure to BD will be difficult to evaluate using relatively insensitive traditional epidemiological studies; however, biomarkers can be used to determine whether there are genotoxic effects associated with recent exposures to BD. In past studies of BD-exposed workers in Southeast Texas, we observed an increase in the frequency of lymphocytes with mutations in a reporter gene, hprt. Frequencies of hprt mutant cells correlated with air levels of BD and with the concentration of a BD metabolite in urine. Average exposures to 1-3 parts per million (p.p.m.) of BD were associated with a threefold increase in hprt variant (mutant) frequencies (Vfs). We now report results from a follow-up study of workers in a synthetic rubber plant in Southeast Texas. Thirty-seven workers were evaluated on three occasions over a 2-week period for exposure to BD by the use of personal organic vapor monitors and by determining the concentration of a BD metabolite in urine. The frequency of hprt mutants was determined, by autoradiography, with lymphocyte samples collected 2 weeks after the final exposure measurement. Based on their work locations, the study participants were assigned to high-exposure (N=22) or low-exposure (N=15) groups. The BD exposure, +/-standard error, of the workers in the high-exposure group (1.65+/-0.52 p.p.m.) was significantly greater than the low-exposure group (0.07+/-0.03 p.p.m.; P<0.01). The frequency of hprt mutant lymphocytes was also significantly different in the two groups (high, 10.67+/-1.5 x 10(-6); low, 3.54+/-0.6 x 10(-6); P<0.001). The concentration of the urine metabolite was greater in the high-exposure group, but the difference was not significant. The correlation coefficient between hprt Vf and BD exposure levels was r=0.44 (CI(95), 0.11-0.69; P=0.011). This study reproduced the findings from a previous study at this plant. Although studies of butadiene-exposed workers in other countries have not detected an effect of exposure on frequencies of hprt mutant lymphocytes, we have repeatedly observed this result in our studies in Texas.

Air Pollutants, Occupational↗
PubMed2001

Leukemia and exposure to 1,3-butadiene, styrene and dimethyldithiocarbamate among workers in the synthetic rubber industry.

This study evaluated relations between exposure to 1,3-butadiene (BD), styrene (STY) and dimethyldithiocarbamate (DMDTC) and mortality from leukemia among synthetic rubber industry workers. Subjects were 13130 men employed for at least 1 year during 1943-1991 at any of six plants that manufactured synthetic rubber. Death certificates and medical records identified workers with leukemia. Cumulative exposure estimates were based on plant- and time period-specific process and task characteristics, linked to subjects' work histories. Poisson regression estimated relative rates (RRs) for workers exposed to each agent compared to unexposed workers. Leukemia (N=59) was positively associated with BD ppm-years (RRs of 1.0, 1.2, 2.0 and 3.8, for exposures of 0, >0-<86.3, 86.3-<362.2 and 362.2+ ppm-years; only the RR for the highest exposure category was statistically significant), STY ppm-years (RRs of 1.0, 1.2, 2.3 and 3.2, for exposures of 0, >0-<20.6, 20.6-<60.4 and 60.4+ ppm-years; only the RR for the highest exposure category was statistically significant) and DMDTC mg-years/cm (RRs of 1.0, 2.3, 4.9 and 2.9, for 0, >0-<566.6, 566.6-<1395.1 and 1395.1+ mg-years/cm; the RR for each non-zero exposure category was statistically significant) after adjusting for age and years since hire. After further adjusting each agent-specific set of RRs for the other two agents, a positive but imprecise relation remained for BD and DMDTC but not for STY. The association with BD was stronger for ppm-years due to exposure intensities >100 ppm than for ppm-years due to lower concentrations. BD and DMDTC, but not STY, were positively associated with leukemia in multivariable analyses. The independent effect of each agent was difficult to evaluate because of correlations with other agents and imprecision.

Butadienes↗
PubMed1987

High-performance liquid chromatographic identification and determination of dithiocarbamates in vulcanized rubber products.

A method was developed for the high-performance liquid chromatographic determination of dithiocarbamates (DTCs), after conversion of zinc dithiocarbamates into the corresponding cobalt(III) complexes. When shaking a chloroform-acetone extract from a rubber sample with cobalt(II) chloride, mixed-ligand cobalt(III) complexes were often formed because of the coexistence of more than two kinds of zinc dithiocarbamates in the rubber sample. The chromatograms were so complicated that DTCs could not easily be determined in the usual manner. However, it was possible to identify and to quantify DTCs by comparing retention times and relative intensities of the multiple peaks of the cobalt(III) complexes obtained from standard mixtures of zinc dithiocarbamates.

Chromatography, High Pressure Liquid↗
PubMed1989

Determination of non-volatile N-nitrosamines in baby bottle rubber nipples and pacifiers by high-performance liquid chromatography-thermal energy analysis.

A method is described for the determination of non-volatile N-nitrosamines in baby bottle rubber nipples and pacifiers. It consists of extraction of the sample with dichloromethane in the presence of ascorbyl palmitate (an inhibitor of artifactual formation of nitrosamines), clean-up on silica or basic alumina, and final analysis by high-performance liquid chromatography-thermal energy analysis, a technique which is highly specific for N-nitroso compounds. The method worked well for the determination of four rubber-related non-volatile nitrosamines, namely, N-nitrosomethylphenylamine, N-nitrosoethylphenylamine, N-nitrosodicyclohexylamine, and N-nitrosodibenzylamine (recoveries from spiked samples greater than 80%; detection limit, ca. 5 micrograms/kg for each). Eighteen out of twenty four samples analyzed were found to contain varying levels (mean, 41 micrograms/kg; range, 8-146 micrograms/kg) of N-nitrosodibenzylamine. The identity of the compound was confirmed by gas chromatography-thermal energy analysis as well as by gas chromatography-mass spectrometry analyses.

Chromatography, High Pressure Liquid↗
PubMed2002

Optimization of parameters for the supercritical fluid extraction in the determination of N-nitrosamines in rubbers.

The study of the possibilities of supercritical fluid extraction (SFE) with N-nitrosamines in rubbers has been carried out. Home-made materials fortified with several N-nitrosamines were prepared in order to optimize the SFE parameters. A Plackett-Burman design was employed to evaluate the influence of those parameters to be controlled in SFE, such as pressure, temperature, static and dynamic time, restrictor temperature and volume of modifier while CO2 was used as the extraction fluid. An extra central composite design for the main factors (according to the previously obtained results) was also developed in order to refine the best supercritical conditions for the extraction of N-nitrosamines from rubbers. Gas chromatography with a nitrogen and phosphorus sensitive detector was used to achieve sensitivity and limits of detection for the concentrations expected in plastic materials. The proposed analytical method has shown to be useful in the determination of N-nitrosamines even for complex matrices.

Chromatography, Supercritical Fluid↗
PubMed1999

In situ monitoring of the ambient air around the chloroprene rubber industrial plant using the Tradescantia-stamen-hair mutation assay.

The city of Yerevan, the capital of Armenia, has been one of the heavily polluted cities since the earlier USSR era. A Chloroprene Rubber Industrial Plant has been the major contributor of air pollution in this city. The first attempt has been undertaken to detect the mutagenic effect of the ambient air around this industrial complex using the Tradescantia-stamen-hair-mutation (Trad-SHM) assay. Tradescantia clone 02 was used for this study. Pots of Tradescantia plants were exposed to ambient air in 10 different locations around the industrial establishment during the months of May and June, 1991 and 1992. Three series of in situ monitoring experiments were carried out. In the first series, sites numbers 1 through 4 were located in the industrial complex, and the second series, sites numbers 5 through 7 were located 1.0-1.3 km away from the Rubber Plant and the third series, sites numbers 8 though 10 were situated 1.5 km from the chemical plant and the monitoring plants were elevated at 5, 13, and 32 m above ground. A control group of plants were grown in a greenhouse about 13 km away from the polluted air from the chemical plant. Results of these two consecutive year's study show significantly elevated high levels of pink mutation events (PME) over the control at sites 1, 2, and 4 in the first series of the study. Positive responses were observed at all sites in the second series of the study. Only site 8 (June 1991) in the third series of the study was significantly higher in PME over the control.

Air Pollutants, Occupational↗
PubMed1995

One of the rubber latex allergens is a lysozyme.

BACKGROUND: Type I hypersensitivity reactions caused by latex products are ascribed to proteins eluted from them, but little is known about the properties of these allergenic proteins. The reason for the cross-reaction between rubber latex and fruits is also not known. We have speculated that a series of defense-related proteins in plants is a cause of latex allergy and the cross reaction. OBJECTIVE: To verify our hypothesis, we selected a lysozyme as a representative defense-related protein and examined its relationship to latex allergy. METHODS: Lysozymes eluted from latex gloves were detected with a cell-suspension clearing test. A chromatographically separated lysozyme was investigated for its physicochemical and enzymatic properties and allergenicity. RESULTS: Lysozyme activity was detected in extracts from ammoniated latex and latex gloves. We separated a lysozyme (27 kd; isoelectric point, 9.5) using cation-exchange and gel filtration chromatography. This lysozyme was enzymatically very similar to fruit lysozymes and was demonstrated to be an allergen. CONCLUSIONS: One of the rubber latex allergens is a lysozyme that has similarities to fruit lysozymes. This suggests the relevance of defense-related proteins to latex allergy and the cross reaction.

Adult↗
PubMed1995

Manipulation of rubber dam septa: an aid to the meticulous isolation of splinted prostheses.

Splinted prostheses are a problem in endodontic isolation. The traditional solution of resorting to a slit-dam technique results in an unrestrained curtain of rubber dam which not only allows for saliva seepage but can serve to compromise the endodontic access opening. This article introduces a simple, yet effective, method of improving the seal of isolated splinted prostheses. It relies on the manipulation and ligation of rubber dam septa with dental floss. Two pictorial clinical reports depict the technique and demonstrate the ease of attaining isolation with splinted prostheses.

Child↗
PubMed1997

Improvement of the rubber dam frame.

An improvement of the rubber dam frame for obtaining the endodontic operative field is proposed. The device consists of an articulated frame that maintains the currently used standard rubber dam sheet in position. A hinge allows the frame to be folded, resulting in easier accessibility to the working area. This accessibility facilitates taking of radiographs, administration of additional doses of anesthetics, and evacuation of therapeutic liquids, which may have accidentally entered the buccal cavity. In addition, a reservoir at the bottom of the frame allows the placement of gauze compresses and an aspiration cannula to avoid leakage of fluids such as sodium hypochloride onto the patient's clothing.

Biocompatible Materials↗
PubMed1983

Injuries caused by plastic bullets compared with those caused by rubber bullets.

The injuries sustained by 99 people struck by plastic bullets, were compared with those sustained by 90 people struck by rubber bullets. Plastic bullets struck the head and chest less often than rubber bullets and caused fewer serious injuries to the face and chest, but tended to cause more serious skull and brain injuries.

Adult↗
PubMed1996

Rubber band constriction of the wrist.

We report the effects of rubber bands placed as decorative bands around the wrists of two infants by older children. These bands went unnoticed by their parents for several hours until swelling of the hand occurred. Early decompression of the carpal tunnel and fasciotomy of the dorsum of the hand are recommended. Education of the community is important in avoiding complications from placement of these rubber bands around an extremity.

Carpal Tunnel Syndrome↗
PubMed1999

Toxicity study of a rubber antioxidant, mixture of 2-mercaptomethylbenzimidazoles, by repeated oral administration to rats.

2-Mercaptobenzimidazole (2-MBI), a rubber antioxidant, is known to exhibit potent antithyroid toxicity in rats and is a candidate as an environmental endocrine disrupter. 2-Mercaptomethylbenzimidazoles (a 1:1 mixture of 4-methyl and 5-methyl isomers, MMBIs), are also employed industrially as rubber antioxidants and are suspected to exert antithyroid toxicity such as 2-MBI. In this investigation, acute and subacute oral toxicity studies of MMBIs in Wistar rats were conducted. The clinical signs of acute oral toxicity were observed including decreased spontaneous movement, a paralytic gait, salivation and lacrimation, and adoption of prone and lateral positions. The LD50 was estimated to be 330 mg/kg. In the subacute oral toxicity study, male and female rats were treated with MMBIs by gavage at doses of 0 (corn oil), 4, 20 and 100 mg/kg for 28 consecutive days followed by a 2-week recovery period for the control and highest dose groups. Body weight and food consumption, clinical signs, organ weights, clinical biochemistry and haematological parameters including clotting times and micronuclei induction in bone marrow erythropoeitic cells, and histopathology were examined. Relative organ weights of lung, liver and kidney, and serum cholesterol and phospholipid significantly increased in male rats treated with MMBIs at doses of 20 and 100 mg/kg. Male rats administered 100 mg/kg MMBIs exhibited a 1.8-fold increase in thyroid weight associated with histopathological changes but not altered serum thyroid hormone levels. Female rats administered 100 mg MMBIs/kg exhibited significant increases of liver and kidney but not thyroid weights, and serum cholesterol level. The antithyroid toxicity of MMBIs in rats was estimated to be one-tenth that of 2-MBI. No-observed-effect levels for male and female rats were found to be 4 and 20 mg/kg, respectively, in this subacute oral toxicity study.

Animals↗