Field protection effectiveness of chemical protective suits and gloves evaluated by biomonitoring

OBJECTIVES

To determine the effectiveness of protective suits and gloves by biomonitoring.

METHODS

Fifteen male spray painters at a ship coating factory were studied for two weeks. Workers wore no protective clothing during the first week and wore protective suits and gloves during the second week. Sampling was conducted on four consecutive working days each week. Ethyl benzene and xylene in the air were collected by using 3M 3500 organic vapour monitors. Urine was collected before and after each work shift.

RESULTS

Urinary mandelic acid (MA) and methyl hippuric acid (MHA) levels were divided by the personal exposure concentrations of ethyl benzene and xylene, respectively. Mean (SE) corrected MA and MHA concentrations in the first week were 1.07 (0.18) and 2.66 (0.68) (mg/g creatinine)/(mg/m3), and concentrations in the second week were 0.50 (0.12) and 1.76 (0.35) (mg/g creatinine)/(mg/m3) in the second week, respectively. Both MA and MHA concentrations in the second week (when spray painters wore protective suits and gloves) were lower than in the first week, respectively (p<0.001, p = 0.011). Mean decrease in MA and MHA biomarkers were 69% and 49%, respectively.

CONCLUSION

This study successfully evaluated the effectiveness of chemical protective suits and gloves by using biomarkers as urinary MA and MHA. This method is feasible for determining the performance of workers wearing personal protective equipment. Moreover, the experimental results suggest that dermal exposure may be the major contributor to total body burden of solvents in spray painters without protective suits and gloves.

Evaluation of the effectiveness of personal protective equipment against occupational exposure to N,N-dimethylformamide

The objectives of this study were to evaluate the protective effectiveness of various personal protective equipment and the respective exposure contributions from respiratory and skin exposures of N,N-dimethylformamide (DMF) with a self-comparison study design. Two high-, four intermediate- and four low-DMF exposure workers from a synthetic leather factory were monitored in airborne DMF concentrations and N-methylformamide (NMF) concentrations in urine across four consecutive days. The workers were designated to wear no personal protective equipment on the first day. The barrier cream, rubber gloves and rubber gloves plus respirator were used on the second, third and fourth days, respectively. Person-to-personal observation was performed in the field to record all high and low exposure tasks during work for each subject. Protective effectiveness index (PEI) was used to evaluate different glove effectiveness. We concluded that the direct skin contact to the strong skin penetrates like DMF could be a more significant exposure source than the respiratory exposure in the actual occupational environment. The provision of protective equipment from skin exposure could be more important than that from respiratory exposure. The application of barrier cream could be as effective as wearing impermeable rubber gloves in the prevention from the skin penetrate in the occupational settings.

Development and Evaluation of an Air-Curtain Fume Cabinet with Considerations of its Aerodynamics

In order to avoid the inherent aerodynamic difficulties of the conventional fume hood, an innovative design--the 'air curtain-isolated fume hood' is developed. The new hood applies a specially designed air curtain (which is generated by a narrow planar jet and a suction slot flow at low velocities) across the sash plane. The hood constructed for the study is full size and transparent for flow visualization. The aerodynamic characteristics are diagnosed by using the laser-light-sheet-assisted smoke flow visualization method. Four characteristic air-curtain flow modes are identified in the domain of jet and suction velocities when the sash remains static. Some of these characteristic flow modes have much improved flow patterns when compared with those of the conventional fume hoods. From the viewpoint of the aerodynamics and mass transport, the results indicate that the air curtain properly setup across the sash opening allows almost no sensible exchange of momentum and mass between the flowfields of the cabinet and the outside environment. Two standard sulfur hexafluoride (SF6) tracer gas concentration measurement methods following the ANSI/ASHRAE 110-1995 standard and the prEN14175 protocol for static test are employed to examine the contaminant leakage levels. Results of the rigorous examinations of leakage show unusually satisfactory hood performance. The leakage of the tracer gas can approach almost null (<0.001 p.p.m.) if the jet and suction velocities are properly adjusted.

Exposure to traffic exhausts and oxidative DNA damage

AIMS

To assess the relations between exposure to traffic exhausts and indicators of oxidative DNA damage among highway toll station workers.

METHODS

Cross-sectional study of 47 female highway toll station workers exposed to traffic exhausts and 27 female office workers as a reference group. Exposure assessment was based on average and cumulative traffic density and a biomarker of exposure, urinary 1-hydroxypyrene-glucuronide (1-OHPG). Urinary 8-hydroxydeoxyguanosine (8-OHdG) was used as a biomarker of oxidative DNA damage. Plasma nitric oxide (NO) was measured as an indicator of oxidative stress related to traffic exhaust exposure.

RESULTS

The mean concentration of urinary 8-OHdG was substantially higher among the exposed non-smokers (13.6 microg/g creatinine) compared with the reference non-smokers (7.3 microg/g creatinine; difference 6.3, 95% CI 3.0 to 9.6). The mean concentration of NO among the exposed (48.0 micromol/l) was also higher compared with the reference non-smokers (37.6 micromol/l; difference 10.4, 95% CI -0.4 to 21.2). In linear regression adjusting for confounding, a change in log(8-OHdG) was statistically significantly related to a unit change in log(1-OHPG) (beta = 0.372, 95% CI 0.081 to 0.663).

CONCLUSIONS

Results indicate that exposure to traffic exhausts increases oxidative DNA damage. Urinary 8-OHdG is a promising biomarker of traffic exhaust induced oxidative stress.

Total body burden arising from a week's repeated dermal exposure to N,N-dimethylformamide

BACKGROUND

Hazardous chemicals and their metabolites may accumulate in the body following repeated airborne exposures and skin contact.

AIMS

To estimate the contribution of skin absorption to total body burden of N,N-dimethylformamide (DMF) across a working week in two groups with similar levels of respiratory exposure but dissimilar skin contact.

METHODS

Twenty five workers in a synthetic leather (SL) factory, 20 in a copper laminate circuit board (CLCB) factory, and 20 age and sex matched non-DMF exposed subjects, were recruited. Environmental monitoring of DMF exposure via respiratory and dermal routes, as well as biological monitoring of pre-shift urinary N-methylformamide (U-NMF), were performed for five consecutive working days.

RESULTS

Environmental and biological monitoring showed no detectable exposure in controls. The average airborne DMF concentration (geometric mean (GM) 3.98 ppm, geometric standard deviation (GSD) 1.91 ppm), was insignificantly lower for SL workers than for CLCB workers (GM 4.49, GSD 1.84 ppm). Dermal DMF exposure and U-NMF values, however, were significantly higher for SL workers. A significant pattern of linear accumulation was found across a five day work cycle for SL workers but not for CLCB workers.

CONCLUSIONS

Dermal exposure to DMF over five consecutive days of occupational exposure can result in the accumulation of a significant DMF body burden. The long term exposure response under both repeated and intermittent conditions of substantial skin exposure is worthy of note.

Aerodynamic Characteristics and Design Guidelines of Push–Pull Ventilation Systems

Aerodynamic characteristics such as the flow patterns, velocity field, streamline evolutions, characteristic flow modes and characteristic flow regimes of the push-pull ventilation system are cross-examined by using the laser-light sheet smoked-flow visualization method and laser Doppler velocimetry. Four characteristic flow modes, which are denoted as dispersion, transition, encapsulation and strong suction, are identified in the domain of the push-jet and pull-flow velocities at various open-surface tank widths and rising gas velocities. It is argued phenomenologically, from the aerodynamic point of view, that operating the system in the strong suction regime would be a better strategy than operating it in other characteristic regimes for the consideration of capture efficiency. Design guidelines are developed and summarized based on the results obtained from this study. The regression formulas for calculating the critical values of the push-jet and the pull-flow velocities are provided for easy access. The sulfur hexafluoride tracer gas validation technique is performed to measure the capture efficiency. The results of tracer gas validations are consistent with those obtained from the aerodynamic visualization and measurements. The operation points obtained by employing the American Conference of Governmental Industrial Hygienists design criteria are compared with the results obtained in this study for both the aerodynamics and the capture efficiency. Methods for improving the capture efficiency and energy consumptions are suggested.

Evaluation of the protective effectiveness of gloves from occupational exposure to 2-methoxyethanol using the biomarkers of 2-methoxyacetic acid levels in the urine and plasma

AIMS

To evaluate the protective effectiveness of gloves from occupational exposure to 2-methoxyethanol (2-ME); and to examine the association of 2-methoxyacetic acid (MAA) in urine and plasma collected simultaneously from low 2-ME exposure and high 2-ME exposure workers in a semiconductor copper laminate circuit board manufacturing plant.

METHODS

Eight hour time weighted breathing zone monitoring was performed to verify the 2-ME exposure classification between workers in regular and special operations. Urine and plasma samples were simultaneously collected from 74 exposed and 80 non-exposed workers. MAA concentrations in the urine (UMAA) and plasma (PMAA) were measured using previously published methods. Three types of gloves worn by workers (cotton, rubber, and no gloves) were recorded by direct observations in the workplace and validated by person-to-person interview. Protective effectiveness indices (PEI) were used to evaluate the glove effectiveness.

RESULTS

There was no detectable 2-ME/MAA in the air, or in urine and plasma samples in non-exposed workers. The average UMAA and PMAA in special operations were 72.63 mg/g Cr. and 29.72 mg/l, significantly higher than values in regular operations (5.44 mg/g Cr. and 2.58 mg/l, respectively). PMAA showed satisfactory correlation to UMAA in all participants from both regular and special operations. The rubber gloves provided significant reduction in 2-ME uptake, whereas cotton gloves provided little protection with fluctuating effectiveness, based on PEI estimates.

CONCLUSIONS

PMAA, similar to UMAA, could serve as a specific biomarker for 2-ME exposure. Wearing impermeable rubber gloves during high risk tasks can reduce major 2-ME exposure. Other improvements, including engineering control, should be provided to diminish worker exposure to 2-ME in occupational environments.

Predictors of whole-body vibration levels among urban taxi drivers

To identify a set of important WBV predictors that could be used to develop a statistical instrument for exposure assessment in a large epidemiologic study, a total of 432 WBV measures were taken from a sample of 247 male drivers in Taipei City, Taiwan. In accordance with the ISO 2631-1 (1997) methods, we measured the frequency-weighted vertical acceleration (z-axis) over drivers' seat surface, under conditions representing different types of rides (vacant vs. short vs. long) assigned to random destinations. Mixed effect models were used to analyse the WBV data including repeated measures. For this group of urban taxi drivers regularly exposed to WBV of low intensity (mean = 0.31 ms( - 2), ranging from 0.17 to 0.55 ms( - 2) r.m.s.), our analyses indicated that average driving speed was the primary predictor (p < 0.0001). As average driving speed increased, measured vertical acceleration increased in a quadratic-linear manner (p < 0.0001). Other WBV predictors, after adjusting for the effects of other covariates, included automobile manufacturer (p = 0.02), engine size (p = 0.04), body weight (p = 0.002), age (p = 0.02), use of seat cushion (p = 0.03), and traffic period (p = 0.02). Our study suggests that a similar statistical approach could be employed in future studies to improve the quality and efficiency of WBV exposure assessment in professional drivers.

Haematological effects among silk screening workers exposed to 2-ethoxy ethyl acetate

BACKGROUND

2-Ethoxy ethyl acetate (2-EEA) is a solvent with broad industrial and commercial applications. It has been reported to cause hematological toxicity, infertility, and teratogenesis.

AIMS

To investigate the haematological effects in 2-EEA exposed workers.

METHODS

Workers from one silk screening shop (n = 29), using 2-EEA as the major cleaning and printing solvent, were recruited as a high exposure group. Workers with indirect and non-exposure to 2-EEA (n = 56) were recruited as the comparison group. Venous blood was collected for blood routine examination. Air concentration of 2-EEA in this plant was measured by eight hour personal sampling.

RESULTS

The geometric mean (GM) of air concentration of 2-EEA in the high exposure group was 7.41 ppm (range 1.35-16.5 pppm). The mean exposure of female workers (GM = 9.34 ppm) was significantly higher than that of male workers (GM = 4.87 ppm). The GM of air 2-EEA concentration in the comparison group was 0.07 ppm (range: non-detectable to 3.62 ppm, n = 26). The haemoglobin and haematocrit in the female high 2-EEA exposure workers were significantly lower than those of female workers in the comparison group. No difference was found between male 2-EEA high exposure and comparison group workers. The haemoglobin, haematocrit, and RBC count in the study population had a significant dose-response relation with air 2-EEA levels.

CONCLUSION

Results suggest that 2-EEA is a haematological toxicant, which leads to anaemic status in high exposure female workers.

Follow up study of haematological effects in workers exposed to 2-methoxyethanol

AIMS

To examine the association between 2-methoxyethanol (2-ME) exposure and haematological effects, as well as the recovery from these haematological effects with continuous reduction in exposure to 2-ME.

METHODS

Twenty nine exposed and 90 non-exposed workers were recruited. Haematological parameters, eight hour full shift personal exposure to 2-ME, and urinary 2-methoxyacetic acid (MAA) were repeatedly measured in three consecutive surveys within six months.

RESULTS

Results of haematological examination in the first exposure survey showed that haemoglobin, packed cell volume, and red blood cell count in the male exposed workers were significantly lower than those in the comparison workers. The frequency of anaemia in the exposed group (42%) was significantly higher than that in the comparison group (3%). The haematological effects were significantly associated with the urinary MAA of exposed workers. The haematological effects had returned to normal in the first follow up survey 2.5 months later, when a reduction in 2-ME exposure was noted. Haematological results of the second follow up examination six months later remained normal. The mean airborne exposure of 2-ME in the three surveys dropped from 35.7 to 2.65, then to 0.55 ppm. The mean urinary MAA of exposed workers in the three surveys was reduced from 57.7 to 24.6, then to 13.5 mg/g creatinine (n = 29). The reduction in exposure through both inhalation and potential dermal contact with 2-ME might account for the haematological recovery.

CONCLUSION

2-ME is a haematological toxin which leads to anaemia in exposed workers. However, the toxic haematological effects of 2-ME persist for only a short period of time after cessation or reduction of exposure.

Collection efficiency and capacity of three samplers for acidic and basic gases

This paper compares the collection efficiency and capacity of a coated porous metal disk with those of a silica gel tube and an impinger at the acid or basic aerosol concentration of two times the permissible exposure limitation (Taiwan IOSH, Institute of Occupational Safety and Health), relative humidity of 80 +/- 5%, and temperature of 30 +/- 3 degrees C in the laboratory. Using 5% sodium carbonate/glycerin coating, the collection efficiencies of the porous metal disk for nitric acid, hydrogen chloride, and hydrogen fluoride are found to be higher than those of the silica gel tube and the impinger when the sampling time is less than 3.0 h. The gas collection capacity of the porous metal disk coated with 5% sodium carbonate is calculated to be 3.9, 5.8, and >2.5 mg for nitric acid, hydrogen chloride, and hydrogen fluoride, respectively. For ammonia, the porous metal disk coated using 4% citric acid performs slightly better than the impinger, and the corresponding capacity is slightly greater than 33.6 mg.

Computer simulation of particle overlap in fiber count samples

Fibrous aerosols are of great importance to industrial hygienists because of the severe health risks that may be associated with inhaling such particles. Previous studies on measurement error due to overloading of fibers and nonfibrous particles on the collected sample indicate that a 100-1300 fiber/mm2 filter area is the best filter loading density to reduce bias in fiber counts. The present study investigated the upper fiber and particle concentration limits for reliable counting and identification and the possibility of a procedure for correcting observed fiber counts to account for fiber masking due to overlapping particles or fibers. A computer-generated grid was used to simulate the light microscope graticule field. The resolution of 2000 x 2000 was found to accurately represent the shape of the fibers and nonfibrous particles. Bivariate lognormal distributions were used to describe the length and width distributions of the fibers. The capability of distinguishing particle-overlapped fibers (defined as the resolution index), the coverage of the graticule field, the filter surface loading density, size distributions of fibers and particles, and the fiber-to-particle concentration ratio were the primary parameters in this study. The counting efficiency was found to consistently decrease with increasing filter surface loading density and decreasing resolution index. The recommended upper limit of filter surface fiber density depended not only on the number concentration ratio but also on the filter surface loading densities and size distributions of fibers and particles. The advantage of using a thoracic preseparator on counting efficiency was calculated and found to improve counting efficiency significantly when the count median diameter of nonfibrous particles was close to or larger than the thoracic 50% cutoff point of 10 microm.

Urinary 2-methoxy acetic acid accumulation in response to 2-methoxy ethanol exposure

Urinary 2-methoxy acetic acid reportedly has a long half-life (77.1 hr) in humans. The authors studied urinary 2-methoxy acetic acid in a group of 18 workers exposed to 2-methoxy ethanol from Monday to Saturday following a 7-d cease in production. The weekly time-weighted average exposure concentration of 2-methoxy ethanol was 4.5 ppm. The urinary 2-methoxy acetic acid of exposed workers was increased significantly, from 18.5 microg/ml (10.6 mg/gm creatinine) on Monday (prior to work) to 48.4 microg/ml (46.5 mg/gm creatinine) on Friday (after work), to 51.2 microg/ml (45.6 mg/gm creatinine) on Saturday after work. These levels occurred, despite that fact that the daily mean time-weighted average 2-methoxy ethanol exposures were very consistent and were close to the current Taiwan Permissible Exposure Limit of 5 ppm. These urinary 2-methoxy acetic acid levels were much higher than levels that occur with inhalation only, and they demonstrate that skin absorption is a significant contributor to 2-methoxy ethanol exposure. The high background concentrations of 2-methoxy acetic acid in the preshift urine samples following a 7-d production halt confirm that there is a long half-life of 2-methoxy acetic acid in humans. The determination of urinary 2-methoxy acetic acid is recommended for exposure assessment of 2-methoxy ethanol.

A new technology to measure skin absorption of vapors

Skin vapor absorption is one of the major exposure routes for some widely used chemicals (e.g., 2-methoxy ethanol), but a good apparatus with which exposure can be measured is currently unavailable. In this study, a polished stainless-steel chamber-combined with computer-controlled auto-feedback software and hardware, real-time gas sensors, and an auto-injection microsyringe-was proposed as new technology. In addition, the machines had activated-charcoal tubes and cold traps, both of which simulated the skin uptake and validated the reliability of the proposed system. The exposure concentrations, relative humidity, and temperature were effectively controlled at 25+/-0.5 ppm (or 300+/-10 ppm), 80+/-2%, and 27.5+/-0.5 degrees C, respectively. The relative errors between the quantity of 2-methoxy ethanol collected in either the charcoal tubes or the cold traps and the quantity of ME injected to maintain a constant exposure were less than 5%. The authors also used this new technology to successfully measure skin absorption of ME vapor in 6 volunteers. The authors concluded that this new technology is a direct, continuous, noninvasive, and simple tool with which to measure skin absorption of vapors.

Haematological and spermatotoxic effects of ethylene glycol monomethyl ether in copper clad laminate factories

OBJECTIVES

To investigate the effects of ethylene glycol monomethyl ether (EGME) on haematology and reproduction in exposed workers.

METHODS

53 Impregnation workers from two factories that make copper clad laminate with EGME as a solvent were recruited as the exposed group. Another group of 121 lamination workers with indirect exposure to EGME was recruited as the control group. Environmental monitoring of concentrations of EGME in air and biological monitoring of urinary methoxyacetic acid (MAA) concentrations were performed. Venous blood was collected for routine and biochemical analyses. Semen was collected from 14 workers exposed to EGME for sperm analysis and was compared with 13 control workers.

RESULTS

Results of haematological examination showed that the haemoglobin, packed cell volume, and red blood cell count in the male workers exposed to EGME were significantly lower than in the controls. The frequency of anaemia in the exposed group (26.1%) was significantly higher than in the control group (3.2%). However, no differences were found between the female workers exposed and not exposed to EGME. After adjustment for sex, body mass index, and duration of employment, red blood cell count was significantly negatively associated with air concentrations of EGME, and haemoglobin, packed cell volume, and red blood cell count were significantly negatively associated with urinary concentrations of MAA. The pH of semen in the exposed workers was significantly lower than in the control workers, but there were no significant differences in the sperm count or sperm morphology between the exposed and control groups.

CONCLUSION

It can be concluded that EGME is a haematological toxin, which leads to anaemia in the exposed workers. However, the data from this study did not support the theory of a spermatotoxic effect of EGME.

Measurement of percutaneous uptake of 2-methoxy ethanol vapor in humans

Absorption of vapors through skin has been largely ignored in occupational health, although for ethylene glycol ethers this route of exposure could be more important than inhalation. We used an automated concentration and humidity controlled system to measure real-time percutaneous absorption of 2-methoxy ethanol (ME) vapor in seven volunteers. The exposure concentration (300 +/- 10 ppm or 25 +/- 0.5 ppm), humidity (80 +/- 2%), and temperature (27.5 +/- 0.5 degrees C) were controlled throughout the experiments. Uptakes during 4-hour single-arm exposure at 25 ppm and 300 ppm were 7.0 mg and 65.3 +/- 25.0 mg, respectively, with corresponding uptake rates of 1.36 micrograms/cm2/hr and 13.2 +/- 5.0 micrograms/cm2/hr. Percutaneous absorption was consistent and unsaturated during exposure. Because the permeability constant of ME vapor (14.0 +/- 5.3 cm/hr) was much higher than that of many widely used organic chemicals, we concluded that vapor absorption through skin is a significant contributor to overall ME exposure.

Field evaluation of a passive sampler for the exposure assessment of 2-methoxyethanol

OBJECTIVE

This paper presents a field evaluation of 3 M 3500 passive badges for measuring 2-methoxyethanol (ME) in a humid working environment.

METHODS

A total of 93 pairs of side-by-side active/passive samples, 48 pairs of duplicate active samples, 52 pairs of duplicate passive samples, and three groups of six replicate active/passive samples were compared. Three groups of six replicate active charcoal/active charcoal tube with drying tube samples were also compared to evaluate the humidity effect.

RESULTS

No statistical difference was found between the passive badges and active samplers. Linear regression showed the correlation to be high (r = 0.992, slope = 0.973, n = 93) over the range of 0.17-163 ppm. The mean concentration difference was -0.34 ppm and the mean relative error was 3.50%. The intraclass correlation coefficients of 48 duplicate active samples and 52 duplicate passive samples were 0.994 and 0.989, respectively. The precision of replicate passive, active, and active/drying tube samples (n = 6) were 3.84%, 7.14%, and 5.12%, respectively.

CONCLUSIONS

The humidity effect for active samples was insignificant at the low sampling rate (36.3 ml/min). It is therefore concluded that the use of the passive samplers to assess ME exposure produces comparable findings to that of active sampling.

Mouse models of tumor development in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a prevalent familial cancer syndrome resulting from germ line mutations in the NF1 tumor suppressor gene. Hallmark features of the disease are the development of benign peripheral nerve sheath tumors (neurofibromas), which can progress to malignancy. Unlike humans, mice that are heterozygous for a mutation in Nf1 do not develop neurofibromas. However, as described here, chimeric mice composed in part of Nf1-/- cells do, which demonstrates that loss of the wild-type Nf1 allele is rate-limiting in tumor formation. In addition, mice that carry linked germ line mutations in Nf1 and p53 develop malignant peripheral nerve sheath tumors (MPNSTs), which supports a cooperative and causal role for p53 mutations in MPNST development. These two mouse models provide the means to address fundamental aspects of disease development and to test therapeutic strategies.

Detection of methyl ethyl ketone in urine using headspace solid phase microextraction and gas chromatography

Headspace solid-phase microextraction coupled with gas chromatography/flame ionization detection was developed to measure urinary methyl ethyl ketone (MEK). A fused silica fiber coated with 75 microns carboxen/polydimethylsiloxane was used to extract urinary MEK. The optimal extraction conditions were obtained when temperature was 50 degrees C, extraction time was 15 minutes, and ammonium sulfate concentration was 0.5 g/mL. The optimal desorption temperature and time were 200 degrees C and 5 minutes, respectively. The concentration range of calibration curves was 27 to 8000 ng/mL of MEK. The within-day and between-day pooled coefficients of variation (9 concentrations, triplicate samples) were 5.4% and 8.8%, respectively. The limit of detection and limit of quantitation were 4.2 ng/mL and 21.6 ng/mL, respectively. The recovery (+/- standard deviation) of MEK was 100.2% +/- 8.6% (n = 3). MEK in urine was stable for at least 1 month when stored at -20 degrees C. This method proved to be applicable for the analysis of urinary MEK of exposed workers in a plastic material printing plant. We concluded that this new method is sensitive, inexpensive, simple, and reliable for measuring the occupational exposure of MEK.

Correlation between urinary 2-methoxy acetic acid and exposure of 2-methoxy ethanol

OBJECTIVES

To examine the correlation between airborne 2-methoxy ethanol (ME) exposures and the urinary 2-methoxy acetic acid (MAA) and to recommend a biological exposure index (BEI) for ME.

METHODS

8 Hour time weighted average (TWA) personal breathing zone samples and urine samples before and after the shift were collected from Monday to Saturday for 27 workers exposed to ME and on Friday for 30 control workers.

RESULTS

No correlation was found between airborne exposure to ME and urinary MAA for nine special operation workers due to the use of personal protective equipment. For 18 regular operation workers, a significant correlation (r = 0.702, p = 0.001) was found between urinary MAA (mg/g creatinine) on Friday at the end of the shift and the weekly mean exposures of ME in a 5 day working week. The proposed BEI, which corresponds to exposure for 5 days and 8 hours a day to 5 ppm, extrapolated from the regression equation is 40 mg MAA/g creatinine. A significant correlation was also found between the weekly increase of urinary MAA (Friday after the shift minus Monday before the shift) and the weekly mean exposures of ME (r = 0.741). The recommended value of the weekly increase of urinary MAA for 5 days repeated exposures of 5 ppm ME is 20 mg/g creatinine. No urinary MAA was detected in workers in the non-exposed control group.

CONCLUSIONS

The Friday urinary MAA after the shift or the weekly increase of urinary MAA is a specific and a good biomarker of weekly exposure to ME.

Improved method to measure urinary alkoxyacetic acids

OBJECTIVES

To simplify the current preparation of samples, and to improve the specificity and reliability of the conventional analytical methods to measure urinary alkoxyacetic acids.

METHODS

Samples containing alkoxyacetic acids including methoxy, ethoxy, and butoxyacetic acids (MAA, EAA, and BAA) were acidified with HCl and extracted with a mixed solvent of methylene chloride and isopropyl alcohol, then analysed by gas chromatography/mass spectrometry (GC/MS).

RESULTS

Optimal results were obtained when pH was 1.05-1.45, the ratio of methylene chloride and isopropyl alcohol was 2:1, and when extraction time was 10 minutes. Over the concentration range 0.3-200 micrograms/ml, MAA, EAA, and BAA could be determined with a pooled coefficient of variation (nine concentrations, six replicate samples) of 5.55%, 6.37%, and 6.41%, respectively. Urine samples were stable for at least 5 months and 3 freeze-thaw cycles at -20 degrees C. The limits of detection of MAA, EAA, and BAA were 0.055, 0.183, and 0.009 microgram/ml, respectively. The matrix effect of urine samples was negligible for MAA and EAA, but were marginally significant for BAA. The average recoveries of alkoxyacetic acids were 99%-101%. In urine samples MAA from 15 exposed workers showed a strong linear correlation (r = 0.999, slope = 1.01) between the new GC/MS method and Sakai's GC method.

CONCLUSIONS

The simplified non-derivatisation pretreatment of samples coupled with GC/MS can provide a specific, sensitive, simple, safe, and reliable method for the biological monitoring of occupational exposure of ethylene glycol ethers.

Development of respirable aerosol samplers using porous foams

Workplace aerosols must be sampled to assess the degree of health hazard caused by the particulate matter. By adjusting the sampling flow rate, most of the samplers can match the 50% cutoff size, but not the slope of the respirable convention defined by the American Conference of Governmental Industrial Hygienists, the International Organization for Standardization, and the European Committee for Standardization (CEN). Combinations of foams (or other porous material) of different nominal sizes (10-100 ppi) and thicknesses (5-35 mm) were employed to overcome this bias. A foam disk 25 mm in diameter was placed in an asbestos sampling cowl. Dioctylphthalate was the liquid test agent. An aerodynamic particle sizer and an Aerosizer were calibrated against a settling chamber and were employed to measure the aerosol number concentrations and size distributions upstream and downstream of the foams. The sampling efficiency data showed that the 50% cutoff size could be met for foams in series, but that the slope remained sharper than the new definition. Foams in parallel showed great flexibility and many of the parallel combinations flattened the slope, closer to that of the new international respirable convention. For instance, when the total flow rate is set at 10.1 L/min the aerosol penetration through foams in parallel (100 ppi, 20 mm thick, diameter 25 mm + 10 ppi, 20 mm thick, diameter 13 mm) nearly matched the new international standard for respirable fraction. This sampler can be further miniaturized for smaller sampling flow rates to fit the capacity of personal sampling pumps.

Pre-analytical for biological monitoring of manganese

Manganese is an essential element but it may result in a toxic event if the workers are excessively exposed to this element. Monitoring of biological Mn exposure is therefore important. The careful preparation for Mn analysis is necessary. In order to get a correct protocol for sampling and storage of the biological samples, identification of the possible contamination source is necessary. This study is concerned with the monitoring procedure of manganese especially the sources of contamination sampling, sample transportation and storage. The results of the study shows that some kinds of needles and anticoagulants might be the main sources of contamination of specimen. It is important to avoid these contamination in performing biological monitoring on workers exposed to manganese.

Automated on-line sample pretreatment system for the determination of trace metals in biological samples by inductively coupled plasma mass spectrometry

A fully automated on-line sample pretreatment system combining microwave digestion with sample preconcentration/matrix separation for the determination of trace metals (Fe, Ni, Cu, Zn, and Pb) in blood and serum samples by inductively coupled plasma mass spectrometry (ICPMS) was designed and evaluated. The samples were mixed with an appropriate reagent and digested in a flow-through, focused microwave-heated oven. After digestion, the sample solution was transferred on-line to a column packed with iminodiacetate-based resin for separation of matrix elements like Na, K, Ca, Mg, Cl, P, and S that might interfere with the measurement by ICPMS. The analytes chelated on the resin were subsequently eluted and led to ICPMS for multielement determination. The whole sample pretreatment process was automatically controlled by a self-designed expert system. The analytical reliability of data from this on-line system was confirmed to be good with the analysis of SRM samples (Seronorm Whole Blood and NIST SRM 1598 Bovine Serum), and the limits of detection (3 sigma) for Fe, Ni, Cu, Zn, and Pb were 68, 0.34, 3.5, 13.4, and 0.22 microgram/L, respectively. With this fully automated on-line system, the determination of analytes in biological fluid samples down to micrograms-per-liter levels has been proven to be feasible, and the sample throughput can achieve up to 6 samples/h.

Characteristics of lead aerosols in different work environments

Air samples were collected to examine physical and chemical characteristics of lead aerosols in different work environments in the airborne lead concentration range from 28-783 micrograms/m3. Size distribution of aerosols was measured using a Marple personal cascade impactor, and lead analysis was conducted using graphite atomic absorption spectrometry. Lead aerosol size distribution was found to be different from that of total particles. Such differences are not negligible and must be taken into account when estimating aerosol deposition within the human respiratory tract. Variation of MMAD (mass median aerodynamic diameter) and GSD (geometric standard deviation) of lead aerosols in the coarse mode wit total airborne concentration was found to be small, and the assumption that lead aerosol distribution is constant is reasonable for establishing the relationship between airborne lead concentration in all work areas of the three plants except the charging area of the capacitor plant. Therefore, it is expected that either total airborne lead or respirable airborne lead concentration can be used to correlate blood lead concentration.

Occupational neurotoxic diseases in Taiwan: a review of the outbreaks and clinical features

In the past 20 years, several outbreaks of neurotoxic disease due to occupational exposure have occurred in Taiwan. The most notorious outbreaks were 'Yu-cheng' due to contamination of polychlorinated biphenyls in cooking oil, lead poisoning in battery manufacturers and workers in a ship-scrapping yard, tile factory and battery recycling plants, and n-Hexane intoxication in press-proffers and ball-manufacturers. In addition, there were manganese intoxication in ferromanganese smelters, mercury intoxication in lamp-socket workers, carbon disulfide intoxication in viscose rayon workers and hydrogen sulfide intoxication in chemical synthetic plants. Although the incidence of occupational neurotoxic diseases has increased, the real incidence is probably still underestimated. The reasons for the underestimation include: 1) the education for workers in industrial hygiene is inadequate; 2) high risk workers are not screened well; 3) physicians are not well trained in early diagnosis of occupational diseases; 4) material safety data information is not readily available in the factories; and 5) the threshold limit values for toxic substances are relatively high in Taiwan, compared with other developed countries.

Lipid peroxidation in workers exposed to manganese

OBJECTIVES

The following hypothesis was tested: plasma manganese concentration is associated positively with the product of lipid peroxidation, and lipid peroxidation is associated negatively with the activities of antioxidants in workers exposed to manganese.

METHODS

The plasma manganese concentration of 22 manganese-exposed workers and 45 referents was determined by graphite furnace atomic absorption spectrophotometry. Malondialdehyde, the product of lipid peroxidation, was determined by high-performance liquid chromatography, and the activities of protective enzymes were measured by ultraviolet-visible spectrophotometry.

RESULTS

The activities of superoxide dismutase, glutathione peroxidase, and catalase spread widely among the referents. The activity of superoxide dismutase and the concentrations of malondialdehyde and manganese were significantly higher in the manganese workers than in the referents. The concentration of malondialdehyde in the exposed workers was correlated strongly with the manganese level of plasma.

CONCLUSIONS

Malondialdehyde can be used as an index of lipid peroxidation induced by manganese exposure.

Nf1 gene targeting: toward models and mechanisms

Patients with neurofibromatosis type I develop multiple benign nerve sheath tumors and are predisposed to a number of malignancies. Since loss-of-function mutations in the NF1 gene appear to be responsible for the disease, NF1 has been classified as a tumor suppressor. Several strategies involving the targeted disruption of the murine homologue have been used in an attempt to establish an animal model for the disease and four types of animals have been generated: (1) Nf1 +/- animals, (2) NF1 -/- embryos, (3) Nf1 -/- chimeras, and (4) mice transplanted with Nf1 -/- hematopoietic stem cells. In addition to yielding mice which mimic various aspects of the human disease, each of these approaches has contributed to a better understanding of the normal function of Nf1.

Chronic carbon disulfide encephalopathy

To understand central nervous damage after long-term exposure to carbon disulfide (CS2), 10 patients who had polyneuropathy with various neuropsychiatric symptoms in a viscose rayon plant were studied. Clinical and laboratory examinations including electroencephalography (EEG), brain computed tomography (CT), brain magnetic resonance images (MRI), and carotid duplex sonography were carried out. Clinically, headache, unpleasant dreams, memory impairment, fatigue, anorexia and emotional lability were common in these patients while 2 patients had stroke episodes. EEGs were all normal. Brain CT scan showed mild cortical atrophy in 3 and low density lesions in the basal ganglia in 3. Brain MRI studies also disclosed mild cortical atrophy in 4 and multiple lesions involving the basal ganglia and corona radiata in 4. Carotid duplex sonography revealed mild atherosclerosis with plaques (< 20% stenosis) of extracranial vessels in 6. However there was no significant difference in flow velocities and flow volumes in the extracranial carotid arteries between patients and the normal controls. Interestingly, 2 patients had multiple brain lesions in the subcortical white matter but without strokes. In conclusion, encephalopathy with possible strokes may occur after chronic exposure to CS2, as well as polyneuropathy. The lesions usually involve the basal ganglia and subcortical white matter. Furthermore, MRI study may detect brain lesions particularly in the subcortical white matter areas before the occurrence of stroke.

Vascular system defects and neuronal apoptosis in mice lacking ras GTPase-activating protein

The gene encoding p120-rasGAP, a negative regulator of Ras, has been disrupted in mice. This Gap mutation affects the ability of endothelial cells to organize into a highly vascularized network and results in extensive neuronal cell death. Mutati ons in the Gap and Nf1 genes have a synergistic effect, such that embryos homozygous for mutations in both genes show an exacerbated Gap phenotype. Thus rasGAP and neurofibromin act together to regulate Ras activity during embryonic development.

Polyneuropathy induced by carbon disulphide in viscose rayon workers

OBJECTIVES

To understand the prevalence of polyneuropathy and correlations among the clinical manifestations, electrophysiological findings, and degree of exposure to carbon disulphide (CS2) in workers who were exposed to variable concentrations of CS2 in a viscose rayon factory.

METHODS

All the 163 workers received a detailed physical and neurological evaluation. Fixed point air samples were analysed for CS2. Nerve conduction velocity was studied in 26 workers with symptoms similar to neuropathy.

RESULTS

Nine workers (53%) with overt polyneuropathy from the fibre cutting department and 19 workers (13%) with oligosymptoms similar to polyneuropathy from various jobs were noted. The fixed point air concentrations of CS2 were 150-300 ppm in the cutting areas and 15 to 100 ppm in the spinning areas. The estimated eight hour time weighted averages in the fibre cutting areas were 40-67 ppm. The occurrence of polyneuropathy was generally correlated with the degree of exposure to CS2. Nerve conduction velocities (NCVs) were significantly different in the overt polyneuropathy and subclinical polyneuropathy groups from the normal controls. The sensitive indicators for CS2 polyneuropathy were distal latency, motor NCV, and amplitude of sensory nerve action potentials in sensory NCVs.

CONCLUSION

The outbreak of polyneuropathy was attributed to higher concentrations of CS2 in fibre cutting areas. Even in other jobs with relatively lower concentrations of CS2, the hazard of subclinical polyneuropathy cannot be overlooked.

Asanguineous whole body perfusion with a new intracellular acellular solution and ultraprofound hypothermia provides cellular protection during 3.5 hours of cardiac arrest in a canine model

Temporary cessation of blood flow is a necessary aid for certain complex neurosurgical and cardiovascular procedures, and hypothermia is often used to help protect against the deleterious effects of ischemia and anoxia. In an attempt to protect cellular integrity during ultraprofound hypothermia (< 10 degrees C) and complete blood substitution, two new crystalloid-colloid blood substitutes (Hypothermosol-maintenance [HTS-M] and Hypothermosol-purge [HTS-P]) have been evaluated. Using extracorporeal bypass, 14 dogs were totally exsanguinated during cooling using the HTS-P solution, then perfused (40-85 ml/kg/min; mean arterial blood pressure = 25-40 mmHg) with either TS-M (Group I, n = 11), or with HTS-P as controls (Group II, n = 3) for 3 hr at 7 degrees C. During warming, the dogs were autotransfused and observed neurologically and biochemically during recovery. All dogs in Group I recovered and eight have survived long term (12-80 weeks) without apparent neurologic deficits. In contrast, dogs in Group II were more difficult to revive (cardiac resuscitation); two survived long term with delayed neurologic recovery. Evaluation of biochemical parameters showed only a transient and inconsequential elevation in enzymes (e.g., brain, liver, and heart) in Group I compared with the markedly greater elevations in Group II. The faster neurologic recovery of dogs treated with the "intracellular" maintenance solution supports the biochemical data showing the benefits of this type of blood substitute for extending the safe limits of hypothermic cardiac arrest to beyond 3 hr.

Tumour predisposition in mice heterozygous for a targeted mutation in Nf1

Human neurofibromatosis type 1 is a dominant disease caused by the inheritance of a mutant allele of the NF1 gene. In order to study NF1 function, we have constructed a mouse strain carrying a germline mutation in the murine homologue. Heterozygous animals do not exhibit the classical symptoms of the human disease, but are highly predisposed to the formation of various tumour types, notably phaeochomocytoma, a tumour of the neural crest-derived adrenal medulla, and myeloid leukaemia, both of which occur with increased frequency in human NF1 patients. The wild-type Nf1 allele is lost in approximately half of the tumours from heterozygous animals. In addition, homozygosity for the Nf1 mutation leads to abnormal cardiac development and mid-gestational embryonic lethality.

Chronic elemental mercury intoxication: clinical and field studies in lampsocket manufacturers

Four workers chronically exposed to elemental mental mercury in a lampsocket manufacturing factory were studied. The clinical manifestations were severe in one, mild in another, and suspicious in the remaining two. Correlation between severity of clinical features and increased urinary mercury concentrations was found. The time weighted average mercury concentrations were 0.945 mg/m3 and 0.709 mg/m3 for two workers in one room and 0.225 mg/m3 in the other. After stopping exposure, the workers recovered spontaneously or with D-penicillamine treatment within six months. It is concluded that recovery from chronic elemental mercury intoxication may be complete when patients are removed early from the exposure environment. The hazard of mercury intoxication in recycling of waste substances is emphasised.

Comparison of the effects of total blood substitution during two different levels of hypothermic cardiac arrest

The effect of total blood replacement with a solution containing neither hemoglobin nor fluorocarbon was studied under two different levels of hypothermia. Ten dogs were anesthetized and esophageal temperature lowered to about 24 degrees at which time exsanguination began. Upon cardiac arrest and the completion of exsanguination, continuous whole body closed chest extracorporeal circulation of an oxygenated blood substitute was begun. Hematocrit was 1% while core temperature remained less than 10 degrees C for 3 hours of perfusion during which nadirs of 1.3 degrees C (Group I, N = 5) and 7.3 degrees (Group II, N = 5) were achieved. Replacement of the perfusate with whole blood began once the dog was rewarmed to approximately 10 degrees C. All dogs survived the procedure. Two dogs from each group died by the fourth post-operative day but the others survived long term. Group II showed a faster return to normal based on motor behavioral, biochemical and hematological changes. Thus the combination of profound hypothermia and complete blood substitution with a solution lacking any special oxygen carrying molecule, can be tolerated for 3 hours using both levels of hypothermia, however, the warmer one appears to be associated with faster recovery.

Complete blood substitution during profound hypothermic cardiac arrest in dogs

This study compared the effects of 3 hours of cardiac arrest performed at 2 different levels of profound hypothermia in totally exsanguinated, blood substituted dogs. Dogs (N = 10) were anesthetized and esophageal temperature was lowered to 24 degrees at which time exsanguination began. Once exsanguination was complete and the heart had arrested, continuous whole body perfusion of an oxygenated blood substitute solution was performed for 3 hours. Core temperature during this period remained below 10 degrees C and reached nadirs of 1.3 degrees C in Group 1 (N = 5) versus 7.3 degrees C in Group II (N = 5). Once the dog was allowed to rewarm to 10 degrees C replacement of the perfusate with blood was begun. All dogs survived the procedure but 2 dogs from each group died by 4 days following the experiment. The remaining 6 dogs were observed for between 10 and 85 days. The group perfused with blood substitute at the warmer nadir had a faster recovery of motor behavior and showed smaller changes from normal in several biochemical and hematological parameters. These findings indicate that profound hypothermia and total blood substitution can be successfully achieved at either temperature nadir, but the warmer level appears to be associated with a faster recovery.

n-Hexane polyneuropathy in a ball-manufacturing factory

Five overt and two occult cases of n-hexane polyneuropathy occurred in a ball-manufacturing factory in Taiwan. The severity of polyneuropathy was directly related to the index of n-hexane exposure that occurred during the processes of cement coating and nylon fiber winding in a poorly ventilated room. The n-hexane concentrations over eight hours of personal sampling of the air of the cement coating and nylon fiber winding areas were 109 ppm and 86 ppm, respectively. After installation of a new factory ventilation system, these seven patients recovered completely, and there were no new cases in the two-year follow-up.

Causes of death in aged burn patients: analysis of 36 cases

Over a 10-year period 110 patients over the age of 65 years were admitted to the Burn Center, Rui Jin Hospital and 36 (32.7 per cent) died. Significant differences between the survivors and non-survivors were related to the total burn surface area and full skin thickness burn size. Among the causes of death, pre-existing cardiopulmonary diseases and associated inhalation injury were particularly important since pneumonia was considered as a primary cause of death in 13 patients, myocardial disease in two, cor-pulmonale and heart failure in two. Care of the early fluid resuscitation, early excision of deep burn wounds and grafting, prevention or treatment of a variety of life-threatening complications, and nutritional supplementation appeared to decrease the mortality of aged burn patients.

Outbreak of carbon tetrachloride poisoning in a color printing factory related to the use of isopropyl alcohol and an air conditioning system in Taiwan

Three workers from a color printing factory were admitted to community hospitals in 1985 with manifestations of acute hepatitis. One of the three had superimposed acute renal failure and pulmonary edema. An investigation was subsequently conducted at the plant to determine the etiology of the outbreak and the prevalence of liver disease among the remaining workers. Comprehensive medical evaluations were conducted, which included physical examinations, liver function tests, and serological screening for hepatitis. Seventeen of 25 workers from the plant had abnormal liver function tests 10 days after the outbreak, and a significant association was found between the presence of abnormal liver function tests and a history of recently having worked inside any of three rooms in which an interconnecting air conditioning system had been installed to cool the printing machines. After further investigation, it was determined that the incident occurred following inadvertent use of carbon tetrachloride to clean a pump in the printing machine. A simulation of the pump cleaning operation revealed ambient air levels of carbon tetrachloride of 300-500 ppm. Ultimately, it was concluded that the outbreak was in all likelihood due to the combined use of carbon tetrachloride and isopropyl alcohol in the cleaning operation. This outbreak underscores the importance of adopting appropriate industrial hygiene measures in a rapidly industrializing nation such as Taiwan.

Free transplantation of sub-axillary lateral thoraco-dorsal flap in burn surgery

Free transplantation of subaxillary lateral thoracodorsal flap is recommended. The thoraco-dorsal artery and its accompanying veins may nourish and drain a large musculo-cutaneous flap. The calibres of both the artery and the veins are big enough to be anastomosed to the recipient vessels using the naked eye. The donor area can be closed by first intention suture without interfering with the functional recovery of the donor area. Both the functional and cosmetic results after free transplantations of this flap are good. In acute electrical or other deep burns, this flap can be used to prevent infection, to protect the deep vital structures, and to lessen the amputation rate. A better condition is created for functional recovery and facilitating reconstructive surgery. The muscular branch of the thoraco-dorsal artery was always present in our 50 patients whereas only 20 cases (40 per cent) had an independent cutaneous branch which nourishes the flap. We stress the point of preserving and using the muscular branch as the main blood vessel to be anastomosed for this free flap.

Changes in lymphocyte response to phytohaemagglutinin and serum immunosuppressive activity after thermal injury

The present study consisted of two parts. In part one, 14 cases were divided into an invasive infection group (4 cases) and a non-invasive infection group (10 cases). A total of 68 assays for lymphocyte responses to PHA stimulation were carried out. The invasive infection group showed a significantly suppressed lymphocyte response, which occurred during invasive infection but neither before nor after the infection. The extent of third-degree burns was statistically significant between these two groups (P less than 0.05), but no significance was found between the total body surface area burned. In part two, 18 burn patients were studied for serum immunosuppressive activity. Both invasive infection cases and non-invasive infection cases showed serum immunosuppression during the course of the study and no significant difference was found between these two groups (P greater than 0.05). It is concluded that the extent of third-degree burn and the complicated systemic infection contribute to the impairment of lymphocyte responses to PHA stimulation, while the post-burn serum immunosuppression is unrelated to the occurrence of systemic infection.

Changes of serum amino acids in severely burned patients

The serum amino acids profile in ten severe burn patients was basically similar with the findings in major burns reported in our proceeding article, supporting the conclusion that burn patients might have a particular amino acid pattern. The larger was the burn size, the more severe was the nitrogen loss. Following a severe burn, the patient was faced with the challenge of acute protein malnutrition. After severe burns, the ratio of serum Phe/Tyr rose to a higher level than in the major burns. Moreover, the elevation of serum Met/Cys ratio indicated a more serious metabolic disturbance. During the first two weeks postburn, acute decrease of serum BCAA by 20-30 per cent of the normal value was associated with a striking increase of mortality. This fact indicated the level of BCAA might be of prognostic value. In severe burns, other than huge amount of calories and protein supplied, enriched BCAA, and perhaps, carnitine might be beneficial.

Serum and erythrocyte amino acid pattern: studies on major burn cases

Venous serum amino acids were measured in 13 patients with major burns. Erythrocyte amino acids and plasma cortisol, blood sugar and urine catecholamine were measured in two representative subgroups respectively. After burn injury, serum proline, glycine, valine, isoleucine and arginine were significantly decreased; phenylalanine, cysteine, methionine, leucine, glutamate, alanine, aspartic acid and tyrosine were significantly increased. Histidine and lysine fluctuated. This serum amino acid profile is considered as a specific pattern for major burns. Serum phenylalanine was markedly elevated in the hypermetabolic burn patients, its fluctuation coincided with the burn course and was negatively correlated with serum albumin level (P less than 0.001). These findings suggest that the ratio of phenylalanine tyrosine is a useful clinical parameter for assessing the patient's nutritional condition. Twenty-three simultaneous determinations of both serum and erythrocyte amino acid concentrations show similar changes, suggesting that the serum amino acid profile might reflect the change of total free amino acid pool. After burn injury, plasma cortisol, blood sugar and urine catecholamine were elevated as well as urine urea nitrogen. However, although the first three returned to normal by the end of the second week post burn, urine urea nitrogen remained high. This indicates that there are other factors controlling nitrogen loss in patients with major burns, it is also postulated that, due to the abnormal amino acid pattern revealed after major burns, the constituents of commercially available amino acid solutions should be modified.