Short-term exposure to noise, fine particulate matter and nitrogen oxides on ambulatory blood pressure: A repeated-measure study.

Exposure to road traffic noise, fine particulate matter (aerodynamic diameter ≤2.5 µm; PM2.5) and nitrogen oxides (NOx) has been associated with transient changes in blood pressure, but whether an interaction exists remains unclear. This panel study investigated whether noise, PM2.5 and NOx exposure were independently associated with changes in 24-h ambulatory blood pressure. We recruited 33 males and 33 females aged 18-32 years as study subjects. Personal noise exposure and ambulatory blood pressure were monitored simultaneously in 2007. During the data collection periods, 24-h data on PM2.5 and NOx from five air-quality monitors within 6 km of participants' home addresses were used to estimate their individual exposures. Linear mixed-effects regression models were used to estimate single and combined effects on ambulatory blood pressure. Exposure to both noise and PM2.5 was significantly associated with increased systolic blood pressure (SBP) and diastolic blood pressure (DBP) over 24h; NOx exposure was only significantly related to elevated DBP. Twenty-four-hour ambulatory blood pressure increased with the current noise exposure of 5 A-weighted decibels (dBA) (SBP 1.44 [95% confidence interval: 1.16, 1.71] mmHg and DBP 1.40 [1.18, 1.61] mmHg) and PM2.5 exposure of 10-µg/m(3) (SBP 0.81 [0.19, 1.43] mmHg and DBP 0.63 [0.17, 1.10] mmHg), as well as the current NOx exposure of 10-ppb (DBP 0.54 [0.12, 0.97] mmHg) after simultaneous adjustment. These findings suggest that exposure to noise and air pollutants may independently increase ambulatory blood pressure and the risk of cardiovascular diseases.

Personal Exposure to Sulfuric Acid in the Electroplating Industry: Development and Validation of a Predictive Model.

This study aimed to measure personal exposure to sulfuric acid in the electroplating industry to establish a predictive model and test its validation. We collected indoor air parameters and related information from four electroplating plants. Silica gel sorbents were used to collect air samples using high-performance ion chromatography. We collected air samples from three plants (i.e., Plant B, Plant C, and Plant D) and applied multiple linear regressions to build a predictive model. Eight samples collected from the fourth plant (i.e., Plant A) were used to validate the model. A total of 41 samples were collected with a mean of 25.0 ± 9.8 µg/m3 (range 12.1-51.7 µg/m3) in this study, including Plant A (8 samples, 17.5 ± 2.8 µg/m3, 13.0-22.0 µg/m3), Plant B (11 samples, 36.5 ± 9.7 µg/m3, 23.1-51.7 µg/m3), Plant C (11 samples, 16.4 ± 1.7 µg/m3, 12.1-17.8 µg/m3), and Plant D (11 samples, 27.4 ± 1.7 µg/m3, 24.1-29.9 µg/m3). Plant B was significantly higher in sulfuric acid than the other plants. Workers from the electroplating process plants were exposed to sulfuric acid at 29.0 ± 11.5 µg/m3. The predictive model for personal exposure to sulfuric acid fit the data well (r2 = 0.853; adjusted r2 = 0.837) and had an accuracy of 5.52 µg/m3 (bias ± precision; 4.98 ± 2.38 µg/m3), validated by the personal sampling of the fourth plant. This study observed that sulfuric acid exposure was lower than the permissible exposure level of 1000 µg/m3 in Taiwan and the United States, and only two samples were lower than the European Union standard of 50 µg/m3. The developed model can be applied in epidemiological studies to predict personal exposure to sulfuric acid in plants using electroplating.

Occupational noise exposure and incident hypertension in men: a prospective cohort study.

The associations between occupational noise exposure and hypertension remain controversial because of the differences in study designs, exposure assessments, and confounding controls. This prospective study investigated the relationship between noise exposure and the 10-year risk of hypertension. A cohort of 578 male workers in Taiwan was followed from 1998 to 2008. All subjects were divided into high-, intermediate-, and low-exposure groups on the basis of noise exposure assessment. Cox regression models were used to estimate the relative risks of hypertension after adjustment for potential confounders. During the 7,805 person-years of follow-up, 141 hypertension cases were identified. Significant increases of 3.2 (95% confidence interval (CI): 0.2, 6.2) mm Hg in systolic blood pressure and 2.5 (95% CI: 0.1, 4.8) mm Hg in diastolic blood pressure between the baseline and follow-up measurements were observed in the high-exposure group. Participants exposed to ≥85 A-weighted decibels (dBA) had a 1.93-fold (95% CI: 1.15, 3.22) risk of hypertension compared with those exposed to <80 dBA. There was a significant exposure-response pattern (P = 0.016) between the risk of hypertension and the stratum of noise exposure. Prolonged exposure to noise levels ≥85 dBA may increase males' systolic and diastolic blood pressure levels. This association may translate into a higher incidence of hypertension.

Simultaneous determination of components released from dental composite resins in human saliva by liquid chromatography/multiple-stage ion trap mass spectrometry.

Dental composite resins are widely used for fixing teeth; however, the monomers used in dental composite resins have been found to be cytotoxic and genotoxic, namely triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A glycol dimethacrylate (Bis-GMA). In this study, we incubated dental composite resins with human saliva for demonstrating the released monomers and biodegradation products. A simple saliva sample dilution method without purification or derivatization was used for quantification. We found that liquid chromatography coupled with multiple-stage ion trap mass spectrometry (LC-MS(n) ) operated in selected reaction monitoring (SRM) mode was able to separate the three monomers within 10 min. The calibration curves were linear (R² >0.996) over a wide range for each monomer in saliva: TEGDMA, 5-500 ppb; UDMA, 5-100 ppb, and Bis-GMA, 5-700 ppb. Furthermore, several biodegradation products were discovered with data-dependent MS/MS scan techniques. Although TEGMA degradation products have previously been reported, we identified two previously unknown UDMA degradation products. The LC-MS/MS method developed in this study was able to successfully quantify monomers and their principal biodegradation products from dental composite resins in human saliva.

Co-exposure to noise, N,N-dimethylformamide, and toluene on 24-hour ambulatory blood pressure in synthetic leather workers.

Independent exposure to noise, N,N-dimethylformamide (DMF), or toluene has been associated with cardiovascular effects, but the combined effects are not clear. This study investigated ambulatory systolic blood pressure (SBP) and diastolic blood pressure (DBP) in workers co-exposed to noise, DMF, and toluene. Twenty workers in a synthetic leather manufacturing company were recruited as study subjects. Personal noise exposure and ambulatory blood pressure were measured concomitantly for 24 hr; airborne co-exposure to DMF and toluene during the working period was also analyzed to identify solvents exposure. Linear mixed-effects regressions were used to estimate effects on ambulatory blood pressure by controlling potential confounders. Four high-combined-exposure workers (83 +/- 8 dBA; DMF: 3.23 +/- 2.15 ppm, toluene: 1.09 +/- 1.13 ppm) had the higher means of 16 +/- 7 mmHg in 24-hr DBP (p = 0.027) and 21 +/- 8 mmHg in working-time DBP (p = 0.048) than seven low-combined-exposure workers (73 +/- 12 dBA; DMF: 0.41 +/- 0.02 ppm, toluene: 0.12 +/- 0.01 ppm). Three high-noise-exposure workers (84 +/- 7 dBA) also had a marginal increase of 13 +/- 6 mmHg in DBP at work (p = 0.076) compared with the control group. No significant differences in SBP and DBP were found between six high-solvent-exposure workers (DMF: 1.24 +/- 1.25 ppm, toluene: 2.63 +/- 1.29 ppm) and office workers during any periods. After the Bonferroni correction, there were no significant differences in ambulatory blood pressure between three high-exposure groups and the low-exposure groups. Our findings suggest no interactive effects of co-exposure to noise, DMF, and toluene on workers' ambulatory blood pressure.

Short-term exposure to noise on stroke volume and left ventricular contractility: A repeated-measure study.

Prolonged exposure to noise has been associated with cardiovascular disease, but the possible mechanism for its influence on cardiac activity is unknown. This study investigated the acute effects of noise exposure on 24-h ambulatory cardiac parameters among male workers. We recruited 75 volunteers in an aviation-industry cohort in 2009. Personal noise-exposure levels and individual cardiac parameters, including stroke volume (SV) and left ventricular contractility (LVC), were measured simultaneously over 24 h on working and nonworking days. Linear mixed-effects regression models were used to estimate transient and sustained effects on ambulatory SV and LVC among high-noise-exposure (≥80 A-weighted decibels [dBA]), low-noise-exposure (<80 dBA) and office workers. Every 1-dBA increase in noise exposure was significantly associated with transient changes of -1.50 (95% confidence interval [CI]: -2.18, -1.03) ml/beat in SV and -1.76 (-2.99, -1.03) L/sec in LVC at work on working days only among high-exposure workers. The 1-dBA increase in nocturnal noise exposure was also significantly associated with transiently decreased SV among high-exposure (-1.62 [-2.15, -1.22] ml/beat), low-exposure (-1.27 [-1.57, -1.03] ml/beat) and office workers (-1.09 [-1.18, -1.00] ml/beat), but only the high-exposure group had the transiently reduced LVC (-1.70, [-2.37, -1.22] L/sec) after the current noise exposure on nonworking days. Such decreasing effects persisted to become sustained decreases in 24-h ambulatory SV in high-exposure (-1.10 [-1.20, -1.01] ml/beat) and office workers (-1.13 [-1.22, -1.05] ml/beat) on working days and in all three groups (-1.19 [-1.36, -1.04]; -1.15 [-1.31, -1.02]; -1.08 [-1.13, -1.02] ml/beat, respectively) on nonworking days. No significant effect on 24-h ambulatory LVC was found in any group on working or nonworking days. Occupational and nocturnal noise exposure may have acute effects on 24-h ambulatory SV among male workers, directly influencing the cardiac function related to cardiovascular disease.

Application of solid-phase microextraction and gas chromatography-mass spectrometry for measuring chemicals in saliva of synthetic leather workers.

Saliva is of interest as a diagnostic aid for oral and systemic diseases, to monitor therapeutic drugs, and detect illicit drug abuse. It is also attractive for biological monitoring of exposure to hazardous solvents. The major advantage of this indicator over other biological monitoring targets is that the saliva is noninvasive and less confidential in comparison with blood and urine. Salivary analysis is generally acceptable by study subjects and can be applied to investigation of a wide variety of compounds. However, very few studies have been conducted on the saliva matrix to monitor exposure to hazardous solvents. The aim of this study is to establish an analytical method, headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS), by which the saliva matrix can be monitored for multiple compounds with various polarities, such as methyl ethyl ketone (MEK), isopropyl alcohol (IPA), and N,N-dimethyl formamide (DMF) (common solvents used in synthetic leather manufacture), as well as acetone (ACE) and N-methyl formamide (NMF) (metabolites of IPA and DMF, respectively). We studied this technique as an alternative biological monitoring method for investigating exposure to hazardous solvents. A Carboxen/Polydimethylsiloxane (CAR/PDMS 75 microm) fiber coating was employed for this study, and various extraction and desorption parameters were evaluated. The extraction efficiency and reproducibility of analyses was improved by pre-incubation. The limits of detection were 0.004, 0.003, 0.006, 0.05, and 0.10 microg/mL for ACE, MEK, IPA, DMF, and NMF, respectively. Method validation was performed on standards spiked in blank saliva, and a correlation was made between HS-SPME and traditional solvent pretreatment methods. It was found that correlation coefficients (r) were greater than 0.996 for each analyte, with no significant differences (p>0.05) between two methods. However, the SPME method achieved lower limits of detection, with good accuracy (recovery 95.3-109.2%) and precision (1.17-8.22% CV) for both intra- and inter-assay, when quality control samples were analyzed for all five compounds. The partition coefficient for each compound between the headspace of the saliva sample and the CAR/PDMS fiber coating was 90.9, 170.1, 36.4, 3.70 and 0.92 for ACE, MEK, IPA, DMF and NMF, respectively. Real sample analyses were performed on workers in a synthetic leather factory. In summary, the SPME method is a highly versatile and flexible technique for chemical measurement, and we demonstrate its application for monitoring biological exposure to hazardous solvents. Saliva monitoring using sensitive SPME approaches for determining workplace exposure should prove useful as an alternative exposure monitoring method.

Road Traffic Noise, Air Pollutants, and the Prevalence of Cardiovascular Disease in Taichung, Taiwan.

Background: A few studies have investigated the interaction between exposure to road traffic noise, air pollutants, and cardiovascular disease (CVD), but their results were inconsistent. This cross-sectional study investigated whether road traffic noise, particulate matter with dynamic diameter less than 10 µm (PM10) and nitrogen dioxides (NO2) exposure were independently associated with the risk of CVD. Methods: We recruited 663 volunteers who had been living near main roads for more than three years in 2008. Information concerning the subjects' home addresses was combined with noise measurements at 42 locations and annual average of air pollutants from 2 monitoring stations to estimate individual exposure. Multivariate logistic regression was used to calculate the odds ratio (OR) for diagnosed CVD, adjusting for potential confounders and co-exposure. Results: Only per 5-dBA increase in road traffic noise was significantly associated with elevated risk of CVD (adjusted OR = 2.23, 95% confidence interval (CI) = 1.26⁻3.93) in the single-exposure models. Such association was aggravated (adjusted OR = 2.96, 95% CI = 1.41⁻6.23) after adjustment for total traffic and PM10 or NO2 in the two-exposure models. Conclusions: Road traffic noise exposure may be associated with the increasing prevalence of CVD. No synergistic association was observed between co-exposure to noise and air pollutants and the risk of CVD.

Temporal and spatial variations in road traffic noise for different frequency components in metropolitan Taichung, Taiwan.

Road traffic noise exposure has been associated with auditory and non-auditory health effects, but few studies report noise characteristics. This study determines 24-h noise levels and analyzes their frequency components to investigate associations between seasons, meteorology, land-use types, and traffic. We set up 50 monitoring stations covering ten different land-use types and conducted measurements at three times of the year to obtain 24-h-average A-weighted equivalent noise levels (LAeq,24h) and frequency analyses from 2013 to 2014 in Taichung, Taiwan. Information on land-use types, road parameters, traffic flow rates, and meteorological variables was also collected for analysis with the annual averages of road traffic noise and its frequency components. The annual average LAeq,24h in Taichung was 66.4 ± 4.7 A-weighed decibels (dBA). Significant differences in LAeq,24h and frequency components were observed between land-use types (all p-values < 0.001), but not between seasons, with the highest two noise levels of 71.2 ± 1.0 dBA and 70.0 ± 2.6 dBA measured in stream-channel and commercial areas, with the highest component being 61.4 ± 5.3 dBA at 1000 Hz. Road width, traffic flow rates, and land-use types were significantly associated with annual average LAeq,24h (all p-values < 0.050). Noise levels at 125 Hz had the highest correlation with total traffic (Spearman's coefficient = 0.795) and the highest prediction in the multiple linear regression (R2 = 0.803; adjusted R2 = 0.765). These findings reveal the spatial variation in road traffic noise exposure in Taichung. The highest correlation and predictive capacity was observed between this variation and noise levels at 125 Hz. We recommend that governmental agencies should take actions to reduce noise levels from traffic vehicles.

Acute effects of noise exposure on 24-h ambulatory blood pressure in hypertensive adults.

OBJECTIVE: Noise exposure is associated with elevated blood pressure, but the effects on susceptible workers have not been reported. This repeated-measure study investigated the effects of noise exposure on 24-h ambulatory blood pressure among hypertensive, pre-hypertensive, and normotensive adults. METHODS: We enrolled 113 volunteers in an occupational cohort in 2009. Individual noise exposure and personal blood pressure were measured simultaneously over 24 h on working and non-working days. Linear mixed-effects regressions were used to estimate the effects on SBP and DBP by controlling for potential confounders. RESULTS: Each A-weighted decibel (dBA) increase in a 30-min time-lagged exposure was associated with transient elevations of work-time SBP [0.30 (95% confidence interval: 0.06, 0.54) mmHg] on working days as well as sleep-time SBP [0.39 (0.12, 0.66) mmHg] and DBP [0.33 (0.14, 0.51) mmHg] on non-working days among 19 hypertensive adults. In contrast, 46 normotensive workers had transient increases in work-time SBP [0.16 (0.03, 0.29) mmHg] and DBP [0.25 (0.15, 0.34) mmHg] on working days as well as sleep-time SBP [0.17 (0.06, 0.29) mmHg] and DBP [0.21 (0.14, 0.29) mmHg] on non-working days caused by a 1-dBA increase in the current exposure. All groups had sustained increases in 24-h average ambulatory SBP and DBP induced by noise exposure on 2 days, but the hypertensive workers had the most pronounced increase in SBP. CONCLUSION: Hypertensive adults are more susceptible to noise exposure with a greater effect on ambulatory SBP. These results suggest a need for more protection for this subpopulation.

Laboratory and field validations of a solid-phase microextraction device for the determination of ethylene oxide.

Laboratory and field evaluations were performed to validate a solid-phase microextraction (SPME) device that was used as a diffusive sampler. Hydrogen bromide (HBr) was loaded onto the carboxen-polydimethylsiloxane (CAR-PDMS) fiber for the determination of ethylene oxide (EtO) with on-fiber derivatization. For laboratory evaluations, known concentrations of ethylene oxide around the threshold limit values (TLV)/time-weighted average and specific relative humidities (RHs) were generated by syringe pumps in a dynamic generation system. The SPME diffusive samplers and the commercially available 3M 3551 passive monitors were placed side-by-side in an exposure chamber which was designed to allow measurement of face velocities, temperatures, exposing vapor concentrations, and RHs. Field validations with both SPME diffusive sampler and 3M 3551 passive monitors were also performed. The correlations between the results from both SPME device and 3M 3551 passive monitor were found to be linear (r > 0.9699) and consistent (slope approximately equal to 1.12 +/- 0.07). However, the variations of diffusion coefficients at different temperatures needs to be considered and the adjustment of sampling constant was a must when sampling at temperatures different from 25 degrees C.

Evaluation of current biological exposure index for occupational N, N-dimethylformamide exposure from synthetic leather workers.

The aim of this study was (1) to investigate the correlation between external exposure to N, N-dimethylformamide (DMF) and urinary excretion of DMF and N-methylformamide; (2) to assess whether the correspondence between the current occupational exposure limit setting and recommended urinary biological exposure index is substantial; and (3) to evaluate whether coexposure to toluene, methyl ethyl ketone, and ethyl acetate has an effect on urinary excretion of DMF and N-methylformamide (NMF). Urinary DMF and NMF were significantly correlated (P < 0.01) with one another and also significantly correlated with airborne DMF (P < 0.01) over the range of 1.55 to 152.8 mg/m. Urinary DMF can be considered a complementary marker for short-term exposure. Urinary concentration of NMF and DMF, corresponding to the 8-hour exposure to airborne DMF at 30 mg/m, was estimated to 38.4 mg/L or 39.4 mg/g creatinine for NMF and to 0.92 mg/L or 0.96 mg/g creatinine for DMF.

Noise frequency components and the prevalence of hypertension in workers.

Epidemiological studies have demonstrated a relationship between noise exposure and hypertension, but the association between hypertension and noise frequency components remains unclear. This cross-sectional study investigated the association between noise exposure at different frequencies and the prevalence of hypertension in 188 screw-manufacturing workers. Participants were divided into one high-noise-exposure group (≥80 A-weighted decibel, [dBA]; n=68) and two reference groups, including 68 low-noise-exposure workers (75.8±3.2 dBA) and 52 office workers (61.5±0.5dBA). Personal noise exposure and environmental octave-band analyses were performed at work. Multiple logistic regression models were used to estimate odds ratios (ORs) for hypertension between different noise-exposure categories after adjustment for potential confounders. Male workers exposed to noise levels at high frequencies of 2000, 4000 or 8000Hz had a higher but non-significant risk of hypertension. Those exposed to ≥80dBA for 2-4years, 4-6years and more than 6years had a 4.43-fold (95% CI=1.21-16.15), 1.21-fold (95% CI=0.35-4.21) and 0.95-fold (95% CI=0.16-5.60) risk of hypertension, respectively, compared with reference workers. A significant association was only observed in male workers exposed to ≥70dBA at 4000Hz for 2-4years (adjusted OR=4.22; 95% CI=1.15-15.49) and was not found at other frequencies for any periods. These findings suggest that occupational noise exposure above 80dBA for specific periods may be associated with hypertension, and noise frequency at 4000Hz may have the greatest effect on hypertension.

Application of solid phase microextraction on dental composite resin analysis.

A direct immersion solid phase microextraction (DI-SPME) method was developed for the analysis of dentin monomers in saliva. Dentine monomers, such as triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA) and 2,2-bis-[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-propane (Bis-GMA), have a high molecular weight and a low vapor pressure. The polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber with a medium polarity was employed for DI-SPME, and 215 nm of detection wavelength was found to be optimum in the chromatogram of HPLC measurement. The calibration range for DI-SPME was 0.30-300 µg/mL with correlation coefficients (r) greater than 0.998 for each analyte. The DI-SPME method achieved good accuracy (recovery 96.1-101.2%) and precision (2.30-8.15% CV) for both intra- and inter-day assays of quality control samples for three target compounds. Method validation was performed on standards dissolved in blank saliva, and there was no significant difference (p>0.2) between the DI-SPME method and the liquid injection method. However, the detection limit of DI-SPME was as low as 0.03, 0.27 and 0.06 µg/mL for TEGDMA, UDMA and Bis-GMA, respectively. Real sample analyses were performed on commercial dentin products after curing for the leaching measurement. In summary, DI-SPME is a more sensitive method that requires less sample pretreatment procedures to measure the resin materials leached in saliva.

Effects of co-exposure to noise and mixture of organic solvents on blood pressure.

OBJECTIVES: Independent exposure to noise or organic solvents is reported to be associated with cardiovascular effects, but the effect of joint exposure is unclear. The present study aimed to investigate effects of noise, a mixture of organic solvents (N,N-dimethylformamide (DMF) and toluene) and their interaction on hypertension. METHODS: We recruited 59 volunteers working in a synthetic leather manufacturing company during 2005-2006. Both personal noise exposure and airborne co-exposure to DMF and toluene at work were measured and used to calculate the mixed hazard index (HI). Multivariate logistic regressions were conducted to estimate between-group differences of hypertension by controlling for potential confounders. RESULTS: We found that 18 co-exposure workers (82.22 +/- 2.70 dBA and a mixed HI of 0.53 +/- 0.20) had the highest prevalence of hypertension (55.6%) compared to 15 solvent-exposure workers (a mixed HI of 0.32 +/- 0.18; 46.7%), 9 noise-exposure workers (84.13 +/- 2.30 dBA; 44.4%) and 17 low-exposure workers (11.8%). The adjusted odds ratio (OR) of hypertension compared to low-exposure workers increased from 7.9 times (95% confidence interval (CI)=0.9-66.3; p=0.06) in solvent-exposure workers and 9.1 times (OR=9.1, 95% CI=1.0-81.1; p<0.05) in noise-exposure workers to 13.5 times (95% CI=1.5-117.8; p<0.05) in co-exposure workers. CONCLUSIONS: Our findings suggest that co-exposure to noise, DMF and toluene is associated with hypertension in synthetic leather workers. Simultaneous exposure to noise and a mixture of organic solvents may have a sub-additive effect on the risk of hypertension.

Modeling organic solvents permeation through protective gloves.

Several researchers have studied the diffusion of organic solvents through chemical protective gloves and have estimated the diffusion coefficients by using various models. In this study, permeation experiments of benzene, toluene, and styrene through nitrile and Neoprene gloves were conducted using the ASTM F-739 standard test method. The diffusion coefficients were estimated using several models from the literature. Using a one-dimensional diffusion equation based on Fick's second law and the estimated diffusion coefficients, the permeation concentrations were simulated and compared with the experimental results. The modeling results indicated that the solubility of the solvent in the glove materials obtained by immersion tests was not an appropriate boundary condition for organic solvent permeation through the polymer gloves. The modeling work of this study will assist industrial hygienists to assess exposure of chemicals to workers through the chemical protective gloves.

The effects of co-exposure to methyl ethyl ketone on the biological monitoring of occupational exposure to N,N-dimethylformamide.

OBJECTIVES: (1) To assess whether urinary N,N-dimethylformamide (U-DMF) is suitable as a biomarker when co-exposure to methyl ethyl ketone (MEK) exists, and to evaluate whether it is suitable as an exposure biomarker of DMF. (2) To examine whether the co-exposure to MEK affects the characteristics of U-NMF and U-DMF. (3) To investigate if the difference in creatinine-adjusted and non-adjusted measurements of urinary biomarkers of DMF exposure is substantial. METHODS: Personal exposure monitoring of N,N-dimethylformamide (DMF) and MEK on 11 synthetic-leather workers was performed for 5 consecutive days. Daily post-shift urine for each individual was collected and was analyzed for urinary N-methylformamide (U-NMF) and U-DMF levels on both non-adjusted and creatinine-adjusted bases. RESULTS: Both U-NMF and U-DMF showed significant associations with airborne DMF. Positive and significant associations between U-NMF and U-DMF on either a non-adjusted basis or a creatinine-adjusted basis were found. Satisfactory linear associations ( P<0.01) between all kinds of urinary biomarkers and DMF exposure were found. The co-exposure to MEK exerted more effect on the relationship of airborne DMF to U-DMF than to U-NMF. CONCLUSIONS: U-DMF is detectable when occupational DMF exposure is near or below the occupational exposure limit of 10 ppm. In view of the performance of sensitivity, specificity, and positive predictive value, U-NMF, in general, is superior to U-DMF. However, on a par with other findings in this and previous studies, U-DMF might be considered as a complimentary biomarker of exposure to DMF in addition to U-NMF. No distinction between creatinine-adjustment or non-adjustment for urine specimens was found in the biological monitoring of DMF exposure. Further exploration of the influence of co-exposure to MEK at higher exposure is warranted.

Relationship between blood lead levels and renal function in lead battery workers.

OBJECTIVES: The aim of this study was to investigate the correlation between blood lead (PbB) levels and renal function indices of blood-urea nitrogen (BUN), serum creatinine (SC) and uric acid (UA) among lead battery workers with exposure to lead. METHODS: A total of 229 workers of both genders from two lead battery factories were recruited in this cross-sectional study. The personal airborne and blood samples were collected on the same day. The airborne lead (PbA) and PbB levels, and individual renal function parameters were measured and statistically analyzed. RESULTS: A positive correlation between PbB levels and individual renal function index of BUN, SC, and UA was found ( P<0.01). The PbB levels and renal function indices showed significant difference between male and female workers. Based on a multiple regression model, an increment of 10 micro g/dl PbB produced an increase of 0.62 mg/dl BUN, after being adjusted for work duration and age, and an increase of 0.085 mg/dl UA, after being adjusted for gender and body weight. Workers with PbB 60 microg/dl showed a positive dose-effect relationship with significant difference in BUN ( P<0.001) and UA ( P<0.05), and the percentage of workers with BUN and UA over the reference value also showed an increasing trend. CONCLUSION: Blood-urea nitrogen and uric acid could be considered as suitable prognostic indicators of renal dysfunction in lead-exposed workers. Our results showed that PbB levels higher than 60 micro g/dl had increasing chances of inducing adverse renal effects.