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

Hematological variations in healthy participants exposed 2 h to propylene glycol ethers under controlled conditions

Glycol ethers are solvents used in a plethora of occupational and household products exposing the users to potential toxic effects. Several glycol ethers derived from ethylene glycol induce hematological toxicity, such as anemia in workers. The exposure effects on blood cells of glycol ethers derived from propylene glycol are unknown in humans. The aim of our study was to evaluate blood parameters indicative of red blood cell (RBC) hemolysis and oxidative stress in participants exposed to propylene glycol (propylene glycol monobutyl ether (PGBE) and propylene glycol monomethyl ether (PGME)), two extensively used propylene glycol derivatives worldwide. Seventeen participants were exposed 2 h in a control inhalation exposure chamber to low PGME (35 ppm) and PGBE (15 ppm) air concentrations. Blood was regularly collected before, during (15, 30, 60, and 120 min), and 60 min after exposure for RBC and oxidative stress analyses. Urine was also collected for clinical effects related to hemolysis. Under the study conditions, our results showed that the blood parameters such as RBCs, hemoglobin concentration, and white blood cells tended to increase in response to PGME and PGBE exposures. These results raise questions about the possible effects in people regularly exposed to higher concentrations, such as workers.

Blood absorption toxicokinetics of glycol ethers after inhalation: A human controlled study

Glycol ethers are organic solvents present in countless products for professional and domestic use. The main toxicological concerns are hematotoxicity, respiratory and reproductive toxicity. The general population can be exposed when using products containing one or several glycol ethers that evaporate or if sprayed, generate aerosols that can be inhaled. The rate at which glycol ethers enters blood following inhalation exposure are unknown in humans, and chemical risk assessors only rely on animal and in vitro toxicity studies. Propylene glycol monomethyl ether (PGME) and propylene glycol monobutyl ether (PGBE) are two examples of glycol ethers used worldwide. Our study aimed to provide human toxicokinetic data after inhalation exposure of low PGME and PGBE concentrations tested alone or in mixture. Healthy participants (n = 28) were exposed to 35 ppm (131 mg/m³) of PGME and 15 ppm (i.e., 83 mg/m³) of PGBE for 2 or 6 h. Blood was regularly collected during the exposure sessions. PGME and PGBE were immediately bioavailable in blood during exposure, and the mean absorption rates were up to 13 μg/L/min and 2.45 μg/L/min, respectively. Maximum mean blood concentration (Cmax) was 2.91 mg/L and 0.41 mg/L for PGME and PGBE. The cumulative internal doses over time (area under the curve, AUC) were 11 mg∗h/L and 1.81 mg∗h/L for PGME and PGBE. PGME and PGBE total blood uptake could possibly be higher in physically active individuals, such as workers. We recommend that glycol ethers present on the market undergo toxicological testing with the internal doses we found in our toxicokinetic study.

Hepatic effects among workers exposed to ethylene glycol monoethyl ether acetate

Data about hepatic effects of ethylene glycol ethers had been limited and inconsistent. In this study, we determined whether ethylene glycol monoethyl ether acetate (EGEEA) was a hepatotoxin in exposed workers. Workers from one silk-screening shop (n=29), using EGEEA as the major cleaning solvent, were recruited as high exposure group. Another group of workers with indirect and low exposure to EGEEA (n=57) were selected as the comparison group. Air concentration of EGEEA was measured by 8-h personal sampling. The mean of air EGEEA concentration in the high exposure group was 7.41-16.5 ppm. The mean of air EGEEA concentration in the low exposure group was 0.07-3.62 ppm. Liver function profiles showed that the AST, ALT, ALP and gamma GT in both male and female EGEEA-exposed workers were not significantly different from those in the comparison group. After adjustment for potential confounders such as gender, body mass index, hepatitis B status, and duration of employment, no difference in hepatic dysfunction were found between exposed and comparison groups. In addition, a two-year follow-up study of these EGEEA-exposed workers, no significant change in hepatic function was noted either. The findings suggest that EGEEA is not a hepatotoxin in this workplace.

Hematological effects of four ethylene glycol monoalkyl ethers in short-term repeated exposure in rats

This study was carried out to compare the hematological effects of 2-methoxyethanol (ME), 2-ethoxyethanol (EE), 2-isopropoxyethanol (IPE), and 2-butoxyethanol (BE) in short-term studies in rats. Male rats were subcutaneously treated with ME or EE at a dosage of 0, 1.25, 2.5 and 5.0 mM/kg in saline, 5 days per week, for 4 weeks. Other rats were exposed to IPE or BE at doses of 0, 0.25, 0.5, 0.75 and 1.25 mM/kg in the same manner. Administration of each chemical, except of ME, resulted in a time- and dose-dependent swelling of erythrocytes as evidenced by an increase in mean corpuscular volume (MCV). Subsequently, red blood cells (RBC), packed cell volumes (PCV), hemoglobin concentration (HGB), and mean cell hemoglobin concentration (MCHC) decreased. Furthermore, an increase in mean cell hemoglobin (MCH) and reticulocyte counts was observed. The onset of hemolysis induced by EE, IPE or BE was faster than after ME administration. While in rats exposed to ME hematological changes were strongly pronounced and progressively increased with exposure time beginning from the day 11, those in animals treated with EE were rather persisted at low constant level for all exposure period. In contrast, the rats exposed to IPE and BE demonstrated the dramatic hematological changes more pronounced in case of BE than IPE at the beginning of exposure (on day 4). Despite of exposure duration, these changes were regressed, although the decrease in RBC and MCHC and the increase in MCV and MCH in rats treated with highest doses of both compound (0.5, 0.75, and 1.25 mM/kg) were more persistent, probably due to selective hemolysis of the aged erythrocytes. In addition, significant leukopenia due to reduction of lymphocytes in rats exposed to ME was observed. In summary, this study demonstrated no tolerance to ME- and EE-induced intravascular hemolysis developed under these experimental conditions. On the contrary, tolerance to IPE- and BE-induced hemolysis in rats exposed to these compounds was prompted.

Hematological Follow‐up of an Intervention Program Adding Rubber Glove‐Wearing to Local Ventilation for 2‐Ethoxyethanol Acetate‐Exposed Workers

The objective of this study was to evaluate an intervention program, implemented in year 1999, of wearing rubber gloves in addition to engineering control, and to follow-up the hematological effects of 2-ethoxyethanol acetate (2-EEA) exposure among workers in a silk-screening factory. All workers from the printing department with direct exposure to 2-EEA were recruited as the exposed group. Workers from the other departments were recruited as the comparison group. Hematological parameters were measured during health surveys conducted 3 times every two years. Information on personal characteristics and working habits was obtained through a structured questionnaire. More female workers were involved in manual printing resulting in higher exposure to 2-EEA. Hemoglobin and haematocrit levels in female exposed workers were significantly lower than those of female comparison workers in the 1st (1998) health survey, but not in the 2nd (2000) and 3rd (2002) health surveys. No difference was found between male exposed and comparison workers for all three surveys. Longitudinal analysis after adjusting for confounders using the general estimating equation model showed the hemoglobin, haematocrit, and RBC count were significantly higher for 2-EEA exposed workers than comparison workers across the 3 surveys (n=42). The results show that wearing rubber gloves in addition to local ventilation was effective at preventing direct dermal exposure to 2-EEA and ameliorated the hematological effects of 2-EEA exposure.

Correlation between urinary methoxyacetic acid and exposure of ethylene glycol dimethyl ether in a lithium battery plant

OBJECTIVE

To examine the correlation between airborne ethylene glycol dimethyl ether (EGdiME) exposures and the urinary methoxyacetic acid (MAA) and to approach the issue of a permissible exposure limit for EGdiME.

METHODS

The survey was conducted on Thursday. Workers occupationally exposed to EGdiME, as well as nonexposed controls, were studied in combination with one of the authors, who was coincidentally exposed to EGdiME while carrying out the study. Air levels of EGdiME were determined by personal sampling on passive gas tubes. Urine was collected from nine control subjects and ten workers immediately before and after the shift, and from one of the authors at intervals during 12 h. The analyses of EGdiME in air and MAA in urine were performed by gas chromatography with flame ionization detection.

RESULTS

The time-weighted average (TWA) air levels of EGdiME ranged from 0.7 to 10.5 ppm during 8 h work shifts. The urinary levels of MAA in one of the authors increased continuously during exposure and after the end of exposure. The levels of urinary MAA in the exposed workers were significantly higher than those in the control subjects. On the other hand, the postshift values were higher than the preshift values in the exposed workers, but the difference was not significant. A linear correlation was found between the TWA air levels of EGdiME and creatinine-adjusted MAA levels in urine collected at the end of the shift (r = 0.933; P < 0.0001). According to our equation, a linear extrapolation to the biological limit value recommended by Shih et al. (1999) of 40 mg MAA/g crea indicated an average inhalation exposure to EGdiME over the workweek of 12 ppm.

CONCLUSIONS

These results indicate that the determination of MAA in urine is suitable for use in the biological monitoring of EGdiME exposure.

Glycol ethers and semen quality: a cross-sectional study among male workers in the Paris Municipality

OBJECTIVES

Apparent increases in human male reproductive disorders, including low sperm production, may have occurred because of increased chemical exposure. Various glycol ether-based solvents have pronounced adverse effects on sperm production and male fertility in laboratory animals. The authors investigated the effects of past and current exposure to glycol ether-containing products on semen quality and reproductive hormones among men employed by the Paris Municipality.

METHODS

Between 2000 and 2001 the authors recruited 109 men who gave semen, blood and urine samples and underwent an andrological examination. Information on lifestyle, occupation, exposure and medical history was obtained by interview. According to their job and chemical products used during the period 1990-2000, men were classified as either occupationally exposed or non-exposed. Current exposure levels to glycol ethers at the time of the study were evaluated by biological monitoring of six urinary metabolites.

RESULTS

Previous exposure to glycol ethers was associated with an increased risk for sperm concentration, for rapid progressive motility and for morphologically normal sperm below the World Health Organization semen reference values. No effect of previous glycol ether exposure on hormones levels was observed. By contrast, current glycol ether exposure levels were low and not correlated with either seminal quality or hormone levels.

CONCLUSIONS

This study suggests that most glycol ethers currently used do not impact on human semen characteristics. Those that were more prevalent from the 1960s until recently may have long lasting negative effects on human semen quality.

The development and regulation of occupational exposure limits in Taiwan

The occupational exposure limits (OELs) in Taiwan was promulgated in 1974 and has been revised five times since then. Many of the OELs were adopted from the most recent ACGIH TLVs and US OSHA PELs. A total of 483 chemicals were listed in the current Taiwan OELs Standard. The procedures of OELs development in Taiwan include the IOSH organized a recommended exposure limits (RELs) Committee to select the target chemicals and to recommend the RELs through literature review based on the health effects in the first stage, then, the CLA put policy needs, economical and technical feasibility into consideration and set up the final OELs at the second stage. A standard operation manual of RELs Committee has been developed. Based on our experience, several issues including the participation of representatives from a comprehensive spectrum, communication/education and training/enforcement, continuous collection of the local exposure data and health hazard information, use of health risk assessment, consideration of economic, and technical feasibility, as well as the globalization and information and experience sharing are critical in developing the appropriate OELs. Three examples including benzene, crystalline silica, and 2-methoxy ethanol are given to demonstrate the operation of system.

Printed circuit board industry

The printed circuit board is the platform upon which microelectronic components such as semiconductor chips and capacitors are mounted. It provides the electrical interconnections between components and is found in virtually all electronics products. Once considered low technology, the printed circuit board is evolving into a high-technology product. Printed circuit board manufacturing is highly complicated, requiring large equipment investments and over 50 process steps. Many of the high-speed, miniaturized printed circuit boards are now manufactured in cleanrooms with the same health and safety problems posed by other microelectronics manufacturing. Asia produces three-fourths of the world's printed circuit boards. In Asian countries, glycol ethers are the major solvents used in the printed circuit board industry. Large quantities of hazardous chemicals such as formaldehyde, dimethylformamide, and lead are used by the printed circuit board industry. For decades, chemically intensive and often sloppy manufacturing processes exposed tens of thousands of workers to a large number of chemicals that are now known to be reproductive toxicants and carcinogens. The printed circuit board industry has exposed workers to high doses of toxic metals, solvents, acids, and photolithographic chemicals. Only recently has there been any serious effort to diminish the quantity of lead distributed worldwide by the printed circuit board industry. Billions of electronics products have been discarded in every region of the world. This paper summarizes recent regulatory and enforcement efforts.

Urinary methoxyacetic acid as an indicator of occupational exposure to ethylene glycol dimethyl ether

OBJECTIVE

To investigate whether methoxyacetic acid (MAA) is the metabolite of ethylene glycol dimethyl ether (EGdiME) in humans and whether its metabolite in urine can be used as a biomarker for exposure to EGdiME.

METHODS

Workers occupationally exposed to EGdiME, as well as nonexposed controls, were studied. Urine samples were collected from 20 control subjects and, on Friday postshift, from 14 workers. The identification and quantification of the metabolite were performed by gas chromatography/mass spectrometry (GC/MS) and GC/FID, respectively. Air samples were collected on activated charcoal tubes by area sampling with battery-operated pumps. The glycol ether was analyzed by GC/FID.

RESULTS

GC/MS clearly showed the metabolite of EGdiME to be MAA. Urinary MAA levels in the control subjects (background levels) were 0.0-0.3 mg/g crea. The levels of urinary MAA in the solvent-exposed workers were significantly (P<0.0001) higher than those in the control subjects. In the eight workers exposed to an average of 0.3 ppm of EGdiME and the six workers exposed to an average of 2.9 ppm, the mean urinary MAA level was 1.08 (range 0.6-1.5) mg/g crea and 9.33 (range 5.7-18.1) mg/g crea, respectively. These results can be explained by differences in the exposure intensity.

CONCLUSIONS

Our results suggest that MAA is the metabolite of EGdiME, and that MAA in urine may be used for biological monitoring of EGdiME exposures.

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.

Hepatic Effects in Workers Exposed to 2-Methoxy Ethanol

The objective of this study was to investigate the effects of 2-ME on hepatic function in exposed workers. Fifty-three impregnation workers from two copper-clad laminate-manufacturing factories using 2-ME as a solvent were recruited as the exposed group. Another group of 121 lamination workers with indirect exposure to 2-ME was recruited as the comparison group. Environmental monitoring of air 2-ME concentrations and biological monitoring of urine 2-methoxy acetic acid concentrations were performed. Venous blood was collected for blood biochemistry analyses. Liver function examination results showed that the aspartate amino transferase, alanine amino transferase, and gamma-glutamyl transferase in the 2-ME-exposed workers were not significantly different from those in the comparison workers. After adjustment for hepatitis carrier status, gender, body mass index, and duration of employment, no difference were found between exposed and comparison groups. We conclude that 2-ME was not a hepatotoxin.

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.

Proposed occupational exposure limits for select ethylene glycol ethers using PBPK models and Monte Carlo simulations

Methoxyethanol (ethylene glycol monomethyl ether, EGME), ethoxyethanol (ethylene glycol monoethyl ether, EGEE), and ethoxyethyl acetate (ethylene glycol monoethyl ether acetate, EGEEA) are all developmental toxicants in laboratory animals. Due to the imprecise nature of the exposure data in epidemiology studies of these chemicals, we relied on human and animal pharmacokinetic data, as well as animal toxicity data, to derive 3 occupational exposure limits (OELs). Physiologically based pharmacokinetic (PBPK) models for EGME, EGEE, and EGEEA in pregnant rats and humans have been developed (M. L. Gargas et al., 2000, Toxicol. Appl. Pharmacol. 165, 53-62; M. L. Gargas et al., 2000, Toxicol. Appl. Pharmacol. 165, 63-73). These models were used to calculate estimated human-equivalent no adverse effect levels (NAELs), based upon internal concentrations in rats exposed to no observed effect levels (NOELs) for developmental toxicity. Estimated NAEL values of 25 ppm for EGEEA and EGEE and 12 ppm for EGME were derived using average values for physiological, thermodynamic, and metabolic parameters in the PBPK model. The uncertainties in the point estimates for the NOELs and NAELs were estimated from the distribution of internal dose estimates obtained by varying key parameter values over expected ranges and probability distributions. Key parameters were identified through sensitivity analysis. Distributions of the values of these parameters were sampled using Monte Carlo techniques and appropriate dose metrics calculated for 1600 parameter sets. The 95th percentile values were used to calculate interindividual pharmacokinetic uncertainty factors (UFs) to account for variability among humans (UF(h,pk)). These values of 1.8 for EGEEA/EGEE and 1.7 for EGME are less than the default value of 3 for this area of uncertainty. The estimated human equivalent NAELs were divided by UF(h,pk) and the default UFs for pharmacodynamic variability among animals and among humans to calculate the proposed OELs. This methodology indicates that OELs (8-h time-weighted average) that should protect workers from the most sensitive adverse effects of these chemicals are 2 ppm EGEEA and EGEE (11 mg/m(3) EGEEA, 7 mg/m(3) EGEE) and 0.9 ppm (3 mg/m(3)) EGME. These recommendations assume that dermal exposure will be minimal or nonexistent.