Urine Excretion, Organ Distribution, and Placental Transfer of 6PPD and 6PPD-Quinone in Mice and Potential Developmental Toxicity through Nuclear Receptor Pathways

The rubber antioxidant 6PPD has gained significant attention due to its highly toxic transformation product, 6PPD-quinone (6PPDQ). Despite their detection in urines of pregnant women, the placental transfer and developmental toxicity of 6PPD and 6PPDQ are unknown. Here, we treated C57Bl/6 mice with 4 mg/kg 6PPD or 6PPDQ to investigate their urine excretion and placental transfer. Female and male mice exhibited sex difference in excretion profiles of 6PPD and 6PPDQ. Urine concentrations of 6PPDQ were one order of magnitude lower than those of 6PPD, suggesting lower excretion and higher bioaccumulation of 6PPDQ. In pregnant mice treated with 6PPD or 6PPDQ from embryonic day 11.5 to 15.5, 6PPDQ showed ∼1.5-8 times higher concentrations than 6PPD in placenta, embryo body, and embryo brain, suggesting higher placental transfer of 6PPDQ. Using in vitro dual-luciferase reporter assays, we revealed that 6PPDQ activated the human retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) at concentrations as low as 0.3 μM, which was ∼10-fold higher than the concentrations detected in human urines. 6PPD activated the RXRα at concentrations as low as 1.2 μM. These results demonstrate the exposure risks of 6PPD and 6PPDQ during pregnancy and emphasize the need for further toxicological and epidemiological investigations.

[Determination of 2, 4-toluenediamine in urine by gas chromatography]

OBJECTIVE

To establish a method for determining the content of 2,4-toluenediamine, a urinary metabolite of toluene diisocyanate, by gas chromatography.

METHODS

Urine samples were collected, and acidification, extraction, derivatization, separation with a capillary column, and detection with an electron capture detector were performed. The target compound was qualified by retention time and quantified by peak area.

RESULTS

The concentration of 2, 4-toluenediamine showed a linear relationship with peak area within 0.0∼40 ng/ml, with a correlation coefficient 0.9995; the limit of detection was 0.44 ng/ml, the lower limit of quantification was 1.47 ng/ml, the relative standard deviation was 1.85%∼4.05%; the recovery rate was 97.98%∼99.28%.

CONCLUSION

The method has the advantages of high sensitivity and high accuracy and can be used for determination of 2, 4-toluenediamine in urine.

Biological monitoring as a valid tool to assess occupational exposure to mixtures of 2,4-:2,6-toluene diisocyanate

BACKGROUND AND OBJECTIVES

Despite its advantages over environmental monitoring, biological monitoring of exposure to 2,4-:2,6-toluene diisocyanate (TDI) mixtures is still underused. The present study was designed in order to evaluate the feasibility and reliability of biological monitoring in a factory producing polyurethane foam blocks.

METHODS

Airborne TDI isomers were sampled by both static and personal pumps and determined by HPLC with fluorimetric detection. Specific metabolites 2,4- and 2,6-toluenediamine (TDA) were determined by gas chromatography-mass spectrometry on hydrolysed urine samples collected from 16 workers at the beginning of the workweek and both before (BS) and at the end (ES) of the 4th workday. Additional samples were collected at the end of the 1st half-shift and at the beginning of the 2nd half-shift in 5 workers.

RESULTS

In the foam production shop, TDI values were on average about 20 microg/m3, with higher levels in the 2nd half-shift and peak levels in workers operating along the polymerization tunnel. Average TDI levels were significantly correlated with ES TDA concentrations (p < 0.0001). TDA showed a fast urinary elimination phase leading to progressively higher TDA levels either during the shift (5 workers) and at the end-of-shift. A slower elimination phase with a weekly accumulation was demonstrated by values at the beginning of the workweek (higher than in unexposed subjects) and by their elevation in subsequent BS samples.

CONCLUSIONS

The study demonstrates the feasibility and reliability of biological monitoring in workers exposed to 2,4-:2, 6-TDI mixtures. This approach can provide information about both the daily and weekly exposure levels.

Analytical investigations of toxic p-phenylenediamine (PPD) levels in clinical urine samples with special focus on MALDI-MS/MS

Para-phenylenediamine (PPD) is a common chromophoric ingredient in oxidative hair-dyes. In some African countries like Sudan, Egypt and Morocco but also in India this chemical is used alone or in combination with colouring extracts like Henna for dyeing of the hair or the skin. Excessive dermal exposure to PPD mainly leads to the N-mono- and N,N′-diacetylated products (MAPPD, DAPPD) by N-acetyltransferase 1 and 2 (NAT1 and 2) catalyzed reactions. Metabolites and PPD are mainly excreted via renal clearance. Despite a low risk of intoxication when used in due form, there are numerous cases of acute intoxication in those countries every year. At the ENT Hospital - Khartoum (Sudan) alone more than 300 cases are reported every year (∼10% fatal), mostly caused by either an accidental or intended (suicidal) high systemic exposure to pure PPD. Intoxication leads to a severe clinical syndrome including laryngeal edema, rhabdomyolysis and subsequent renal failure, neurotoxicity and acute toxic hepatitis. To date, there is no defined clinical treatment or antidote available and treatment is largely supportive. Herein, we show the development of a quick on-site identification assay to facilitate differential diagnosis in the clinic and, more importantly, the implementation of an advanced analytical platform for future in-depth investigations of PPD intoxication and metabolism is described. The current work shows a sensitive (∼25 µM) wet chemistry assay, a validated MALDI-MS/MS and HPLC-UV assay for the determination of PPD and its metabolites in human urine. We show the feasibility of the methods for measuring PPD over a range of 50–1000 µM. The validation criteria included linearity, lower limit of quantification (LLOQ), accuracy and precision, recovery and stability. Finally, PPD concentrations were determined in clinical urine samples of cases of acute intoxication and the applied technique was expanded to identify MAPPD and DAPPD in the identical samples.

Biological monitoring of TDI-derived amines in polyurethane foam production

BACKGROUND

Toluene diisocyanate (TDI) is used in industry in the production of flexible polyurethane foam, commonly a mixture of the 2,4- and 2,6- isomers. The production process may lead to exposure to diisocyanates which are associated with respiratory disease. A method has been available for the determination of TDI biomarkers in urine for some years.

AIMS

To explore the usefulness of urinary toluenediamine (uTDA) in assessing whether dermal absorption of diisocyanates makes a significant contribution to a worker's total exposure.

METHODS

Twenty-six workers took part in the study. Thirteen workers whose duties brought them into physical contact with uncured polyurethane foam during their shift (handlers) were compared to a control group of 13 workers in the same block plant environment had no physical contact with uncured foam on the day that sampling took place (non-handlers). Creatinine-adjusted uTDA levels in the two groups were compared across a work shift.

RESULTS

Both groups of workers were exposed to similar levels of airborne TDI. Ten handlers were found to have TDA in post-shift urine samples above detection limits compared with two non-handlers (P < 0.05). No clear relationship was found between the level of airborne TDI exposure and post-shift uTDA.

CONCLUSIONS

uTDA provides a useful indication of the contribution which skin absorption makes to total TDI exposure. The results suggest that skin protection when handling uncured polyurethane foam may not receive sufficient consideration.

Analysis of paraphenylenediamine

The toxic Paraphenylenediamine is characterized by infrared spectrophotometry and nuclear magnetic resonance spectroscopy, whereas, high performance liquid chromatography with a refractive index detector was used to determine its purity in the suspect samples using external standardisation. An analytical method for determination of lower traces of paraphenylenediamine in post-mortem biological fluids was developed. This procedure involves deproteneization or hydrolysis followed by liquid-liquid extraction and derivatization with trifluoroacetic anhydride. 1 microL of the extract was then analysed by gas chromatography/iontrap mass spectrometry. Benzidine used as the internal standard for quantification and the extraction recovery test was evaluated to 85%. This method was validated in cases with paraphenylenediamine poisoning.

N-Glucuronidation of the antiepileptic drug retigabine: results from studies with human volunteers, heterologously expressed human UGTs, human liver, kidney, and liver microsomal membranes of Crigler-Najjar type II

Retigabine (D-23129), an N-2-amino-4-(4-fluorobenzylamino)phenylcarbamine acid ethyl ester, is a novel antiepileptic drug which is currently in phase II clinical development. This drug undergoes N-glucuronidation. We aimed to identify the principal enzymes involved in the N-glucuronidation pathway of retigabine and compared our findings with those obtained from human liver (a pool of 30 donors) and kidney microsomes (a pool of 3 donors) and with results from a human absorption, distribution, metabolism, and excretion study upon administration of 200 microCi of [(14)C]-D-23129. Essentially, microsomal assays with UGT1A1 produced only one of the 2 N-glucuronides, whereas UGT1A9 is capable of forming both N-glucuronides. The rates of metabolism for UGT1A9, human liver microsomes, and UGT1A1 were 200, 100, and 100 pmol N-glucuronide per minute per milligram of protein, respectively. At the 50 micromol/L uridine diphosphate glucoronic acid (UDPGA) concentration, UGT1A4 also catalyzed the N-glucuronidation of retigabine, the rates being approximately 5 and 6 pmol/(min.mg protein). With UGT1A9, the production of metabolites 1 and 2 proceeded at a K(m) of 38+/-25 and 45+/-15 micromol/L, whereas the K(m) for retigabine N-glucuronidation by human liver microsomal fractions was 145+/-39 micromol/L. Furthermore, a V(max) of 1.2+/-0.3 (nmol/[min.mg protein]) was estimated for human liver microsomes (4 individual donors). We investigated the potential for drug-drug interaction using the antiepileptic drugs valproic acid, lamotrigine, the tricyclic antidepressant imipramine, and the anesthetic propofol. These are commonly used medications and are extensively glucuronidated. No potential for drug-drug interactions was found at clinically relevant concentrations (when assayed with human liver microsomes or UGT1A9 enzyme preparations). Notably, the biosynthesis of retigabine-N-glucuronides was not inhibited in human liver microsomal assays in the presence of 330 micromol/L bilirubin, and glucuronidation of retigabine was also observed with microsomal preparations from human kidney and Crigler-Najjar type II liver. This suggests that lack of a particular UDP-glucuronosyltransferase (UGT) isoform (eg, UGT1A1 in kidney) or functional loss of an entire UGT1A gene does not completely abolish disposal of the drug. Finally, chromatographic separations of extracts from microsomal assays and human urine of volunteers receiving a single dose of (14)C-retigabine provided clear evidence for the presence of the 2 N-glucuronides known to be produced by UGT1A9. We therefore suggest N-glucuronidation of retigabine to be of importance in the metabolic clearance of this drug.

Improvement in the GC-MS method for determining urinary toluene-diamine and its application to the biological monitoring of workers exposed to toluene-diisocyanate

OBJECTIVES

To develop a simple and sensitive GC-MS method for determining toluene-diamine (TDA) in urine and to apply the method for biological monitoring of workers exposed to toluene-diisocyanate (TDI).

METHODS

After acid hydrolysis of 0.1 ml of urine, diluted tenfold with water, for 1.5 h, the free TDA formed was extracted with dichloromethane, and the heptafluorobutyric anhydride derivative was determined by GC-MS. We applied the method to the biological monitoring of 18 workers who were using an 80:20 mixture of 2,4-TDI and 2,6-TDI.

RESULTS

2,6-TDA and 2,4-TDA were simply determined in 7 min by GC-MS. TDA levels in post-shift urine were well correlated with personal exposure levels of TDI. The correlation was improved by correction with creatinine or specific gravity in the 2,6-isomer, but not in the 2,4-isomer because of low exposure levels. From the correlation equation, the 2,6-TDA level (corrected with creatinine), corresponding to the TDI level of 5 ppb, was calculated to be 31.6 mug/g Cre. TDAs in pre-shift urine also correlated significantly with the personal exposure levels of TDIs, although the slope of the correlations for pre-shift samples was 60%-70% of those for post-shift samples. The correlation between 2,4-TDA and 2,6-TDA levels was significant, although the levels of the 2,4-isomer were less than one-tenth of the 2,6-isomers in both air (personal exposure) and urine.

CONCLUSION

The present method is simple and practicable and can be useful for biological monitoring of TDI workers.

Urinary acetylated metabolites and N-acetyltransferase-2 genotype in human subjects treated with a para-phenylenediamine-containing oxidative hair dye

In the organism of mammals, important detoxification pathways of arylamines are catalysed by N-acetyltransferase 2 (NAT2). A recent case-control epidemiology study suggested that human NAT2 slow acetylators exposed to oxidative hair dyes may be at greater risk to develop bladder cancer. We therefore profiled urinary [(14)C]-metabolites and NAT2 genotype in eight human subjects following treatment with a dark-shade oxidative hair dye containing [(14)C]-para-phenylenediamine (PPD). Genotyping identified three subjects as slow, and five subjects as intermediate NAT2 acetylators. Within 24 h after treatment, the study subjects excreted a mean total of 0.43+/-0.24% of the applied [(14)C] in the urine, where five different metabolites were found. The major urinary metabolites were concluded to be N-mono-acetylated and N,N'-diacetylated PPD. They were present in all urine samples and amounted to 80-95% of the total urinary [(14)C]. Another metabolite, possibly a glucuronic acid conjugate, was found in 6/8 urine samples at 5-13% of the total urinary [(14)C]. All metabolites appeared to be related to PPD, no evidence of the presence of high-molecular weight dye-intermediates or corresponding metabolites was found. The metabolite profile in the study subjects showed no significant differences between the NAT2 intermediate and NAT2 slow acetylator subgroups. Urine of NAT2 slow acetylators contained N-mono-acetylated-PPD at 42.2+/-10.2% and N,N'-di-acetylated-PPD at 54.1+/-7.6% of total urinary radioactivity, while the corresponding values of intermediate acetylators were 46.0+/-8.9% and 45.7+/-9.9%, respectively. Overall, our results suggest that the human acetylation rate of PPD after topical application is independent of the NAT2 genotype status, most likely due to metabolism by epidermal NAT1 prior to systemic absorption.

Human systemic exposure to a [14C]-para-phenylenediamine-containing oxidative hair dye and correlation with in vitro percutaneous absorption in human or pig skin

We investigated the absorption of a commercial [14C]-PPD-containing oxidative dark-shade hair dye in human volunteers as well as in vitro using human or pig ear skin. The hair of eight male volunteers was cut to a standard length, dyed, washed, dried, clipped and collected. Hair, washing water, materials used in the study and a 24-h scalp wash were collected for determination of radioactivity. Blood, urine and faeces were analysed up to 120 h after hair dyeing. An identical [14C]-PPD-containing hair dye formulation was applied in vitro for 0.5 h to human and pig ear skin, and radioactivity was determined in skin compartments after 24 h. In humans, the recovery rate was 95.7+/-1.5% of the applied radioactivity. Washing water, cut hair, gloves, paper towels, caps or scalp wash contained a total of 95.16+/-1.46% of the applied [14C]. Absorbed radioactivity amounted to 0.50+/-0.24% in the urine and 0.04+/-0.04% in the faeces, corresponding to a mean of 7.0+/-3.4 mg [14C]-PPD-equivalents absorbed. Within 24 h after application, most of the radioactivity was eliminated. The Cmax of [14C]-PPD-equivalents in the plasma was 0.087 microgeq/ml, the Tmax was approximately 2 h, and the mean the AUC(0-12h) was 0.67 microgeq h/ml. In vitro tests in human or pig skin found total absorbed amounts of 2.4+/-1.6% (10.6+/-6.7 microgeq/cm2) or 3.4+/-1.7% (14.6+/-6.9 microgeq/cm2), respectively. Percentage-based in vitro results were considerably higher than corresponding in vivo data, whereas, in units of microg/cm2, they corresponded to a total absorbed amount of 7.40 or 10.22 mgeq for human or pig skin, respectively. All results suggested that hair dyeing with oxidative hair dyes produces minimal systemic exposure that is unlikely to pose a risk to human health.

Pharmacokinetic interaction between retigabine and lamotrigine in healthy subjects

PURPOSE

The antiepileptic drugs (AEDs) retigabine (RGB) and lamotrigine (LTG) undergo predominantly N-glucuronidation and renal excretion. This study was performed to evaluate potential pharmacokinetic interactions between both AEDs.

METHODS

Twenty-nine healthy male subjects participated in the study. Group A ( n=14) received single oral 200-mg RGB doses on day 1 and day 7, and 25 mg o.i.d. LTG on days 3-8. Group B ( n=15) received single oral 200-mg LTG doses on day 1 and day 17, and was up-titrated to 300 mg RGB b.i.d. on days 6-20. Blood samples were collected to compare the pharmacokinetics of both AEDs and the N-acetyl metabolite of RGB (AWD21-360) after single and concomitant treatments.

RESULTS

RGB was rapidly absorbed and eliminated with a mean half-life (t(1/2)) of 6.3+/-1.1 h and an apparent clearance (CL/F) of 0.69+/-1.4 l/h/kg. Under co-administration of LTG, mean RGB t(1/2) and area under the plasma concentration-time curve (AUC) were increased by 7.5% ( P=0.045) and 15% ( P=0.006), respectively, while CL/F was decreased by 13% ( P=0.06). Consistent results were obtained for AWD21-360. LTG was moderately rapidly absorbed, eliminated with a mean t(1/2) of 37+/-10.4 h and a CL/F of 0.028+/-0.007 l/h/kg. Under co-administration of RGB, mean LTG t(1/2) and AUC decreased by 15% and 18%, respectively, while CL/F increased by 22% (all parameters, P=0.001).

CONCLUSIONS

RGB and LTG exhibit a modest pharmacokinetic interaction on each other. The slight decline in RGB clearance due to LTG is believed to result from competition for renal elimination rather than competition for glucuronidation. The induction of LTG clearance due to retigabine was unexpected since RGB did not show enzyme induction in various other drug-drug interaction studies. Further studies in patients are needed to assess the clinical relevance of these findings for concomitant treatment with both drugs in the upper recommended dose range.

Simultaneous determination of oxidative hair dye p-phenylenediamine and its metabolites in human and rabbit biological fluids

A liquid chromatography with an electrochemical detector method has been developed for the quantitative measurement for three diamine derivatives (p-phenylenediamine, N,N(')-p-phenylenebisacetamide, and 4-aminoacetanilide) in human urine and rabbit blood, urine, and feces. The detection cell consisted of a glassy carbon electrochemical signal obtained with a supporting electrolyte containing 20% methanol-5mM octylammonium orthophosphate (pH 6.30) as the mobile phase. A comparison of the results obtained from HPLC-UV shows agreement.

LC-MS determination of urinary toluenediamine in workers exposed to toluenediisocyanate

To improve the biological monitoring method for 2,6- and 2,4-toluenediisocyanate (TDI) exposure, we developed a simple and rapid method for analysis of the corresponding urinary metabolites, 2,6- and 2,4-toluenediamine (TDA) using liquid chromatograph-mass spectrometry (LC-MS). One ml of urine was hydrolyzed at 100 degrees C for 1.5 h with H(2)SO(4). Alkalinized hydrolysate was extracted with dichloromethane (DCM) and analyzed by atmospheric pressure chemical ionization (APCI) LC-MS, in positive-ion mode. The mass spectra of TDA isomers showed the protonated molecule [M+H](+), at m/z 123 as the base peak. Calibration curves of 2,6-TDA were linear up to 400 microg/l. TDA isomers in urine of exposed workers as determined by LC-MS correlated well with those obtained by gas chromatography-mass spectrometry. 2,6- and 2,4-TDA were not detected in non-exposed subjects, whereas exposed workers showed urinary levels up to 250 and 63 microg/l, respectively.

Exposure to 2,4- and 2,6-toluene diisocyanate (TDI) during production of flexible foam: determination of airborne TDI and urinary 2,4- and 2,6-toluenediamine (TDA)

Occupational exposure to 2,4- and 2,6-toluene diisocyanate (2,4- and 2,6-TDI) was measured during the production of flexible foam. The usefulness of urinalysis of the TDI-derived amines, 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA), for exposure assessment was compared with air monitoring. Urine samples were collected from 17 employees at two plants. The workers' personal exposure was measured using 1-(2-methoxyphenyl)-piperazine (2MP)-impregnated glass fibre filters for sampling and high-performance liquid chromatography (HPLC) with ultraviolet (UV) and electrochemical (EC) detection for quantification. The limit of detection (LOD) of 2,4- and 2,6-TDI was 0.01 microtg ml(-1) for a 20 microl injection. The precision of sample preparation, expressed as the relative standard deviation (RSD), was 0.6% with UV detection and 0.8% with EC detection at a 2,4-TDI concentration of 0.2 microg ml(-1) (n = 6). For 2,6-TDI, the corresponding RSDs were 0.5% and 0.8%. The urinary 2,4- and 2,6-TDA metabolites were determined after acid hydrolysis as heptafluorobutyric anhydride derivatives by gas chromatography-mass spectrometry. The LOD in urine was 0.35 nmol l(-1) for 2,4-TDA and 0.04 nmol l(-1) for 2,6-TDA. The precision (RSD) of six analyses of human urine spiked to a concentration of 100 nmol l(-1) was 3.7% for 2,4-TDA and 3.6% for 2,6-TDA. There was a trend for linear correlation between urinary TDA concentration and the product of airborne TDI concentration and sampling time. Urinalysis of TDA is proposed as a practical method for assessing personal exposures in workers exposed intermittently to TDI.

The use of electrochemically grown polymers on metallized electrodes to reduce electrode fouling in biological matrices

The use of electrochemically grown polymers has expanded dramatically in the last couple of years, and they are now well established as membranes for immobilizing components. The evidence here for their anti-fouling properties is good. The poly(1,3-diaminobenzene)-covered electrodes performed well in the buffer, urine, plasma and serum samples, but not so well in the blood. The Ru/Rh/Pt, Rh/Rh and the Pt-on-glassy carbon electrodes covered with poly(1,3-diaminobenzene) were the best electrodes in the blood. The Pt disc seemed to exhibit the largest irrepeatability in most of the biological matrices.

Measurement of 2,4-toluenediamine in urine and serum samples from women with Même or Replicon breast implants

The objective of this matched case-control study was to determine whether women with Même or Replicon polyurethane-covered silicone breast implants are exposed to clinically significant levels of free 2,4-TDA from biodegradation of the polyurethane foam. Urine and serum samples were obtained from 61 patients with Même or Replicon breast implants and 61 controls on two separate occasions separated by 10 +/- 3 days. Free TDA was analyzed by gas chromatography combined with negative chemical ionization mass spectrometry with lower limit of quantitation in both urine and serum of 10 pg/ml. The results were correlated with the length of time since implantation. No patients or controls had detectable free 2,4-TDA in their sera. Thirty patients had quantifiable levels of free 2,4-TDA, and 18 had detectable levels in their urine. Controls had no quantifiable levels, but 7 subjects had detectable levels. The biodegradative half-life of the polyurethane foam was estimated to be 2 years. A risk assessment using the cancer potency estimate calculated by the FDA from rat data and the National Academy of Sciences methodology provided a theoretical lifetime risk of approximately one in one million. It was concluded that the polyurethane foam cover on the Même and Replicon breast implants biodegrades. The risk assessment of approximately one in one million derived from this study strengthens earlier conclusions by the Health Protection Branch (Canada) that there is no significant risk of cancer from exposure to the 2,4-TDA formed from this biodegradation.

Air and biological monitoring of toluene diisocyanate in a flexible foam plant

Comparative air measurements of toluene diisocyanate (TDI) were performed in a 5.6 m3 standard atmosphere and at a TDI flexible foam plant. Air samples were collected in midget impinger flasks containing 9-(N-methyl-amino-methyl)-anthracene (MAMA) in toluene and on 13-mm glass-fiber filters impregnated with MAMA and glycerol analyzed by LC-UV and with filter-tape instruments. In the laboratory study the average amounts of the TDI-MAMA derivatives determined were higher for filters compared to impingers when tested at concentrations between 16 and 150 micrograms/m3 (n = 29). At the TDI foaming plant the amount of TDI-MAMA collected on the filters compared with impingers showed higher TDI values at low concentrations and lower values at higher concentrations. The same was seen for the filter-tape measurements, but for two samples at very low concentrations the response was much lower. The average air concentration was 29.8 micrograms/m3 (12.5-79.9; n = 12). The highest exposure peak measured was approximately 3 mg TDI/m3. 2,4- and 2,6-toluene diamine (TDA) in urine (U-TDA) and in plasma (P-TDA) from four exposed workers and one volunteer were determined after strong acid hydrolysis as their pentafluoro-propionic anhydride derivatives using gas chromatography-mass spectrometry. The ions monitored were the M-20 ions (M = molecular weight) of the TDA and trideuterium labeled TDA as the internal standard. The P-TDA among the workers varied between 1-38 micrograms/L and between 7-24 micrograms/L for 2,4- and 2,6-TDA, respectively. The individual plasma levels among the workers over the 3-day periods varied between 7-73%. For the volunteer, P-TDA reached a maximum about 24 hours after the last exposure. The half-time of P-TDA for the volunteer was about 10 days. The urine levels (U-TDA) varied greatly with time and exposure. High peaks were found during or shortly after the exposure. No clear correlation between air levels of TDI measured with the filter-tape instruments and levels of TDA in hydrolyzed urine and plasma was seen, but the U-TDAMax followed the exposure in time as measured with the filter-tape instruments.

Biomarkers in hydrolysed urine, plasma and erythrocytes among workers exposed to thermal degradation products from toluene diisocyanate foam

Blood and urine samples were collected from six workers and two volunteers exposed to thermal degradation products from toluene diisocyanate (TDI)-based polyurethane (PUR) before and during the summer vacation. Air samples were collected on filters impregnated with 9-(N-methylaminomethyl)anthracene. The concentrations of the amines corresponding to 2,4- and 2,6-TDI, i.e., 2,4- and 2,6-toluenediamine (TDA), were determined in urine (U-TDA), plasma (P-TDA) and erythrocytes (E-TDA) after acid hydrolysis as pentafluoropropionic anhydride derivatives by GC-MS. Among the workers urinary elimination phases were seen. The estimated medians of the urinary half-lives were for the slow phase 18 d for 2,4-TDA and 19 d for 2,6-TDA. P-2,4-TDA ranged between 2.5 and 19 ng ml-1 and P-2,6-TDA between 4.4 and 30 ng ml-1. The estimated median of the half-lives in plasma were 7.8 d for 2,4-TDA and 9.6 d for 2,6-TDA. E-2,4-TDA ranged between 0.5 and 6.6 ng g-1 and E-2,6-TDA between 1.2 and 14 ng g-1. A significant linear relationship was found between the mean P-TDA and the mean E-TDA. Linear relationships were observed between the mean daily U-TDA and P-TDA and E-TDA. Virtually linear relationships were obtained for P-TDA and E-TDA and the TDI air levels. Proteins from lysed erythrocytes were separated and fractionated by gel filtration. 'TDI'-modified proteins were found in six out of a total of 80 fractions (fractions 51-56). These co-eluted completely with the haemoglobin (UV, 415 nm). Fractions 51-56 contained 89% of the applied amounts of 2,4-TDA and 81% of 2,6-TDA.

Toxicokinetics of 2,4- and 2,6-toluenediamine in hydrolysed urine and plasma after occupational exposure to 2,4- and 2,6- toluene diisocyanate

OBJECTIVES

To assess the toxicokinetics of 2,4- and 2,6- toluenediisocyanate (TDI) in chronically exposed subjects.

METHODS

Blood and urine, from 11 workers at two flexible foam polyurethane production plants, were sampled. By gas chromatography-mass spectrometry (GC-MS) 2,4- and 2,6-toluene diamine (TDA) were measured as pentafluoropropionic anhydride (PFPA) derivatives after acidic hydrolysis of plasma (P-TDA, ng/ml) and urine (U-TDA, microgram/h).

RESULTS

In one of the plants the P-2,4-TDA concentrations were 0.4-1 ng/ml before a four to five week holiday and 0.2-0.5 ng/ml afterwards. The corresponding values for P-2,6-TDA were 2-6 and 0.5-2 ng/ml respectively. In the other plant the P-2,4-TDA concentrations were 2-23 ng/ml before the holiday and 0.5-6 ng/ml afterwards and the P-2,6-TDA concentrations were 7-24 ng/ml before and 3-6 ng/ml afterwards. The P-2,4-TDA concentrations were 2-24 ng/ml before a 12 day holiday, and 1-14 ng/ml afterwards. The corresponding values for P-2,6-TDA were 12-29 and 8-17 ng/ml, respectively. The urinary elimination rates (U-TDA, microgram/h) for 2,4-TDA before the holiday were 0.04-0.54 and 0.02-0.18 microgram/h afterwards. The corresponding values for 2,6-TDA were 0.18-0.76 microgram/h before and 0.09-0.27 microgram/h after the holiday. The half life in urine ranged between 5.8 and 11 days for 2,4- and 2,6-TDA. The differences in exposure were reflected by the P-TDA concentrations. The mean half life in plasma was 21 (range 14-34) days for 2,4-TDA and 21 (16-26) days for 2,6-TDA. The TDI air concentrations varied between 0.4 and 4 micrograms/m3 in one plant and in the other between 10 and 120 micrograms/m3.

CONCLUSIONS

The half life in plasma of chronically exposed workers for 2,4-and 2,6-TDA was twice as long as for volunteers with short term exposure. An indication of a two phase elimination pattern in urine was found. The first phase was related to the more recent exposure and the second, much slower one was probably related to release of TDA in urine from TDI adducts in the body.

Rhabdomyolysis in paraphenylenediamine intoxication

Edema of the upper airways and rhabdomyolysis developed in a young patient as a consequence of paraphenylenediamine poisoning. Treatment with adrenaline, steroids and enforced diuresis prevented tracheostomy and renal failure.

Exposure to toluenediamines from polyurethane-covered breast implants

Toluenediamines (TDA) were monitored in blood, urine and redon drainage following implantation of polyurethane (PU)-covered breast prostheses. In the redon drainage TDAs showed an initial steep drop. The levels did not fall below detection limits but formed a plateau, which suggests a continued degradation of the PU foam. Urinary metabolite levels were above pre-operation background in all samples collected. In plasma there is an initial lag period of 20-30 days, where little above background TDA was found, after which levels rose to above 4.0 and 1.5 ng/ml plasma for 2,4-toluenediamine (24TDA) and 2,6-toluenediamine (26TDA), respectively. Elevated levels were found up to 2 years post-operation. Acid hydrolysis of precipitated plasma proteins released equivalent amounts of TDA as from total plasma, TDA being covalently bound to both albumin and globulin fractions. Urinary and plasma levels from these patients are in the same range detected from occupational exposure to toluene diisocyanate.

Determination of toluenediamine isomers by capillary gas chromatography and chemical ionization mass spectrometry with special reference to the biological monitoring of 2,4- and 2,6-toluene diisocyanate

The determination of 2,3-, 3,4-, 2,6-, 2,4- and 2,5-toluenediamine (TDA) in hydrolysed human urine and blood plasma was studied by GC-MS. The TDA isomers as their perfluoro-fatty acid anhydride derivatives were investigated. Chemical ionization with ammonia and isobutane as reagent gas and monitoring both positive and negative ions are studied. Negative ion monitoring using ammonia and the TDA pentafluoropropionic anhydride (PFPA) derivatives were chosen owing to the low detection limits and good separations of the isomers studied. The ions monitored were m/z 394 and 374 corresponding to the (M-20)- and (M-40)- ions and the m/z = 397 and 377 ions of the tri-deuterium-labelled TDA used as an internal standard. The performance of 2,4-, 2,5- and 2,6-TDA-PFPA in the ion source was studied by varying the ammonia pressure, temperature and electron energy. A 1-ml volume of human urine was added to 1.5 ml of 6 M HCl containing 0.5 micrograms/l of each of the trideuterated 2,6- and 2,4-TDA and the solution was hydrolysed at 100 degrees C overnight. TDA was extracted into 2 ml of toluene by the addition of 5 ml of saturated NaOH solution. Derivatization was performed in toluene by the addition of 10 microliters of PFPA. The excesses of the reagent and acid formed were removed by extraction with 1 M phosphate buffer solution (pH 7.5). Analyses of 2,6-, 2,4- and 2,5-TDA-spiked human urine (0.2-2.5 micrograms/l) were performed. The correlation coefficients were 0.999 (n = 6). The precision (R.S.D.) for human urine spiked at 1 micrograms/l was 1.6% for 2.6-TDA, 3,5% for 2,4-TDA and 3.2% for 2,5-TDA (n = 10). The detection limit, defined as twice the signal-to-noise ratio, was 1-5 fg injected, corresponding to less than 0.05 micrograms/l of TDA in human urine or plasma.

Systemic paraphenylenediamine (PPD) poisoning: a case report and review

A case of suicidal poisoning with paraphenylenediamine (PPD) is reported. The patient presented with typical features of severe oropharyngeal oedema and rhabdomyolysis. He suffered sudden cardiac death within 4 hours of admission despite full supportive treatment. The diagnosis was only established after his death. Systemic poisoning with paraphenylenediamine (PPD) is rare in western countries, and therefore a high degree of awareness and circumstantial evidence is required to make an early diagnosis. The classical and other less commonly reported features of this poisoning are discussed. There is no specific antidote available but some guidelines for management of such a case are reviewed.

Biological monitoring of occupational exposure to toluene diisocyanate

The study validated the use of urinary toluene diamine (TDA) in postshift samples as an indicator of preceding 8-h exposure to toluene diisocyanate (TDI). Nine workers exposed in TDI-based polyurethane foam production were studied. Their exposure levels varied in 8-h time-averaged samples from 9.5 to 94 micrograms/m3. The urinary TDA concentrations varied from 6.5 to 31.7 micrograms/g creatinine and they were linearly related to the atmospheric TDI levels. Approximately 20% of TDI is metabolized to diamines but their specificity is remarkable to the extent that by analysis for the 2,4- and 2,6-diamino isomers an idea of the percutaneous absorption may be had.

Gas chromatographic/tandem mass spectrometric identification and quantitation of metabolic 4-acetyltoluene-2,4-diamine from the F344 rat

2,4-Toluenediamine (TDA) and 2,4-toluenediisocyanate (TDI) are metabolized in the Fischer 344 rat to monoacetyl-2,4-toluenediamine (Ac-TDA) and diacetyl-2,4-toluenediamine (Ac2-TDA). A gas chromatographic/tandem mass spectrometric (GC/MS/MS) method was developed to characterize the structure of the Ac-TDA metabolite (2-acetyl versus 4-acetyl), as a D3-diacetyl-TDA derivative. This method was also shown to be useful in the measurement of urinary levels of TDA, Ac-TDA and Ac2-TDA. Urine samples (1.0 g) were adjusted to pH 6.5-7.0, fortified with the internal standard D9-Ac2-TDA (D3-ring + D3-acetyl x 2) and extracted with ethyl acetate (2 x 2 ml). The extract residues were then derivatized with D6-acetic anhydride and analyzed via electron impact GC/MS/MS. MS/MS analysis of the D3-Ac2-TDA derivative of the two Ac-TDA isomers yielded different daughter ion spectra from the common parent ion (m/z 209). Analysis of urine samples from rats administered TDA (p.o., i.v.) and TDI (p.o., inhalation) indicated that all of the metabolic Ac-TDA from these test materials was the 4-acetyl-TDA isomer. Subsequent GC/MS analysis of the heptafluorobutyric acid (HFBA) derivative of this metabolite confirmed the MS/MS results. Selected ion monitoring of the M-acetyl daughter ions from the derivatized TDA, Ac-TDA and Ac2-TDA was shown to be a useful technique for quantitation of urinary levels of these compounds, with a detection limit of 35 ng g-1 urine for TDA and 10 ng g-1 urine for Ac-TDA and Ac2-TDA.

Rapid high-performance liquid chromatographic determination of urinary N-(1-methylethyl)-N'-phenyl-1,4-benzenediamine in workers exposed to aromatic amines

A procedure has been developed for determining N-(1-methylethyl)-N'-phenyl-1,4-benzenediamine in urine by using high-performance liquid chromatography. The method uses chloroform extraction for partial clean-up of the urine sample. The separation is carried out on a reversed-phase column using 65 mmol/l aqueous ammonium acetate in acetonitrile (30:70, v/v) as the mobile phase. The column effluent is monitored at 290 nm with an ultraviolet detector. The analyte is separated from other normal urine constituents in less than 4 min. Peak height and concentration are linearly related. Coefficients of variation assessed for within-day reproducibility were 5.9 and 3.7% at concentrations of 22.3 and 92.1 micrograms/l, respectively. The mean analytical recovery from urine samples spiked with known amounts of amine was 89.7 +/- 6.8%. The request of only a small volume of urine and the simple pre-treatment procedure makes it suitable for the routine monitoring of the exposure of rubber vulcanization workers to aromatic amines.

Urinary excretion of free toluenediamines in a patient with polyurethane-covered breast implants

We report the detection of free 2,4-toluenediamine in urine of a patient implanted with polyurethane-covered breast implants. Samples were collected on several dates, ranging from 21 days to seven months after the insertion of the implants, and these samples all showed the presence of free 2,4-toluenediamine at a concentration of about 1 micrograms/L. The chemical was not found in a urine sample collected before implantation. This finding is important for risk assessment of cancer in patients with this type of breast implant because the chemical is a suspected carcinogen. Free 2,6-toluenediamine, an isomer, was also found in all samples from this patient.

Percutaneous absorption, biotransformation, retention and excretion of 1,3-diaminobenzene in the rat

Groups of seven male Wistar rats were dermally exposed for 24 hr to 556 mumol [14C]meta-phenylenediamine (MPD; 1,3-diaminobenzene) in either aqueous solution (Group 2) or 4% hydrogen peroxide (Group 3). The percutaneous absorption and the amount of non-excreted radioactivity were significantly higher in Group 2 rats. Radioactivity associated with DNA purified from the liver and kidneys was demonstrated. Urine was the principal route of excretion, especially in Group 2 rats. Rats in Group 3 excreted significantly more MPD in the faeces than did Group 2 rats. Urinary excretion of material that constituted two of the peaks in the high-performance liquid chromatogram demonstrated first-order elimination kinetics. Three N-acetylated metabolites (N-acetyl-1,3-diaminobenzene, N,N'-diacetyl-2,4-diaminophenol and N,N'-diacetyl-1,3-diaminobenzene) accounted for 49 and 37% of the urinary excretion of group 2 and 3 rats, respectively, indicating that such metabolites represent important pathways in the metabolism of MPD. Minor excretion of at least one highly hydrophilic, unidentified metabolite of MPD was demonstrated. High-performance liquid chromatographic analysis of urine indicated that the XAD-2 purification procedure, which is usually used before mutagenicity testing in vitro, resulted in some of the radioactive materials being discarded. The percutaneous absorption of MPD in vivo was compared with the permeability of isolated epidermal membranes in vitro. These studies showed that such in vitro studies might be used to predict the dermal absorption by rats, in vivo, of MPD and similar, topically applied compounds.

Excretion kinetics of the rubber anti-oxidant N-isopropyl-N'-phenyl-p-phenylendiamine (IPPD)

Sixteen rubber vulcanizers using IPPD as anti-oxidant were monitored for the presence of the parent compound in the urine during two consecutive working weeks using HPLC for analysis. At least two components in the excretion kinetics could be demonstrated: a fast one, as end-shift urinary concentrations significantly exceeded before-shift ones, and a less rapid one, as before-shift values at the end of the week significantly differed from those determined at the beginning. A skin absorption experiment was also performed. It demonstrated three components in the excretion kinetics, with apparent half-times of approximately 3, 7 and 24 h. Excretion ceased 7 d after skin exposure.

Determination of occupational exposure to toluene diisocyanate by biological monitoring

Exposure of workers to toluene diisocyanate monomer in a factory producing flexible polyurethane was measured using impinger and reagent-impregnated filter sampling. These techniques yielded highly concordant results so that the facile filter techniques can be recommended. The personal exposures were compared with the individual excretion of amine metabolites from the parent toluene diisocyanates. The excretion was linearly related to the product of sampling time and concentration. The biological half-lives of the amines proved to be short so that urine should be sampled 2 h after the exposure. The percutaneous absorption of the monomers could also be controlled.

Effect of microsomal enzyme inducers on the urinary excretion pattern of mutagenic metabolites of the carcinogen 2,4-toluenediamine

2,4-Toluenediamine [(TDA) CAS: 95-80-7] was administered to rats pretreated with the microsomal enzyme inducers phenobarbital (PB), beta-naphthoflavone (beta NF), or 3-methylcholanthrene (MCA). The 24-hour urines of male F344 rats were examined for their mutagenic potency by means of the Salmonella assay, with the Aroclor 1254-pretreated rat liver S-9 fraction as an activating system. No revertants were found with TDA or its urinary metabolites in the absence of the S-9 fraction. In the presence of S-9, the number of revertants increased as the concentration of TDA or its urinary metabolites increased. The urinary metabolites, generated after the microsomal enzyme inducers (PB, beta NF, MCA), had increased mutagenic activity as compared with the controls (saline, corn oil). In the presence of beta-glucuronidase (beta G), increased numbers of TA98 revertants were noted in the urine of rats pretreated with PB, saline, or corn oil. Addition of sulfatase did not alter the number of TA98 revertants. Conversely, beta G treatment of urine from rats pretreated with MCA or beta NF led to a decrease in the number of TA98 revertants as compared to levels in urine without beta G. Addition of known urinary metabolites of TDA, such as 4-acetylamino-2-aminobenzoic acid or 2,4-diacetylaminobenzoic acid, to beta NF-pretreated rat urine had no inhibitory effect on the mutagenicity in the absence of beta G. However, in the presence of beta G, the inhibitory effect was similar to that noted with beta NF-pretreated rat urine. Upon separation of urinary metabolites (beta NF-pretreated rat urine) into free, conjugated, and water-soluble forms, the maximum number of TA98 revertants was associated with the free ethyl acetate-extractable fraction, which accounted for the total mutagenic activity associated with the original volume of urine. Conjugated metabolites showed much less mutagenic activity, and an inhibitory principle was associated with the water-soluble fraction.

Mutagens in rat urine after dermal application of 1,3-diaminobenzene

The mutagenicity of urine from rats treated topically on the skin with 1,3-diaminobenzene was studied by the Salmonella/mammalian-microsome assay. Urine samples were either passed directly through micropore filters or extracts were prepared using XAD-2 resin before testing in the frameshift strain TA98. Significant mutagenic activity was found only after metabolic activation with rat-liver microsomes. The activity was higher in extracts from rats treated with a mixture of hydrogen peroxide and 1,3-diaminobenzene than from rats which were exposed to 1,3-diaminobenzene only. After fractionation of the urine by HPLC it could be demonstrated that the mutagenic activity was not due to the parent amine but related to metabolites in two of the fractions. To a lesser extent these two partially purified fractions were also mutagenic without S9 activation even though it was not possible to demonstrate this effect in unfractionated urine extracts. A third fraction containing two metabolites did not exert demonstrable mutagenic activity. The implications for the assessment of hazard to man are discussed.

Distribution, excretion, and metabolism of nitro-p-phenylenediamine in rats

The distribution, excretion, and metabolism of nitro-p-phenylenediamine, a constituent of hair dye, was studied after administration of [14C]nitro-p-phenylene-diamine (2.6 mg/30 microCi/kg) to male rats. After intraperitoneal administration, 37.4% of the radioactivity administered was excreted in the urine and 54.3% in the feces within 24 h. After intravenous administration, 42.2% of the radioactivity was excreted in the bile within 24 h. The highest concentration of radioactivity in tissues was found at 1 h, except in the small and large intestines, followed by a rapid decrease in concentration. Only small amounts of radioactivity were found in the tissues 48 h after administration. Some of the radioactive materials in the urine were separated by thin-layer chromatography and identified as N1,N4-diacetyl-2-amino-p-phenylenediamine, N4-acetyl-2-nitro-p-phenylenediamine, and unchanged nitro-p-phenylenediamine.

Mutagenicity of urine from rats after administration of 2,4-diaminoanisole: the effect of microsomal enzyme inducers

Ring 14C-labelled 2,4-diaminoanisole disulfate was administered to rats pretreated with the microsomal inducers phenobarbital (PB), beta-naphthoflavone (BNF), 3-methylcholanthrene (MC) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The 24-h urine from rats pretreated with PB showed a 2-fold increase in revertant rate over the corresponding control as measured by the Ames Salmonella test system. Pretreatment of rats with BNF, MC or TCDD decreased the mutagenicity of urine by about 70% when an activating system was used. However, in the absence of an activating system, the urine from rats induced with BNF, MC or TCDD showed a significant (P < 0.001) degree of mutagenicity compared with urine from controls or urine from phenobarbital-induced rats. Release of conjugates by beta-glucuronidase increased the mutagenicity of urine even in the absence of an activating system, but the number of revertants was almost doubled in the presence of an activating system. The urine from rats treated only with the 4 inducers did not show any mutagenicity. 2,4-Diaminoanisole itself was mutagenic only in the presence of an activating system. alpha-Naphthoflavone (ANF) (0.1 mM) inhibited by 85--90% the in vitro mutagenicity of urine, mediated by Aroclor 1254, MC or TCDD induced rat-liver microsomes. The mutagenicity mediated through PB-induced rat-liver microsomes was, however, inhibited only by 16%. Similarly, 0.1 mM metyrapone (MP) inhibited the mutagenicity of urine by Aroclor 1254, MC or TCDD induced rat-liver microsomes by 13--18%. For the same MP concentration a 50% inhibition of the mutagenicity mediated through PB-induced rat-liver microsomes was observed. The mutagenicity pattern for urine in vitro was shown to be similar with liver S9 from rats induced either with Aroclor 1254 or with MC.

Tissue distribution and excretion of 2,4-[14C]toluenediamine in the mouse

The tissue distribution and excretion of 2,4-[14C]toluenediamine was studied in male mice given a single ip dose (1 microCi, 0.667 mg/kg). By 24 h 52% of the administered radioactivity had been excreted in the urine and 22% in the feces. The organs with the highest concentrations of radioactivity were the liver and kidneys. High concentrations of radioactivity were also observed in the gastrointestinal tract. Elimination of radioactivity from the liver, kidneys, and blood was biphasic, with half-lives of 11.7, 9.1, and 12.6 h, respectively, for the slow phases. The dominant route of excretion was via the kidneys; during the first hour after dosing, nearly 50% of the administered radioactivity was recovered in the urine. However, only an additional 2-4% of the dose appeared in the urine during the remaining 23 h of the experiment. By 24 h, only 1.25% of the administered radioactivity has been trapped from the air expired by the animals.

Comparison of the metabolism of 2,4-toluenediamine in rats and mice

The excretion, distribution, and metabolism of 2,4-toluenediamine (TDA) have been compared in rats and mice. The elimination of TDA metabolites into urine was faster and more complete in mice than in rats. However, the feces of rats accounted for a greater percentage of the dose in rats than in mice. The distribution of metabolites in tissues were considerably lower in mice than in rats. The major urinary metabolites observed in the rat were 4-acetylamino-2-aminotoluene, 2,4-diacetylaminotoluene, 4-acetylamino-2-aminobenzoic acid. The major metabolites in the mice were 4-acetylamino-2-aminobenzoic acid, 4-acetylamino-2-aminotoluene and 2,4-diacetylaminobenzoic acid.

High-performance liquid chromatography of 2,6- and 2,4-diaminotoluene, and its application to the determination of 2,4-diaminotoluene in urine and plasma

2,4-Diaminotoluene is used for the production of industrial dyes, and along with the 2,6-isomer, as an intermediate in the production of polyurethane foams. 2,6- and 2,4-diaminotoluene were resolved as sharp peaks by normal-phase high-performance liquid chromatography in 3 min by an acetonitrile-water-saturated chloroform elution solvent (8:2, v/v) with detection by ultraviolet absorbance at 250 nm. The relationship between peak height and amount injected was linear over a range of 0.025-2 microgram for both compounds. Retention times and peak heights were highly reproducible. Detection was very sensitive, allowing quantitation of 1-2 ng of either compound. Quantitative recovery of 2,4-diaminotoluene from spiked urine and plasma samples was obtained by extraction with methylene chloride.