The Epping jaundice

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Industrial, Biocide, and Cosmetic Chemical Inducers of Cholestasis

A frequent side effect of many drugs includes the occurrence of cholestatic liver toxicity. Over the past couple of decades, drug-induced cholestasis has gained considerable attention, resulting in a plethora of data regarding its prevalence and mechanistic basis. Likewise, several food additives and dietary supplements have been reported to cause cholestatic liver insults in the past few years. The induction of cholestatic hepatotoxicity by other types of chemicals, in particular synthetic compounds, such as industrial chemicals, biocides, and cosmetic ingredients, has been much less documented. Such information can be found in occasional clinical case reports of accidental intake or suicide attempts as well as in basic and translational study reports on mechanisms or testing of new therapeutics in cholestatic animal models. This paper focuses on such nonpharmaceutical and nondietary synthetic chemical inducers of cholestatic liver injury, in particular alpha-naphthylisocyanate, 3,5-diethoxycarbonyl-1,4-dihydrocollidine, methylenedianiline, paraquat, tartrazine, triclosan, 2-octynoic acid, and 2-nonynoic acid. Most of these cholestatic compounds act by similar mechanisms. This could open perspectives for the prediction of cholestatic potential of chemicals.

Risk evaluation of occupational exposure to methylene dianiline and toluene diamine in polyurethane foam

Methylene diphenylisocyanate (MDI) and toluene diisocyanate (TDI) are widely used in industry to produce polyurethane foam products. Small amounts of methylenedianiline (MDA) and toluene diamine (TDA) are released during MDI and TDI polymerization and may be present in newly finished polyurethane foam parts. MDA and TDA concentrations in foam decline exponentially within several hours of demolding. MDA and the 2,4-isomer of TDA are known animal carcinogens and, in addition, have significant non-carcinogenic health effects. Our goal was to determine whether worker exposure to MDA or TDA in freshly produced polyurethane foams was associated with unacceptable health risks. Sampling and analysis of the fresh foam indicated that MDA and TDA concentrations varied considerably among products, but concentrations in all materials evaluated declined rapidly over time. We found that, under a worst-case exposure scenario, cancer risks from TDA exposure were approximately 5-10 6, whereas cancer risks from MDA exposure resulted in a tumorigenic margin of exposure (MOE) of 85 000. Non-cancer chronic hazard indices were well below 1.0. Therefore, the potential cancer and non-cancer health risks from MDA or TDA exposure to newly manufactured foam parts appear to fall well within acceptable health risk criteria.

Formation and elution of toxic compounds from γ-ray-sterilized medical products and the Ames test of eluted components

No formation of N,N'-methylene dianiline (MDA) was observed in chain-extended thermoplastic polyurethane (PU) when sterilized by autoclaving or γ-ray irradiation. No formation of MDA was observed in nonchain-extended thermoplastic PU when sterilized by γ-ray irradiation. Less than 1 ppm of MDA was produced in nonchain-extended thermoplastic PU subjected to autoclave sterilization. Autoclave sterilization did not produce MDA in thermosetting PU potting material. MDA formation in potting material was promoted by γ-ray irradiation and increased with increasing irradiation doses at a quadratic equation of regression. MDA formation at 100 kGy irradiation amounted to a few ppm and less than one ppm at 25 kGy irradiation: therefore, the potential risk to human recipients was not significant. The elution of compounds other than MDA from potting material was more problematic. Solvent extracts from potting material showed mutagenicity in the absence of metabolic activity (S9Mix). MDA showed mutagenicity in the presence of metabolic activity, therefore MDA was not the major mutagenic candidate. The chemical and biological characteristics of the specific mutagens should be identified in a further study. The lack of MDA formation and a smaller presence of mutagens in autoclave-sterilized potting material indicated that autoclave sterilization was preferable if the material is able to tolerate heating.

Xenobiotic-induced liver injury and fibrosis

INTRODUCTION

Many different drugs and xenobiotics (chemical compounds foreign to an organism) can injure the bile duct epithelium and cause inflammatory bile duct diseases (cholangiopathies) ranging from transient cholestasis to vanishing bile duct syndrome, sclerosing cholangitis with development of biliary fibrosis and cirrhosis. Animal models of xenobiotic-induced liver injury have provided major mechanistic insights into the molecular mechanisms of xenobiotic-induced cholangiopathies and biliary fibrosis including primary biliary cirrhosis and primary sclerosing cholangitis.

AREAS COVERED

In this review, the authors discuss the basic principles of xenobiotic-induced liver and bile duct injury and biliary fibrosis with emphasis on animal models. A PubMed search was performed using the search terms "xenobiotic," "liver injury," "cholestasis," and "biliary fibrosis." Reference lists of retrieved articles were also searched for relevant literature.

EXPERT OPINION

Xenobiotic-induced cholangiopathies are underestimated and frequently overlooked medical conditions due to their often transient nature. However, biliary disease may progress to vanishing bile duct syndrome, biliary fibrosis, and cirrhosis. Moreover, xenobiotics may prime the liver for subsequent liver disease by other agents and may also contribute to the development of hepatobiliary cancer though interaction with resident stem cells.

4,4'-Methylenedianiline-induced hepatitis in an industrial worker: case report and review of the literature

4,4'-Methylenedianiline (MDA) is a chemical used in manufacturing and insulation processes and is a well-known hepatotoxin. We report the case of a 42-year-old construction-site worker who was accidentally exposed to large amounts of MDA and developed acute liver damage. The clinical course is described, with particular emphasis on the timely identification of the underlying cause and prompt management that led to an uneventful recovery. We review the relevant literature and discuss the safety measures necessary to minimize similar occupational hazards in industrial workers.

Liquid chromatography-electrospray tandem mass spectrometry investigations of fragmentation pathways of biliary 4,4'-methylenedianiline conjugates produced in rats

4,4'-methylenedianiline (DAPM) is the main building block for production of 4,4'-methylenediphenyldiisocyanate that has been widely used in the manufacturing of polyurethane materials including medical devices. Although it was revealed that damage to biliary epithelial cells of the liver and common bile duct occurred upon acute exposure to DAPM, the exact mechanism of DAPM toxicity is not fully understood. Both phase I and II biotransformations of DAPM, some of which generate reactive intermediates, are characterized in detail by liquid chromatography electrospray tandem mass spectrometry. The two most prominent metabolites found in rat bile (M2 and M7) implicated glutathione, glucuronic acid, and glycine conjugations (phase II) following hydroxylation, and N-oxidation (phase I). Their decomposition pathways, as evidenced by MS(n) experiments, have been elucidated in detail. [figure: see text]

Grand rounds: an outbreak of toxic hepatitis among industrial waste disposal workers

CONTEXT

Industrial waste (which is composed of various toxic chemicals), changes to the disposal process, and addition of chemicals should all be monitored and controlled carefully in the industrial waste industry to reduce the health hazard to workers.

CASE PRESENTATION

Five workers in an industrial waste plant developed acute toxic hepatitis, one of whom died after 3 months due to fulminant hepatitis. In the plant, we detected several chemicals with hepatotoxic potential, including pyridine, dimethylformamide, dimethylacetamide, and methylenedianiline. The workers had been working in the high-vapor-generating area of the plant, and the findings of pathologic examination showed typical features of acute toxic hepatitis.

DISCUSSION

Infectious hepatitis and drug-induced hepatitis were excluded by laboratory findings, as well as the clinical course of hepatitis. All cases of toxic hepatitis in this plant developed after the change of the disposal process to thermochemical reaction-type treatment using unslaked lime reacted with industrial wastes. During this chemical reaction, vapor containing several toxic materials was generated. Although we could not confirm the definitive causative chemical, we suspect that these cases of hepatitis were caused by one of the hepatotoxic agents or by a synergistic interaction among several of them.

RELEVANCE TO CLINICAL OR PROFESSIONAL PRACTICE

In the industrial waste treatment process, the danger of developing toxic hepatitis should be kept in mind, because any subtle change of the treatment process can generate various toxic materials and threaten the workers' health. A mixture of hepatotoxic chemicals can induce clinical manifestations that are quite different from those predicted by the toxic property of a single agent.

4,4′-Methylenedianiline-Induced Hepatotoxicity Is Modified by N-Acetyltransferase 2 (NAT2) Acetylator Polymorphism in the Rat

4,4'-Methylenedianiline (MDA) is widely used in the manufacturing of polyurethane foam, epoxy resins, and polymers. Exposure to MDA induces liver damage in humans and rats. MDA undergoes N-acetylation catalyzed by N-acetyltransferase 1 (NAT1) and 2 (NAT2) in the liver. Both human and rat NAT2 are polymorphic, and human NAT2 genetic polymorphism modifies the frequency and/or severity of drug and xenobiotic toxicity in human populations. Recombinant expression of rat Nats in Escherichia coli showed that MDA was acetylated by both recombinant rat Nat1 and Nat2 and was catalyzed at substantially higher rates by rapid acetylator Nat2 compared with slow acetylator Nat2. Rapid acetylator F344 rat liver cytosols catalyzed the N-acetylation of MDA at significantly higher rates than those from slow acetylator Wistar-Kyoto (WKY) inbred rats. To test the effect of NAT2 genetic polymorphism on hepatotoxicity from acute MDA exposure, we compared hepatotoxicity in rapid (F344) and slow (WKY) Nat2 acetylator inbred rats that were administered MDA. Based on the results of dose-response studies ranging up to 150 mg/kg MDA administered by intragastric gavage, the effect of a moderately hepatotoxic dose (37.5 mg/kg) was compared in rapid versus slow acetylator rats. Plasma alanine transaminase enzyme activities were approximately 5-fold higher (p < 0.05) in rapid versus slow acetylator rats after MDA treatment, and necrotizing hepatitis with portal damage consisting of bile ductular necrosis, portal expansion, and inflammation was clearly more prominent. These results suggest that acetylator phenotype is an important factor for susceptibility toward MDA hepatotoxicity.

Evaluation of Aqueous Extracts from Elast-Eon Polymers for Methylene Dianiline (MDA) by High-Performance Liquid Chromatography (HPLC)

Elast-Eon polymers are a class of materials suitable for use in long-term implantable medical devices. They are the copolymers of methylene diphenyl diisocyanate (MDI) based polyurethanes and hydroxyl-terminated polydimethyl siloxane, and as a result combine the biostability and biocompatibility of silicones with the mechanical properties of polyurethanes. In order to ensure product safety and meet regulatory requirements, it is important to confirm the absence or presence of toxic 4,4′-methylene dianiline (MDA) in aqueous extracts of Elast-Eon. The present work focusses on the development of an analytical technique to detect any leachable MDA from Elast-Eon polymers. No traces of MDA could be detected in the aqueous extracts from Elast-Eon, or from sterilized and aged (accelerated oxidized) samples of Elast-Eon.

The Epping Jaundice outbreak: mortality after 38�years of follow-up

OBJECTIVE

To investigate mortality in individuals exposed to 4,4'-methylenedianiline (MDA).

METHODS

The mortality of 84 individuals, accidentally poisoned with MDA during the "Epping Jaundice" outbreak of 1965, was compared with expected values based on national rates defined by age, period and sex, for the period 1965-2002. In addition, cancer registration data were analysed for the period 1971-2002.

RESULTS

The vital status of 83% of the group was established, with 37 deaths occurring before the end of follow-up. Mortality from all causes was close to expectation among females (Obs, 25; Exp, 30.3; SMR, 82), and below expectation among males (Obs, 12; Exp, 26.7; SMR, 45). There were no observed deaths from cancer of the liver or from nonmalignant liver disease.

CONCLUSIONS

This study has found no evidence to suggest that the ingestion of MDA had adversely affected mortality.

Drug-induced cholestasis

Drugs may cause several overlapping syndromes of cholestasis, the pathophysiological syndrome resulting from impaired bile flow. These reactions comprise approximately 17% of all hepatic adverse drug reactions (ADRs) and they may be severe. Causes of 'pure' (bland) cholestasis include oestrogens and anabolic steroids; rarer associations are with antimicrobials and NSAIDs. 'Cholestatic hepatitis' is a common drug reaction in which liver injury and inflammation cause significant elevation of serum alanine aminotransferase (ALT) as well as cholestasis. Chlorpromazine and ketoconazole are classic examples, but it is now exemplified by amoxycillin-clavulanate and other oxy-penicillins. Chronic cholestasis results from small bile duct injury leading to the vanishing bile duct syndrome (VBDS), a disorder mimicking primary biliary cirrhosis, or from injury to larger bile ducts causing secondary sclerosing cholangitis. Whilst there is increasing evidence of a genetic predisposition to cholestatic drug reactions, there are currently no pretreatment tests to predict drug safety. Prevention of severe reactions therefore relies on early detection of liver injury and prompt drug withdrawal. Symptomatic management includes relief of pruritus and correction of fat-soluble vitamin deficiency. In small cohort studies, ursodeoxycholic acid (UDCA) arrested progressive cholestasis in two-thirds of cases, but evidence for use of corticosteroids is anecdotal. This review considers diagnosis, pathogenesis, prevention and management of drug-induced cholestasis, with particular reference to frequently- and newly-described causes.

N-oxidation of aromatic amines by intracellular oxidases

The introduction includes a literature review of DNA reactive species and DNA adduct formation that results from aromatic amine N-oxidation catalyzed by hepatic cytochrome P450 vs. that catalyzed by nonhepatic peroxidases. Experimental evidence is then described for a novel oxidative stress mechanism involving prooxidant N-cation radical formation by both oxidases, which is proposed as a contributing mechanism for aromatic amine induced cytotoxicity and carcinogenesis. Aromatic amine N-cation radicals formed by peroxidases were found to cooxidize GSH or NADH and form reactive oxygen species. The latter could explain the reported DNA oxidative damage found in vivo following methylaminoazobenzene administration [Hirano et al. Analyses of Oxidative DNA Damage and Its Repair Activity in the Livers of 3'-Methyl-4-dimethylaminoazobenzene-Treated Rodents. Jpn. J. Cancer Res. 2000, 91, 681-685]. It was also found that the prooxidant activity of the aromatic amine increased as its redox potential, i.e., ease of oxidation decreased with o-anisidine and aminofluorene being the most effective at forming reactive oxygen species. This suggests that the rate-limiting step in the cooxidation is the rate of arylamine oxidation by the peroxidase. Incubation of hepatocytes with aromatic amines caused a decrease in the mitochondrial membrane potential before cytotoxicity ensued. The CYP1A2-induced hepatocytes isolated from 3-methylcholanthrene administered rats were much more susceptible to some arylamines and were protected by CYP1A2 inhibitors. Hepatocyte GSH was also depleted by all arylamines tested and extensive GSH oxidation occurred with o-anisidine and aminofluorene, which was prevented by CYP1A2 inhibitors. This suggests that in intact hepatocytes CYP1A2 may also catalyze a one-electron oxidation of some arylamines to form prooxidant cation radicals, which cooxidize GSH to form the reactive oxygen species.

Liver dysfunction among workers handling 5-nitro-o-toluidine

BACKGROUND

5-Nitro-o-toluidine is an aromatic nitro amino compound. While other aromatic compounds are known to damage the human liver and are registered as toxic substances, toxicity information concerning 5-nitro-o-toluidine is lacking.

AIMS

To investigate the hepatotoxicity of 5-nitro-o-toluidine.

PATIENTS AND METHODS

Of 15 workers in the same factory who handled 5-nitro-o-toluidine, three were hospitalised with symptoms of acute liver dysfunction. Suspecting a link between liver dysfunction and working conditions, we correlated workplace factors with clinical findings in all 15 workers.

RESULTS

Blood biochemistry tests indicated liver damage in seven of 15 study subjects. Workers who handled 5-nitro-o-toluidine and nitrosyl sulphuric acid often loosened their respiratory protective equipment shortly after 5-nitro-o-toluidine powder had been dispersed into the air of the room. No potential hepatotoxins were present except for 5-nitro-o-toluidine. Six of the affected workers had handled 5-nitro-o-toluidine 12 to 20 times; the seventh worker had handled the powder three times; and the other eight workers without liver dysfunction had handled the material once or twice. No other significant differences in background were evident between the affected and unaffected workers, such as age, sex, or protective measures. Histological findings during recovery from liver damage were similar to those of acute viral hepatitis. None of the 15 subjects has demonstrated liver damage since the factory was closed.

CONCLUSIONS

A link between liver dysfunction and 5-nitro-o-toluidine exposure is suggested by greater severity of liver dysfunction associated with more episodes of handling.

Modulation of taurine levels in the rat liver alters methylene dianiline hepatotoxicity

Methylene dianiline (DAPM) causes hepatic damage and bile duct necrosis in rats. This has been detected histologically and biochemically. The toxicity was dose related over the range 0-100 mg/kg but the dose response relationship showed a maximum at about 75-100 mg/kg. This was true for both histopathology and biochemical parameters of liver dysfunction. When animals were depleted of taurine using beta-alanine pretreatment, the toxicity of DAPM was increased. Conversely treatment of rats with taurine, significantly attenuated the rise in alanine transaminase (ALT). However depletion of taurine with guanidinoethanesulphonate (GES) attenuated rises in both transaminases. It is concluded that taurine may play a role in the toxicity of DAPM but that GES, although depleting taurine as does beta-alanine, causes additional effects such as increasing glutathione (GSH), perhaps leading to protection.

Accidental intoxication with methylene dianiline p,p'-diaminodiphenylmethane: acute liver damage after presumed ecstasy consumption

BACKGROUND

MDA is the abbreviation for methylene dianiline (p,p' diaminodiphenylmethane; 4,4'-methylenedianiline; CAS 101-77-9); and for methylendioxyamphetamine (MDMA, N, alpha-dimethyl-1,3-benzodioxole-5-ethanamine; CAS 42542-10-9). While the former is used for the production of polyurethane foams, the latter is a psychometric drug, which is becoming increasingly popular in the techno scene.

METHODS

We report six participants of a technoparty (1 female, 5 males, ages 17-25) who were admitted to the hospital with severe colicky abdominal pain and subsequently developed symptoms of hepatotoxicity. They had ingested an alcoholic beverage that had been spiked with a powdery substance they dubbed MDA.

RESULTS

All patients showed similar clinical symptoms, with an identical time course. Acute jaundice developed within 2 days after ingestion. Enzymes indicating cholestasis increased steadily over 7 days and reached peak values of 800 U/L (AP) and 380 U/L (GGT), whereas transaminases remained moderately elevated. Between days 5 and 7, all patients became febrile for one day, their body temperatures rising up to 40 degrees C. There was no evidence for hemolysis or an infectious hepatitis. Toxicological analysis revealed the presence of p,p'-diaminodiphenylmethane (4,4'-methylenedianiline) at a concentration of 130 mg/L in one of two urine extracts examined.

CONCLUSIONS

The analytical data indicate that the participants of the technoparty assumed the aniline-derivative, the cause of Epping Jaundice, was methylendioxyamphetamine because the same abbreviation, MDA, is used for both compounds. An overview of the acute liver toxicity of aniline derivatives is given and the possibility of amphetamine-induced liver damage is discussed.

Biomarkers of exposure, antibodies, and respiratory symptoms in workers heating polyurethane glue

OBJECTIVES

The pathogenic basis of respiratory disorders associated with isocyanates are still obscure. One reason for this is the lack of good estimates of human exposure. In this study exposure was estimated by measurement of isocyanate metabolites in biological samples.

METHODS

In a factory using isocyanate based polyurethane (PUR) glue, isocyanate concentrations in air were measured by liquid chromatography. Samples from 174 employees were analysed for metabolites of 4,4'-methylene diphenyl diisocyanate (MDI) in plasma (P-MDX) and urine (U-MDX). After hydrolysis, 4,4'-methylenedianiline was measured by gas chromatography-mass spectrometry (GC-MS). The employees were screened for work related respiratory symptoms and tested for specific immunoglobulin E (IgE) and IgG antibodies directed against isocyanate conjugated to human serum albumin.

RESULTS

The time weighted isocyanate concentrations in air were low (MDI < 0.2-7; hexamethylene diisocyanate (HDI) < 0.1-0.7; 2,6-toluene diisocyanate (TDI) < 0.1 microgram/m3). All subjects had detectable P-MDX and U-MDX. There were significant associations between the estimates of exposure to thermal degradation products of an MDI based glue and P-MDX (range < or = 0.10-5.5 micrograms/l); and U-MDX (< or = 0.04-5.0 micrograms/g creatinine); in cases of heavy exposure. P-MDX and U-MDX were associated with each other (r = 0.64; P = 0.0001), work related symptoms (P-MDX: P = 0.03; Mann-Whitney U test), and serum concentrations of MDI specific IgG antibodies (r = 0.26; P = 0.0007). Unexpectedly, high P-MDX and U-MDX concentrations were also encountered in workers cutting textile (P-MDX 2.4-4.5 micrograms/l; U-MDX 0.81-3.8 micrograms/g creatinine); the reason is still unknown. Equally unexpected, there were significant negative associations between P-MDX and liver function tests.

CONCLUSIONS

The results clearly show the value of biomarkers for isocyanate exposure; in particular, P-MDX is useful. Further, these results show the risk connected with thermal degradation of PUR.

Formation and elution of toxic compounds from sterilized medical products: methylenedianiline formation in polyurethane

The formation of a toxic and carcinogenic compound, methylenedianiline (MDA), in sterilized medical use polyurethane (PU) is discussed. Due to good biocompatibility and biostability, PU is widely used for blood-containing devices. There are two types of PU currently available for medical use. One is chain-extended thermoplastic PU, the other is thermosetting PU used for potting material connecting fibers and modules in artificial dialyzers and plasma separators. Both gamma-ray irradiation and autoclave sterilization are predominantly used for the sterilization of these devices. MDA formation in sterilized PUs by gamma-ray irradiation and by autoclave treatment is compared. The Delany clause in the USA prohibits the manufacture of medical devices producing any toxic compound during fabrication and sterilization, therefore, the formation and elution of MDA and other toxic compounds should be seriously considered. Although MDA formation at a concentration of a few to a few hundred ppb in autoclaved chain-extended thermoplastic PU has been reported, there have been no papers describing MDA formation in autoclaved thermosetting PU potting material, or describing MDA formation in gamma-ray irradiated chain-extended thermoplastic PU and thermosetting PU. We elected to determine whether MDA was in fact produced in Pus sterilized by gamma-ray irradiation or by autoclave sterilization. Our objective was to estimate the risk factor to the human patients or recipient. Our conclusion is to confirm which sterilization of gamma-ray or autoclave is more appropriate. No formation of MDA was observed in autoclaved thermosetting PU potting material at 121 degrees C for 60 min. A few ppm of MDA was formed in irradiated potting material. MDA formation increased with increasing irradiation doses. MDA formed in irradiated potting material at 2.5 Mrad (less than one ppm) is not a significant risk to the recipient. The estimated cancer causing risk factor when absorbing one mg MDA/kg body weight/day is 0.29. Twenty-nine persons per 100 persons exhibit a cancer potential. More importantly, our experimental evidence indicated that serum extracts from irradiated potting material contained unknown compounds other than MDA. The presence of these compounds is considerably more significant and toxic. When tested, these compounds proved to be mutagenic in the absence of metabolic activity, thus promoting a need to identify and study further. Compounds indicating mutagenicity increased with increasing irradiation. Small amounts of mutagenic compounds were determined in extract from autoclaved potting material, smaller than that by gamma-ray irradiation. Therefore, autoclave sterilization is more appropriate, providing materials can withstand the process.(ABSTRACT TRUNCATED AT 400 WORDS)

Assessment of occupational exposure to 4,4'-methylenedianiline by the analysis of urine and blood samples

Seven workers at a work site where methylenedianiline (MDA) was used as a curing agent for an epoxy resin were studied during 4 workdays and one weekend. Internal exposure was monitored by analysis of 4,4'-MDA in hydrolysed urine and blood. After acidic hydrolysis, MDA was extracted, derivatised by use of pentafluoropropionic anhydride, and determined by gas chromatography and mass spectrometry, with negative ion chemical ionization. There was wide variation of MDA concentrations in hydrolysed blood between the workers (range 10-60 nmol/l). Also, the urinary excretion rate varied considerably both between and within the individual workers (0-90 mumol/h). The urinary excretion displayed some variation in relation to exposed periods. The urinary levels were linearly related to the concentrations in blood (rs = 0.93, P = 0.02). The present results show the value of excretion of MDA in hydrolysed urine and concentrations in blood as means for the biological monitoring of MDA exposure. In this case, the exposure was probably mainly dermal, in spite of extensive protection measures.

Biomonitoring of 4,4'-methylene dianiline by measurement in hydrolysed urine and plasma after epicutaneous exposure in humans

Five healthy volunteers were dermally exposed for 1 h to 0.75-2.25 mumol 4,4'-methylene dianiline (MDA) dissolved in isopropanol, by use of a patch-test technique. Determination of MDA remaining in the patch units after exposure showed that a median of 28% (range 25-29%) was absorbed. By analysis of hydrolysed plasma, an initial accumulation of MDA could be shown, and then a decline. MDA was also detected in hydrolysed urine. The maximum rate of MDA excretion in urine was found 6-11 h after the onset of exposure. Within two subjects studied at three doses, the urinary excretion was proportional to the exposure. The elimination half-lives (elim-t1/2) in plasma and urine had medians of 13 and 7 h, respectively. In eight out of nine exposures, the elim-t1/2 was longer in plasma than in urine. Slow acetylation seemed to be associated with short elim-t1/2 in urine. The median of total MDA amount excreted in urine during 48 h, was 33 nmol for the five subjects exposed to 0.75 mumol, which corresponded to roughly 16% (range 2%-26%) of the absorbed dose while only a limited number of individuals were studied, the data still indicated that MDA in hydrolysed plasma or urine can be used for biological monitoring of occupational dermal exposure. However, the individual variation must be taken into account. Sampling should preferably be made several hours post shift. Urine is preferred before plasma at low exposures, because of its higher concentrations of MDA.

Follow-up of a group of workers intoxicated with 4,4'-methylenedianiline

4,4'-Methylenedianiline (MDA), an aromatic amine, is a known human hepatotoxin and an animal carcinogen but there is little information regarding its chronic effects in humans. Between 1967 and 1976, 10 workers at a plant in Ontario that used MDA as an epoxy hardener developed acute jaundice. We followed this group from the date of intoxication through to the end of 1991 for cancer incidence by matching with the Ontario Cancer Registry. To date, one cancer, a pathologically confirmed bladder cancer has developed (expected number based on provincial incidence rates: 0.64 for all cancers, 0.05 for bladder cancer). This finding may be important because bladder cancer was a site of interest a priori; bladder cancers have been observed in two other occupationally exposed groups (significantly higher than expected in one of these); in the National Toxicology Program bioassay, urinary bladder tumors occurred in exposed animals but not in controls; and MDA has structural similarity to known human bladder carcinogens such as benzidine.

Characterization of acute 4,4'-methylene dianiline hepatotoxicity in the rat

Methylene dianiline (DDM) is a chemical intermediate in the production of isocyanates and other industrial chemicals, and it is hepatotoxic in humans. The acute hepatotoxicity of orally administered DDM was characterized in rats. Rats receiving DDM (25-225 mg/kg, per os) demonstrated a dose-dependent elevation in serum alanine aminotransferase activity, g-glutamyltransferase activity, and serum bilirubin concentration. DDM also caused a decrease in bile flow and an elevation in liver weight. Significant changes in these markers of liver injury occurred between 8 and 12 hr after a single, oral administration of DDM. Histologically, DDM caused multifocal, necrotizing hepatitis with neutrophil infiltration. Changes in the portal regions consisted of bile ductular necrosis, portal edema, neutrophil infiltration, mild fibrin exudation, and segmental necrotizing vasculitis. The role of cytochrome P450 monooxygenase (MO)-mediated metabolism in DDM hepatotoxicity was evaluated using the MO inhibitors, aminobenzotriazole and SKF-525A and the MO inducers phenobarbital and beta-naphthoflavone. Aminobenzotriazole provided protection from DDM-induced hepatotoxicity, whereas SKF-525A had no effect. The effect of phenobarbital pretreatment depended on the dose of DDM administered. At a dose of DDM that produced a maximal hepatotoxic response, phenobarbital did not influence hepatotoxicity. However, phenobarbital pretreatment provided protection against the hepatotoxic effects of a lower dose of DDM. beta-naphthoflavone pretreatment had a more modest effect on DDM-induced hepatic insult. These results demonstrate that DDM causes acute hepatotoxicity in the rat that is dose and time dependent. Results using inducers and inhibitors of MO suggest that DDM requires bioactivation to exert toxicity; however, the relationship between metabolism and toxicity may be complex.

Chemical disasters

Chemical disasters are sufficiently common that plans are needed to prevent them, or to mitigate their effects should they occur. However, they are sufficiently rare that any individual is likely to have little or no experience of them. This article reviews chemical disasters which have been reported in the medical literature, and briefly discusses plans for medical involvement in the prevention and tackling of such events.

Identification of metabolites of 4,4'-diaminodiphenylmethane (methylene dianiline) using liquid chromatographic and mass spectrometric techniques

The in vitro metabolism of 4,4'-diaminodiphenylmethane (methylene dianiline, MDA) was investigated using rabbit liver microsomes. Minimal clean-up of the microsomal incubations was carried out using zinc sulphate precipitation followed by solid-phase extraction on Sep-Pak C18 cartridges. Three metabolites were detected in hepatic microsomal incubations, namely the azodiphenylmethane (azo) azoxydiphenylmethane (azoxy) and 4-nitroso-4'-aminodiphenylmethane (nitroso) compounds. The azo and azoxy metabolites were produced enzymatically whereas the nitroso compound may have been formed via a non-enzymatic process. Reversed-phase high-performance liquid chromatography-plasma spray mass spectrometry was used to initially detect these metabolites. Fast atom bombardment mass spectrometry and fast atom bombardment tandem mass spectrometry were utilized to further structurally characterise these compounds. Comparison of mass spectral data obtained from synthesised standards with data obtained on the putative metabolites substantiated the characterisation of these compounds.

The Epping jaundice outbreak: a 24 year follow up

STUDY OBJECTIVE

The aim was to trace 84 cases of jaundice that occurred following accidental ingestion of methylene dianiline (MDA) in Epping in 1965, and to look at long term health effects.

DESIGN

The original case notes of the cases were used to identify the patients. Subsequent tracing procedures included local general practitioners, the Central NHS Registry, electoral rolls, and company records.

SETTING

This was a community based survey.

MAIN RESULTS

The health status of 68 (81%) of the group was established with 18 deaths. Of the 50 cases known to be alive, 58% completed a health questionnaire. The causes of death were unremarkable except for one case of carcinoma of the biliary tract. Two surviving cases had suffered retinal pathology. Four other surviving cases had had a further, perhaps unrelated, episode of jaundice.

CONCLUSIONS

Although the dose and route of administration in the epidemic differed from occupational exposure, this follow up study a generation on provides little, if any, evidence of long term health sequelae. Nevertheless, in the absence of well documented exposure and health effects data, such accidental poisonings with proven animal carcinogens warrant long term follow up. The identified cohort will be the subject of further study.

Methylene dianiline: assessment of exposure and cancer morbidity in power generator workers

The biaromatic amine 4,4'-methylene dianiline (MDA) is an animal carcinogen, possibly also carcinogenic to humans. In a cohort of 595 power generator workers potentially exposed to MDA in a curing agent of an epoxy system, the overall standardised cancer incidence ratio (SIR) among males (n = 550), however, was only 0.52 [95% confidence interval (CI) 0.16-1.21] based on five observed cases. One male urinary bladder cancer case was found in comparison to 0.6 expected (SIR 1.67; 95% CI 0.04-9.31). This case was identified in an unexposed subcohort. High levels of MDA metabolites were ascertained in the urine of currently exposed workers, probably following percutaneous absorption. Although no evidence of an increased overall or bladder cancer risk was detected, the limitations of the study in regard to the size of the cohort, age and cancer latency preclude a definite risk assessment. The dermal absorption of MDA has been highlighted.

Fatal fulminant hepatic failure in a 'solvent abuser'

The case of a 17 year old abuser of butane aerosols who developed fulminant hepatic failure after taking a proprietary engine or carburetor cleaner is described. Fatalities as a result of liver failure due to volatile hydrocarbons or solvents have not previously been reported. The likely toxins included isopropyl alcohol, methyl amyl alcohol, butylated hydroxytoluene as well as petroleum products, and evidence for their toxicity is reviewed. The possibility of increased susceptibility to hepatotoxins after enzyme induction by abuse of volatile agents is discussed. Hepatic dysfunction should be sought in patients who abuse solvents or volatile hydrocarbons and supportive measures instituted promptly when required.

Toxicity of 1,4-bis(aminocyclohexyl)methane

1,4-Bis(aminocyclohexyl)methane (PACM; CAS No. 1761-71-3) is a white solid considered for use in polymeric systems. PACM is moderately toxic systemically, with the acute oral lethal dose in rats between 670 and 1000 mg kg-1. PACM is a weak dermal sensitizer in the guinea pig. Instillation of as little as 10 mg of PACM to the rabbit eye produces severe injury. This damage could be permanent and was not reduced by rinsing the eye with water. Dogs given oral doses of 50 mg PACM kg-1 5 days per week for up to 18 months showed kidney and liver damage, along with local irritation of the gastrointestinal tract. The chemical is highly irritating and contact with it should be avoided.

High-performance liquid chromatographic determination of 4,4'-methylenedianiline in human urine

A method is described for the determination of urinary 4,4'-methylenedianiline (MDA) by high-performance liquid chromatography (HPLC). MDA was extracted from hydrolyzed urine using C18 solid-phase extraction columns. The extract was analyzed by reversed-phase HPLC with electrochemical detection at a cell potential of 0.8 V. The method was very sensitive (detection limit 2.5 micrograms/l) and quantitation using 4,4'-ethylenedianiline as an internal standard correlated well with results by gas chromatography-mas spectrometry. Run-to-run precision (n = 25) averaged 8.9%. In analysis of more than 160 potentially exposed workers, MDA was detected in less than 20% of the urines and concentrations ranged up to 210 micrograms MDA per g of creatinine.

Determination of the N-acetyl metabolites of 4,4'-methylene dianiline and 4,4'-methylene-bis(2-chloroaniline) in urine

A sensitive and specific gas chromatographic/mass spectrometric assay is described for the determination of N-acetyl 4,4'-methylene dianiline (N-acetyl MDA) and N-acetyl 4,4'-methylene-bis(2-chloroaniline) (N-acetyl MbOCA) in urine. The method is based on the solvent extraction of the compounds together with deuterium-labelled internal standards, the compounds being separated and detected by capillary gas chromatography/mass spectrometry as their pentafluoropropyl derivatives. The method has been applied to the detection of N-acetyl MbOCA and N-acetyl MDA in the urine of workers occupationally exposed to MbOCA and MDA. The results show that whilst N-acetyl MbOCA is a relatively minor urinary metabolite a significant proportion of MDA is excreted as the N-acetylated compound.

Genotoxicity of epoxy resin hardeners in the hepatocyte primary culture/DNA repair test

The genotoxicity of 9 chemicals used as epoxy resin hardeners was examined in the DNA repair test with rat hepatocytes. DNA repair synthesis was elicited by 7 chemicals, i.e., 4-aminodiphenyl ether, 4,4-diaminodiphenyl ether, 3,4,4'-triaminodiphenyl ether, 3,3'-dichloro-4,4'-diaminodiphenyl ether, 1,3-phenylenedi-4-aminophenyl ether, 4,4'-diaminodiphenyl methane and 4,4'-methylene-bis(2-chloroaniline). The positive results obtained with 4 epoxy resin hardeners of unknown carcinogenicity, i.e., 4-amino-diphenyl ether, 3,4,4'-triaminodiphenyl ether, 3,3'-dichloro-4,4'-diaminodiphenyl ether and 1,3-phenylene-di-4-aminophenyl ether suggest that they may be carcinogens. The genotoxicity of 1,4-phenylene-di-4-aminophenyl ether, of unknown carcinogenicity, and 4,4'-diaminodiphenyl sulfone, for which there is no sound proof of carcinogenicity, was not confirmed in the DNA repair test. The result with 4,4'-diaminodiphenyl sulfone was in agreement with its lack of mutagenicity in Salmonella typhimurium.

Assessment of occupational exposure to 4,4'-diaminodiphenylmethane (methylene dianiline) by gas chromatography-mass spectrometry analysis of urine

A new specific and sensitive method has been used to monitor workers from five different factories where 4,4'-diaminodiphenylmethane (methylene dianiline) (DDM) was being used. The isolation and identification of an N-acetyl conjugate of DDM, a major metabolite of DDM found in human urine, is reported for the first time. The use of this biological monitoring method will allow the assessment of the absorption of DDM and help in monitoring improvements in work practices, particularly where exposure may occur through pathways other than inhalation.

Carcinogenesis studies of 4,4'-methylenedianiline dihydrochloride given in drinking water to F344/N rats and B6C3F1 mice

Carcinogenesis studies of 4,4'-methylenedianiline dihydrochloride (98.6% pure) were conducted by administering this chemical in the drinking water of F344/N rats and B6C3F1 mice. Groups of 50 rats and 50 mice of each sex received drinking water containing 150 or 300 ppm 4,4'-methylenedianiline dihydrochloride (dosage expressed as the free base) for 103 wk. Groups of 50 rats and 50 mice of each sex, given drinking water adjusted with 0.1 N HCl to the pH (3.7) of the 300-ppm formulation, served as controls. Survival was comparable among groups except for male mice receiving the 300-ppm dose of 4,4'-methylenedianiline dihydrochloride; survival in that group was lower than that in controls. Mean body weight was reduced in 300-ppm-dose female rats and 300-ppm-dose male and female mice compared to controls. Water consumption was reduced in a dose-related manner in both sexes of rats. No compound-related clinical effects were observed. Under the conditions of these studies, there was clear evidence of carcinogenicity for F344/N rats and for B6C3F1 mice in that 4,4'-methylenedianiline dihydrochloride caused increased incidences of (1) follicular-cell carcinomas of the thyroid gland (controls, 0/49; low dose, 0/47; high dose, 7/48, 15%; p less than or equal to 0.012) and neoplastic nodules of the liver (controls, 1/50, 2%; low dose, 12/50, 24%; high dose, 25/50, 50%; p less than or equal to 0.001) in male rats, (2) follicular-cell adenomas (controls, 0/47; low dose, 2/47, 4%; high dose, 17/48, 35%; p less than or equal to 0.001) and C-cell adenomas (controls, 0/47; low dose, 3/47, 6%; high dose, 6/48, 13% p less than or equal to 0.029) of the thyroid gland in female rats, (3) follicular-cell adenomas of the thyroid gland (controls, 0/47; low dose, 3/49, 6%; high dose, 16/49, 33%; p less than or equal to 0.001), carcinomas of the liver (controls, 10/49, 20%; low dose, 33/50, 66%; high dose, 29/50, 58%; p less than or equal to 0.001), and pheochromocytomas of the adrenal gland in male mice (controls, 2/48, 4%; low dose, 12/49, 24%; high dose, 14/49, 29%; p less than or equal to 0.001), and (4) follicular-cell adenomas of the thyroid gland (controls, 0/50; low dose, 1/47, 2%; high dose, 13/50, 26%; p less than or equal to 0.001), carcinomas (controls, 1/50, 2%; low dose, 6/50, 12%; high dose, 11/50, 22%; p less than or equal to 0.002) and adenomas (controls, 3/50, 6%; low dose, 9/50, 18%; high dose, 12/50, 24%.(ABSTRACT TRUNCATED AT 400 WORDS)

[The liver and environmental poisons]

For almost a century now numerous examples of acute and subacute hepatic injury from exposure to toxic agents in the occupational or non-occupational environment have been extensively studied and are well documented, but such events are comparatively rare. In contrast, epidemiological data associating exposure to environmental chemicals with chronic liver disease or primary hepatic malignancies in the human is scarce as compared with the vast body of literature concerning chronic pulmonary disease as a consequence of exposure at the workplace. Large-scale industrial production of many newly synthesized organic chemicals began during the period 1930-1940 but it was not until the 1960s that the output increased exponentially. Consequently, the spectrum of environmental influences is gaining increasing complexity since simultaneous or sequential exposure to a variety of pollutants is becoming the rule rather than the exception. Possible interaction or synergism of environmental agents--even of those which in themselves or for their low dosage level may be considered "harmless" - and particularly latency periods of more than one decade further complicate preventive strategies. The liver, as the central site for the biotransformation of xenobiotics, deserves special attention when new chemicals which are to be introduced into the environment are being tested for their potential toxicity, especially since many hepatotoxic agents have been shown to undergo bioactivation in the liver. Currently available information on hepatic injury due to environmental agents is briefly reviewed and comprises solvents and degreasing agents, pesticides, polyhalogenated biphenyls, dioxins and dibenzofuranes, epoxy resin hardeners, vinyl chloride, naturally occurring hepatotoxins in plants and fungi, herbal medicines and traditional remedies and a side-light on the Reye syndrome and the Spanish "toxic oil syndrome".

Methylene dianilene: a new toxic cause of visual failure with hepatitis

A 28-year-old man ingested methylene dianilene in potassium carbonate and gamma-butyrolactone. He developed toxic optic neuritis, with severe visual dysfunction (not previously reported in humans), prolonged toxic hepatitis, with disturbed liver-function tests 18 months after the incident, and other more transient effects. The course of his illness is described and the literature on methylene dianilene toxicity is reviewed.

Occupational hepatitis caused by methylenedianiline

Four of the six workmen who were engaged in laying an epoxy resin based floor developed an acute hepatic illness; in two of these men, the illness recurred on re-exposure a few months later, and their convalescence period was prolonged. It was concluded that methylenedianiline, which was used as the curing agent for the epoxy resin, was the likely hepatotoxin on the basis of marked similarities of these men's symptoms and signs to those described in other published reports about toxic exposure to this compound. To date, there is no evidence of long-term liver damage caused by this widely used industrial chemical.

Subacute toxicity of methylene-bis-(2,6-diisopropylaniline) in the rat and hamster

Methylene-bis-2,6-diisopropylaniline (MDPA), a chemical having potential application as a polyurethane chain extender or an epoxy curing agent, was administered daily by gavage to male Fischer 344 rats and male Syrian golden FVG hamsters. Rats were administered MDPA at 10.5, 21.0, 42.0, 63.0, or 87.5 mg/kg in corn oil for 5, 10, or 28 d. Hamsters received 87.5 or 875 mg MDPA/kg daily for the same periods. Histopathologic evaluation of rat tissue showed diffuse vacuolar change and periacinar vacuolar degeneration of the livers, with congestion, hemosiderosis, and hematopoiesis in the spleen. Hepatic periacinar vacuolar degeneration decreased in incidence and severity from d 5 to d 28, and livers of rats sacrificed 28 d after cessation of MDPA treatment (d 56) were normal. Hepatic vacuolar change was characterized by lipid inclusions. Electron microscopic evaluation found no structural abnormalities in hepatocytes with a moderate level of lipid vacuolization, while degeneration was seen in cells with extensive vacuolization. Stage III, stage IV, and maximal respiratory rates of mitochondria isolated from livers of test animals were higher than age-matched controls after 28 d treatment. At the high dose (875 mg/kg), MDPA produced liver lesions consisting of periacinar vacuolar change, vacuolar degeneration, hepatocytic swelling, and necrosis in hamsters. The high dose also produced acute toxic tubular nephrosis and a high mortality rate. At a dose (87.5 mg/kg) equuimolar to the high dose in the rat, however, the only lesion observed in the hamster was periacinar vacuolar change. In summary, the degenerative hepatic lesion produced in liver decreased in incidence with continued administration, and higher doses were required to produce this lesion in the hamster than in the rat.

Di(4-aminophenyl)-methane (MDA): 4-7 year dog feeding study

9 pure bred female beagles ingested purified or crude MDA (in 70 mg doses on 3 days of the week) over periods ranging from 3 years, 11 months to 7 years, 2 months. Total quantities of MDA ingested ranged from 39.98 g to 66.92 g/dog, or from approx. 4.0 to 6.26 g/kg body wt. Purified and crude MDA in the doses administered produced similar effects: (a)occasional loss of body weight followed by rather prompt recovery while treatment was interrupted; (b) no specific effect on blood sugar, BUN, creatinine, uric acid, total protein, albumin and a questionable effect on alkaline phosphatase activity; (c) from moderate to severe gross and micropathological changes in the liver, less severe effects in the kidneys and spleen, and occassionally gross or micropathological changes in other organs. Purified and crude MDA did not produce tumors of the urinary bladder or liver.

Food contaminants

With the increasing use of a large variety of chemicals, opportunities for contamination of food are becoming greater. Food may be involved following some accidental occurrence or from more general environmental contamination. Three examples are given: an outbreak of paralysis in Morocco involved 10,000 people who had ingested food adulterated with triorthocresyl phosphate; an epidemic of jaundice in London followed the contamination of flour with an epoxy resin hardener; organic mercury poisoning in an Arab country involved more than 6000 people who had eaten bread made from grain treated with a methyl mercury fungicide. The hazard which may arise from heavy metal accumulation in the body is discussed.