OECD test strategies and methods for endocrine disruptors

The question whether (man-made or natural) chemical substances may have an adverse effect on the endocrine system has gained high visibility in the public as well as in the scientific community. This relates to possible effects on the environment as well as on human health for chemicals with (anti)estrogenic, (anti)androgenic or (anti)thyroid activity. Taking into account the broad universe of chemicals to which humans or the environment may be exposed, a sound testing strategy and robust test methods are urgently needed. Both subjects have been addressed by a specific OECD working group (EDTA-Endocrine Disruptor Testing and Assessment Task Force) involving regulatory agencies, the scientific community, chemical industry and NGOs. Like other organizations the OECD has adopted a tiered-testing strategy with the first tier using screening assays as quick and inexpensive tools, providing a way of generating alerts to potential endocrine activity that can be used to prioritize substances for definitive tests that then can determine the toxicological consequences of endocrine toxicity. The efforts of the OECD have therefore concentrated on the validation of specific screening and testing guidelines, like the uterotrophic, the Hershberger, and the "enhanced TG 407" test. The experimental testing necessary for this validation procedure is completed for the uterotrophic and the "enhanced TG 407" tests and near completion for the Hershberger assay. The data obtained so far have been published (for the uterotrophic assay) or will be submitted to the EDTA working group for final evaluation. Overall, the validation program has been very successful and should be sufficient for setting up OECD test guidelines for these experimental procedures. This will add substantially to the "tool-box" of OECD test methods that is available internationally to regulatory agencies and chemical industry for the identification and assessment of possible endocrine disruptors. Despite this success it is well recognized that the methodological "tool-box" should be supplemented by further screening and testing procedures related to effects on human health and the environment.

Evaluation of historical control data in carcinogenicity studies

Results obtained in long-term carcinogenicity studies with animals should be evaluated, first and foremost, by statistical comparisons of the data obtained from the treated group with that from the concurrent control group. Often the results are compared with data from so-called historical control groups in order to take variations in the incidences of spontaneous tumours into account. Because historical control data change in the course of time and for a variety of reasons, certain requirements must be met before they may be used in the evaluation of the results of long-term studies. The present paper discusses potential sources of variability of tumour incidences in untreated animals, presents databanks for historical control data, mentions the factors that affect tumour incidences in untreated animals and describes biostatistical data evaluation. Finally, details are given of the criteria used by the DFG Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area to decide whether historical control data may be applied. These include the requirement that the historical control data were obtained with animals of the same species and strain and from the same breeder. The data were obtained in the same laboratory, the study design, experimental methods and assessment criteria were the same, and the studies used for the comparison were carried out within a limited time window. Historical control data that have not been published may be used provided they fulfil the above criteria and have been made available in sufficient detail to be comprehensible.

Children as a sensitive subgroup and their role in regulatory toxicology: DGPT workshop report

There is increasing discussion that children might be considered as a specific subgroup in public health regulations which could be more sensitive than the average "adult" human being. Differences between children and adults, with regard to susceptibility towards toxicants, may result from a combination of toxicokinetic, toxicodynamic and exposure factors. Kinetic factors are of importance mainly in the early postnatal period, largely as the result of immature elimination systems, i.e. metabolising enzymes and/or renal function. Specific vulnerability may prevail during several time periods, related to the development and maturation of organs (for example, brain, bone, endocrine system). For some substances, it has been shown that children at a specific age are less sensitive than adults. Specific exposures of toddlers to environmental chemicals may be high due to their moving behaviour and hand-to-mouth activities. Existing scenarios and models for exposure of children should be improved, in particular with respect to different ages. The outcome of model calculations must be verified by human biomonitoring analysis. At present, there is ongoing discussion of toxicological test models suitable to delineate human postnatal development. Experience with infant-orientated test systems is scarce (for example in developmental neurotoxicity). In general, tools for predicting toxicological sensitivity of children must be further improved. Regulators should also be aware that reduction of lifestyle-related toxic exposures such as smoking and drug abuse in children and adolescents is now an increasing public health problem in many countries.

Changes in the classification of carcinogenic chemicals in the work area. (Section III of the German List of MAK and BAT values)

Carcinogenic chemicals in the work area were previously classified into three categories in section III of the German List of MAK and BAT values (the list of values on maximum workplace concentrations and biological tolerance for occupational exposures). This classification was based on qualitative criteria and reflected essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. In the new classification scheme the former sections IIIA1, IIIA2, and IIIB are retained as categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to the risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by non-genotoxic mechanisms, and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose/response relationships and toxicokinetics and for which risk at low doses can be assessed are classified in category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for category 4 (1,4-dioxane) and category 5 (styrene) are presented.

Changes in the classification of carcinogenic chemicals in the work area. Section III of the German List of MAK and BAT Values

Carcinogenic chemicals in the work area are currently classified into three categories in section III of the German List of MAK and BAT Values (list of values on maximum workplace concentrations and biological tolerance for occupational exposures). This classification is based on qualitative criteria and reflects essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. It is proposed that these categories - IIIA1, IIIA2, IIIB - be retained as Categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by nongenotoxic mechanisms and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in Category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose-response relationships and toxicokinetics, and for which risk at low doses can be assessed are classified in Category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for Category 4 (1,4-dioxane) and Category 5 (styrene) are presented.

Proposed changes in the classification of carcinogenic chemicals in the work area

Carcinogenic chemicals in the work area are currently classified into three categories in Section III of the German List of MAK and BAT Values. This classification is based on qualitative criteria and reflects essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. It is proposed that these Categories--IIIA1, IIIA2, and IIIB--be retained as Categories 1, 2, and 3, to conform with EU regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, it is now proposed that these three categories be supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not convey a significant risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. It is proposed that chemicals known to act typically by nongenotoxic mechanisms and for which information is available that allows evaluation of the effects of low-dose exposures be classified in Category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose-response relationships and toxicokinetics and for which risk at low doses can be assessed will be classified in Category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for Category 4 (1,4-dioxane) and Category 5 (styrene) are presented. The proposed changes in classifying carcinogenic chemicals in the work area are presented for further discussion.

Assessment of structurally related chemicals: toxicity and ecotoxicity of acrylic acid and acrylic acid alkyl esters (acrylates), methacrylic acid and methacrylic acid alkyl esters (methacrylates)

BUA compiled the available data on toxicity and ecotoxicity for several acrylic and methacrylic acid esters and their corresponding acids. A comparison of these data revealed a qualitative similarity in the toxicological and ecotoxicological properties of the compounds considered. The data indicate that methacrylates are less reactive than the corresponding acrylates.

In vitro cytotoxicity of glycol ethers and oxidation products in CHO cells

The cytotoxicity of several glycol ethers and of some of their oxidation products, the corresponding alkoxy acetates, was compared in Chinese hamster ovary (CHO-K1) cells without metabolic activation. Cytotoxicity was measured in terms of cloning formation ability, and EC50 values (concentrations allowing 50% of the seeded cells to form colonies) were estimated. The results, in the case of unmetabolized glycol ethers tested, showed an increase in toxicity with increasing chain length. The cytotoxicity of the corresponding alkoxy acetates, however, did not exhibit a trend in parallel with the chemical structure. 2-Methoxypropionic acid was somewhat less cytotoxic than the alkoxy acetic acids investigated. It is concluded that gross cytotoxicity to dividing cells is not the predominant mechanism for the teratogenicity or myelotoxicity and testes toxicity of methoxy- and ethoxyethanol, which produce these effects after oxidation to their corresponding alkoxy acetates.

An embryotoxicity study of the fungicide tridemorph and its commercial formulation Calixin

Tridemorph (N-tridecyl-2,6-dimethylmorpholine), the active ingredient of the commercially formulated fungicide Calixin, is a teratogen in rats and mice. The no-effect level for embryotoxic effects was 27.5 mg/kg for mice and 20.6 mg/kg for rats. By contrast, when Calixin, which contains 83% tridemorph, was administered orally at dose levels of 0.156, 0.722, and 3.909 mg/kg, no embryotoxic effects were observed in two strains of rats. Our extensive investigations, carried out under exposure conditions resembling as closely as possible those reported in another study, did not reproduce the previous findings of teratogenicity of Calixin.

[Frequency of positive diazepam-screening in post-mortem examinations (author's transl)]

The post-mortem blood specimens of 389 forensic autopsies were analyzed for diazepam. The age of the cases investigated was above 10 years and the survival time was less than 12 hours. Eighteen samples corresponding to 4.6% were found to be diazepam-positive. These 18 samples were distributed equally between men and women. The proportion of diazepam-positive samples was increased in the groups of suicide and poisoning (alcohol and opiates). The association between diazepam intake and poisoning was statistically highly significant. No correlation was found between diazepam intake and age. Alcohol was found to occur significantly more often in the group of the diazepam positive cases as compared to the diazepam negative group.

[Impairment of performance by alcohol and diazepam (author's transl)]

An investigation was carried out on the effect of the intake of diazepam and alcohol on simple performance tests. The combined administration of diazepam and alcohol led to an increase of the plasma diazepam concentration as compared to that obtained after diazepam without alcohol. Furthermore, after combined intake of diazepam and alcohol a decrease of performance was observed, that was significantly higher, than the effects obtained after either alcohol or diazepam alone. This impairment was especially noticeable duirng the first hour of the experiment, i.e. until the plateau of the diazepam plasma concentration was reached, while afterwards a correlation between diazepam plasma concentration and impairment of performance could not be established. The relevance of these findings for the interpretation of diazepam plasma concentrations in relation to the impairment of performance are discussed.

Formation of thermally stable derivatives of chlordiazepoxide and its desmethyl metabolite for GLC

A derivatization procedure is described for the GLC determination of subnanogram amounts of chlordiazepoxide and nanogram amounts of N-desmethylchlordiazepoxide. Treatment with acetic anhydride at elevated temperature eliminates the highly polar and unstable nitrone group of these compounds by rearrangement and acetylation. The mass spectrometric fragmentation pattern of the acetyl derivatives is recorded and interpreted.

Fatal poisoning with a plant protective containing monocrotophos, dodine and dinocap

The toxicological findings after fatal poisoning with a plant protective containing monocrotophos, dodine and dinocap are described and discussed. While monocrotophos could be measured in all tissues and in blood 12 microgram/g, lung 13 microgram/g, brain 13 microgram/g, kidney 11 microgram/g, liver 1.8 microgram/g), measurable amounts of dodine (detection limit approx. 3 microgram/g) and dinocap (detection limit approx. 4 microgram/g) were not detected in these materials. The gastric contents contained 52 mg of monocrotophos, 7.5 mg of dodine and 20 mg of dinocap.

A micromethod for the isolation of drugs from blood using amberlite XAD-2

The extraction of drugs from small blood samples (1 ml or less) for subsequent quantitative determination is described. Isolation was carried out by adsorption of the drugs to Amberlite XAD-2 resin utilizing a batch procedure that enabled the simultaneous extraction of up to 200 samples in approx. 5 hours. A new desorption technique yielded extracts of high purity that could be used directly for gas chromatographic or radioimmunological determinations, even if hemolyzed or putrid blood was to be examined. The following 26 substances were quantitated after addition to postmortem blood speciments at concentrations of 1-10 microgram/ml: tilidine, diphenhydramine, dibenzepine, imipramine, chlorpromazine, amphetamine, pentazocine, phenacetin, methaqualone, meprobamate, parathion, diazepam, digoxin, beta-methyldigoxin, carbromal, glutethimide, amobarbital, pentobarbital, cyclobarbital, phenobarbital, diphenylhydantoin, carbutamide, tolbutamide, glycodiazin, tolazamide and chlorpropamide. Thereby recoveries of 60-100% could be achieved. The reproducibility of the procedure was satisfactory as demonstrated by coefficients of variation of 3.7-8%.

[Occurrence of diazepam in blood samples of drivers under the influence of alcohol (author's transl)]

Diazepam was determined by radioimmunoassay and gas chromatography in 2050 unselected blood or serum specimens of subjects, who were sus,ected of driving under the influence of alcohol in the years 1974 and 1976. A "cut-off" limit of 20 ng/ml was selected. Diazepam was found in 46 samples corresponding to 2.24%, 27 samples (1.3%) exhibited concentrations of 20--100 ng/ml, 14 samples (0.7%) of 100--500 ng/ml, 1 sample (0.05%) of 500--1000 ng/ml and 4 samples (0.2%, as related to the total of 2050 samples) of more than 1000 ng/ml. Furthermore, 44 blood specimens of subjects were analyzed, who had claimed diazepam intake before the blood sample was withdrawn. Diazepam was found in 27 cases corresponding to 61%. Finally, blood specimens of 219 unselected inpatients of a surgical ward were investigated; 59 of these (27%) were found to be diazepam-positive.

Isolation of drugs from blood by column chromatography on Amberlite XAD-2

An investigation was carried out on the isolation of 28 drugs from blood by column chromatography on Amberlite XAD-2. The following substances were added to postmortem blood specimens at concentrations generally of 1--10 microgram/ml: barbital, heptabarbital, hexobarbital, pentobarbital, phenobarbital, phenylbutazone, monocrotophos, amidopyrine, carbromal, diazepam, meprobamate, methaqualone, nitrazepam, phenazetin, chlorpromazine, dibenzepin, diphenhydramine, haloperidol, imipramine, mescaline, methadone, morphine, pentazocine, pethidine, tilidine, triflupromazine, verapamil, N-propylajmalinium bitartrate. The samples were purified by column chromatography on Amberlite XAD-2 and simple solvent extraction and subsequently quantitated by gas chromatography. By systematic variation of the conditions for adsorption of the drugs and desorption from the resin, revoveries of more than 80% after XAD-2 column chromatography could be achieved for most drugs. Thereby it was demonstrated, that in cases of fatal poisoning or emergencies this procedure is a valuable tool for forensic and clinical toxicologists who have to find out the toxic agent by chemical analysis of the blood.

Radioimmunological screening and gas chromatographic identification of diazepam in blood and serum

A radioimmunoassay for the determination of diazepam in human blood and serum is presented. Diazepam is separated from the bulk of the biological material by adsorption at Amberlite XAD-2 and subsequent desorption with ethyl acetate. The extract thus obtained can be used directly for the determination od diazepam by radioimmunoassay and gas chromatography with electron capture detection. For the combined radioimmunological and gas chromatographic determination 0.5 ml of blood or serum are necessary, the lower detection limit being approx. 5 ng/ml for both of these procedures. A good reliability of the radioimmunoassay is established with respect to precision, accuracy and specificity. The quantitative results obtained by radioimmunoassay and gas chromatography correspond well with each other. The radioimmunological procedure enables the screening of more than 200 samples for diazepam by one technician within two working days.

Influence of rifampicin treatment on the metabolic fate of [4-14C] mestranol in women

[4-14C] Mestranol was administered to 2 rifampicin treated and to 3 untreated hysterectomised women with normal liver functions. The urinary excretions of mestranol, ethynylestradiol, 2-hydroxy-ethynylestradiol and of the total radioactivity were measured within the following 5 days. After this period the total urinary excretion of radioactivity amounted to approx. 43% (38%-50%) of the administered dose and no difference was found for the rifampicin treated and untreated women. Moreover, in the urines of both of these groups the same amounts of radioactive mestranol (1.1%-6.3% of the urinary radioactivity) and 2-hydroxy-ethynylestradiol (0.9%-3.9% of the urinary radioactivity) were measured. In contrast, the urinary excretion of ethynyl-estradiol was definitely lower in the rifampicin treated women (3.5% and 4.9% of the urinary radioactivity) as compared to the control group (15%-23%).

Suicide by an overdosage of N-propylajmalinium bitartrate

The toxicological findings after suicidal poisoning with N-propylajmalinium bitartrate (NPAB) are presented. For isolation of NPAB the biological material was homogenized and the drug was isolated by adsorption on Amberlite XAD-2. After column chromatographic purification on Sephadex LH-20 quantitative determinations were carried out by gas chromatography of the trifluoroacetate. The identity of the material finally obtained was checked by various chromatographic and spectrometric methods. The following concentrations of NPAB were found: liver 58 microgram/g, kidney 32 microgram/g, brain 16 microgram/g, muscle less than 10 microgram/g, heart less than 5 microgram/g, blood less than 5 microgram/g, gastric contents 600 mg (total). 1200 mg of NPAB had been swallowed; thus the amount of NPAB, that had crossed into blood, was approx. 500-600 mg corresponding to a dose of 9-11 mg/kg body weight.

Fatal poisoning with verapamil

The toxicologic findings in a case of fatal poisoning with verapamil (Isoptin) are are presented. For isolation of verapamil the biologic material was subjected to protein precipitation. The aqueous solutions were acidified with hydrochloric acid, prepurified by extraction with ether, and subsequently the basic drug verapamil was isolated by ion pair extraction with chloroform. Quantitative determination of verapamil was carried out by gas chromatography using a nitrogen specific flame ionization detector. The following concentrations of verapamil were measured: liver 5500 ng/g, kidney 2000 ng/g, blood 590 ng/g, urine 250 ng/g, gastric contents 3 mg (total). During examination by the police it was claimed by a witness that two tablets of Isoptin had been taken before death. After application of a therapeutic dose of Isoptin peak concentrations of 11 and 30 ng/g of blood cells and of 30 and 65 ng/g of plasma were measured in two healthy subjects; the latter figures corresponded well to previous findings of other authors, who investigated plasma concentrations of verapamil after therapeutic administration. In the case presented here, the blood concentration of 590 ng/g clearly demonstrated that an extreme overdose must have been taken before death.

[Determination of morphine in the vitreous and cerebrospinal fluid by radioimmunoassay (author's transl)]

In 12 cases of fatal poisoning with morphine or heroin a radioimmunological determination of morphine was carried out in vitreous humor, cerebrospinal fluid and urine. The concentrations varied between 30 and 350 ng of morphine-equivalents/ml in the cerebrospinal fluid and between 45 and 280 ng/ml in the vitreous humor (urine concentrations: 120-100.000 ng/ml). The counts per minute differed significantly for samples with and without prior ingestion of morphine, when vitreous and cerebrospinal fluids were tested by the morphine (3H) radioimmunoassay. Thereby it was clearly demonstrated, that radioimmunoassay is a valuable screening procedure for the rapid identification of morphine in corpses, even when urine is not available.

Pryogalloloestrogens -- a new group of oestrogen metabolites

After incubation of radioactive catecholoestrogen monomethyl ethers with rat liver slices the following well known metabolic pathways were observed: 1) demethylation, 2) 16alpha-hydroxylation, 3) oxidoreduction at C-atom 17, and 4) conjugation with glutathione, sulphuric acid and glucuronic acid. In addition, for the first time a further aromatic ortho-hydroxylation, leading to pyrogalloloestrogen derivatives, was detected. Thus, the incubation of 2-methoxyoestrone yielded 2,4-dihydroxyoestrone 2-methyl ether as the main metabolite of the lipophile fraction. Under the same conditions, 4-methoxyoestrone was converted to 2,4-dihydroxyoestrone 4-methyl ether and 2,4-dihydroxyoestradiol-17beta 4-methyl ether; these compounds were the quantitatively most important metabolites not only in the lipophile but also in the sulphate and glucuronide fractions. The identity of these new metabolic products was established by chromatography, microchemical reactions and recrystallisation to constant specific radioactivity.

Excretion of 2-hydroxyestrone in urine throughout human pregnancies

Urinary 2-hydroxyesterone was quantitatively determined in the course of several normal human pregnancies. The urine was subjected to hot acid hydrolysis and after chromatographic purification, 2-hydroxyesterone was converted into the corresponding phenazine derivative, which was submitted to a final column chromatogrphy and then quantitated by UV-spectrometry. For correction of procedural losses 2-hydroxyestrone-4-14C was used as internal standard. The urinary 2-hydroxyestrone of different subjects varied within a wide range especially at mid-pregnancy between 100 and 2500 mug/24 h. The day-to-day variation of the excretion of 2-hydroxyestrone was mostly less than 30% of the total value of that day, but sometimes could even reach 60%. The investigation of 2-hydroxyestrone and total estrogens at regular intervals throughout several pregnancies, showed that the excretion of 2-hydroxyesterone generally reached a maximum during the second trimester, while the excretion of the total estrogens steadily increased up to parturition. When analyzing the urines of different subjects during the last 4 months of pregnancy, no correlation appeared to exist for the excretions of the total estrogens and of 2-hydroxyestrone.

The excretion of 2-hydroxyestrone during the menstrual cycle

A double isotope derivative determination technique was developed to investigate the excretion of 2-hydroxyestrone inhuman menstrual cycle. The method is highly specific, accurate and precise within the range of 0.2-20 nmol 2-hydroxyestrone/20ml of urine. The amounts of 2-hydroxyestrone excreted during menstrual cycle varied between 10 (proliferation phase) and 60 mug/24 h urine (ovulatory peak), which is comparable to that of estriol, supposed hitherto to be the main excretion product of estrogen metabolism.