William Lijinsky

Studies on the toxicity of petroleum waxes

1. n1. The experimental approach to the problem of determining the safety of petroleum waxes as incidental additives to human food is discussed. n n2. n2. Thirty-six samples of petroleum wax were analyzed for polycyclic aromatic hydrocarbons. Eight samples contained identifiable hydrocarbons. Benz[a] anthracene, benzo[e]pyrene, chrysene, flouranthene, pyrene, and triphenylene were identified. The highest concentration of polycyclic hydrocarbon was 0.64ppm. No correlation was observed between polycyclic aromatic hydrocarbon content and any physical characteristic of the waxes, including crystalline form. n n3. n3. The elution of polycyclic aromatic hydrocarbons added to petroleum waxes by milk, skimmed milk, and butter fat has been studied by absorption spectroscopy and using C14-labeled hydrocarbon. Both the fat and protein components of milk were responsible for the elution. The four polycyclic aromatic hydrocarbons studied were eluted at comparable rates. Elution from paraffin wax was considerably greater than from microscrystalline wax. No relation was found between elution of polycyclic aromatic hydrocarbon and oil content of wax. Very little of the eluted material remained as free hydrocarbon in the milk. n nThe elution in the gut of rats and mice of dibenz[a,h]anthracene added to waxes has been studied by absorption spectroscopy and using labeled hydrocarbon. The proportion of dibenzanthracene eluted from the wax was high, although most of the eluted material did not pass into the animal. Direct measurement of the radioactivity in the carcass showed that 6–20% of the radioactive material in the wax had passed through the intestinal wall, but none of this was present as the free hydrocarbon. n n4. n4. Five petroleum waxes were tested by repeated skin application in benzene solution to mice and rabbits. In addition one of the test waxes was fractionated and its aromatic and nonaromatic components were tested separately on mice, also by repeated skin applications. Solvent-treated controls were kept. No carcinogenic effect was detected. n n5. n5. Five petroleum waxes were tested in mice by subcutaneous implantation in disk form. Fibrosarcomas developed around the implants with incidences correlated to the melting points of the waxes. In addition, one of the test waxes was fractionated and its aromatic and nonaromatic components were tested separately; the same wax was also tested subcutaneously in powdered form. The findings indicate that the subcutaneous sarcomas occurred as a result of the physical rather than the chemical properties of the materials. n n6. n6. Five petroleum waxes were tested by feeding in rats at a 10% level in the diet for a period of two years, following which the rats were observed until their death. No carcinogenic or toxic effect was detected. n n7. n7. Untreated groups of Swiss mice of both sexes and of Sprague-Dawley rats of both sexes were observed for their whole life span and then submitted to complete autopsy and to histologic examination. All the tumors observed are reported. n n8. n8. The conclusion drawn from the results of the chemical and biological experiments is that no carcinogenic or other toxic hazard has been demonstrated in petroleum waxes used in food packaging or other food applications.

Morphology of early changes in liver carcinogenesis induced by methapyrilene

Two weeks of treatment with the liver carcinogen methapyrilene induced a significant increase in mitochondria of periportal hepatocytes in F344 rats. Administration of [3H]-methapyrilene hydrochloride resulted in a pronounced concentration of bound radioactivity in the periportal hepatocytes, with mitochondria being the principal site of intracellular binding. The nuclei of the liver cells were unlabeled.

The detection of polycyclic aromatic hydrocarbons in liquid smoke and some foods

Abstract Samples of liquid smoke, several smoked foods, vegetable oils, and water were examined for the presence of polycyclic aromatic hydrocarbons. The aromatic materials were concentrated by extraction and solvent partition, the polycyclic aromatic hydrocarbons were separated by chromatography and identified and estimated by absorption spectrometry. Polycyclic aromatic hydrocarbons were absent from the water and vegetable oils, but were present in bacon, smoked salmon, smoked haddock, and liquid smoke at concentrations of the order of parts per billion. Traces of the carcinogen benzo[ a ]pyrene were present in smoked salmon and smoked haddock, but no carcinogens were detected in bacon or in the two samples of liquid smoke examined.

Purification and Toxicity of Aflatoxin Gl.

Summary A method for quantitative analysis of crude aflatoxin mixtures is described, using thin layer chromatography and absorption spectrometry. Highly purified aflatoxin G l has been prepared by thin layer chromatography and is a blue fluorescent compound, not, as previously reported, green fluorescent. The toxicity of the purified compound does not differ from that of the less pure compound containing a yellow impurity. Both aflatoxins Bl and Gl are fairly stable in aqueous solution in the dark, but undergo rapid decomposition in light (40% in 1 day; almost 100% after 9 days).

Rate of Metabolism of 9,10-Dimethyl-1,2-Benzanthracene in Newborn and Adult Mice.

Summary Determination of the proportion of free 9,10-dimethyl-1,2-benzanthracene remaining in newborn and in adult mice following intraperitoneal injection, revealed that this compound disappeared more quickly from the adult than from the newborn animals. This supports the view that the greater susceptibility of the newborn to tumor induction by this carcinogen is due to longer persistence of the compound in the newborn than in the adult.

Polycyclic aromatic hydrocarbons in commercial solvents

Abstract Samples of benzene, hexane, isooctane, and toluene were examined by adsorption and partition chromatography, followed by spectroscopic analysis of the fractions. Several polycyclic aromatic hydrocarbons were identified in all the samples. One sample of hexane contained significant concentrations of benzo[ a ]pyrene and benz[ a ]anthracene, in addition to other compounds.

Liposolubility as an aspect of nitrosamine carcinogenicity: quantitative correlations and qualitative observations.

Carcinogenicity data for a number of nitrosamines have been examined for possible structure-activity correlations with liposolubility by the method of Hansch. Correlations were found in two cases which support a previous mechanistic suggestion and which also suggest a possible difference between the action of nitrosopiperidines and dinitrosopiperazines in inducing olfactory carcinomas. No correlations were found for non-cyclic nitrosamines.

Skin tumorigenesis by an extract of amber petrolatum

Abstract A sample of amber petrolatum has been resolved into aliphatic and aromatic fractions. The aromatic portion was separated into two components by solvent partition. The aromatic portion and the two subfractions were tested in isooctane solution at 50 times their concentration in the petrolatum, and all showed significant carcinogenicity to mouse skin. The petrolatum itself, tested as a 15% solution in isooctane, showed no significant tumorigenic activity. The tumorigenic activity detected in the fractions cannot be ascribed to any of the compounds so far identified in the original sample.

Comparative metabolism of the cis and trans isomers of N-nitroso-2-6-dimethylmorpholine in rats, hamsters and guinea pigs☆

The in vivo metabolism of the cis and trans isomers of N-[3,5-3H]nitroso-2,6-dimethylmorpholine (NDMM) was studied in female Fischer rats, Syrian golden hamsters and guinea pigs by analysis of urinary metabolites using high pressure liquid chromatography (HPLC). Animals were treated by gavage with 12 mg/kg body wt. of NDMM, composed of both isomers and 12 microCi/kg body wt. of either of the separated radioactive isomers (cis or trans). Control animals received 12 mg, 12 microCi/kg body wt. NDMM with both isomers labeled in their natural proportion. There was a substantial increase in the excretion of a particular metabolite, 2-(2-hydroxyl-methyl)ethoxy propanoic acid, in the urine of rats, hamsters and guinea pigs 24 h after received the trans isomer (24, 22 and 13% of the total dose excreted, respectively). A minor metabolite was determined to be 2,6-dimethylmorpholine-3-one, another product of alpha-oxidation. The metabolite 1-amino-2-hydroxypropanol was identified, indicating that NDMM was metabolized by both alpha- and beta-oxidation. In all three species, animals administered the cis isomer excreted larger amounts of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) and N-nitroso-bis(2-hydroxypropyl)amine (BHP) products of beta oxidation, than those treated with the trans isomer. Hamsters and guinea pigs treated with the more carcinogenic cis isomer in these species, also excreted twice as much of two other metabolites than was found in the urine of animals given the trans isomer. The trans isomer of NDMM appeared to be preferentially metabolized by alpha-oxidation and from earlier studies this metabolic pathway seemed to be important in carcinogenesis by NDMM in the rat. The cis isomer might be in a conformation more favorable for beta-oxidation and this pathway may be of primary importance in carcinogenesis by NDMM in hamsters and guinea pigs.

Methaphenilene, an analogue of the antihistaminic methapyrilene, is a "peroxisome proliferator".

The antihistaminic methapyrilene has been identified as a strong hepatocarcinogen in the rat (Lijinsky et al. 1980). In view of their abundant mitochondria, the induced hepatocellular carcinomas were diagnosed as oncocytomas (Reznik-Sch~ller and Reuber 1981). The mitochondrial increase characteristic of this tumor type was a]ready manifest after 2 weeks of treatment (Reznik-Schflller and Lijinsky 1981). The present experiment was conducted to study the effects of methaphenilene, an analogue of methapyrilene having a benzene ring in place of pyridine. By quantitative electron microscopic morphometry we found that after 2 and 3 weeks of treatment with metbaphenilene the peroxisome/ mitochondria ratio in hepatocytes increased from 2:5 in the controls to 6:5 and 8:5, respectively. This effect was not restricted to any particular area (eg. periportal, centrilobular) of the l iver. All other cell organelles appeared to be within the normal range morphologically and numerically. The effect of replacing the pyridyl in methapyrilene with phenyl is to increase the number of peroxisomes in rat hepatocytes, in contrast with the mitochondrial proliferation induced by methapyrilene. Both of these organelles are involved in oxidative metabolic pathways of the cell although they serve different functions. I t is not certain that the increase in mitochondria or peroxisomes is associated with carcinogenesis by this group of antihistaminics.