Letter: Chromosomal and dominant lethal effects of vinyl chloride

Fifty years of cytogenetics: a parallel view of the evolution of cytogenetics and genotoxicology

A parallelism exists between human cytogenetics and cytogenetic toxicology. The breakthroughs, mostly coming from and used in clinical genetics, are widely used in genetic toxicology. The birth of human cytogenetics occurred in 1956 when it was published that the diploid number of chromosomes in humans is 46. The first stage in chromosome-induced mutagenesis began in 1938 when Sax published the effects of X-rays on the chromosomes of Drosophila. In 1959, the cytogenetic anomalies for Down, Klinefelter, and Turner syndromes were described, and parallelly in 1960, the first publication on chromosomal aberrations in man caused by ionizing radiation appeared. The cytogenetic analysis of chromosomal aberrations in cell cultures is considered one of the primary methods to evaluate induced mutagenesis. At the end of the 1960s, banding techniques allowed chromosomes to be individually identified, in parallel, the sister chromatid exchange analysis technology was described. Another milestone in the history of induced mutagenesis was the discovery that mutagenic agents were able to alter chromosomal division and segregation in gonads inducing meiotic nondisjunction. Here we review new approaches and applications such as biological dosimetry, translocation scoring using FISH, and micronucleus test. Chromosomal aberrations and micronucleus test are now effective cytogenetic biomarkers of early effect used as cancer predictors. Human cytogenetics has proven to be effective over its 50-year lifespan and, although each new technique that has appeared seemed to announce its end, the fact is that the current state of cytogenetics is in reality a collection of techniques that, while common, are cheap, fast, and wide-ranging. Therefore, in genotoxicology, they continue to be useful to identify mutagenic agents as well as to evaluate and analyze exposed populations.

Factors affecting various biomarkers in untreated lung cancer patients and healthy donors

The purpose of the present communication was to determine in lung cancer patients and healthy donors if there was a possible association between cancer and biomarkers of cytogenetic damage and ras p21 oncoprotein levels, and if various exogenous confounding factors (such as smoking habit) and endogenous ones (age, sex, etc.) could affect these biomarkers. Peripheral blood and plasma were collected from 31 lung cancer patients prior to treatment and 35 healthy donors of a similar socioeconomic status and from the same region in Poland. Chromosomal aberrations (CA), sister chromatid exchanges (SCE), high frequency cells (HFC), and proliferative rate index (PRI) were examined from the blood and ras p21 oncoproteins from the plasma. These parameters were used as biomarkers of genotoxic anomalies. All the biomarkers were examined for their relationship to confounding factors of age, sex, smoking habit, and immediate family cancer history. Results were analyzed by a t-test, analysis of variance (ANOVA), and stepwise multivariate regression analysis. All types of CA (including and excluding gaps), percent aberrant cells, SCE, and ras p21 oncoproteins were statistically significantly higher in cancer patients than in the healthy donors. Although there were smaller numbers of females in the cancer patients group who were older than the males, there was a difference due to sex (gender) with statistically significant increases in females for CA, SCE, and HFC, but there was no increase for ras p21 oncoproteins. Cytogenetic damage was not related to other cancers in the immediate families of the groups. All major CA parameters differed significantly between smokers and non-smokers in the cancer patients group, and SCE and HFC differed in the healthy donors group. Such parameters also showed a significant variability with the number of cigarettes smoked and the years of smoking habit. Multivariate regression analyses showed a significant association between cytogenetic damage, ras p21 oncoproteins, and cancer. In conclusion, cytogenetic damage and ras p21 oncoproteins in this study appear to be biomarkers associated with cancer, but have not been proved causally, and confounding factors such as age, sex (gender), and smoking can have an impact on them.

Genetic toxicology of vinyl chloride--a review

Vinyl chloride (VC) is a colorless gas with a mild, sweet odor. It is extensively used in the production of vinyl chloride polymer, copolymer resin, packaging materials, wire and cable coatings as well as in industrial and laboratory intermediates. It is toxic and also carcinogenic in experimental animals. The wide human exposure to this compound in different industries throughout the world causes great concern for human health. In the present review an attempt has been made to evaluate and update the genotoxic effects of vinyl chloride based on the available literature.

Chromosomal aberrations and sister-chromatid exchanges in lymphocytes from coke oven workers

To test whether coke oven workers, an occupational group known to be at increased cancer risk, manifest increased peripheral blood chromosomal aberration frequencies, we obtained samples from a group of 30 steelworker volunteers, who had worked several years at coke oven jobs. Exposure estimates were made using measurements of work place atmospheric coal tar pitch volatiles and work histories. No statistically significant positive regression of chromosomal aberrations on exposure estimates was found. The data from the coke oven workers were also compared with the obtained concurrently and employing precisely the same laboratory protocol from a group of male Brookhaven National Laboratory employees. The coke oven workers as a group were found to have statistically significantly elevated frequencies of chromatid aberrations and of sister-chromatid exchanges.

Teratogens and the male. An analysis with special reference to herbicide exposure

A review of the experimental evidence and of the human clinical and epidemiological studies relating to possible teratogenesis after exposure of the male to toxic substances is presented. Toxic insults to the process of gametogenesis can occur either in the male or in the female. Temporary infertility can occur in males exposed to toxic substances, and teratospermia is well documented. An increased miscarriage rate among the wives of men chronically exposed to toxic substances has been reported. A number of experiments have been conducted to study the progeny of male mammals poisoned with proven mammalian teratogens. In none of these studies has the teratogenic syndrome (easily demonstrable as an effect of the drug or toxin when ingested by the pregnant mother) appeared in the offspring of a male who has been exposed to the toxin. Epidemiological studies in humans have given no positive evidence that the baseline congenital malformation rate of children is increased if the father has been exposed to toxic substances. The available evidence indicates that spermatogenesis is particularly resilient after exposure to various toxic chemicals.

Pulmonary manifestations of vinyl and polyvinyl chloride (interstitial lung disease). Newer aspects

Newer varieties of occupational lung diseases primarily due to the vast increase in industrial technology have been reported recently. Preeminent among such newer agents are vinyl chloride (VC) and polyvinyl chloride. Very few cases have been reported, in Europe only, with descriptive histopathologic changes. To our knowledge, no pathologic studies of VC exposure have been described in the American literature. The biopsy abnormalities in our patients disclosed desquamation of alveolar macrophages into the alveolar lumina and minor interstitial and alveolar inflammatory changes. Pulmonary function abnormalities included restrictive insufficiency. Preventive therapy consists of the avoidance of further exposures, frequent industrial hygiene monitoring, and total avoidance of tobacco smoke, as well as associated atmospheric pollutants. Thus far, none of these patients has exhibited evidence of pulmonary neoplasms. All three patients survived their occupational injuries, and two are still disabled to varying degrees. Urine and blood levels of phthalic acid derivatives were elevated in two patients, the exact significance of which is not fully known. It probably represents a toxicologic response, but must be further pursued before conclusions can be reached.

Vinyl chloride mutagenesis in Drosophila melanogaster

In inhalation experiments, Drosophila males were exposed to vinyl chloride at concentrations of 200, 850, 10,000 30,000 or 50,000 ppm for 2 days, and to 30 or 850 ppm for 17 days. VCM was mutagenic in the recessive-lethal test both after short-term and long-term exposures. The lowest effective concentration (LEC) was 850 ppm after 2 day exposure, and this value could be lowered to 30 ppm by prolonging the exposure time to 17 days. With the concentration levels tested, the mutation frequency increased with concentrations and reached a plateau at 10,000 ppm. This indicates a substrate saturation effect. In contrast with the recessive lethal assay, negative results were obtained when tests on dominant lethals, translocations, entire and partial sex-chromosome loss were carried out with VCM at 30,000 ppm for 2 days. This finding of a false negative seems a logical consequence of the observed saturation effect, and strengthens the concept that there exist two effective concentrations for point mutations vs the induction of chromosome breakage events. Vinyl chloride monomer provides another example to support our view that chromosome breakage is not a reliable measure of mutagenic activity.

Lack of mutagenicity of vinyl chloride in two strains of Neurospora crassa

No detectable induction of mutations could be found in two strains of Neurospora crassa after their conidia were treated with vinyl chloride, in ethanol solution and in its gaseous form. The results suggest that although N. crassa seems to lativating systems does not increase mutagenic activity of vinyl chloride in the two strains tested. At the same time these strains were mutated easily by UV and methyl methanesulfonate.

Carcinogenic, mutagenic and teratogenic risks associated with vinyl chloride

The data presented demonstrate clearly that vinyl chloride (VC) is related to a significant excess of mortality from cancer of the liver, lung and brain among workers occupationally exposed to VC. The risk of dying from cancer of the lymphatic and hematopoietic system also appears to increase with an increase in latency. These cancer sites could have been predicted by the animal bioassay conducted by Maltoni. With regard to the liver, even the histophthologic type of cancer (angiosarcoma) was observed first in experimental animals. A study of cancer mortality among populations residing proximate to VC polymerization facilities also demonstrated an increased risk of dying from CNS and lymphatic cancer. These latter findings raise cause for concern about out-plant emmissions of VC, but without further study these cancers obviously cannot be interpreted as being related to out-plant exposure to VC. Various test systems now have elicited a positive mutagenic response to VC. Thus, our observations of a significant excess of fetal mortality among the wives of males, who were occupationally exposed to VC, raise public health concern that VC may be mutagenic in humans. With regard to the teratogenicity of VC, observations of a significant excess of children born with birth defects were reported among populations residing proximate to VC polymerization facilities. Additional epidemiologic study is needed to determine whether a repeated pattern of excessive numbers of children born with birth defects can be observed in other communities with VC polymerization facilities.

Genetic risks of vinyl chloride

A study of pregnancy outcome among wives of workers exposed to vinyl-chloride monomer (V.C.M.) indicated that, in comparison with controls, there was a significant excess fetal loss in the group whose husbands had a primary exposure to V.C.M., whereas no differences between the groups were observed before the husband's exposures. The difference in fetal death-rates for the post-exposure comparisons was a reflection of a greater fetal loss associated with the wives younger-aged husbands. The significant excess did not seem to be the result of bias from interviewers, respondents, nor from women who had experienced chronic abortions weighting the results. These findings, in conjunction with the demonstration of a mutagenic response via microbial test systems and with observations of significant excesses of chromosomal aberrations among workers exposed to V.C.M., raise scientific and public-health concern for the possible genetic risks of V.C.M. to man.

Industrial mutagens and potential mutagens I. Halogenated aliphatic derivatives

The halogenated aliphatic hydrocarbons represent one of the most important categories of industrial chemicals from a consideration of volume, use categories, environmental and toxicological considerations and hence most importantly, potential population risk. The major halocarbons reviewed, primarily in terms of their occurrence, utility, stability, distribution, and levels of exposure as well as their metabolism, carcinogenicity and mutagenicity included: vinylchloride, vinylidene chloride, trichloroethylene, perchloroethylene, ethylene dichloride, ethylene dibromide, chloroprene, chloroform, carbon tetrachloride, fluorocarbons (trichlorofluoromethane and dichlorodifluoromethane), epichlorohydrin, halohydrins (2-chloro- and 2-bromoethanol) and haloethers (bis(chloromethyl); chloromethyl'-methyl; bis(2-chloroethyl)-and bis(2-chloroisopropyl)ether. In many instances, data were not available to assess world production, populations at risk and degrees of exposure. With the exception of vinylchloride, vinylidene chloride, epichlorohydrin and 2-halo ethanols, there is an acknowledged paucity of definitive mutagenicity data concerning the majority of halogenated hydrocarbons. Their ubiquitous distribution, and in a number of cases, their carcinogenicity both in man and animals, dictates the urgent need to more exhaustively investigate their potential mutagenicity.