Human teratogenic and mutagenic markers in monitoring about point sources of pollution

Effects of low-level radio-frequency (3kHz to 300GHz) energy on human cardiovascular, reproductive, immune, and other systems: A review of the recent literature

OBJECTIVES

Occupational or residential exposures to radio-frequency energy (RFE), including microwaves, have been alleged to result in health problems. A review of recent epidemiological studies and studies of humans as subjects in laboratory investigations would be useful.

METHODS

This paper is a narrative review of the recent medical and scientific literature (from mid-1998 through early 2006) dealing with possible effects of RFE on humans, relating to topics other than cancer, tumors, and central nervous system effects (areas covered in a previous review). Subject areas in this review include effects on cardiovascular, reproductive, and immune systems.

RESULTS

A large number of studies were related to exposures from cellular telephones. Although both positive and negative findings were reported in some studies, in a majority of instances no significant health effects were found. Most studies had some methodological limitations. Although some cardiovascular effects due to RFE were reported in epidemiological studies (e.g., lower 24-h heart rate, blunted circadian rhythm of heart rate), there were no major effects on a large number of cardiovascular parameters in laboratory studies of volunteers during exposure to cell-phone RFE. In population-based studies of a wide range of RFE frequencies, findings were equivocal for effects on birth defects, fertility, neuroblastoma in offspring, and reproductive hormones. Some changes in immunoglobulin levels and in peripheral blood lymphocytes were reported in different studies of radar and radio/television-transmission workers. Due to variations in results and difficulties in comparing presumably exposed subjects with controls, however, it is difficult to propose a unifying hypothesis of immune-system effects. Although subjective symptoms may be produced in some sensitive individuals exposed to RFE, there were no straightforward differences in such symptoms between exposed and control subjects in most epidemiological and laboratory studies. Consistent, strong associations were not found for RFE exposure and adverse health effects. The majority of changes relating to each of the diseases or conditions were small and not significant.

CONCLUSIONS

On the basis of previous reviews of older literature and the current review of recent literature, there is only weak evidence for a relationship between RFE and any endpoint studied (related to the topics above), thus providing at present no sufficient foundation for establishing RFE as a health hazard.

Risk of Fetal Exposure to Tricyclic Antidepressants

OBJECTIVES

(1) To review the literature on the risk of fetal exposure to tricyclic antidepressants (TCAs). (2) To estimate the frequency of TCA exposure in pregnant women in the Canadian province of Saskatchewan.

METHODS

MEDLINE was searched for English-language papers published from 1953 to 2003, using the key words "tricyclic antidepressants (TCAs)," "amitriptyline," "amoxapine," "clomipramine," "desipramine," "doxepin," "imipramine," "lofepramine," "maprotiline," "nortriptyline," "protriptyline," and "trimipramine." The search was restricted to human studies. To estimate potential exposure to TCAs during pregnancy, data from the outpatient prescription drug database of Saskatchewan, Canada, were analyzed.

RESULTS

The number of women of reproductive age (16 to 44 years) with at least 1 prescription of genotoxic TCAs was 3501 in 1977, 2959 in 1991, and 1330 in 1999. Corresponding figures for non-genotoxic TCAs were 3403, 4200, and 5493, respectively. Based on these figures, the rates of prescriptions given to women of reproductive age in any particular calendar year were 1.30% (95% confidence interval [CI], 1.25%-1.35%) for genotoxic TCAs, and 2.32% (95% CI, 2.25%-2.39%) for non-genotoxic TCAs.

CONCLUSIONS

Prescription of TCAs to women of reproductive age is quite frequent, and there has been no apparent decline in prescriptions in recent years. The frequent prescription of potentially toxic TCAs to pregnant women may be due to increases in unplanned pregnancies in industrial countries, lack of adequate scientific evidence on the adverse effects of TCAs, and conflicting needs to treat maternal diseases and to protect fetuses. Consultation with specialists experienced in treating depression may be helpful when treating pregnant women with TCAs. Large-scale epidemiologic studies to assess the potential adverse effects of TCAs use in pregnancy on a broad spectrum of fetal and infant outcomes are needed. The findings from such studies will have direct implication on the use of TCAs in the clinical treatment of depression in pregnancy.

Chlorpyrifos (Dursban)-associated birth defects: report of four cases

Extensive and unusual patterns of birth defects noted in four children included defects of the brain, eyes, ears, palate, teeth, heart, feet, nipples, and genitalia. Brain defects were present in the ventricles, corpus callosum, choroid plexus, and septum pellucidum, and genital defects included the testes (undescended), microphallus, and labia (fused). All children had growth retardation, and three had hypotonia and profound mental retardation. The children were exposed in utero to chlorpyrifos (Dursban). Published literature and unpublished documents by the U.S. Environmental Protection Agency contain reports that identify similarities in defects found in test animals and in children exposed to Dursban. A pattern of defects found in the four children in this study may represent a heretofore unrecognized syndrome that should be considered when Dursban-exposed women have children with birth defects.

Fallacies of international and national comparisons of disease occurrence in the epidemiology of neural tube defects

Despite extensive research, little progress has been made in elucidating the etiologies of anencephalus and spina bifida. International and national distributions of disease occurrence have often been used as a basis for generating etiological hypotheses (e.g., potato blight, tea consumption, and zinc deficiency hypotheses). However, few of the epidemiological studies of neural tube defects (NTDs) have been conducted with scientific rigor in design, and most are of dubious validity, often with low precision in the estimates. This paper shows that the accepted geographic patterns of NTDs may be attributable to variations in the validity of studies used to describe these patterns. The nonuniformity in the duration and diligence of case ascertainment, the lack of a standardized nomenclature and classification, and the definition of the denominator remain principal problems in evaluating the epidemiology of NTDs. For example, the distinction between incidence and prevalence is not always made, and there is no consistency in the placement of the gestational boundary between late fetal deaths and spontaneous abortions. Findings are compared from studies conducted at different times, without due regard to the effect of secular trends, and using studies that have varying levels of case ascertainment. In etiological research, it is important to perform studies that are accurate and precise, but the literature used to define the spatial distribution of NTDs has often been accepted without due regard to the effect of these factors.

Timely monthly surveillance of birth prevalence rates of congenital malformations and genetic disorders ascertained by registries or other systematic data bases

In many jurisdictions large data sets on malformations are now collected routinely in order to define prevalence rates of malformations in infants and children, to detect long-term secular trends, and to ascertain cases for ad hoc case-control studies. With slight modifications, these data sets may be used for prompt surveillance of changes in the birth prevalence of malformations, changes that conceivably could be possibly due to the introduction of a teratogen into the environment. A specific logistic approach is suggested, modeled on the New York State Malformation Registry, for prompt detection of changes in rates.

Potential human developmental toxicants and the role of animal testing in their identification and characterization

Some 50 chemicals have been identified from environmental, occupational, or therapeutic exposure data as being potential developmental toxicants in humans. The toxicity pattern of these chemicals in humans has been characterized and correlated with developmental toxicity end points in laboratory animal models in order to determine the relevance and predictiveness of the results of testing in animals in extrapolation to human data. In general, animal developmental toxicity data closely paralleled human outcomes, and while humans in most cases were more sensitive than animals, the data support the concept that, imperfections aside, studies in animals serve a vital role in the hazard identification process.

The effects of severe mixed environmental pollution on human chromosomes

Cytogenetic studies were conducted on healthy young mothers, shortly after child birth, in two residential areas each with an approximate population of 20,000, situated about 25 km from Athens, Greece. One of the areas, Elefsis, is subject to severe mixed industrial pollution, and the other, Koropi, is relatively free of pollution. Chromosomal aberrations were investigated in 16 women from each area in 72 hour lymphocyte cultures treated with gentian violet to enhance any chromosomal instability induced by the pollution. The women were of a comparable socioeconomic level, aged between 20 and 31 years, and with no history of factors associated with mutagenesis. Venous blood samples were taken from the two groups and processed concurrently. The slides were coded and examined independently by two observers, who were unaware of the source of the samples. A total of 100 cells was examined on each sample. The two observers obtained highly comparable results. Women from Elefsis had an average of 0.42 anomalies per cell and those from Koropi had 0.39. The absence of a statistically significant difference between the two groups clearly shows that the severe mixed environmental pollution of Elefsis has no significant visible effect on human chromosomes in most residents. However, two Elefsis women had abnormal results and could be at risk. Their presence is not sufficient to raise significantly their group's average, but the induction by pollution of an increased rate of chromosomal anomalies in only a few people at risk could account for the known association between urban residence and cancer mortality.

General human health risks associated with the use of chemicals

Health risks to man associated with the use of chemicals include carcinogenesis, mutagenesis, and systems damage. Adverse effects from chemical exposures are determined by the nature and amount of the chemical, the type and length of exposure, and individual susceptibility to the chemical. A series of short- or long-term tests have been devised to predict human risk from suspect chemicals. These tests have provided enough information to establish guidelines for human safety, but they are not capable of providing sufficient information for unequivocal, scientifically valid standards for exposure limits. New methods now under development promise to provide more detailed information on early effects and cumulative damage to individuals. Developing countries should use existing data and regulatory experiences to the greatest possible extent to establish exposure limits according to local needs. When more ideal methods for the detection of chemical damage to man are available, these approaches and the data derived from their use can be incorporated into the programs in developing countries.

Aneuploidy and health risk assessment: current status and future directions

The U.S. Environmental Protection Agency (EPA) recently sponsored a workshop to discuss the contribution of aneuploidy to human disease and disability, the development of tests for detecting chemicals that induce aneuploidy and the relevance of these tests to human risk, and the current understanding of mechanisms by which aneuploidy arises. This summary is based on the presentations given at the workshop. It is hoped that this summary will stimulate thinking in this vitally important area of risk assessment and contribute to the establishment of priorities for basic research, development of new test methods, and validation of existing test approaches. Such research is needed to enhance the scientific basis of risk assessment for aneuploidy-producing chemicals.

Cancer and birth defects near the Drake Superfund site, Pennsylvania

The Drake Superfund site in Clinton County, Pennsylvania, has been contaminated with the carcinogens beta-naphthylamine, benzidene, and benzene. The authors reviewed county-wide, age-adjusted, sex-, race-, and site-specific cancer mortality rates for the years 1950-1959, 1960-1969, and 1970-1979, and type-specific birth defects incidence rates for 1973-1978. During the 1970s, a significantly increased number of bladder cancer deaths occurred among white males in Clinton County, and a significantly increased number of other cancer deaths occurred in the general population of Clinton and three surrounding counties. There were no statistically significant clusters of any specific birth defect or of all birth defects. County-wide data on cancer and birth defects can be used for initially screening counties with Superfund sites, but more definitive studies are needed to assess the actual health effects caused by these sites.

Repeated surveillance of exposure to thallium in a population living in the vicinity of a cement plant emitting dust containing thallium

From 1979 to 1981, several medical surveys were carried out among a population living in the vicinity of a cement plant that emitted dust containing thallium until August, 1979. Air, soil, plants, and domestic animals in the area were contaminated by thallium and this led to an increased intake of thallium in the population, mainly due to the consumption of home-grown vegetables and fruit. In order to assess the degree of the individuals' exposure to thallium, thallium levels in 24-h urine samples (TlU) were determined. Three surveys were carried out from September to December, 1979 to assess the degree of thallium exposure of different parts of the general population. Subjects with relatively high exposure, as indicated by the results of the above mentioned population surveys, or those suffering from health disorders that might be related to an increased intake of thallium, were reexamined several times from 1979-1981. Special attention was also given to children attending a kindergarten situated about 0.5 km from the cement plant. As compared to an "unexposed" reference population (mean TlU: 0.3 microgram/l), the majority of the population living in the cement plant area had significantly elevated urinary thallium levels (range: less than 0.1-76.5 micrograms/l) indicating a substantially increased environmental exposure. A reduction of the intake of thallium was mainly achieved by the fact that the population, as advised by the authorities, largely avoided the consumption of home-grown, potentially contaminated foodstuffs. Reports on the teratogenicity of thallium in certain animal species caused great concern that thallium might have exerted teratogenic effects on the newborn of women exposed to thallium during pregnancy. Therefore, an investigation of children born between January, 1978 and August, 1979 (n = 297) was carried out. Although the number of congenital malformations was greater than expected, we conclude, considering carefully all data available, that there is likely no causal relationship between thallium and the occurrence of congenital malformations in the children investigated.