Health of children born to medical radiographers

OBJECTIVES

To develop a reliable method for collecting information on reproductive outcome in an occupational setting; and to investigate the health of children born to medical radiographers.

METHODS

The study population comprised 6730 members of the College of Radiographers who were, at the time of survey; aged between 30 and 64 years, on the current membership file of the College, and were resident in Britain.

RESULTS

The postal method developed proved to be reliable, with around 87% of questionnaires being returned. The observed frequencies of reproductive events were broadly in line with findings from other studies: of the 9208 pregnancies reported, 83% were livebirths, 12% were miscarriages (gestational age < 20 weeks), 1% were stillbirths (gestational age > or = 20 weeks), and 1% were other rarer spontaneous adverse events (ectopic pregnancy, blighted ovum, and hydatidiform mole). There was little difference between men and women in the frequency of adverse reproductive events reported, with the exception that male radiographers reported fewer medical terminations, the proportions being 3.1% and 1.4% for women and men respectively. Among children, the overall risks of major congenital malformation (RR 1.0, 95%CI 0.9-1.2), chromosomal anomaly (RR 1.4, 95%CI 0.8-2.3), and cancer (RR 1.2 95%CI 0.7-2.0) were as expected based on general population rates. Borderline excesses of chromosomal anomalies other than Down's syndrome in the children of female radiographers (RR 3.9, 95%CI 1.3-9.0, based on five observations), and cancer in the children of male radiographers (RR 2.7, 95%CI 0.9-6.5, based on five observations) were noted. The numbers on which these risks are based are small and the findings should be interpreted cautiously.

CONCLUSIONS

The postal methods developed for obtaining information about reproductive events and child health proved to be reliable in men, as well as in women. Overall, the findings for medical radiographers are reassuring. Dose-response relations could not, however, be examined as long term dose records of radiographers are not routinely kept in an accessible form.

Hazards of ionising radiation: 100 years of observations on man

In November 1895, when Conrad Röntgen serendipitously discovered X-rays, epidemiology was effectively limited to the study of infectious disease. What little epidemiological work was done in other fields was done as part of clinical medicine or under the heading of geographical pathology. The risks from exposure to X-rays and subsequently from other types of ionising radiation were consequently discovered by qualitative association or animal experiment. They did not begin to be quantified in humans until half a century later, when epidemiology emerged as a scientific discipline capable of quantifying risks of non-infectious disease and the scientific world was alerted to the need for assessing the effects of the radiation to which large populations might be exposed by the use of nuclear energy in peace and war.

Birth prevalence of congenital malformations in Bavaria, Germany, after the Chernobyl accident

This study considers whether or not exposure to radioactive fallout from the Chernobyl accident led to an increased prevalence of congenital malformations in infants born in Bavaria, the German state with the highest levels of contamination after the accident. The odds ratios for major malformations after the accident relative to before were used as indicators for adverse health effects. Since measurements of caesium in soil showed that contamination was considerably higher in Southern Bavaria than in Northern Bavaria, the odds ratios were calculated for both regions separately. Analysis did not show a significant increase in any of the odds ratios of the selected malformations in Southern Bavaria as compared to Northern Bavaria. Consequently, this study provides no evidence that radiation from Chernobyl caused an increase in the birth prevalence of major congenital malformations.

Electric blanket use during pregnancy in relation to the risk of congenital urinary tract anomalies among women with a history of subfertility

To study the potential effect of prenatal exposure to electromagnetic fields on the occurrence of cogenital urinary tract anomalies (CUTAs) in offspring, we conducted a case-control study in western Washington State. CUTA cases without known chromosomal abnormalities were identified from the Washington Birth Defects Registry. Controls without birth defects were randomly selected from among infants born in five large hospitals in King County, WA. Mothers of cases and controls were interviewed to obtain information on prenatal use of electric blankets, electrically heated water beds, and video display terminals. After adjustment for potential confounders, the risk of CUTAs was found not to be materially associated with these prenatal exposures among all subjects. Among women with a history of subfertility, however, prenatal use of electric blankets was associated with a more than four-fold increase in the risk of CUTAs [adjusted odds ratio (OR) = 4.4; 95% confidence interval (CI) = 0.9-22.7]. The risk was greater if the exposure occurred during the first trimester (adjusted OR = 10.0; 95% CI = 1.2-85.5). The risk also appeared to increase with increasing duration of electric blanket use. Despite small numbers and the potential for recall bias, our study indicates that identifying a susceptible population may be required for detecting adverse reproductive effects of electromagnetic fields.

[The genetic consequences of the Chernobyl accident. The monitoring of congenital developmental defects in newborn infants in Kaluga Province]

The study concentrates on the genetic after-effects of the Chernobyl accident in some districts of Kaluga Province. The frequencies and range of congenital malformations, prematurely death-rate in the radionuclear polluted districts were compared with the control districts. Prematurely death-rate in compared regions is the same. The increase of the congenital malformation frequency is revealed in one the polluted districts (256/10,000) as compared with the control one (27/10,000). We assume that the observed effect is mainly connected with the professional activity of the population.

French Polynesia: a nuclear paradise in the Pacific

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Selective monitoring for a Chernobyl effect on pregnancy outcome in Kiev, 1969-1989

The aim of this investigation was to determine the frequency of adverse pregnancy outcomes in Kiev during the period surrounding the Chernobyl accident on April 26, 1986. Additional effective equivalent doses resulting from the catastrophic irradiation in 1986-1991 was 8.04 mSv for Kiev inhabitants. We retrospectively analyzed the archives of the two largest obstetric hospitals between 1969 and 1990. Spontaneous miscarriages, congenital anomalies, and perinatal mortality varied during the two decades without any pronounced changes in any direction. Additional long-term follow-up is needed to determine mutagenic or carcinogenic effects.

[Incidence of developmental defects in human embryos in the territory of Byelarus after the accident at the Chernobyl nuclear power station]

The incidence of developmental abnormalities (DA) among 5 to 12-week human embryos collected in Minsk during abortions before the Chernobyl' accident was compared to that in Minsk, Mogilev, and southeastern districts of Gomel' and Mogilev regions before and after the accident. The incidence of DA among human embryos from the most radionuclide-contaminated rural regions of Byelarus exceeds that of the control group and of the urban population after the Chernobyl' accident by a factor of 1.5-2. The mutagenic effect of irradiation is the most probable cause of the increased DA frequency. These data suggest that recording of DA in embryos obtained by medical abortions is a new promising approach to the monitoring of genetic consequences of irradiation in human populations.

Ionizing radiation and genetic risks. V. Multifactorial diseases: a review of epidemiological and genetic aspects of congenital abnormalities in man and of models on maintenance of quantitative traits in populations

This paper discusses (a) data on the epidemiological and etiological aspects of human congenital abnormalities, (b) the multifactorial threshold model and other models which have been proposed to explain their inheritance patterns and recurrence risks in families and (c) current concepts on mechanisms on the prevalence of heritable variation for quantitative traits in populations. Congenital abnormalities, which afflict an estimated 6% of all live births, are etiologically heterogeneous. The majority of these do not follow Mendelian transmission patterns, but do 'run' in families. The multifactorial threshold model is an extension of genetic principles developed for quantitative traits to all-or-none traits; in its simplest formulation, it assumes the existence in the population of an underlying normally distributed 'liability' (which is due to numerous genetic and environmental factors acting additively, each contributing a small amount of liability) and of a 'threshold' beyond which the individual is affected. For most congenital abnormalities, the nature of these factors remains unknown. Other models assume fewer causal factors although, again, these remain to be identified. The question of how considerable heritable variation for most quantitative/polygenic traits has come to exist is a long-standing one in evolutionary population genetics. Models postulating that its existence is consistent with a balance between recurrent mutation and stabilizing selection or suggesting the possible operation of other mechanisms have been published in the literature. In the absence of knowledge on mechanisms responsible for the stable prevalences of congenital abnormalities or other multifactorial conditions in the population (but which is required to predict the consequences of an increase in mutation rate on their prevalences) it is necessary (a) to adapt and use concepts derived from quantitative and evolutionary population genetics and (b) to examine how sensitive the predictions are to the assumptions used, and how consistent they are with biological realities.

[Fertility after cytostatic treatments]

Antimitotic chemotherapy and radiation therapy can induce temporary or permanent infertility in men, transitory amenorrhea or premature ovarian failure in women, and genetic mutations responsible of fetal deaths or congenital malformations in the progeny. Alkylating agents and radiotherapy can provoke definitive male infertility and ovarian failure, but individual susceptibility seems quite variable. In man, return of spermatogenesis can still be observed more than 10 years after treatment and pregnancies are obtained with very low sperm counts. In women, the progressive depletion of the follicular pool explains the increasing frequency of ovarian failure, with lower doses of treatment. Antimitotic and immunosuppressive therapy can also induce irreversible lesions in children's gonads.

[The clinical and cytogenetic characteristics of the children born to persons with a history of 1st- and 2d-degree acute radiation sickness as a result of the accident at the Chernobyl Atomic Electric Power Station]

We have examined 15 children (born in 1987-1988), whose fathers liquidated the aftereffects of the accident at Chernobyl Nuclear Power Plant and suffered from acute radiation sickness of the 1st and 2nd stages and 50 children of the control group. The obtained data showed that the number of small developmental abnormalities (stigmas of dysembryogenesis) increased as well as the chromatid aberration frequency as compared with the control group.

[Limited genetic monitoring in Kiev in relation to the accident at the Chernobyl Atomic Electric Power Station]

Frequency of innate developmental defects, perinatal death rate, spontaneous and induced abortions were statistically studied on the basis of primary medical information from archives of two largest maternity hospitals of Kiev for the period between 1969 and 1989. Significant variations in the chosen characters in different years were found, unidirectional changes in time being absent. No increase in the number of innate defects and frequency of spontaneous abortions after 1986 was found. It is shown necessary to introduce a system of unified registration of innate developmental defects adopted by an international register as well as to use more perfect mathematical methods for correct estimation of the processes occurring in human populations.

[The immediate and late results of radiation effects on the occurrence of congenital defects in the locomotor apparatus based on screening data on newborns in the maternity hospitals of the city of Kiev]

On the basis of screening of 15939 newborns at the maternity homes of Kiev after the accident at the Chernobyl atomic station it was found that the number of children with congenital malformation of the locomotor apparatus in 1991-1992 increased by 28.7% as compared with the data of the first postaccident years (1986-1987). Congenital pathology of the hip joint (dysplasia in average 23.5 per 1000 births, hip dislocation 3.6:1000) and foot deformity (7.9:1000) had the highest incidence with a tendency to increase at the latest years.

Birth defects and high voltage power lines: an exploratory study based on registry data

This is an exploratory study on birth defects in municipalities through which overhead high voltage power lines (HVPL) pass. It was aimed to test the association between maternal residencial proximity to HVPL and congenital anomalies through a case-control study based on data from the Central-East France Registry of Congenital Malformations. Each of the 1688 malformed infants identified through the register was matched with two randomly selected controls in the same maternal age group of the general population. No excess of any specific type of malformation was observed in infants exposed to HVPL. An inverse association was even found between maternal residence in municipalities with potentially high exposure to electromagnetic fields from overhead power lines and congenital anomalies of all types. This was accounted for by low numbers of exposed infants with two types of malformations: skeletal defects and cardiac defects. Difficulties in interpretation of data are addressed and limitations of the study are discussed. If an inverse association were upheld in further work, a possible mechanism might be that exposure to electromagnetic fields may increase the risk of spontaneous abortion of fetuses with anomalies.

Measured dose to ovaries and testes from Hodgkin's fields and determination of genetically significant dose

PURPOSE

To determine the genetically significant dose from therapeutic radiation exposure with Hodgkin's fields by estimating the doses to ovaries and testes.

MATERIALS AND METHODS

Phantom measurements were performed to verify estimated doses to ovaries and testes from Hodgkin's fields. Thermoluminescent LiF dosimeters (TLD-100) of 1 x 3 x 3 mm3 dimensions were embedded in phantoms and exposed to standard mantle and paraaortic fields using Co-60, 4 MV, 6 MV, and 10 MV photon beams.

RESULTS

Our results show that measured doses to ovaries and testes are about two to five times higher than the corresponding graphically estimated doses for Co-60 and 4 MVX photon beams as depicted in ICRP publication 44. In addition, the measured doses to ovaries and testes are about 30% to 65% lower for 10 MV photon beams than for their corresponding Co-60 photon beams.

CONCLUSION

The genetically significant dose from Hodgkin's treatment (less than 0.01 mSv) adds about 4% to the genetically significant dose contribution to medical procedures and adds less than 1% to the genetically significant dose from all sources. Therefore, the consequence to society is considered to be very small. The consequences for the individual patient are, likewise, small.

[Analysis of congenital malformations in newborns]

We analyzed data from 194 newborns with congenital malformations of central nervous, cardiovascular, gastro-intestinal, skeletal, genito-urinary systems and Down's syndrome. We detected that the highest frequency of congenital malformations occurred from may 1986 to december 1986. Congenital malformations were detected more frequently in female newborns and newborns delivered by multipara. The percentage of CNS malformations was constant but at the same time the number of other malformations were significantly changed. We made an attempt of statistical analysis of frequency and type of malformations taking into consideration possible influence of radiation during analyzed period.

Birth defects in Norway by levels of external and food-based exposure to radiation from Chernobyl

In Norway, external doses of radiation resulting from fallout from the Chernobyl nuclear accident were estimated from detailed measurements, including soil deposition patterns. Internal doses were estimated from measurements of radioactive cesium in meat and milk supplies. The doses were calculated as average monthly doses for each of 454 municipalities during 36 consecutive months after the accident in spring 1986. Prospectively collected data on all newborns listed in the Medical Birth Registry of Norway who were conceived in the period May 1983-April 1989 were used to assess possible dose-response relations between estimated external and food-based exposures and congenital malformations and some other conditions. A positive association was observed between total radiation dose (external plus food-based) and hydrocephaly, while a negative association was observed for Down's syndrome. However, an important conclusion of the study was that no associations were found for conditions previously reported to be associated with radiation, i.e., small head circumference, congenital cataracts, anencephaly, spina bifida, and low birth weight. Potential sources of bias, including exposure misclassification and incomplete ascertainment of cases, are discussed.

1992 assessment of radiation risk from dental radiography

Recent studies suggest that the lifetime cancer risks from exposure to low levels of ionizing radiation may be greater than previously estimated. This review first summarizes the findings of these studies as they pertain to dental radiology, then uses their concepts in combination with dosimetry from the dental literature to estimate the radiation risk from dental radiology. Estimation of risk from groups of exposed individuals requires use of mathematical models that fit the epidemiological data. The ICRP estimates that a single brief whole-body exposure of 1 Gy to 10,000 people results in about 500 additional cancer deaths over the lifetime of the exposed individuals, assuming a dose rate effectiveness factor of 2 for cancers other than leukaemia. Leukaemias are seen as a wave from 5 to 30 years following exposure. Cancers other than leukaemia typically start to appear about 10 years following exposure and remain in excess for as long as most exposed populations are followed, presumably for the lifetime of the exposed individuals. The gonadal dose is so small from dental radiography that the risk of heritable defects is negligible in comparison with the somatic risk. The dental literature contains several studies reporting sufficient dosimetric data for radiosensitive sites in the head and neck to allow estimation of the risk of fatal cancers from intra-oral and panoramic radiography. The highest estimated risks (using the ICRP data) are for leukaemia (bone marrow), thyroid and bone surface cancer. The total risk is estimated to be 2.5 fatal malignancies per 10(6) full-mouth examinations made with D-speed film and round collimation.(ABSTRACT TRUNCATED AT 250 WORDS)

[Genetic monitoring in connection with the Chernobyl accident]

The complex investigation has been provided to control the genetically influenced processes after Chernobyl accident in some Ukrainian regions. Some dangerous trends in genetic populational status were revealed in the Ukrainian regions surrounding Chernobyl power plant allowing for the increasing number of congenital anomalies among the newborns and the spontaneous abortions as well as higher proportion in aberrations of chromosome type in human somatic and embryos cells, higher incidence of structural defects in embryonal bone system and higher, compared with control, proportion of children with intensive catabolism (R-protein homeostasis).

Congenital malformations and exposure to high-frequency electromagnetic radiation among Danish physiotherapists

A cluster initiated the present case-referent study to assess the relation between exposure to high-frequency electromagnetic radiation and congenital malformations. Through the linkage of a cohort formed from a union file of Danish physiotherapists with complete national registers of pregnancy outcome, cases (pregnancies terminated by the birth of a malformed child) and referents were identified. From responses in a blinded telephone interview without knowledge of case status, exposure to high-frequency electromagnetic radiation in the first month of pregnancy was assessed. Indices reflecting duration of exposure ("time") and maximum level of exposure ("peak") were composed. After a 7% dropout 54 cases and 247 referents were interviewed. No statistically significant associations between pregnancy outcome and high-frequency electromagnetic radiation were found (odds ratio 1.7, 95% confidence interval 0.6-4.3).

The evaluation of the germinal mutagenic impact of Chernobyl radiological contamination in Hungary

The genetic consequences of radioactive fall-out deposition from the Chernobyl (USSR) accident in Hungary was evaluated as a part of the ongoing programme on the population-based Hungarian Surveillance of Germinal Mutations. The surveillance is based on three groups of indicator conditions: 15 sentinel anomalies (indicators of germinal dominant gene mutations), Down's syndrome (an indicator of germinal numerical and structural chromosomal mutations) and unidentified multiple congenital abnormalities (indicators of germinal dominant gene and chromosomal mutations). Cases with these indicator conditions were selected from the material of the Hungarian Congenital Abnormality Registry. After the diagnostic accuracies were checked, familial and sporadic cases were separated. Only the latter group was evaluated for evidence of new mutations. The analysis did not reveal any measurable germinal mutagenic effects of the Chernobyl accident. Furthermore, there were no significant differences in the rates of these three groups of indicator conditions between regions with higher and lower increased background radiation.