Determination of infant mortality and morbidity in the population of Ukraine affected by the CHNPP accident

N. Omelyanets, N. Dubovaya, S. Kartashova, N. Gunko, S. Omelyanets, V. Buzunov, R. Pott-Born

Research Centre for Radiation Medicine

53, Melnikov St, Kiev, 04050, Ukraine

Tel. 38 (044) 431-98-33, Fax. 38 (044) 213-72-02, E-mail: omelyan@rcrm.kiev.ua

Abstract: I n the post-accidental period, especially after 1990, the medico-demographic situation has considerably worsened: the population is decreasing on account of a decrease of the birth rate and the increase of general mortality. Infant mortality and stillbirth rates are mostly decreasing, but stay at high levels, especially on the radioactively contaminated territories (RCT). The socio-economic changes after 1990 and the significant decrease in living standards promoted the worsening of the medico-demographic indices. Thus the birth rate significantly decreased in all RCT and infant mortality remained at mean levels of 10-15 (range 5-25) % 0. Infant mortality increased in some contaminated raions, especially in Narodichi and Polesskoe raions on account of mortality in the neonatal period. Postneonatal mortality appeared unchanged. stillbirth rate decreased in all raions of the study. The main causes of infant deaths were certain conditions originating in the perinatal period, congenital anomalies and diseases of the respiratory system. The main causes of early neonatal mortality were the syndrome of respiratory distress (more than 33%), congenital anomalies (about 25%), birth trauma (up to 13%), intrauterine hypoxia and asphyxia in childbirth (5%). The results were analyzed in relation to the contamination levels by 137 Cs, the average individual thyroid doses, whole body and collective doses of the population of the raions and the time period before and after the accident. There is not found a correlation of the indices of infant mortality with the received radiation doses of the thyroid gland in 1986 and with the collective radiation dose of the population in the radioactively contaminated oblasts and raions. The correlation of the indices with mean individual radiation doses is in single instances significant. The risk analysis show that RR for neonatal mortality is significant in the contaminated in comparison to the control raions, but there is no increased risk for infant mortality when comparing the pre-accidental with the post-accidental time.

1. INTRODUCTION

In Ukraine, the western part of the former USSR, the explosion of the block No. 4 of the Chernobyl nuclear power plant (ChNPP) on April 26, 1986 led to the release of about 100 millions Ci of radioactively nuclides into the atmosphere. Vast areas in the three adjacent countries, Belarus, Ukraine and the Russian Federation, and also great parts of Western Europe were contaminated [1, 2 ]. Millions of people were exposed to increased radioactive contamination. Isotopes of radioiodine ( 131, 132, 133, 134I), caesium ( 134, 136, 137Cs), strontium ( 89, 90Sr) and plutonium ( 238, 239, 240, 241Pu) were the most dangerous from biological point of view. These isotopes are beta- and alpha-emitters and led to external and internal exposures of the population. During the first months after the accident there were high exposures of the thyroid gland (especially of children) by radioiodine. The soils of a territory of about 145 thousand km 2 were contaminated by radio-caesium with more than 37 kBq/m 2 (1 Ci/km 2). In the contaminated territories about people live in 2,2 million in Ukraine.

There are Ukrainian studies about health deterioration of the victims of the accident [3-6]. Between 1986 and 2000 in Ukraine there were about 1400 verified cases of thyroid cancer registered among those, who were children at the time of the accident [7] . This pathology is clearly a consequence of the thyroid exposure by radioiodine [8-10].

Numerous other scientific studies concerning the Chernobyl accident aftermath have been conducted in the affected republics of the former USSR. Some studies have never been published; others gave incoherent, incomplete, and even contradictory results regarding the ecological and medical significance of the catastrophe of April 26, 1986.

The goal of the project 3.3.1 “Determination of infant mortality and morbidity in the population of Ukraine affected by the ChNPP accident”, a subproject of the French-German Initiative for Investigation of Health Effects after the Chernobyl Accident, was the collection and analysis of the data on infant mortality and morbidity of exposed children in the highly contaminated regions of Ukraine in comparison to the low or uncontaminated regions before and after the accident.

2. MATERIALS AND METHODS

Object of investigation was the population of Zhitomir and Kiev oblasts with their five most highly radioactively contaminated raions, the non-radioactively contaminated Poltava oblast with five raions and Ukraine as a whole.

Zhitomir and Kiev oblasts are the most radioactively contaminated of the 12 oblasts of Ukraine. The major part of the exclusion zone with the destroyed nuclear reactor and more than 800 temporary storehouses of radioactive waste, which were formed during liquidation of the consequences of the accident is situated in Kiev oblast. In 1986 91,2 thousand people were evacuated from the 30-km zone and districts considered as raions of strong radiation control were established. In their territories live 1,45 million people. These are 75,6 thousand liquidators and 0,94 million victims with 0,44 million children. Almost 2/3 evacuees were resettled in regions of their oblasts and even raions. In Luginy, Narodichi and Ovruch raions of Zhitomir oblast, Polesskoe and Ivankov raions of the Kiev oblast the majority of inhabitants required resettlement, for some for a second time, because their life span dose would exceed 350 mSv. In 1991-1992 inhabitants of these raions were subjected to resettlement. Up to now this resettlement is not completed, however [7]. Most inhabitants, who need resettlement, live in Zhitomir oblast. Within the boarders of these oblasts there are different zones of radioactively contamination, which were established by the national legislation in 1991, when lifespan dose was limited to 70 mSv. The population of these oblasts has both the highest thyroid doses and the highest average individual and collective doses. Therefore these two oblasts are selected for the study in the present research . The most radioactively contaminated raions were selected: from Zhitomir oblast: Luginy, Narodichi and Ovruch raions, from Kiev oblast: Ivankov and Polesskoe raions.

As the control population served 5 raions from the radioactively clean oblast Poltava.

In life statistics infant mortality is divided in several age groups from which we selected: prenatal age (stillbirths), stillborn and newborn in the age 0-6 days (perinatal mortality), newborns in the age of 0-6 days (early neonatal mortality), newborns in the age of 0-27 days (neonatal mortality), newborns in the age of 7-27 days (late neonatal mortality), newborns in the age 28-365 days (postneonatal mortality), infants in the age till 1 year (infant mortality) differentiated by gender.

The study of radioecology and calculation of the doses was based on the collection and usage of sources containing all relevant data to the contamination in the raions and oblasts of the study. The information sources were data’s of: Minsdrav of Ukraine, Goskomgidromet of the USSR [11], thyreodosimetric and dosimetric passportisation of the settlements of Ukraine which were radioactively contaminated (they include information about the soil contamination of the settlements, the contamination of milk and potatoes by radionuclides of caesium and about the size of the thyroid and passport dose [12-18]), maps [2, 19], sanitary-epidemiological stations of investigated oblasts and raions, publications about of irradiation doses [20]. Estimation of radioecology in the selected territories carried out on soil contamination by 137Cs, 90Sr and 239Pt.

Three groups of irradiation doses were calculated: the individual irradiation doses of parents and infants, the average individual doses of the population on the administrative territories (raions), the collective doses of the population.

For calculation of the average individual irradiation dose of the population of each contaminated raion average individual irradiation doses of each age group were summarized and the sum divided by the number of inhabitants of this raion. Average and medians doses were calculated. The thyroid irradiation doses are submitted as mean individual doses for seven age groups. This distribution by age is made by experts, which carried out the dose reconstruction, using the data of radioiodine absorption by thyroid gland (TG) taking into account its weight in relation to the body weight.

The collective doses (CD) of the population of the selected raions were calculated using the individual average doses and the average annual number of the population.

Average individual irradiation doses of the inhabitants, of the children born before the accident, and of infants born after the accident was calculated. These doses were implemented into the “Protocol of verification of the causes of death or stillbirth” at the process of data verification. The irradiation dose of a fetus corresponds to the dose of the mother during pregnancy (in 1986). If the pregnancy was after 1986, for the deceased or stillborn infant only irradiation doses of the mother and father were taken into account depending on the age of the child at the moment of the accident.

The following socio-economic indices were taken which constitute the life standard of the population of the country: real gross domestic product (GDP); industrial production; agricultural production; index of inflation; employment of the population; retail circulation of goods; consumption of the basic food products (meat, milk, eggs, sugar, oil, vegetables, potatoes, bread); cost of a set from 22 major food products in cooperative and state trade; average wages of the workers and employees; cost of household services; number of pupils; availability of habitation; introduction of apartment houses; of pre-school institutions; of hospitals; and of out-patient facilities – ambulance institutions; quantity of beds in the hospital; the throughput of out-patient-ambulance institutions; availability of doctors; availability of the middle medical personnel.

The following indices were calculated for both sexes separately: number and age structure of the population by gender (form “ Number of the constant population by sex and separate age groups on January 1 of year____”), t otal mortality of the population by sex and causes, per 1,000 (form No. S-8), n umber of child births (form No. А-1), b irth rate, per 1,000 (form No. A-1), n umber of newborn children (form No. А-1), s ex ratio of the newborn children, number of stillborn (form No. А-1), s tillbirth by sex and causes, per 1,000 (form No. А-05), n umber of diseased infants at the age of 0-6 days (form No. А-05), n umber of diseased infants at the age of 0-27 days (form No. S-8), n umber of diseased infants at the age until 1 year (forms No. А-1, S-8), e arly neonatal mortality by sex and causes, per 1,000 (form No. А-05), l ast neonatal mortality by sex and causes, per 1,000 (form No. А-05), p erinatal mortality by sex and causes, per 1,000 (form No. А-05), p ostneonatal mortality by sex and causes, per 1,000 (form No. А-05), i nfant mortality by sex and causes, per 1,000 (form No. A-1, S-8), i nfant morbidity by causes, per 1,000 (form No. 12).

The following methods of statistic were applied for data analysis: calculation of rates, means and standard errors; t-statistics and c 2 ; regression analysis and calculation of relative risks (RR); analysis of the structure of the causes of infant mortality and morbidity. The hypothesis concerning possible dependencies between indices of infant mortality in the post-accidental period and the radioactively contamination of soils by 137Cs was checked by the non-parametrical correlation analysis estimating Spearman’s correlation factors.

The RR of infant mortality and its components was calculated comparing the indices of the RCT with those of the pre-accidental period (1981-1985) and with the group of control raions of the Poltava oblast.

Calculation of RR was carried out both for the post-accidental period and for the five-year intervals. The value of RR is telling the significance of the connection between the influence of a risk factor (here the radiation exposure of the population by the Chernobyl accident) and cases of infant deaths on the contaminated territories. With increasing value of RR (>1,0), increases the probability of an etiologic connection. Statistical significance was estimated by small value of p criterion of χ 2 (< 0,05) and confidence limits of ratio, which do not include 1,0.

3. RESULTS

3.1 Socio-economic conditions of life

From 1985 till 1989-1990 mainly positive tendencies were observed in the economic development of the country. But since 1990 levels of real gross domestic product (GDP), products of industry and agriculture began to decrease. The annual rates of decrease of the indices were roughly 2%. The decrease of indices as commissioning of habitation and number of employed people started even earlier [21].

The greatest influence on the demographic indices as mortality, birthrate or infant mortality is exerted by various socio-economic factors, as for instance the GDP in fig. 1. The increasing collective irradiation dose might as well contribute to the adverse changes of the demographic indices.

The analysis expectancy of life of the population of Zhitomir and Kiev oblasts, and also of five of the most radioactively contaminated raions ( Luginy , Narodichi, Ovruch, Ivankov, Polesskoe) 5 years prior to the accident and for the whole period after the accident results in a slightly greater decrease expectancy of life in comparison to the control raions of the study. During the period 1986-2000 it was reduced by 4,2% in the contaminated raions, by 2,8-3,0% in radioactively contaminated oblasts, by 3,6% in control oblast and by 2,7% in Ukraine, compared to the level in 1981-1985.

* – GDP – in percentage by 1985;

** – CD – in thousands pers.-Sv.

Figure 1. Demographic indices in connection with GDP and collective dose of the population of Ukraine from 1981 to 2000

3.2. Infant mortality

The data of fig. 2 show, that before the accident (1981-1985) infant mortality in investigated oblasts fluctuated within the limits of 12,1-17,2‰ live births children. During the whole period 1986-2000 there was a general reduction of infant mortality. In 2000 the rate in radioactively contaminated oblasts was 9,02-10,3‰ and was thus lower than in Ukraine as a whole (11,9‰). Besides the general tendency for a decrease in Zhitomir and Kiev oblasts there was registered an increase of infant mortality in 1987 and from 1990 to 1994 in the Zhitomir oblast and from 1990 to 1993 in the Kiev oblast. The highest indices of infant mortality were observed in the Zhitomir oblast.

Figure 2. Infant mortality dynamics in the oblasts and in Ukraine as a whole from 1981 to 2000 ( per 1,000 live births)

In the contaminated raions of the Zhitomir and Kiev oblasts (fig. 3) in the pre-accidental period infant mortality was 13,4 per 1,000 live births children and was thus lower, than in the control oblast Poltava, where 17,6‰ was registered. In the period after the accident (1986 to 2000) an increase or stagnation of infant mortality at elevated levels was observed in the contaminated raions. The highest indices of infant mortality were in the Narodichi and Polesskoe raions.

The data show that the main reason for the decrease of infant mortality rates is the high level in the pre-accidental time. In the contaminated raions a clear tendency for increase of the rates is observed.

In the structure of infant mortality both till, and after the accident certain conditions originating in the perinatal period and congenital anomalies were the main endogenic causes. The exogenic causes of infant death – infectious and parasitic diseases, diseases of the respiratory organs, traumas and poisonings were about 25% from all cases of death. After the accident the decrease of infant mortality basically was due to the reduction of causes of death by exogenic causes.

In the radioactively contaminated raions the level of infant mortality from certain conditions originating in the perinatal period for 1986-1994 has increased 3 times and was 4,0±0,5‰ (in 1981-1985 this index corresponded to 1,3±0,3‰). In the period 1995-2000 this index decreased to 2,5±0,5. In the control raion Lokhvytsia there was a steady decrease of this index from 4,36‰ in 1986 to 2,19‰ in 2000.

Figure 3. Infant mortality dynamics in the radioactively contaminated and control raions from 1981 to 2000 (per 1,000 live births)

The second place in the structure of the causes of infant mortality was occupied by congenital anomalies. All cases of ICD 9 codes from 740 to 759 were included. In Ukraine the indices fluctuated between 3,5 and 4,3‰. The level with 3,94±0,04‰ in 1986-1990 has decreased to 3,69±0,15‰ in 1991-1995.

In 1996-2000 the level of infant mortality was 4,34±0,19‰. The contaminated Zhitomir oblast showed indices of congenital malformation between 2,2 and 4,6‰, the highest value being observed in 1987 and the lowest one in 1999. In the control Poltava oblast the indices are slightly lower over the whole observation period. In the raions there are great fluctuations in the size of the indices, which does not allow any conclusions. The mean values over the whole period are 1,8±1,2‰ for the contaminated raions and 2,8±1,2‰ for the control raions. The highest value of the contaminated raions (4,6‰) was registered in 1987. But also in the control raions the index was elevated in 1987 (4,2‰). The highest value of the control raions was registered in 1994 (5,1‰). In the contaminated raions in the pre-accidental period the index was 2,85±0,16‰. In the control it was 3,68±0,47‰. During the period of the study (1986-2000) a general decrease of infant mortality from congenital anomalies was registered. So, if in 1986-1990 its level was 2,0±0,81‰, in 1996-2000 – it was 1,43±0,45‰ (in control raions accordingly 2,93±0,6‰ and 1,77±0,25‰). In control raions the indices of congenital malformations are in the postaccidental period significantly (t =-2,67, p < 0,01) higher than in contaminated raions.

The infant mortality from diseases of respiratory organs, which is the third most widespread cause of death of children in the age > 1 year, in the post-accident period also considerably decreased, especially in 1997-2000. The index of these diseases in the radioactively contaminated raions was 0,52 per 1,000 newborns (in 1981-1985 it was 3,73‰), whereas in control raions it was 0,98 per 1,000 of newborns (in 1981-1985 it was 4,7‰).

3.3. Stillbirth

The stillbirth in oblasts and in the country as a whole tended to decrease. Also in the radioactively contaminated and in the control raions there is a decrease observed over the whole study period. In the contaminated raions the stillbirth rate was even less, than in the control raions.

In more than 60% of the stillbirth cases the fetus died at childbirth. The basic cause was intrauterine hypoxia and asphyxia. On the second place of the causes of stillbirth were congenital anomalies. The syndrome of respiratory disorder occupied the third place. In the radioactively contaminated oblasts the stillbirth rate by congenital anomalies decreased from 1985 to 1996 1,3-1,6 times (in the Poltava oblast 2,5 times), by intrauterine hypoxia and asphyxia during childbirth 1,2 times, by respiratory distress 1,8 times and by birth trauma 1,5-2,4 times. The reason of the decrease of the stillbirth death by congenital anomalies is the deterioration of the quality of diagnostics of this pathology.

3.4. Perinatal mortality

The perinatal period is considered in Ukraine as the time from the 28 th week of pregnancy till the completion of the 7 th day of life of a newborn. Perinatal mortality thus consists of the early neonatal mortality and the stillbirth rate.

The perinatal mortality in Ukraine has decreased from 15,1‰ in 1981 to 10,1‰ in 2000 that is 1,5 times. Such tendencies were marked both in the radioactively contaminated and control oblasts.

The dynamics of perinatal mortality in the radioactively contaminated raions does not show the general decrease of the indices seen in the oblasts, especially in the raions of the Zhitomir oblast. The two raions of the Kiev oblast show in the contrary to the first oblast very high indices in 1987. In the control raions of the Poltava oblast are no values standing out, but are slightly higher in comparison to the contaminated raions. In both groups of raions, where it is clearly seen, that the control raions have the tendency for higher values.

The positive changes in dynamics of perinatal mortality were caused, mainly on account of the decrease of stillbirth rate in the radioactively contaminated and in the control raions. In both groups of raions the share of the stillbirth rate is higher than the share of early neonatal mortality. Whereas in the contaminated raions this difference is small, in the control raions the stillbirth rate was partly over 80% of the perinatal mortality. Early neonatal mortality shows mean indices of the whole period of 4‰ in both groups of raions. The mean stillbirth rate is in the control raions 13,1 and in the contaminated raions 10,6‰.

In investigated territories (both groups of raions) in the perinatal period about 33% of children perish from respiratory distress-syndrome, 41% – from hypoxia and asphyxia of a fetus and 23% – from congenital anomalies.

3.5. Neonatal mortality

The neonatal mortality of children occurs in the period from the moment of birth until the 28 th day of life. In the structure of neonatal mortality early (0-6 days) and late (7-28 days) neonatal mortality are enclosed. Within the first months and there in the first week of life is the risk of death for a newborn child especially high. The least viable children die mainly from pathologies of so-called endogenic causes as there are certain conditions originating in the perinatal period and congenital anomalies.

Dynamics of the neonatal mortality in the investigated raions are shown in fig. 4. The indices of neonatal mortality were not different in the control or contaminated raions. The exception is the year 1990, where the contaminated raions have an index of 9,2‰ and the control raions of 3,9‰.

Figure 4. Neonatal mortality dynamics in investigated raions from 1981 to 2000 (per 1,000 live births)

The level of early neonatal mortality considerably increased in 1986-1990 in comparison to the pre-accidental time (2,4 times), it increased also in the control raions (1,2 times), but this increase was not statistically significant (p > 0,05).

The respiratory distress syndrome occupies the first place in the structure of the causes (more than 33%). They were followed by congenital anomalies (about 25%), birth trauma (up to 13%) as well as intrauterine hypoxia and asphyxia during childbirth (5%). In 1986-1996 in most investigated territories the level of these causes was reduced. The exception was the oblast Zhitomir, where an increase of infant losses from certain conditions originating in the perinatal period was observed.

Late neonatal mortality did not show remarkable changes in the different periods on the level of the oblast and the Ukraine as a whole. The control raions show higher indices in the pre-accidental time than the contaminated raions (1,4 and 0,7 ‰), but in the last period (1996-2000) the level of late neonatal mortality was quite similar: 1,9 ‰.

3.6. Postneonatal mortality

In 1981-1985 the postneonatal mortality in Ukraine was 8,7‰. There was a steady decrease of the index to 6,2‰ in the last period. A similar process is observed in the oblasts, there is a decrease from 7-9‰ to 5,2-6,3‰. Quite different is the result in the contaminated raions. Figure 3.33 shows, that the indices are higher than in the oblasts and there are no decrease registered. Also the values in the contaminated raions are on the average slightly higher than in the control raions (8,8 and 7,7‰). Only in the pre-accidental period postneonatal mortality in the contaminated raions was 10,8‰ and in the control raions 13,0‰ accordingly.

3.7. Verification of the causes of infant deaths

During verification of the causes of death of the infants data about the place of death (in medical institution, at home) are collected. The information is received from the medical documents (History of childbirth, History of development of the child, Medical card of the outpatient patient, Case Record) and medical certificates about death. The data of these documents are transferred to the “Protocol of verification of the cause of death of the infant” for each child.

The analysis of the data confirms that the majority of the infant deaths occur in medical institutions.

In total in the three oblasts of the study during 12 years the causes of death of1728 infants were verified. 1727 died infants had data on autopsy. In the Zhitomir oblast 100% of the stillborn and deceased infants in the age till 1 year were subjected to autopsy. In Kiev oblast the share of autopsies was 99,7%. In the control oblast Poltava the share of the autopsies of infants was 100%. The clinical diagnoses of the causes of death are confirmed pathologo-anatomically with practically no differences.

3.8. Infant morbidity in various regions and periods of study

Data about infant morbidity in vital statistics of Ukraine on oblasts level are available only since 1991, and on raion level since 1994. The analysis of infant morbidity was therefore carried out from this dates on.

The regression analysis has revealed an overall statistically significant increase of infant morbidity during 1991-2000. The average growth rate was 37,0‰ in Zhitomir oblast, 67,6‰ in Kiev oblast, 39,9‰ in Poltava oblast and 71,1‰ in the Ukraine. In comparison with 1991 infant morbidity has increased till 2000 for 21,4% in Zhitomir oblast, for 41% in Kiev oblast, for 34,6% in Poltava oblast and for 42,6% in Ukraine. In comparison with Ukraine the mean values of infant morbidity in Zhitomir oblast were significantly higher (t=2,95, p < 0,05). Also in comparison to Poltava oblast the values are significantly higher in the Zhitomir oblast (t =-3,8, p < 0,01).

During 1994-2000 infant morbidity has increased statistically significantly in Narodichi (growth rate = 95,2‰) and in Ivankov (growth rate = 94,1‰) raions.

There was a non significant decrease of morbidity in Luginy and Polesskoe raions (average rates of decrease were 95,6 and 111,2‰, accordingly). In 1996-2000 there was also a decrease of the infant morbidity in Lokhvytsia raion (average rate of decrease was 4,05‰). In comparison with the control raion Lokhvytsia infant morbidity is significantly higher in Luginy (t=4,1, p < 0,05), Ovruch (t=2,4, p < 0,04) and Polesskoe (t=3,37, p < 0,05) raions.

The level of morbidity has increased in 2000 in comparison with 1994 by 69,3% in Narodichi, by 40,7% in Ovruch, by 99,7% in Ivankov and by 59,6% in Lokhvytsia raions. In Luginy and Polesskoe raions 27 and 38,2% marked a decrease of morbidity, accordingly, but Polesskoe raion show the highest morbidity rate from all raions.

In 1991-2000 in Ukraine and investigated oblasts diseases of the respiratory system (ICD 9 code 460-519) occupy the leading place in formation of infant morbidity (mean value per 1000 infants of Poltava oblast 797, of Kiev oblast 1037, of Zhitomir oblast 1176 and of the Ukraine 935). The morbidity indices are in the contaminated oblasts significantly higher than in the control oblast Poltava (in Zhitomir oblast – t=14,9, p < 0,05; in Kiev oblast – t=7,16, p < 0,05). The increase of the morbidity by diseases of the respiratory organs since 1991 is observed on all territories. During the period 1994-2000 he highest values were recorded in Polesskoe raion of the Kiev oblast with a mean value of 1145‰ and the lowest value in Narodichi raion of the Zhitomir oblast with a mean value of 443‰. In the control raion Lokhvytsia the value was 660,8‰. There could not be established an overall significant growth of the indices. In 1991 on the studied territories the share of the diseases of the respiratory organs of the total morbidity was more than 60%. Till 2000 it was reduced, in the Ukraine to 48,6% and to 55,9% in Zhitomir and Kiev oblasts.

On the second place in the structure of infant morbidity are the diseases of certain conditions originating in the perinatal period (ICD 9 code 764-779) . In 1991-2000 their mean level was 180 (Poltava oblast), 304 (Kiev oblast), 257 (Zhitomir oblast) and 247 (Ukraine) per 1,000 infants. Morbidity by this disease is also growing in all territories during the study period, whereas the indices were in the radioactively contaminated oblasts significantly higher in comparison with the control oblast Poltava (in the Zhitomir oblast – t=4,1, p < 0,05; in the Kiev oblast – t=4,9, p < 0,01). Again in Narodichi raion of the Zhitomir oblast the indices are the lowest (62‰) and in Polesskoe raion of the Kiev oblast the highest 918‰). The highest growth rate was registered in Ivankov raion (105‰ in 1994 and 742‰ in 2000). The mean value in the control raion Lokhvytsia is 149,2‰.

The fraction of diseases from certain conditions originating in the perinatal period of total morbidity has increased from 9,4-12,1% up to 14,2-17,0%

The third place in the structure of infant morbidity is occupied by disease of nervous system and sense organs (ICD 9 code 320-389) with mean levels of 63,0 (Poltava oblast), 102 (Kiev oblast), 94 (Zhitomir oblast) and 97,5‰ (Ukraine). The morbidity from this disease for 1991-2000 is also considerably increased, especially in radiation-contaminated oblasts in comparison to the control oblast Poltava, where no real increase is observed. The average growth rate was 8,4‰ in the Zhitomir oblast and 8,3‰ in the Kiev oblast. In the radioactively contaminated oblasts the morbidity was significantly higher in comparison with the Poltava oblast (in the Zhitomir oblast – t=3,8, p < 0,01; in the Kiev oblast – t=4,5, p < 0,02). The ratio of diseases of nervous system and sensitivity organs of the total morbidity has increased from 2,7-5,3% in 1991 up to 3,7-6,8% in 2000.

In the radioactively contaminated raions the levels of the infant morbidity from separate classes of diseases varied highly during 1994-2000. The first two places in the morbidity structure were occupied by diseases of respiratory organs with the contribution of 30-72% (depending on raion and year of observation) and certain conditions originating in the perinatal period (their share in the morbidity was 6-48%). Rank third – fourth was morbidity of the infants from diseases of nervous system and sensitivity organs and diseases of digestive organs (their share was on average 5-11%).

3.9. Correlation of the data with the contamination of the investigated territories

There is no obvious correlation between the indices of infant mortality and the average levels of soil contamination by 137Cs. The exception is the raions Ivankov and Polesskoe, where the correlation coefficients demonstrate a small, but significant correlation. Thus, a positive correlation is established for stillbirth rate (r s = 0,58-0,59, p < 0,05), perinatal mortality (r s = 0,58-0,62, p < 0,05), postneonatal mortality (r s = 0,55, p < 0,05) in the Ivankov raion and early neonatal mortality (r s = 0,46, p < 0,05) in the Polesskoe raion. Inspite of these correlations most indices of infant mortality are decreasing in the period of the study, so that it is not possible to give a reliable answer to the question of a radiation effect.

Significant dependencies between indices of infant morbidity and soil contamination by 137Cs were not revealed in Luginy, Ovruch and Ivankov raions. At the same time in the most contaminated Narodichi and Polesskoe raions the rank coefficients of correlation were 0,93 and 1,0 (at p < 0,05). Morbidity was least in Narodichi raion and highest in Polesskoe raion. Thus, despite this strong correlation it is not clear what the real reasons are for the increase of infant morbidity in the contaminated regions.

3.10. Correlation of the indices with the thyroid doses

Estimation of dependencies of indices of infant mortality from exposure doses to the TG in the age group 0≤1 years was carried out by non-parametrical coefficients of correlation simultaneously for all five radioactively contaminated raions for 1986 (cross correlation analysis).

There are observed no statistically significant dependencies of indices of infant mortality and its components from irradiation doses to TG by radioiodine. In most cases the received results of rank correlation show reverse dependencies between the attributes.

3.11. Correlation of the indices with average individual whole body exposure doses

Up to now in Ukraine there are no data of individual exposure doses of the inhabitants of the RCT. Profound epidemiological researches are therefore limited. In order to find a possible correlation of the indices of infant mortality with an exposure dose, the mean whole body doses per year of the population of the contaminated raions divided by the number of population was used. The calculations were carried out with the help of methods of the non-parametrical rank correlation analysis by the program STATGRAPHICS.

The majority of the received values of the coefficient by Spearman’s confirm the absence of a connection between the investigated attributes (r s = 0,01-0,46, p > 0,05). The exceptions were the coefficients of correlation between indices of perinatal mortality and individual average irradiation doses in Ovruch and Ivankov raions (r s = 0,78, r s = 0,56, p < 0,05) and between the parameter of early neonatal mortality in Polesskoe raion (r s = 0,56, p < 0,05). The values of rank correlation coefficients by Spearman’sshow an average degree of correlation.

3.12. Correlation of the indices with the total accumulated (at the end of the appropriate year) collective doses of whole body irradiation

An estimation of the dependencies of the level of indices of infant mortality, of stillbirth rate, early neonatal, perinatal, neonatal and postneonatal mortality from the total accumulated (at the end of the appropriate year) CD of whole body irradiation of the inhabitants of the RCT is carried out. The non-parametrical correlation analysis was used for these estimations. Rank coefficients of Spearman’scorrelation between the above listed indices and accumulated effective CD for 1986-2000 was estimated using the dosimetric data and the data of the structure of infant mortality. The designed values of rank coefficients of correlation by Spearman’sare within the limits of 0,01-0,42 depending on the kind of indices and the territory. They are not statistically significant, and when the p value is significant, it is for a negative rank coefficient, that speaks for absence of a correlation between the attributes. There is no connection between the revealed changes of indices of infant mortality in the post-accidental period and the accumulated effective CD on the whole body of the population.

3.13. Risk analysis

The analysis of coefficients grouped by the five-year periods has revealed increased risk of the infant mortality on the RCT in comparison with the control Poltava oblast. So, the RR of infant mortality in the Zhitomir oblast has exceeded 1,0 in 1986-1990 on account of postneonatal mortality. The highest values of the RR were in 1991-1995: neonatal mortality – 1,35 (1,21 < RR < 1,52, p < 0,005), perinatal mortality – 1,26 (1,16 < RR < 1,36, p < 0,005).

The RR of the infant mortality and its structure (designed in relation to the pre-accidental period) in investigated raions are shown, what it in radioactively contaminated raions has reliably exceeded 1,0 since 1986. This increase was caused by increase of the RR of the infant mortality in the neonatal period, in the age of 0-6 and 0-27 days. Also in control raions (five raions of the Poltava oblast) in the post-accidental period a statistically significant increase of the RR of infant mortality in the age of 0-27 days was revealed in 1991-1995. The RR of the stillbirth rates after the accident were decreasing both in radioactively contaminated and control raions.

The analysis has revealed no statistically reliable increase of the RR of the infant mortality and its structures in radioactively contaminated raions in comparison to the control raions in 1986-2000 ( p>0,05) .

4. Conclusions

1. In the contaminated raions the average individual irradiation doses to the thyroid gland of infants were from 0,34 to 4,57 Gy and for adults from 0,22 to 0,5 Gy. The average individual irradiation doses to the whole body in the selected settlements are within the limits of 2,2 to 8,1 mSv. In some settlements the expected lifetime doses can exceed the established limit of 70 mSv. The effective irradiation doses for the inhabitants of the investigated raions during the period from 1986 to 2000 varied from 6,0 mSv (Polesskoe raion) to 29,4 mSv (Luginy raion). The collective effective irradiation doses varied between 66 (Polesskoe raion) to 1723 (Ovruch raion) pers.-Sv. The overall collective irradiation doses during the period from 1986 to 2000 were 13 530 pers.-Sv in the Zhitomir area and 9 960 pers.-Sv – in Kiev and correspond to almost 50% of the collective dose of the whole country.

2. Since 1991 in Ukraine the socio-economic crisis led to a considerable deterioration of life standards of the inhabitants of the country. The observed demographic crisis is characterized by a decrease of the population number, due to a decrease of birth rate and a decrease of life expectancy by increased general mortality. In the contaminated raions the age distribution is distorted by resettlement activities.

3. Infant mortality is decreasing in all oblasts of the study and Ukraine as a whole. Also in the control raions of the Poltava oblast the infant mortality index is decreasing, whereas in the contaminated raions no reliable decrease is observed, the mean indices were 14,7 ± 3,7‰.

4. Stillbirth rate is decreasing in all oblasts, Ukraine and both the contaminated and the control raions. The indices decrease on the oblast and raion level from 10 to 6‰. In the contaminated raions the stillbirth rate is lower in comparison to the control raions. However, the years 1999 and 2000 are characterized by an increase of the stillbirth rate in the contaminated raions.

5. Perinatal mortality decreased on the oblast level and Ukraine as a whole from 15 to 10‰. In the control oblast Poltava this index decreased to 7‰, Zhitomir oblast having the highest values. On the raion level there is no decrease stated.

6. There is no significant decrease in early neonatal mortality in both groups of raions the mean values are 4‰.

7. Neonatal mortality did not show any remarkable changes during the period from 1981 and 2000 in the oblasts and in the contaminated and control raions. The indices varied between 3 –10 cases per 1000 live births children with mean values of 5,3‰ (contaminated raions) and 5,9‰ (control raions). The indices are lower in the raions in comparison to the oblasts by 1‰.

8. Postneonatal mortality is slightly decreasing for Ukraine and the oblasts of the study (7-9‰ to 5,2-6,3‰); in the control and contaminated raions there is no clear tendency observed.

9. The main causes of infant deaths in the investigated territories were diseases of respiratory system, certain conditions originating in the perinatal period and congenital anomalies. During the period 1986-2000 a general decrease of infant mortality from the given causes of death was registered.

The main causes of early neonatal mortality are the syndrome of respiratory distress (more than 33%), congenital anomalies (about 25%), birth trauma (up to 13%) and intrauterine hypoxia and asphyxia in childbirth (5%).

10. After the accident there was a general increase of infant morbidity on almost all territories. Diseases of respiratory system, certain conditions originating in the perinatal period, diseases of nervous system and sense organs occupy the leading place in the structure of infant morbidity.

11. The epidemiological analysis has revealed in some instances a weak correlation between changes of stillbirth, early neonatal, perinatal neonatal and postneonatal mortality, with the contamination of soils by 137Cs, with individual average and collective irradiation doses of thyroid gland and the whole body of the population living in the contaminated raions of the Kiev and Zhitomir oblasts.

12. There is no statistically reliable increase of the RR of the infant mortality in radioactively contaminated raions in comparison to the control raions in 1986-2000. When however the indices of infant mortality of the post-accidental time were compared with the pre-accidental time, then there is an elevated RR in the contaminated raions on account of the mortality in the neonatal period.

5. Outlook

The accumulated data show that it is not possible to get an unequivocal answer to the question of an effect of acute and protracted radiation exposition of the population measured by various indices of infant mortality. However, the observation of the parameters of infant mortality in the study regions in the following years would allow a better estimation of the health effects after the Chernobyl accident.

The validation of monthly indices of the structure of infant mortality in the year after the Chernobyl accident with the determination of more realistic individual doses could contribute to a deeper understanding of the early health effects.

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