what factors affect amount of radiation exposure to background

• Journal List
• Environ Health
• v.ane; 2002
• PMC149393

Environ Health. 2002; 1: 4.

Influence of diverse factors on individual radiation exposure from the chernobyl disaster

Pavlo Zamostian

¹National University "Kyiv Mogila Academy" Department of Environs Sciences, Kyiv, Ukraine

Kirsten B Moysich

²Roswell Park Cancer Institute, Buffalo, New York, USA

Martin C Mahoney

ⁱⁱRoswell Park Cancer Institute, Buffalo, New York, USA

Philip McCarthy

^twoRoswell Park Cancer Establish, Buffalo, New York, USA

Alexandra Bondar

ⁱNational University "Kyiv Mogila University" Department of Environment Sciences, Kyiv, Ukraine

Andrey Yard Noschenko

^aneNational University "Kyiv Mogila University" Section of Environment Sciences, Kyiv, Ukraine

Arthur G Michalek

ⁱⁱRoswell Park Cancer Institute, Buffalo, New York, U.s.a.

Received 2002 Jul xviii; Accustomed 2002 Oct 29.

Abstruse

Groundwork

The explosion at the Chernobyl Nuclear Ability Establish was one of the greatest known nuclear disasters of the 20th century. To reduce individual exposure to ionizing radiation the Soviet Wedlock government introduced a number of counter-measures. This article presents a description of how historical events conspired to disrupt these efforts and bear on residents in exposed areas.

Methods

This study employed an extensive review of data on radionuclide deposition, contamination patterns and lifestyle characteristics. Data were obtained from the Ukraine Ministry of Health and the Ukraine Enquiry Center for Radiation Medicine.

Results

Data are presented on annual contamination rates in selected locales also as information on local food consumption patterns. Historical factors including economic and political circumstances are also highlighted. Results prove the diminution of individual doses between 1987 and 1991 so an increase between 1991 and 1994 and the relationship between this increase and changes in the lifestyle of the local population.

Conclusion

A number of factors played straight and indirect roles in contributing to the populace's cumulative radiation exposure. Time to come mail service-contamination studies demand to consider these factors when estimating individual exposures.

Background

The Chernobyl Nuclear Ability Plant accident tin can be differentiated from other radiation accidents not but by its magnitude but also past its transcontinental impact and the unique patterns of radionuclide fallout. It is estimated that more four million people in the Ukraine lonely were exposed. Unlike the diminutive bomb detonation, exposures from Chernobyl were different and subtler [1]. Rather than high-energy external exposure, the vast bulk of individuals received on-going, low-dose exposures owing to the presence of long-lived radionuclides such as cesium (Cs), strontium (Sr) and plutonium (Pu) in their food supply. These exposures and the government's response to minimize their effect were further complicated by the interplay of economic and political factors resulting from the dissolution of the Soviet Marriage.

This study describes the dynamics of these factors in a specific region of Ukraine where the population received significant internal doses of radiation due to consumption of radioactively contaminated food and where these exposures, and thereby their health risks, announced to have been exacerbated by the dissolution of the Soviet Union and subsequent disruption of protective counter-measures.

Characteristics of the report region

Fallout from the Chernobyl Nuclear Power Plant accident contaminated vast regions of the Ukraine. The territories of the "Ukrainian Polissia" region of Ukraine were among those virtually affected. These rayons*, located at the northern part of the Kyiv, Zhitomir and Rivno Oblasts, span over 50,000 square kilometers and are abode to over 1.7 million people (Figure ​ 1). The Polissia territories are known for their bang-up variations in environmental and geographic conditions also every bit in agronomical patterns. Radioactive contamination inside these territories (excluding the more than highly contaminated 30-km exclusion zone) may exist characterized by levels of ¹³⁷Cs ground degradation densities of upwardly to 555 kBq·m^-2 (local spots upwards to 3700 kBq·g^-2); ^xcSr depositions more often than not did not exceed 100 kBq·m^-2; and ^238–240Pu depositions did not exceed 370 kBq·1000^-2[2].

Map of Ukraine showing Oblasts in relation to the Chernobyl Nuclear Ability Institute

Local contagion

The Rivno Oblast, located approximately 250–300 km from the Chernobyl Nuclear Power Plant, is 1 of the more than interesting areas within the Ukrainian Polissia. Levels of ¹³⁷Cs soil deposition did not exceed 200 kBq·g^-2, and levels of ⁹⁰Sr and ^238–240Pu depositions were negligible. Because of these "depression" levels of exposure, this area was non officially considered "radioactively contaminated" by the Chernobyl accident. Detailed studies of this surface area, therefore, were not begun until 1987–1988, when unusually high levels of ¹³⁷Cs were detected transferring from soil to plants and through the ecological chain to animals and people. The local environment too has peat-swampy soil that is characterized past the highest values of soil-to-milk transfer coefficients.

In add-on, the rayons of the Rivno Oblast may be characterized by unique socioeconomic characteristics and subcontract-direction practices. Residents tend to live in small villages surrounded by forests. Family unit size tends to be moderately large (three to five children). The main nutrient sources are locally produced (vegetables, milk) and/or include foods that can exist foraged from the forests (mushrooms, berries and wild game) and swamps (cranberries). These wild foods are known to nearly readily concentrate radioactive elements (particularly ¹³⁷Cs). It is estimated that approximately 90 percent of the total lifetime radiation dose to individuals in the population is due to internal exposure to radiation from radiocesium ingested in contaminated foodstuffs [3].

Methods

Radiations exposure measurements and dose estimates

The Rokitnovsky rayon, which is located within the Rivno Oblast, was selected for this study because it is well described by the above characteristics. Moreover, an assortment of personal and ecology radiation monitoring information are bachelor for this surface area from the Radiation Protection Establish [4]. Table ​ one summarizes the information on radioactive contamination of Rokitnovsky due to the Chernobyl accident.

Tabular array 1

Radioactive contamination of the Rokitnovsky Rayon, Rivno Oblast

Soil deposition	Mean, kBq·m-two	Standard divergence, kBq·m-ii	Maximum, kBq·m-2	Minimum, kBq·m-ii
137Cs	74,three	32,2	170,2	25,9
90Sr	4,5	5,5	23,iii	0,4
238–240Pu	0,037	0,027	0,xiv	0,0

Source: Ministry building of Wellness, 1995^thirteen

An individual'south dose is calculated based on external (direct exposure) and internal exposures (i.e., consumption of milk and wild foods). Of item involvement in this give-and-take is internal exposure. It is possible to estimate internal exposures from radiocesium ingestion within a detail population by because the concentration of ¹³⁷ Cs in the human diet over different periods of time [iii]. This concentration is determined by the radioecological atmospheric condition at the place where the foodstuffs were produced (¹³⁷Cs soil deposition and its soil-transfer factor) and dietary patterns (i.e., frequency, quantity of particular foodstuffs such every bit milk, mushrooms, etc.).

Radiological monitoring for internal exposure may be accomplished in two ways: ane) monitoring of radionuclide body brunt past whole torso counters (WBCs); or ii) monitoring of radionuclide concentrations in various foodstuffs and their reported consumption. Continuous WBCs of radiocesium body burden across gender and among unlike age groups and seasons of year is the most accurate way to judge internal exposure [4,v], just surveillance is often complicated and time consuming. While measurement of radiocesium concentration in locally produced foodstuffs provides information on the relative contribution of specific food items, information technology is quite hard to determine private values and oft impractical.

Contamination of locally produced milk

In the Ukrainian population, milk is widely consumed by both children and adults since it is readily bachelor throughout the year in all areas. Milk is also a significant source of internal exposure due to its concentration of radiocesium. Co-ordinate to the results of dietary studies in the northern part of Rivno Oblast [4,vi] approximately 70–75% of daily ¹³⁷Cs intake is due to consumption of locally produced milk and milk products; about x–15% may exist attributed to forest mushroom and berry consumption and about 10–15% due to irish potato and vegetable consumption. Thus, consumption of locally produced milk appears to represent the most of import factor in determining internal radiocesium exposure. Although wood mushrooms and berries are highly contaminated with ¹³⁷Cs, most of the internal exposure resulted from milk consumption due to the prevalence of milk consumption in this population.

Countermeasures

A number of countermeasures were initiated after the Accident. The goal of these activities was to reduce the population's internal exposure to radionuclides such every bit ¹³¹I in the brusque-term and ¹³⁷Cs in the long-term. The virtually significant countermeasures included governmental prohibitions of consuming locally produced milk and foodstuffs, warnings against consumption of wild foods (mushrooms and berries) utilize of "clean areas" for farming and pastures where improvements had been applied and application of Cs binders to fauna foods. In add-on, the government distributed foods from uncontaminated areas to the residents of contaminated areas. The success of these counter measures was likely non-compatible and varied by oblast likewise as by type of farm (commonage vs. private). The long-term success of this strategy depended on continuous governmental back up and compliance among residents inside the affected areas. According to a study by the International Diminutive Energy Bureau (IAEA), the application of countermeasures led to significant reductions in radiocesium contamination of milk and meat produced on State and collective farms [7]. They notation, however, that many of the countermeasures were difficult to utilise by modest-scale farmers for economic reasons thus affording significant proportions of the population with trivial protection.

Results

Ionizing radiation exposure cess or biomonitoring

Figure ​ 2 illustrates results of ¹³⁷Cs concentrations in milk from 1988 through 2000 in Rokitnovsky. In excess of 5000 gamma-spectrometry measurements of milk were conducted during this period. Milk samples were collected from privately endemic cows by the Ukrainian government as part of a radiological monitoring program inside areas contaminated by the Chernobyl accident. Milk samples from privately endemic cows were tested because milk is a significant dietary staple of these individuals and is known to concentrate Cs.

Dynamics of ¹³⁷Cs concentration in milk (Bq-L), produced on private farms in selected villages, Rokitnovsky Rayon, Rivno Oblast, Ukraine

In the selected settlements of Vezhitsia, Drozdyn, Perehodichi and Stare Selo approximately 20–lxxx milk samples were collected each year during pasture season (leap through autumn). Concentration of ¹³⁷Cs and ¹³⁴Cs was determined in these milk samples by means of gamma-spectrometry measurements. As demonstrated past Figure ​ ii, while there is variation in the concentration of ¹³⁷Cs in milk in different areas of the Rokitnovsky region, there is a significant decline in ¹³⁷Cs milk concentrations over fourth dimension. The former may be attributed to a number of factors such as the actual radioactive contamination of the territory (Tabular array ​ 1) likewise as differences in ecology weather condition (soil types, landscapes, etc.) that affect the transfer of ¹³⁷Cs from the soil. For example, the transfer factor of ¹³⁷Cs from soil to milk in 1991–1992 was in the range from 0.3 to 20 Bq·L^-2 per kBq·m^-2.[eight]. The soil transfer gene is the nearly of import parameter in determining ¹³⁷Cs concentration in locally produced milk. The villages of Vezhitsia, Drozdyn, Perehodichi and Stare Selo exhibited the highest soil-to-milk transfer coefficients. For 1991–1992, recorded values were 19.9 Bq·L^-2 per kBq·grand^-2 in Vezhitsia, 19.4 Bq·L^-2 per kBq·g^-2 in Drozdyn, 9.9 Bq·50^-2 per kBq·thousand^-2 in Perehodichi and 17.iv Bq·L^-two per kBq·m^-2 Bq-L^-two in Stare Selo. High transfer factors coupled with other local characteristics (e.g., proximity to forests and swamps, availability of cultivated pastures for cows) make these areas the most disquisitional from the standpoint of internal exposure in nearby residents. From 1988 through 1991, the mean concentration in milk (for all of Rokitnovsky) decreased by more than 4 fold and past 1996 most ten-fold. Decrements of similar magnitude have been reported past other investigators [9,10]. No further decrease was observed for the menstruation 1996 through 2000. Given that milk is an important contributor of radiocesium intake for rural people as previously described, decreases in ecology contamination levels would be paralleled by decreases in the local population's internal dose.

Whole trunk counts

Showtime in 1987, the Ukrainian regime-monitoring program in the radioactively contaminated areas initiated directly body brunt measurements of radiocesium using WBCs amidst Rokitnovsky residents [4]. Virtually 16,000 WBCs were performed among unlike age groups, with approximately 7000 measurements amongst adults. The majority of these were performed in the field past the Inquiry Center for Radiation Medicine (RCRM) using mobile whole trunk counters while some were performed in the central laboratory at the RCRM in Kiev. Regardless, all measurements were made using similar methodology and are considered equally valid. Information technology should be noted that the number of measurements performed each year did vary. Individuals were selected from each settlement. The typical annual number of measurements in each settlement was l–100, which corresponds to 10–20% of the developed population in each settlement. Nevertheless there were some years when only 10 measurements were made in a given settlement while in other years 300–400 measurements were fabricated.

Mean annual effective doses calculated based on results of WBC measurements between 1988 and 2000 are presented in Effigy ​ three. As tin can exist seen, there is great variation among annual internal effective doses (D_int) of radiation from ingested radiocesium. D_int depends on ii chief radioecological parameters – the value of ¹³⁷Cs deposition in soil and the soil-to-milk transfer factor. Annual effective doses through internal exposure (D_int) appear higher in these selected villages (Vezhitsia, Drozdyn, Perehodichi and Stare Selo) compared to the mean value for the whole Rayon. From 1988 until 1991, D_int decreased 2–4 fold; then between 1992 and 1994 in that location was a rapid increase of D_int followed by a slight reduction (1995) so a stabilization of dose (1996–2000). However, for selected villages (peculiarly in Stare Selo and Vezhitsia), there are annual variations with no discernable blueprint of decreasing doses. These observations warrant farther investigation to analyze the roles played by the application of counter-measures, lifestyle changes, elimination of radionuclides from the ecosystem and/or other unmeasured factors.

Dynamics of annual effective doses of internal exposure (D_int) due to ¹³⁷Cs ingestion in Rokitnovsky Rayon and selected village, Rivno Oblast, Ukraine past twelvemonth from Whole Torso Count (WBC) data

Modifying factors

A myriad of factors are known to contribute to individual Chernobyl-related ionizing radiations exposure. Chief among these is direct environmental contagion from the blow based on prevailing current of air patterns, type of housing, amount of time spent outdoors, etc. Other factors include those that affect levels of internal exposure such every bit soil types (soil-to-milk transfer factors) and consumption patterns of contaminated foods (locally produced and wild). While these factors directly contribute to individual exposures, they are also bailiwick to the influence of external forces. The confluence of economic (collapse of the Soviet Union in 1991), environmental (fallout patterns and local soil-to-milk transfer ratios) and sociological (local food consumption patterns) factors resulted in significant variations in individual exposure.

Radionuclide fallout from the Chernobyl reactor explosion and the ensuing graphite fire contaminated vast areas of land, most of which was agricultural. The firsthand governmental response was the destruction of livestock and food crops within the contaminated areas. Counter-measures were then introduced by the Soviet Matrimony government that included shipments of uncontaminated milk and foods into these areas and so as to reduce individual exposure and associated wellness risks. If these countermeasures were not introduced and people continued to consume locally produced foodstuffs, levels of D_int of ¹³⁷Cs would have continued unabated and the populace'south only hope would have been time, the fourth dimension information technology would take for the natural elimination of ¹³⁷Cs from the ecosystem. And fourth dimension is not an ally. While the half-life of ¹³⁷Cs in agricultural products is 2.8–5.6 years, it is approximately 10 years for berries and 20 years for mushrooms [11]. Fesenko, et al.[12] studied xx-seven rural settlements to assess the effectiveness of countermeasures. They observed an initial subtract of up to 40% of doses with a gradual diminution of issue over time.

Discussion

Introduction of countermeasures such as the provision of non-contaminated foodstuffs from 1988 until 1991, resulted in decreases of ¹³⁷Cs exposures based upon biomonitoring and WBC data in the Rokitnovsky Rayon by more than two-fold. Similar decreases were documented in other villages, such as in Perehodichi and Vezhitsia, where levels dropped almost four fold. Subsequently the collapse of the Soviet Matrimony in 1991, values of D_int in these areas quickly increased and approximated values registered in the immediate post-accident menstruation.

A plausible explanation for the increase in D_int relates to the severe economic strains brought on by the dissolution of the Soviet Union and a abeyance of government sponsored counter-measures. The plummet of the FSU, which was accompanied by high unemployment and economic hardship, led to a reversion to traditional diets. People were forced to once once more consume more locally produced nutrient as well as "free" natural foods from the forests (mushrooms, berries, wild game, etc.). Moreover, subsequently a relatively short catamenia of time, it is likely that people became indifferent to warnings of the possible harm from radiation and to recommendations about the consumption of these foods. The influence of these factors is especially stiff in those villages located in the wood area, where wild foods are a traditional mainstay of the local diet. Radiological contamination is tasteless, odorless and invisible. Information technology is only natural that after the "immediate" crisis passed more people were more concerned with the immediate effects of hunger rather than any possible long-term wellness effects.

Further evidence to support this hypothesis can be gleaned from interviews conducted by one of the authors (PZ) amongst a sample of residents of the northern rayons of the Rivno Oblast covering the period 1987 and 1994 (retrospectively collected by PZ). Families were asked whether they consumed the post-obit foods: home milk and milk products, vegetables, potatoes, home meat, mushrooms and berries from the forest, local fish and wild game (Figure ​ four). Results betoken that for 1994, more people reported consuming such potentially highly contaminated products as mushrooms and wood berries compared to 1987. For example, only 31% of those interviewed in 1987 reported eating forest berries compared to 92% in 1994. For wild mushrooms, 29% reported consumption in 1987 compared to 44% in 1994. Withal, the proportion reporting consumption of milk (97%), potatoes (98%) and vegetables (97%) remained constant over time (data not shown in Effigy). It should be noted that in most of the territories with high levels of ¹³⁷Cs contagion (i.e., those where external exposure > internal exposure), about 40% of the dose was received during the beginning yr following the accident and about lx%, owing to internal exposures, during the side by side five to vii years with relatively little received thereafter [xiii].

Pct Reporting Consumption of Local Foodstuffs Among Residents of Rivno Oblast by Year

Conclusions

We have related how a number of factors contributed to individual exposures among residents of the Polissia Region in Ukraine. Opposite to initial expectations that nutrient management practices, effective counter-measures, and fourth dimension would result in decreased internal exposure from ¹³⁷Cs, this did non occur perhaps due to social and economic forces active in the study region. The economic crisis that occurred in the Ukrainian part of the Onetime Soviet Marriage after 1990 likely contributed to increased internal doses from ¹³⁷Cs owing to consumption of locally produced and wild foods (mushrooms, berries, wild game, etc.).

In the absence of serial WBCs, private exposure can only be estimated based on environmental sampling and personal interviews. Future post-contagion studies demand to include continuous monitoring of both the radiation content of locally produced foodstuffs and patterns of consumption. Moreover, efforts should include periodic population surveys to appraise changes in dietary behaviors, agronomical practices, politico-economic issues, and other factors that could affect internal dose estimates. Only on the basis of such information volition it be possible to reasonably plan, implement and evaluate constructive protective programs aimed at reducing exposures and to affect the subsequent gamble of morbidity and mortality.

Listing of Abbreviations

Bq: Becquerel Cs :Cesium

D_int:Internal effective doses

IAEA: International Atomic Free energy Agency

I: Iodine

Pu: Plutonium

RCRM: Enquiry Center for Radiations Medicine

Sr: Strontium

WBC: Whole trunk count

Competing interests

None declared.

Authors' contributions

PZ and AGN participated in statistical analysis and drafting the manuscript. MCM, PM, and AB participated in study design and manuscript preparation. KBM and AMM conceived of the report and participated in its blueprint and manuscript preparation.

Note

* The Ukraine consists of 24 large administrative units – Oblasts and the Democracy of Crimea. Each Oblast consists of smaller administrative units called Rayons.

Acknowledgements

"This work was supported by Grant #N00014-94-ane-0049 issued to Georgetown University from the Office of Naval Research in support of the International Consortium for Research on the Health Effects of Radiation. The contents are solely the responsibleness of the authors and practise non necessarily represent the Office of Naval Research or Georgetown University."

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC149393/

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