Teratogenic radiation effects

Perinatal mortality and congenital malformations

following Chernobyl

Alfred Körblein Nuremberg, Germany

Teratogenic radiation effects: Adverse health effects to the fetus after exposure to ionizing radiation:

Congenital malformations, perinatal deaths

(i.e. stillbirths and early neonatal deaths), cognitive impairment

UNSCEAR on teratogenic effects:

• UNSCEAR 2008 (Chernobyl consequences):

A search in the document finds no hit for

“teratogenic” OR “perinatal” OR “malformation”

• UNSCEAR 2013 (Fukushima consequences)

(b) Other health effects, F14:

“Prenatal exposure was not expected to increase .. the incidence of spontaneous

abortion, miscarriages, perinatal mortality, congenital effects or cognitive

impairment.”

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ICRP 90 (2003): Biological effects after prenatal irradiation (embryo and fetus)

• Experimental data on age-dependent patterns of sensitivity to malformation

induction re-inforce the view of maximum sensitivity during major

organogenesis, but with a true dose threshold.

For practical purposes, risks of induction of malformation at low doses may

therefore be discounted.

• (44) Induction of malformations […]

most pronounced during organogenesis (weeks 3-11 p.c.)

• (60) Most experimental data basically fit

sigmoid or shoulder-type dose-response curves [… ]

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ICRP 90, Fig.1.1: Occurence of lethality and abnormality after prenatal radiation exposure of about 2 Gy

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Shape of the dose-response relationship for stochastic and teratogenic effects

From: http://gd1.med.uni-giessen.de/ugm_2/deu/ugi_nuk/PDF/Rad_V2_Strahlentherapie.pdf

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Results of epidemiologial studies

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Perinatal mortality in Germany and regression line.

Excess rate in 1987: 0.36 per 1000 (P=0.018), 317 excess deaths from: Körblein A, Küchenhoff H. Perinatal mortality in Germany following the Chernobyl accident. Radiat Environ Biophys. 1997 Feb;36(1):3-7.

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1980 1982 1984 1986 1988 1990 1992

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1987

Perinatal mortality in Poland and regression line.

Excess rate in 1987: 0.57 per 1000 (P=0.015), 348 excess deaths

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1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991

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1987

Deviations of perinatal mortality in Germany and Poland from secular

trend (standardized residuals) and range of 2 standard deviations.

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1980 1982 1984 1986 1988 1990 1992

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Poland

Germany

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Monthly perinatal mortality rates and trend line. The vertical line indicates the date of the Chernobyl accident.

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Perinatal mortality in Germany

Deviations of mortality rates from undisturbed trend line (standardized residuals) and 3-month moving average. After Chernobyl, mortality peaks are found in

February and November 1987

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Infant mortality rates in Poland and trend line with seasonal variations Lower panel: standardized residuals and 3-month moving average Peaks are found in January , April, and November 1987

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Monthly infant mortality in Poland

Upper panel: monthly rates and regression line Lower panel: Standardized residuals and 3-month moving average Maximum in April 1987

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Early neonatal mortality in oblast Zhytomyr

Trend analysis of monthly data

• Logistic regression with linear-quadratic time trend

• Seasonal effect modeled by dummy coding for individual months (dummy variables for Feb through Dec, Jan=reference)

• Cesium burden of pregnant women calculated from cesium concentration in cow milk (measured), beef, cereals, and pork

• Linear- plus quadratic cesium dependency to allow for a curvilinear shape of cesium effect on perinatal mortality

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From: UNCEAR 2008, Annex D, page 95

Measured cesium-137 concentration in cow milk (black points) and calculated cesium concentration in beef, cereals, and pork, semilogarithmic plot

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1986 1987 1988 1989

cesiu

m in f

oodstu

ff [

Bq

per

kg

]

calendar years

milk beef

cereals pork

Measured cesium-137 concentration in cow milk (black points) and calculated cesium concentration in beef, cereals, and pork, linear plot

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1986 1987 1988 1989

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siu

m i

n f

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ff [

Bq

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r kg

]

calendar years

milk

beef

cereals

pork

Cesium-137 concentration in cow milk (crosses, left axis)

and cesium burden in pregnant women (grey line, right axis), calculated with a biological half-life of 70 days

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1986 1987 1988 1989

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[B

q p

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kg

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cesiu

m in c

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milk

[B

q/l]

calendar years

cesium in cow milk

cesium burden

Cesium-137 concentration in cow milk, beef, cereals, and pork and cesium burden in pregnant women (grey line, right axis), calculated with a biological half-life of 70 days

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1986 1987 1988 1989

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wom

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q/k

g]

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[Bq

/kg

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calendar years

Monthly averages of cesium burden in pregant women from ingestion of milk and other foodstuff

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1986 1987 1988

cesiu

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burd

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[Bq

/kg

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calendar years

other food

milk

Residual sum of squares obtained with regressions of German monthly perinatal mortality rates as a function of time-lag between cesium burden and mortality. Horizontal broken line indicates critical chisquare value. Best estimate of time-lag is 7 ± 1 months.

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time-lag [months]

Standardized residuals of perinatal mortality in Germany and 3-month moving average.

Lower graph: cesium burden of pregnant women, shifted by 7 months

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1985 1986 1987 1988 1989 1990

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Dose dependency Increase of perinatal mortality in Germany as a function of lagged cesium burden,

and regression line. The cesium effect on mortality is significant (P=0.0016, F-test). The dose-response is curvilinear: Linear term <0, quadratic term >0 (P=0.034)

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Dose dependency Increase of infant mortality in Poland as a function of cesium burden, and regression

line. Cesium effect on mortality is significant (P=0.014, F-test). Dose-response is curvilinear: Linear term <0, quadratic term >0 (P=0.016)

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Congenital malformations in Bavaria

• After Chernobyl, a study of congenital malformations in Bavaria was conducted by German Federal Office of Radiation Protection (BfS-ISH)

• The following isolated malformations were included: - neural tube defects, - anophtalamus, microphtalamus, cararact - limb anomalies - cleft lip and palate - atresia of gastrointestinal tract - cong. anomalies of the heart, cong. anomalies of abdominal wall - diaphragmatic hernia

• Malfomations with likely genetic origin: trisomy 21, malformation syndrom (multiple malformations)

• Malformation rates in Southern Bavaria (total cesium soil contamination: ~30 kBq/m²) were compared with rates in Northern Bavaria (~10 kBq/m²)

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Method: Cesium burden cs(k, t) is defined as the product of (1) cesium soil deposition (kBq/m²) in district k (k = 1 to 96) cs(k) and (2) cesium concentration (Bq/kg) in pregnant women as a function of time t, cs(t) cs(k, t) = cs(k) * cs(t) [kBq/m² *Bq/kg] The model allows for a linear time trend and a linear-quadratic dose-response i.e. a nonlinear dependency of malformation risk on cesium burden. Result: The association of malformation rates with cesium burden is significant (P=0.014, F-test ). The dose-response curve is non-linear: neg. linear term (P=0.0092), pos. quadratic term (P=0.0023) from: Küchenhoff H, Engelhardt A, Körblein A, 2006 available at: http://www.ratical.org/radiation/Chernobyl/chernobylebook.pdf, pp 179-183

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Combined spatial-temporal regression

Odds ratios (~relative risks) of malformation rates in Bavarian districts as a function of cesium burden, aggregated values and regression line. The error bars are standard deviations.

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Summary

• In 1987, perinatal mortality is significantly increased in Poland and in Germany. Effect in Poland is 1.6 times greater than in Germany.

• 317 excess perinatal deaths in Germany and 354 in Poland in 1987

• Significant association of perinatal mortality in Germany and infant mortality in Poland with calculated cesium burden during pregnancy

• Curvilinear dose-response (negative linear, positive quadratic term)

• Significant association of malformation rates in Bavaria with cesium burden

• No “safe dose“ (threshold dose) for teratogenic effects

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