Spatial-temporal Trend Analyses of Infant Mortality Versus Chernobyl Fallout in Switzerland (1969 - 2024): Analysis of a Dose Response Association at the Canton Level

Abstract

Background: In Switzerland from 1987 to 2022 after the Chernobyl accident in April 1986, the infant mortality proportion jumped relatively parallel to the prevailing monotone secular downward trend from 1950 to 1986. The jump odds ratio (OR) in 1987 was 1.175 (1.102, 1.253). This report aims at studying whether the cantonspecific drops or jumps of the infant mortality in 1987 are associated with the average Chernobyl cesium-137 (Cs-137) fallout in the Swiss cantons.

Methods: Counts of annual live births and infant deaths under one year of age from 1969 to 2024 stratified by sex and the twenty-six Swiss cantons were obtained from the Federal Statistical Office (FSO). The Swiss Federal Office of Public Health (FOPH) provided a map of Switzerland documenting Cs-137 Chernobyl fallout (kBq/m2) in early May 1986. Possible dose-response associations of Chernobyl fallout with infant mortality were analyzed employing five parsimonious regression techniques.

Results: The overall infant mortality proportion in the period 1969 - 2024 was 0.65%, i.e., 29,322 infant deaths in 4,524,021 live births. Restricted to the period 1987 - 2024 (with a total of 13,948 infant deaths), the jump OR in 1987 in the long-term infant mortality trend is 1.165 (1.095, 1.240), p-value < 0.0001 and translates to 1964 (1201, 2688) excess infant deaths from 1987 to 2024. The five regression techniques consistently suggest that infant mortality in Switzerland after Chernobyl increased in the order of 1% to 3% per kBq/m2 Cs-137 fallout.

Conclusion: In Switzerland after the Chernobyl accident, the positive association of canton-specific jumps in infant mortality with canton-specific Chernobyl fallout strengthens the evidence of a causal link of low dose ionizing radiation (IR) and detrimental effects on early human development.