Published online by Cambridge University Press: 29 October 2007
An understanding of the cosmic ray modulation of life processes is critical to space exploration, evolution and current medical science. Previous evidence has implicated a role for cosmic rays in US female cancer, involving a possible cross-generational foetal effect. This study explores the global nature of that effect by examining cancer time variations for population cohorts in five countries on three continents. Age–period–cohort analysis was used to separate cohort-related effects from period-related effects, generating time signatures for comparisons among both male and female populations in the United States (US), United Kingdom (UK), Australia (AU), Canada (CA) and New Zealand (NZ). The available cancer mortality data spanned most of the 20th century for US, UK and AU, with shorter periods for CA and NZ. The longest cohort series spanned 1825 to 1965 and exhibited two peaks of higher mortality likelihood approximately 75 years apart in all countries and in both sexes. The constancy of this oscillation on three continents and both hemispheres suggests the presence of a global environmental effect. To explore a possible source for this effect, the birth cohort oscillation is shown to correlate with the variations in background cosmic radiation one generation prior to the birth cohorts. This confirms an earlier study correlating human breast cancer mortality and galactic cosmic rays. A corroborating correlation is also noted between the latitude dependences of cancer incidence in 42 countries and the intensity of background cosmic rays. The role of germ cells as a possible target of this radiation is discussed, emphasizing the amplification that must occur to make this weak radiation relevant to human health. Germ cell timing for this effect has profound implications for evolution, long-distance space travel and the colonization of planets with high background radiation.