Climate change, the exposome, and early-onset carcinogenesis.

The incidence of early-onset cancers (diagnosis before 50 years of age) has been steadily increasing globally, presenting a significant public health challenge. While genetic predispositions play a role, most cancers cannot be traced to heritable components. Furthermore, the rapid rise in the incidence rates of these cancers strongly suggests the influence of environmental factors that constitute the "exposome." This perspective article integrates recent findings linking climate change and broader planetary health challenges to pervasive inflammation in the development of chronic diseases, especially cancer. We propose that the complex interplay of anthropogenic climate change, biodiversity loss, environmental degradation, disruption of ecological systems, exposure to environmental pathogens and toxins, industrialized food systems, and consumption of suboptimal, proinflammatory diets containing high concentrations of ultra-processed foods, creates a procarcinogenic exposome that may be particularly important during critical developmental windows, leading to increased susceptibility to carcinogenesis relatively early in life. Framed through a planetary health perspective, this article synthesizes evidence on how large-scale ecological disruption alters the human exposome and contributes to chronic inflammation, metabolic dysregulation, immune dysfunction, and cellular damage, all recognized drivers of cancer development. Although our primary focus is on early-onset cancers, many of these mechanisms are relevant across the cancer continuum and may influence carcinogenesis throughout the life course. We highlight the need for transdisciplinary research and integrated solutions that address both individual behaviors and systemic environmental and policy changes to mitigate the growing burden of early-onset cancers.