BioEssays | 2021
Environment and human health as complex interacting systems
Abstract
It is my privilege to serve as Guest Editor of this Focus Issue of BioEssays which was written during a year of many challenges—a pandemic that has changed every facet of human life, major transformation of political systems, a climate crisis that threatens the wellbeing of our planet itself, and a world-wide demand for social justice that pushes against the inertia of age-old socio-economic hierarchies. From all this, it is clear now that our environment is important, and while this may seem an obvious statement, the past several decades of human scientific effort have not given environmental determinants of health their due—our investment in genetics has far outweighed that in environmental health sciences, for example. However, the tide is turning, and the articles that are included in this issue exemplify that the future will be a ‘‘multi-omic’’ amalgamation of scientific effort that does not assign privilege to any one field but does recognize that a holistic study of the environment is a necessary component of all efforts to understand health and disease. Unlike our base genomic code, the environment is not finite, and no boundary can be placed around it. For this reason, Environmental Health as a field is also not easily defined, but there is a general agreement that it focuses on the interaction of human physiology with physical, chemical, biological and social factors.What is often not discussed in formal definitions of Environmental Health is that the interactions between the environment and human physiology operate across multiple levels and scales. This then gives way to a complexity that cannot be resolved by reductionist thinking. However, reductionismand structuralism have plagued environmental health sciences as much as any other field giving rise to fragmented studies on individual environmental factors that cannot be combined into a coherent model. To address this problem, a recent conjecture, to which I was a contributor, proposed that complex systems cannot interact directly or exist in isolation.[1] Titled, theBiodynamic InterfaceConjecture, it postulates theexistence of an operationally independent interface that connects the environment and human health. The carefully curated articles in this issue further support this to show how the environment and our physiology are indeed complex interacting systems, and the connections that we form with various environmental factors cannot be resolved by reducing them to simple correlations. Thoughtful pieces included in this issue connect large-scale exposures such as air pollution, bushfires that spanned millions of acres, and persistent use of pesticides to complex health problems such as cardiovascular disease and neurodevelopmental disorders, including autism spectrum disorder (10.1002/bies.2100046, 10.1002/bies.2000254, and 10.1002/bies.2000307). Morris and colleagues showthat these global events are linked tomolecular pathways impacting neuroinflammation, oxidative stress andmitochondrial function (10.1002/bies.2000288). What will resonate with every reader are the words of Wolhuter and colleagues, “[will this] convince us to change ourways?” In amanner, the answer to that is exemplified by the work of Ainsworth et al. who provide a path to rescue the coral reef, another victimof the climate crisis, throughgreater knowledge-sharing (10.1002/bies.2100048). The environment is not all that is contained around us but also that what is within us. An oft ignored reality is that for the microbiome, we humans are their environment. Adler and colleagues use a novel tool, also employed by two other authors, to argue that environmental influences are active as early as fetal development to impact microbial trajectories in childhood ultimately leading to ill health (10.1002/bies.2000314).Keepingwith this theme, Luthra-Guptasarma and Guptasarma make an elegant case for the role of diet-gut microbiome link as a determinant of inflammation in severe COVID-19 (10.1002/bies.2000211). The temporally dynamic nature of our ever-changing environment is another feature that distinguishes it from our genome. But how do we measure what environmental influences occurred in the past? Smith et al., Broberg et al., and Lupo et al., use two novel methods that can help scientists travel back in time and characterize the environmental exposures during our earliest development. Deciduous teeth, which commence development prenatally, and neonatal dry blood spots that are collected at birth and archived the world over, can be analyzed in laboratories with mass spectrometry and other methods to obtain thousands of molecular markers of both the environmental exposures and our biological response to those exposures (10.1002/bies.2100030, 10.1002/bies.2000299, and 10.1002/bies.2000298). Examples of using these tools to study cardiovascular disease, pediatric cancer, and biological rhythms are provided. At the level of organizations, Bölte and colleagues provide an elegant example of how a polarizing debate between a biomedical versus a neurodiversity paradigm in the study of neurodevelopmental disorders, can be resolved by embracing the views of the International Classification of Functioning Disability and Health (10.1002/bies.2000254). Staying at that level, Dahm and colleagues (10.1002/bies.2100107) provide a thought-provoking opinionpiece on how research institutions can foster scientific breakthroughs. They argue for a persistently dynamic innovative researcher and these words from their article resonated strongly with me—“we always have the opportunity to re-create ourselves, what we do and how we do it”.