Defining the Human Envirome: An Omics Approach for Assessing the Environmental Risk of Cardiovascular Disease

Abstract

Both genetic and environmental factors contribute to the development of cardiovascular disease, but in comparison with genetics, environmental factors have received less attention. Evaluation of environmental determinants of cardiovascular disease is limited by the lack of comprehensive omics approaches for integrating multiple environmental exposures. Hence, to understand the effects of the environment as a whole (envirome), it is important to delineate specific domains of the environment and to assess how, individually and collectively; these domains affect cardiovascular health. In this review, we present a hierarchical model of the envirome; defined by 3 consecutively nested domains, consisting of natural, social, and personal environments. Extensive evidence suggests that features of the natural environment such as sunlight, altitude, diurnal rhythms, vegetation, and biodiversity affect cardiovascular health. However, the effects of the natural environment are moderated by the social environment comprised of built environments, agricultural and industrial activities, pollutants and contaminants, as well as culture, economic activities, and social networks that affect health by influencing access to healthcare, social cohesion, and socioeconomic status. From resources available within society, individuals create personal environments, characterized by private income, wealth and education, and populated by behavioral and lifestyle choices relating to nutrition, physical activity, sleep, the use of recreational drugs, and smoking. An understanding of the interactions between different domains of the envirome and their integrated effects on cardiovascular health could lead to the development of new prevention strategies and deeper insights into etiologic processes that contribute to cardiovascular disease risk and susceptibility.

Keywords: air pollution; coronary artery disease; diet; exercise; smoking prevention.

Figure 1. Model of the human envirome

The entirety of the human environment could differentiated into natural, social and personal domains. Each domain is nested within another. The natural environment is the most primeval. The social environment is nested within the natural environment, as it is derived from and developed within nature. Personal environments are constructed from elements from the social and natural environments by individual choices or happenstance. While each domain is categorically distinct, yet their boundaries are porous. The natural environment permeates through both social and personal domains, and often the construction of social and personal environments affects the natural environment. Each domain individually and collectively affects cardiovascular health, and moderates, modifies, or rectifies the influence of other domains.

Figure 2. The natural environment

The natural environment is comprised of a geosphere and a biosphere. The geosphere is a composite of the lithosphere, hydrosphere, and atmosphere. It is characterized by its location, climate, and geography. The biosphere includes living plants, animals, and microbes. Features of geosphere, such as altitude, sunlight, diurnal and seasonal cycles of the earth influence cardiovascular function and are important determinants of cardiovascular health. Similarly, surrounding biodiversity and exposure to plants, animals and microbes could result in disease as well as immune adaptation. Elements of both the geosphere and biosphere could be sources of pollution.

Figure 3. The social environment

Interactions of humans with nature and with each other results in the construction of social environments. Interactions with nature, such as agriculture or mining result in the development of technology, and lead to economic development, sustained by interactions between members of a society, which create elaborate social networks. Such networks are characterized by their distinct culture, history, governance, and organization. Interactions of humans with nature and with other members of a society create knowledge and technology, which lead to the development of built environments. The built environment, in turn, supports increasing complex social networks and ensures preservation and transmission of knowledge and technology. Together, social networks and built environments are important determinants of cardiovascular health. They support health services and health care, and they enable specific behavioral choices. Social environments and the economic and interactive activities they support generate environmental pollutants that affect cardiovascular health.

Figure 4. The personal environment

Personal microenvironments are created by either choice or chance. They are characterized by physical living conditions within a society, as well as smaller social networks comprised of family, coworkers, and immediate acquaintances. Each of these influence cardiovascular health and disease risk, as do personal income, wealth and education. Components of both the natural and the social environments affect the creating and transmission of personal environments and shape lifestyle choices such as physical activity, sleep, nutrition, smoking, and the use of recreational drugs.

Figure 5. The human pollutome

Elements of each domain of the envirome are sources of air, water and soil pollution. In the natural environment, events such as earthquakes, volcanoes and forest fires can be a source of sporadic pollution either by emitting toxic gases and particles in the air and water or uncovering mercury and arsenic in the soil. Activities within the social environment such as agriculture, power generation, traffic and biomass burning generate a variety of gaseous and particulate pollution, as well as noise and light pollution. Exposure to ambient pollutants within social environments could be moderated by characteristics of the personal environment, which in turn can be a source of additional exposure to particles and chemicals derived from cooking, the use of candles, incense, and cleaners. To define pollutant exposure as a whole, it is important not only to quantify pollutants in each environmental domain, but also to account also for change or moderation of exposure from sources in one domain by another. It is also important to identify how characteristics of each domain modify exposure to pollutants in that and other domains.

Scheme 1. Influence of built environment of cardiovascular health and disease risk

Features of the built environment affect CVD risk factors, cardiovascular events and cardiovascular mortality. The diversity of land use within neighborhoods affects physical activity and food choices of residents and their risk of obesity, T2D or stroke. Characteristic of urban environments that affect walkability influence physical activity, and the risk of obesity, hypertension, and T2D. Urban greenspaces have been found to promote physical activity and better mental health and have been linked to a decreased risk of diabetes, cardiovascular and stroke mortality. Features of building used for residential and commercial purposes affect individual mental health and stress, whereas higher levels of public transportation have been linked with lower levels of obesity. Residential proximity to major roadways is associated with increased cardiovascular mortality, risk of myocardial infarction and stroke.