Factors that affect health are often described as either “proximal” (downstream or directly affecting health) or “distal” (upstream or indirectly affecting health). For example, income is thought of as distal (upstream) because it doesn’t directly affect health. However, just as upstream water flows downstream, income is thought to influence proximal factors like where one works and lives, which directly affect health. According to Nancy Krieger, this is not the right way to think about drivers of health.

In the American Journal of Public Health, Krieger wrote,

To take but one example, consider the political economy and ecology of tobacco products and their embodied health consequences. A cigarette (or Freud’s infamous cigar []) is simultaneously:

1. A combustible mass of tobacco leaves and additives whose burning smoke transports psychoactive and addictive chemicals (e.g., nicotine) and carcinogens deep down the respiratory tract to the innermost parts of the lung and its alveolar capillaries, thereby increasing risk of cancer, cardiovascular and pulmonary disease, and other smoking-related ailments, and

2. A highly profitable product whose production, distribution, advertisement, and consumption involves relentless corporate marketing (including manipulation of ideologies involving freedom, class, gender, sexuality, and race/ethnicity and targeting of marginalized groups), government regulation and taxation, tobacco farmers and workers, land ownership, trade agreements, and international treaties. []

Respecting this kind of simultaneity forces one to grapple directly with the competing interests in tobacco regulation (or anything). If, however, one simply searches further and further upstream for solutions to downstream problems, one may fail to account for the fact that there are both winners and losers to policy interventions.

Consequently, as recognized by several new sophisticated multilevel initiatives (e.g., Sweden’s 2003 new public health policy,[] the American Legacy Foundation’s Truth Campaign,[] and the Corporations and Health Watch project []), effective action to curb tobacco use and social disparities in tobacco-related diseases requires integrated, multi-faceted, multilevel campaigns that are relentlessly honest about who gains and who loses from the status quo. The same could be said for any other public health concerns deemed “proximal” or “downstream,” whether about environmental and occupational hazards,[,,,] access to safe water,[,] access to affordable nutritious food,[,] or violence,[]—just as could be said for efforts focused on such ostensibly “distal” or “upstream” social determinants as economic poverty.[]

Another problem with the proximal/distal paradigm is that it suggests that the only relationships are causal ones that run from the distal to proximal factors. That may be true for some of them to some extent, but it isn’t necessarily true to the full extent for all of them. For example, income and where one lives/works both influence health. They also both influence each other — causality may run both ways, upstream and down, which breaks the river metaphor.

Unlike distal and proximal events separated by space or time, levels coexist simultaneously, not sequentially, and exert influence accordingly. The proximal–distal divide, however, inherently cleaves levels rather than connects them, thereby obscuring the intermingling of ecosystems, economics, politics, history, and specific exposures and processes at every level, macro to micro, from societal to inside the body. As William Blake (1757–1827) famously put it, the challenge instead is “to see a world in a grain of sand” []—because it is there.