Nature and human well-being: The olfactory pathway

Abstract

The world is undergoing massive atmospheric and ecological change, driving unprecedented challenges to human well-being. Olfaction is a key sensory system through which these impacts occur. The sense of smell influences quality of and satisfaction with life, emotion, emotion regulation, cognitive function, social interactions, dietary choices, stress, and depressive symptoms. Exposures via the olfactory pathway can also lead to (anti-)inflammatory outcomes. Increased understanding is needed regarding the ways in which odorants generated by nature (i.e., natural olfactory environments) affect human well-being. With perspectives from a range of health, social, and natural sciences, we provide an overview of this unique sensory system, four consensus statements regarding olfaction and the environment, and a conceptual framework that integrates the olfactory pathway into an understanding of the effects of natural environments on human well-being. We then discuss how this framework can contribute to better accounting of the impacts of policy and land-use decision-making on natural olfactory environments and, in turn, on planetary health.

Fig. 1.. Conceptual framework of the pathway from exposure to natural olfactory environments to human well-being.

The olfactory environment is characterized by the concentrations and ratios of airborne chemicals. Dimensions of olfactory function (i.e., sensitivity, discrimination, and identification) are influenced by a variety of individual and environmental factors, which together moderate olfactory perception. Subjective experience is a mediator through which olfactory perceptions lead to well-being outcomes. Relevant determinants of this experience include individual preference, culture, association, prior experience, and multisensory context. Other pathways to well-being include those that occur below the threshold of perception (i.e., subthreshold) and those that occur via initial affective responses that are suprathreshold but independent of top-down processes related to subjective experience. These components lead to a variety of well-being outcomes, from broader dimensions such as quality of and satisfaction with life, to emotional responses and emotion regulation, cognitive function, influences on behavior (social interactions and dietary choices), stress, depressive symptoms, (anti-)inflammatory processes, and effects from exposures to pathogens. Together, these outcomes are the result of subthreshold biochemical processes, initial affective responses, and subjective appraisals of odors from nature. A variety of other pathways mediate the relationship between olfactory environments and human well-being, although they are not illustrated here. Photos credit: University of Washington.