Evaluating the relative importance of VOCs on human wellbeing in urban greenspaces

Characterising the impact of VOC profiles in glasshouses in the Oxford Botanic Gardens 

An increasing number of research studies have demonstrated an apparent link between time spent in nature and positive human health and wellbeing outcomes but it is not always clear which specific aspects of nature are responsible for the physiological and psychological relaxation of our bodies.

On-going work to examine which nature-derived characteristics promote positive wellbeing outcomes tends to concentrate on understanding the implications on four of the main senses: sight, touch, sound, and - the focus of this work - smell. 

Many plants have distinctive scents. These arise from the emission of specific biogenic VOCs which play important roles in plant processes such as pollination and seed dispersal, communication, and deterring predators. Humans can detect the release of VOCs, including terpenes which give pine and citrus scents and green leaf volatiles which give fresh aromas, even at low concentrations within complex environments.

Whilst the majority of recent studies on the impact of VOCs have been based in clinical settings indoors or in forested environments, the aim of this pilot study is to investigate the impacts of nature-based olfactory stimuli within urban greenspaces. Using glasshouses in the Oxford Botanic Gardens and working with 14 participants over 2 months, the objectives are to: 

1. A map of the ambient biogenic VOC profiles in 6 glasshouses at the Oxford Botanic Gardens.
2.  A survey of the vegetation present in these glasshouses to identify the species that may be associated with the characteristic ambient VOC profiles.
3. A quantitative analysis of the percentage of vegetation in each glasshouse.
4. An analysis of salivary a-amylase activity collected from human participants before and after visiting each glasshouse as a proxy for physiological calming.
5. An analysis of participants’ heart rate before and after 30 minutes in a glasshouse.
6. An analysis of the subjective wellbeing tests to assess whether the participants recognise any changes in stress/ anxiety.

The information derived from this pilot study will be important in determining how urban greenspace nature-derived stimuli contribute to the physiological and psychological experience of stress. Early results show that the glasshouses are characterised by distinct VOC profiles, that participants demonstrated a decrease in heart rate and experienced improved psychological wellbeing following their visits to the glasshouse but it was not yet clear if glasshouses with distinct VOC profiles induce beneficial marked changes in physiological proxies of stress.