Forest Volatile Organic Compounds and Their Effects on Human Health: A State-of-the-Art Review

Abstract

The aim of this research work is to analyze the chemistry and diversity of forest VOCs (volatile organic compounds) and to outline their evidence-based effects on health. This research work was designed as a narrative overview of the scientific literature. Inhaling forest VOCs like limonene and pinene can result in useful antioxidant and anti-inflammatory effects on the airways, and the pharmacological activity of some terpenes absorbed through inhalation may be also beneficial to promote brain functions by decreasing mental fatigue, inducing relaxation, and improving cognitive performance and mood. The tree composition can markedly influence the concentration of specific VOCs in the forest air, which also exhibits cyclic diurnal variations. Moreover, beneficial psychological and physiological effects of visiting a forest cannot be solely attributed to VOC inhalation but are due to a global and integrated stimulation of the five senses, induced by all specific characteristics of the natural environment, with the visual component probably playing a fundamental role in the overall effect. Globally, these findings can have useful implications for individual wellbeing, public health, and landscape design. Further clinical and environmental studies are advised, since the majority of the existing evidence is derived from laboratory findings.

Keywords: biogenic volatile organic compounds; forest; limonene; phytoncides; pinene; preventive medicine; public health; review.

Figure 1

BVOCs’ functions in relation to biotic and abiotic stresses. Adapted from Laothawornkitkul et al. (2009) [8].

Figure 2

Main biosynthetic pathways for BVOCs. In green and yellow colors, the methylerythritol phosphate (MEP) and mevalonate (MVA) pathways to isoprenoids, respectively, in blue color, the lipoxygenase (LOX) pathway to GLVs, and in purple color, the shikimate pathway to aromatic compounds. Adapted from Maffei et al. (2011) [17].

Figure 3

Atmospheric concentration of BVOCs under forest canopy [16,31,32,34,38,39,40,41,42,43,44]. Abbreviations: Tot. terpenes = total concentration of terpenes; LOX = products of the lipoxygenase (LOX) pathway.

Figure 4

Atmospheric concentrations of seven monoterpenes under the canopy of a Scots pine forest [44].