Conifer-Derived Monoterpenes and Forest Walking

Evolution and the critical role of the microbiota in the reduced mental and physical health associated with low socioeconomic status (SES)

The evolution of the gut-microbiota-brain axis in animals reveals that microbial inputs influence metabolism, the regulation of inflammation and the development of organs, including the brain. Inflammatory, neurodegenerative and psychiatric disorders are more prevalent in people of low socioeconomic status (SES). Many aspects of low SES reduce exposure to the microbial inputs on which we are in a state of evolved dependence, whereas the lifestyle of wealthy citizens maintains these exposures. This partially explains the health deficit of low SES, so focussing on our evolutionary history and on environmental and lifestyle factors that distort microbial exposures might help to mitigate that deficit. But the human microbiota is complex and we have poor understanding of its functions at the microbial and mechanistic levels, and in the brain. Perhaps its composition is more flexible than the microbiota of animals that have restricted habitats and less diverse diets? These uncertainties are discussed in relation to the encouraging but frustrating results of attempts to treat psychiatric disorders by modulating the microbiota.

Aphid Cerosipha forbesi control using Piper macedoi Yunck essential oil in strawberry crop

Strawberry is a food rich in bioactive compounds with great antioxidant potential. However, due to the high incidence of pests that affect crop cultivation, phytosanitary management still lacks control methods for agroecological cultivation. Thus, the present research aimed to evaluate the chemical composition and the potential of the essential oil of the leaves of Piper macedoi in the control of Cerosipha forbesi in laboratory and semi-field conditions. The concentration of essential oil in the leaves of P. macedoi that showed the highest mortality was 2.0 ml/L of oil, with a mortality above 91% under laboratory conditions. A mortality rate of 80% for all concentrations tested was observed after 24 h in all conditions tested. Thus, using essential oil from the leaf of P. macedoi can be a highly viable strategy in managing the aphid C. forbesi since it showed high mortality rates with small doses of oil.

Soil processes modify the composition of volatile organic compounds (VOCs) from CO2- and CH4-dominated geogenic and landfill gases: A comprehensive study

Degradation mechanisms affecting non-methane volatile organic compounds (VOCs) during gas uprising from different hypogenic sources to the surface were investigated through extensive sampling surveys in areas encompassing a high enthalpy hydrothermal system associated with active volcanism, a CH4-rich sedimentary basin and a municipal waste landfill. For a comprehensive framework, published data from medium-to-high enthalpy hydrothermal systems were also included. The investigated systems were characterised by peculiar VOC suites that reflected the conditions of the genetic environments in which temperature, contents of organic matter, and gas fugacity had a major role. Differences in VOC patterns between source (gas vents and landfill gas) and soil gases indicated VOC transformations in soil. Processes acting in soil preferentially degraded high-molecular weight alkanes with respect to the low-molecular weight ones. Alkenes and cyclics roughly behaved like alkanes. Thiophenes were degraded to a larger extent with respect to alkylated benzenes, which were more reactive than benzene. Furan appeared less degraded than its alkylated homologues. Dimethylsulfoxide was generally favoured with respect to dimethylsulfide. Limonene and camphene were relatively unstable under aerobic conditions, while α-pinene was recalcitrant. O-bearing organic compounds (i.e., aldehydes, esters, ketones, alcohols, organic acids and phenol) acted as intermediate products of the ongoing VOC degradations in soil. No evidence for the degradation of halogenated compounds and benzothiazole was observed. This study pointed out how soil degradation processes reduce hypogenic VOC emissions and the important role played by physicochemical and biological parameters on the effective VOC attenuation capacity of the soil.

Evaluation of urinary limonene metabolites as biomarkers of exposure to greenness

Exposure to plants is known to improve physical and mental health and living in areas of high vegetation is associated with better health. The addition of quantitative measures of greenness exposure at individual-level to other objective and subjective study measures will help establish cause-and-effect relationships between greenspaces and human health. Because limonene is one of the most abundant biogenic volatile organic compounds emitted by plants, we hypothesized that urinary metabolites of inhaled limonene can serve as biomarkers of exposure to greenness. To test our hypothesis, we analyzed urine samples collected from eight human volunteers after limonene inhalation or after greenness exposure using liquid chromatography-high resolution mass spectrometry-based profiling. Eighteen isomers of nine metabolites were detected in urine after limonene inhalation, and their kinetic parameters were estimated using nonlinear mixed effect models. Urinary levels of most abundant limonene metabolites were elevated after brief exposure to a forested area, and the ratio of urinary limonene metabolites provided evidence of recent exposure. The identities and structures of these metabolites were validated using stable isotope tracing and tandem mass spectral comparison. Together, these data suggest that urinary metabolites of limonene, especially uroterpenol glucuronide and dihydroperillic acid glucuronide, could be used as individualized biomarkers of greenness exposure.

Association of exposures to serum terpenes with the prevalence of dyslipidemia: a population-based analysis

This study sought to examine hitherto unresearched relationships between serum terpenes and the prevalence of dyslipidemia. Serum terpenes such as limonene, α-pinene, and β-pinene from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) were used as independent variables in this cross-sectional study. Continuous lipid variables included total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), residual cholesterol (RC), and apolipoprotein B (Apo B). Binary lipid variables (elevated TC, ≥5.18 mmol/L; lowered HDL-C, <1.04 mmol/L in men, and <1.30 mmol/L in women; elevated non-HDL-C, ≥4.2 mmol/L; elevated TG, ≥1.7 mmol/L; elevated LDL-C, ≥3.37 mmol/L; elevated RC, ≥1.0 mmol/L; and elevated Apo B, ≥1.3 g/L) suggest dyslipidemia. The relationships between the mixture of serum terpenes with lipid variables were investigated using weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR). The study for TC, HDL-C, and non-HDL-C included a total of 1,528 people, whereas the analysis for TG, LDL-C, RC, and Apo B comprised 714 participants. The mean age of the overall participants was 47.69 years, and 48.77% were male. We found that tertiles of serum terpene were positively associated with binary (elevated TC, non-HDL-C, TG, LDL-C, RC, Apo B, and lowered HDL-C) and continuous (TC, non-HDL-C, TG, LDL-C, RC, and Apo B, but not HDL-C) serum lipid variables. WQS regression and BKMR analysis revealed that the mixture of serum terpenes was linked with the prevalence of dyslipidemia. According to our data, the prevalence of dyslipidemia was correlated with serum concentrations of three terpenes both separately and collectively.

Dynamic environmental interactions shaped by vegetative plant volatiles

Covering: up to November 2022Plants shape terrestrial ecosystems through physical and chemical interactions. Plant-derived volatile organic compounds in particular influence the behavior and performance of other organisms. In this review, we discuss how vegetative plant volatiles derived from leaves, stems and roots are produced and released into the environment, how their production and release is modified by abiotic and biotic factors, and how they influence other organisms. Vegetative plant volatiles are derived from different biosynthesis and degradation pathways and are released via distinct routes. Both biosynthesis and release are regulated by other organisms as well as abiotic factors. In turn, vegetative plant volatiles modify the physiology and the behavior of a wide range of organisms, from microbes to mammals. Several concepts and frameworks can help to explain and predict the evolution and ecology of vegetative plant volatile emission patterns of specific pathways: multifunctionality of specialized metabolites, chemical communication displays and the information arms race, and volatile physiochemistry. We discuss how these frameworks can be leveraged to understand the evolution and expression patterns of vegetative plant volatiles. The multifaceted roles of vegetative plant volatiles provide fertile grounds to understand ecosystem dynamics and harness their power for sustainable agriculture.

Effects of Plant-Emitted Monoterpenes on Anxiety Symptoms: A Propensity-Matched Observational Cohort Study

Immersive experiences in green areas, particularly in forests, have long been known to produce beneficial effects for human health. However, the exact determinants and mechanisms leading to healthy outcomes remain to be elucidated. The purpose of this observational cohort study was to investigate whether inhaling plant-emitted biogenic volatile compounds, namely monoterpenes (MTs), can produce specific effects on anxiety symptoms. Data from 505 subjects participating in 39 structured forest therapy sessions at different Italian sites were collected. The air concentration of monoterpenes was measured at each site. STAI state questionnaires were administered before and after the sessions as a measure of anxiety. A propensity score matching analysis was then performed, considering an above-average exposure to inhalable air MTs as the treatment. The estimated effect was -1.28 STAI-S points (95% C.I. -2.51 to -0.06, p = 0.04), indicating that the average effect of exposure to high MT air concentrations during forest therapy sessions was to decrease anxiety symptoms.

The Association between Physical Environment and Externalising Problems in Typically Developing and Neurodiverse Children and Young People: A Narrative Review

The physical environment is of critical importance to child development. Understanding how exposure to physical environmental domains such as greenspace, urbanicity, air pollution or noise affects aggressive behaviours in typical and neurodiverse children is of particular importance given the significant long-term impact of those problems. In this narrative review, we investigated the evidence for domains of the physical environment that may ameliorate or contribute to the display of aggressive behaviours. We have considered a broad range of study designs that include typically developing and neurodiverse children and young people aged 0-18 years. We used the GRADE system to appraise the evidence. Searches were performed in eight databases in July 2020 and updated in June 2022. Additional articles were further identified by hand-searching reference lists of included papers. The protocol for the review was preregistered with PROSPERO. Results: We retrieved 7174 studies of which 67 are included in this review. The studies reported on green space, environmental noise and music, air pollution, meteorological effects, spatial density, urban or rural setting, and interior home elements (e.g., damp/sensory aspects/colour). They all used well validated parent and child reported measures of aggressive behaviour. Most of the studies were rated as having low or unclear risk of bias. As expected, noise, air pollution, urbanicity, spatial density, colour and humidity appeared to increase the display of aggressive behaviours. There was a dearth of studies on the role of the physical environment in neurodiverse children. The studies were heterogeneous and measured a range of aggressive behaviours from symptoms to full syndromes. Greenspace exposure was the most common domain studied but certainty of evidence for the association between environmental exposures and aggression problems in the child or young person was low across all domains. We found a large knowledge gap in the literature concerning neurodiverse children, which suggests that future studies should focus on these children, who are also more likely to experience adverse early life experiences including living in more deprived environments as well as being highly vulnerable to the onset of mental ill health. Such research should also aim to dis-aggregate the underlying aetiological mechanisms for environmental influences on aggression, the results of which may point to pathways for public health interventions and policy development to address inequities that can be relevant to ill health in neurodiverse young people.

Chemical Composition of Atmospheric Air in Nemoral Scots Pine Forests and Submountainous Beech Forests: The Potential Region for the Introduction of Forest Therapy

Studies show that forests are one of the main recreational destinations. This can be explained by their beneficial effects on the health of their visitors, which can be attributed to compounds from the terpene group. The aim of this research was to determine the chemical composition of air in the interiors of Nemoral Scots pine forests and submountainous beech forests, with the determination of compounds of the terpene group. Samples of organic compounds present in the air were collected with the use of Tenax TA sorbent tubes. The process of separation, identification, and determination of the extracted organic compounds was carried out with the use of the gas chromatography technique integrated with a flame ionization detector. Additional identification of the extracted compounds was carried out with the use of GC coupled with mass spectrometry. The most abundant group of compounds was the aliphatic hydrocarbons, both saturated (linear and branched) and unsaturated (terpenes). Carbonyl compounds were also found in the collected samples, but they constituted no more than 10% of all compounds present on the chromatograms. The concentrations of terpenes and terpenoids in the forest atmosphere varied from 10 to 74 µg·m^-3, representing on average 33% of the total volatile organic compounds.

Health Risk Implications of Volatile Organic Compounds in Wildfire Smoke During the 2019 FIREX-AQ Campaign and Beyond

Fire Influence on Regional to Global Environments and Air Quality was a NOAA/NASA collaborative campaign conducted during the summer of 2019. The objectives included identifying and quantifying wildfire composition, smoke evolution, and climate and health impacts of wildfires and agricultural fires in the United States. Ground based mobile sampling via sorbent tubes occurred at the Nethker and Williams Flats fires (2019) and Chief Timothy and Whitetail Loop fires (2020) in Idaho and Washington. Air samples were analyzed through thermal desorption-gas chromatography-mass spectrometry for a variety of volatile organic compounds to elucidate both composition and health impacts. Benzene, toluene, ethylbenzene, xylenes, butenes, phenol, isoprene and pinenes were observed in the wildfire smoke, with benzene ranging from 0.04 to 25 ppbv. Health risk was assessed for each fire by determining sub-chronic (wildfire event) and projected chronic inhalation risk exposure from benzene, a carcinogen, as well as other non-carcinogenic compounds including toluene, ethylbenzene, xylenes, and hexane. The cancer risk of benzene from sub-chronic exposure was 1 extra cancer per million people and ranged from 1 to 19 extra cancers per million people for the projected chronic scenarios, compared to a background level of 1 extra cancer per million people. The hazard index of non-carcinogenic compounds was less than one for all scenarios and wildfires sampled, which was considered low risk for non-cancer health events.

Antibacterial and Oxidative Stress-Protective Effects of Five Monoterpenes from Softwood

Volatile organic compounds (VOC) affect the quality of indoor air. Terpenes and especially monoterpenes are the main molecules emitted from softwood material (coniferous species), which is widely used in construction. The corneal epithelium is one of the first human membranes to encounter VOCs in the air. Moreover, the industrial use of pleasant-scented monoterpenes in cosmetics, food, and detergents exposes people to monoterpenes in their daily lives. In the present study, the health effective properties of five monoterpenes from softwood were tested; cytotoxicity and oxidative stress-protective effects of α- and β-pinenes, R- and S-limonene, and 3-carene were tested in a human corneal epithelial (HCE) cell model system and with two additional in vitro antioxidant tests: oxygen radical absorbance capacity (ORAC) and hydrogen peroxide (H₂O₂) scavenging. Antibacterial efficacies were tested with two bioluminescent bacterial biosensor strains (Escherichia coli K12+pcGLS11 and Staphylococcus aureus RN4220+pAT19) and with minimum inhibitory concentration (MIC) test against Escherichia coli. Only very high concentrations of monoterpenes (0.3–0.5 mg/mL) demonstrated cytotoxicity against HCE cells. Contrary to the original hypothesis, monoterpenes did not exhibit strong antioxidant properties in tested concentrations. However, biosensors and MIC tests indicated clear antibacterial activities for all tested monoterpenes.

The Relationship between the Restorative Perception of the Environment and the Physiological and Psychological Effects of Different Types of Forests on University Students

Short-term exposure to a forest environment is beneficial to human physiological and psychological health. However, there is little known about the relationship between the restorative perception of environment and physiological and psychological restoration achieved by experiencing the forest environment. This study evaluated the relationship between the restorative perception of different types of forests and human physiological and psychological effects. A sample of 30 young adult students from Beijing Forestry University was exposed to coniferous, deciduous, and mixed forests as well as an urban site. Restorative perception of the environment was measured using the PRS questionnaire. Restorative effects were measured using physiological indicators (blood pressure and heart rate) and three psychological questionnaires (Restorative Outcome Scale; Subjective Vitality Scale; Warwick-Edinburgh Mental Well-being Scale). The results demonstrated the following: (1) There were significant differences in the perceived restorative power of the three types of forests, with the highest level in the mixed forest, followed by the coniferous forest and the deciduous forest. (2) All types of forests were beneficial to physiological and psychological restoration. The mixed forest had the greatest effect in lowering blood pressure and heart rate as well as increasing vitality, while the coniferous forest had the strongest increases in psychological restoration and positive mental health. (3) The level of perceived restorative power of environment was positively related to the physiological and psychological restoration. These findings provide practical evidence for forest therapy that can maximize the restorative potential of forests.

Short-Term Effects of Forest Therapy on Mood States: A Pilot Study

Immersion in forest environments was shown to produce beneficial effects to human health, in particular psychophysical relaxation, leading to its growing recognition as a form of integrative medicine. However, limited evidence exists about the statistical significance of the effects and their association with external and environmental variables and personal characteristics. This experimental study aimed to substantiate the very concept of forest therapy by means of the analysis of the significance of its effects on the mood states of anxiety, depression, anger and confusion. Seven forest therapy sessions were performed in remote areas and a control one in an urban park, with participants allowed to attend only one session, resulting in 162 psychological self-assessment questionnaires administered before and after each session. Meteorological comfort, the concentration of volatile organic compounds in the forest atmosphere and environmental coherence were identified as likely important external and environmental variables. Under certain conditions, forest therapy sessions performed in remote sites were shown to outperform the control session, at least for anxiety, anger and confusion. A quantitative analysis of the association of the outcomes with personal sociodemographic characteristics revealed that only sporting habits and age were significantly associated with the outcomes for certain psychological domains.

Human absorption of monoterpenes after a 2-h forest exposure: A field experiment in a Mediterranean holm oak forest

The current body of literature points monoterpenes as one of the determinant factors of the interaction between forests and human health. The present study aims at analyzing the monoterpene absorption by humans during a 2 -hs forest exposure in a Mediterranean holm oak forest focusing on the four most abundant monoterpene compounds: alpha-pinene, beta-pinene, alpha-phellandrene and limonene. Participants' blood samples were collected before and after exposure to forest or urban environment (control). We conducted air and blood sampling using cartridges and head space method and determined the monoterpene compounds through CGMS. We identified the four compounds in forest air during the experimental study being alpha-pinene the monoterpene with the greatest concentration. Results show no significant changes in monoterpene blood concentrations for the forest and control group. However, a negative significant relationship between absorption and baseline blood concentration of the most abundant forest air monoterpenes, alpha-pinene and beta-pinene, was found in individuals visiting the forest, i.e. higher absorption was found the lower the baseline blood concentration was. Although no significant lineal correlation could be spotted between the vital variables and the monoterpene absorption, we found significant correlations between the absorption of the monoterpene compounds. This attempt, first in a Mediterranean holm oak forest, can serve as a starting point and constitute a valuable contribution for further research in regard to experimental design and laboratory analysis.

Development and Validation of an Analytical Method for Quantitation of Alpha-pinene in Rodent Blood and Mammary Gland by Headspace GC-MS

Alpha-pinene (AP), produced by pine trees and other plants, is the main component of turpentine and is used as a fragrance and flavor ingredient. Exposure occurs via use of personal care and household cleaning products and in the lumber industry. Despite widespread exposure, toxicity data for AP are limited. The objective of this work was to develop and validate a method to quantitate AP in rodent blood and mammary glands, in support of toxicokinetic and toxicology studies of AP. The method uses 100 µL of blood or ~100 mg of mammary gland with analysis by headspace gas chromatography-mass spectrometry. The samples are diluted with internal standard (2H3-AP, IS) and sealed in headspace vials; mammary glands are homogenized within the vial. The vials are equilibrated briefly at 60°C before a headspace sample is analyzed. The method was validated in Sprague Dawley rat blood over the range 5-500 ng/mL and mammary gland over the range 100-5000 ng/g. The method was linear (r ≥0.99), accurate (mean relative error (RE) ≤±13.4%) and precise (relative standard deviation (RSD) ≤7.1%) in both matrices. Recoveries incorporating IS were ≥88.7% at all concentrations in both tissues. Standards as high as 1500 ng/mL in blood and 20,000 ng/g in mammary gland could be analyzed using lower injection volume or extrapolating the calibration curve beyond the upper limit of quantitation (mean %RE ≤±18.7; %RSD ≤2.2). Loss of AP occurred during overnight autosampler storage as well as frozen storage in as few as 15 days, but incorporation of IS prior to storage corrected for the loss such that calculated concentrations were within 84.7-117% of day 0 concentrations following frozen storage up to ≥32 days in both matrices. Matrix evaluation was performed in Hsd:Sprague Dawley®SD® rat and B6C3F1 mouse blood and mammary glands (mean %RE ≤±9.2; %RSD ≤4.3). These data demonstrate that the method is suitable for determination of AP in rodent blood and mammary glands.

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

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.

Effects of a Forest Walk on Urinary Dityrosine and Hexanoyl-Lysine in Young People: A Pilot Study

A few studies indicate exposure to forests may alleviate oxidative stress in the body. However, more evidence is needed to support this potentiality. The purpose of the current study aimed at examining whether there is any difference in urinary levels of oxidatively modified proteins or lipids-dityrosine (DT) and hexanoyl-lysine (HEL), respectively, after a forest or urban walk. The study was performed on 29 university students who took part in forest walks (Shinjo Village) in Okayama Prefecture of Japan and on 42 university students who took part in urban walks in the downtown area of Okayama City. Urine samples before and after the walks were analyzed for DT and HEL excretion. Air phytoncides during the walks were also measured. We found a decreased tendency in urinary DT and HEL (p < 0.05) in most participants after the forest walks, but not after the urban walks. We further found the total levels of air phytoncides in the forest field were 1.50 times higher compared with those in the urban field. This study suggests the possibility that regular immersion in a forest environment might contribute toward weakening of the oxidative modifications of proteins or lipids in the body.

Human Breathable Air in a Mediterranean Forest: Characterization of Monoterpene Concentrations under the Canopy

Monoterpenes have been identified as potential determinants of the human health effects induced by forest exposure. The present study characterizes the total monoterpene concentrations at nose height in a Mediterranean Holm oak forest located in North-East Iberian Peninsula during the annual emission peak (summer and autumn: June to November) using a Proton Transfer Reaction-Mass Spectrometry (PTR-MS). Results show a strong variability of the total monoterpene concentrations in season and daytime. The concentration peak appears during July and August. These two months displayed two average maxima in their diel cycles: One during early morning (from 6:00 to 8:00, 0.30 ppbv for July and 0.41 ppbv for August) and another one at early afternoon (from 13:00 to 15:00, 0.27 ppbv during July and 0.32 ppbv during August). Monoterpene concentrations were strongly related with the temperature (exponentially) and solar radiation (rectangular hyperbolic relationship). The concentrations registered here are similar or higher than in previous ex situ studies showcasing the effects of forests on human health. These findings provide relevant data for the scientific and healthcare community by improving the understanding of monoterpene dynamics at nose height and suggesting further research on the effects of forests on human health, particularly in the Mediterranean region.

Measures to Promote Rural Healthcare Tourism with a Scientific Evidence-Based Approach

The present study aimed to evaluate the effects of physical activities on human health in forests in countryside and rural areas. The test experiment was conducted in a countryside forest, whereas the controlled experiment was conducted in an urban area where the study participants resided. A total of 22 participants (aged 20.9 ± 1.3 years) were evaluated in this study. Heart rate variability and salivary cortisol level were used as indices of physiological conditions, and semantic differential method, profile of mood states (POMS), and state-trait anxiety inventory (STAI) were used to evaluate the participants' emotional states. The participants were asked to walk around forest and urban areas for 15 min. The results were as follows. As compared to the urban area, in the forest area, (1) the power of the high-frequency (HF) component of the heart rate variability (HRV) was significantly higher; (2) low-frequency (LF)/(LF + HF) was significantly lower; (3) salivary cortisol level was significantly lower; (4) the participants felt more comfortable, natural, relaxed, and less anxious and showed higher levels of positive emotions and lower levels of negative emotions. Consequently, walking in the forest area induces relaxing short-term physiological and psychological effects on young people living in urban areas.

How Should Forests Be Characterized in Regard to Human Health? Evidence from Existing Literature

The potential of forests as a source of health has been addressed by the scientific community and is now being considered in national forest strategies, management plans and policies. Studies identifying the mechanisms by which forest characteristics may induce these effects on human health are nevertheless scarce. This systematic review of literature on forests and human health with real-life human exposure was conducted to assess the extent to which forests have been studied and described in detail and the extent to which relationships between forest variables and health effects have been reported. The analysis underlines the lack of forest descriptions in 19.35% of the 62 studies selected for review as well as the high heterogeneity of forest variables’ description. Patterns among the articles could not be identified correlating the broader forest variable (forest type) and the most studied health variables identified (blood pressure, pulse rate or/and cortisol levels). These findings, together with previous ex situ researches, suggest the need to ameliorate and incorporate more accurate descriptions of forest variables within human health studies to provide data for forest management and the potential use of these habitats for preventive medicine and clinical practice guidelines.

Temporal and Spatial Variability of Volatile Organic Compounds in the Forest Atmosphere

The healing effects of the forest are increasingly being valued for their contribution to human psychological and physiological health, motivating further advances aimed at improving knowledge of relevant forest resources. Biogenic volatile organic compounds, emitted by the plants and accumulating in the forest atmosphere, are essential contributors to the healing effects of the forest, and represent the focus of this study. Using a photoionization detector, we investigated the high frequency variability, in time and space, of the concentration of total volatile organic compounds on a hilly site as well as along forest paths and long hiking trails in the Italian northern Apennines. The scale of concentration variability was found to be comparable to absolute concentration levels within time scales of less than one hour and spatial scales of several hundred meters. During daylight hours, on clear and calm days, the concentration peaked from noon to early afternoon, followed by early morning, with the lowest levels in the late afternoon. These results were related to meteorological variables including the atmospheric vertical stability profile. Moreover, preliminary evidence pointed to higher concentrations of volatile organic compounds in forests dominated by conifer trees in comparison to pure beech forests.

Effects by inhalation of abundant fragrances in indoor air - An overview

Odorous compounds (odors) like fragrances may cause adverse health effects. To assess their importance by inhalation, we have reviewed how the four major abundant and common airborne fragrances (α-pinene (APN), limonene (LIM), linalool (LIL), and eugenol (EUG)) impact the perceived indoor air quality as odor annoyance, sensory irritation and sensitization in the airways. Breathing and cardiovascular effects, and work performance, and the impact in the airways of ozone-initiated gas- and particle phase reactions products have also been assessed. Measured maximum indoor concentrations for APN, LIM and LIL are close to or above their odor thresholds, but far below their thresholds for sensory irritation in the eyes and upper airways; no information could be traced for EUG. Likewise, reported risk values for long-term effects are far above reported indoor concentrations. Human exposure studies with mixtures of APN and LIM and supported by animal inhalation models do not support sensitization of the airways at indoor levels by inhalation that include other selected fragrances. Human exposure studies, in general, indicate that reported lung function effects are likely due to the perception rather than toxic effects of the fragrances. In general, effects on the breathing rate and mood by exposure to the fragrances are inconclusive. The fragrances may increase the high-frequency heart rate variability, but aerosol exposure during cleaning activities may result in a reduction. Distractive effects influencing the work performance by fragrance/odor exposure are consistently reported, but their persistence over time is unknown. Mice inhalation studies indicate that LIM or its reaction mixture may possess anti-inflammatory properties. There is insufficient information that ozone-initiated reactions with APN or LIM at typical indoor levels cause airway effects in humans. Limited experimental information is available on long-term effects of ozone-initiated reaction products of APN and LIM at typical indoor levels.